diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..4674eda
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,82 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.25'
+          cache: true
+
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v8
+        with:
+          version: latest
+          args: --timeout=5m
+
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache: true
+
+      - name: Run tests
+        run: go test -v -race -coverprofile=coverage.out -covermode=atomic ./...
+
+      - name: Upload coverage
+        uses: codecov/codecov-action@v5
+        with:
+          files: coverage.out
+          fail_ci_if_error: false
+
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        goos: [linux, darwin, windows]
+        goarch: [amd64, arm64]
+        exclude:
+          - goos: windows
+            goarch: arm64
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version: '1.25'
+          cache: true
+
+      - name: Build
+        env:
+          GOOS: ${{ matrix.goos }}
+          GOARCH: ${{ matrix.goarch }}
+        run: |
+          go build -ldflags="-s -w" -o azswitch-${{ matrix.goos }}-${{ matrix.goarch }}${{ matrix.goos == 'windows' && '.exe' || '' }} ./cmd/azswitch
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: azswitch-${{ matrix.goos }}-${{ matrix.goarch }}
+          path: azswitch-${{ matrix.goos }}-${{ matrix.goarch }}*
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
new file mode 100644
index 0000000..ada1b5d
--- /dev/null
+++ b/.github/workflows/release.yml
@@ -0,0 +1,48 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*.*.*'
+
+permissions:
+  contents: write
+  packages: write
+
+jobs:
+  goreleaser:
+    name: GoReleaser
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Set up Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.25'
+          cache: true
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Run GoReleaser
+        uses: goreleaser/goreleaser-action@v6
+        with:
+          distribution: goreleaser
+          version: '~> v2'
+          args: release --clean
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..052b3c1
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,29 @@
+# Build output
+/bin/
+/dist/
+
+# Test binary
+*.test
+
+# Coverage reports
+/coverage/
+
+# Dependency directories
+vendor/
+
+# Go workspace file
+go.work
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Debug
+debug.log
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..4e5bd56
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,75 @@
+version: "2"
+run:
+  issues-exit-code: 1
+linters:
+  enable:
+    - gocritic
+    - misspell
+    - revive
+    - unconvert
+  settings:
+    gocritic:
+      disabled-checks:
+        - hugeParam
+      enabled-tags:
+        - diagnostic
+        - style
+        - performance
+    misspell:
+      locale: US
+    revive:
+      rules:
+        - name: blank-imports
+        - name: context-as-argument
+        - name: context-keys-type
+        - name: dot-imports
+        - name: error-return
+        - name: error-strings
+        - name: error-naming
+        - name: exported
+        - name: if-return
+        - name: increment-decrement
+        - name: var-naming
+        - name: var-declaration
+        - name: package-comments
+        - name: range
+        - name: receiver-naming
+        - name: time-naming
+        - name: unexported-return
+        - name: indent-error-flow
+        - name: errorf
+  exclusions:
+    generated: lax
+    presets:
+      - comments
+      - common-false-positives
+      - legacy
+      - std-error-handling
+    rules:
+      - linters:
+          - errcheck
+          - gocritic
+        path: _test\.go
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
+issues:
+  max-issues-per-linter: 0
+  max-same-issues: 0
+formatters:
+  enable:
+    - gofmt
+    - goimports
+  settings:
+    gofmt:
+      simplify: true
+    goimports:
+      local-prefixes:
+        - github.com/l2D/azswitch
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
diff --git a/.goreleaser.yml b/.goreleaser.yml
new file mode 100644
index 0000000..7390603
--- /dev/null
+++ b/.goreleaser.yml
@@ -0,0 +1,127 @@
+# yaml-language-server: $schema=https://goreleaser.com/static/schema.json
+version: 2
+
+before:
+  hooks:
+    - go mod tidy
+
+builds:
+  - id: azswitch
+    main: ./cmd/azswitch
+    binary: azswitch
+    env:
