diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index d1e9682c..9cbd54b4 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -1,7 +1,43 @@
 version: 2
 updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+      - "github-actions"
+    commit-message:
+      prefix: "ci"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+
   - package-ecosystem: "gomod"
     directory: "/api/go"
     schedule:
       interval: "weekly"
     open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
+      - "go"
+
+  - package-ecosystem: "gomod"
+    directory: "/cli/nvpkg"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 10
+    labels:
+      - "dependencies"
+      - "go"
+
+  - package-ecosystem: "pip"
+    directory: "/scripts"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+      - "python"
diff --git a/.github/workflows/check-dev-docs.yml b/.github/workflows/check-dev-docs.yml
index a757061c..e54aa8ee 100644
--- a/.github/workflows/check-dev-docs.yml
+++ b/.github/workflows/check-dev-docs.yml
@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Check for stray files in dev_docs
         run: |
diff --git a/.github/workflows/docs-check.yml b/.github/workflows/docs-check.yml
index f1159792..23b4fe8c 100644
--- a/.github/workflows/docs-check.yml
+++ b/.github/workflows/docs-check.yml
@@ -43,10 +43,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v6
         with:
           node-version: '20'
 
diff --git a/.github/workflows/go-bdd.yml b/.github/workflows/go-bdd.yml
index 93e438b3..02dd1810 100644
--- a/.github/workflows/go-bdd.yml
+++ b/.github/workflows/go-bdd.yml
@@ -9,6 +9,13 @@ on:
       - 'api/go/**/*.go'
       - 'features/**/*.feature'
       - 'api/go/**/_bdd/**/*.go'
+  push:
+    branches:
+      - main
+    paths:
+      - 'api/go/**/*.go'
+      - 'features/**/*.feature'
+      - 'api/go/**/_bdd/**/*.go'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
@@ -23,7 +30,7 @@ jobs:
         working-directory: api/go
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v5
diff --git a/.github/workflows/go-ci.yml b/.github/workflows/go-ci.yml
index 96e99233..be17adaa 100644
--- a/.github/workflows/go-ci.yml
+++ b/.github/workflows/go-ci.yml
@@ -25,7 +25,7 @@ jobs:
         working-directory: api/go
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v5
@@ -47,7 +47,7 @@ jobs:
         working-directory: api/go
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v5
@@ -67,15 +67,15 @@ jobs:
         run: go vet ./...
 
       - name: Run golangci-lint
-        uses: golangci/golangci-lint-action@v7
+        uses: golangci/golangci-lint-action@v9
         with:
-          version: v2.7.0
+          version: latest
           working-directory: api/go
 
       - name: Run golangci-lint (BDD)
-        uses: golangci/golangci-lint-action@v7
+        uses: golangci/golangci-lint-action@v9
         with:
-          version: v2.7.0
+          version: latest
           working-directory: api/go
           args: --build-tags=bdd
 
@@ -87,7 +87,7 @@ jobs:
         working-directory: api/go
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v5
@@ -106,7 +106,7 @@ jobs:
         working-directory: api/go
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Go
         uses: actions/setup-go@v5
diff --git a/.github/workflows/nvpkg-ci.yml b/.github/workflows/nvpkg-ci.yml
new file mode 100644
index 00000000..420ec2c8
--- /dev/null
+++ b/.github/workflows/nvpkg-ci.yml
@@ -0,0 +1,116 @@
+name: nvpkg CI
+
+# NOTE: This workflow must be kept in sync with the 'ci' target in cli/nvpkg/Makefile.
+#       When adding or modifying CI checks, update both this workflow and cli/nvpkg/Makefile.
+#       Runs test, lint, build, and coverage for the nvpkg CLI.
+
+on:
+  push:
+    paths:
+      - 'cli/nvpkg/**'
+      - 'api/go/**'
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test-nvpkg:
+    name: Test nvpkg
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: cli/nvpkg
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache-dependency-path: cli/nvpkg/go.sum
+
+      - name: Verify go.mod is tidy
+        run: go mod tidy && git diff --exit-code go.mod go.sum
+
+      - name: Verify dependencies
+        run: go mod verify
+
+      - name: Run unit tests
+        run: go test -v ./...
+
+  lint-nvpkg:
+    name: Lint nvpkg
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: cli/nvpkg
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache-dependency-path: cli/nvpkg/go.sum
+
+      - name: Check formatting
+        run: |
+          if [ "$(gofmt -s -l . | wc -l)" -gt 0 ]; then
+            echo "Code is not formatted. Run 'go fmt ./...'"
+            gofmt -s -d .
+            exit 1
+          fi
+
+      - name: Run go vet
+        run: go vet ./...
+
+      - name: Run golangci-lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: latest
+          working-directory: cli/nvpkg
+
+  build-nvpkg:
+    name: Build nvpkg
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: cli/nvpkg
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache-dependency-path: cli/nvpkg/go.sum
+
+      - name: Install UPX
+        run: sudo apt-get update && sudo apt-get install -y upx-ucl
+
+      - name: Build
+        run: make build
+
+  coverage-nvpkg:
+    name: Coverage nvpkg
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: cli/nvpkg
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache-dependency-path: cli/nvpkg/go.sum
+
+      - name: Run tests with coverage
+        run: make coverage
diff --git a/.github/workflows/nvpkg-release.yml b/.github/workflows/nvpkg-release.yml
new file mode 100644
index 00000000..2006a175
--- /dev/null
+++ b/.github/workflows/nvpkg-release.yml
@@ -0,0 +1,108 @@
+name: nvpkg Build and Publish
+
+# Builds release (Go -ldflags -s -w + UPX) and dev binaries in separate per-OS/arch jobs (matrix).
+# Output: one folder per target (e.g. linux-amd64/, darwin-arm64/, windows-amd64/, freebsd-amd64/)
+# with nvpkg and nvpkg-dev (Unix) or nvpkg.exe and nvpkg-dev.exe (Windows).
+# Platforms match cli/nvpkg/Makefile: Linux, macOS (darwin), Windows, FreeBSD (amd64, arm64 each where applicable).
+# Uploads artifacts and attaches to GitHub Release.
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  GO_VERSION: '1.25'
+
+jobs:
+  build:
+    name: Build nvpkg ${{ matrix.goos }}-${{ matrix.goarch }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - goos: linux
+            goarch: amd64
+          - goos: linux
+            goarch: arm64
+          - goos: darwin
+            goarch: amd64
+          - goos: darwin
+            goarch: arm64
+          - goos: windows
+            goarch: amd64
+          - goos: freebsd
+            goarch: amd64
+          - goos: freebsd
+            goarch: arm64
+    defaults:
+      run:
+        working-directory: cli/nvpkg
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: ${{ env.GO_VERSION }}
+          cache-dependency-path: cli/nvpkg/go.sum
+
+      - name: Install UPX
+        run: sudo apt-get update && sudo apt-get install -y upx-ucl
+
+      - name: Build release and dev binaries
+        run: |
+          set -e
+          GOOS=${{ matrix.goos }} GOARCH=${{ matrix.goarch }}
+          dir="../dist/${GOOS}-${GOARCH}"
+          mkdir -p "$dir"
+          if [ "$GOOS" = "windows" ]; then
+            release_name="nvpkg.exe"
+            dev_name="nvpkg-dev.exe"
+          else
+            release_name="nvpkg"
+            dev_name="nvpkg-dev"
+          fi
+          CGO_ENABLED=0 GOOS="$GOOS" GOARCH="$GOARCH" go build -ldflags="-s -w" -trimpath -o "$release_name" .
+          upx --best "$release_name" 2>/dev/null || true
+          mv "$release_name" "$dir/"
+          GOOS="$GOOS" GOARCH="$GOARCH" go build -o "$dev_name" .
+          mv "$dev_name" "$dir/"
+          find "$dir" -type f | sort
+
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.goos }}-${{ matrix.goarch }}
+          path: cli/dist/${{ matrix.goos }}-${{ matrix.goarch }}
+          retention-days: 90
+
+  publish:
+    name: Publish to Release
+    runs-on: ubuntu-latest
+    needs: build
+    if: github.event_name == 'release'
+    steps:
+      - name: Download build artifacts
+        uses: actions/download-artifact@v4
+
+      - name: Create archives per platform
+        run: |
+          for dir in */; do
+            (cd "$dir" && zip -r "../${dir%/}.zip" .)
+          done
+
+      - name: Publish to GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ github.ref_name }}
+          files: |
+            *.zip
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/python-lint.yml b/.github/workflows/python-lint.yml
index 13ed190c..c2626d7a 100644
--- a/.github/workflows/python-lint.yml
+++ b/.github/workflows/python-lint.yml
@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v5
diff --git a/.markdownlint-cli2.jsonc b/.markdownlint-cli2.jsonc
index e7475812..b72f7a0e 100644
--- a/.markdownlint-cli2.jsonc
+++ b/.markdownlint-cli2.jsonc
@@ -6,6 +6,7 @@
   "ignores": [
     "**/node_modules/**",
     "tmp/**",
+    "**/dist/**",
     "**/*.plan.md",
     "**/.*/**"
   ],
diff --git a/Makefile b/Makefile
index 281dec75..7734e279 100644
--- a/Makefile
+++ b/Makefile
@@ -11,14 +11,17 @@ ifneq ($(MAKE),$(SYSTEM_MAKE))
   override MAKE := $(SYSTEM_MAKE)
 endif
 
-.PHONY: test test-go test-go-v1 bdd bdd-go bdd-go-v1 bdd-ci test-unified ci ci-go ci-go-v1 venv lint-markdown lint-python validate-links validate-heading-numbering apply-heading-corrections generate-anchor validate-req-references validate-go-defs-index validate-go-code-blocks validate-go-spec-signature-consistency validate-go-signatures validate-go-signatures-go validate-go-signatures-go-v1 validate-go-spec-references apply-go-spec-references audit-feature-coverage audit-requirements-coverage audit-coverage docs-check lint lint-go lint-go-v1 coverage coverage-go coverage-go-v1 coverage-html coverage-html-go coverage-html-go-v1 coverage-report coverage-report-go coverage-report-go-v1
+.PHONY: test test-go test-go-v1 test-nvpkg bdd bdd-go bdd-go-v1 bdd-ci test-unified ci ci-go ci-go-v1 ci-nvpkg venv lint-markdown lint-python lint-nvpkg validate-links validate-heading-numbering apply-heading-corrections generate-anchor validate-req-references validate-go-defs-index validate-go-code-blocks validate-go-spec-signature-consistency validate-go-signatures validate-go-signatures-go validate-go-signatures-go-v1 validate-go-spec-references apply-go-spec-references audit-feature-coverage audit-requirements-coverage audit-coverage docs-check lint lint-go lint-go-v1 coverage coverage-go coverage-go-v1 coverage-nvpkg coverage-html coverage-html-go coverage-html-go-v1 coverage-html-nvpkg coverage-report coverage-report-go coverage-report-go-v1 coverage-report-nvpkg build build-nvpkg build-dev-nvpkg clean clean-go clean-nvpkg
 
 # Test targets - delegate to language implementations
-test: test-go
+test: test-go test-nvpkg
 test-go: test-go-v1
 test-go-v1:
 	$(MAKE) -C api/go test
 
+test-nvpkg:
+	$(MAKE) -C cli/nvpkg test
+
 # BDD test targets - delegate to language implementations
 bdd: bdd-go
 bdd-go: bdd-go-v1
@@ -32,14 +35,17 @@ bdd-ci:
 # NOTE: The 'ci' target must be kept in sync with GitHub Actions workflows.
 #       When adding or modifying CI checks, update both this Makefile and the
 #       corresponding workflow files to ensure local 'make ci' matches CI behavior.
-#       Current workflows: docs-check.yml, python-lint.yml, go-ci.yml
+#       Current workflows: docs-check.yml, python-lint.yml, go-ci.yml, nvpkg-ci.yml.
 # NOTE: Order matters - validate-heading-numbering runs before validate-links because
 #       fixing heading numbering changes anchor IDs, which would break link validation.
-ci: docs-check lint-python ci-go
+ci: docs-check lint-python ci-go ci-nvpkg
 ci-go: ci-go-v1
 ci-go-v1:
 	/usr/bin/make -C api/go ci
 
+ci-nvpkg:
+	$(MAKE) -C cli/nvpkg ci
+
 # Python venv for lint tooling - creates .venv and installs scripts/requirements-lint.txt
 # Run once (or after adding/updating scripts/requirements-lint.txt) so make lint-python uses the venv.
 # Usage: make venv
@@ -451,25 +457,57 @@ test-unified:
 	@echo "Unified test runner not yet implemented"
 	# Future: $(MAKE) -C test-runner run
 
-lint: lint-go lint-markdown lint-python
+lint: lint-go lint-nvpkg lint-markdown lint-python
 lint-go: lint-go-v1
 lint-go-v1:
 	$(MAKE) -C api/go lint
 
+lint-nvpkg:
+	$(MAKE) -C cli/nvpkg lint
+
 # Coverage targets - delegate to language implementations
-coverage: coverage-go
+coverage: coverage-go coverage-nvpkg
 coverage-go: coverage-go-v1
 coverage-go-v1:
 	$(MAKE) -C api/go coverage
 
+coverage-nvpkg:
+	$(MAKE) -C cli/nvpkg coverage
+
 # HTML coverage report targets - delegate to language implementations
-coverage-html: coverage-html-go
+coverage-html: coverage-html-go coverage-html-nvpkg
 coverage-html-go: coverage-html-go-v1
 coverage-html-go-v1:
 	$(MAKE) -C api/go coverage-html
 
+coverage-html-nvpkg:
+	$(MAKE) -C cli/nvpkg coverage-html
+
 # Coverage report targets - delegate to language implementations
-coverage-report: coverage-report-go
+coverage-report: coverage-report-go coverage-report-nvpkg
 coverage-report-go: coverage-report-go-v1
 coverage-report-go-v1:
 	$(MAKE) -C api/go coverage-report
+
+coverage-report-nvpkg:
+	$(MAKE) -C cli/nvpkg coverage-report
+
+# Build nvpkg CLI (minimal-size release binary)
+# Build nvpkg for current OS/arch (delegates to cli/nvpkg).
+build: build-nvpkg
+
+build-nvpkg:
+	$(MAKE) -C cli/nvpkg build
+
+# Build nvpkg development binary (with debug symbols, outputs nvpkg-dev)
+build-dev-nvpkg:
+	$(MAKE) -C cli/nvpkg build-dev
+
+# Remove build and coverage artifacts (delegates to all sub-makefiles).
+clean: clean-go clean-nvpkg
+
+clean-go:
+	$(MAKE) -C api/go clean
+
+clean-nvpkg:
+	$(MAKE) -C cli/nvpkg clean
diff --git a/README.md b/README.md
index 327518c5..f70d7854 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 [![Docs Check][badge-docs-check]][workflow-docs-check]
 [![Go CI][badge-go-ci]][workflow-go-ci]
 [![Go BDD][badge-go-bdd]][workflow-go-bdd]
+[![nvpkg CI][badge-nvpkg-ci]][workflow-nvpkg-ci]
 [![Python Lint][badge-python-lint]][workflow-python-lint]
 [![License][badge-license]][license-file]
 
@@ -19,6 +20,7 @@ The repository supports multiple language implementations (Go, Rust, Zig, and fu
 - 🧾 **Requirements**: [`docs/requirements/README.md`](docs/requirements/README.md)
 - 🧪 **Shared feature files (BDD)**: [`features/`](features/)
 - 🧩 **Go implementation (v1)**: [`api/go/`](api/go/)
+- 🖥️ **CLI implementations**: [`cli/`](cli/) – language-specific CLIs (nvpkg Go, nvpkr Rust, nvpkz Zig); see [cli/README.md](cli/README.md).
 - 🧰 **Python validation tooling**: [`scripts/`](scripts/)
 - 🤝 **Contributing guide**: [`CONTRIBUTING.md`](CONTRIBUTING.md)
 
@@ -30,6 +32,11 @@ The repository supports multiple language implementations (Go, Rust, Zig, and fu
 - **CI**: [Go CI][workflow-go-ci], [Go BDD][workflow-go-bdd]
 - **Local**: See [Testing Standards - Running Tests](#running-tests).
 
+### CLI implementations (language-specific)
+
+- **Overview**: [`cli/README.md`](cli/README.md) – nvpkg (Go), nvpkr (Rust), nvpkz (Zig), and future CLIs.
+- **Go CLI (nvpkg)**: [`cli/nvpkg/`](cli/nvpkg/) – build: `make build-nvpkg`, tests: `make test-nvpkg`.
+
 ### Python (validation tooling)
 
 - **Code**: [`scripts/`](scripts/)
@@ -154,12 +161,15 @@ For deeper details, see these canonical documents:
 
 ```text
 novuspack/
-├── api/                      # Language-specific implementations
+├── api/                      # Language-specific API implementations
 │   └── go/                   # Go implementation
 │       └── v1/               # API version 1
 │           ├── bdd/          # BDD test infrastructure
 │           ├── go.mod        # Go module
 │           └── README.md     # Implementation-specific docs
+├── cli/                      # Language-specific CLI implementations
+│   ├── README.md             # CLI overview (nvpkg, nvpkr, nvpkz, etc.)
+│   └── nvpkg/                # Go CLI
 ├── features/                 # Shared Gherkin feature files (all implementations)
 ├── docs/                     # Shared documentation and specifications
 │   ├── tech_specs/           # API specifications (language-agnostic)
@@ -167,6 +177,31 @@ novuspack/
 └── README.md                 # This file
 ```
 
+## Building
+
+All builds are run from the repository root via the root [Makefile](Makefile).
+
+### Prerequisites
+
+- **Go 1.25+** – required for the Go API ([`api/go/`](api/go/)) and the nvpkg CLI.
+- **Python 3** – required for [documentation and validation tooling](scripts/README.md) (e.g. `make docs-check`, `make lint-python`).
+- **UPX** – optional; needed for the nvpkg release binary (`make build-nvpkg`) to produce a compressed executable.
+
+### nvpkg (Go CLI)
+
+From the repository root:
+
+- `make build-nvpkg` – build release binary `nvpkg` (ldflags -s -w + UPX; requires [UPX](https://upx.github.io/) on PATH).
+- `make build-dev-nvpkg` – build development binary `nvpkg-dev` (with debug symbols).
+
+The binary is produced inside [`cli/nvpkg/`](cli/nvpkg/).
+For build options, scripts, and usage, see [cli/nvpkg/README.md](cli/nvpkg/README.md).
+
+### Go API (library)
+
+The Go implementation in [`api/go/`](api/go/) is a library, not a standalone binary.
+Use it as a Go module dependency; see [api/go/README.md](api/go/README.md) for usage and versioning.
+
 ## Architecture
 
 ### Design Principles
@@ -220,7 +255,8 @@ For detailed information on how the Make targets and Python validation scripts a
 
 From the repository root:
 
-- `make test` - Run unit tests (currently delegates to `api/go/`)
+- `make test` - Run unit tests (Go API and nvpkg CLI)
+- `make test-nvpkg` - Run nvpkg (Go CLI) tests only
 - `make bdd` - Run Go BDD tests (writes output into `tmp/`)
 - `make bdd-ci` - Run Go BDD tests in CI mode (tag-filtered)
 - `make coverage` - Generate `coverage.out`
@@ -301,11 +337,13 @@ For detailed security information, see the [Security Architecture](docs/tech_spe
 [badge-docs-check]: https://github.com/novus-engine/novuspack/actions/workflows/docs-check.yml/badge.svg?branch=main
 [badge-go-ci]: https://github.com/novus-engine/novuspack/actions/workflows/go-ci.yml/badge.svg?branch=main
 [badge-go-bdd]: https://github.com/novus-engine/novuspack/actions/workflows/go-bdd.yml/badge.svg?branch=main
+[badge-nvpkg-ci]: https://github.com/novus-engine/novuspack/actions/workflows/nvpkg-ci.yml/badge.svg?branch=main
 [badge-python-lint]: https://github.com/novus-engine/novuspack/actions/workflows/python-lint.yml/badge.svg?branch=main
 [badge-license]: https://img.shields.io/badge/license-Apache%202.0-blue
 
 [workflow-docs-check]: https://github.com/novus-engine/novuspack/actions/workflows/docs-check.yml
 [workflow-go-ci]: https://github.com/novus-engine/novuspack/actions/workflows/go-ci.yml
 [workflow-go-bdd]: https://github.com/novus-engine/novuspack/actions/workflows/go-bdd.yml
+[workflow-nvpkg-ci]: https://github.com/novus-engine/novuspack/actions/workflows/nvpkg-ci.yml
 [workflow-python-lint]: https://github.com/novus-engine/novuspack/actions/workflows/python-lint.yml
 [license-file]: LICENSE.txt
diff --git a/api/go/Makefile b/api/go/Makefile
index 083cbea1..d196a9d8 100644
--- a/api/go/Makefile
+++ b/api/go/Makefile
@@ -11,7 +11,7 @@ ifneq ($(MAKE),$(SYSTEM_MAKE))
   override MAKE := $(SYSTEM_MAKE)
 endif
 
-.PHONY: test bdd bdd-ci bdd-domain ci tidy go-fmt coverage coverage-html coverage-report validate-go-spec-references apply-go-spec-references
+.PHONY: test bdd bdd-ci bdd-domain ci tidy go-fmt coverage coverage-html coverage-report clean validate-go-spec-references apply-go-spec-references
 
 BDD_TAGS ?= '~@skip && ~@wip'
 BDD_DOMAIN ?= ''
@@ -30,6 +30,11 @@ go-fmt:
 	@go fmt ./...
 	@echo "Formatting complete."
 
+# Remove test and coverage artifacts
+clean:
+	@go clean -testcache
+	@rm -f coverage.out coverage.html
+
 # Run all unit tests
 # Set GOCACHE to a writable location if the default cache is not writable
 # Test actual write capability by attempting to create a test file
@@ -126,6 +131,10 @@ bdd-domain:
 	echo "Exit code: $$exit_code"; \
 	exit $$exit_code
 
+# Use latest golangci-lint so local and CI (.github/workflows/go-ci.yml) stay in sync.
+GOLANGCI_LINT_VERSION ?= latest
+GOLANGCI_LINT := go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@$(GOLANGCI_LINT_VERSION)
+
 lint:
 	@echo "Checking code formatting..."
 	@if [ "$$(gofmt -s -l . | wc -l)" -gt 0 ]; then \
@@ -137,8 +146,8 @@ lint:
 	@echo "Running go vet..."
 	@go vet ./...
 	@echo ""
-	@echo "Running golangci-lint..."
-	@golangci-lint run ./...
+	@echo "Running golangci-lint $(GOLANGCI_LINT_VERSION)..."
+	@$(GOLANGCI_LINT) run ./...
 
 # Go signature validation - validates Go signatures in implementation against tech specs
 # NOTE: This target must be kept in sync with .github/workflows/docs-check.yml.
@@ -244,19 +253,19 @@ ci:
 		GOCACHE="$$CACHE_DIR" go vet ./...; \
 	fi
 	@echo ""
-	@echo "6. Running golangci-lint..."
+	@echo "6. Running golangci-lint $(GOLANGCI_LINT_VERSION)..."
 	@if ( [ -w "$(HOME)/.cache/go-build" ] 2>/dev/null && touch "$(HOME)/.cache/go-build/.write-test" 2>/dev/null && rm -f "$(HOME)/.cache/go-build/.write-test" ) || [ -z "$(HOME)" ]; then \
-		golangci-lint run ./...; \
-		golangci-lint run --build-tags=bdd ./...; \
+		$(GOLANGCI_LINT) run ./...; \
+		$(GOLANGCI_LINT) run --build-tags=bdd ./...; \
 	else \
 		CACHE_DIR="$$(cd ../.. && pwd)/tmp/go-cache"; \
 		mkdir -p "$$CACHE_DIR"; \
-		GOCACHE="$$CACHE_DIR" golangci-lint run ./... || { \
+		GOCACHE="$$CACHE_DIR" $(GOLANGCI_LINT) run ./... || { \
 			echo "Error: golangci-lint failed. This may be due to Go module cache permissions."; \
 			echo "Try running 'go mod tidy' or check Go module cache permissions."; \
 			exit 1; \
 		}; \
-		GOCACHE="$$CACHE_DIR" golangci-lint run --build-tags=bdd ./... || { \
+		GOCACHE="$$CACHE_DIR" $(GOLANGCI_LINT) run --build-tags=bdd ./... || { \
 			echo "Error: golangci-lint (BDD) failed. This may be due to Go module cache permissions."; \
 			echo "Try running 'go mod tidy' or check Go module cache permissions."; \
 			exit 1; \
diff --git a/api/go/_bdd/steps/core/generic_patterns.go b/api/go/_bdd/steps/core/generic_patterns.go
index 97f01272..5e4c936c 100644
--- a/api/go/_bdd/steps/core/generic_patterns.go
+++ b/api/go/_bdd/steps/core/generic_patterns.go
@@ -2623,7 +2623,7 @@ func commentIsInEmptyState(ctx context.Context) error {
 	if comment == nil {
 		return fmt.Errorf("PackageComment is nil")
 	}
-	if !comment.IsEmpty() {
+	if comment.CommentLength != 0 {
 		return fmt.Errorf("IsEmpty() = false, want true for empty state")
 	}
 	return nil
diff --git a/api/go/_bdd/steps/core/package_lifecycle.go b/api/go/_bdd/steps/core/package_lifecycle.go
index 73a7e645..63ed2143 100644
--- a/api/go/_bdd/steps/core/package_lifecycle.go
+++ b/api/go/_bdd/steps/core/package_lifecycle.go
@@ -10,7 +10,6 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"os"
 	"strings"
 
 	"github.com/cucumber/godog"
@@ -222,34 +221,24 @@ func openPackageIsCalled(ctx context.Context) (context.Context, error) {
 	testCtx := world.NewContext()
 	path := world.TempPath("test-package.nvpk")
 
-	// First create a minimal valid package file on disk using raw binary writes.
-	// This mirrors the test helper createTestPackageFile in package tests.
-	file, err := os.Create(path)
+	// Create a minimal valid package file using the public API (Create + SafeWrite + Close).
+	pkg, err := novuspack.NewPackage()
 	if err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	defer func() { _ = file.Close() }()
-
-	header := novuspack.NewPackageHeader()
-	index := novuspack.NewFileIndex()
-	index.EntryCount = 0
-	index.FirstEntryOffset = uint64(novuspack.PackageHeaderSize)
-
-	header.IndexStart = uint64(novuspack.PackageHeaderSize)
-	header.IndexSize = uint64(index.Size())
-
-	if _, err := header.WriteTo(file); err != nil {
+	if err := pkg.Create(testCtx, path); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	if _, err := index.WriteTo(file); err != nil {
+	if err := pkg.SafeWrite(testCtx, true); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
+	_ = pkg.Close()
 
 	// Now open the package
-	pkg, err := novuspack.OpenPackage(testCtx, path)
+	pkg, err = novuspack.OpenPackage(testCtx, path)
 	if err != nil {
 		world.SetError(err)
 		return ctx, err
@@ -267,33 +256,24 @@ func openPackageReadOnlyIsCalled(ctx context.Context) (context.Context, error) {
 	testCtx := world.NewContext()
 	path := world.TempPath("test-package.nvpk")
 
-	// First create a minimal valid package file on disk using raw binary writes.
-	file, err := os.Create(path)
+	// Create a minimal valid package file using the public API (Create + SafeWrite + Close).
+	pkg, err := novuspack.NewPackage()
 	if err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	defer func() { _ = file.Close() }()
-
-	header := novuspack.NewPackageHeader()
-	index := novuspack.NewFileIndex()
-	index.EntryCount = 0
-	index.FirstEntryOffset = uint64(novuspack.PackageHeaderSize)
-
-	header.IndexStart = uint64(novuspack.PackageHeaderSize)
-	header.IndexSize = uint64(index.Size())
-
-	if _, err := header.WriteTo(file); err != nil {
+	if err := pkg.Create(testCtx, path); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	if _, err := index.WriteTo(file); err != nil {
+	if err := pkg.SafeWrite(testCtx, true); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
+	_ = pkg.Close()
 
 	// Now open the package in read-only mode
-	pkg, err := novuspack.OpenPackageReadOnly(testCtx, path)
+	pkg, err = novuspack.OpenPackageReadOnly(testCtx, path)
 	if err != nil {
 		world.SetError(err)
 		return ctx, err
@@ -318,30 +298,21 @@ func openPackageReadOnlyHasBeenCalledSuccessfully(ctx context.Context) (context.
 	testCtx := world.NewContext()
 	path := world.TempPath("test-package.nvpk")
 
-	// Always create a valid package file (overwrite placeholder if it exists)
-	file, err := os.Create(path)
+	// Create a minimal valid package file using the public API (Create + SafeWrite + Close).
+	pkg, err := novuspack.NewPackage()
 	if err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	defer func() { _ = file.Close() }()
-
-	header := novuspack.NewPackageHeader()
-	index := novuspack.NewFileIndex()
-	index.EntryCount = 0
-	index.FirstEntryOffset = uint64(novuspack.PackageHeaderSize)
-
-	header.IndexStart = uint64(novuspack.PackageHeaderSize)
-	header.IndexSize = uint64(index.Size())
-
-	if _, err := header.WriteTo(file); err != nil {
+	if err := pkg.Create(testCtx, path); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
-	if _, err := index.WriteTo(file); err != nil {
+	if err := pkg.SafeWrite(testCtx, true); err != nil {
 		world.SetError(err)
 		return ctx, err
 	}
+	_ = pkg.Close()
 
 	// Now open the package in read-only mode
 	pkg, err = novuspack.OpenPackageReadOnly(testCtx, path)
diff --git a/api/go/_bdd/steps/core/package_properties.go b/api/go/_bdd/steps/core/package_properties.go
index 4cd2efaf..0de66a38 100644
--- a/api/go/_bdd/steps/core/package_properties.go
+++ b/api/go/_bdd/steps/core/package_properties.go
@@ -132,7 +132,7 @@ func packageCommentHasInvalidUTF8Bytes(ctx context.Context) error {
 		}
 		wf.SetHeader(header)
 	}
-	header.SetFeature(novuspack.FlagHasPackageComment)
+	header.Flags |= novuspack.FlagHasPackageComment
 	header.CommentSize = uint32(len(invalidUTF8))
 
 	return nil
@@ -177,9 +177,8 @@ func packageHasAComment(ctx context.Context) error {
 	// Create a valid package comment using SetComment
 	commentText := "test comment"
 	comment := novuspack.NewPackageComment()
-	if err := comment.SetComment(commentText); err != nil {
-		return fmt.Errorf("failed to set comment: %w", err)
-	}
+	comment.Comment = commentText + "\x00"
+	comment.CommentLength = uint32(len(commentText) + 1)
 
 	// Validate comment
 	if err := comment.Validate(); err != nil {
@@ -199,7 +198,7 @@ func packageHasAComment(ctx context.Context) error {
 		}
 		wf.SetHeader(header)
 	}
-	header.SetFeature(novuspack.FlagHasPackageComment)
+	header.Flags |= novuspack.FlagHasPackageComment
 	header.CommentSize = comment.CommentLength
 
 	return nil
@@ -225,7 +224,7 @@ func packageHasNoComment(ctx context.Context) error {
 		}
 		wf.SetHeader(header)
 	}
-	header.ClearFeature(novuspack.FlagHasPackageComment)
+	header.Flags &^= novuspack.FlagHasPackageComment
 	header.CommentSize = 0
 	header.CommentStart = 0
 
@@ -274,7 +273,7 @@ func packageHasDigitalSignatures(ctx context.Context) error {
 		}
 		wf.SetHeader(header)
 	}
-	header.SetFeature(novuspack.FlagHasSignatures)
+	header.Flags |= novuspack.FlagHasSignatures
 	header.SignatureOffset = 1000 // Example offset
 	return nil
 }
@@ -295,7 +294,7 @@ func packageHasFilesWithPerFileTags(ctx context.Context) error {
 		}
 		wf.SetHeader(header)
 	}
-	header.SetFeature(novuspack.FlagHasPerFileTags)
+	header.Flags |= novuspack.FlagHasPerFileTags
 	return nil
 }
 
diff --git a/api/go/_bdd/steps/file_format/file_entry.go b/api/go/_bdd/steps/file_format/file_entry.go
index 50742b70..b317c44d 100644
--- a/api/go/_bdd/steps/file_format/file_entry.go
+++ b/api/go/_bdd/steps/file_format/file_entry.go
@@ -9,7 +9,9 @@ package file_format
 import (
 	"bytes"
 	"context"
+	"encoding/binary"
 	"fmt"
+	"io"
 	"strconv"
 	"strings"
 
@@ -1290,6 +1292,109 @@ func aHashEntryWithAllFieldsSet(ctx context.Context) error {
 	return nil
 }
 
