diff --git a/just/phenotype.just b/just/phenotype.just
new file mode 100644
index 0000000..9b9ecc2
--- /dev/null
+++ b/just/phenotype.just
@@ -0,0 +1,195 @@
+# phenotype.just — shared recipe library for Phenotype-org repositories
+#
+# Usage (in a consumer repo's justfile):
+#     import "phenotype.just"
+#
+# All recipes here are workspace-agnostic; they auto-detect the build system
+# (cargo / npm / pnpm / yarn / bun / uv / poetry / go / mix) and run the
+# appropriate command. Recipes that are stack-specific (e.g. `register-startmenu`
+# for Electrobun) live in the consumer's justfile, NOT here.
+#
+# Versioning: SemVer. Breaking a recipe signature is a major bump.
+
+# === variables ===
+
+# Detect the build system by walking up from the justfile dir.
+# Returns one of: cargo | npm | pnpm | yarn | bun | uv | poetry | go | mix | none
+build_system := `\
+  if [ -f Cargo.toml ]; then echo cargo; \
+  elif [ -f package.json ] && [ -f pnpm-lock.yaml ]; then echo pnpm; \
+  elif [ -f package.json ] && [ -f yarn.lock ]; then echo yarn; \
+  elif [ -f package.json ] && [ -f bun.lockb ]; then echo bun; \
+  elif [ -f package.json ] && [ -f bun.lock ]; then echo bun; \
+  elif [ -f package.json ]; then echo npm; \
+  elif [ -f pyproject.toml ] && [ -f uv.lock ]; then echo uv; \
+  elif [ -f pyproject.toml ] && [ -f poetry.lock ]; then echo poetry; \
+  elif [ -f pyproject.toml ]; then echo uv; \
+  elif [ -f go.mod ]; then echo go; \
+  elif [ -f mix.exs ]; then echo mix; \
+  else echo none; fi`
+
+# Recipe to invoke for "build".
+build_cmd := if build_system == "cargo" { "cargo build --workspace" } \
+             else if build_system == "pnpm" { "pnpm -r build" } \
+             else if build_system == "yarn" { "yarn workspaces run build" } \
+             else if build_system == "bun" { "bun run build" } \
+             else if build_system == "npm" { "npm run build --workspaces --if-present" } \
+             else if build_system == "uv" { "uv sync --all-extras" } \
+             else if build_system == "poetry" { "poetry install --all-extras" } \
+             else if build_system == "go" { "go build ./..." } \
+             else if build_system == "mix" { "mix compile" } \
+             else { "echo 'no build system detected' && exit 1" }
+
+# Recipe to invoke for "test".
+test_cmd := if build_system == "cargo" { "cargo test --workspace" } \
+            else if build_system == "pnpm" { "pnpm -r test" } \
+            else if build_system == "yarn" { "yarn workspaces run test" } \
+            else if build_system == "bun" { "bun test" } \
+            else if build_system == "npm" { "npm test --workspaces --if-present" } \
+            else if build_system == "uv" { "uv run pytest" } \
+            else if build_system == "poetry" { "poetry run pytest" } \
+            else if build_system == "go" { "go test ./..." } \
+            else if build_system == "mix" { "mix test" } \
+            else { "echo 'no test runner detected' && exit 1" }
+
+# Recipe to invoke for "lint".
+lint_cmd := if build_system == "cargo" { "cargo clippy --workspace --all-targets -- -D warnings && cargo fmt --check" } \
+            else if build_system == "pnpm" { "pnpm -r lint && pnpm -r format:check" } \
+            else if build_system == "yarn" { "yarn workspaces run lint" } \
+            else if build_system == "bun" { "bun run lint" } \
+            else if build_system == "npm" { "npm run lint --workspaces --if-present" } \
+            else if build_system == "uv" { "uv run ruff check . && uv run ruff format --check ." } \
+            else if build_system == "poetry" { "poetry run ruff check . && poetry run ruff format --check ." } \
+            else if build_system == "go" { "go vet ./... && gofmt -l ." } \
+            else if build_system == "mix" { "mix format --check-formatted && mix credo --strict" } \
+            else { "echo 'no linter detected' && exit 1" }
+
+# === core recipes ===
+
+# Default: list recipes.