+      - CGO_ENABLED=0
+    goos:
+      - linux
+      - darwin
+      - windows
+    goarch:
+      - amd64
+      - arm64
+    ignore:
+      - goos: windows
+        goarch: arm64
+    ldflags:
+      - -s -w
+      - -X github.com/l2D/azswitch/internal/version.Version={{.Version}}
+      - -X github.com/l2D/azswitch/internal/version.CommitSHA={{.Commit}}
+      - -X github.com/l2D/azswitch/internal/version.BuildTime={{.Date}}
+
+archives:
+  - id: default
+    name_template: '{{ .ProjectName }}_{{ .Version }}_{{ .Os }}_{{ .Arch }}'
+    format: tar.gz
+    format_overrides:
+      - goos: windows
+        format: zip
+    files:
+      - LICENSE
+      - README.md
+
+checksum:
+  name_template: 'checksums.txt'
+
+snapshot:
+  name_template: '{{ incpatch .Version }}-next'
+
+changelog:
+  sort: desc
+  use: github
+  groups:
+    - title: Features
+      regexp: '^.*?feat(\([[:word:]]+\))??!?:.+$'
+      order: 0
+    - title: Bug Fixes
+      regexp: '^.*?fix(\([[:word:]]+\))??!?:.+$'
+      order: 1
+    - title: Performance Improvements
+      regexp: '^.*?perf(\([[:word:]]+\))??!?:.+$'
+      order: 2
+    - title: Documentation
+      regexp: '^.*?docs(\([[:word:]]+\))??!?:.+$'
+      order: 3
+    - title: Others
+      order: 999
+  filters:
+    exclude:
+      - '^style:'
+      - '^chore:'
+      - '^ci:'
+
+release:
+  github:
+    owner: l2D
+    name: azswitch
+  draft: false
+  prerelease: auto
+  footer: |
+    ## Docker Image
+    ```
+    docker pull ghcr.io/l2d/azswitch:{{ .Tag }}
+    ```
+    
+    ## Quick Install
+    ```bash
+    # Go install
+    go install github.com/l2D/azswitch/cmd/azswitch@{{ .Tag }}
+    ```
+
+dockers:
+  - image_templates:
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-amd64'
+    dockerfile: Dockerfile
+    use: buildx
+    build_flag_templates:
+      - '--pull'
+      - '--platform=linux/amd64'
+      - '--label=org.opencontainers.image.created={{.Date}}'
+      - '--label=org.opencontainers.image.title={{.ProjectName}}'
+      - '--label=org.opencontainers.image.revision={{.FullCommit}}'
+      - '--label=org.opencontainers.image.version={{.Version}}'
+      - '--label=org.opencontainers.image.source={{.GitURL}}'
+    goarch: amd64
+
+  - image_templates:
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-arm64'
+    dockerfile: Dockerfile
+    use: buildx
+    build_flag_templates:
+      - '--pull'
+      - '--platform=linux/arm64'
+      - '--label=org.opencontainers.image.created={{.Date}}'
+      - '--label=org.opencontainers.image.title={{.ProjectName}}'
+      - '--label=org.opencontainers.image.revision={{.FullCommit}}'
+      - '--label=org.opencontainers.image.version={{.Version}}'
+      - '--label=org.opencontainers.image.source={{.GitURL}}'
+    goarch: arm64
+
+docker_manifests:
+  - name_template: 'ghcr.io/l2d/azswitch:{{ .Tag }}'
+    image_templates:
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-amd64'
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-arm64'
+
+  - name_template: 'ghcr.io/l2d/azswitch:latest'
+    image_templates:
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-amd64'
+      - 'ghcr.io/l2d/azswitch:{{ .Tag }}-arm64'
diff --git a/.mise.toml b/.mise.toml
new file mode 100644
index 0000000..939f37e
--- /dev/null
+++ b/.mise.toml
@@ -0,0 +1,10 @@
+[tools]
+act = "0.2.84"
+actionlint = "1.7.10"
+azure-cli = "2.82.0"
+gitleaks = "8.24.3"
+go = "1.25.6"
+golangci-lint = "2.8.0"
+pre-commit = "4.5.1"
+trivy = "0.68.2"
+yamlfmt = "0.21.0"
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..789e4b1
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,32 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+  # Go formatting
+  - repo: https://github.com/tekwizely/pre-commit-golang
+    rev: v1.0.0-rc.4
+    hooks:
+      - id: go-fmt
+        args: [-w]
+
+  # Go linting with golangci-lint v2 (includes formatters: gofmt, goimports)
+  - repo: https://github.com/golangci/golangci-lint
+    rev: v2.8.0
+    hooks:
+      - id: golangci-lint
+        args: [--config=.golangci.yml, --fix]
+
+  # Gitleaks - Secret scanning
+  - repo: https://github.com/gitleaks/gitleaks
+    rev: v8.30.0
+    hooks:
+      - id: gitleaks
+
+  # Trivy - Security scanning for filesystem
+  - repo: local
+    hooks:
+      - id: trivy-fs
+        name: Trivy filesystem scan
+        entry: trivy fs --exit-code 1 --severity HIGH,CRITICAL --scanners vuln,misconfig,secret .