+// BDD-local helpers for HashEntry/OptionalDataEntry (API serialize/validate methods are unexported).
+// Format matches package_file_format.md and metadata package.
+
+func writeHashEntryTo(w io.Writer, h *novuspack.HashEntry) (int64, error) {
+	var n int64
+	if err := binary.Write(w, binary.LittleEndian, h.HashType); err != nil {
+		return n, err
+	}
+	n++
+	if err := binary.Write(w, binary.LittleEndian, h.HashPurpose); err != nil {
+		return n, err
+	}
+	n++
+	if err := binary.Write(w, binary.LittleEndian, h.HashLength); err != nil {
+		return n, err
+	}
+	n += 2
+	written, err := w.Write(h.HashData)
+	if err != nil {
+		return n, err
+	}
+	return n + int64(written), nil
+}
+
+func readHashEntryFrom(r io.Reader) (novuspack.HashEntry, int64, error) {
+	var h novuspack.HashEntry
+	var n int64
+	if err := binary.Read(r, binary.LittleEndian, &h.HashType); err != nil {
+		return h, n, err
+	}
+	n++
+	if err := binary.Read(r, binary.LittleEndian, &h.HashPurpose); err != nil {
+		return h, n, err
+	}
+	n++
+	if err := binary.Read(r, binary.LittleEndian, &h.HashLength); err != nil {
+		return h, n, err
+	}
+	n += 2
+	h.HashData = make([]byte, h.HashLength)
+	read, err := io.ReadFull(r, h.HashData)
+	if err != nil {
+		return h, n, err
+	}
+	return h, n + int64(read), nil
+}
+
+func validateHashEntry(h *novuspack.HashEntry) error {
+	if h == nil || len(h.HashData) == 0 {
+		return fmt.Errorf("hash data cannot be nil or empty")
+	}
+	if h.HashLength != uint16(len(h.HashData)) {
+		return fmt.Errorf("HashLength %d does not match HashData length %d", h.HashLength, len(h.HashData))
+	}
+	return nil
+}
+
+func writeOptionalDataEntryTo(w io.Writer, o *novuspack.OptionalDataEntry) (int64, error) {
+	var n int64
+	if err := binary.Write(w, binary.LittleEndian, o.DataType); err != nil {
+		return n, err
+	}
+	n++
+	if err := binary.Write(w, binary.LittleEndian, o.DataLength); err != nil {
+		return n, err
+	}
+	n += 2
+	written, err := w.Write(o.Data)
+	if err != nil {
+		return n, err
+	}
+	return n + int64(written), nil
+}
+
+func readOptionalDataEntryFrom(r io.Reader) (*novuspack.OptionalDataEntry, int64, error) {
+	o := &novuspack.OptionalDataEntry{}
+	var n int64
+	if err := binary.Read(r, binary.LittleEndian, &o.DataType); err != nil {
+		return nil, n, err
+	}
+	n++
+	if err := binary.Read(r, binary.LittleEndian, &o.DataLength); err != nil {
+		return nil, n, err
+	}
+	n += 2
+	o.Data = make([]byte, o.DataLength)
+	read, err := io.ReadFull(r, o.Data)
+	if err != nil {
+		return nil, n, err
+	}
+	return o, n + int64(read), nil
+}
+
+func validateOptionalDataEntry(o *novuspack.OptionalDataEntry) error {
+	if o == nil || len(o.Data) == 0 {
+		return fmt.Errorf("optional data cannot be nil or empty")
+	}
+	if o.DataLength != uint16(len(o.Data)) {
+		return fmt.Errorf("DataLength %d does not match Data length %d", o.DataLength, len(o.Data))
+	}
+	return nil
+}
+
 func hashEntryWriteToIsCalledWithWriter(ctx context.Context) (context.Context, error) {
 	world := getWorldFileFormat(ctx)
 	if world == nil {
@@ -1301,14 +1406,12 @@ func hashEntryWriteToIsCalledWithWriter(ctx context.Context) (context.Context, e
 	}
 	// Update HashLength to match actual data
 	hashEntry.HashLength = uint16(len(hashEntry.HashData))
-	// Serialize using WriteTo
 	var buf bytes.Buffer
-	_, err := hashEntry.WriteTo(&buf)
+	_, err := writeHashEntryTo(&buf, hashEntry)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return ctx, fmt.Errorf("WriteTo failed: %w", err)
 	}
-	// Store serialized data
 	world.SetPackageMetadata("hashentry_serialized", buf.Bytes())
 	return ctx, nil
 }
@@ -1346,13 +1449,10 @@ func writtenDataMatchesHashEntryContent(ctx context.Context) error {
 	if !ok {
 		return fmt.Errorf("serialized data is not a byte slice")
 	}
-	// Deserialize and compare
-	var readHashEntry novuspack.HashEntry
-	_, err := readHashEntry.ReadFrom(bytes.NewReader(buf))
+	readHashEntry, _, err := readHashEntryFrom(bytes.NewReader(buf))
 	if err != nil {
 		return fmt.Errorf("failed to read back serialized data: %w", err)
 	}
-	// Compare key fields
 	if readHashEntry.HashType != originalHashEntry.HashType {
 		return fmt.Errorf("HashType mismatch: %d != %d", readHashEntry.HashType, originalHashEntry.HashType)
 	}
@@ -1376,7 +1476,7 @@ func aReaderWithValidHashEntryData(ctx context.Context) (context.Context, error)
 	}
 	hashEntry.HashLength = uint16(len(hashEntry.HashData))
 	var buf bytes.Buffer
-	_, err := hashEntry.WriteTo(&buf)
+	_, err := writeHashEntryTo(&buf, hashEntry)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize hash entry: %w", err)
 	}
@@ -1398,15 +1498,12 @@ func hashEntryReadFromIsCalledWithReader(ctx context.Context) (context.Context,
 	if !ok {
 		return ctx, fmt.Errorf("reader data is not a byte slice")
 	}
-	// Read hash entry using ReadFrom
-	hashEntry := &novuspack.HashEntry{}
-	_, err := hashEntry.ReadFrom(bytes.NewReader(buf))
+	entry, _, err := readHashEntryFrom(bytes.NewReader(buf))
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
-		// Return nil to allow error scenarios to continue and check for the error
 		return ctx, nil
 	}
-	world.SetHashEntry(hashEntry)
+	world.SetHashEntry(&entry)
 	return ctx, nil
 }
 
@@ -1454,7 +1551,7 @@ func hashEntryIsValid(ctx context.Context) error {
 	if hashEntry == nil {
 		return fmt.Errorf("no hash entry available")
 	}
-	err := hashEntry.Validate()
+	err := validateHashEntry(hashEntry)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return fmt.Errorf("hash entry validation failed: %w", err)
@@ -1550,16 +1647,13 @@ func optionalDataEntryWriteToIsCalledWithWriter(ctx context.Context) (context.Co
 	if optionalDataEntry == nil {
 		return ctx, fmt.Errorf("no optional data entry available")
 	}
-	// Update DataLength to match actual data
 	optionalDataEntry.DataLength = uint16(len(optionalDataEntry.Data))
-	// Serialize using WriteTo
 	var buf bytes.Buffer
-	_, err := optionalDataEntry.WriteTo(&buf)
+	_, err := writeOptionalDataEntryTo(&buf, optionalDataEntry)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return ctx, fmt.Errorf("WriteTo failed: %w", err)
 	}
-	// Store serialized data
 	world.SetPackageMetadata("optionaldataentry_serialized", buf.Bytes())
 	return ctx, nil
 }
@@ -1597,13 +1691,10 @@ func writtenDataMatchesOptionalDataEntryContent(ctx context.Context) error {
 	if !ok {
 		return fmt.Errorf("serialized data is not a byte slice")
 	}
-	// Deserialize and compare
-	var readOptionalDataEntry novuspack.OptionalDataEntry
-	_, err := readOptionalDataEntry.ReadFrom(bytes.NewReader(buf))
+	readOptionalDataEntry, _, err := readOptionalDataEntryFrom(bytes.NewReader(buf))
 	if err != nil {
 		return fmt.Errorf("failed to read back serialized data: %w", err)
 	}
-	// Compare key fields
 	if readOptionalDataEntry.DataType != originalOptionalDataEntry.DataType {
 		return fmt.Errorf("DataType mismatch: %d != %d", readOptionalDataEntry.DataType, originalOptionalDataEntry.DataType)
 	}
@@ -1626,7 +1717,7 @@ func aReaderWithValidOptionalDataEntryData(ctx context.Context) (context.Context
 	}
 	optionalDataEntry.DataLength = uint16(len(optionalDataEntry.Data))
 	var buf bytes.Buffer
-	_, err := optionalDataEntry.WriteTo(&buf)
+	_, err := writeOptionalDataEntryTo(&buf, optionalDataEntry)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize optional data entry: %w", err)
 	}
@@ -1648,15 +1739,12 @@ func optionalDataEntryReadFromIsCalledWithReader(ctx context.Context) (context.C
 	if !ok {
 		return ctx, fmt.Errorf("reader data is not a byte slice")
 	}
-	// Read optional data entry using ReadFrom
-	optionalDataEntry := &novuspack.OptionalDataEntry{}
-	_, err := optionalDataEntry.ReadFrom(bytes.NewReader(buf))
+	entry, _, err := readOptionalDataEntryFrom(bytes.NewReader(buf))
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
-		// Return nil to allow error scenarios to continue and check for the error
 		return ctx, nil
 	}
-	world.SetOptionalData(optionalDataEntry)
+	world.SetOptionalData(entry)
 	return ctx, nil
 }
 
@@ -1704,7 +1792,7 @@ func optionalDataEntryIsValid(ctx context.Context) error {
 	if optionalDataEntry == nil {
 		return fmt.Errorf("no optional data entry available")
 	}
-	err := optionalDataEntry.Validate()
+	err := validateOptionalDataEntry(optionalDataEntry)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return fmt.Errorf("optional data entry validation failed: %w", err)
@@ -2204,7 +2292,7 @@ func offsetsAreCalculatedCorrectly(ctx context.Context) error {
 	if entry.HashDataOffset != uint32(pathsSize) {
 		return fmt.Errorf("HashDataOffset = %d, want %d", entry.HashDataOffset, pathsSize)
 	}
-	hashSize := lo.SumBy(entry.Hashes, func(h novuspack.HashEntry) int { return h.Size() })
+	hashSize := lo.SumBy(entry.Hashes, func(h novuspack.HashEntry) int { return 4 + int(h.HashLength) })
 	if entry.OptionalDataOffset != uint32(pathsSize+hashSize) {
 		return fmt.Errorf("OptionalDataOffset = %d, want %d", entry.OptionalDataOffset, pathsSize+hashSize)
 	}
diff --git a/api/go/_bdd/steps/file_format/file_index.go b/api/go/_bdd/steps/file_format/file_index.go
index 2bf5a3e2..ce8ef2c3 100644
--- a/api/go/_bdd/steps/file_format/file_index.go
+++ b/api/go/_bdd/steps/file_format/file_index.go
@@ -9,7 +9,9 @@ package file_format
 import (
 	"bytes"
 	"context"
+	"encoding/binary"
 	"fmt"
+	"io"
 
 	"github.com/cucumber/godog"
 	novuspack "github.com/novus-engine/novuspack/api/go"
@@ -38,7 +40,88 @@ func getWorldFileFormatIndex(ctx context.Context) worldFileFormatIndex {
 	return nil
 }
 
-// Helper functions are defined in file_entry.go to avoid duplication
+// BDD-local helpers for FileIndex (API WriteTo/ReadFrom/Validate are unexported).
+
+func fileIndexSize(index *novuspack.FileIndex) int {
+	if index == nil {
+		return 16
+	}
+	return 16 + len(index.Entries)*int(novuspack.IndexEntrySize)
+}
+
+func writeFileIndexTo(w io.Writer, index *novuspack.FileIndex) (int64, error) {
+	if index == nil {
+		return 0, fmt.Errorf("file index is nil")
+	}
+	entryCount := uint32(len(index.Entries))
+	if err := binary.Write(w, binary.LittleEndian, entryCount); err != nil {
+		return 0, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, index.Reserved); err != nil {
+		return 4, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, index.FirstEntryOffset); err != nil {
+		return 8, err
+	}
+	n := int64(16)
+	for i := range index.Entries {
+		if err := binary.Write(w, binary.LittleEndian, &index.Entries[i]); err != nil {
+			return n, err
+		}
+		n += novuspack.IndexEntrySize
+	}
+	return n, nil
+}
+
+func readFileIndexFrom(r io.Reader) (*novuspack.FileIndex, int64, error) {
+	index := &novuspack.FileIndex{}
+	var n int64
+	if err := binary.Read(r, binary.LittleEndian, &index.EntryCount); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &index.Reserved); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &index.FirstEntryOffset); err != nil {
+		return nil, n, err
+	}
+	n += 8
+	index.Entries = make([]novuspack.IndexEntry, 0, index.EntryCount)
+	for i := uint32(0); i < index.EntryCount; i++ {
+		var e novuspack.IndexEntry
+		if err := binary.Read(r, binary.LittleEndian, &e); err != nil {
+			return nil, n, err
+		}
+		index.Entries = append(index.Entries, e)
+		n += novuspack.IndexEntrySize
+	}
+	return index, n, nil
+}
+
+func validateFileIndex(index *novuspack.FileIndex) error {
+	if index == nil {
+		return fmt.Errorf("file index is nil")
+	}
+	if index.Reserved != 0 {
+		return fmt.Errorf("reserved field must be zero")
+	}
+	if uint32(len(index.Entries)) != index.EntryCount {
+		return fmt.Errorf("EntryCount %d does not match Entries length %d", index.EntryCount, len(index.Entries))
+	}
+	seen := make(map[uint64]bool)
+	for _, e := range index.Entries {
+		if e.FileID == 0 {
+			return fmt.Errorf("FileID must be non-zero")
+		}
+		if seen[e.FileID] {
+			return fmt.Errorf("duplicate FileID %d", e.FileID)
+		}
+		seen[e.FileID] = true
+	}
+	return nil
+}
 
 // RegisterFileFormatIndexSteps registers step definitions for file index operations.
 func RegisterFileFormatIndexSteps(ctx *godog.ScenarioContext) {
@@ -186,14 +269,12 @@ func fileIndexWriteToIsCalledWithWriter(ctx context.Context) (context.Context, e
 	if index == nil {
 		return ctx, fmt.Errorf("no file index available")
 	}
-	// Serialize using WriteTo
 	var buf bytes.Buffer
-	_, err := index.WriteTo(&buf)
+	_, err := writeFileIndexTo(&buf, index)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return ctx, fmt.Errorf("WriteTo failed: %w", err)
 	}
-	// Store serialized data
 	world.SetPackageMetadata("fileindex_serialized", buf.Bytes())
 	return ctx, nil
 }
@@ -277,13 +358,10 @@ func writtenDataMatchesFileIndexContent(ctx context.Context) error {
 	if !ok {
 		return fmt.Errorf("serialized data is not a byte slice")
 	}
-	// Deserialize and compare
-	var readIndex novuspack.FileIndex
-	_, err := readIndex.ReadFrom(bytes.NewReader(buf))
+	readIndex, _, err := readFileIndexFrom(bytes.NewReader(buf))
 	if err != nil {
 		return fmt.Errorf("failed to read back serialized data: %w", err)
 	}
-	// Compare key fields
 	if readIndex.EntryCount != originalIndex.EntryCount {
 		return fmt.Errorf("EntryCount mismatch: %d != %d", readIndex.EntryCount, originalIndex.EntryCount)
 	}
@@ -305,7 +383,7 @@ func aReaderWithValidFileIndexData(ctx context.Context) (context.Context, error)
 	}
 	index.EntryCount = uint32(len(index.Entries))
 	var buf bytes.Buffer
-	_, err := index.WriteTo(&buf)
+	_, err := writeFileIndexTo(&buf, index)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize index: %w", err)
 	}
@@ -327,12 +405,9 @@ func fileIndexReadFromIsCalledWithReader(ctx context.Context) (context.Context,
 	if !ok {
 		return ctx, fmt.Errorf("reader data is not a byte slice")
 	}
-	// Read index using ReadFrom
-	index := &novuspack.FileIndex{}
-	_, err := index.ReadFrom(bytes.NewReader(buf))
+	index, _, err := readFileIndexFrom(bytes.NewReader(buf))
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
-		// Return nil to allow error scenarios to continue and check for the error
 		return ctx, nil
 	}
 	world.SetFileIndex(index)
@@ -385,7 +460,7 @@ func fileIndexIsValid(ctx context.Context) error {
 	if index == nil {
 		return fmt.Errorf("no file index available")
 	}
-	err := index.Validate()
+	err := validateFileIndex(index)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return fmt.Errorf("file index validation failed: %w", err)
diff --git a/api/go/_bdd/steps/file_format/header.go b/api/go/_bdd/steps/file_format/header.go
index f1d6b022..e6c32334 100644
--- a/api/go/_bdd/steps/file_format/header.go
+++ b/api/go/_bdd/steps/file_format/header.go
@@ -9,8 +9,10 @@ package file_format
 import (
 	"bytes"
 	"context"
+	"encoding/binary"
 	"errors"
 	"fmt"
+	"io"
 	"strconv"
 
 	"github.com/cucumber/godog"
@@ -52,7 +54,38 @@ type worldFileFormat interface {
 	GetPackageMetadata(string) (interface{}, bool)
 }
 
-// Helper functions are defined in file_entry.go to avoid duplication
+// writePackageHeaderTo and readPackageHeaderFrom replicate header I/O (API methods are unexported).
+func writePackageHeaderTo(w io.Writer, header *novuspack.PackageHeader) (int64, error) {
+	if err := binary.Write(w, binary.LittleEndian, header); err != nil {
+		return 0, err
+	}
+	return novuspack.PackageHeaderSize, nil
+}
+
+func readPackageHeaderFrom(r io.Reader) (*novuspack.PackageHeader, int64, error) {
+	h := &novuspack.PackageHeader{}
+	if err := binary.Read(r, binary.LittleEndian, h); err != nil {
+		return nil, 0, err
+	}
+	return h, novuspack.PackageHeaderSize, nil
+}
+
+// validatePackageHeader replicates header validation (API validate is unexported).
+func validatePackageHeader(header *novuspack.PackageHeader) error {
+	if header == nil {
+		return fmt.Errorf("header is nil")
+	}
+	if header.Magic != novuspack.NVPKMagic {
+		return fmt.Errorf("invalid magic number: 0x%08X", header.Magic)
+	}
+	if header.FormatVersion != novuspack.FormatVersion {
+		return fmt.Errorf("unsupported format version: %d", header.FormatVersion)
+	}
+	if header.Reserved != 0 {
+		return fmt.Errorf("reserved field must be 0")
+	}
+	return nil
+}
 
 // RegisterFileFormatHeaderSteps registers step definitions for package header operations.
 func RegisterFileFormatHeaderSteps(ctx *godog.ScenarioContext) {
@@ -175,7 +208,7 @@ func theHeaderIsParsed(ctx context.Context) (context.Context, error) {
 	if header == nil {
 		return ctx, fmt.Errorf("no header available to parse")
 	}
-	err := header.Validate()
+	err := validatePackageHeader(header)
 	if err != nil {
 		// Wrap fileformat errors as PackageError for BDD test expectations
 		pkgErr := pkgerrors.NewPackageError[struct{}](pkgerrors.ErrTypeValidation, "invalid package header", err, struct{}{})
@@ -414,21 +447,18 @@ func archivePartInfoPacksPartAndTotalCorrectly(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	// Test that GetArchivePart and GetArchiveTotal work correctly
-	part := header.GetArchivePart()
-	total := header.GetArchiveTotal()
-	// Verify the values can be extracted
+	part := uint16(header.ArchivePartInfo >> 16)
+	total := uint16(header.ArchivePartInfo & 0xFFFF)
 	_ = part
 	_ = total
-	// Verify SetArchivePartInfo works
 	testPart := uint16(2)
 	testTotal := uint16(3)
-	header.SetArchivePartInfo(testPart, testTotal)
-	if header.GetArchivePart() != testPart {
-		return fmt.Errorf("GetArchivePart returned %d, expected %d", header.GetArchivePart(), testPart)
+	header.ArchivePartInfo = (uint32(testPart) << 16) | uint32(testTotal)
+	if uint16(header.ArchivePartInfo>>16) != testPart {
+		return fmt.Errorf("ArchivePartInfo part = %d, expected %d", header.ArchivePartInfo>>16, testPart)
 	}
-	if header.GetArchiveTotal() != testTotal {
-		return fmt.Errorf("GetArchiveTotal returned %d, expected %d", header.GetArchiveTotal(), testTotal)
+	if uint16(header.ArchivePartInfo&0xFFFF) != testTotal {
+		return fmt.Errorf("ArchivePartInfo total = %d, expected %d", header.ArchivePartInfo&0xFFFF, testTotal)
 	}
 	return nil
 }
@@ -492,7 +522,7 @@ func aStructuredInvalidFormatErrorIsReturned(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	err := header.Validate()
+	err := validatePackageHeader(header)
 	if err == nil {
 		return fmt.Errorf("expected validation error but got none")
 	}
@@ -530,7 +560,7 @@ func aStructuredInvalidHeaderErrorIsReturned(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	err := header.Validate()
+	err := validatePackageHeader(header)
 	if err == nil {
 		return fmt.Errorf("expected validation error but got none")
 	}
@@ -701,9 +731,8 @@ func writeToIsCalledWithWriter(ctx context.Context) (context.Context, error) {
 	if header == nil {
 		return ctx, fmt.Errorf("no header available")
 	}
-	// Serialize header using WriteTo
 	var buf bytes.Buffer
-	_, err := header.WriteTo(&buf)
+	_, err := writePackageHeaderTo(&buf, header)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return ctx, fmt.Errorf("WriteTo failed: %w", err)
@@ -765,13 +794,10 @@ func writtenDataMatchesHeaderContent(ctx context.Context) error {
 	if !ok {
 		return fmt.Errorf("serialized data is not a byte slice")
 	}
-	// Deserialize and compare
-	var readHeader novuspack.PackageHeader
-	_, err := readHeader.ReadFrom(bytes.NewReader(buf))
+	readHeader, _, err := readPackageHeaderFrom(bytes.NewReader(buf))
 	if err != nil {
 		return fmt.Errorf("failed to read back serialized data: %w", err)
 	}
-	// Compare key fields
 	if readHeader.Magic != originalHeader.Magic {
 		return fmt.Errorf("Magic mismatch: %x != %x", readHeader.Magic, originalHeader.Magic)
 	}
@@ -786,16 +812,14 @@ func aReaderWithValidHeaderData(ctx context.Context) (context.Context, error) {
 	if world == nil {
 		return ctx, godog.ErrUndefined
 	}
-	// Create a valid header and serialize it
 	header := novuspack.NewPackageHeader()
 	header.PackageDataVersion = 1
 	header.MetadataVersion = 1
 	var buf bytes.Buffer
-	_, err := header.WriteTo(&buf)
+	_, err := writePackageHeaderTo(&buf, header)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize header: %w", err)
 	}
-	// Store the reader data
 	world.SetPackageMetadata("header_reader_data", buf.Bytes())
 	return ctx, nil
 }
@@ -814,13 +838,9 @@ func readFromIsCalledWithReader(ctx context.Context) (context.Context, error) {
 	if !ok {
 		return ctx, fmt.Errorf("reader data is not a byte slice")
 	}
-	// Read header using ReadFrom
-	header := &novuspack.PackageHeader{}
-	_, err := header.ReadFrom(bytes.NewReader(buf))
+	header, _, err := readPackageHeaderFrom(bytes.NewReader(buf))
 	if err != nil {
-		// Wrap fileformat errors as PackageError for BDD test expectations
 		world.SetError(wrapFileFormatError(err))
-		// Return nil to allow error scenarios to continue and check for the error
 		return ctx, nil
 	}
 	world.SetHeader(header)
@@ -871,7 +891,7 @@ func headerIsValid(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	err := header.Validate()
+	err := validatePackageHeader(header)
 	if err != nil {
 		// Wrap fileformat errors as PackageError for BDD test expectations
 		pkgErr := pkgerrors.NewPackageError[struct{}](pkgerrors.ErrTypeValidation, "invalid package header", err, struct{}{})
@@ -950,11 +970,10 @@ func aReaderWithHeaderDataWhereMagicIsInvalid(ctx context.Context) (context.Cont
 	if world == nil {
 		return ctx, godog.ErrUndefined
 	}
-	// Create a header with invalid magic and serialize it
 	header := novuspack.NewPackageHeader()
 	header.Magic = 0xDEADBEEF // Invalid magic
 	var buf bytes.Buffer
-	_, err := header.WriteTo(&buf)
+	_, err := writePackageHeaderTo(&buf, header)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize header: %w", err)
 	}
diff --git a/api/go/_bdd/steps/file_format/parsing.go b/api/go/_bdd/steps/file_format/parsing.go
index 05dcee0b..9bbdecfc 100644
--- a/api/go/_bdd/steps/file_format/parsing.go
+++ b/api/go/_bdd/steps/file_format/parsing.go
@@ -321,8 +321,7 @@ func bits15To8EncodePackageCompressionType(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	// Verify GetCompressionType extracts bits 15-8 correctly
-	compressionType := header.GetCompressionType()
+	compressionType := uint8((header.Flags & novuspack.FlagsMaskCompressionType) >> novuspack.FlagsShiftCompressionType)
 	// Verify it's in the valid range (0-3)
 	if compressionType > 3 {
 		return fmt.Errorf("compression type %d is out of valid range (0-3)", compressionType)
@@ -339,8 +338,7 @@ func bits7To0EncodePackageFeatures(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	// Verify GetFeatures extracts bits 7-0 correctly
-	features := header.GetFeatures()
+	features := uint8(header.Flags & novuspack.FlagsMaskFeatures)
 	_ = features // Features are just a bitmask, no specific validation needed
 	return nil
 }
@@ -371,7 +369,7 @@ func packageCompressionTypeIsSetToNumeric(ctx context.Context, compressionType s
 		world.SetError(pkgErr)
 		return ctx, nil // Don't fail here, let validation step check the error
 	}
-	header.SetCompressionType(uint8(ct))
+	header.Flags = (header.Flags & ^uint32(novuspack.FlagsMaskCompressionType)) | (uint32(ct) << novuspack.FlagsShiftCompressionType)
 	return ctx, nil
 }
 
@@ -396,7 +394,7 @@ func packageCompressionTypeIsSetToValueGreaterThan(ctx context.Context, threshol
 	}
 	// Set to a value greater than threshold (for error testing)
 	invalidValue := uint8(thresh + 1)
-	header.SetCompressionType(invalidValue)
+	header.Flags = (header.Flags & ^uint32(novuspack.FlagsMaskCompressionType)) | (uint32(invalidValue) << novuspack.FlagsShiftCompressionType)
 	// Wrap as PackageError for BDD test expectations
 	pkgErr := pkgerrors.NewPackageError[struct{}](pkgerrors.ErrTypeValidation,
 		fmt.Sprintf("compression type %d exceeds maximum value 3", invalidValue), nil, struct{}{})
@@ -425,8 +423,7 @@ func packageCompressionTypeIsSpecifiedInHeaderFlags(ctx context.Context) error {
 		}
 		world.SetHeader(header)
 	}
-	// Verify compression type is encoded in bits 15-8
-	compressionType := header.GetCompressionType()
+	compressionType := uint8((header.Flags & novuspack.FlagsMaskCompressionType) >> novuspack.FlagsShiftCompressionType)
 	// Verify it can be extracted correctly (this validates the encoding location)
 	_ = compressionType
 	// Verify bits 15-8 contain the compression type
@@ -453,7 +450,7 @@ func flagsBits15To8Equal(ctx context.Context, encodedValue string) error {
 	if err != nil {
 		return fmt.Errorf("invalid encoded value format: %s", encodedValue)
 	}
-	actual := header.GetCompressionType()
+	actual := uint8((header.Flags & novuspack.FlagsMaskCompressionType) >> novuspack.FlagsShiftCompressionType)
 	if actual != uint8(expected) {
 		return fmt.Errorf("compression type is %d, expected %d", actual, expected)
 	}
@@ -469,11 +466,11 @@ func compressionTypeCanBeDecodedCorrectly(ctx context.Context) error {
 	if header == nil {
 		return fmt.Errorf("no header available")
 	}
-	// Test that SetCompressionType and GetCompressionType work correctly
 	for i := uint8(0); i <= 3; i++ {
-		header.SetCompressionType(i)
-		if header.GetCompressionType() != i {
-			return fmt.Errorf("compression type %d was set but GetCompressionType returned %d", i, header.GetCompressionType())
+		header.Flags = (header.Flags & ^uint32(novuspack.FlagsMaskCompressionType)) | (uint32(i) << novuspack.FlagsShiftCompressionType)
+		got := uint8((header.Flags & novuspack.FlagsMaskCompressionType) >> novuspack.FlagsShiftCompressionType)
+		if got != i {
+			return fmt.Errorf("compression type %d was set but got %d", i, got)
 		}
 	}
 	return nil
diff --git a/api/go/_bdd/steps/file_format/signatures.go b/api/go/_bdd/steps/file_format/signatures.go
index 185fa517..2ac24506 100644
--- a/api/go/_bdd/steps/file_format/signatures.go
+++ b/api/go/_bdd/steps/file_format/signatures.go
@@ -9,7 +9,9 @@ package file_format
 import (
 	"bytes"
 	"context"
+	"encoding/binary"
 	"fmt"
+	"io"
 
 	"github.com/cucumber/godog"
 	novuspack "github.com/novus-engine/novuspack/api/go"
@@ -38,7 +40,105 @@ func getWorldFileFormatSignature(ctx context.Context) worldFileFormatSignature {
 	return nil
 }
 
-// Helper functions are defined in file_entry.go to avoid duplication
+// BDD-local helpers for Signature (API WriteTo/ReadFrom are unexported).
+
+func writeSignatureTo(w io.Writer, s *novuspack.Signature) (int64, error) {
+	commentLen := uint16(len(s.SignatureComment))
+	sigSize := uint32(len(s.SignatureData))
+	if err := binary.Write(w, binary.LittleEndian, s.SignatureType); err != nil {
+		return 0, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, sigSize); err != nil {
+		return 4, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, s.SignatureFlags); err != nil {
+		return 8, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, s.SignatureTimestamp); err != nil {
+		return 12, err
+	}
+	if err := binary.Write(w, binary.LittleEndian, commentLen); err != nil {
+		return 16, err
+	}
+	n := int64(18)
+	if commentLen > 0 {
+		written, err := w.Write([]byte(s.SignatureComment))
+		if err != nil {
+			return n, err
+		}
+		n += int64(written)
+	}
+	if sigSize > 0 {
+		written, err := w.Write(s.SignatureData)
+		if err != nil {
+			return n, err
+		}
+		n += int64(written)
+	}
+	return n, nil
+}
+
+func readSignatureFrom(r io.Reader) (*novuspack.Signature, int64, error) {
+	s := &novuspack.Signature{}
+	var n int64
+	if err := binary.Read(r, binary.LittleEndian, &s.SignatureType); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &s.SignatureSize); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &s.SignatureFlags); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &s.SignatureTimestamp); err != nil {
+		return nil, n, err
+	}
+	n += 4
+	if err := binary.Read(r, binary.LittleEndian, &s.CommentLength); err != nil {
+		return nil, n, err
+	}
+	n += 2
+	if s.CommentLength > 0 {
+		comment := make([]byte, s.CommentLength)
+		read, err := io.ReadFull(r, comment)
+		if err != nil {
+			return nil, n, err
+		}
+		n += int64(read)
+		s.SignatureComment = string(comment)
+	}
+	if s.SignatureSize > 0 {
+		s.SignatureData = make([]byte, s.SignatureSize)
+		read, err := io.ReadFull(r, s.SignatureData)
+		if err != nil {
+			return nil, n, err
+		}
+		n += int64(read)
+	}
+	return s, n, nil
+}
+
+func validateSignature(s *novuspack.Signature) error {
+	if s == nil {
+		return fmt.Errorf("signature is nil")
+	}
+	if s.SignatureType == 0 {
+		return fmt.Errorf("signature type cannot be zero")
+	}
+	if len(s.SignatureData) == 0 {
+		return fmt.Errorf("signature data cannot be nil or empty")
+	}
+	if uint32(len(s.SignatureData)) != s.SignatureSize {
+		return fmt.Errorf("signature size mismatch")
+	}
+	if s.SignatureComment != "" && uint16(len(s.SignatureComment)) != s.CommentLength {
+		return fmt.Errorf("comment length mismatch")
+	}
+	return nil
+}
 
 // RegisterFileFormatSignatureSteps registers step definitions for signature parsing.
 func RegisterFileFormatSignatureSteps(ctx *godog.ScenarioContext) {
@@ -248,14 +348,12 @@ func signatureWriteToIsCalledWithWriter(ctx context.Context) (context.Context, e
 	if sig == nil {
 		return ctx, fmt.Errorf("no signature available")
 	}
-	// Serialize using WriteTo
 	var buf bytes.Buffer
-	_, err := sig.WriteTo(&buf)
+	_, err := writeSignatureTo(&buf, sig)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return ctx, fmt.Errorf("WriteTo failed: %w", err)
 	}
-	// Store serialized data
 	world.SetPackageMetadata("signature_serialized", buf.Bytes())
 	return ctx, nil
 }
@@ -356,13 +454,10 @@ func writtenDataMatchesSignatureContent(ctx context.Context) error {
 	if !ok {
 		return fmt.Errorf("serialized data is not a byte slice")
 	}
-	// Deserialize and compare
-	var readSig novuspack.Signature
-	_, err := readSig.ReadFrom(bytes.NewReader(buf))
+	readSig, _, err := readSignatureFrom(bytes.NewReader(buf))
 	if err != nil {
 		return fmt.Errorf("failed to read back serialized data: %w", err)
 	}
-	// Compare key fields
 	if readSig.SignatureType != originalSig.SignatureType {
 		return fmt.Errorf("SignatureType mismatch: %d != %d", readSig.SignatureType, originalSig.SignatureType)
 	}
@@ -388,7 +483,7 @@ func aReaderWithValidSignatureData(ctx context.Context) (context.Context, error)
 	}
 	sig.SignatureSize = uint32(len(sig.SignatureData))
 	var buf bytes.Buffer
-	_, err := sig.WriteTo(&buf)
+	_, err := writeSignatureTo(&buf, sig)
 	if err != nil {
 		return ctx, fmt.Errorf("failed to serialize signature: %w", err)
 	}
@@ -410,12 +505,9 @@ func signatureReadFromIsCalledWithReader(ctx context.Context) (context.Context,
 	if !ok {
 		return ctx, fmt.Errorf("reader data is not a byte slice")
 	}
-	// Read signature using ReadFrom
-	sig := &novuspack.Signature{}
-	_, err := sig.ReadFrom(bytes.NewReader(buf))
+	sig, _, err := readSignatureFrom(bytes.NewReader(buf))
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
-		// Return nil to allow error scenarios to continue and check for the error
 		return ctx, nil
 	}
 	world.SetSignature(sig)
@@ -464,7 +556,7 @@ func signatureIsValid(ctx context.Context) error {
 	if sig == nil {
 		return fmt.Errorf("no signature available")
 	}
-	err := sig.Validate()
+	err := validateSignature(sig)
 	if err != nil {
 		world.SetError(wrapFileFormatError(err))
 		return fmt.Errorf("signature validation failed: %w", err)
diff --git a/api/go/_bdd/steps/file_mgmt/patterns.go b/api/go/_bdd/steps/file_mgmt/patterns.go
index 3c8e6642..a247d560 100644
--- a/api/go/_bdd/steps/file_mgmt/patterns.go
+++ b/api/go/_bdd/steps/file_mgmt/patterns.go
@@ -111,7 +111,7 @@ func RegisterFileMgmtPatterns(ctx *godog.ScenarioContext) {
 	ctx.Step(`^AddFilePath is called with new path$`, addFilePathIsCalledWithNewPath)
 	ctx.Step(`^AddFilePath is called with non-existent file$`, addFilePathIsCalledWithNonexistentFile)
 	ctx.Step(`^AddFilePath is called with path and metadata$`, addFilePathIsCalledWithPathAndMetadata)
-	ctx.Step(`^AddFilePattern encounters I\/O error$`, addFilePatternEncountersIOError)
+	ctx.Step(`^AddFilePattern encounters I/O error$`, addFilePatternEncountersIOError)
 	ctx.Step(`^AddFilePattern is called with context, pattern, and options$`, addFilePatternIsCalledWithContextPatternAndOptions)
 	ctx.Step(`^AddFilePattern is called with invalid pattern$`, addFilePatternIsCalledWithInvalidPattern)
 	ctx.Step(`^AddFilePattern is called with options$`, addFilePatternIsCalledWithOptions)
@@ -148,7 +148,7 @@ func RegisterFileMgmtPatterns(ctx *godog.ScenarioContext) {
 	ctx.Step(`^a target file path$`, aTargetFilePath)
 	ctx.Step(`^a target file path that does not exist$`, aTargetFilePathThatDoesNotExist)
 	ctx.Step(`^a target file path that exists$`, aTargetFilePathThatExists)
-	ctx.Step(`^a target file path with I\/O errors$`, aTargetFilePathWithIOErrors)
+	ctx.Step(`^a target file path with I/O errors$`, aTargetFilePathWithIOErrors)
 	ctx.Step(`^a new path string$`, aNewPathString)
 	ctx.Step(`^a non-existent file path$`, aNonexistentFilePath)
 	ctx.Step(`^a non-existent file identifier$`, aNonexistentFileIdentifier)
diff --git a/api/go/go.mod b/api/go/go.mod
index 4deded57..07756d07 100644
--- a/api/go/go.mod
+++ b/api/go/go.mod
@@ -6,8 +6,9 @@ replace github.com/novus-engine/novuspack => ../../..
 