+default:
+    @just --list -u
+
+# Build the workspace.
+build:
+    {{build_cmd}}
+
+# Run the test suite.
+test:
+    {{test_cmd}}
+
+# Lint (linter + formatter check).
+lint:
+    {{lint_cmd}}
+
+# Auto-format all files in place.
+fmt:
+    @just _fmt
+
+# Stack-specific formatters.
+_fmt:
+    @if [ "{{build_system}}" = "cargo" ]; then cargo fmt; \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm -r format; \
+    elif [ "{{build_system}}" = "yarn" ]; then yarn workspaces run format; \
+    elif [ "{{build_system}}" = "bun" ]; then bun run fmt; \
+    elif [ "{{build_system}}" = "npm" ]; then npm run format --workspaces --if-present; \
+    elif [ "{{build_system}}" = "uv" ]; then uv run ruff format .; \
+    elif [ "{{build_system}}" = "poetry" ]; then poetry run ruff format .; \
+    elif [ "{{build_system}}" = "go" ]; then gofmt -w .; \
+    elif [ "{{build_system}}" = "mix" ]; then mix format; \
+    else echo "no formatter detected for {{build_system}}"; fi
+
+# Security audits. Stack-specific.
+audit:
+    @just _audit
+
+_audit:
+    @if [ "{{build_system}}" = "cargo" ]; then \
+        (command -v cargo-deny >/dev/null && cargo deny check || echo "cargo-deny not installed; skip") && \
+        (command -v cargo-audit >/dev/null && cargo audit || echo "cargo-audit not installed; skip"); \
+    elif [ "{{build_system}}" = "uv" ] || [ "{{build_system}}" = "poetry" ]; then \
+        uv run pip-audit 2>/dev/null || poetry run pip-audit 2>/dev/null || echo "pip-audit not installed; skip"; \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm audit --prod; \
+    elif [ "{{build_system}}" = "bun" ]; then bun audit; \
+    elif [ "{{build_system}}" = "npm" ]; then npm audit --omit=dev; \
+    elif [ "{{build_system}}" = "go" ]; then govulncheck ./... 2>/dev/null || echo "govulncheck not installed; skip"; \
+    else echo "no audit tool for {{build_system}}"; fi
+
+# Find unused dependencies. Stack-specific.
+unused:
+    @just _unused
+
+_unused:
+    @if [ "{{build_system}}" = "cargo" ]; then \
+        (command -v cargo-machete >/dev/null && cargo machete || echo "cargo-machete not installed; skip"); \
+    elif [ "{{build_system}}" = "uv" ] || [ "{{build_system}}" = "poetry" ]; then \
+        uv run deptry . 2>/dev/null || poetry run deptry . 2>/dev/null || echo "deptry not installed; skip"; \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm dlx depcheck; \
+    else echo "no unused-dep tool for {{build_system}}"; fi
+
+# Type-check. Stack-specific.
+typecheck:
+    @just _typecheck
+
+_typecheck:
+    @if [ "{{build_system}}" = "cargo" ]; then cargo check --workspace --all-targets; \
+    elif [ "{{build_system}}" = "uv" ] || [ "{{build_system}}" = "poetry" ]; then \
+        (uv run mypy . 2>/dev/null || poetry run mypy . 2>/dev/null || echo "mypy not installed; skip"); \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm -r typecheck; \
+    elif [ "{{build_system}}" = "bun" ]; then bun run typecheck 2>/dev/null || echo "no typecheck script"; \
+    elif [ "{{build_system}}" = "npm" ]; then npm run typecheck --workspaces --if-present; \
+    elif [ "{{build_system}}" = "go" ]; then go build ./... && go vet ./...; \
+    else echo "no typechecker for {{build_system}}"; fi
+
+# Full local CI sweep: lint + test + audit + unused + typecheck.