+        language: system
+        pass_filenames: false
+        stages: [pre-commit]
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..d750354
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,110 @@
+# Contributing to azswitch
+
+Thank you for your interest in contributing to azswitch! This document provides guidelines and information about contributing.
+
+## Development Setup
+
+### Prerequisites
+
+- Go 1.25 or later
+- Azure CLI (for testing)
+- golangci-lint (for linting)
+- Docker (optional, for container builds)
+
+### Getting Started
+
+1. Fork the repository
+2. Clone your fork:
+
+   ```bash
+   git clone https://github.com/YOUR_USERNAME/azswitch.git
+   cd azswitch
+   ```
+
+3. Install dependencies:
+
+   ```bash
+   go mod download
+   ```
+
+4. Build:
+
+   ```bash
+   make build
+   ```
+
+5. Run tests:
+
+   ```bash
+   make test
+   ```
+
+## Making Changes
+
+### Code Style
+
+- Follow standard Go conventions
+- Run `make fmt` before committing
+- Run `make lint` to check for issues
+- Write tests for new functionality
+
+### Commit Messages
+
+This project follows [Conventional Commits](https://www.conventionalcommits.org/):
+
+- `feat:` - New features
+- `fix:` - Bug fixes
+- `docs:` - Documentation changes
+- `refactor:` - Code refactoring
+- `test:` - Test changes
+- `chore:` - Maintenance tasks
+
+Example:
+
+```sh
+feat(tui): add search filtering for subscriptions
+
+- Add fuzzy search to subscription list
+- Highlight matching characters
+```
+
+### Pull Requests
+
+1. Create a feature branch from `main`
+2. Make your changes
+3. Run tests and linting
+4. Push your branch
+5. Open a Pull Request
+
+## Project Structure
+
+```sh
+azswitch/
+├── cmd/azswitch/       # Application entry point
+├── internal/
+│   ├── azure/          # Azure CLI wrapper
+│   ├── tui/            # Bubble Tea TUI
+│   └── version/        # Version info
+├── .github/workflows/  # CI/CD
+└── Makefile           # Build automation
+```
+
+## Testing
+
+### Running Tests
+
+```bash
+# Run all tests
+make test
+
+# Run with coverage
+make coverage
+```
+
+### Mock Client
+
+Use `azure.NewMockClient()` for testing TUI components without Azure CLI.
+
+## Questions?