 require (
 	github.com/cucumber/godog v0.15.1
-	github.com/goccy/go-yaml v1.15.13
+	github.com/goccy/go-yaml v1.19.2
 	github.com/samber/lo v1.52.0
+	golang.org/x/text v0.33.0
 )
 
 require (
@@ -18,5 +19,4 @@ require (
 	github.com/hashicorp/go-memdb v1.3.5 // indirect
 	github.com/hashicorp/golang-lru v1.0.2 // indirect
 	github.com/spf13/pflag v1.0.10 // indirect
-	golang.org/x/text v0.33.0 // indirect
 )
diff --git a/api/go/go.sum b/api/go/go.sum
index 0db7d064..b367fba7 100644
--- a/api/go/go.sum
+++ b/api/go/go.sum
@@ -9,8 +9,8 @@ github.com/cucumber/messages/go/v22 v22.0.0/go.mod h1:aZipXTKc0JnjCsXrJnuZpWhtay
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/goccy/go-yaml v1.15.13 h1:Xd87Yddmr2rC1SLLTm2MNDcTjeO/GYo0JGiww6gSTDg=
-github.com/goccy/go-yaml v1.15.13/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
+github.com/goccy/go-yaml v1.19.2 h1:PmFC1S6h8ljIz6gMRBopkjP1TVT7xuwrButHID66PoM=
+github.com/goccy/go-yaml v1.19.2/go.mod h1:XBurs7gK8ATbW4ZPGKgcbrY1Br56PdM69F7LkFRi1kA=
 github.com/gofrs/uuid v4.2.0+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
 github.com/gofrs/uuid v4.3.1+incompatible/go.mod h1:b2aQJv3Z4Fp6yNu3cdSllBxTCLRxnplIgP/c0N/04lM=
 github.com/gofrs/uuid v4.4.0+incompatible h1:3qXRTX8/NbyulANqlc0lchS1gqAVxRgsuW1YrTJupqA=
@@ -50,8 +50,6 @@ github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
 github.com/stretchr/testify v1.8.2/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-golang.org/x/text v0.22.0 h1:bofq7m3/HAFvbF51jz3Q9wLg3jkvSPuiZu/pD1XwgtM=
-golang.org/x/text v0.22.0/go.mod h1:YRoo4H8PVmsu+E3Ou7cqLVH8oXWIHVoX0jqUWALQhfY=
 golang.org/x/text v0.33.0 h1:B3njUFyqtHDUI5jMn1YIr5B0IE2U0qck04r6d4KPAxE=
 golang.org/x/text v0.33.0/go.mod h1:LuMebE6+rBincTi9+xWTY8TztLzKHc/9C1uBCG27+q8=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/api/go/novus_package/package_file_management.go b/api/go/novus_package/package_file_management.go
index 62ce348e..bb17372e 100644
--- a/api/go/novus_package/package_file_management.go
+++ b/api/go/novus_package/package_file_management.go
@@ -1011,6 +1011,7 @@ func (p *filePackage) captureFilesystemMetadata(storedPath string, fileInfo os.F
 			preserveOwnership = options.PreserveOwnership.GetOrDefault(false)
 		}
 		if preserveOwnership {
+			// FIXME: syscall.Stat_t is Unix-only; prevents cross-compiling for Windows (e.g. nvpkg build-windows-amd64). Use build tags or a Windows-specific path.
 			if sys, ok := fileInfo.Sys().(*syscall.Stat_t); ok {
 				uid := uint32(sys.Uid)
 				gid := uint32(sys.Gid)
diff --git a/api/go/novus_package/package_file_management_test.go b/api/go/novus_package/package_file_management_test.go
index 92b97b1f..8b53be8f 100644
--- a/api/go/novus_package/package_file_management_test.go
+++ b/api/go/novus_package/package_file_management_test.go
@@ -651,6 +651,172 @@ func TestRemoveFile_ErrorCases(t *testing.T) {
 	}, "RemoveFile")
 }
 
+// ====================
+// RemoveFilePattern (stub) Tests
+// ====================
+
+// TestRemoveFilePattern_ReturnsUnsupported tests that RemoveFilePattern returns ErrTypeUnsupported (stub).
+func TestRemoveFilePattern_ReturnsUnsupported(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	ctx := context.Background()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(ctx, tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	removed, err := pkg.RemoveFilePattern(ctx, "*.tmp")
+	if err == nil {
+		t.Fatal("RemoveFilePattern succeeded, want ErrTypeUnsupported")
+	}
+	if removed != nil {
+		t.Errorf("RemoveFilePattern returned %v, want nil slice", removed)
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeUnsupported {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeUnsupported)
+	}
+}
+
+// TestRemoveFilePattern_EmptyPattern tests validation error for empty pattern.
+func TestRemoveFilePattern_EmptyPattern(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	ctx := context.Background()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(ctx, tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	_, err = pkg.RemoveFilePattern(ctx, "")
+	if err == nil {
+		t.Fatal("RemoveFilePattern(empty) succeeded, want validation error")
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeValidation {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeValidation)
+	}
+}
+
+// TestRemoveFilePattern_ContextCancelled tests context cancellation.
+func TestRemoveFilePattern_ContextCancelled(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(context.Background(), tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, err = pkg.RemoveFilePattern(ctx, "*.tmp")
+	if err == nil {
+		t.Fatal("RemoveFilePattern with cancelled context succeeded, want error")
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeContext {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeContext)
+	}
+}
+
+// ====================
+// RemoveDirectory (stub) Tests
+// ====================
+
+// TestRemoveDirectory_ReturnsUnsupported tests that RemoveDirectory returns ErrTypeUnsupported (stub).
+func TestRemoveDirectory_ReturnsUnsupported(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	ctx := context.Background()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(ctx, tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	removed, err := pkg.RemoveDirectory(ctx, "/subdir/", nil)
+	if err == nil {
+		t.Fatal("RemoveDirectory succeeded, want ErrTypeUnsupported")
+	}
+	if removed != nil {
+		t.Errorf("RemoveDirectory returned %v, want nil slice", removed)
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeUnsupported {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeUnsupported)
+	}
+}
+
+// TestRemoveDirectory_EmptyPath tests validation error for empty path.
+func TestRemoveDirectory_EmptyPath(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	ctx := context.Background()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(ctx, tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	_, err = pkg.RemoveDirectory(ctx, "", nil)
+	if err == nil {
+		t.Fatal("RemoveDirectory(empty) succeeded, want validation error")
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeValidation {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeValidation)
+	}
+}
+
+// TestRemoveDirectory_ContextCancelled tests context cancellation.
+func TestRemoveDirectory_ContextCancelled(t *testing.T) {
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(context.Background(), tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, err = pkg.RemoveDirectory(ctx, "/dir/", nil)
+	if err == nil {
+		t.Fatal("RemoveDirectory with cancelled context succeeded, want error")
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeContext {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeContext)
+	}
+}
+
 // ====================
 // File Integration Tests
 // ====================
diff --git a/api/go/novus_package/package_writer_test.go b/api/go/novus_package/package_writer_test.go
index 6e2a159c..4cc90fdd 100644
--- a/api/go/novus_package/package_writer_test.go
+++ b/api/go/novus_package/package_writer_test.go
@@ -11,6 +11,8 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
+
+	"github.com/novus-engine/novuspack/api/go/pkgerrors"
 )
 
 func TestPackage_WriteFile(t *testing.T) {
@@ -166,12 +168,38 @@ func TestPackage_SafeWrite_RoundTrip(t *testing.T) {
 	}
 }
 
+// assertStubUnsupported runs fn on a created package and asserts ErrTypeUnsupported.
+func assertStubUnsupported(t *testing.T, name string, fn func(Package, context.Context) error) {
+	t.Helper()
+	pkg, err := NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage failed: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	ctx := context.Background()
+	tmpPath := filepath.Join(t.TempDir(), "pkg.nvpk")
+	if err := pkg.Create(ctx, tmpPath); err != nil {
+		t.Fatalf("Create failed: %v", err)
+	}
+	err = fn(pkg, ctx)
+	if err == nil {
+		t.Fatalf("%s succeeded, want ErrTypeUnsupported", name)
+	}
+	pkgErr, ok := err.(*pkgerrors.PackageError)
+	if !ok {
+		t.Fatalf("Error type = %T, want *pkgerrors.PackageError", err)
+	}
+	if pkgErr.Type != pkgerrors.ErrTypeUnsupported {
+		t.Errorf("Error type = %v, want %v", pkgErr.Type, pkgerrors.ErrTypeUnsupported)
+	}
+}
+
 func TestPackage_FastWrite(t *testing.T) {
-	t.Skip("TODO(Priority 5): FastWrite not implemented yet")
+	assertStubUnsupported(t, "FastWrite", func(pkg Package, ctx context.Context) error { return pkg.FastWrite(ctx) })
 }
 
 func TestPackage_Defragment(t *testing.T) {
-	t.Skip("TODO(Priority 2): Defragment implementation pending")
+	assertStubUnsupported(t, "Defragment", func(pkg Package, ctx context.Context) error { return pkg.Defragment(ctx) })
 }
 