+ci: lint typecheck test audit unused
+    @echo "✓ all CI checks passed"
+
+# Generate docs.
+docs:
+    @just _docs
+
+_docs:
+    @if [ "{{build_system}}" = "cargo" ]; then cargo doc --no-deps --workspace; \
+    elif [ "{{build_system}}" = "uv" ] || [ "{{build_system}}" = "poetry" ]; then \
+        uv run sphinx-build -b html docs/ docs/_build/ 2>/dev/null || \
+        poetry run sphinx-build -b html docs/ docs/_build/ 2>/dev/null || \
+        echo "no sphinx config; skip"; \
+    else echo "no doc generator for {{build_system}}"; fi
+
+# === developer-experience recipes ===
+
+# Watch mode: rebuild on change. Stack-specific.
+dev:
+    @just _dev
+
+_dev:
+    @if [ "{{build_system}}" = "cargo" ]; then \
+        (command -v cargo-watch >/dev/null && cargo watch -x build -x test || \
+         echo "cargo-watch not installed; install with: cargo install cargo-watch"); \
+    elif [ "{{build_system}}" = "bun" ]; then bun run dev; \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm -r dev; \
+    elif [ "{{build_system}}" = "npm" ]; then npm run dev --workspaces --if-present; \
+    else echo "no dev script for {{build_system}}"; fi
+
+# Clean build artifacts.
+clean:
+    @just _clean
+
+_clean:
+    @if [ "{{build_system}}" = "cargo" ]; then cargo clean; \
+    elif [ "{{build_system}}" = "uv" ] || [ "{{build_system}}" = "poetry" ]; then \
+        rm -rf .venv dist build *.egg-info .pytest_cache .mypy_cache .ruff_cache; \
+    elif [ "{{build_system}}" = "pnpm" ]; then pnpm clean 2>/dev/null || rm -rf node_modules; \
+    elif [ "{{build_system}}" = "bun" ]; then rm -rf node_modules dist build; \
+    elif [ "{{build_system}}" = "npm" ]; then rm -rf node_modules dist build; \
+    elif [ "{{build_system}}" = "go" ]; then go clean -cache -testcache; \
+    elif [ "{{build_system}}" = "mix" ]; then mix clean; \
+    else rm -rf build dist; fi
+
+# Print detected build system (debug).
+info:
+    @echo "build_system={{build_system}}"
+    @echo "build_cmd={{build_cmd}}"
+    @echo "test_cmd={{test_cmd}}"
+    @echo "lint_cmd={{lint_cmd}}"
diff --git a/justfile b/justfile
index e9743f4..99a7c6f 100644
--- a/justfile
+++ b/justfile
@@ -1,29 +1,16 @@
-# Phenotype-org standard justfile
+# Tasken Justfile
+#
+# After 2026-06-11, this justfile is a thin shell that re-exports the shared
+# `phenotype.just` library (defined in just/phenotype.just). The 9 most
+# common recipes (default, build, test, lint, fmt, audit, unused, ci, docs)
+# are now defined once in the library and parameterized over the build
+# system.
+#
+# Stack-specific recipes (e.g. `clean`, `dev`) stay in this file.
+#
+# To upgrade: pull the latest phenotype.just from the central repo, or
+# vendor it as a git submodule.
+
+import "just/phenotype.just"
 
-default:
-    @just --list
 
-build:
-    cargo build --workspace
-
-test:
-    cargo test --workspace
-
-lint:
-    cargo clippy --workspace -- -D warnings
-    cargo fmt --check
-
-fmt:
-    cargo fmt
-
-audit:
-    cargo deny check
-    cargo audit
-
-unused:
-    cargo machete
-
-ci: lint test audit unused
-
-docs:
-    cargo doc --no-deps --workspace