+
+Feel free to open an issue for questions or discussions.
diff --git a/Dockerfile b/Dockerfile
new file mode 100644
index 0000000..212fd67
--- /dev/null
+++ b/Dockerfile
@@ -0,0 +1,42 @@
+# Build stage
+FROM golang:1.25-alpine AS builder
+
+RUN apk add --no-cache git ca-certificates
+
+WORKDIR /app
+
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o azswitch ./cmd/azswitch
+
+# Runtime stage with Azure CLI
+FROM mcr.microsoft.com/azure-cli:2.82.0
+
+LABEL org.opencontainers.image.title="azswitch"
+LABEL org.opencontainers.image.description="TUI for switching Azure tenants and subscriptions"
+LABEL org.opencontainers.image.source="https://github.com/l2D/azswitch"
+LABEL org.opencontainers.image.licenses="MIT"
+
+# Create non-root user
+RUN tdnf install -y shadow-utils && \
+    groupadd -g 1000 azswitch && \
+    useradd -u 1000 -g azswitch -d /home/azswitch -s /bin/sh -m azswitch && \
+    tdnf clean all
+
+# Copy binary from builder
+COPY --from=builder /app/azswitch /usr/local/bin/azswitch
+
+# Set up Azure CLI cache directory with proper ownership
+RUN mkdir -p /home/azswitch/.azure && \
+    chown -R azswitch:azswitch /home/azswitch/.azure
+
+USER azswitch
+WORKDIR /home/azswitch
+
+ENTRYPOINT ["/usr/local/bin/azswitch"]
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..b3bbf45
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,98 @@
+.PHONY: build test lint clean install run fmt tidy coverage setup pre-commit
+
+# Build variables
+BINARY_NAME=azswitch
+VERSION?=$(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
+COMMIT_SHA?=$(shell git rev-parse --short HEAD 2>/dev/null || echo "unknown")
+BUILD_TIME=$(shell date -u '+%Y-%m-%dT%H:%M:%SZ')
+LDFLAGS=-ldflags "-s -w -X github.com/l2D/azswitch/internal/version.Version=$(VERSION) -X github.com/l2D/azswitch/internal/version.CommitSHA=$(COMMIT_SHA) -X github.com/l2D/azswitch/internal/version.BuildTime=$(BUILD_TIME)"
+
+# Go commands
+GOCMD=go
+GOBUILD=$(GOCMD) build
+GOTEST=$(GOCMD) test
+GOGET=$(GOCMD) get
+GOFMT=$(GOCMD) fmt
+GOMOD=$(GOCMD) mod
+
+# Default target
+all: lint test build
+
+# Build the binary
+build:
+	@mkdir -p bin
+	$(GOBUILD) $(LDFLAGS) -o bin/$(BINARY_NAME) ./cmd/azswitch
+
+# Build for all platforms
+build-all:
+	@mkdir -p dist
+	GOOS=darwin GOARCH=amd64 $(GOBUILD) $(LDFLAGS) -o dist/$(BINARY_NAME)-darwin-amd64 ./cmd/azswitch
+	GOOS=darwin GOARCH=arm64 $(GOBUILD) $(LDFLAGS) -o dist/$(BINARY_NAME)-darwin-arm64 ./cmd/azswitch
+	GOOS=linux GOARCH=amd64 $(GOBUILD) $(LDFLAGS) -o dist/$(BINARY_NAME)-linux-amd64 ./cmd/azswitch
+	GOOS=linux GOARCH=arm64 $(GOBUILD) $(LDFLAGS) -o dist/$(BINARY_NAME)-linux-arm64 ./cmd/azswitch
+	GOOS=windows GOARCH=amd64 $(GOBUILD) $(LDFLAGS) -o dist/$(BINARY_NAME)-windows-amd64.exe ./cmd/azswitch
+
+# Run tests
+test:
+	$(GOTEST) -v -race ./...
+
+# Run tests with coverage
+coverage:
+	@mkdir -p coverage
+	$(GOTEST) -v -race -coverprofile=coverage/coverage.out -covermode=atomic ./...
+	$(GOCMD) tool cover -html=coverage/coverage.out -o coverage/coverage.html
+
+# Run linter
+lint:
+	golangci-lint run ./...
+
+# Format code
+fmt:
+	$(GOFMT) ./...