 func TestPackage_WriteFile_InvalidPath(t *testing.T) {
diff --git a/cli/README.md b/cli/README.md
new file mode 100644
index 00000000..16d5b1c6
--- /dev/null
+++ b/cli/README.md
@@ -0,0 +1,53 @@
+# CLI Implementations
+
+## 1. Overview
+
+This directory holds language-specific CLI implementations for creating, inspecting, and modifying NovusPack (`.nvpk`) packages.
+Each subdirectory is a separate implementation; the binary name indicates the language.
+
+CLI tools in this directory are intended to be **functional implementations of the public API surface**.
+They should expose the same capabilities as the NovusPack API (create, inspect, modify, validate) in a way that is usable both from scripts and from an interactive session.
+
+## 2. Purpose and Requirements
+
+High level purpose and requirements.
+Use as a loose guideline until more formal requirements have been defined for a given implementation.
+
+### 2.1 Dual Modality
+
+CLI implementations must support:
+
+- **Command-based usage:** Every capability is invokable as a subcommand (e.g. `nvpkg create`, `nvpkg add`, `nvpkg list`) so that scripts and automation can drive the tool without user interaction.
+- **Interactive usage:** A REPL (read-eval-print loop) mode where a user opens a package once and then runs list, add, remove, read, etc. without repeating the package path; changes can be batched in memory and written with a single `write` (or equivalent).
+
+All API functionality that is relevant to package creation, inspection, modification, and validation should be available in both modes.
+
+### 2.2 High-Level Capabilities (from API Surface)
+
+Implementations are expected to cover at least the following, in both command and interactive form where applicable:
+
+- **Create** – Create a new empty package (`create <path>` with optional flags).
+- **Info** – Show package metadata and summary (`info <path>`).
+- **List** – List package contents – paths, sizes (`list <path>`).
+- **Add** – Add files or directories (`add <path> <sources>...`).
+- **Remove** – Remove a file, directory, or pattern (`remove <path> <entry>`).
+- **Read** – Read a file to stdout or file (`read <path> <internal>`).
+- **Extract** – Extract all or a subtree to a directory (`extract <path> [-o dir]`).
+- **Header** – Print raw package header (`header <path>`).
+- **Validate** – Validate package integrity (`validate <path>`).
+- **Comment** – Get or set package comment (`comment` get/set/clear).
+- **Identity** – Get or set Vendor ID / App ID (`identity` get/set).
+- **Metadata** – Show or manipulate package metadata (`metadata <path>`).
+- **Interactive** – REPL: open/write, pwd/cd/ls, and all above (`interactive` / `i`).
+
+Exact subcommand names and flags may vary by implementation; the list reflects the current Go CLI (nvpkg) as the reference.
+
+## 3. Implementations
+
+| Binary | Language | Directory        | README / Description                                  |
+| ------ | -------- | ---------------- | ----------------------------------------------------- |
+| nvpkg  | Go       | [nvpkg/](nvpkg/) | [nvpkg/README.md](nvpkg/README.md) – Cobra-based CLI. |
+| nvpkr  | Rust     | (planned)        | Rust implementation.                                  |
+| nvpkz  | Zig      | (planned)        | Zig implementation.                                   |
+
+Additional language implementations may be added under their own subdirectories with corresponding binary names and a README that describes build, commands, and how they map to the API.
diff --git a/cli/nvpkg/.gitignore b/cli/nvpkg/.gitignore
new file mode 100644
index 00000000..09dd484b
--- /dev/null
+++ b/cli/nvpkg/.gitignore
@@ -0,0 +1,9 @@
+dist/
+nvpkg
+nvpkg.exe
+nvpkg-dev
+nvpkg-dev.exe
+nvpkg.upx
+nvpkg.lvl*
+coverage.out
+coverage.html
diff --git a/cli/nvpkg/.golangci.yml b/cli/nvpkg/.golangci.yml
new file mode 100644
index 00000000..a3688f3c
--- /dev/null
+++ b/cli/nvpkg/.golangci.yml
@@ -0,0 +1,32 @@
+# golangci-lint configuration
+# Matches api/go strategy: contextcheck, dupl, gocyclo, gocritic, goconst, gocognit.
+# Ensures context propagation and code quality standards.
+
+version: "2"
+
+linters:
+  enable:
+    - contextcheck
+    - dupl          # Code duplication detection
+    - gocyclo       # Cyclomatic complexity
+    - gocritic      # Code critique and code smells
+    - goconst       # Constant usage
+    - gocognit      # Cognitive complexity
+  settings:
+    dupl:
+      threshold: 50
+    gocyclo:
+      min-complexity: 15
+    gocritic:
+      enabled-tags:
+        - diagnostic
+        - experimental
+        - opinionated
+        - performance
+        - style
+      disabled-checks:
+        - dupImport
+    goconst:
+      min-len: 3
+    gocognit:
+      min-complexity: 15
diff --git a/cli/nvpkg/Makefile b/cli/nvpkg/Makefile
new file mode 100644
index 00000000..2932aa58
--- /dev/null
+++ b/cli/nvpkg/Makefile
@@ -0,0 +1,187 @@
+# Makefile for nvpkg CLI
+# Follows conventions of root Makefile and api/go/Makefile.
+# Unit tests target 90%% code coverage.
+
+# Ensure MAKE is set to the actual make binary for recursive calls
+SYSTEM_MAKE := $(shell PATH="/usr/bin:/usr/local/bin:/bin:$$PATH" command -v make 2>/dev/null || echo /usr/bin/make)
+ifneq ($(MAKE),$(SYSTEM_MAKE))
+  override MAKE := $(SYSTEM_MAKE)
+endif
+
+.PHONY: test tidy coverage coverage-90 coverage-html coverage-report lint ci build build-dev clean
+.PHONY: build-all build-linux-amd64 build-linux-arm64 build-darwin-amd64 build-darwin-arm64 build-windows-amd64 build-freebsd-amd64 build-freebsd-arm64
+
+# Default minimum 82%%; use make coverage-90 to require 90%% (target)
+COVERAGE_MIN ?= 82
+TMP_DIR ?= ../../tmp
+OUT_DIR ?= dist
+LDFLAGS_RELEASE := -ldflags="-s -w"
+
+# Run all unit tests
+test:
+	@if ( [ -w "$(HOME)/.cache/go-build" ] 2>/dev/null && touch "$(HOME)/.cache/go-build/.write-test" 2>/dev/null && rm -f "$(HOME)/.cache/go-build/.write-test" ) || [ -z "$(HOME)" ]; then \
+		go test -v ./...; \
+	else \
+		mkdir -p $(TMP_DIR)/go-cache; \
+		GOCACHE="$$(cd $(TMP_DIR) && pwd)/go-cache" go test -v ./...; \
+	fi
+
+# Run tests with coverage; fail if cmd coverage below COVERAGE_MIN (default 90%%).
+# Only ./cmd is measured so main package does not lower the total.
+coverage:
+	@echo "Running tests with coverage (minimum $(COVERAGE_MIN)%% for cmd)..."
+	@go clean -testcache
+	@go test -coverprofile=coverage.out -coverpkg=./cmd ./cmd/...
+	@echo ""
+	@TOTAL=$$(go tool cover -func=coverage.out | awk '/total:/{gsub(/%/,""); print $$NF}'); \
+	if [ -z "$$TOTAL" ]; then echo "Error: could not parse coverage total"; exit 1; fi; \
+	if ! echo "$$TOTAL $(COVERAGE_MIN)" | awk '{exit !($$1>=$$2)}'; then \
+		echo "Coverage $$TOTAL%% is below minimum $(COVERAGE_MIN)%%"; \
+		go tool cover -func=coverage.out | grep "total:"; \
+		exit 1; \
+	fi; \
+	echo "Coverage $$TOTAL%% meets minimum $(COVERAGE_MIN)%%"; \
+	echo "Coverage profile saved to: coverage.out"
+
+# Require 90%% coverage (target); fails until api path metadata write is complete
+coverage-90:
+	@$(MAKE) coverage COVERAGE_MIN=90
+
+# Generate HTML coverage report
+coverage-html: coverage
+	@echo "Generating HTML coverage report..."
+	@go tool cover -html=coverage.out -o coverage.html
+	@echo "Coverage report saved to: coverage.html"
+	@if command -v xdg-open >/dev/null 2>&1; then \
+		xdg-open coverage.html; \
+	elif command -v open >/dev/null 2>&1; then \
+		open coverage.html; \
+	else \
+		echo "Open coverage.html in your browser to view the report"; \
+	fi
+
+# Display coverage report in terminal
+coverage-report: coverage
+	@echo "=== Coverage Report ==="
+	@go tool cover -func=coverage.out
+	@echo ""
+	@echo "=== Total ==="
+	@go tool cover -func=coverage.out | grep "total:" || echo "Coverage data not available"
+
+# Tidy dependencies
+tidy:
+	@echo "Running go mod tidy..."
+	@go mod tidy
+	@echo "Dependencies tidied successfully."
+
+# Lint: gofmt, go vet, golangci-lint (same strategy as api/go; uses .golangci.yml)
+# Use latest golangci-lint so local and CI (.github/workflows/nvpkg-ci.yml) stay in sync.
+GOLANGCI_LINT_VERSION ?= latest
+GOLANGCI_LINT := go run github.com/golangci/golangci-lint/v2/cmd/golangci-lint@$(GOLANGCI_LINT_VERSION)
+
+lint:
+	@echo "Checking code formatting..."
+	@if [ "$$(gofmt -s -l . | wc -l)" -gt 0 ]; then \
+		echo "Code is not formatted. Run 'go fmt ./...'"; \
+		gofmt -s -d .; \
+		exit 1; \
+	fi
+	@echo ""
+	@echo "Running go vet..."
+	@go vet ./...
+	@echo ""
+	@echo "Running golangci-lint $(GOLANGCI_LINT_VERSION)..."
+	@$(GOLANGCI_LINT) run ./...
+
+# Native release build for current OS/arch only. Outputs to $(OUT_DIR)/<goos>-<goarch>/nvpkg (or nvpkg.exe on Windows).
+BUILD_GOOS := $(shell go env GOOS)
+BUILD_GOARCH := $(shell go env GOARCH)
+BUILD_PLATFORM := $(BUILD_GOOS)-$(BUILD_GOARCH)
+BUILD_BINARY := nvpkg$(if $(filter windows,$(BUILD_GOOS)),.exe,)
+
+build:
+	@mkdir -p $(OUT_DIR)/$(BUILD_PLATFORM)
+	@rm -f $(OUT_DIR)/$(BUILD_PLATFORM)/$(BUILD_BINARY)
+	@CGO_ENABLED=0 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/$(BUILD_PLATFORM)/$(BUILD_BINARY) .
+	$(call run_upx,$(OUT_DIR)/$(BUILD_PLATFORM)/$(BUILD_BINARY))
+	@echo "Built: $(CURDIR)/$(OUT_DIR)/$(BUILD_PLATFORM)/$(BUILD_BINARY)"
+
+# Cross-platform release builds for all supported platforms. Outputs to $(OUT_DIR)/<platform>/nvpkg (or nvpkg.exe on Windows).
+build-all: build-linux-amd64 build-linux-arm64 build-darwin-amd64 build-darwin-arm64 build-windows-amd64 build-freebsd-amd64 build-freebsd-arm64
+	@echo "Built binaries:"
+	@echo "  $(CURDIR)/$(OUT_DIR)/linux-amd64/nvpkg"
+	@echo "  $(CURDIR)/$(OUT_DIR)/linux-arm64/nvpkg"
+	@echo "  $(CURDIR)/$(OUT_DIR)/darwin-amd64/nvpkg"
+	@echo "  $(CURDIR)/$(OUT_DIR)/darwin-arm64/nvpkg"
+	@echo "  $(CURDIR)/$(OUT_DIR)/windows-amd64/nvpkg.exe"
+	@echo "  $(CURDIR)/$(OUT_DIR)/freebsd-amd64/nvpkg"
+	@echo "  $(CURDIR)/$(OUT_DIR)/freebsd-arm64/nvpkg"
+
+# After build: UPX (required for release). Go -ldflags="-s -w" already omits symbols.
+# Tolerate AlreadyPackedException (exit 2) so re-runs of build/ci succeed.
+define run_upx
+	@if command -v upx >/dev/null 2>&1; then upx --best $(1) || { r=$$?; [ $$r -eq 2 ] && exit 0; exit $$r; }; else echo "upx not found: install upx (e.g. apt install upx-ucl) for release builds"; exit 1; fi
+endef
+
+build-linux-amd64:
+	@mkdir -p $(OUT_DIR)/linux-amd64
+	@CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/linux-amd64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/linux-amd64/nvpkg)
+
+build-linux-arm64:
+	@mkdir -p $(OUT_DIR)/linux-arm64
+	@CGO_ENABLED=0 GOOS=linux GOARCH=arm64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/linux-arm64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/linux-arm64/nvpkg)
+
+build-darwin-amd64:
+	@mkdir -p $(OUT_DIR)/darwin-amd64
+	@CGO_ENABLED=0 GOOS=darwin GOARCH=amd64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/darwin-amd64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/darwin-amd64/nvpkg)
+
+build-darwin-arm64:
+	@mkdir -p $(OUT_DIR)/darwin-arm64
+	@CGO_ENABLED=0 GOOS=darwin GOARCH=arm64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/darwin-arm64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/darwin-arm64/nvpkg)
+
+build-freebsd-amd64:
+	@mkdir -p $(OUT_DIR)/freebsd-amd64
+	@CGO_ENABLED=0 GOOS=freebsd GOARCH=amd64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/freebsd-amd64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/freebsd-amd64/nvpkg)
+
+build-freebsd-arm64:
+	@mkdir -p $(OUT_DIR)/freebsd-arm64
+	@CGO_ENABLED=0 GOOS=freebsd GOARCH=arm64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/freebsd-arm64/nvpkg .
+	$(call run_upx,$(OUT_DIR)/freebsd-arm64/nvpkg)
+
+# Windows build requires api/go to be Windows-compatible (e.g. no Unix-only syscalls).
+# Currently not supported until api/go is Windows-compatible.
+build-windows-amd64:
+	@mkdir -p $(OUT_DIR)/windows-amd64
+	@CGO_ENABLED=0 GOOS=windows GOARCH=amd64 go build $(LDFLAGS_RELEASE) -trimpath -o $(OUT_DIR)/windows-amd64/nvpkg.exe .
+	$(call run_upx,$(OUT_DIR)/windows-amd64/nvpkg.exe)
+
+# Build development binary with debug symbols (for debugging and stack traces)
+build-dev:
+	@go build -o nvpkg-dev .
+
+# CI: verify, test, build, lint
+ci: tidy
+	@echo "Running CI checks..."
+	@echo ""
+	@echo "1. Verifying dependencies..."
+	@go mod verify
+	@echo ""
+	@echo "2. Running unit tests with coverage..."
+	@$(MAKE) coverage
+	@echo ""
+	@echo "3. Building..."
+	@$(MAKE) build
+	@echo ""
+	@echo "4. Linting..."
+	@$(MAKE) lint
+	@echo "CI checks passed."
+
+# Remove build and coverage artifacts
+clean:
+	@rm -rf $(OUT_DIR)
+	@rm -f nvpkg nvpkg.exe nvpkg-dev nvpkg-dev.exe coverage.out coverage.html
diff --git a/cli/nvpkg/README.md b/cli/nvpkg/README.md
new file mode 100644
index 00000000..70994689
--- /dev/null
+++ b/cli/nvpkg/README.md
@@ -0,0 +1,402 @@
+# nvpkg
+
+## 1. Overview
+
+nvpkg is a command-line tool for creating, inspecting, and modifying NovusPack (`.nvpk`) packages.
+It is built with [Cobra](https://github.com/spf13/cobra) and uses the [NovusPack Go API](../../api/go/README.md) as its only project dependency.
+
+The CLI supports creating empty packages, adding files or directories, listing contents, reading or extracting files from a package, removing entries, and inspecting package headers.
+
+## 2. Requirements
+
+- Go 1.25 or later
+- The [api/go](../../api/go/) module (satisfied via `replace` in [go.mod](go.mod) when building from this repository)
+
+## 3. Installation and Build
+
+Build the binary from the `nvpkg` directory or from the repository root.
+
+### 3.1 Build from Source
+
+From the `nvpkg` directory:
+
+#### 3.1.1 Release Build (Smallest Size; Requires [UPX](https://upx.github.io/) on PATH)
+
+```bash
+make build
+```
+
+Output: `nvpkg` (or `nvpkg.exe` on Windows).
+Uses `CGO_ENABLED=0`, `-ldflags="-s -w"`, `-trimpath`, then `upx --best`.
+Install UPX if needed (e.g. `apt install upx-ucl`).
+
+#### 3.1.2 Development Build (with Debug Symbols, for Debugging and Stack Traces)
+
+```bash
+make build-dev
+```
+
+Output: `nvpkg-dev` (or `nvpkg-dev.exe` on Windows).
+
+### 3.2 Build from Repository Root
+
+From the repository root:
+
+```bash
+make build-nvpkg     # release binary (nvpkg; requires upx)
+make build-dev-nvpkg # development binary (nvpkg-dev)
+```
+
+## 4. Commands and Usage
+
+All commands take a package path (path to a `.nvpk` file) where applicable.
+Internal paths inside a package use a leading slash (e.g. `/config.json`).
+
+### 4.1 Global Help
+
+```bash
+./nvpkg --help
+./nvpkg <command> --help
+```
+
+### 4.2 Create
+
+Create a new empty NovusPack package at the given path.
+The file is written immediately; the package contains no entries until you add them with `add`.
+
+Usage:
+
+```text
+nvpkg create <package path> [flags]
+```
+
+Flags:
+
+| Flag          | Type   | Description     |
+| ------------- | ------ | --------------- |
+| `--comment`   | string | Package comment |
+| `--vendor-id` | uint32 | Vendor ID       |
+| `--app-id`    | uint64 | Application ID  |
+
+Examples:
+
+```bash
+./nvpkg create myapp.nvpk
+./nvpkg create myapp.nvpk --comment "My application assets"
+./nvpkg create myapp.nvpk --vendor-id 1 --app-id 100
+```
+
+### 4.3 Info
+
+Show metadata and summary for an existing package (file count, sizes, Vendor ID/App ID when set, comment if set).
+
+Usage:
+
+```text
+nvpkg info <package path>
+```
+
+Example:
+
+```bash
+./nvpkg info myapp.nvpk
+```
+
+### 4.4 List
+
+List all files in a package.
+Output is one line per file: display path, size, stored size.
+
+Usage:
+
+```text
+nvpkg list <package path>
+```
+
+Example:
+
+```bash
+./nvpkg list myapp.nvpk
+```
+
+### 4.5 Add
+
+Add files or directories to a package.
+If the package path does not exist, a new package is created and then the sources are added.
+If it exists, the package is opened and the sources are added.
+After adding, the package is written to disk.
+
+Usage:
+
+```text
+nvpkg add <package path> <file or dir> [file or dir ...] [flags]
+```
+
+Flags:
+
+| Flag   | Type   | Description                              |
+| ------ | ------ | ---------------------------------------- |
+| `--as` | string | Store under this path (single file only) |
+
+Examples:
+
+```bash
+./nvpkg add myapp.nvpk config.json
+./nvpkg add myapp.nvpk config.json --as /config/app.json
+./nvpkg add myapp.nvpk ./assets ./data
+```
+
+### 4.6 Remove
+
+Remove a file, a directory (all files under a path), or files matching a pattern from a package.
+The package is written back to disk after the removal.
+
+Usage:
+
+```text
+nvpkg remove <package path> <internal path or pattern> [flags]
+```
+
+Flags:
+
+| Flag        | Description                                            |
+| ----------- | ------------------------------------------------------ |
+| `--pattern` | Treat second argument as a glob pattern (e.g. `*.tmp`) |
+
+- Single file: `remove <pkg> /path/to/file`
+- Directory (path ending with `/`): `remove <pkg> /path/to/dir/` removes all files under that path
+- Pattern: `remove <pkg> "*.tmp" --pattern`
+
+Examples:
+
+```bash
+./nvpkg remove myapp.nvpk /config/old.json
+./nvpkg remove myapp.nvpk /cache/
+./nvpkg remove myapp.nvpk "*.tmp" --pattern
+```
+
+### 4.7 Read
+
+Read a file from a package by its internal path.
+Output goes to stdout unless `--output` / `-o` is set.
+
+Usage:
+
+```text
+nvpkg read <package path> <internal path> [flags]
+```
+
+Flags:
+
+| Flag             | Type   | Description                     |
+| ---------------- | ------ | ------------------------------- |
+| `-o`, `--output` | string | Write to file instead of stdout |
+
+Examples:
+
+```bash
+./nvpkg read myapp.nvpk /config.json
+./nvpkg read myapp.nvpk /config.json -o config.json
+```
+
+### 4.8 Extract
+
+Extract all or a subtree of files from a package to a directory.
+Without an internal path, extracts every file.
+With an internal path (e.g. `/docs`), extracts only that file or directory subtree.
+
+Usage:
+
+```text
+nvpkg extract <package path> [internal path] [flags]
+```
+
+Flags:
+
+| Flag             | Type   | Description                          |
+| ---------------- | ------ | ------------------------------------ |
+| `-o`, `--output` | string | Directory to extract into (required) |
+
+Examples:
+
+```bash
+./nvpkg extract myapp.nvpk -o ./out
+./nvpkg extract myapp.nvpk /docs -o ./docs
+```
+
+### 4.9 Header
+
+Print the raw package header (magic, format version, index start, flags).
+Does not open the full package; only reads the header from disk.
+
+Usage:
+
+```text
+nvpkg header <package path>
+```
+
+Example:
+
+```bash
+./nvpkg header myapp.nvpk
+```
+
+### 4.10 Validate
+
+Validate package integrity (header, index, and optional content checks).
+
+Usage:
+
+```text
+nvpkg validate <package path>
+```
+
+Example:
+
+```bash
+./nvpkg validate myapp.nvpk
+```
+
+### 4.11 Interactive
+
+Run nvpkg in a read-eval-print loop (REPL).
+Use `open <path>` to set the current package; then `list`, `add`, `remove`, and `read` use that path without repeating it.
+Package changes (add, remove) stay in-memory until you run `write`; only `write` persists to disk.
+A current working directory (cwd) is maintained; `pwd`, `cd`, and `ls` navigate the local filesystem.
+Paths support `~` for home (e.g. `open ~/pkg.nvpk`, `cd ~`).
+Add takes sources first and optional package path last when no package is open (e.g. `add f1 f2 pkg.nvpk`).
+Use `--as <internal path>` when adding a single file to set its path inside the package.
+Paths given to `add` are resolved against cwd when relative.
+Up/down arrow in interactive mode browses command history.
+Tab completes command names and, for `open`, `cd`, `ls`, `create`, and `add`, completes paths from the current working directory.
+Use `validate` to check package integrity; `help` for in-session commands, `quit` or `exit` to leave.
+
+Usage:
+
+```text
+nvpkg interactive
+nvpkg i
+```
+
+In-session commands:
+
+| Command                          | Description                                                                   |
+| -------------------------------- | ----------------------------------------------------------------------------- |
+| `open <path>`                    | Set current package (opens and keeps in memory)                               |
+| `close`                          | Clear current package (closes without writing)                                |
+| `write`                          | Persist current package to disk (changes stay in-memory until write)          |
+| `pwd`                            | Print current working directory                                               |
+| `cd [dir]`                       | Change directory (no arg => home)                                             |
+| `ls [dir]`                       | List local dir: size, mod date, name (default: cwd)                           |
+| `create <path>`                  | Create empty package (flags: `--comment`, etc.)                               |
+| `info [path]`                    | Show package info (path optional if open)                                     |
+| `list [path]`                    | List contents (path optional if open)                                         |
+| `header [path]`                  | Print raw header (path optional if open)                                      |
+| `add [src]... [path]`            | Add file(s)/dir(s); path optional if package open; `--as <path>` for one file |
+| `remove [path] <internal path>`  | Remove entry                                                                  |
+| `read [path] <internal path>`    | Read file; `-o file` to write to file                                         |
+| `extract [path] [internal path]` | Extract all or subtree; `-o dir` required                                     |
+| `help`                           | Show in-session help                                                          |
+| `quit`, `exit`, `q`              | Exit                                                                          |
+
+Example:
+
+```bash
+./nvpkg interactive
+nvpkg> pwd
+/home/user/project
+nvpkg> ls
+assets/
+config.json
+nvpkg> open myapp.nvpk
+Current package: myapp.nvpk
+nvpkg [myapp.nvpk]> add config.json
+nvpkg [myapp.nvpk]> list
+/config.json  42  40
+nvpkg [myapp.nvpk]> quit
+```
+
+## 5. Make Targets
+
+The [Makefile](Makefile) provides the same conventions as the root and [api/go](../../api/go/Makefile) Makefiles.
+
+| Target                 | Description                                                               |
+| ---------------------- | ------------------------------------------------------------------------- |
+| `make test`            | Run all unit tests                                                        |
+| `make coverage`        | Run tests with coverage; fail if cmd coverage below COVERAGE_MIN (82%)    |
+| `make coverage-90`     | Same as coverage with 90% minimum                                         |
+| `make coverage-html`   | Generate HTML coverage report                                             |
+| `make coverage-report` | Print coverage summary to the terminal                                    |
+| `make lint`            | Run gofmt, go vet, and golangci-lint (see [.golangci.yml](.golangci.yml)) |
+| `make build`           | Build release binary: ldflags -s -w + UPX --best (nvpkg; requires upx)    |
+| `make build-dev`       | Build development binary with debug symbols (nvpkg-dev)                   |
+| `make ci`              | Run tidy, verify, coverage, build, and lint                               |
+| `make tidy`            | Run go mod tidy                                                           |
+| `make clean`           | Remove binaries (nvpkg, nvpkg-dev) and coverage artifacts                 |
+
+From the repository root you can run `make test-nvpkg`, `make ci-nvpkg`, `make lint-nvpkg`, `make coverage-nvpkg`, `make build-nvpkg`, `make build-dev-nvpkg`, and related targets that delegate into this directory.
+
+## 6. Functionality Scripts
+
+The [scripts/](scripts/) directory contains bash scripts that exercise the CLI.
+
+| Script                                                   | Purpose                                            |
+| -------------------------------------------------------- | -------------------------------------------------- |
+| [run_all.sh](scripts/run_all.sh)                         | Run all checks (requires built nvpkg or NVPKG set) |
+| [check_create.sh](scripts/check_create.sh)               | Create empty package and run info                  |
+| [check_header_info.sh](scripts/check_header_info.sh)     | Create package and run header and info             |
+| [check_add_list_read.sh](scripts/check_add_list_read.sh) | Add file, list, read (skips if add fails)          |
+| [check_remove.sh](scripts/check_remove.sh)               | Add file, remove it, list (skips if add fails)     |
+
+Temporary files are written under the repository `tmp/` directory.
+Set `NVPKG` to the path of the binary if it is not at `../nvpkg` relative to the script directory.
+
+## 7. Testing and Coverage
+
+Unit tests live in [cmd/](cmd/) with the pattern `*_test.go`.
+Coverage is measured only for the `cmd` package; the minimum is enforced by `make coverage` (default 82%, target 90% once the API path-metadata write is complete).
+
+Run tests:
+
+```bash
+make test
+```
+
+Run tests with coverage and enforce minimum:
+
+```bash
+make coverage
+```
+
+### 7.1 TTY test harness (pty)
+
+Interactive mode uses two code paths:
+
+- **Non-TTY (tests):** When `InteractiveStdin` is set (e.g. by tests), the REPL uses a `bufio.Scanner` over that reader. Most tests use this path.
+- **TTY:** When `InteractiveStdin` is nil, the REPL uses `runInteractiveWithLiner`, which uses [liner](https://github.com/peterh/liner) for readline-style history and completion. That path is only hit when stdin is a real terminal.
+
+**TestRunInteractive_WithPty** exercises the TTY path by running `nvpkg interactive` in a **subprocess** with a pseudoterminal ([github.com/creack/pty](https://github.com/creack/pty)):
+
+1. The test starts `go run . interactive` with stdin/stdout/stderr attached to the pty slave.
+2. The child process sees a TTY and uses `runInteractiveWithLiner`.
+3. The test writes scripted input to the pty master (`help\n`, `quit\n`) and reads output from the master.
+4. It asserts the output contains the prompt and help text.
+
+The test is skipped on Windows and when pty is unsupported. Because the liner path runs in the child process, it does not increase coverage of the test binary; it validates that the TTY path works when run with a real pty.
+
+## 8. Linting
+
+Linting follows the same strategy as [api/go](../../api/go/): gofmt, go vet, and golangci-lint with [.golangci.yml](.golangci.yml).
+Enabled linters include contextcheck, dupl, gocyclo, gocritic, goconst, and gocognit.
+
+Run lint:
+
+```bash
+make lint
+```
+
+## 9. Related Documentation
+
+- [api/go README](../../api/go/README.md) – NovusPack Go API used by nvpkg
+- [Root Makefile](../../Makefile) – Repository-wide targets including nvpkg
+- [.github/copilot-instructions.md](../../.github/copilot-instructions.md) – Project and markdown standards
diff --git a/cli/nvpkg/cmd/add.go b/cli/nvpkg/cmd/add.go
new file mode 100644
index 00000000..a6aaa135
--- /dev/null
+++ b/cli/nvpkg/cmd/add.go
@@ -0,0 +1,201 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strconv"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var addCmd = &cobra.Command{
+	Use:   "add <package path> <file or dir> [file or dir ...]",
+	Short: "Add files or directories to a NovusPack package",
+	Args:  cobra.MinimumNArgs(2),
+	RunE:  runAdd,
+}
+
+var (
+	addStoredPath          string
+	addBasePath            string
+	addPreserveDepth       int
+	addFlatten             bool
+	addNoFollowSymlinks    bool
+	addPreservePermissions bool
+	addPreserveOwnership   bool
+)
+
+func init() {
+	addCmd.Flags().StringVar(&addStoredPath, "as", "", "Store under this path (single file only)")
+	addCmd.Flags().StringVar(&addBasePath, "base-path", "", "Strip this prefix from source paths (at most one of --as, --base-path, --preserve-depth, --flatten)")
+	addCmd.Flags().IntVar(&addPreserveDepth, "preserve-depth", 0, "Keep N directory levels from source (0=off)")
+	addCmd.Flags().BoolVar(&addFlatten, "flatten", false, "Store all files at package root")
+	addCmd.Flags().BoolVar(&addNoFollowSymlinks, "no-follow-symlinks", false, "Do not follow symlinks; reject them")
+	addCmd.Flags().BoolVar(&addPreservePermissions, "preserve-permissions", false, "Store Unix permission bits")
+	addCmd.Flags().BoolVar(&addPreserveOwnership, "preserve-ownership", false, "Store UID/GID (implies --preserve-permissions)")
+}
+
+func runAdd(_ *cobra.Command, args []string) error {
+	ctx := context.Background()
+	pkgPath := args[0]
+	sources := args[1:]
+
+	pkg, err := openOrCreatePackage(ctx, pkgPath)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = pkg.Close() }()
+
+	opts, err := buildAddFileOptions(nil)
+	if err != nil {
+		return err
+	}
+	if err := addSources(ctx, pkg, sources, opts); err != nil {
+		return err
+	}
+	if err := pkg.Write(ctx); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "Added %d item(s) to %s\n", len(sources), pkgPath)
+	return nil
+}
+
+func openOrCreatePackage(ctx context.Context, pkgPath string) (novuspack.Package, error) {
+	if _, statErr := os.Stat(pkgPath); statErr != nil && os.IsNotExist(statErr) {
+		pkg, err := novuspack.NewPackage()
+		if err != nil {
+			return nil, fmt.Errorf("new package: %w", err)
+		}
+		if err := pkg.Create(ctx, pkgPath); err != nil {
+			_ = pkg.Close()
+			return nil, fmt.Errorf("create: %w", err)
+		}
+		return pkg, nil
+	}
+	return openPackage(ctx, pkgPath, false)
+}
+
+// openPackage opens an existing package, optionally read-only. Used by list, read, info, extract, validate.
+func openPackage(ctx context.Context, path string, readOnly bool) (novuspack.Package, error) {
+	if readOnly {
+		return novuspack.OpenPackageReadOnly(ctx, path)
+	}
+	return novuspack.OpenPackage(ctx, path)
+}
+
+const (
+	flagTrue = "true"
+	flagYes  = "yes"
+)
+
+// flagBool returns true if v is a truthy flag value (e.g. "1", "true", "yes").
+func flagBool(v string) bool {
+	return v == "1" || v == flagTrue || v == flagYes
+}
+
+// buildAddFileOptions builds AddFileOptions from package vars (when flags is nil) or from interactive flags map.
+// At most one of StoredPath, BasePath, PreserveDepth, FlattenPaths may be set.
+func buildAddFileOptions(flags map[string]string) (*novuspack.AddFileOptions, error) {
+	opts := &novuspack.AddFileOptions{}
+	var pathOptCount int
+	var err error
+	if flags != nil {
+		pathOptCount, err = applyAddFileOptionsFromFlags(flags, opts)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		pathOptCount = applyAddFileOptionsFromVars(opts)
+	}
+	if pathOptCount > 1 {
+		return nil, fmt.Errorf("at most one of --as, --base-path, --preserve-depth, --flatten may be set")
+	}
+	return opts, nil
+}
+
+func applyAddFileOptionsFromFlags(flags map[string]string, opts *novuspack.AddFileOptions) (int, error) {
+	var n int
+	if v := flags["as"]; v != "" {
+		opts.StoredPath.Set(v)
+		n++
+	}
+	if v := flags["base-path"]; v != "" {
+		opts.BasePath.Set(v)
+		n++
+	}
+	if v := flags["preserve-depth"]; v != "" {
+		d, err := strconv.Atoi(v)
+		if err != nil || d < 0 {
+			return 0, fmt.Errorf("invalid --preserve-depth: %s", v)
+		}
+		opts.PreserveDepth.Set(d)
+		n++
+	}
+	if flagBool(flags["flatten"]) {
+		opts.FlattenPaths.Set(true)
+		n++
+	}
+	if flagBool(flags["no-follow-symlinks"]) {
+		opts.FollowSymlinks.Set(false)
+	}
+	if flagBool(flags["preserve-permissions"]) {
+		opts.PreservePermissions.Set(true)
+	}
+	if flagBool(flags["preserve-ownership"]) {
+		opts.PreserveOwnership.Set(true)
+	}
+	return n, nil
+}
+
+func applyAddFileOptionsFromVars(opts *novuspack.AddFileOptions) int {
+	var n int
+	if addStoredPath != "" {
+		opts.StoredPath.Set(addStoredPath)
+		n++
+	}
+	if addBasePath != "" {
+		opts.BasePath.Set(addBasePath)
+		n++
+	}
+	if addPreserveDepth > 0 {
+		opts.PreserveDepth.Set(addPreserveDepth)
+		n++
+	}
+	if addFlatten {
+		opts.FlattenPaths.Set(true)
+		n++
+	}
+	if addNoFollowSymlinks {
+		opts.FollowSymlinks.Set(false)
+	}
+	if addPreservePermissions {
+		opts.PreservePermissions.Set(true)
+	}
+	if addPreserveOwnership {
+		opts.PreserveOwnership.Set(true)
+	}
+	return n
+}
+
+func addSources(ctx context.Context, pkg novuspack.Package, sources []string, opts *novuspack.AddFileOptions) error {
+	for _, src := range sources {
+		info, err := os.Stat(src)
+		if err != nil {
+			return fmt.Errorf("stat %s: %w", src, err)
+		}
+		if info.IsDir() {
+			_, err = pkg.AddDirectory(ctx, src, opts)
+			if err != nil {
+				return fmt.Errorf("add directory %s: %w", src, err)
+			}
+		} else {
+			_, err = pkg.AddFile(ctx, src, opts)
+			if err != nil {
+				return fmt.Errorf("add file %s: %w", src, err)
+			}
+		}
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/add_test.go b/cli/nvpkg/cmd/add_test.go
new file mode 100644
index 00000000..503b7b2e
--- /dev/null
+++ b/cli/nvpkg/cmd/add_test.go
@@ -0,0 +1,114 @@
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestRunAdd_SourceNotFound(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "pkg.nvpk")
+	if err := runCreate(createCmd, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	err := runAdd(addCmd, []string{pkgPath, filepath.Join(dir, "nonexistent.txt")})
+	if err == nil {
+		t.Error("runAdd with missing source should fail")
+	}
+}
+
+func TestRunAdd_PackageNotExist_CreatePath(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "newpkg.nvpk")
+	srcPath := filepath.Join(dir, "src.txt")
+	if err := os.WriteFile(srcPath, []byte("data"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	err := runAdd(addCmd, []string{pkgPath, srcPath})
+	if err != nil {
+		t.Fatalf("runAdd (create new package): %v", err)
+	}
+	if _, err := os.Stat(pkgPath); os.IsNotExist(err) {
+		t.Error("package file was not created")
+	}
+}
+
+func TestRunAdd_OpenExisting(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "existing.nvpk")
+	srcPath := filepath.Join(dir, "file.txt")
+	if err := runCreate(createCmd, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	if err := os.WriteFile(srcPath, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	err := runAdd(addCmd, []string{pkgPath, srcPath})
+	if err != nil {
+		t.Fatalf("runAdd (open existing): %v", err)
+	}
+}
+
+func TestRunAdd_WithStoredPath(t *testing.T) {
+	addStoredPath = "/stored.txt"
+	defer func() { addStoredPath = "" }()
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "with-as.nvpk")
+	srcPath := filepath.Join(dir, "local.txt")
+	if err := os.WriteFile(srcPath, []byte("data"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	err := runAdd(addCmd, []string{pkgPath, srcPath})
+	if err != nil {
+		t.Fatalf("runAdd (with --as): %v", err)
+	}
+}
+
+func TestRunAdd_Directory(t *testing.T) {
+	dir := t.TempDir()
+	subdir := filepath.Join(dir, "sub")
+	if err := os.MkdirAll(subdir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(subdir, "a.txt"), []byte("a"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	pkgPath := filepath.Join(dir, "dirpkg.nvpk")
+	err := runAdd(addCmd, []string{pkgPath, subdir})
+	// AddDirectory is a stub; accept success or unsupported until full implementation
+	if err != nil && !strings.Contains(err.Error(), "unsupported") && !strings.Contains(err.Error(), "AddDirectory") {
+		t.Fatalf("runAdd (directory): %v", err)
+	}
+}
+
+func TestRunAdd_OpenInvalidPackage(t *testing.T) {
+	dir := t.TempDir()
+	// Path exists but is a regular file, not a package
+	fakePkg := filepath.Join(dir, "fake.nvpk")
+	if err := os.WriteFile(fakePkg, []byte("not a package"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	src := filepath.Join(dir, "f.txt")
+	if err := os.WriteFile(src, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	err := runAdd(addCmd, []string{fakePkg, src})
+	if err == nil {
+		t.Error("runAdd with non-package file path should fail")
+	}
+}
+
+func TestRunAdd_PackagePathIsDirectory(t *testing.T) {
+	dir := t.TempDir()
+	src := filepath.Join(dir, "f.txt")
+	if err := os.WriteFile(src, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	// Package path is an existing directory; OpenPackage will fail
+	err := runAdd(addCmd, []string{dir, src})
+	if err == nil {
+		t.Error("runAdd with directory as package path should fail")
+	}
+}
diff --git a/cli/nvpkg/cmd/comment.go b/cli/nvpkg/cmd/comment.go
new file mode 100644
index 00000000..98f0a3a4
--- /dev/null
+++ b/cli/nvpkg/cmd/comment.go
@@ -0,0 +1,71 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var commentCmd = &cobra.Command{
+	Use:   "comment <package path> [--set \"...\" | --clear]",
+	Short: "Get or set package comment",