+
+# Tidy dependencies
+tidy:
+	$(GOMOD) tidy
+
+# Install the binary
+install: build
+	cp bin/$(BINARY_NAME) $(GOPATH)/bin/
+
+# Run the application
+run: build
+	./bin/$(BINARY_NAME)
+
+# Clean build artifacts
+clean:
+	rm -rf bin/
+	rm -rf dist/
+	rm -rf coverage/
+
+# Development: run with live reload (requires air)
+dev:
+	air
+
+# Setup pre-commit hooks
+setup:
+	pre-commit install
+
+# Run pre-commit on all files
+pre-commit:
+	pre-commit run --all-files
+
+# Help
+help:
+	@echo "Available targets:"
+	@echo "  build      - Build the binary"
+	@echo "  build-all  - Build for all platforms"
+	@echo "  test       - Run tests"
+	@echo "  coverage   - Run tests with coverage report"
+	@echo "  lint       - Run linter"
+	@echo "  fmt        - Format code"
+	@echo "  tidy       - Tidy dependencies"
+	@echo "  install    - Install binary to GOPATH/bin"
+	@echo "  run        - Build and run"
+	@echo "  clean      - Remove build artifacts"
+	@echo "  dev        - Run with live reload (requires air)"
+	@echo "  setup      - Install pre-commit hooks"
+	@echo "  pre-commit - Run pre-commit on all files"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..7d8b12a
--- /dev/null
+++ b/README.md
@@ -0,0 +1,135 @@
+# azswitch
+
+A TUI application for switching Azure tenants, directories, and subscriptions.
+
+![Demo](docs/demo.gif)
+
+## Features
+
+- **Interactive TUI** - Navigate with keyboard (vim-style j/k or arrows)
+- **View Current Account** - See active user, tenant, and subscription
+- **Switch Subscriptions** - Quick selection from available subscriptions
+- **Switch Tenants** - Re-authenticate to a different Azure AD tenant
+- **CLI Mode** - Non-interactive flags for scripting
+
+## Installation
+
+### Homebrew (macOS/Linux)
+
+```bash
+brew install l2D/tap/azswitch
+```
+
+### Go Install
+
+```bash
+go install github.com/l2D/azswitch/cmd/azswitch@latest
+```
+
+### Binary Download
+
+Download the latest release from [GitHub Releases](https://github.com/l2D/azswitch/releases).
+
+### Docker
+
+```bash
+docker pull ghcr.io/l2d/azswitch
+```
+
+#### Running with existing Azure credentials
+
+Mount your local Azure CLI configuration:
+
+```bash
+docker run --rm -it -v ~/.azure:/home/azswitch/.azure ghcr.io/l2d/azswitch
+```
+
+#### Running with CLI flags
+
+```bash
+# Show current account
+docker run --rm -v ~/.azure:/home/azswitch/.azure ghcr.io/l2d/azswitch --current
+
+# List subscriptions
+docker run --rm -v ~/.azure:/home/azswitch/.azure ghcr.io/l2d/azswitch --list
+```
+
+#### Interactive shell with Azure CLI
+
+To access the container shell with Azure CLI:
+
+```bash
+docker run --rm -it -v ~/.azure:/home/azswitch/.azure --entrypoint /bin/sh ghcr.io/l2d/azswitch
+```
+
+#### Building locally
+
+```bash
+docker build -t azswitch .
+docker run --rm -it -v ~/.azure:/home/azswitch/.azure azswitch
+```
+
+## Prerequisites
+
+- [Azure CLI](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli) must be installed
+- Must be logged in (`az login`)
+
+## Usage
+
+### Interactive Mode (Default)
+
+```bash
+azswitch
+```
+
+### CLI Flags
+
+```bash
+# Show current account
+azswitch --current
+
+# List all subscriptions
+azswitch --list
+
+# Switch to subscription by name or ID
+azswitch --subscription "My Subscription"
+azswitch --subscription xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+
+# Switch to a different tenant
+azswitch --tenant xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+```
+
+## Key Bindings
+
+| Key | Action |
+|-----|--------|
+| `j` / `Down` | Move cursor down |
+| `k` / `Up` | Move cursor up |
+| `Enter` | Select item |
+| `Tab` | Switch between subscriptions/tenants view |
+| `?` | Toggle help |
+| `q` / `Ctrl+C` | Quit |
+
+## Development
+
+### Build
+
+```bash
+make build
+```
+
+### Test
+
+```bash
+make test
+```
+
+### Lint
+
+```bash
+make lint
+```
+
+## License
+
+[MIT](LICENSE)
diff --git a/cmd/azswitch/main.go b/cmd/azswitch/main.go
new file mode 100644
index 0000000..dd28091
--- /dev/null
+++ b/cmd/azswitch/main.go
@@ -0,0 +1,157 @@
+// Package main is the entry point for azswitch.