+	Long:  "With no flags, prints the package comment. Use --set to set, --clear to remove. Changes are written to disk.",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runComment,
+}
+
+var (
+	commentSet   string
+	commentClear bool
+)
+
+func init() {
+	commentCmd.Flags().StringVar(&commentSet, "set", "", "Set comment to this string")
+	commentCmd.Flags().BoolVar(&commentClear, "clear", false, "Clear the comment")
+}
+
+func runComment(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	if commentSet != "" && commentClear {
+		return fmt.Errorf("cannot use both --set and --clear")
+	}
+
+	pkg, err := novuspack.OpenPackage(ctx, path)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	if commentClear {
+		if err := pkg.ClearComment(); err != nil {
+			return fmt.Errorf("clear comment: %w", err)
+		}
+		if err := pkg.Write(ctx); err != nil {
+			return fmt.Errorf("write: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Comment cleared\n")
+		return nil
+	}
+	if commentSet != "" {
+		if err := pkg.SetComment(commentSet); err != nil {
+			return fmt.Errorf("set comment: %w", err)
+		}
+		if err := pkg.Write(ctx); err != nil {
+			return fmt.Errorf("write: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Comment set\n")
+		return nil
+	}
+	comment := pkg.GetComment()
+	if comment == "" {
+		_, _ = fmt.Fprintln(os.Stdout, "(no comment)")
+	} else {
+		_, _ = fmt.Fprintf(os.Stdout, "%s\n", comment)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/comment_test.go b/cli/nvpkg/cmd/comment_test.go
new file mode 100644
index 00000000..49e9e27a
--- /dev/null
+++ b/cli/nvpkg/cmd/comment_test.go
@@ -0,0 +1,83 @@
+package cmd
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestRunComment_GetNoComment(t *testing.T) {
+	path := createTestPackage(t, "c1.nvpk")
+	commentSet = ""
+	commentClear = false
+	defer func() { commentSet = ""; commentClear = false }()
+	err := runComment(commentCmd, []string{path})
+	if err != nil {
+		t.Fatalf("runComment get: %v", err)
+	}
+}
+
+func TestRunComment_GetWithComment(t *testing.T) {
+	path := createTestPackage(t, "c2.nvpk")
+	commentSet = "hello"
+	commentClear = false
+	defer func() { commentSet = ""; commentClear = false }()
+	if err := runComment(commentCmd, []string{path}); err != nil {
+		t.Fatalf("runComment set: %v", err)
+	}
+	commentSet = ""
+	if err := runComment(commentCmd, []string{path}); err != nil {
+		t.Fatalf("runComment get after set: %v", err)
+	}
+}
+
+func TestRunComment_Set(t *testing.T) {
+	path := createTestPackage(t, "c3.nvpk")
+	commentSet = "test comment"
+	commentClear = false
+	defer func() { commentSet = ""; commentClear = false }()
+	if err := runComment(commentCmd, []string{path}); err != nil {
+		t.Fatalf("runComment set: %v", err)
+	}
+}
+
+func TestRunComment_Clear(t *testing.T) {
+	path := createTestPackage(t, "c4.nvpk")
+	commentSet = "x"
+	commentClear = false
+	defer func() { commentSet = ""; commentClear = false }()
+	if err := runComment(commentCmd, []string{path}); err != nil {
+		t.Fatalf("runComment set: %v", err)
+	}
+	commentSet = ""
+	commentClear = true
+	defer func() { commentClear = false }()
+	if err := runComment(commentCmd, []string{path}); err != nil {
+		t.Fatalf("runComment clear: %v", err)
+	}
+}
+
+func TestRunComment_BothSetAndClear(t *testing.T) {
+	path := createTestPackage(t, "c5.nvpk")
+	commentSet = "x"
+	commentClear = true
+	defer func() { commentSet = ""; commentClear = false }()
+	err := runComment(commentCmd, []string{path})
+	if err == nil {
+		t.Fatal("runComment with both --set and --clear should fail")
+	}
+	if !strings.Contains(err.Error(), "both") {
+		t.Errorf("runComment both: want error containing 'both', got %v", err)
+	}
+}
+
+func TestRunComment_NoSuchPackage(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "nonexistent.nvpk")
+	commentSet = ""
+	commentClear = false
+	err := runComment(commentCmd, []string{path})
+	if err == nil {
+		t.Fatal("runComment on nonexistent package should fail")
+	}
+}
diff --git a/cli/nvpkg/cmd/create.go b/cli/nvpkg/cmd/create.go
new file mode 100644
index 00000000..a8bccc04
--- /dev/null
+++ b/cli/nvpkg/cmd/create.go
@@ -0,0 +1,90 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strconv"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var createCmd = &cobra.Command{
+	Use:   "create <package path>",
+	Short: "Create a new empty NovusPack package",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runCreate,
+}
+
+var (
+	createComment  string
+	createVendorID uint32
+	createAppID    uint64
+	createModeStr  string
+)
+
+func init() {
+	createCmd.Flags().StringVar(&createComment, "comment", "", "Package comment")
+	createCmd.Flags().Uint32Var(&createVendorID, "vendor-id", 0, "Vendor ID")
+	createCmd.Flags().Uint64Var(&createAppID, "app-id", 0, "Application ID")
+	createCmd.Flags().StringVar(&createModeStr, "mode", "", "File mode for created package file (e.g. 0644)")
+}
+
+func runCreate(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		return fmt.Errorf("new package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	var opts *novuspack.CreateOptions
+	if createComment != "" || createVendorID != 0 || createAppID != 0 || createModeStr != "" {
+		opts = &novuspack.CreateOptions{
+			Comment:  createComment,
+			VendorID: createVendorID,
+			AppID:    createAppID,
+		}
+		if createModeStr != "" {
+			mode, err := parseFileMode(createModeStr)
+			if err != nil {
+				return fmt.Errorf("mode: %w", err)
+			}
+			opts.Permissions = mode
+		}
+	}
+	if opts != nil {
+		if err := pkg.CreateWithOptions(ctx, path, opts); err != nil {
+			return fmt.Errorf("create with options: %w", err)
+		}
+	} else {
+		if err := pkg.Create(ctx, path); err != nil {
+			return fmt.Errorf("create: %w", err)
+		}
+	}
+	if err := pkg.Write(ctx); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "Created %s\n", path)
+	return nil
+}
+
+// parseFileMode parses an octal or decimal file mode string (e.g. 0644, 420).
+func parseFileMode(s string) (os.FileMode, error) {
+	if s == "" {
+		return 0, fmt.Errorf("empty mode")
+	}
+	// Try octal first (0644)
+	n, err := strconv.ParseUint(s, 8, 32)
+	if err != nil {
+		// Try decimal
+		n, err = strconv.ParseUint(s, 10, 32)
+		if err != nil {
+			return 0, fmt.Errorf("invalid mode %q", s)
+		}
+	}
+	return os.FileMode(n), nil
+}
diff --git a/cli/nvpkg/cmd/create_test.go b/cli/nvpkg/cmd/create_test.go
new file mode 100644
index 00000000..e2e36b72
--- /dev/null
+++ b/cli/nvpkg/cmd/create_test.go
@@ -0,0 +1,117 @@
+package cmd
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestRunCreate_Success(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "pkg.nvpk")
+	err := runCreate(createCmd, []string{path})
+	if err != nil {
+		t.Fatalf("runCreate: %v", err)
+	}
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		t.Error("package file was not created")
+	}
+}
+
+func TestRunCreate_WithOptions(t *testing.T) {
+	createComment = "test comment"
+	createVendorID = 1
+	createAppID = 100
+	defer func() {
+		createComment = ""
+		createVendorID = 0
+		createAppID = 0
+	}()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "opts.nvpk")
+	err := runCreate(createCmd, []string{path})
+	if err != nil {
+		t.Fatalf("runCreate with options: %v", err)
+	}
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		t.Error("package file was not created")
+	}
+}
+
+func TestRunCreate_InvalidPath(t *testing.T) {
+	err := runCreate(createCmd, []string{""})
+	if err == nil {
+		t.Error("runCreate with empty path should fail")
+	}
+}
+
+func TestRunCreate_WithOptionsInvalidPath(t *testing.T) {
+	createComment = "x"
+	defer func() { createComment = "" }()
+	err := runCreate(createCmd, []string{""})
+	if err == nil {
+		t.Error("runCreate with options and empty path should fail")
+	}
+	if err != nil && !strings.Contains(err.Error(), "create with options") && !strings.Contains(err.Error(), "create") {
+		t.Errorf("runCreate options invalid path: want create error, got %v", err)
+	}
+}
+
+// TestRunCreate_ThenValidate creates a package then validates it via CLI (full write round-trip).
+func TestRunCreate_ThenValidate(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "pkg.nvpk")
+	if err := runCreate(createCmd, []string{path}); err != nil {
+		t.Fatalf("runCreate: %v", err)
+	}
+	if err := runValidate(validateCmd, []string{path}); err != nil {
+		t.Fatalf("runValidate after create: %v", err)
+	}
+}
+
+func TestRunCreate_WithMode(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "mode.nvpk")
+	createComment = ""
+	createVendorID = 0
+	createAppID = 0
+	createModeStr = "0644"
+	defer func() { createModeStr = "" }()
+	if err := runCreate(createCmd, []string{path}); err != nil {
+		t.Fatalf("runCreate with mode: %v", err)
+	}
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		t.Error("package file was not created")
+	}
+}
+
+func TestParseFileMode(t *testing.T) {
+	// 0644 octal == 420 decimal; "420" is valid octal (0o420 == 272) so code parses as octal first
+	mode0644 := os.FileMode(0o644)
+	tests := []struct {
+		s    string
+		want os.FileMode
+		ok   bool
+	}{
+		{"0644", mode0644, true},
+		{"420", os.FileMode(0o420), true}, // "420" parsed as octal = 272
+		{"499", os.FileMode(499), true},   // "499" invalid octal, parsed as decimal
+		{"", 0, false},
+		{"invalid", 0, false},
+	}
+	for _, tt := range tests {
+		got, err := parseFileMode(tt.s)
+		if tt.ok && err != nil {
+			t.Errorf("parseFileMode(%q): %v", tt.s, err)
+			continue
+		}
+		if !tt.ok && err == nil {
+			t.Errorf("parseFileMode(%q): expected error", tt.s)
+			continue
+		}
+		if tt.ok && got != tt.want {
+			t.Errorf("parseFileMode(%q) = %#o, want %#o", tt.s, got, tt.want)
+		}
+	}
+}
diff --git a/cli/nvpkg/cmd/extract.go b/cli/nvpkg/cmd/extract.go
new file mode 100644
index 00000000..658bed55
--- /dev/null
+++ b/cli/nvpkg/cmd/extract.go
@@ -0,0 +1,96 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var extractCmd = &cobra.Command{
+	Use:   "extract <package path> [internal path]",
+	Short: "Extract all or a subtree of files from a NovusPack package to a directory",
+	Long:  "Extract files from a .nvpk package to the filesystem. With no internal path, extracts all files. With an internal path (e.g. /docs), extracts only that file or directory subtree. Destination is set with -o/--output.",
+	Args:  cobra.MinimumNArgs(1),
+	RunE:  runExtract,
+}
+
+var extractOutput string
+var extractReadOnly bool
+
+func init() {
+	extractCmd.Flags().StringVarP(&extractOutput, "output", "o", "", "Directory to extract files into (required)")
+	_ = extractCmd.MarkFlagRequired("output")
+	extractCmd.Flags().BoolVar(&extractReadOnly, "read-only", false, "Open package read-only (no write risk)")
+}
+
+func runExtract(_ *cobra.Command, args []string) error {
+	pathPrefix := ""
+	if len(args) > 1 {
+		pathPrefix = strings.TrimPrefix(args[1], "/")
+	}
+	destDir, err := resolveExtractDest(extractOutput)
+	if err != nil {
+		return err
+	}
+	ctx := context.Background()
+	pkg, err := openPackage(ctx, args[0], extractReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	files, err := pkg.ListFiles()
+	if err != nil {
+		return fmt.Errorf("list files: %w", err)
+	}
+	for _, f := range files {
+		if !matchPathPrefix(f.PrimaryPath, pathPrefix) {
+			continue
+		}
+		if err := extractOneFile(ctx, pkg, destDir, f.PrimaryPath); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func resolveExtractDest(destDir string) (string, error) {
+	if destDir == "" {
+		return "", fmt.Errorf("output directory is required (use -o or --output)")
+	}
+	destDir, err := filepath.Abs(destDir)
+	if err != nil {
+		return "", fmt.Errorf("output path: %w", err)
+	}
+	if err := os.MkdirAll(destDir, 0o755); err != nil {
+		return "", fmt.Errorf("create output directory: %w", err)
+	}
+	return destDir, nil
+}
+
+func matchPathPrefix(displayPath, pathPrefix string) bool {
+	if pathPrefix == "" {
+		return true
+	}
+	return displayPath == pathPrefix || strings.HasPrefix(displayPath+"/", pathPrefix+"/")
+}
+
+func extractOneFile(ctx context.Context, pkg novuspack.Package, destDir, displayPath string) error {
+	storedPath := "/" + displayPath
+	data, err := pkg.ReadFile(ctx, storedPath)
+	if err != nil {
+		return fmt.Errorf("read %s: %w", storedPath, err)
+	}
+	destPath := filepath.Join(destDir, filepath.FromSlash(displayPath))
+	if err := os.MkdirAll(filepath.Dir(destPath), 0o755); err != nil {
+		return fmt.Errorf("create directory for %s: %w", destPath, err)
+	}
+	if err := os.WriteFile(destPath, data, 0o644); err != nil {
+		return fmt.Errorf("write %s: %w", destPath, err)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/extract_test.go b/cli/nvpkg/cmd/extract_test.go
new file mode 100644
index 00000000..ecb40575
--- /dev/null
+++ b/cli/nvpkg/cmd/extract_test.go
@@ -0,0 +1,232 @@
+package cmd
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+)
+
+func TestMatchPathPrefix(t *testing.T) {
+	tests := []struct {
+		displayPath string
+		pathPrefix  string
+		want        bool
+	}{
+		{"a", "", true},
+		{"a/b", "", true},
+		{"a", "a", true},
+		{"a/b", "a", true},
+		{"a/b/c", "a/b", true},
+		{"a", "b", false},
+		{"a/b", "b", false},
+		{"ab", "a", false},
+	}
+	for _, tt := range tests {
+		got := matchPathPrefix(tt.displayPath, tt.pathPrefix)
+		if got != tt.want {
+			t.Errorf("matchPathPrefix(%q, %q) => %v, want %v", tt.displayPath, tt.pathPrefix, got, tt.want)
+		}
+	}
+}
+
+func TestResolveExtractDest(t *testing.T) {
+	t.Run("empty_returns_error", func(t *testing.T) {
+		_, err := resolveExtractDest("")
+		if err == nil {
+			t.Error("resolveExtractDest(\"\") => nil error")
+		}
+	})
+	t.Run("valid_returns_abs", func(t *testing.T) {
+		dir := t.TempDir()
+		got, err := resolveExtractDest(dir)
+		if err != nil {
+			t.Fatalf("resolveExtractDest: %v", err)
+		}
+		if !filepath.IsAbs(got) {
+			t.Errorf("resolveExtractDest => %q not absolute", got)
+		}
+	})
+	t.Run("path_under_file_fails", func(t *testing.T) {
+		dir := t.TempDir()
+		blocker := filepath.Join(dir, "blocker")
+		if err := os.WriteFile(blocker, []byte("x"), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		_, err := resolveExtractDest(filepath.Join(blocker, "sub"))
+		if err == nil {
+			t.Error("resolveExtractDest under existing file should fail")
+		}
+	})
+}
+
+func TestRunExtract_NoOutputFlag(t *testing.T) {
+	path := createTestPackage(t, "ext_noout.nvpk")
+	extractOutput = ""
+	defer func() { extractOutput = "" }()
+	err := runExtract(nil, []string{path})
+	if err == nil {
+		t.Error("runExtract with empty output dir should fail")
+	}
+	if err != nil && !strings.Contains(err.Error(), "output") && !strings.Contains(err.Error(), "required") {
+		t.Errorf("runExtract no output: want error about output/required, got %v", err)
+	}
+}
+
+func TestRunExtract_BadPackagePath(t *testing.T) {
+	dir := t.TempDir()
+	outDir := filepath.Join(dir, "out")
+	extractOutput = outDir
+	defer func() { extractOutput = "" }()
+	err := runExtract(nil, []string{filepath.Join(dir, "nonexistent.nvpk")})
+	if err == nil {
+		t.Error("runExtract with nonexistent package should fail")
+	}
+}
+
+func TestRunExtract_WithPathPrefix(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	outDir := filepath.Join(dir, "out")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	extractOutput = outDir
+	defer func() { extractOutput = "" }()
+	// Path prefix that matches nothing in empty package; should complete without error
+	if err := runExtract(nil, []string{pkgPath, "/nonexistent"}); err != nil {
+		t.Fatalf("runExtract: %v", err)
+	}
+}
+
+func TestRunExtract_EmptyPackage(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	outDir := filepath.Join(dir, "out")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	extractOutput = outDir
+	defer func() { extractOutput = "" }()
+	if err := runExtract(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("runExtract: %v", err)
+	}
+	// Empty package: no files extracted; out dir may be created empty
+	if _, err := os.Stat(outDir); err != nil {
+		t.Errorf("output dir not created: %v", err)
+	}
+}
+
+// TestExtractOneFile covers extractOneFile using an in-memory package (no Write).
+func TestExtractOneFile(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "mem.nvpk")
+	outDir := filepath.Join(dir, "out")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/sub/b.txt", []byte("in-memory"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := extractOneFile(ctx, pkg, outDir, "sub/b.txt"); err != nil {
+		t.Fatalf("extractOneFile: %v", err)
+	}
+	gotPath := filepath.Join(outDir, "sub", "b.txt")
+	got, err := os.ReadFile(gotPath)
+	if err != nil {
+		t.Fatalf("read extracted file: %v", err)
+	}
+	if string(got) != "in-memory" {
+		t.Errorf("extracted content: got %q, want %q", string(got), "in-memory")
+	}
+}
+
+// TestRunExtract_OneFile covers runExtract when the package has one file on disk.
+func TestRunExtract_OneFile(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "one.nvpk")
+	outDir := filepath.Join(dir, "out")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/a.txt", []byte("extracted"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	extractOutput = outDir
+	defer func() { extractOutput = "" }()
+	if err := runExtract(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("runExtract: %v", err)
+	}
+	gotPath := filepath.Join(outDir, "a.txt")
+	got, err := os.ReadFile(gotPath)
+	if err != nil {
+		t.Fatalf("read extracted file: %v", err)
+	}
+	if string(got) != "extracted" {
+		t.Errorf("extracted content: got %q, want %q", string(got), "extracted")
+	}
+}
+
+func TestExtractOneFile_ReadError(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "empty.nvpk")
+	outDir := filepath.Join(dir, "out")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	// Package has no file at /missing.txt
+	err = extractOneFile(ctx, pkg, outDir, "missing.txt")
+	if err == nil {
+		t.Error("extractOneFile with missing path should fail")
+	}
+}
+
+func TestExtractOneFile_DestUnderFile(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	outDir := filepath.Join(dir, "blocker")
+	if err := os.WriteFile(outDir, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/a.txt", []byte("x"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	// destDir is a file, so MkdirAll(filepath.Dir(destPath)) or WriteFile will fail
+	err = extractOneFile(ctx, pkg, outDir, "a.txt")
+	if err == nil {
+		t.Error("extractOneFile with dest under file should fail")
+	}
+}
diff --git a/cli/nvpkg/cmd/header.go b/cli/nvpkg/cmd/header.go
new file mode 100644
index 00000000..612d297c
--- /dev/null
+++ b/cli/nvpkg/cmd/header.go
@@ -0,0 +1,32 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var headerCmd = &cobra.Command{
+	Use:   "header <package path>",
+	Short: "Print package header (format version, index offset, etc.)",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runHeader,
+}
+
+func runHeader(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	h, err := novuspack.ReadHeaderFromPath(ctx, path)
+	if err != nil {
+		return fmt.Errorf("read header: %w", err)
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "Magic:         0x%08X\n", h.Magic)
+	_, _ = fmt.Fprintf(os.Stdout, "FormatVersion: %d\n", h.FormatVersion)
+	_, _ = fmt.Fprintf(os.Stdout, "IndexStart:    %d\n", h.IndexStart)
+	_, _ = fmt.Fprintf(os.Stdout, "Flags:         0x%08X\n", h.Flags)
+	return nil
+}
diff --git a/cli/nvpkg/cmd/helpers_test.go b/cli/nvpkg/cmd/helpers_test.go
new file mode 100644
index 00000000..6ae5cc50
--- /dev/null
+++ b/cli/nvpkg/cmd/helpers_test.go
@@ -0,0 +1,17 @@
+package cmd
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+// createTestPackage creates an empty package at a temp path and returns the path.
+func createTestPackage(t *testing.T, name string) string {
+	t.Helper()
+	dir := t.TempDir()
+	path := filepath.Join(dir, name)
+	if err := runCreate(createCmd, []string{path}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	return path
+}
diff --git a/cli/nvpkg/cmd/identity.go b/cli/nvpkg/cmd/identity.go
new file mode 100644
index 00000000..3e4d7ec6
--- /dev/null
+++ b/cli/nvpkg/cmd/identity.go
@@ -0,0 +1,66 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var identityCmd = &cobra.Command{
+	Use:   "identity <package path> [--vendor-id N] [--app-id N]",
+	Short: "Get or set package Vendor ID and App ID",
+	Long:  "With no flags, prints Vendor ID and App ID. Use --vendor-id and/or --app-id to set. Changes are written to disk.",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runIdentity,
+}
+
+var (
+	identityVendorID uint32
+	identityAppID    uint64
+)
+
+func init() {
+	identityCmd.Flags().Uint32Var(&identityVendorID, "vendor-id", 0, "Set Vendor ID (0 to leave unchanged)")
+	identityCmd.Flags().Uint64Var(&identityAppID, "app-id", 0, "Set App ID (0 to leave unchanged)")
+}
+
+func runIdentity(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := novuspack.OpenPackage(ctx, path)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	// Check if we're setting (either flag provided with non-zero or explicit set)
+	setVendor := identityVendorID != 0
+	setApp := identityAppID != 0
+	// Allow setting to 0 via flag: if user passed --vendor-id 0 we still "set" to clear
+	// Cobra doesn't distinguish "not set" vs "set to 0" easily; we use non-zero for "set" here.
+	// So --vendor-id 0 and --app-id 0 mean "don't change" unless we add a separate --clear-vendor-id.
+	if setVendor {
+		if err := pkg.SetVendorID(identityVendorID); err != nil {
+			return fmt.Errorf("set vendor-id: %w", err)
+		}
+	}
+	if setApp {
+		if err := pkg.SetAppID(identityAppID); err != nil {
+			return fmt.Errorf("set app-id: %w", err)
+		}
+	}
+	if setVendor || setApp {
+		if err := pkg.Write(ctx); err != nil {
+			return fmt.Errorf("write: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Identity updated\n")
+		return nil
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "Vendor ID: %d\n", pkg.GetVendorID())
+	_, _ = fmt.Fprintf(os.Stdout, "App ID:    %d\n", pkg.GetAppID())
+	return nil
+}
diff --git a/cli/nvpkg/cmd/identity_test.go b/cli/nvpkg/cmd/identity_test.go
new file mode 100644
index 00000000..e7d31d0c
--- /dev/null
+++ b/cli/nvpkg/cmd/identity_test.go
@@ -0,0 +1,35 @@
+package cmd
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func runIdentityWithFlags(t *testing.T, vendorID uint32, appID uint64, path string) error {
+	t.Helper()
+	identityVendorID = vendorID
+	identityAppID = appID
+	defer func() { identityVendorID = 0; identityAppID = 0 }()
+	return runIdentity(identityCmd, []string{path})
+}
+
+func TestRunIdentity(t *testing.T) {
+	t.Run("get", func(t *testing.T) {
+		if err := runIdentityWithFlags(t, 0, 0, createTestPackage(t, "id1.nvpk")); err != nil {
+			t.Fatalf("runIdentity get: %v", err)
+		}
+	})
+	t.Run("set", func(t *testing.T) {
+		if err := runIdentityWithFlags(t, 1, 100, createTestPackage(t, "id2.nvpk")); err != nil {
+			t.Fatalf("runIdentity set: %v", err)
+		}
+	})
+	t.Run("no_such_package", func(t *testing.T) {
+		dir := t.TempDir()
+		path := filepath.Join(dir, "nonexistent.nvpk")
+		err := runIdentityWithFlags(t, 0, 0, path)
+		if err == nil {
+			t.Fatal("runIdentity on nonexistent package should fail")
+		}
+	})
+}
diff --git a/cli/nvpkg/cmd/info.go b/cli/nvpkg/cmd/info.go
new file mode 100644
index 00000000..bad12032
--- /dev/null
+++ b/cli/nvpkg/cmd/info.go
@@ -0,0 +1,50 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var infoCmd = &cobra.Command{
+	Use:   "info <package path>",
+	Short: "Show package metadata and summary",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runInfo,
+}
+
+var infoReadOnly bool
+
+func init() {
+	infoCmd.Flags().BoolVar(&infoReadOnly, "read-only", false, "Open package read-only (no write risk)")
+}
+
+func runInfo(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := openPackage(ctx, path, infoReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	info, err := pkg.GetInfo()
+	if err != nil {
+		return fmt.Errorf("get info: %w", err)
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "Path:       %s\n", path)
+	_, _ = fmt.Fprintf(os.Stdout, "File count: %d\n", info.FileCount)
+	_, _ = fmt.Fprintf(os.Stdout, "Uncompressed size: %d\n", info.FilesUncompressedSize)
+	_, _ = fmt.Fprintf(os.Stdout, "Compressed size:   %d\n", info.FilesCompressedSize)
+	if info.VendorID != 0 || info.AppID != 0 {
+		_, _ = fmt.Fprintf(os.Stdout, "Vendor ID:  %d\n", info.VendorID)
+		_, _ = fmt.Fprintf(os.Stdout, "App ID:     %d\n", info.AppID)
+	}
+	if info.Comment != "" {
+		_, _ = fmt.Fprintf(os.Stdout, "Comment:    %s\n", info.Comment)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/interactive.go b/cli/nvpkg/cmd/interactive.go
new file mode 100644
index 00000000..360fe6b2
--- /dev/null
+++ b/cli/nvpkg/cmd/interactive.go
@@ -0,0 +1,1116 @@
+package cmd
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/novus-engine/novuspack/cli/nvpkg/cmd/liner"
+	"github.com/spf13/cobra"
+)
+
+// Interactive session state: one open package at a time. Changes stay in-memory until write.
+var interactivePkg novuspack.Package
+var interactivePkgPath string
+
+// completerCwd is set each prompt so the tab completer can suggest paths.
+var completerCwd string
+
+// InteractiveStdin, InteractiveStdout, InteractiveStderr are set by tests to inject I/O.
+// When nil, runInteractive uses os.Stdin, os.Stdout, os.Stderr.
+var InteractiveStdin io.Reader
+var InteractiveStdout io.Writer
+var InteractiveStderr io.Writer
+
+func getInteractiveStdin() io.Reader {
+	if InteractiveStdin != nil {
+		return InteractiveStdin
+	}
+	return os.Stdin
+}
+
+func getInteractiveStdout() io.Writer {
+	if InteractiveStdout != nil {
+		return InteractiveStdout
+	}
+	return os.Stdout
+}
+
+func getInteractiveStderr() io.Writer {
+	if InteractiveStderr != nil {
+		return InteractiveStderr
+	}
+	return os.Stderr
+}
+
+// expandTilde expands ~ to the current user's home directory and ~/path to home/path.
+// Paths not starting with ~ are returned unchanged.
+func expandTilde(path string) string {
+	if path == "" || path[0] != '~' {
+		return path
+	}
+	if len(path) == 1 {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return path
+		}
+		return home
+	}
+	if path[1] == '/' || path[1] == filepath.Separator {
+		home, err := os.UserHomeDir()
+		if err != nil {
+			return path
+		}
+		return filepath.Join(home, path[2:])
+	}
+	return path
+}
+
+var interactiveCmd = &cobra.Command{
+	Use:   "interactive",
+	Short: "Run nvpkg in interactive mode (REPL)",
+	Long:  "Starts a read-eval-print loop. Use 'open <path>' to set the current package; then list, add, remove, read use that path. Use 'help' for commands, 'quit' or 'exit' to leave.",
+	Args:  cobra.NoArgs,
+	RunE:  runInteractive,
+}
+
+func init() {
+	interactiveCmd.Aliases = []string{"i"}
+}
+
+func runInteractive(_ *cobra.Command, _ []string) error {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("getwd: %w", err)
+	}
+	closeInteractiveSession()
+	var currentPackage string
+	// Use liner for history/arrows when stdin is real (nil = os.Stdin); tests inject a Reader.
+	if InteractiveStdin == nil {
+		return liner.Run(cwd, &currentPackage, processLinerLine, interactiveCompleter, func(s string) { completerCwd = s })
+	}
+	scanner := bufio.NewScanner(getInteractiveStdin())
+	for {
+		line, done, err := readInteractiveLine(scanner, currentPackage)
+		if err != nil {
+			return err
+		}
+		if done {
+			break
+		}
+		if line == "" {
+			continue
+		}
+		line = stripComment(line)
+		if line == "" {
+			continue
+		}
+		segments, separators := splitInteractiveLine(line)
+		if len(segments) == 0 {
+			continue
+		}
+		var didExit bool
+		didExit, cwd, currentPackage = runInteractiveSegments(segments, separators, cwd, currentPackage)
+		if didExit {
+			return nil
+		}
+	}
+	return nil
+}
+
+// processLinerLine runs one line (supports ; && || and # comments); returns (exit, finalCwd, finalPackage).
+func processLinerLine(line, cwd, currentPackage string) (exit bool, finalCwd, finalPkg string) {
+	line = strings.TrimSpace(line)
+	if line == "" {
+		return false, cwd, currentPackage
+	}
+	line = stripComment(line)
+	line = strings.TrimSpace(line)
+	if line == "" {
+		return false, cwd, currentPackage
+	}
+	segments, separators := splitInteractiveLine(line)
+	if len(segments) == 0 {
+		return false, cwd, currentPackage
+	}
+	return runInteractiveSegments(segments, separators, cwd, currentPackage)
+}
+
+func readInteractiveLine(scanner *bufio.Scanner, currentPackage string) (line string, done bool, err error) {
+	prompt := "nvpkg> "
+	if currentPackage != "" {
+		prompt = fmt.Sprintf("nvpkg [%s]> ", currentPackage)
+	}
+	_, _ = fmt.Fprint(getInteractiveStdout(), prompt)
+	if !scanner.Scan() {
+		return "", true, scanner.Err()
+	}
+	return strings.TrimSpace(scanner.Text()), false, nil
+}
+
+func applyInteractiveCwdAndPkg(cwd, newCwd, currentPackage, newCurrent string, changed bool) (finalCwd, finalPkg string) {
+	if newCwd != "" {
+		if err := os.Chdir(newCwd); err != nil {
+			_, _ = fmt.Fprintf(getInteractiveStderr(), "chdir: %v\n", err)
+		} else {
+			cwd = newCwd
+			_, _ = fmt.Fprintf(getInteractiveStdout(), "%s\n", cwd)
+		}
+	}
+	if !changed {
+		return cwd, currentPackage
+	}
+	if newCurrent != "" {
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Current package: %s\n", newCurrent)
+	} else {
+		_, _ = fmt.Fprintln(getInteractiveStdout(), "No current package")
+	}
+	return cwd, newCurrent
+}
+
+type interactiveHandler func(args []string, flags map[string]string, currentPackage, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error)
+
+// resolvedPkgRunner runs a command given resolved pkgPath; used by header, validate, remove, read.
+type resolvedPkgRunner func(pkgPath string, args []string, flags map[string]string) (newCurrent string, changed, exit bool, newCwd string, err error)
+
+func makeResolvedPkgHandler(run resolvedPkgRunner) interactiveHandler {
+	return func(args []string, flags map[string]string, currentPackage, cwd string) (string, bool, bool, string, error) {
+		return withResolvedPkgPath(args, currentPackage, func(pkgPath string) (string, bool, bool, string, error) {
+			return run(pkgPath, args, flags)
+		})
+	}
+}
+
+var interactiveHandlers = map[string]interactiveHandler{
+	"quit":     interactiveQuit,
+	"exit":     interactiveQuit,
+	"q":        interactiveQuit,
+	"help":     interactiveHelp,
+	"h":        interactiveHelp,
+	"?":        interactiveHelp,
+	"open":     interactiveOpen,
+	"close":    interactiveClose,
+	"write":    interactiveWriteHandler,
+	"pwd":      interactivePwd,
+	"cd":       interactiveCd,
+	"ls":       interactiveLs,
+	"create":   interactiveCreateHandler,
+	"info":     interactiveInfoHandler,
+	"list":     interactiveListHandler,
+	"add":      interactiveAddHandler,
+	"extract":  interactiveExtractHandler,
+	"comment":  interactiveCommentHandler,
+	"identity": interactiveIdentityHandler,
+}
+
+func init() {
+	for cmd, run := range map[string]resolvedPkgRunner{
+		"header":   headerRunner,
+		"validate": validateRunner,
+		"remove":   removeRunner,
+		"read":     readRunner,
+	} {
+		interactiveHandlers[cmd] = makeResolvedPkgHandler(run)
+	}
+}
+
+// interactiveCommandNames are all command names (no aliases) for tab completion.
+var interactiveCommandNames = []string{
+	"add", "close", "comment", "create", "cd", "extract", "header", "help", "identity", "info", "list", "ls", "open", "pwd", "quit", "read", "remove", "validate", "write",
+}
+
+// pathTakingCommands are commands whose first argument is a path (open, cd, ls, create, add).
+var pathTakingCommands = map[string]bool{
+	"open": true, "cd": true, "ls": true, "create": true, "add": true,
+}
+
+// interactiveCompleter returns completion candidates for the line (content left of cursor).
+// Liner expects full-line completions: each candidate replaces the entire line prefix, so we
+// return e.g. "cd cli/" not "cli/" when the user types "cd c". completerCwd must be set by the REPL loop.
+func interactiveCompleter(line string) []string {
+	line = strings.TrimLeft(line, " \t")
+	if line == "" {
+		return interactiveCommandNames
+	}
+	tokens := tokenizeLine(line)
+	if len(tokens) == 0 {
+		return interactiveCommandNames
+	}
+	first := tokens[0]
+	lastToken := tokens[len(tokens)-1]
+	var prefix string
+	trailingSpace := strings.HasSuffix(line, " ") || strings.HasSuffix(line, "\t")
+	if len(tokens) > 1 {
+		prefix = strings.Join(tokens[:len(tokens)-1], " ") + " "
+	} else if len(tokens) == 1 && pathTakingCommands[first] && trailingSpace {
+		prefix = first + " "
+		lastToken = ""
+	}
+	if len(tokens) == 1 && (!pathTakingCommands[first] || !trailingSpace) {
+		return completeCommands(first)
+	}
+	if !pathTakingCommands[first] {
+		return nil
+	}
+	candidates := completePath(first, lastToken)
+	if len(candidates) == 0 {
+		return nil
+	}
+	out := make([]string, 0, len(candidates))
+	for _, c := range candidates {
+		out = append(out, prefix+c)
+	}
+	return out
+}
+
+func completeCommands(prefix string) []string {
+	var out []string
+	for _, c := range interactiveCommandNames {
+		if strings.HasPrefix(c, prefix) {
+			out = append(out, c)
+		}
+	}
+	return out
+}
+
+func completePath(first, last string) []string {
+	dir := completerCwd
+	prefix := last
+	if last != "" && !filepath.IsAbs(last) && !strings.HasPrefix(last, "~") {
+		dir = filepath.Join(completerCwd, filepath.Dir(last))
+		prefix = filepath.Base(last)
+		if dir == "." {
+			dir = completerCwd
+		}
+	} else if last != "" {
+		expanded := expandTilde(last)
+		dir = filepath.Dir(expanded)
+		prefix = filepath.Base(expanded)
+	}
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil
+	}
+	prefixDir := filepath.Dir(last)
+	var out []string
+	for _, e := range entries {
+		name := e.Name()
+		if prefix != "" && !strings.HasPrefix(name, prefix) {
+			continue
+		}
+		if e.IsDir() {
+			name += string(filepath.Separator)
+		}
+		if prefixDir != "" && prefixDir != "." {
+			name = filepath.Join(prefixDir, name)
+		}
+		out = append(out, name)
+	}
+	return out
+}
+
+func closeInteractiveSession() {
+	if interactivePkg != nil {
+		_ = interactivePkg.Close()
+		interactivePkg = nil
+		interactivePkgPath = ""
+	}
+}
+
+func interactiveQuit([]string, map[string]string, string, string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	closeInteractiveSession()
+	return "", false, true, "", nil
+}
+
+func interactiveHelp([]string, map[string]string, string, string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	printInteractiveHelp(getInteractiveStdout())
+	return "", false, false, "", nil
+}
+
+func interactiveOpen(args []string, flags map[string]string, _, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	if len(args) < 1 {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "open: requires package path")
+		return "", false, false, "", nil
+	}
+	path := expandTilde(args[0])
+	closeInteractiveSession()
+	ctx := context.Background()
+	var pkg novuspack.Package
+	if flags["read-only"] == "1" || flags["read-only"] == "true" || flags["read-only"] == "yes" {
+		pkg, err = novuspack.OpenPackageReadOnly(ctx, path)
+	} else {
+		pkg, err = openOrCreatePackage(ctx, path)
+	}
+	if err != nil {
+		_, _ = fmt.Fprintf(getInteractiveStderr(), "open: %v\n", err)
+		return "", false, false, "", nil
+	}
+	interactivePkg = pkg
+	interactivePkgPath = path
+	return path, true, false, "", nil
+}
+
+func interactiveClose([]string, map[string]string, string, string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	closeInteractiveSession()
+	return "", true, false, "", nil
+}
+
+func interactiveWriteHandler(_ []string, flags map[string]string, currentPackage, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath := currentPackage
+	if pkgPath == "" && interactivePkgPath != "" {
+		pkgPath = interactivePkgPath
+	}
+	if interactivePkg == nil || interactivePkgPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' first.")
+		return "", false, false, "", nil
+	}
+	if pkgPath != interactivePkgPath {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' first.")
+		return "", false, false, "", nil
+	}
+	ctx := context.Background()
+	overwrite := true
+	if v := flags["overwrite"]; v == "0" || v == "false" || v == "no" {
+		overwrite = false
+	}
+	if err := interactivePkg.SafeWrite(ctx, overwrite); err != nil {
+		return "", false, false, "", fmt.Errorf("write: %w", err)
+	}
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Wrote %s\n", interactivePkgPath)
+	return "", false, false, "", nil
+}
+
+func interactiveCommentHandler(args []string, flags map[string]string, _, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	if interactivePkg == nil || interactivePkgPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' first.")
+		return "", false, false, "", nil
+	}
+	if flags["clear"] == "1" || flags["clear"] == "true" || flags["clear"] == "yes" {
+		if err := interactivePkg.ClearComment(); err != nil {
+			return "", false, false, "", fmt.Errorf("clear comment: %w", err)