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/spf13/cobra"
+
+	"github.com/l2D/azswitch/internal/azure"
+	"github.com/l2D/azswitch/internal/tui"
+	"github.com/l2D/azswitch/internal/version"
+)
+
+var (
+	// Flags
+	flagList         bool
+	flagCurrent      bool
+	flagSubscription string
+	flagTenant       string
+)
+
+func main() {
+	if err := rootCmd.Execute(); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+var rootCmd = &cobra.Command{
+	Use:   "azswitch",
+	Short: "Switch Azure tenants, directories, and subscriptions",
+	Long: `azswitch is a TUI application for switching Azure tenants, 
+directories, and subscriptions.
+
+Run without flags to enter interactive mode.`,
+	Version: version.Short(),
+	RunE:    run,
+}
+
+func init() {
+	rootCmd.Flags().BoolVarP(&flagList, "list", "l", false, "List all subscriptions")
+	rootCmd.Flags().BoolVarP(&flagCurrent, "current", "c", false, "Show current account")
+	rootCmd.Flags().StringVarP(&flagSubscription, "subscription", "s", "", "Switch to subscription by ID or name")
+	rootCmd.Flags().StringVarP(&flagTenant, "tenant", "t", "", "Switch to tenant by ID")
+
+	rootCmd.SetVersionTemplate("{{.Version}}\n")
+}
+
+func run(_ *cobra.Command, _ []string) error {
+	client := azure.NewCLIClient()
+	ctx := context.Background()
+
+	// Check if Azure CLI is installed
+	if err := client.CheckCLI(ctx); err != nil {
+		//nolint:staticcheck // ST1005: Azure CLI is a proper noun
+		return fmt.Errorf("Azure CLI is not installed. Install from: https://docs.microsoft.com/en-us/cli/azure/install-azure-cli")
+	}
+
+	// Check if logged in
+	if err := client.CheckLogin(ctx); err != nil {
+		return fmt.Errorf("not logged in to Azure CLI. Run: az login")
+	}
+
+	// Handle non-interactive flags
+	if flagCurrent {
+		return showCurrent(ctx, client)
+	}
+
+	if flagList {
+		return listSubscriptions(ctx, client)
+	}
+
+	if flagSubscription != "" {
+		return switchSubscription(ctx, client, flagSubscription)
+	}
+
+	if flagTenant != "" {
+		return switchTenant(ctx, client, flagTenant)
+	}
+
+	// Interactive mode
+	return runInteractive(client)
+}
+
+func showCurrent(ctx context.Context, client azure.Client) error {
+	account, err := client.GetCurrentAccount(ctx)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println("Current Azure Account:")
+	fmt.Printf("  User:         %s\n", account.User.Name)
+	fmt.Printf("  Tenant:       %s (%s)\n", account.TenantDisplayName, account.TenantID)
+	fmt.Printf("  Subscription: %s\n", account.Name)
+	fmt.Printf("  ID:           %s\n", account.ID)
+	fmt.Printf("  State:        %s\n", account.State)
+
+	return nil
+}
+
+func listSubscriptions(ctx context.Context, client azure.Client) error {
+	subs, err := client.ListSubscriptions(ctx)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println("Available Subscriptions:")
+	for i := range subs {
+		sub := &subs[i]
+		indicator := "  "
+		if sub.IsDefault {
+			indicator = "* "
+		}
+		fmt.Printf("%s%s\n", indicator, sub.Name)
+		fmt.Printf("    ID:    %s\n", sub.ID)
+		fmt.Printf("    State: %s\n", sub.State)
+	}
+
+	return nil
+}
+
+func switchSubscription(ctx context.Context, client azure.Client, subscription string) error {
+	fmt.Printf("Switching to subscription: %s\n", subscription)
+
+	if err := client.SetSubscription(ctx, subscription); err != nil {
+		return fmt.Errorf("failed to switch subscription: %w", err)
+	}
+
+	fmt.Println("Successfully switched subscription")
+	return showCurrent(ctx, client)
+}
+
+func switchTenant(ctx context.Context, client azure.Client, tenant string) error {
+	fmt.Printf("Switching to tenant: %s\n", tenant)
+	fmt.Println("This will open a browser for authentication...")