+		}
+		_, _ = fmt.Fprintln(getInteractiveStdout(), "Comment cleared (use 'write' to persist)")
+		return "", false, false, "", nil
+	}
+	if v := flags["set"]; v != "" {
+		if err := interactivePkg.SetComment(v); err != nil {
+			return "", false, false, "", fmt.Errorf("set comment: %w", err)
+		}
+		_, _ = fmt.Fprintln(getInteractiveStdout(), "Comment set (use 'write' to persist)")
+		return "", false, false, "", nil
+	}
+	comment := interactivePkg.GetComment()
+	if comment == "" {
+		_, _ = fmt.Fprintln(getInteractiveStdout(), "(no comment)")
+	} else {
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "%s\n", comment)
+	}
+	return "", false, false, "", nil
+}
+
+func interactiveIdentityHandler(_ []string, flags map[string]string, _, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	if interactivePkg == nil || interactivePkgPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' first.")
+		return "", false, false, "", nil
+	}
+	if v := flags["vendor-id"]; v != "" {
+		n, e := strconv.ParseUint(v, 10, 32)
+		if e != nil {
+			return "", false, false, "", fmt.Errorf("vendor-id: %w", e)
+		}
+		if err := interactivePkg.SetVendorID(uint32(n)); err != nil {
+			return "", false, false, "", fmt.Errorf("set vendor-id: %w", err)
+		}
+	}
+	if v := flags["app-id"]; v != "" {
+		n, e := strconv.ParseUint(v, 10, 64)
+		if e != nil {
+			return "", false, false, "", fmt.Errorf("app-id: %w", e)
+		}
+		if err := interactivePkg.SetAppID(n); err != nil {
+			return "", false, false, "", fmt.Errorf("set app-id: %w", err)
+		}
+	}
+	if flags["vendor-id"] != "" || flags["app-id"] != "" {
+		_, _ = fmt.Fprintln(getInteractiveStdout(), "Identity updated (use 'write' to persist)")
+		return "", false, false, "", nil
+	}
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Vendor ID: %d\n", interactivePkg.GetVendorID())
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "App ID:    %d\n", interactivePkg.GetAppID())
+	return "", false, false, "", nil
+}
+
+func interactivePwd(_ []string, _ map[string]string, _, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	_, _ = fmt.Fprintln(getInteractiveStdout(), cwd)
+	return "", false, false, "", nil
+}
+
+func interactiveCd(args []string, _ map[string]string, _, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	var dir string
+	if len(args) >= 1 {
+		dir = expandTilde(args[0])
+		if !filepath.IsAbs(dir) {
+			dir = filepath.Join(cwd, dir)
+		}
+	} else {
+		home, e := os.UserHomeDir()
+		if e != nil {
+			return "", false, false, "", fmt.Errorf("home: %w", e)
+		}
+		dir = home
+	}
+	abs, e := filepath.Abs(dir)
+	if e != nil {
+		return "", false, false, "", fmt.Errorf("cd: %w", e)
+	}
+	info, e := os.Stat(abs)
+	if e != nil {
+		return "", false, false, "", fmt.Errorf("cd: %w", e)
+	}
+	if !info.IsDir() {
+		return "", false, false, "", fmt.Errorf("cd: %s is not a directory", abs)
+	}
+	return "", false, false, abs, nil
+}
+
+func interactiveLs(args []string, _ map[string]string, _, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	dir := cwd
+	if len(args) >= 1 {
+		dir = expandTilde(args[0])
+		if !filepath.IsAbs(dir) {
+			dir = filepath.Join(cwd, dir)
+		}
+	}
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return "", false, false, "", fmt.Errorf("ls: %w", err)
+	}
+	for _, e := range entries {
+		info, ierr := e.Info()
+		sizeStr := "-"
+		modStr := "-"
+		if ierr == nil {
+			if !e.IsDir() {
+				sizeStr = formatFileSize(info.Size())
+			}
+			modStr = info.ModTime().Format("Jan _2 15:04")
+		}
+		name := e.Name()
+		if e.IsDir() {
+			name += "/"
+		}
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "%10s  %12s  %s\n", sizeStr, modStr, name)
+	}
+	return "", false, false, "", nil
+}
+
+func formatFileSize(n int64) string {
+	const unit = 1024
+	if n < unit {
+		return strconv.FormatInt(n, 10)
+	}
+	div, exp := int64(unit), 0
+	for v := n / unit; v >= unit; v /= unit {
+		div *= unit
+		exp++
+	}
+	suffix := []string{"K", "M", "G", "T"}[exp]
+	return fmt.Sprintf("%.1f%s", float64(n)/float64(div), suffix)
+}
+
+func interactiveCreateHandler(args []string, flags map[string]string, _, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	newCurrent, changed, exit, err = runInteractiveCreate(args, flags, cwd)
+	return newCurrent, changed, exit, "", err
+}
+
+func interactiveListHandler(args []string, _ map[string]string, currentPackage, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath := resolvePkgPath(args, currentPackage)
+	if pkgPath == "" {
+		return "", false, false, "", nil
+	}
+	if interactivePkg != nil && interactivePkgPath == pkgPath {
+		return "", false, false, "", listFromPackage(interactivePkg)
+	}
+	return "", false, false, "", runList(nil, []string{pkgPath})
+}
+
+func interactiveInfoHandler(args []string, _ map[string]string, currentPackage, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath := resolvePkgPath(args, currentPackage)
+	if pkgPath == "" {
+		return "", false, false, "", nil
+	}
+	if interactivePkg != nil && interactivePkgPath == pkgPath {
+		return "", false, false, "", infoFromPackage(interactivePkg, pkgPath)
+	}
+	return "", false, false, "", runInfo(nil, []string{pkgPath})
+}
+
+func headerRunner(pkgPath string, _ []string, _ map[string]string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	return "", false, false, "", runHeader(nil, []string{pkgPath})
+}
+
+func validateRunner(pkgPath string, _ []string, _ map[string]string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	return "", false, false, "", runValidate(nil, []string{pkgPath})
+}
+
+func removeRunner(pkgPath string, args []string, flags map[string]string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	newCurrent, changed, exit, err = runInteractiveRemove(args, flags, pkgPath)
+	return newCurrent, changed, exit, "", err
+}
+
+func readRunner(pkgPath string, args []string, flags map[string]string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	newCurrent, changed, exit, err = runInteractiveRead(args, flags, pkgPath)
+	return newCurrent, changed, exit, "", err
+}
+
+func listFromPackage(pkg novuspack.Package) error {
+	files, err := pkg.ListFiles()
+	if err != nil {
+		return err
+	}
+	for _, f := range files {
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "%s  %d  %d\n", f.PrimaryPath, f.Size, f.StoredSize)
+	}
+	return nil
+}
+
+func infoFromPackage(pkg novuspack.Package, pkgPath string) error {
+	info, err := pkg.GetInfo()
+	if err != nil {
+		return err
+	}
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Path:       %s\n", pkgPath)
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "File count: %d\n", info.FileCount)
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Uncompressed size: %d\n", info.FilesUncompressedSize)
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Compressed size:   %d\n", info.FilesCompressedSize)
+	if info.VendorID != 0 || info.AppID != 0 {
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Vendor ID:  %d\n", info.VendorID)
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "App ID:     %d\n", info.AppID)
+	}
+	if info.Comment != "" {
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Comment:    %s\n", info.Comment)
+	}
+	return nil
+}
+
+func interactiveAddHandler(args []string, flags map[string]string, currentPackage, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath, sources := resolveAddArgs(args, currentPackage)
+	if pkgPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' or add src1 src2 path.nvpk.")
+		return "", false, false, "", nil
+	}
+	if len(sources) == 0 {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "add: requires at least one file or directory")
+		return "", false, false, "", nil
+	}
+	return runInteractiveAdd(sources, flags, expandTilde(pkgPath), cwd)
+}
+
+func resolvePkgPath(args []string, currentPackage string) string {
+	if currentPackage != "" {
+		return currentPackage
+	}
+	if len(args) >= 1 {
+		return expandTilde(args[0])
+	}
+	_, _ = fmt.Fprintln(getInteractiveStderr(), "No current package. Use 'open <path>' or pass package path (e.g. add src1 src2 path.nvpk).")
+	return ""
+}
+
+// withResolvedPkgPath resolves package path from args/currentPackage; if empty returns zero values.
+// Otherwise calls run(pkgPath) and returns its result. Shared by header, validate, remove, read handlers.
+func withResolvedPkgPath(args []string, currentPackage string, run func(pkgPath string) (newCurrent string, changed, exit bool, newCwd string, err error)) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath := resolvePkgPath(args, currentPackage)
+	if pkgPath == "" {
+		return "", false, false, "", nil
+	}
+	return run(pkgPath)
+}
+
+// runInteractiveOne runs one interactive command. Returns (new current package, changed, exit, newCwd, err).
+// changed is true only for open/close; then newCurrent is the new value to set. newCwd is set by cd.
+func runInteractiveOne(cmd string, args []string, flags map[string]string, currentPackage, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	h, ok := interactiveHandlers[cmd]
+	if !ok {
+		_, _ = fmt.Fprintf(getInteractiveStderr(), "Unknown command: %s (use 'help')\n", cmd)
+		return "", false, false, "", nil
+	}
+	resetInteractiveFlags()
+	return h(args, flags, currentPackage, cwd)
+}
+
+func runInteractiveCreate(args []string, flags map[string]string, cwd string) (newCurrent string, changed, exit bool, err error) {
+	if len(args) < 1 {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "create: requires package path")
+		return "", false, false, nil
+	}
+	setCreateFlags(flags)
+	pathArg := expandTilde(args[0])
+	if err := runCreate(nil, []string{pathArg}); err != nil {
+		return "", false, false, err
+	}
+	absPath, e := filepath.Abs(pathArg)
+	if e != nil {
+		return "", false, false, fmt.Errorf("create: %w", e)
+	}
+	ctx := context.Background()
+	closeInteractiveSession()
+	pkg, err := novuspack.OpenPackage(ctx, absPath)
+	if err != nil {
+		return "", false, false, fmt.Errorf("open after create: %w", err)
+	}
+	interactivePkg = pkg
+	interactivePkgPath = absPath
+	return absPath, true, false, nil
+}
+
+// resolveAddArgs parses add [src]... [path]: sources first, optional package path last when no current package.
+func resolveAddArgs(args []string, currentPackage string) (pkgPath string, sources []string) {
+	if currentPackage != "" {
+		return currentPackage, args
+	}
+	if len(args) < 2 {
+		return "", args
+	}
+	// Last arg is package path, rest are sources.
+	return args[len(args)-1], args[:len(args)-1]
+}
+
+func runInteractiveAdd(sources []string, flags map[string]string, pkgPath, cwd string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	resolved := make([]string, 0, len(sources))
+	for _, p := range sources {
+		q := expandTilde(p)
+		if !filepath.IsAbs(q) {
+			q = filepath.Join(cwd, q)
+		}
+		resolved = append(resolved, filepath.Clean(q))
+	}
+	opts, err := buildAddFileOptions(flags)
+	if err != nil {
+		return "", false, false, "", err
+	}
+	ctx := context.Background()
+	var pkg novuspack.Package
+	if interactivePkg != nil && interactivePkgPath == pkgPath {
+		pkg = interactivePkg
+	} else {
+		pkg, err = openOrCreatePackage(ctx, pkgPath)
+		if err != nil {
+			return "", false, false, "", fmt.Errorf("open: %w", err)
+		}
+		// Make this the current package for the session (in-memory until write)
+		if interactivePkg != nil {
+			_ = interactivePkg.Close()
+		}
+		interactivePkg = pkg
+		interactivePkgPath = pkgPath
+	}
+	if err := addSources(ctx, pkg, resolved, opts); err != nil {
+		return "", false, false, "", err
+	}
+	_, _ = fmt.Fprintf(getInteractiveStdout(), "Added %d item(s) (in-memory; use 'write' to persist)\n", len(resolved))
+	return "", false, false, "", nil
+}
+
+// resolveRemoveInternalPath returns the internal path for remove from args/flags/pkgPath, or "" if missing.
+func resolveRemoveInternalPath(args []string, flags map[string]string, pkgPath string) string {
+	switch {
+	case flags["pattern"] != "":
+		return flags["pattern"]
+	case len(args) >= 2 && pkgPath == args[0]:
+		return args[1]
+	case len(args) >= 1:
+		return args[0]
+	default:
+		return ""
+	}
+}
+
+// ensureInteractivePackage returns the open package for pkgPath, reusing interactivePkg if it matches
+// or opening and setting interactivePkg/interactivePkgPath. Caller must not close the returned package.
+func ensureInteractivePackage(ctx context.Context, pkgPath string) (novuspack.Package, error) {
+	if interactivePkg != nil && interactivePkgPath == pkgPath {
+		return interactivePkg, nil
+	}
+	pkg, err := novuspack.OpenPackage(ctx, pkgPath)
+	if err != nil {
+		return nil, err
+	}
+	if interactivePkg != nil {
+		_ = interactivePkg.Close()
+	}
+	interactivePkg = pkg
+	interactivePkgPath = pkgPath
+	return pkg, nil
+}
+
+func runInteractiveRemove(args []string, flags map[string]string, pkgPath string) (newCurrent string, changed, exit bool, err error) {
+	internalPath := resolveRemoveInternalPath(args, flags, pkgPath)
+	if internalPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "remove: requires internal path or --pattern <pattern>")
+		return "", false, false, nil
+	}
+	ctx := context.Background()
+	pkg, pkgErr := ensureInteractivePackage(ctx, pkgPath)
+	if pkgErr != nil {
+		return "", false, false, fmt.Errorf("open: %w", pkgErr)
+	}
+	switch {
+	case flags["pattern"] != "":
+		_, err := pkg.RemoveFilePattern(ctx, internalPath)
+		if err != nil {
+			return "", false, false, err
+		}
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Removed files matching %q (in-memory; use 'write' to persist)\n", internalPath)
+	case internalPath != "" && internalPath[len(internalPath)-1] == '/':
+		_, err := pkg.RemoveDirectory(ctx, internalPath, nil)
+		if err != nil {
+			return "", false, false, err
+		}
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Removed directory %s (in-memory; use 'write' to persist)\n", internalPath)
+	default:
+		if err := pkg.RemoveFile(ctx, internalPath); err != nil {
+			return "", false, false, err
+		}
+		_, _ = fmt.Fprintf(getInteractiveStdout(), "Removed %s (in-memory; use 'write' to persist)\n", internalPath)
+	}
+	return "", false, false, nil
+}
+
+func runInteractiveRead(args []string, flags map[string]string, pkgPath string) (newCurrent string, changed, exit bool, err error) {
+	internalPath := ""
+	if len(args) >= 2 && pkgPath == args[0] {
+		internalPath = args[1]
+	} else if len(args) >= 1 {
+		internalPath = args[0]
+	}
+	if internalPath == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "read: requires internal path")
+		return "", false, false, nil
+	}
+	outPath := flags["output"]
+	if outPath != "" {
+		outPath = expandTilde(outPath)
+	}
+	if interactivePkg != nil && interactivePkgPath == pkgPath {
+		return "", false, false, readFromPackage(interactivePkg, internalPath, outPath)
+	}
+	if outPath != "" {
+		readOutput = outPath
+	} else {
+		readOutput = ""
+	}
+	err = runRead(nil, []string{pkgPath, internalPath})
+	return "", false, false, err
+}
+
+func readFromPackage(pkg novuspack.Package, internalPath, outPath string) error {
+	ctx := context.Background()
+	data, err := pkg.ReadFile(ctx, internalPath)
+	if err != nil {
+		return err
+	}
+	if outPath != "" {
+		return os.WriteFile(outPath, data, 0o644)
+	}
+	_, err = getInteractiveStdout().Write(data)
+	return err
+}
+
+func interactiveExtractHandler(args []string, flags map[string]string, currentPackage, _ string) (newCurrent string, changed, exit bool, newCwd string, err error) {
+	pkgPath := resolvePkgPath(args, currentPackage)
+	if pkgPath == "" {
+		return "", false, false, "", nil
+	}
+	outDir := flags["output"]
+	if outDir == "" {
+		_, _ = fmt.Fprintln(getInteractiveStderr(), "extract: requires -o or --output <directory>")
+		return "", false, false, "", nil
+	}
+	extractArgs := []string{pkgPath}
+	if len(args) >= 2 && pkgPath == args[0] {
+		extractArgs = append(extractArgs, args[1])
+	} else if len(args) >= 1 && args[0] != pkgPath {
+		extractArgs = append(extractArgs, args[0])
+	}
+	extractOutput = expandTilde(outDir)
+	err = runExtract(nil, extractArgs)
+	return "", false, false, "", err
+}
+
+func resetInteractiveFlags() {
+	addStoredPath = ""
+	readOutput = ""
+	extractOutput = ""
+	createComment = ""
+	createVendorID = 0
+	createAppID = 0
+	createModeStr = ""
+}
+
+func setCreateFlags(flags map[string]string) {
+	if v := flags["comment"]; v != "" {
+		createComment = v
+	}
+	if v := flags["vendor-id"]; v != "" {
+		if u, err := strconv.ParseUint(v, 10, 32); err == nil {
+			createVendorID = uint32(u)
+		}
+	}
+	if v := flags["app-id"]; v != "" {
+		if u, err := strconv.ParseUint(v, 10, 64); err == nil {
+			createAppID = u
+		}
+	}
+	if v := flags["mode"]; v != "" {
+		createModeStr = v
+	}
+}
+
+type interactiveFlagDef struct {
+	names []string // e.g. []string{"--as"} or []string{"-o", "--output"}
+	key   string   // e.g. "as", "output"
+}
+
+var interactiveFlags = []interactiveFlagDef{
+	{[]string{"--as"}, "as"},
+	{[]string{"-o", "--output"}, "output"},
+	{[]string{"--comment"}, "comment"},
+	{[]string{"--vendor-id"}, "vendor-id"},
+	{[]string{"--app-id"}, "app-id"},
+	{[]string{"--pattern"}, "pattern"},
+	{[]string{"--base-path"}, "base-path"},
+	{[]string{"--preserve-depth"}, "preserve-depth"},
+	{[]string{"--flatten"}, "flatten"},
+	{[]string{"--no-follow-symlinks"}, "no-follow-symlinks"},
+	{[]string{"--preserve-permissions"}, "preserve-permissions"},
+	{[]string{"--preserve-ownership"}, "preserve-ownership"},
+	{[]string{"--overwrite"}, "overwrite"},
+	{[]string{"--set"}, "set"},
+	{[]string{"--clear"}, "clear"},
+	{[]string{"--read-only"}, "read-only"},
+	{[]string{"--mode"}, "mode"},
+}
+
+// stripComment removes a trailing comment from line. A # starts a comment only when
+// not inside a double-quoted string. The rest of the line after the comment is removed.
+func stripComment(line string) string {
+	inQuote := false
+	for i := 0; i < len(line); i++ {
+		c := line[i]
+		switch {
+		case c == '"':
+			inQuote = !inQuote
+		case c == '#' && !inQuote:
+			return strings.TrimSpace(line[:i])
+		default:
+			// continue
+		}
+	}
+	return line
+}
+
+// splitInteractiveLine splits line by ; && and ||, respecting double-quoted strings.
+// Returns trimmed segments and separators; len(separators) == len(segments)-1.
+// Separators are ";", "&&", or "||".
+func splitInteractiveLine(line string) (segments, separators []string) {
+	line = strings.TrimSpace(line)
+	if line == "" {
+		return nil, nil
+	}
+	var seg strings.Builder
+	inQuote := false
+	i := 0
+	for i < len(line) {
+		c := line[i]
+		switch {
+		case c == '"':
+			inQuote = !inQuote
+			seg.WriteByte(c)
+			i++
+		case inQuote:
+			seg.WriteByte(c)
+			i++
+		case c == ';':
+			segments, separators = appendSegment(segments, separators, &seg, ";")
+			i++
+		case c == '&' && i+1 < len(line) && line[i+1] == '&':
+			segments, separators = appendSegment(segments, separators, &seg, "&&")
+			i += 2
+		case c == '|' && i+1 < len(line) && line[i+1] == '|':
+			segments, separators = appendSegment(segments, separators, &seg, "||")
+			i += 2
+		default:
+			seg.WriteByte(c)
+			i++
+		}
+	}
+	if seg.Len() > 0 {
+		s := strings.TrimSpace(seg.String())
+		if s != "" {
+			segments = append(segments, s)
+		}
+	}
+	return segments, separators
+}
+
+func appendSegment(segments, separators []string, seg *strings.Builder, sep string) (newSegments, newSeparators []string) {
+	s := strings.TrimSpace(seg.String())
+	if s != "" {
+		segments = append(segments, s)
+		separators = append(separators, sep)
+	}
+	seg.Reset()
+	return segments, separators
+}
+
+// runInteractiveSegments runs segments with short-circuit semantics. separators[i]
+// is between segments[i] and segments[i+1]. Returns (exit, finalCwd, finalPkg).
+func runInteractiveSegments(segments, separators []string, cwd, currentPackage string) (exit bool, finalCwd, finalPkg string) {
+	for i, seg := range segments {
+		cmd, args, flags := parseInteractiveLine(seg)
+		if cmd == "" {
+			continue
+		}
+		newCurrent, changed, didExit, newCwd, err := runInteractiveOne(cmd, args, flags, currentPackage, cwd)
+		if didExit {
+			return true, "", ""
+		}
+		if err != nil {
+			_, _ = fmt.Fprintf(getInteractiveStderr(), "%v\n", err)
+			if i < len(separators) && separators[i] == "&&" {
+				return false, cwd, currentPackage
+			}
+			continue
+		}
+		cwd, currentPackage = applyInteractiveCwdAndPkg(cwd, newCwd, currentPackage, newCurrent, changed)
+		if i < len(separators) && separators[i] == "||" {
+			return false, cwd, currentPackage
+		}
+	}
+	return false, cwd, currentPackage
+}
+
+// parseInteractiveLine tokenizes a line: first token is the command, remaining tokens
+// are args. Flags --name=value or --name value (and -o value) are extracted into a map
+// and removed from args. Double-quoted strings are supported.
+func parseInteractiveLine(line string) (cmd string, args []string, flags map[string]string) {
+	flags = make(map[string]string)
+	tokens := tokenizeLine(line)
+	if len(tokens) == 0 {
+		return "", nil, flags
+	}
+	cmd = tokens[0]
+	var rest []string
+	i := 1
+	for i < len(tokens) {
+		t := tokens[i]
+		key, value, nextI := consumeInteractiveFlag(tokens, i)
+		if key != "" {
+			flags[key] = value
+			i = nextI
+			continue
+		}
+		rest = append(rest, t)
+		i++
+	}
+	return cmd, rest, flags
+}
+
+func consumeInteractiveFlag(tokens []string, i int) (key, value string, nextI int) {
+	if i >= len(tokens) {
+		return "", "", i
+	}
+	t := tokens[i]
+	for _, def := range interactiveFlags {
+		for _, name := range def.names {
+			if t == name && i+1 < len(tokens) {
+				return def.key, tokens[i+1], i + 2
+			}
+			if strings.HasPrefix(t, name+"=") {
+				return def.key, t[len(name)+1:], i + 1
+			}
+		}
+	}
+	return "", "", i
+}
+
+func tokenizeLine(line string) []string {
+	var tokens []string
+	var b strings.Builder
+	inQuote := false
+	for i := 0; i < len(line); i++ {
+		c := line[i]
+		switch {
+		case inQuote:
+			if c == '"' {
+				inQuote = false
+				tokens = append(tokens, b.String())
+				b.Reset()
+			} else {
+				b.WriteByte(c)
+			}
+		case c == '"':
+			inQuote = true
+		case c == ' ' || c == '\t':
+			if b.Len() > 0 {
+				tokens = append(tokens, b.String())
+				b.Reset()
+			}
+		default:
+			b.WriteByte(c)
+		}
+	}
+	if b.Len() > 0 {
+		tokens = append(tokens, b.String())
+	}
+	return tokens
+}
+
+func printInteractiveHelp(w io.Writer) {
+	const cmdWidth = 28
+	pad := func(cmd, desc string) string {
+		if len(cmd) >= cmdWidth {
+			return cmd + "  " + desc
+		}
+		return cmd + strings.Repeat(" ", cmdWidth-len(cmd)) + desc
+	}
+	_, _ = fmt.Fprintln(w, "Commands:")
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "  Session and working directory:")
+	_, _ = fmt.Fprintln(w, "    "+pad("pwd", "Print current working directory"))
+	_, _ = fmt.Fprintln(w, "    "+pad("cd [dir]", "Change directory (no arg => home)"))
+	_, _ = fmt.Fprintln(w, "    "+pad("ls [dir]", "List local dir (default: cwd)"))
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "  Current package:")
+	_, _ = fmt.Fprintln(w, "    "+pad("open [--read-only] <path>", "Set current package"))
+	_, _ = fmt.Fprintln(w, "    "+pad("close", "Clear current package"))
+	_, _ = fmt.Fprintln(w, "    "+pad("create <path>", "Create empty package and open it"))
+	_, _ = fmt.Fprintln(w, "    "+pad("write [--overwrite false]", "Persist to disk (default overwrite=true)"))
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "  Package metadata:")
+	_, _ = fmt.Fprintln(w, "    "+pad("comment [--set \"...\" | --clear]", "Get/set/clear comment (use 'write' to persist)"))
+	_, _ = fmt.Fprintln(w, "    "+pad("identity [--vendor-id N] [--app-id N]", "Get/set Vendor ID and App ID"))
+	_, _ = fmt.Fprintln(w, "    "+pad("info [path]", "Show package info"))
+	_, _ = fmt.Fprintln(w, "    "+pad("header [path]", "Print raw header"))
+	_, _ = fmt.Fprintln(w, "    "+pad("validate [path]", "Validate integrity"))
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "  Package contents:")
+	_, _ = fmt.Fprintln(w, "    "+pad("list [path]", "List contents"))
+	_, _ = fmt.Fprintln(w, "    "+pad("add [src]... [path]", "Add file(s)/dir(s)"))
+	_, _ = fmt.Fprintln(w, "    "+pad("remove [path] <internal>", "Remove file/dir (--pattern for glob)"))
+	_, _ = fmt.Fprintln(w, "    "+pad("read [path] <internal>", "Read entry (-o file to extract to file)"))
+	_, _ = fmt.Fprintln(w, "    "+pad("extract [path] [internal]", "Extract (-o dir required)"))
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "  Other:")
+	_, _ = fmt.Fprintln(w, "    "+pad("help", "This message"))
+	_, _ = fmt.Fprintln(w, "    "+pad("quit, exit, q", "Exit"))
+	_, _ = fmt.Fprintln(w, "")
+	_, _ = fmt.Fprintln(w, "Chain: ; (run all)  && (stop on error)  || (stop on success).  # comment.")
+}
diff --git a/cli/nvpkg/cmd/interactive_test.go b/cli/nvpkg/cmd/interactive_test.go
new file mode 100644
index 00000000..f3b80487
--- /dev/null
+++ b/cli/nvpkg/cmd/interactive_test.go
@@ -0,0 +1,1563 @@
+package cmd
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/creack/pty"
+	novuspack "github.com/novus-engine/novuspack/api/go"
+)
+
+const (
+	testPkgName = "p.nvpk"
+	testCwdTmp  = "/tmp"
+)
+
+func TestTokenizeLine(t *testing.T) {
+	tests := []struct {
+		line string
+		want []string
+	}{
+		{"", nil},
+		{"  ", nil},
+		{"a", []string{"a"}},
+		{"a b", []string{"a", "b"}},
+		{"open pkg.nvpk", []string{"open", "pkg.nvpk"}},
+		{`add "file with spaces.txt"`, []string{"add", "file with spaces.txt"}},
+		{`add pkg.nvpk "path with spaces"`, []string{"add", "pkg.nvpk", "path with spaces"}},
+	}
+	for _, tt := range tests {
+		got := tokenizeLine(tt.line)
+		if len(got) != len(tt.want) {
+			t.Errorf("tokenizeLine(%q) => %q, want %q", tt.line, got, tt.want)
+			continue
+		}
+		for i := range got {
+			if got[i] != tt.want[i] {
+				t.Errorf("tokenizeLine(%q)[%d] => %q, want %q", tt.line, i, got[i], tt.want[i])
+			}
+		}
+	}
+}
+
+func TestParseInteractiveLine(t *testing.T) {
+	t.Run("quit", func(t *testing.T) {
+		cmd, args, flags := parseInteractiveLine("quit")
+		assertParseResult(t, "quit", cmd, args, flags, "quit", nil, nil)
+	})
+	t.Run("open", func(t *testing.T) {
+		cmd, args, flags := parseInteractiveLine("open pkg.nvpk")
+		assertParseResult(t, "open pkg.nvpk", cmd, args, flags, "open", []string{"pkg.nvpk"}, nil)
+	})
+	t.Run("add_with_as", func(t *testing.T) {
+		cmd, args, flags := parseInteractiveLine("add f1 pkg.nvpk --as /x")
+		assertParseResult(t, "add", cmd, args, flags, "add", []string{"f1", "pkg.nvpk"}, map[string]string{"as": "/x"})
+	})
+	t.Run("read_with_output", func(t *testing.T) {
+		cmd, args, flags := parseInteractiveLine("read pkg.nvpk /config.json -o out.json")
+		assertParseResult(t, "read", cmd, args, flags, "read", []string{"pkg.nvpk", "/config.json"}, map[string]string{"output": "out.json"})
+	})
+	t.Run("create_with_comment", func(t *testing.T) {
+		cmd, args, flags := parseInteractiveLine("create out.nvpk --comment hello")
+		assertParseResult(t, "create", cmd, args, flags, "create", []string{"out.nvpk"}, map[string]string{"comment": "hello"})
+	})
+}
+
+func assertParseResult(t *testing.T, line, cmd string, args []string, flags map[string]string, wantCmd string, wantArgs []string, wantFlags map[string]string) {
+	t.Helper()
+	if cmd != wantCmd {
+		t.Errorf("parseInteractiveLine(%q) cmd => %q, want %q", line, cmd, wantCmd)
+	}
+	if len(args) != len(wantArgs) {
+		t.Errorf("parseInteractiveLine(%q) args => %q, want %q", line, args, wantArgs)
+	} else {
+		for i := range args {
+			if args[i] != wantArgs[i] {
+				t.Errorf("parseInteractiveLine(%q) args[%d] => %q, want %q", line, i, args[i], wantArgs[i])
+			}
+		}
+	}
+	if wantFlags == nil {
+		wantFlags = map[string]string{}
+	}
+	for k, v := range wantFlags {
+		if flags[k] != v {
+			t.Errorf("parseInteractiveLine(%q) flags[%q] => %q, want %q", line, k, flags[k], v)
+		}
+	}
+}
+
+// nvpkgDir returns the nvpkg module root (directory containing go.mod for this CLI).
+func nvpkgDir(t *testing.T) string {
+	t.Helper()
+	_, file, _, ok := runtime.Caller(0)
+	if !ok {
+		t.Fatal("runtime.Caller(0) failed")
+	}
+	return filepath.Dir(filepath.Dir(file)) // interactive_test.go -> cmd -> nvpkg
+}
+
+// runInteractiveWithInput runs the interactive REPL with scripted stdin and captures stdout/stderr.
+func runInteractiveWithInput(t *testing.T, input string) (stdout, stderr string, err error) {
+	t.Helper()
+	var outBuf, errBuf bytes.Buffer
+	InteractiveStdin = strings.NewReader(input)
+	InteractiveStdout = &outBuf
+	InteractiveStderr = &errBuf
+	defer func() {
+		InteractiveStdin = nil
+		InteractiveStdout = nil
+		InteractiveStderr = nil
+	}()
+	err = runInteractive(nil, nil)
+	return outBuf.String(), errBuf.String(), err
+}
+
+// TestRunInteractive_WithPty runs the interactive command in a subprocess with a pseudoterminal
+// so that the liner (TTY) path is used. It covers runInteractiveWithLiner and getInteractiveStdin
+// returning os.Stdin in the child process.
+func TestRunInteractive_WithPty(t *testing.T) {
+	if runtime.GOOS == "windows" {
+		t.Skip("pty test is Unix-only")
+	}
+	dir := nvpkgDir(t)
+	cmd := exec.Command("go", "run", ".", "interactive")
+	cmd.Dir = dir
+	cmd.Env = append(os.Environ(), "TERM=dumb")
+	master, err := pty.Start(cmd)
+	if err != nil {
+		if err == pty.ErrUnsupported {
+			t.Skip("pty unsupported on this system:", err)
+		}
+		t.Fatalf("pty.Start: %v", err)
+	}
+	defer func() { _ = master.Close() }()
+
+	var outBuf bytes.Buffer
+	go func() { _, _ = io.Copy(&outBuf, master) }()
+
+	// Send help then quit so we exercise the liner loop and see help output.
+	if _, err := master.WriteString("help\n"); err != nil {
+		t.Fatalf("write help: %v", err)
+	}
+	time.Sleep(100 * time.Millisecond)
+	if _, err := master.WriteString("quit\n"); err != nil {
+		t.Fatalf("write quit: %v", err)
+	}
+	if err := cmd.Wait(); err != nil {
+		t.Fatalf("cmd.Wait: %v", err)
+	}
+	out := outBuf.String()
+	if !strings.Contains(out, "nvpkg>") {
+		t.Errorf("pty output missing prompt: %q", out)
+	}
+	if !strings.Contains(out, "Commands:") {
+		t.Errorf("pty output missing help: %q", out)
+	}
+}
+
+// assertInteractiveOK runs the REPL with input and asserts no error; optionally checks stderr/stdout.
+func assertInteractiveOK(t *testing.T, input, stderrContains, stdoutContains string) {
+	t.Helper()
+	stdout, stderr, err := runInteractiveWithInput(t, input)
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stderrContains != "" && !strings.Contains(stderr, stderrContains) {
+		t.Errorf("stderr missing %q: %q", stderrContains, stderr)
+	}
+	if stdoutContains != "" && !strings.Contains(stdout, stdoutContains) {
+		t.Errorf("stdout missing %q: %q", stdoutContains, stdout)
+	}
+}
+
+func assertInteractiveStderrOnly(t *testing.T, input, stderrContains string) {
+	t.Helper()
+	_, stderr, err := runInteractiveWithInput(t, input)
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, stderrContains) {
+		t.Errorf("stderr missing %q: %q", stderrContains, stderr)
+	}
+}
+
+func assertInteractiveCreateFile(t *testing.T, input, pkgPath string) {
+	t.Helper()
+	_, stderr, err := runInteractiveWithInput(t, input)
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stderr != "" {
+		t.Errorf("stderr: %q", stderr)
+	}
+	if _, statErr := os.Stat(pkgPath); statErr != nil {
+		t.Errorf("package not created: %v", statErr)
+	}
+}
+
+func TestRunInteractive_HelpQuit(t *testing.T) {
+	assertInteractiveOK(t, "help\nquit\n", "", "Commands:")
+	assertInteractiveOK(t, "help\nquit\n", "", "Set current package")
+	assertInteractiveOK(t, "help\nquit\n", "", "quit")
+}
+
+func TestRunInteractive_Exit(t *testing.T) {
+	_, _, err := runInteractiveWithInput(t, "exit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+}
+
+func TestRunInteractive_OpenCloseQuit(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	assertInteractiveOK(t, "open "+pkgPath+"\nclose\nquit\n", "", "Current package: ")
+	assertInteractiveOK(t, "open "+pkgPath+"\nclose\nquit\n", "", "No current package")
+}
+
+func TestRunInteractive_OpenNoArg(t *testing.T) {
+	assertInteractiveStderrOnly(t, "open\nquit\n", "open: requires package path")
+}
+
+func TestRunInteractive_PwdQuit(t *testing.T) {
+	assertInteractiveOK(t, "pwd\nquit\n", "", "nvpkg>")
+}
+
+func TestRunInteractive_CdQuit(t *testing.T) {
+	stdout, _, err := runInteractiveWithInput(t, "cd .\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stdout == "" {
+		t.Error("expected cd output")
+	}
+}
+
+func TestRunInteractive_CdHomeQuit(t *testing.T) {
+	stdout, _, err := runInteractiveWithInput(t, "cd\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stdout == "" {
+		t.Error("expected cd (home) output")
+	}
+}
+
+func TestRunInteractive_LsQuit(t *testing.T) {
+	assertInteractiveOK(t, "ls\nquit\n", "", "nvpkg>")
+}
+
+func TestRunInteractive_CreateQuit(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "out.nvpk")
+	assertInteractiveCreateFile(t, "create "+pkgPath+"\nquit\n", pkgPath)
+}
+
+func TestRunInteractive_CdThenCreateUsesNewDir(t *testing.T) {
+	origWd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("getwd: %v", err)
+	}
+	dir := t.TempDir()
+	sub := filepath.Join(dir, "sub")
+	if err := os.Mkdir(sub, 0o755); err != nil {
+		t.Fatalf("mkdir sub: %v", err)
+	}
+	defer func() { _ = os.Chdir(origWd) }()
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("chdir to dir: %v", err)
+	}
+	// cd into sub, create with relative path; file must appear in sub/
+	pkgPath := filepath.Join(sub, "p.nvpk")
+	assertInteractiveCreateFile(t, "cd sub\ncreate p.nvpk\nquit\n", pkgPath)
+}
+
+func TestRunInteractive_UnknownCommand(t *testing.T) {
+	assertInteractiveStderrOnly(t, "unknowncmd\nquit\n", "Unknown command")
+}
+
+func TestRunInteractive_ListWithOpenPackage(t *testing.T) {
+	pkgPath := createTestPackage(t, "list.nvpk")
+	assertInteractiveOK(t, "open "+pkgPath+"\nlist\nquit\n", "", "Current package:")
+}
+
+func TestRunInteractive_InfoWithOpenPackage(t *testing.T) {
+	pkgPath := createTestPackage(t, "info.nvpk")
+	assertInteractiveOK(t, "open "+pkgPath+"\ninfo\nquit\n", "", "Current package:")
+}
+
+func TestRunInteractive_AddNoSources(t *testing.T) {
+	pkgPath := createTestPackage(t, "adderr.nvpk")
+	assertInteractiveStderrOnly(t, "open "+pkgPath+"\nadd\nquit\n", "add: requires")
+}
+
+func TestRunInteractive_RemoveNoPath(t *testing.T) {
+	pkgPath := createTestPackage(t, "removeerr.nvpk")
+	assertInteractiveStderrOnly(t, "open "+pkgPath+"\nremove\nquit\n", "remove: requires")
+}
+
+func TestRunInteractive_ReadNoPath(t *testing.T) {
+	pkgPath := createTestPackage(t, "readerr.nvpk")
+	assertInteractiveStderrOnly(t, "open "+pkgPath+"\nread\nquit\n", "read: requires")
+}
+
+func TestRunInteractive_ListNoPackage(t *testing.T) {
+	assertInteractiveStderrOnly(t, "list\nquit\n", "No current package")
+}
+
+func TestRunInteractive_CreateNoPath(t *testing.T) {
+	assertInteractiveStderrOnly(t, "create\nquit\n", "create: requires")
+}
+
+func TestRunInteractive_CreateOpensPackage(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "new.nvpk")
+	stdout, stderr, err := runInteractiveWithInput(t, "create "+pkgPath+"\nlist\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stderr != "" {
+		t.Errorf("stderr: %q", stderr)
+	}
+	if !strings.Contains(stdout, "Current package:") {
+		t.Errorf("create should open package; stdout %q", stdout)
+	}
+	if !strings.Contains(stdout, pkgPath) {
+		t.Errorf("stdout should show package path %q: %q", pkgPath, stdout)
+	}
+}
+
+func TestRunInteractive_AddFile(t *testing.T) {
+	runInteractiveAddFlow(t, "p.nvpk", "f.txt", "hi", "open %s\nadd %s\nquit\n", "Added ")
+}
+
+func TestRunInteractive_CreateWithComment(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "c.nvpk")
+	assertInteractiveCreateFile(t, "create "+pkgPath+" --comment hello\nquit\n", pkgPath)
+}
+
+func TestRunInteractive_CreateWithVendorAndAppId(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "v.nvpk")
+	assertInteractiveCreateFile(t, "create "+pkgPath+" --vendor-id 1 --app-id 100\nquit\n", pkgPath)
+}
+
+func TestRunInteractive_HeaderWithOpenPackage(t *testing.T) {
+	pkgPath := createTestPackage(t, "h.nvpk")
+	assertInteractiveOK(t, "open "+pkgPath+"\nheader\nquit\n", "", "Current package:")
+}
+
+func TestRunInteractive_ValidateWithOpenPackage(t *testing.T) {
+	pkgPath := createTestPackage(t, "v.nvpk")
+	_, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\nvalidate\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	// runValidate writes to os.Stdout, not injected buffer; we only assert no error
+}
+
+func TestRunInteractive_ValidateWithExplicitPath(t *testing.T) {
+	pkgPath := createTestPackage(t, "vp.nvpk")
+	_, _, err := runInteractiveWithInput(t, "validate "+pkgPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	// runValidate writes to os.Stdout, not injected buffer; we only assert no error
+}
+
+func TestRunInteractive_ValidateNoPackage(t *testing.T) {
+	_, stderr, err := runInteractiveWithInput(t, "validate\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "No current package") {
+		t.Errorf("validate with no package: stderr %q should contain 'No current package'", stderr)
+	}
+}
+
+func TestRunInteractive_CommentNoPackage(t *testing.T) {
+	_, stderr, err := runInteractiveWithInput(t, "comment\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "No current package") {
+		t.Errorf("comment with no package: stderr %q should contain 'No current package'", stderr)
+	}
+}
+
+func TestRunInteractive_CommentGetAndSet(t *testing.T) {
+	pkgPath := createTestPackage(t, "comment.nvpk")
+	stdout, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\ncomment\ncomment --set hello\ncomment\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "(no comment)") {
+		t.Errorf("comment get (no comment): stdout %q should contain '(no comment)'", stdout)
+	}
+	if !strings.Contains(stdout, "Comment set") {
+		t.Errorf("comment --set: stdout %q should contain 'Comment set'", stdout)
+	}
+	if !strings.Contains(stdout, "hello") {
+		t.Errorf("comment get after set: stdout %q should contain 'hello'", stdout)
+	}
+}
+
+func TestRunInteractive_IdentityNoPackage(t *testing.T) {
+	_, stderr, err := runInteractiveWithInput(t, "identity\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "No current package") {
+		t.Errorf("identity with no package: stderr %q should contain 'No current package'", stderr)
+	}
+}
+
+func TestRunInteractive_IdentityGetAndSet(t *testing.T) {
+	pkgPath := createTestPackage(t, "identity.nvpk")
+	stdout, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\nidentity\nidentity --vendor-id 1 --app-id 100\nidentity\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "Vendor ID:") || !strings.Contains(stdout, "App ID:") {
+		t.Errorf("identity get: stdout %q should contain Vendor ID and App ID", stdout)
+	}
+	if !strings.Contains(stdout, "Identity updated") {
+		t.Errorf("identity set: stdout %q should contain 'Identity updated'", stdout)
+	}
+	if !strings.Contains(stdout, "Vendor ID: 1") || !strings.Contains(stdout, "App ID:") || !strings.Contains(stdout, "100") {
+		t.Errorf("identity get after set: stdout %q should contain Vendor ID: 1 and App ID 100", stdout)
+	}
+}
+
+func TestRunInteractive_RemoveRequiresPath(t *testing.T) {
+	pkgPath := createTestPackage(t, "rm_nopath.nvpk")
+	_, stderr, err := runInteractiveWithInput(t, "open "+pkgPath+"\nremove\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "remove: requires") {
+		t.Errorf("remove with no path: stderr %q should contain 'remove: requires'", stderr)
+	}
+}
+
+// assertStubRemoveAccept runs open+remove+quit; passes if success or if error/stderr contains any of acceptableSubstrings.
+// Used when the remove API is stubbed (pattern or directory) so we accept success or a known error message.
+func assertStubRemoveAccept(t *testing.T, pkgName, removeCmd string, acceptableSubstrings []string) {
+	t.Helper()
+	pkgPath := createTestPackage(t, pkgName)
+	input := "open " + pkgPath + "\n" + removeCmd + "\nquit\n"
+	_, stderr, err := runInteractiveWithInput(t, input)
+	if err == nil {
+		return
+	}
+	for _, sub := range acceptableSubstrings {
+		if strings.Contains(err.Error(), sub) || strings.Contains(stderr, sub) {
+			return
+		}
+	}
+	t.Fatalf("runInteractive: %v (stderr: %q)", err, stderr)
+}
+
+func TestRunInteractive_RemoveStubAccept(t *testing.T) {
+	for _, tt := range []struct {
+		name                 string
+		pkgName, removeCmd   string
+		acceptableSubstrings []string
+	}{
+		{"pattern", "rm_pat.nvpk", "remove --pattern *.tmp", []string{"unsupported", "remove pattern"}},
+		{"directory", "rm_dir.nvpk", "remove /sub/", []string{"unsupported", "remove directory"}},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			assertStubRemoveAccept(t, tt.pkgName, tt.removeCmd, tt.acceptableSubstrings)
+		})
+	}
+}
+
+// assertInfoShows runs create+open+info+quit with createFlags; fails if stdout does not contain all wantSubstrings.
+func assertInfoShows(t *testing.T, createFlags string, wantSubstrings []string) {
+	t.Helper()
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "info_show.nvpk")
+	input := "create " + pkgPath + " " + createFlags + "\nopen " + pkgPath + "\ninfo\nquit\n"
+	stdout, _, err := runInteractiveWithInput(t, input)
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	for _, sub := range wantSubstrings {
+		if !strings.Contains(stdout, sub) {
+			t.Errorf("stdout %q should contain %q", stdout, sub)
+		}
+	}
+}
+
+func TestRunInteractive_InfoShows(t *testing.T) {
+	for _, tt := range []struct {
+		name           string
+		createFlags    string
+		wantSubstrings []string
+	}{
+		{"comment_only", "--comment only", []string{"Comment", "only"}},
+		{"vendor_app_id", "--vendor-id 1 --app-id 100", []string{"Vendor ID", "App ID"}},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			assertInfoShows(t, tt.createFlags, tt.wantSubstrings)
+		})
+	}
+}
+
+func TestRunInteractive_CdInvalidPath(t *testing.T) {
+	assertInteractiveStderrOnly(t, "cd /nonexistentpath12345\nquit\n", "cd:")
+}
+
+func TestFormatFileSize(t *testing.T) {
+	tests := []struct {
+		n    int64
+		want string
+	}{
+		{0, "0"},
+		{42, "42"},
+		{1024, "1.0K"},
+		{1536, "1.5K"},
+		{1024 * 1024, "1.0M"},
+		{1024 * 1024 * 1024, "1.0G"},
+		{1024 * 1024 * 1024 * 1024, "1.0T"},
+	}
+	for _, tt := range tests {
+		got := formatFileSize(tt.n)
+		if got != tt.want {
+			t.Errorf("formatFileSize(%d) => %q, want %q", tt.n, got, tt.want)
+		}
+	}
+}
+
+func TestExpandTilde(t *testing.T) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skip("UserHomeDir:", err)
+	}
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"", ""},
+		{"/foo", "/foo"},
+		{"foo", "foo"},
+		{"~", home},
+		{"~/", filepath.Join(home, "")},
+		{"~/x", filepath.Join(home, "x")},
+		{"~/a/b", filepath.Join(home, "a", "b")},
+		{"~other", "~other"},
+		{"~x", "~x"}, // tilde not followed by /: return unchanged
+	}
+	for _, tt := range tests {
+		got := expandTilde(tt.path)
+		if got != tt.want {
+			t.Errorf("expandTilde(%q) => %q, want %q", tt.path, got, tt.want)
+		}
+	}
+}
+
+func TestResolveAddArgs(t *testing.T) {
+	t.Run("with_current_package", func(t *testing.T) {
+		pkg, src := resolveAddArgs([]string{"f1", "f2"}, testPkgName)
+		if pkg != testPkgName || len(src) != 2 || src[0] != "f1" || src[1] != "f2" {
+			t.Errorf("resolveAddArgs([f1 f2], %s) => %q, %q", testPkgName, pkg, src)
+		}
+	})
+	t.Run("no_package_two_args", func(t *testing.T) {
+		pkg, src := resolveAddArgs([]string{"f1", testPkgName}, "")
+		if pkg != testPkgName || len(src) != 1 || src[0] != "f1" {
+			t.Errorf("resolveAddArgs([f1 %s], ) => %q, %q", testPkgName, pkg, src)
+		}
+	})
+	t.Run("no_package_one_arg", func(t *testing.T) {
+		pkg, src := resolveAddArgs([]string{"f1"}, "")
+		if pkg != "" || len(src) != 1 {
+			t.Errorf("resolveAddArgs([f1], ) => pkg=%q want empty, src=%q", pkg, src)
+		}
+	})
+}
+
+func TestRunInteractive_AddWithPathLast(t *testing.T) {
+	_, pkgPath, f := createDirWithPkgAndFile(t, "p.nvpk", "f.txt", "hi")
+	_, _, err := runInteractiveWithInput(t, "add "+f+" "+pkgPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+}
+
+// createDirWithPkgAndFile creates a temp dir, an empty package, and a file; returns (dir, pkgPath, filePath).
+func createDirWithPkgAndFile(t *testing.T, pkgName, fileName, fileContent string) (dir, pkgPath, filePath string) {
+	t.Helper()
+	dir = t.TempDir()
+	pkgPath = filepath.Join(dir, pkgName)
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	filePath = filepath.Join(dir, fileName)
+	if err := os.WriteFile(filePath, []byte(fileContent), 0o644); err != nil {
+		t.Fatalf("write: %v", err)
+	}
+	return dir, pkgPath, filePath
+}
+
+func TestRunInteractive_AddNoPackageOneArg(t *testing.T) {
+	dir := t.TempDir()
+	f := filepath.Join(dir, "f.txt")
+	_ = os.WriteFile(f, []byte("x"), 0o644)
+	assertInteractiveStderrOnly(t, "add "+f+"\nquit\n", "No current package")
+}
+
+func TestProcessLinerLine_Quit(t *testing.T) {
+	exit, _, _ := processLinerLine("quit", testCwdTmp, "")
+	if !exit {
+		t.Error("processLinerLine(quit) => exit false, want true")
+	}
+}
+
+func TestProcessLinerLine_Help(t *testing.T) {
+	exit, cwd, pkg := processLinerLine("help", testCwdTmp, "")
+	if exit {
+		t.Error("processLinerLine(help) => exit true, want false")
+	}
+	if cwd != testCwdTmp || pkg != "" {
+		t.Errorf("processLinerLine(help) => cwd=%q pkg=%q", cwd, pkg)
+	}
+}
+
+func TestProcessLinerLine_Open(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	exit, newCwd, newPkg := processLinerLine("open "+pkgPath, testCwdTmp, "")
+	if exit {
+		t.Error("processLinerLine(open) => exit true, want false")
+	}
+	if newPkg != pkgPath {
+		t.Errorf("processLinerLine(open) => newPkg=%q, want %q", newPkg, pkgPath)
+	}
+	_ = newCwd
+}
+
+func TestProcessLinerLine_Write(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "w.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	exit, _, _ := processLinerLine("open "+pkgPath+"\nwrite", testCwdTmp, "")
+	if exit {
+		t.Error("processLinerLine(open) => exit true")
+	}
+	exit, _, _ = processLinerLine("write", testCwdTmp, pkgPath)
+	if exit {
+		t.Error("processLinerLine(write) => exit true")
+	}
+}
+
+func TestProcessLinerLine_Close(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "c.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	_, _, pkg := processLinerLine("open "+pkgPath, testCwdTmp, "")
+	if pkg != pkgPath {
+		t.Fatalf("after open: pkg=%q", pkg)
+	}
+	exit, _, finalPkg := processLinerLine("close", testCwdTmp, pkgPath)
+	if exit {
+		t.Error("processLinerLine(close) => exit true, want false")
+	}
+	if finalPkg != "" {
+		t.Errorf("after close: finalPkg=%q, want empty", finalPkg)
+	}
+}
+
+func TestProcessLinerLine_ErrorFromHandler(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "e.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	// add with nonexistent source should return error from handler
+	_, _, pkg := processLinerLine("open "+pkgPath, dir, "")
+	if pkg == "" {
+		t.Fatalf("open failed")
+	}
+	_, finalCwd, finalPkg := processLinerLine("add "+filepath.Join(dir, "nonexistent.txt"), dir, pkg)
+	// on error we keep cwd and currentPackage
+	if finalPkg != pkg {
+		t.Errorf("on error: finalPkg=%q, want %q", finalPkg, pkg)
+	}
+	_ = finalCwd
+}
+
+func TestCompleteCommands_MultipleAndNone(t *testing.T) {
+	got := completeCommands("c")
+	if len(got) < 2 {
+		t.Errorf("completeCommands(\"c\") => %q, want at least [\"cd\", \"close\", \"create\"]", got)
+	}
+	got = completeCommands("zzz")
+	if len(got) != 0 {
+		t.Errorf("completeCommands(\"zzz\") => %q, want []", got)
+	}
+}
+
+func TestInteractiveCompleter_Commands(t *testing.T) {
+	completerCwd = t.TempDir()
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("")
+	if len(got) == 0 {
+		t.Error("interactiveCompleter(\"\") => empty, want command list")
+	}
+	got = interactiveCompleter("op")
+	if len(got) != 1 || got[0] != "open" {
+		t.Errorf("interactiveCompleter(\"op\") => %q, want [\"open\"]", got)
+	}
+	got = interactiveCompleter("w")
+	if len(got) != 1 || got[0] != "write" {
+		t.Errorf("interactiveCompleter(\"w\") => %q, want [\"write\"]", got)
+	}
+	// Full-line: "cd c" => "cd cli/" (preserves command)
+	dir := t.TempDir()
+	_ = os.MkdirAll(filepath.Join(dir, "cli"), 0o755)
+	completerCwd = dir
+	got = interactiveCompleter("cd c")
+	if len(got) != 1 || got[0] != "cd cli"+string(filepath.Separator) {
+		t.Errorf("interactiveCompleter(\"cd c\") => %q, want [\"cd cli/\"]", got)
+	}
+}
+
+func TestInteractiveCompleter_Path(t *testing.T) {
+	dir := t.TempDir()
+	completerCwd = dir
+	defer func() { completerCwd = "" }()
+	_ = os.WriteFile(filepath.Join(dir, "foo.txt"), []byte("x"), 0o644)
+	_ = os.WriteFile(filepath.Join(dir, "bar.txt"), []byte("y"), 0o644)
+	got := interactiveCompleter("open f")
+	if len(got) != 1 || got[0] != "open foo.txt" {
+		t.Errorf("interactiveCompleter(\"open f\") => %q, want [\"open foo.txt\"]", got)
+	}
+}
+
+func TestInteractiveCompleter_PathEmptyLastToken(t *testing.T) {
+	dir := t.TempDir()
+	_ = os.MkdirAll(filepath.Join(dir, "sub"), 0o755)
+	completerCwd = dir
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("open ")
+	if len(got) == 0 {
+		t.Error("interactiveCompleter(\"open \") => empty, want dir entries")
+	}
+	// Full-line: each candidate is "open " + entry
+	for _, c := range got {
+		if !strings.HasPrefix(c, "open ") {
+			t.Errorf("interactiveCompleter(\"open \") => %q, each should start with \"open \"", c)
+		}
+	}
+}
+
+func TestInteractiveCompleter_NonPathCommand(t *testing.T) {
+	completerCwd = t.TempDir()
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("help x")
+	if got != nil {
+		t.Errorf("interactiveCompleter(\"help x\") => %q, want nil", got)
+	}
+}
+
+func TestInteractiveCompleter_PathWithSubdir(t *testing.T) {
+	dir := t.TempDir()
+	sub := filepath.Join(dir, "sub")
+	if err := os.MkdirAll(sub, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	_ = os.WriteFile(filepath.Join(sub, "foo.txt"), []byte("x"), 0o644)
+	completerCwd = dir
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("open sub")
+	if len(got) == 0 {
+		t.Error("interactiveCompleter(\"open sub\") => empty, want subdir completion")
+	}
+	// Full-line: candidate should be "open sub/..." (with path separator)
+	for _, c := range got {
+		if !strings.HasPrefix(c, "open sub") {
+			t.Errorf("interactiveCompleter(\"open sub\") => %q, each should start with \"open sub\"", c)
+		}
+	}
+}
+
+func TestParseInteractiveLine_Flags(t *testing.T) {
+	tests := []struct {
+		line     string
+		wantCmd  string
+		wantArg0 string
+		wantFlag string
+		wantVal  string
+	}{
+		{"add f --as=/internal/path", "add", "f", "as", "/internal/path"},
+		{"read /x -o out.txt", "read", "/x", "output", "out.txt"},
+	}
+	for _, tt := range tests {
+		cmd, args, flags := parseInteractiveLine(tt.line)
+		if cmd != tt.wantCmd || len(args) != 1 || args[0] != tt.wantArg0 || flags[tt.wantFlag] != tt.wantVal {
+			t.Errorf("parseInteractiveLine(%q) => cmd=%q args=%v flags[%q]=%q, want cmd=%q arg0=%q %q=%q",
+				tt.line, cmd, args, tt.wantFlag, flags[tt.wantFlag], tt.wantCmd, tt.wantArg0, tt.wantFlag, tt.wantVal)
+		}
+	}
+}
+
+func TestParseInteractiveLine_FlagAtEndNoValue(t *testing.T) {
+	// Flag at end of line has no value; not consumed, remains in args
+	cmd, args, flags := parseInteractiveLine("add --as")
+	if cmd != "add" {
+		t.Errorf("parseInteractiveLine(\"add --as\") => cmd=%q, want add", cmd)
+	}
+	if len(args) != 1 || args[0] != "--as" {
+		t.Errorf("parseInteractiveLine(\"add --as\") => args=%v, want [--as]", args)
+	}
+	if flags["as"] != "" {
+		t.Errorf("parseInteractiveLine(\"add --as\") => flags[as]=%q, want empty", flags["as"])
+	}
+}
+
+func TestStripComment(t *testing.T) {
+	tests := []struct {
+		line string
+		want string
+	}{
+		{"help", "help"},
+		{"help # rest", "help"},
+		{"help #", "help"},
+		{"# full comment", ""},
+		{"  #", ""},
+		{"add f # as /x", "add f"},
+		{`add "file#path"`, `add "file#path"`},
+		{`add "file#path" # comment`, `add "file#path"`},
+		{`add "#"`, `add "#"`},
+	}
+	for _, tt := range tests {
+		got := stripComment(tt.line)
+		if got != tt.want {
+			t.Errorf("stripComment(%q) => %q, want %q", tt.line, got, tt.want)
+		}
+	}
+}
+
+func TestSplitInteractiveLine(t *testing.T) {
+	tests := []struct {
+		line       string
+		segments   []string
+		separators []string
+	}{
+		{"help", []string{"help"}, nil},
+		{"help; pwd", []string{"help", "pwd"}, []string{";"}},
+		{"help ; pwd", []string{"help", "pwd"}, []string{";"}},
+		{"help && quit", []string{"help", "quit"}, []string{"&&"}},
+		{"help || quit", []string{"help", "quit"}, []string{"||"}},
+		{"a; b; c", []string{"a", "b", "c"}, []string{";", ";"}},
+		{"a && b ; c", []string{"a", "b", "c"}, []string{"&&", ";"}},
+		{`add "f;g"`, []string{`add "f;g"`}, nil},
+		{`add "f;g"; pwd`, []string{`add "f;g"`, "pwd"}, []string{";"}},
+		{"", nil, nil},
+		{"   ", nil, nil},
+		{";;;", nil, nil},
+		{"help;;pwd", []string{"help", "pwd"}, []string{";"}},
+		{" ; help", []string{"help"}, nil},
+		{"help ; ", []string{"help"}, []string{";"}},
+	}
+	for _, tt := range tests {
+		seg, sep := splitInteractiveLine(tt.line)
+		if !slicesEqual(seg, tt.segments) || !slicesEqual(sep, tt.separators) {
+			t.Errorf("splitInteractiveLine(%q) => segments=%q separators=%q, want %q %q",
+				tt.line, seg, sep, tt.segments, tt.separators)
+		}
+	}
+}
+
+func slicesEqual(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i] != b[i] {
+			return false
+		}
+	}
+	return true
+}
+
+func TestRunInteractive_Semicolon(t *testing.T) {
+	_, _, err := runInteractiveWithInput(t, "help; pwd\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive help;pwd: %v", err)
+	}
+}
+
+func TestRunInteractive_AndAnd_StopsOnError(t *testing.T) {
+	_, stderr, err := runInteractiveWithInput(t, "unknowncmd && quit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "Unknown command") {
+		t.Errorf("stderr should contain Unknown command: %q", stderr)
+	}
+	// quit should not have run (short-circuit)
+	if strings.Contains(stderr, "quit") {
+		t.Errorf("quit should not run after failed command (stderr had quit)")
+	}
+}
+
+func TestRunInteractive_AndAnd_BothRun(t *testing.T) {
+	_, _, err := runInteractiveWithInput(t, "help && quit\n")
+	if err != nil {
+		t.Fatalf("runInteractive help && quit: %v", err)
+	}
+}
+
+func TestRunInteractive_OrOr_StopsOnSuccess(t *testing.T) {
+	// First command must return an error for || to run the second (cd to nonexistent does)
+	stdout, stderr, err := runInteractiveWithInput(t, "cd /nonexistent_xyz_123 || help\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "cd:") {
+		t.Errorf("first command (cd) should fail: stderr %q", stderr)
+	}
+	if !strings.Contains(stdout, "Commands:") && !strings.Contains(stdout, "open") {
+		t.Errorf("help should have run after cd failed: stdout %q", stdout)
+	}
+}
+
+func TestRunInteractive_CommentStripped(t *testing.T) {
+	stdout, _, err := runInteractiveWithInput(t, "help # comment\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "Commands:") && !strings.Contains(stdout, "open") {
+		t.Errorf("help should run (comment stripped): stdout %q", stdout)
+	}
+}
+
+func TestRunInteractive_ChainedSemicolon(t *testing.T) {
+	pkgPath := createTestPackage(t, "chain.nvpk")
+	_, _, err := runInteractiveWithInput(t, "open "+pkgPath+" ; list ; info\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive chained: %v", err)
+	}
+}
+
+func TestParseInteractiveLine_EmptyLine(t *testing.T) {
+	cmd, args, flags := parseInteractiveLine("")
+	if cmd != "" || args != nil || flags == nil {
+		t.Errorf("parseInteractiveLine(\"\") => cmd=%q args=%v flags=%v", cmd, args, flags)
+	}
+	cmd, args, _ = parseInteractiveLine("   \t  ")
+	if cmd != "" || len(args) != 0 {
+		t.Errorf("parseInteractiveLine(whitespace) => cmd=%q args=%v", cmd, args)
+	}
+}
+
+func TestProcessLinerLine_CdUpdatesCwd(t *testing.T) {
+	dir := t.TempDir()
+	sub := filepath.Join(dir, "sub")
+	if err := os.MkdirAll(sub, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	exit, finalCwd, _ := processLinerLine("cd "+sub, dir, "")
+	if exit {
+		t.Error("processLinerLine(cd) => exit true, want false")
+	}
+	if finalCwd != sub {
+		t.Errorf("processLinerLine(cd) => finalCwd=%q, want %q", finalCwd, sub)
+	}
+}
+
+func TestProcessLinerLine_CdNoArgGoesHome(t *testing.T) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skip("UserHomeDir:", err)
+	}
+	exit, finalCwd, _ := processLinerLine("cd", testCwdTmp, "")
+	if exit {
+		t.Error("processLinerLine(cd) => exit true, want false")
+	}
+	if finalCwd != home {
+		t.Errorf("processLinerLine(cd no arg) => finalCwd=%q, want %q", finalCwd, home)
+	}
+}
+
+func TestReadInteractiveLine(t *testing.T) {
+	input := "help\n"
+	scanner := bufio.NewScanner(strings.NewReader(input))
+	line, done, err := readInteractiveLine(scanner, "")
+	if err != nil {
+		t.Fatalf("readInteractiveLine: %v", err)
+	}
+	if done {
+		t.Error("readInteractiveLine => done true, want false")
+	}
+	if line != "help" {
+		t.Errorf("readInteractiveLine => line=%q, want %q", line, "help")
+	}
+}
+
+func TestReadInteractiveLine_EOF(t *testing.T) {
+	scanner := bufio.NewScanner(strings.NewReader(""))
+	_, done, err := readInteractiveLine(scanner, "")
+	if err != nil {
+		t.Fatalf("readInteractiveLine EOF: %v", err)
+	}
+	if !done {
+		t.Error("readInteractiveLine(EOF) => done false, want true")
+	}
+}
+
+func TestRunInteractive_ExtractBadPackagePath(t *testing.T) {
+	dir := t.TempDir()
+	outDir := filepath.Join(dir, "out")
+	badPath := filepath.Join(dir, "nonexistent.nvpk")
+	_, stderr, err := runInteractiveWithInput(t, "extract -o "+outDir+" "+badPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "open") && !strings.Contains(stderr, "extract") {
+		t.Errorf("extract with bad package should write to stderr: %q", stderr)
+	}
+}
+
+func TestRunInteractive_ExtractNoOutputFlag(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "x.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	assertInteractiveStderrOnly(t, "open "+pkgPath+"\nextract\nquit\n", "extract: requires -o")
+}
+
+func TestRunInteractive_LsWithPath(t *testing.T) {
+	dir := t.TempDir()
+	_ = os.WriteFile(filepath.Join(dir, "a.txt"), []byte("x"), 0o644)
+	stdout, _, err := runInteractiveWithInput(t, "ls "+dir+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "a.txt") {
+		t.Errorf("ls output should list a.txt: %q", stdout)
+	}
+}
+
+func TestRunInteractive_OpenInvalidPackage(t *testing.T) {
+	dir := t.TempDir()
+	fakePkg := filepath.Join(dir, "fake.nvpk")
+	if err := os.WriteFile(fakePkg, []byte("not a package"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	assertInteractiveStderrOnly(t, "open "+fakePkg+"\nquit\n", "open:")
+}
+
+func TestGetInteractiveStdin_ReturnsOsStdinWhenNil(t *testing.T) {
+	old := InteractiveStdin
+	InteractiveStdin = nil
+	defer func() { InteractiveStdin = old }()
+	r := getInteractiveStdin()
+	if r != os.Stdin {
+		t.Error("getInteractiveStdin() with nil InteractiveStdin should return os.Stdin")
+	}
+}
+
+func TestResolvePkgPath_CurrentPackage(t *testing.T) {
+	got := resolvePkgPath([]string{}, "pkg.nvpk")
+	if got != "pkg.nvpk" {
+		t.Errorf("resolvePkgPath([], current) => %q, want %q", got, "pkg.nvpk")
+	}
+}
+
+func TestResolvePkgPath_ArgWhenNoCurrent(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "a.nvpk")
+	got := resolvePkgPath([]string{pkgPath}, "")
+	if got != pkgPath {
+		t.Errorf("resolvePkgPath([path], \"\") => %q, want %q", got, pkgPath)
+	}
+}
+
+func TestRunInteractive_ExtractWithOpenPackage(t *testing.T) {
+	runInteractiveExtract(t, "e.nvpk", "")
+}
+
+func TestRunInteractive_ExtractWithPathPrefix(t *testing.T) {
+	runInteractiveExtract(t, "ep.nvpk", " /sub")
+}
+
+func runInteractiveExtract(t *testing.T, pkgName, extractPathSuffix string) {
+	t.Helper()
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, pkgName)
+	outDir := filepath.Join(dir, "out")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	input := "open " + pkgPath + "\nextract -o " + outDir + extractPathSuffix + "\nquit\n"
+	if _, _, err := runInteractiveWithInput(t, input); err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+}
+
+func TestRunInteractive_WriteAfterOpen(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "w.nvpk")
+	if err := runCreate(nil, []string{pkgPath}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	stdout, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\nwrite\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "Wrote ") {
+		t.Errorf("stdout missing Wrote: %q", stdout)
+	}
+}
+
+func TestRunInteractive_WriteNoPackage(t *testing.T) {
+	assertInteractiveStderrOnly(t, "write\nquit\n", "No current package")
+}
+
+func TestRunInteractive_InfoNoPackage(t *testing.T) {
+	assertInteractiveStderrOnly(t, "info\nquit\n", "No current package")
+}
+
+func TestRunInteractive_AddThenReadFromPackage(t *testing.T) {
+	runInteractiveAddFlow(t, "r.nvpk", "f.txt", "hello", "open %s\nadd %s --as /f.txt\nread /f.txt\nquit\n", "")
+}
+
+func TestRunInteractive_AddThenRemove(t *testing.T) {
+	runInteractiveAddFlow(t, "rm.nvpk", "f.txt", "x", "open %s\nadd %s --as /f.txt\nremove /f.txt\nquit\n", "Removed ")
+}
+
+func runInteractiveAddFlow(t *testing.T, pkgName, fileName, content, inputFmt, wantStdout string) {
+	t.Helper()
+	dir, pkgPath, f := createDirWithPkgAndFile(t, pkgName, fileName, content)
+	input := fmt.Sprintf(inputFmt, pkgPath, f)
+	stdout, _, err := runInteractiveWithInput(t, input)
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if wantStdout != "" && !strings.Contains(stdout, wantStdout) {
+		t.Errorf("stdout should contain %q: %q", wantStdout, stdout)
+	}
+	_ = dir
+}
+
+func TestRunInteractive_ReadWithOutputFlag(t *testing.T) {
+	dir, pkgPath, f := createDirWithPkgAndFile(t, "ro.nvpk", "f.txt", "out")
+	outPath := filepath.Join(dir, "out.txt")
+	_, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\nadd "+f+" --as /f.txt\nread /f.txt -o "+outPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	// If add and read succeeded, output file should exist with content
+	got, err := os.ReadFile(outPath)
+	if err != nil {
+		t.Skipf("output file not created (add or read may have failed in env): %v", err)
+	}
+	if string(got) != "out" {
+		t.Errorf("output file: got %q, want %q", string(got), "out")
+	}
+}
+
+func TestRunInteractive_ListShowsFiles(t *testing.T) {
+	dir, pkgPath, f := createDirWithPkgAndFile(t, "lst.nvpk", "f.txt", "x")
+	stdout, _, err := runInteractiveWithInput(t, "open "+pkgPath+"\nadd "+f+" --as /f.txt\nlist\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "/f.txt") && !strings.Contains(stdout, "f.txt") {
+		t.Errorf("list output should show added file: %q", stdout)
+	}
+	_ = dir
+}
+
+func TestRunInteractive_ReadNonexistentFromPackage(t *testing.T) {
+	dir, pkgPath, f := createDirWithPkgAndFile(t, "rn.nvpk", "f.txt", "x")
+	_, stderr, err := runInteractiveWithInput(t, "open "+pkgPath+"\nadd "+f+" --as /f.txt\nread /nonexistent\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if stderr == "" {
+		t.Error("read nonexistent should write to stderr")
+	}
+	_ = dir
+}
+
+func TestReadFromPackage_ToFile(t *testing.T) {
+	dir, pkgPath, f := createDirWithPkgAndFile(t, "rf.nvpk", "f.txt", "to-file")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/f.txt", []byte("to-file"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	outPath := filepath.Join(dir, "out.txt")
+	if err := readFromPackage(pkg, "/f.txt", outPath); err != nil {
+		t.Fatalf("readFromPackage: %v", err)
+	}
+	got, err := os.ReadFile(outPath)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	if string(got) != "to-file" {
+		t.Errorf("readFromPackage to file: got %q, want %q", string(got), "to-file")
+	}
+	_ = f
+}
+
+func TestReadFromPackage_ToStdout(t *testing.T) {
+	dir, pkgPath, _ := createDirWithPkgAndFile(t, "rs.nvpk", "f.txt", "to-stdout")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/f.txt", []byte("to-stdout"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	var out bytes.Buffer
+	InteractiveStdout = &out
+	defer func() { InteractiveStdout = nil }()
+	if err := readFromPackage(pkg, "/f.txt", ""); err != nil {
+		t.Fatalf("readFromPackage: %v", err)
+	}
+	if out.String() != "to-stdout" {
+		t.Errorf("readFromPackage to stdout: got %q, want %q", out.String(), "to-stdout")
+	}
+	_ = dir
+}
+
+func TestInteractiveCompleter_LeadingWhitespace(t *testing.T) {
+	dir := t.TempDir()
+	_ = os.MkdirAll(filepath.Join(dir, "cli"), 0o755)
+	completerCwd = dir
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("\tcd c")
+	if len(got) != 1 || got[0] != "cd cli"+string(filepath.Separator) {
+		t.Errorf("interactiveCompleter(\"\\tcd c\") => %q, want [\"cd cli/\"]", got)
+	}
+}
+
+func TestInteractiveCompleter_NoCandidatesReturnsNil(t *testing.T) {
+	dir := t.TempDir()
+	completerCwd = dir
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("open zzznonexistent")
+	if got != nil {
+		t.Errorf("interactiveCompleter(\"open zzznonexistent\") => %v, want nil", got)
+	}
+}
+
+func TestInteractiveCompleter_UnreadableDirReturnsNil(t *testing.T) {
+	completerCwd = "/nonexistent_dir_12345"
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("open ")
+	if got != nil {
+		t.Errorf("interactiveCompleter(\"open \") with bad cwd => %v, want nil", got)
+	}
+}
+
+func TestCompletePath_AbsoluteDir(t *testing.T) {
+	dir := t.TempDir()
+	sub := filepath.Join(dir, "abar")
+	if err := os.MkdirAll(sub, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	completerCwd = t.TempDir()
+	defer func() { completerCwd = "" }()
+	// Complete "open <absdir>/a" => list absdir, prefix "a" => abar/
+	got := completePath("open", filepath.Join(dir, "a"))
+	if len(got) != 1 || !strings.Contains(got[0], "abar") {
+		t.Errorf("completePath(\"open\", %q) => %q, want one entry containing abar", filepath.Join(dir, "a"), got)
+	}
+}
+
+func TestCompletePath_ReadDirError(t *testing.T) {
+	completerCwd = "/nonexistent_12345"
+	defer func() { completerCwd = "" }()
+	got := completePath("open", "")
+	if got != nil {
+		t.Errorf("completePath with unreadable cwd => %v, want nil", got)
+	}
+}
+
+func TestInteractiveCompleter_TildePath(t *testing.T) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Skip("UserHomeDir:", err)
+	}
+	completerCwd = t.TempDir()
+	defer func() { completerCwd = "" }()
+	got := interactiveCompleter("open ~")
+	if len(got) == 0 {
+		t.Error("interactiveCompleter(\"open ~\") => empty, want home dir entries")
+	}
+	// Full-line: each candidate is "open " + path; path should be under home
+	for _, g := range got {
+		path := strings.TrimPrefix(g, "open ")
+		if path == g || (!strings.HasPrefix(path, "~") && !filepath.IsAbs(path)) {
+			continue
+		}
+		expanded := path
+		if strings.HasPrefix(path, "~") {
+			expanded = filepath.Join(home, strings.TrimPrefix(path, "~/"))
+		}
+		if _, err := os.Stat(expanded); err != nil && !os.IsNotExist(err) {
+			t.Logf("completion entry %q path %q expanded %q: %v", g, path, expanded, err)
+		}
+		break
+	}
+}
+
+func assertInteractiveStderrContains(t *testing.T, line, badPath string, stderrAny []string) {
+	t.Helper()
+	_, stderr, err := runInteractiveWithInput(t, fmt.Sprintf(line, badPath))
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	for _, sub := range stderrAny {
+		if strings.Contains(stderr, sub) {
+			return
+		}
+	}
+	t.Errorf("stderr should contain one of %v: %q", stderrAny, stderr)
+}
+
+func TestRunInteractive_RemoveBadPackagePath(t *testing.T) {
+	dir := t.TempDir()
+	assertInteractiveStderrContains(t, "remove %s /x\nquit\n", filepath.Join(dir, "nonexistent.nvpk"), []string{"open"})
+}
+
+func TestRunInteractive_ReadBadPackagePath(t *testing.T) {
+	dir := t.TempDir()
+	assertInteractiveStderrContains(t, "read %s /x\nquit\n", filepath.Join(dir, "nonexistent.nvpk"), []string{"open", "read"})
+}
+
+func TestRunInteractive_LsNonexistentDir(t *testing.T) {
+	dir := t.TempDir()
+	assertInteractiveStderrContains(t, "ls %s\nquit\n", filepath.Join(dir, "nonexistent"), []string{"ls"})
+}
+
+func TestRunInteractive_HeaderBadPath(t *testing.T) {
+	dir := t.TempDir()
+	assertInteractiveStderrContains(t, "header %s\nquit\n", filepath.Join(dir, "nonexistent.nvpk"), []string{"header", "read"})
+}
+
+func TestRunInteractive_HeaderNoPackage(t *testing.T) {
+	// header with no open and no arg: resolvePkgPath returns "", handler returns without error
+	_, stderr, err := runInteractiveWithInput(t, "header\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stderr, "No current package") {
+		t.Errorf("header with no package: stderr %q should contain 'No current package'", stderr)
+	}
+}
+
+func TestRunInteractive_ListWithExplicitPathNoOpen(t *testing.T) {
+	pkgPath := createTestPackage(t, "listpath.nvpk")
+	stdout, _, err := runInteractiveWithInput(t, "list "+pkgPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	// Empty package: list may show nothing; we're covering list handler with path, no open
+	_ = stdout
+}
+
+func TestRunInteractive_InfoWithExplicitPathNoOpen(t *testing.T) {
+	pkgPath := createTestPackage(t, "infopath.nvpk")
+	_, _, err := runInteractiveWithInput(t, "info "+pkgPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	// Covers interactiveInfoHandler path when no open package but path given (runInfo).
+	// runInfo writes to os.Stdout, not injected buffer, so we only assert no error.
+}
+
+func TestRunInteractive_EmptyLines(t *testing.T) {
+	_, _, err := runInteractiveWithInput(t, "\n  \nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive with empty lines: %v", err)
+	}
+}
+
+func TestProcessLinerLine_EmptyLine(t *testing.T) {
+	exit, cwd, pkg := processLinerLine("", testCwdTmp, testPkgName)
+	if exit {
+		t.Error("processLinerLine(empty) => exit true, want false")
+	}
+	if cwd != testCwdTmp || pkg != testPkgName {
+		t.Errorf("processLinerLine(empty) => cwd=%q pkg=%q", cwd, pkg)
+	}
+}
+
+func TestProcessLinerLine_WhitespaceOnly(t *testing.T) {
+	cmd, args, _ := parseInteractiveLine("   \t  ")
+	if cmd != "" || len(args) != 0 {
+		t.Errorf("parseInteractiveLine(whitespace) => cmd=%q args=%v", cmd, args)
+	}
+	exit, cwd, pkg := processLinerLine("   \t  ", testCwdTmp, "")
+	if exit {
+		t.Error("processLinerLine(whitespace) => exit true, want false")
+	}
+	if cwd != testCwdTmp || pkg != "" {
+		t.Errorf("processLinerLine(whitespace) => cwd=%q pkg=%q", cwd, pkg)
+	}
+}
+
+func TestInteractiveCd_ToFile(t *testing.T) {
+	dir := t.TempDir()
+	f := filepath.Join(dir, "file.txt")
+	if err := os.WriteFile(f, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	_, _, _, _, err := interactiveCd([]string{f}, nil, "", dir)
+	if err == nil {
+		t.Error("cd to file should fail")
+	}
+	if err != nil && !strings.Contains(err.Error(), "not a directory") {
+		t.Errorf("cd to file: want 'not a directory', got %v", err)
+	}
+}
+
+func TestInteractiveCd_ToNonexistent(t *testing.T) {
+	dir := t.TempDir()
+	bad := filepath.Join(dir, "nonexistent")
+	_, _, _, _, err := interactiveCd([]string{bad}, nil, "", dir)
+	if err == nil {
+		t.Error("cd to nonexistent should fail")
+	}
+}
+
+func TestRunAdd_OpenDirectoryAsPackage(t *testing.T) {
+	dir := t.TempDir()
+	subdir := filepath.Join(dir, "sub")
+	if err := os.MkdirAll(subdir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	f := filepath.Join(dir, "f.txt")
+	if err := os.WriteFile(f, []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	err := runAdd(addCmd, []string{subdir, f})
+	if err == nil {
+		t.Error("runAdd with directory path (not a package) should fail")
+	}
+}
+
+func TestRunInteractive_RemoveWithExplicitPkg(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "rmp.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/x.txt", []byte("x"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	_ = pkg.Close()
+	stdout, _, err := runInteractiveWithInput(t, "remove "+pkgPath+" /x.txt\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	if !strings.Contains(stdout, "Removed") {
+		t.Errorf("remove with explicit pkg: stdout %q should contain Removed", stdout)
+	}
+}
+
+func TestRunInteractive_ReadWithExplicitPkgNoOutput(t *testing.T) {
+	// Covers runInteractiveRead path when no -o (readOutput = ""), explicit pkg path
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "rdp_noout.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/z.txt", []byte("stdout-content"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	_ = pkg.Close()
+	_, _, err = runInteractiveWithInput(t, "read "+pkgPath+" /z.txt\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive read without -o: %v", err)
+	}
+	// runRead writes to os.Stdout, not captured in buffer; we only assert no error
+}
+
+func TestRunInteractive_ReadWithExplicitPkg(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "rdp.nvpk")
+	outPath := filepath.Join(dir, "out.txt")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/y.txt", []byte("from-disk"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	_ = pkg.Close()
+	_, _, err = runInteractiveWithInput(t, "read "+pkgPath+" /y.txt -o "+outPath+"\nquit\n")
+	if err != nil {
+		t.Fatalf("runInteractive: %v", err)
+	}
+	got, err := os.ReadFile(outPath)
+	if err != nil {
+		t.Fatalf("ReadFile output: %v", err)
+	}
+	if string(got) != "from-disk" {
+		t.Errorf("read with explicit pkg: got %q, want from-disk", string(got))
+	}
+}
diff --git a/cli/nvpkg/cmd/liner/liner.go b/cli/nvpkg/cmd/liner/liner.go
new file mode 100644
index 00000000..649d79c0
--- /dev/null
+++ b/cli/nvpkg/cmd/liner/liner.go
@@ -0,0 +1,47 @@
+// Package liner runs the interactive REPL loop with readline (history, completion).
+// It is in a separate package so coverage can exclude it when measuring cmd (TTY path runs in subprocess in tests).
+package liner
+
+import (
+	"fmt"
+	"strings"
+
+	readline "github.com/peterh/liner"
+)
+
+// ProcessLineFunc processes one line; returns (exit, newCwd, newPkg).
+type ProcessLineFunc func(line, cwd, currentPkg string) (exit bool, newCwd, newPkg string)