+
+	if err := client.LoginToTenant(ctx, tenant); err != nil {
+		return fmt.Errorf("failed to switch tenant: %w", err)
+	}
+
+	fmt.Println("Successfully switched tenant")
+	return showCurrent(ctx, client)
+}
+
+func runInteractive(client azure.Client) error {
+	model := tui.NewModel(client)
+
+	p := tea.NewProgram(model, tea.WithAltScreen())
+	if _, err := p.Run(); err != nil {
+		return fmt.Errorf("error running TUI: %w", err)
+	}
+
+	return nil
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..42d712c
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,32 @@
+module github.com/l2D/azswitch
+
+go 1.25.6
+
+require (
+	github.com/charmbracelet/bubbles v0.21.0
+	github.com/charmbracelet/bubbletea v1.3.10
+	github.com/charmbracelet/lipgloss v1.1.0
+	github.com/spf13/cobra v1.10.2
+)
+
+require (
+	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
+	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
+	github.com/charmbracelet/x/ansi v0.10.1 // indirect
+	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
+	github.com/charmbracelet/x/term v0.2.1 // indirect
+	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-localereader v0.0.1 // indirect
+	github.com/mattn/go-runewidth v0.0.16 // indirect
+	github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 // indirect
+	github.com/muesli/cancelreader v0.2.2 // indirect
+	github.com/muesli/termenv v0.16.0 // indirect
+	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/spf13/pflag v1.0.9 // indirect
+	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
+	golang.org/x/sys v0.36.0 // indirect
+	golang.org/x/text v0.3.8 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..e3b12dd
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,59 @@
+github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
+github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
+github.com/aymanbagabas/go-udiff v0.2.0 h1:TK0fH4MteXUDspT88n8CKzvK0X9O2xu9yQjWpi6yML8=
+github.com/aymanbagabas/go-udiff v0.2.0/go.mod h1:RE4Ex0qsGkTAJoQdQQCA0uG+nAzJO/pI/QwceO5fgrA=
+github.com/charmbracelet/bubbles v0.21.0 h1:9TdC97SdRVg/1aaXNVWfFH3nnLAwOXr8Fn6u6mfQdFs=
+github.com/charmbracelet/bubbles v0.21.0/go.mod h1:HF+v6QUR4HkEpz62dx7ym2xc71/KBHg+zKwJtMw+qtg=
+github.com/charmbracelet/bubbletea v1.3.10 h1:otUDHWMMzQSB0Pkc87rm691KZ3SWa4KUlvF9nRvCICw=
+github.com/charmbracelet/bubbletea v1.3.10/go.mod h1:ORQfo0fk8U+po9VaNvnV95UPWA1BitP1E0N6xJPlHr4=
+github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc h1:4pZI35227imm7yK2bGPcfpFEmuY1gc2YSTShr4iJBfs=
+github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc/go.mod h1:X4/0JoqgTIPSFcRA/P6INZzIuyqdFY5rm8tb41s9okk=
+github.com/charmbracelet/lipgloss v1.1.0 h1:vYXsiLHVkK7fp74RkV7b2kq9+zDLoEU4MZoFqR/noCY=
+github.com/charmbracelet/lipgloss v1.1.0/go.mod h1:/6Q8FR2o+kj8rz4Dq0zQc3vYf7X+B0binUUBwA0aL30=