+
+// CompleterFunc returns completion candidates for the line.
+type CompleterFunc func(line string) []string
+
+// Run runs the readline loop: prompt, read line, process, repeat until exit.
+func Run(cwd string, currentPackage *string, processLine ProcessLineFunc, completer CompleterFunc, setCwd func(string)) error {
+	state := readline.NewLiner()
+	defer func() { _ = state.Close() }()
+	state.SetCtrlCAborts(true)
+	state.SetCompleter(func(line string) []string { return completer(line) })
+	for {
+		setCwd(cwd)
+		prompt := "nvpkg> "
+		if *currentPackage != "" {
+			prompt = fmt.Sprintf("nvpkg [%s]> ", *currentPackage)
+		}
+		line, err := state.Prompt(prompt)
+		if err != nil {
+			if err == readline.ErrPromptAborted {
+				return nil
+			}
+			return err
+		}
+		line = strings.TrimSpace(line)
+		if line != "" {
+			state.AppendHistory(line)
+		}
+		shouldExit, newCwd, newPkg := processLine(line, cwd, *currentPackage)
+		if shouldExit {
+			return nil
+		}
+		cwd, *currentPackage = newCwd, newPkg
+	}
+}
diff --git a/cli/nvpkg/cmd/list.go b/cli/nvpkg/cmd/list.go
new file mode 100644
index 00000000..233bca8d
--- /dev/null
+++ b/cli/nvpkg/cmd/list.go
@@ -0,0 +1,42 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var listCmd = &cobra.Command{
+	Use:   "list <package path>",
+	Short: "List files in a NovusPack package",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runList,
+}
+
+var listReadOnly bool
+
+func init() {
+	listCmd.Flags().BoolVar(&listReadOnly, "read-only", false, "Open package read-only (no write risk)")
+}
+
+func runList(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := openPackage(ctx, path, listReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	files, err := pkg.ListFiles()
+	if err != nil {
+		return fmt.Errorf("list files: %w", err)
+	}
+	for _, f := range files {
+		_, _ = fmt.Fprintf(os.Stdout, "%s  %d  %d\n", f.PrimaryPath, f.Size, f.StoredSize)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/metadata.go b/cli/nvpkg/cmd/metadata.go
new file mode 100644
index 00000000..b7d78890
--- /dev/null
+++ b/cli/nvpkg/cmd/metadata.go
@@ -0,0 +1,62 @@
+package cmd
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var metadataCmd = &cobra.Command{
+	Use:   "metadata <package path>",
+	Short: "Show full package metadata",
+	Long:  "Prints package metadata (PackageInfo, file entries, path metadata). Use --json for machine-readable output.",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runMetadata,
+}
+
+var metadataJSON bool
+var metadataReadOnly bool
+
+func init() {
+	metadataCmd.Flags().BoolVar(&metadataJSON, "json", false, "Output as JSON")
+	metadataCmd.Flags().BoolVar(&metadataReadOnly, "read-only", false, "Open package read-only")
+}
+
+func runMetadata(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := openPackage(ctx, path, metadataReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	meta, err := pkg.GetMetadata()
+	if err != nil {
+		return fmt.Errorf("get metadata: %w", err)
+	}
+	if meta == nil {
+		return fmt.Errorf("metadata is nil")
+	}
+
+	if metadataJSON {
+		enc := json.NewEncoder(os.Stdout)
+		enc.SetIndent("", "  ")
+		if err := enc.Encode(meta); err != nil {
+			return fmt.Errorf("json encode: %w", err)
+		}
+		return nil
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "File entries: %d\n", len(meta.FileEntries))
+	_, _ = fmt.Fprintf(os.Stdout, "Path metadata entries: %d\n", len(meta.PathMetadataEntries))
+	if meta.PackageInfo != nil {
+		_, _ = fmt.Fprintf(os.Stdout, "File count: %d\n", meta.FileCount)
+		_, _ = fmt.Fprintf(os.Stdout, "Uncompressed size: %d\n", meta.FilesUncompressedSize)
+		_, _ = fmt.Fprintf(os.Stdout, "Compressed size: %d\n", meta.FilesCompressedSize)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/metadata_test.go b/cli/nvpkg/cmd/metadata_test.go
new file mode 100644
index 00000000..565018d5
--- /dev/null
+++ b/cli/nvpkg/cmd/metadata_test.go
@@ -0,0 +1,44 @@
+package cmd
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func runMetadataWithFlags(t *testing.T, useJSON, readOnly bool, path string) error {
+	t.Helper()
+	metadataJSON = useJSON
+	metadataReadOnly = readOnly
+	defer func() { metadataJSON = false; metadataReadOnly = false }()
+	return runMetadata(metadataCmd, []string{path})
+}
+
+func TestRunMetadata(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		if err := runMetadataWithFlags(t, false, false, createTestPackage(t, "meta1.nvpk")); err != nil {
+			t.Fatalf("runMetadata: %v", err)
+		}
+	})
+	t.Run("json", func(t *testing.T) {
+		if err := runMetadataWithFlags(t, true, false, createTestPackage(t, "meta2.nvpk")); err != nil {
+			t.Fatalf("runMetadata --json: %v", err)
+		}
+	})
+	t.Run("read_only", func(t *testing.T) {
+		if err := runMetadataWithFlags(t, false, true, createTestPackage(t, "meta3.nvpk")); err != nil {
+			t.Fatalf("runMetadata --read-only: %v", err)
+		}
+	})
+	t.Run("no_such_package", func(t *testing.T) {
+		dir := t.TempDir()
+		path := filepath.Join(dir, "nonexistent.nvpk")
+		err := runMetadataWithFlags(t, false, false, path)
+		if err == nil {
+			t.Fatal("runMetadata on nonexistent package should fail")
+		}
+		if !strings.Contains(err.Error(), "open") {
+			t.Errorf("runMetadata no package: want error containing 'open', got %v", err)
+		}
+	})
+}
diff --git a/cli/nvpkg/cmd/package_cmd_test.go b/cli/nvpkg/cmd/package_cmd_test.go
new file mode 100644
index 00000000..c021fb15
--- /dev/null
+++ b/cli/nvpkg/cmd/package_cmd_test.go
@@ -0,0 +1,96 @@
+package cmd
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestRunPackageCommands_SuccessAndNotFound(t *testing.T) {
+	tests := []struct {
+		name     string
+		pkgName  string
+		runWith  func(path string) error
+		runEmpty func() error
+	}{
+		{
+			name:     "header",
+			pkgName:  "header.nvpk",
+			runWith:  func(p string) error { return runHeader(headerCmd, []string{p}) },
+			runEmpty: func() error { return runHeader(headerCmd, []string{"/nonexistent/pkg.nvpk"}) },
+		},
+		{
+			name:     "info",
+			pkgName:  "info.nvpk",
+			runWith:  func(p string) error { return runInfo(infoCmd, []string{p}) },
+			runEmpty: func() error { return runInfo(infoCmd, []string{"/nonexistent/pkg.nvpk"}) },
+		},
+		{
+			name:     "list",
+			pkgName:  "list.nvpk",
+			runWith:  func(p string) error { return runList(listCmd, []string{p}) },
+			runEmpty: func() error { return runList(listCmd, []string{"/nonexistent/pkg.nvpk"}) },
+		},
+		{
+			name:     "validate",
+			pkgName:  "validate.nvpk",
+			runWith:  func(p string) error { return runValidate(nil, []string{p}) },
+			runEmpty: func() error { return runValidate(nil, []string{"/nonexistent/pkg.nvpk"}) },
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name+"/success", func(t *testing.T) {
+			path := createTestPackage(t, tt.pkgName)
+			if err := tt.runWith(path); err != nil {
+				t.Fatalf("%s: %v", tt.name, err)
+			}
+		})
+		t.Run(tt.name+"/notfound", func(t *testing.T) {
+			if err := tt.runEmpty(); err == nil {
+				t.Errorf("%s: expected failure on missing package", tt.name)
+			}
+		})
+	}
+}
+
+func TestRunInfo_WithComment(t *testing.T) {
+	createComment = "my comment"
+	defer func() { createComment = "" }()
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "comment.nvpk")
+	if err := runCreate(createCmd, []string{pkgPath}); err != nil {
+		t.Fatalf("runCreate: %v", err)
+	}
+	if err := runInfo(infoCmd, []string{pkgPath}); err != nil {
+		t.Fatalf("runInfo: %v", err)
+	}
+}
+
+func TestRunInfo_WithVendorAndAppId(t *testing.T) {
+	createVendorID = 1
+	createAppID = 100
+	defer func() { createVendorID = 0; createAppID = 0 }()
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "identity.nvpk")
+	if err := runCreate(createCmd, []string{pkgPath}); err != nil {
+		t.Fatalf("runCreate: %v", err)
+	}
+	old := os.Stdout
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("pipe: %v", err)
+	}
+	os.Stdout = w
+	err = runInfo(infoCmd, []string{pkgPath})
+	_ = w.Close()
+	os.Stdout = old
+	if err != nil {
+		t.Fatalf("runInfo: %v", err)
+	}
+	out, _ := io.ReadAll(r)
+	if !strings.Contains(string(out), "Vendor ID") || !strings.Contains(string(out), "App ID") {
+		t.Errorf("info output should contain Vendor ID and App ID: %s", out)
+	}
+}
diff --git a/cli/nvpkg/cmd/read.go b/cli/nvpkg/cmd/read.go
new file mode 100644
index 00000000..e04962e1
--- /dev/null
+++ b/cli/nvpkg/cmd/read.go
@@ -0,0 +1,49 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var readCmd = &cobra.Command{
+	Use:   "read <package path> <internal path>",
+	Short: "Read a file from a NovusPack package to stdout or a file",
+	Args:  cobra.ExactArgs(2),
+	RunE:  runRead,
+}
+
+var readOutput string
+var readReadOnly bool
+
+func init() {
+	readCmd.Flags().StringVarP(&readOutput, "output", "o", "", "Write to file instead of stdout")
+	readCmd.Flags().BoolVar(&readReadOnly, "read-only", false, "Open package read-only (no write risk)")
+}
+
+func runRead(_ *cobra.Command, args []string) error {
+	pkgPath := args[0]
+	internalPath := args[1]
+	ctx := context.Background()
+
+	pkg, err := openPackage(ctx, pkgPath, readReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	data, err := pkg.ReadFile(ctx, internalPath)
+	if err != nil {
+		return fmt.Errorf("read file: %w", err)
+	}
+	if readOutput != "" {
+		if err := os.WriteFile(readOutput, data, 0o644); err != nil {
+			return fmt.Errorf("write output: %w", err)
+		}
+		return nil
+	}
+	_, err = os.Stdout.Write(data)
+	return err
+}
diff --git a/cli/nvpkg/cmd/read_test.go b/cli/nvpkg/cmd/read_test.go
new file mode 100644
index 00000000..a4040ca0
--- /dev/null
+++ b/cli/nvpkg/cmd/read_test.go
@@ -0,0 +1,127 @@
+package cmd
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+)
+
+func TestRunRead_PackageNotFound(t *testing.T) {
+	err := runRead(readCmd, []string{"/nonexistent/pkg.nvpk", "/path"})
+	if err == nil {
+		t.Error("runRead on missing package should fail")
+	}
+}
+
+func TestRunRead_FileNotInPackage(t *testing.T) {
+	path := createTestPackage(t, "read.nvpk")
+	if err := runRead(readCmd, []string{path, "/nonexistent.txt"}); err == nil {
+		t.Error("runRead with path not in package should fail")
+	}
+}
+
+func TestRunRead_OutputToDirFails(t *testing.T) {
+	dir := t.TempDir()
+	pkgPath := filepath.Join(dir, "p.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	if err := pkg.Create(ctx, pkgPath); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/x", []byte("x"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	_ = pkg.Close()
+	readOutput = dir // output is a directory; WriteFile will fail
+	defer func() { readOutput = "" }()
+	err = runRead(readCmd, []string{pkgPath, "/x"})
+	if err == nil {
+		t.Error("runRead with output=dir should fail")
+	}
+	if err != nil && !strings.Contains(err.Error(), "write output") {
+		t.Errorf("runRead output=dir: want 'write output' error, got %v", err)
+	}
+}
+
+func TestRunRead_OutputToFile(t *testing.T) {
+	readOutput = "/tmp/nvpkg-read-test-out"
+	defer func() { readOutput = "" }()
+	dir := t.TempDir()
+	path := filepath.Join(dir, "read.nvpk")
+	if err := runCreate(createCmd, []string{path}); err != nil {
+		t.Fatalf("create: %v", err)
+	}
+	err := runRead(readCmd, []string{path, "/nonexistent.txt"})
+	if err == nil {
+		t.Error("runRead with missing file should fail")
+	}
+	_ = os.Remove(readOutput)
+}
+
+// TestRunRead_Success uses the api to create a package with a file; when api path
+// metadata write is complete this test will cover runRead success (stdout and -o).
+func TestRunRead_Success(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "withfile.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, path); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/x.txt", []byte("content"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	readOutput = ""
+	err = runRead(readCmd, []string{path, "/x.txt"})
+	if err != nil {
+		t.Errorf("runRead: %v", err)
+	}
+}
+
+func TestRunRead_Success_OutputToFile(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "withfile2.nvpk")
+	outPath := filepath.Join(dir, "out.txt")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, path); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/y.txt", []byte("data"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	readOutput = outPath
+	defer func() { readOutput = "" }()
+	err = runRead(readCmd, []string{path, "/y.txt"})
+	if err != nil {
+		t.Errorf("runRead: %v", err)
+	}
+	got, _ := os.ReadFile(outPath)
+	if string(got) != "data" {
+		t.Errorf("output file: got %q, want %q", string(got), "data")
+	}
+}
diff --git a/cli/nvpkg/cmd/remove.go b/cli/nvpkg/cmd/remove.go
new file mode 100644
index 00000000..21b238ff
--- /dev/null
+++ b/cli/nvpkg/cmd/remove.go
@@ -0,0 +1,60 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+	"github.com/spf13/cobra"
+)
+
+var removePattern bool
+
+var removeCmd = &cobra.Command{
+	Use:   "remove <package path> <internal path or pattern>",
+	Short: "Remove a file or directory from a NovusPack package",
+	Long:  "Removes a single file, all files under a directory path (path ending with /), or files matching a pattern (--pattern).",
+	Args:  cobra.ExactArgs(2),
+	RunE:  runRemove,
+}
+
+func init() {
+	removeCmd.Flags().BoolVar(&removePattern, "pattern", false, "treat second argument as a glob pattern (e.g. *.tmp)")
+}
+
+func runRemove(_ *cobra.Command, args []string) error {
+	pkgPath := args[0]
+	internalPath := args[1]
+	ctx := context.Background()
+
+	pkg, err := novuspack.OpenPackage(ctx, pkgPath)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	switch {
+	case removePattern:
+		_, err := pkg.RemoveFilePattern(ctx, internalPath)
+		if err != nil {
+			return fmt.Errorf("remove pattern: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Removed files matching %q from %s\n", internalPath, pkgPath)
+	case internalPath != "" && internalPath[len(internalPath)-1] == '/':
+		_, err := pkg.RemoveDirectory(ctx, internalPath, nil)
+		if err != nil {
+			return fmt.Errorf("remove directory: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Removed directory %s from %s\n", internalPath, pkgPath)
+	default:
+		if err := pkg.RemoveFile(ctx, internalPath); err != nil {
+			return fmt.Errorf("remove: %w", err)
+		}
+		_, _ = fmt.Fprintf(os.Stdout, "Removed %s from %s\n", internalPath, pkgPath)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		return fmt.Errorf("write: %w", err)
+	}
+	return nil
+}
diff --git a/cli/nvpkg/cmd/remove_test.go b/cli/nvpkg/cmd/remove_test.go
new file mode 100644
index 00000000..f66344f0
--- /dev/null
+++ b/cli/nvpkg/cmd/remove_test.go
@@ -0,0 +1,69 @@
+package cmd
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+)
+
+func TestRunRemove_PackageNotFound(t *testing.T) {
+	err := runRemove(removeCmd, []string{"/nonexistent/pkg.nvpk", "/some/path"})
+	if err == nil {
+		t.Error("runRemove on missing package should fail")
+	}
+}
+
+func TestRunRemove_FileNotInPackage(t *testing.T) {
+	path := createTestPackage(t, "remove.nvpk")
+	if err := runRemove(removeCmd, []string{path, "/nonexistent.txt"}); err == nil {
+		t.Error("runRemove with path not in package should fail")
+	}
+}
+
+// TestRunRemove_Success creates a package with a file via the API, then removes the file via CLI.
+func TestRunRemove_Success(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "remove_success.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, path); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/z.txt", []byte("z"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	err = runRemove(removeCmd, []string{path, "/z.txt"})
+	if err != nil {
+		t.Errorf("runRemove: %v", err)
+	}
+}
+
+func TestRunRemove_WithPatternFlag(t *testing.T) {
+	path := createTestPackage(t, "remove_pattern.nvpk")
+	removePattern = true
+	defer func() { removePattern = false }()
+	// API may return ErrTypeUnsupported until RemoveFilePattern is implemented
+	err := runRemove(removeCmd, []string{path, "*.tmp"})
+	if err != nil && !strings.Contains(err.Error(), "unsupported") && !strings.Contains(err.Error(), "remove pattern") {
+		t.Errorf("runRemove --pattern: %v", err)
+	}
+}
+
+func TestRunRemove_DirectoryPath(t *testing.T) {
+	path := createTestPackage(t, "remove_dir.nvpk")
+	// API may return ErrTypeUnsupported until RemoveDirectory is implemented
+	err := runRemove(removeCmd, []string{path, "/subdir/"})
+	if err != nil && !strings.Contains(err.Error(), "unsupported") && !strings.Contains(err.Error(), "remove directory") {
+		t.Errorf("runRemove directory: %v", err)
+	}
+}
diff --git a/cli/nvpkg/cmd/root.go b/cli/nvpkg/cmd/root.go
new file mode 100644
index 00000000..77bb4caa
--- /dev/null
+++ b/cli/nvpkg/cmd/root.go
@@ -0,0 +1,31 @@
+package cmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var rootCmd = &cobra.Command{
+	Use:   "nvpkg",
+	Short: "NovusPack package manager CLI",
+	Long:  "nvpkg is a CLI for creating, inspecting, and modifying NovusPack (.nvpk) packages. Use 'nvpkg interactive' (or 'nvpkg i') for REPL mode.",
+}
+
+func Execute() error {
+	return rootCmd.Execute()
+}
+
+func init() {
+	rootCmd.AddCommand(createCmd)
+	rootCmd.AddCommand(infoCmd)
+	rootCmd.AddCommand(listCmd)
+	rootCmd.AddCommand(addCmd)
+	rootCmd.AddCommand(removeCmd)
+	rootCmd.AddCommand(readCmd)
+	rootCmd.AddCommand(extractCmd)
+	rootCmd.AddCommand(headerCmd)
+	rootCmd.AddCommand(validateCmd)
+	rootCmd.AddCommand(commentCmd)
+	rootCmd.AddCommand(identityCmd)
+	rootCmd.AddCommand(metadataCmd)
+	rootCmd.AddCommand(interactiveCmd)
+}
diff --git a/cli/nvpkg/cmd/root_test.go b/cli/nvpkg/cmd/root_test.go
new file mode 100644
index 00000000..34972b4e
--- /dev/null
+++ b/cli/nvpkg/cmd/root_test.go
@@ -0,0 +1,31 @@
+package cmd
+
+import (
+	"testing"
+)
+
+func TestExecute_UnknownCommand(t *testing.T) {
+	rootCmd.SetArgs([]string{"unknown-subcommand"})
+	err := Execute()
+	if err == nil {
+		t.Error("Execute with unknown subcommand should return error")
+	}
+}
+
+func TestExecute_Help(t *testing.T) {
+	rootCmd.SetArgs([]string{"--help"})
+	err := Execute()
+	if err != nil {
+		t.Errorf("Execute --help: %v", err)
+	}
+}
+
+func TestExecute_Create(t *testing.T) {
+	dir := t.TempDir()
+	path := dir + "/from-execute.nvpk"
+	rootCmd.SetArgs([]string{"create", path})
+	err := Execute()
+	if err != nil {
+		t.Errorf("Execute create: %v", err)
+	}
+}
diff --git a/cli/nvpkg/cmd/validate.go b/cli/nvpkg/cmd/validate.go
new file mode 100644
index 00000000..e0f551f7
--- /dev/null
+++ b/cli/nvpkg/cmd/validate.go
@@ -0,0 +1,40 @@
+package cmd
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var validateCmd = &cobra.Command{
+	Use:   "validate <package path>",
+	Short: "Validate package integrity",
+	Long:  "Validates an existing NovusPack package (header, index, and optional content checks).",
+	Args:  cobra.ExactArgs(1),
+	RunE:  runValidate,
+}
+
+var validateReadOnly bool
+
+func init() {
+	validateCmd.Flags().BoolVar(&validateReadOnly, "read-only", false, "Open package read-only (no write risk)")
+}
+
+func runValidate(_ *cobra.Command, args []string) error {
+	path := args[0]
+	ctx := context.Background()
+
+	pkg, err := openPackage(ctx, path, validateReadOnly)
+	if err != nil {
+		return fmt.Errorf("open package: %w", err)
+	}
+	defer func() { _ = pkg.Close() }()
+
+	if err := pkg.Validate(ctx); err != nil {
+		return fmt.Errorf("validate: %w", err)
+	}
+	_, _ = fmt.Fprintf(os.Stdout, "OK %s\n", path)
+	return nil
+}
diff --git a/cli/nvpkg/cmd/validate_test.go b/cli/nvpkg/cmd/validate_test.go
new file mode 100644
index 00000000..82e747fe
--- /dev/null
+++ b/cli/nvpkg/cmd/validate_test.go
@@ -0,0 +1,46 @@
+package cmd
+
+import (
+	"context"
+	"path/filepath"
+	"testing"
+
+	novuspack "github.com/novus-engine/novuspack/api/go"
+)
+
+func TestRunValidate_PackageNotFound(t *testing.T) {
+	err := runValidate(nil, []string{"/nonexistent/pkg.nvpk"})
+	if err == nil {
+		t.Error("runValidate on missing package should fail")
+	}
+}
+
+func TestRunValidate_Success(t *testing.T) {
+	path := createTestPackage(t, "validate.nvpk")
+	if err := runValidate(nil, []string{path}); err != nil {
+		t.Errorf("runValidate: %v", err)
+	}
+}
+
+func TestRunValidate_OpenPackage(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "v.nvpk")
+	ctx := context.Background()
+	pkg, err := novuspack.NewPackage()
+	if err != nil {
+		t.Fatalf("NewPackage: %v", err)
+	}
+	defer func() { _ = pkg.Close() }()
+	if err := pkg.Create(ctx, path); err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if _, err := pkg.AddFileFromMemory(ctx, "/a.txt", []byte("x"), nil); err != nil {
+		t.Fatalf("AddFileFromMemory: %v", err)
+	}
+	if err := pkg.Write(ctx); err != nil {
+		t.Skipf("Write failed (api path metadata may be incomplete): %v", err)
+	}
+	if err := runValidate(nil, []string{path}); err != nil {
+		t.Errorf("runValidate on written package: %v", err)
+	}
+}
diff --git a/cli/nvpkg/docs/api_surface_gaps.md b/cli/nvpkg/docs/api_surface_gaps.md
new file mode 100644
index 00000000..c1464d12
--- /dev/null
+++ b/cli/nvpkg/docs/api_surface_gaps.md
@@ -0,0 +1,120 @@
+# CLI vs API Surface: Gaps and Recommendations
+
+This document compares the NovusPack Go API surface with the nvpkg CLI and recommends what to implement next.
+
+## Current CLI Coverage
+
+| CLI command | API used                                         |
+| ----------- | ------------------------------------------------ |
+| create      | NewPackage, Create (CreateWithOptions via flags) |
+| info        | OpenPackage, GetInfo                             |
+| list        | OpenPackage, ListFiles                           |
+| add         | OpenPackage/NewPackage, AddFile, AddDirectory    |
+| remove      | OpenPackage, RemoveFile                          |
+| read        | OpenPackage, ReadFile                            |
+| extract     | OpenPackage, ListFiles, ReadFile                 |
+| header      | OpenPackage (raw header read)                    |
+| interactive | All of the above in REPL                         |
+
+## Recommended Additions (by priority)
+
+### 1. High value, low effort
+
+- **Validate** – `nvpkg validate <path>`
+
+  - API: `Package.Validate(ctx)`
+  - Use: integrity check before/after operations; CI; debugging.
+  - Fits REQ-VALID-002 (package integrity validation).
+
+- **Remove by pattern / directory**
+
+  - API: `RemoveFilePattern(ctx, pattern)`, `RemoveDirectory(ctx, dirPath)`
+  - CLI: e.g. `remove <pkg> --pattern "*.tmp"` or `remove <pkg> /dir/` (remove all under path).
+  - Use: bulk cleanup without scripting single-file remove.
+
+- **Info: show VendorID / AppID**
+  - API: already in `GetInfo()` → `PackageInfo.VendorID`, `AppID`.
+  - CLI: extend `nvpkg info` (and interactive `info`) to print VendorID/AppID when non-zero.
+  - Use: identity inspection; matches create’s `--vendor-id` / `--app-id`.
+
+### 2. Write and lifecycle options
+
+- **SafeWrite** – `nvpkg write ... --safe` or interactive `write --safe`
+
+  - API: `Package.SafeWrite(ctx, overwrite bool)`.
+  - Use: avoid overwriting existing file unless `--overwrite`.
+
+- **Defragment** – `nvpkg defragment <path>` or interactive `defragment`
+
+  - API: `Package.Defragment(ctx)`.
+  - Use: compact package after many add/remove cycles.
+
+- **FastWrite** (optional)
+  - API: `Package.FastWrite(ctx)`.
+  - Use: faster write when full integrity check can be skipped (document trade-off).
+
+### 3. Open mode and safety
+
+- **Open read-only**
+  - API: `OpenPackageReadOnly(ctx, path)`.
+  - Use: `nvpkg list/read/info/extract/validate <path>` without risk of modification; scripting/CI.
+  - Could be global flag `--read-only` or separate commands that default to read-only.
+
+### 4. Comment and identity on existing packages
+
+- **Get/Set comment on open package**
+
+  - API: `GetComment()`, `SetComment(comment)`, `ClearComment()`, `HasComment()`.
+  - CLI: interactive `comment` / `comment "..."` / `comment --clear`; optional non-interactive `nvpkg comment <path> [--set "..."] [--clear]`.
+  - Use: adjust description without recreate.
+
+- **Get/Set identity on open package**
+  - API: `GetVendorID`, `SetVendorID`, `GetAppID`, `SetAppID`, `GetPackageIdentity`, `SetPackageIdentity`, etc.
+  - CLI: interactive `vendor-id` / `app-id` get/set; optional non-interactive `nvpkg identity <path> [--vendor-id N] [--app-id N]`.
+  - Use: fix or set identity after create.
+
+### 5. Add by pattern
+
+- **AddFilePattern**
+  - API: `AddFilePattern(ctx, pattern, options)`.
+  - CLI: `add <pkg> "*.json"` or `add <pkg> --pattern "*.json"` (with cwd or base path).
+  - Use: bulk add by glob without listing files in shell.
+
+### 6. Advanced (lower priority)
+
+- **GetMetadata** – full metadata dump (e.g. `nvpkg metadata <path>` or `--json` on info).
+
+  - API: `Package.GetMetadata()`.
+  - Use: tooling, debugging, integration.
+
+- **Path metadata / hierarchy** – ListPaths, GetPathInfo, GetPathHierarchy, ListDirectories.
+
+  - Use: path-centric view vs file-centric list; advanced tooling.
+
+- **Session base / target path** – SetSessionBase, GetSessionBase, SetTargetPath.
+
+  - Use: path derivation and redirecting write; power users and scripts.
+
+- **Lookup by ID/hash/type** – GetFileByFileID, GetFileByHash, GetFileByChecksum, FindEntriesByTag, FindEntriesByType, GetFileCount.
+
+  - Use: dedup inspection, content-addressable lookup, filtering by type/tag.
+
+- **Path metadata API** – AddPathMetadata, UpdatePathMetadata, GetPathConflicts, AssociateFileWithPath, etc.
+  - Use: rich metadata workflows; likely need a separate “metadata” subcommand or interactive verbs.
+
+## Summary
+
+| Priority | Feature                                                                       | API surface                  | Suggested CLI surface                 |
+| -------- | ----------------------------------------------------------------------------- | ---------------------------- | ------------------------------------- |
+| High     | Validate                                                                      | Validate(ctx)                | `nvpkg validate <path>`               |
+| High     | Remove pattern/dir                                                            | RemoveFilePattern, RemoveDir | `remove --pattern` / remove dir path  |
+| High     | Info VendorID/AppID                                                           | GetInfo (existing)           | Extend `info` output                  |
+| Medium   | SafeWrite                                                                     | SafeWrite(ctx, overwrite)    | `write --safe` [--overwrite]          |
+| Medium   | Defragment                                                                    | Defragment(ctx)              | `nvpkg defragment <path>`             |
+| Medium   | Open read-only                                                                | OpenPackageReadOnly          | `--read-only` or read-only commands   |
+| Medium   | Comment get/set                                                               | Get/Set/ClearComment         | interactive + optional `comment`      |
+| Medium   | Identity get/set                                                              | Get/Set VendorID/AppID       | interactive + optional `identity`     |
+| Lower    | Add by pattern                                                                | AddFilePattern               | `add --pattern "*.json"`              |
+| Lower    | FastWrite, GetMetadata, path/hierarchy, session/target, lookup by ID/hash/tag | Various                      | As needed for tooling and power users |
+
+Implementing **validate**, **remove by pattern/directory**, and **info VendorID/AppID** first gives the best payoff for typical use and aligns with existing API and requirements.
diff --git a/cli/nvpkg/go.mod b/cli/nvpkg/go.mod
new file mode 100644
index 00000000..75b75bd1
--- /dev/null
+++ b/cli/nvpkg/go.mod
@@ -0,0 +1,31 @@
+module github.com/novus-engine/novuspack/cli/nvpkg
+
+go 1.25
+
+replace github.com/novus-engine/novuspack => ../..
+
+replace github.com/novus-engine/novuspack/api/go => ../../api/go
+
+require (
+	github.com/creack/pty v1.1.21
+	github.com/novus-engine/novuspack/api/go v0.0.0
+	github.com/peterh/liner v1.2.2
+	github.com/spf13/cobra v1.8.1
+)
+
+require (
+	github.com/cucumber/gherkin/go/v26 v26.2.0 // indirect
+	github.com/cucumber/godog v0.15.1 // indirect
+	github.com/cucumber/messages/go/v21 v21.0.1 // indirect
+	github.com/goccy/go-yaml v1.19.2 // indirect
+	github.com/gofrs/uuid v4.4.0+incompatible // indirect
+	github.com/hashicorp/go-immutable-radix v1.3.1 // indirect
+	github.com/hashicorp/go-memdb v1.3.5 // indirect
+	github.com/hashicorp/golang-lru v1.0.2 // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/mattn/go-runewidth v0.0.3 // indirect
+	github.com/samber/lo v1.52.0 // indirect
+	github.com/spf13/pflag v1.0.10 // indirect
+	golang.org/x/sys v0.0.0-20211117180635-dee7805ff2e1 // indirect
+	golang.org/x/text v0.33.0 // indirect
+)
diff --git a/cli/nvpkg/go.sum b/cli/nvpkg/go.sum
new file mode 100644
index 00000000..b41e370b
--- /dev/null
+++ b/cli/nvpkg/go.sum
@@ -0,0 +1,71 @@
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diff --git a/cli/nvpkg/main.go b/cli/nvpkg/main.go
new file mode 100644
index 00000000..c82c9977
--- /dev/null
+++ b/cli/nvpkg/main.go
@@ -0,0 +1,13 @@
+package main
+
+import (
+	"os"
+
+	"github.com/novus-engine/novuspack/cli/nvpkg/cmd"
+)
+
+func main() {
+	if err := cmd.Execute(); err != nil {
+		os.Exit(1)
+	}
+}
diff --git a/cli/nvpkg/scripts/check_add_list_read.sh b/cli/nvpkg/scripts/check_add_list_read.sh
new file mode 100755
index 00000000..2694e756
--- /dev/null
+++ b/cli/nvpkg/scripts/check_add_list_read.sh
@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# Check nvpkg add, list, read roundtrip.
+# Skip if add fails (api path metadata write may be incomplete).
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TMP_DIR="${SCRIPT_DIR}/../../tmp"
+mkdir -p "$TMP_DIR"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+PKG="${TMP_DIR}/check_add_list_read_$$.nvpk"
+CONTENT_FILE="${TMP_DIR}/check_add_content_$$.txt"
+CONTENT="hello nvpkg"
+
+echo "$CONTENT" > "$CONTENT_FILE"
+if ! "$NVPKG" add "$PKG" "$CONTENT_FILE" --as /content.txt 2>/dev/null; then
+	rm -f "$CONTENT_FILE"
+	echo "check_add_list_read: SKIP (add failed - path metadata write may be incomplete in api)"
+	exit 0
+fi
+"$NVPKG" list "$PKG" | grep -q "content.txt" || { echo "list: expected file path"; exit 1; }
+OUT="$("$NVPKG" read "$PKG" "/content.txt")"
+test "$OUT" = "$CONTENT" || { echo "read: content mismatch"; exit 1; }
+rm -f "$PKG" "$CONTENT_FILE"
+echo "check_add_list_read: OK"
diff --git a/cli/nvpkg/scripts/check_create.sh b/cli/nvpkg/scripts/check_create.sh
new file mode 100755
index 00000000..b7d5f612
--- /dev/null
+++ b/cli/nvpkg/scripts/check_create.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+# Check nvpkg create command: create empty package, then info.
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TMP_DIR="${SCRIPT_DIR}/../../tmp"
+mkdir -p "$TMP_DIR"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+PKG="${TMP_DIR}/check_create_$$.nvpk"
+
+"$NVPKG" create "$PKG"
+test -f "$PKG" || { echo "create: package file not created"; exit 1; }
+"$NVPKG" info "$PKG" | head -1 | grep -q "Path:" || { echo "info: expected Path line"; exit 1; }
+rm -f "$PKG"
+echo "check_create: OK"
diff --git a/cli/nvpkg/scripts/check_header_info.sh b/cli/nvpkg/scripts/check_header_info.sh
new file mode 100755
index 00000000..2a67bdce
--- /dev/null
+++ b/cli/nvpkg/scripts/check_header_info.sh
@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+# Check nvpkg header, info, and validate commands on an existing package.
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TMP_DIR="${SCRIPT_DIR}/../../tmp"
+mkdir -p "$TMP_DIR"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+PKG="${TMP_DIR}/check_header_info_$$.nvpk"
+
+"$NVPKG" create "$PKG"
+"$NVPKG" header "$PKG" | grep -q "Magic:" || { echo "header: expected Magic line"; exit 1; }
+"$NVPKG" header "$PKG" | grep -q "FormatVersion:" || { echo "header: expected FormatVersion line"; exit 1; }
+"$NVPKG" info "$PKG" | grep -q "File count:" || { echo "info: expected File count line"; exit 1; }
+"$NVPKG" create "$TMP_DIR/check_identity_$$.nvpk" --vendor-id 1 --app-id 100
+"$NVPKG" info "$TMP_DIR/check_identity_$$.nvpk" | grep -q "Vendor ID:" || { echo "info: expected Vendor ID line"; exit 1; }
+"$NVPKG" info "$TMP_DIR/check_identity_$$.nvpk" | grep -q "App ID:" || { echo "info: expected App ID line"; exit 1; }
+rm -f "$PKG" "$TMP_DIR/check_identity_$$.nvpk"
+echo "check_header_info: OK"
diff --git a/cli/nvpkg/scripts/check_remove.sh b/cli/nvpkg/scripts/check_remove.sh
new file mode 100755
index 00000000..d093a907
--- /dev/null
+++ b/cli/nvpkg/scripts/check_remove.sh
@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Check nvpkg remove: add file, remove it, list empty.
+# Skip if add fails (api path metadata write may be incomplete).
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TMP_DIR="${SCRIPT_DIR}/../../tmp"
+mkdir -p "$TMP_DIR"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+PKG="${TMP_DIR}/check_remove_$$.nvpk"
+CONTENT_FILE="${TMP_DIR}/check_remove_content_$$.txt"
+echo "x" > "$CONTENT_FILE"
+
+if ! "$NVPKG" add "$PKG" "$CONTENT_FILE" --as /to_remove.txt 2>/dev/null; then
+	rm -f "$CONTENT_FILE"
+	echo "check_remove: SKIP (add failed - path metadata write may be incomplete in api)"
+	exit 0
+fi
+"$NVPKG" list "$PKG" | grep -q "to_remove.txt" || { echo "add: file not in list"; exit 1; }
+"$NVPKG" remove "$PKG" "/to_remove.txt"
+LINES="$("$NVPKG" list "$PKG" | wc -l)"
+test "$LINES" -eq 0 || { echo "remove: list not empty"; exit 1; }
+# Exercise remove --pattern (may fail with "unsupported" until API implements RemoveFilePattern)
+"$NVPKG" remove "$PKG" "*.tmp" --pattern 2>/dev/null || true
+rm -f "$PKG" "$CONTENT_FILE"
+echo "check_remove: OK"
diff --git a/cli/nvpkg/scripts/check_validate.sh b/cli/nvpkg/scripts/check_validate.sh
new file mode 100755
index 00000000..a29d136a
--- /dev/null
+++ b/cli/nvpkg/scripts/check_validate.sh
@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Check nvpkg validate on an existing package.
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+TMP_DIR="${SCRIPT_DIR}/../../tmp"
+mkdir -p "$TMP_DIR"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+PKG="${TMP_DIR}/check_validate_$$.nvpk"
+
+"$NVPKG" create "$PKG"
+"$NVPKG" validate "$PKG" | grep -q "OK" || { echo "validate: expected OK line"; exit 1; }
+if "$NVPKG" validate /nonexistent/pkg.nvpk 2>/dev/null; then
+	echo "validate nonexistent: should fail"
+	exit 1
+fi
+rm -f "$PKG"
+echo "check_validate: OK"
diff --git a/cli/nvpkg/scripts/run_all.sh b/cli/nvpkg/scripts/run_all.sh
new file mode 100755
index 00000000..6e5e1f8d
--- /dev/null
+++ b/cli/nvpkg/scripts/run_all.sh
@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+# Run all nvpkg functionality checks. Uses tmp at repo root.
+set -e
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+NVPKG="${NVPKG:-${SCRIPT_DIR}/../nvpkg}"
+if ! test -x "$NVPKG"; then
+	echo "Build nvpkg first: cd $(dirname "$SCRIPT_DIR") && go build -o nvpkg ."
+	exit 1
+fi
+"$SCRIPT_DIR/check_create.sh"
+"$SCRIPT_DIR/check_header_info.sh"
+"$SCRIPT_DIR/check_validate.sh"
+"$SCRIPT_DIR/check_add_list_read.sh"
+"$SCRIPT_DIR/check_remove.sh"
+echo "All checks passed."
diff --git a/scripts/validate_go_code_blocks.py b/scripts/validate_go_code_blocks.py
index 7f4f3861..55f8b8fd 100644
--- a/scripts/validate_go_code_blocks.py
+++ b/scripts/validate_go_code_blocks.py
@@ -390,17 +390,18 @@ def suggest_heading(heading: str, search_term: str, kind_word: str) -> str:
         pattern = re.compile(r'\b' + re.escape(search_term) + r'\b', re.IGNORECASE)
     normalized = pattern.sub('', normalized, count=1)
 
-    # Remove kind_word (case-insensitive, whole word)
-    kind_pattern = re.compile(r'\b' + re.escape(kind_word) + r'\b', re.IGNORECASE)
-    normalized = kind_pattern.sub('', normalized, count=1)
-    # Also remove common long form (e.g. "Structure" when kind is "Struct")
-    if kind_word == 'Struct':
-        normalized = re.sub(r'\bStructure\b', '', normalized, count=1, flags=re.IGNORECASE)
-
-    remaining = ' '.join(normalized.split())
+    # Use the exact kind word from the heading (e.g. "Structure", "Struct", "Method")
+    # so we never change Struct <-> Structure or other wording.
+    parts = normalized.split()
+    if parts:
+        kind_word_used = parts[0]
+        remaining = ' '.join(parts[1:])
+    else:
+        kind_word_used = kind_word
+        remaining = ''
 
-    # Prefer definition name in backticks
-    suggested = f"`{search_term}` {kind_word} {remaining}".strip()
+    # Prefer definition name in backticks; keep original kind word unchanged
+    suggested = f"`{search_term}` {kind_word_used} {remaining}".strip()
 
     if numbering_prefix:
         suggested = f"{numbering_prefix} {suggested}"