+github.com/charmbracelet/x/ansi v0.10.1 h1:rL3Koar5XvX0pHGfovN03f5cxLbCF2YvLeyz7D2jVDQ=
+github.com/charmbracelet/x/ansi v0.10.1/go.mod h1:3RQDQ6lDnROptfpWuUVIUG64bD2g2BgntdxH0Ya5TeE=
+github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd h1:vy0GVL4jeHEwG5YOXDmi86oYw2yuYUGqz6a8sLwg0X8=
+github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd/go.mod h1:xe0nKWGd3eJgtqZRaN9RjMtK7xUYchjzPr7q6kcvCCs=
+github.com/charmbracelet/x/exp/golden v0.0.0-20241011142426-46044092ad91 h1:payRxjMjKgx2PaCWLZ4p3ro9y97+TVLZNaRZgJwSVDQ=
+github.com/charmbracelet/x/exp/golden v0.0.0-20241011142426-46044092ad91/go.mod h1:wDlXFlCrmJ8J+swcL/MnGUuYnqgQdW9rhSD61oNMb6U=
+github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
+github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
+github.com/cpuguy83/go-md2man/v2 v2.0.6/go.mod h1:oOW0eioCTA6cOiMLiUPZOpcVxMig6NIQQ7OS05n1F4g=
+github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f h1:Y/CXytFA4m6baUTXGLOoWe4PQhGxaX0KpnayAqC48p4=
+github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f/go.mod h1:vw97MGsxSvLiUE2X8qFplwetxpGLQrlU1Q9AUEIzCaM=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
+github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+github.com/mattn/go-localereader v0.0.1 h1:ygSAOl7ZXTx4RdPYinUpg6W99U8jWvWi9Ye2JC/oIi4=
+github.com/mattn/go-localereader v0.0.1/go.mod h1:8fBrzywKY7BI3czFoHkuzRoWE9C+EiG4R1k4Cjx5p88=
+github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
+github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6 h1:ZK8zHtRHOkbHy6Mmr5D264iyp3TiX5OmNcI5cIARiQI=
+github.com/muesli/ansi v0.0.0-20230316100256-276c6243b2f6/go.mod h1:CJlz5H+gyd6CUWT45Oy4q24RdLyn7Md9Vj2/ldJBSIo=
+github.com/muesli/cancelreader v0.2.2 h1:3I4Kt4BQjOR54NavqnDogx/MIoWBFa0StPA8ELUXHmA=
+github.com/muesli/cancelreader v0.2.2/go.mod h1:3XuTXfFS2VjM+HTLZY9Ak0l6eUKfijIfMUZ4EgX0QYo=
+github.com/muesli/termenv v0.16.0 h1:S5AlUN9dENB57rsbnkPyfdGuWIlkmzJjbFf0Tf5FWUc=
+github.com/muesli/termenv v0.16.0/go.mod h1:ZRfOIKPFDYQoDFF4Olj7/QJbW60Ol/kL1pU3VfY/Cnk=
+github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
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+github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.10.2 h1:DMTTonx5m65Ic0GOoRY2c16WCbHxOOw6xxezuLaBpcU=
+github.com/spf13/cobra v1.10.2/go.mod h1:7C1pvHqHw5A4vrJfjNwvOdzYu0Gml16OCs2GRiTUUS4=
+github.com/spf13/pflag v1.0.9 h1:9exaQaMOCwffKiiiYk6/BndUBv+iRViNW+4lEMi0PvY=
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+go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
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+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.36.0 h1:KVRy2GtZBrk1cBYA7MKu5bEZFxQk4NIDV6RLVcC8o0k=
+golang.org/x/sys v0.36.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
+golang.org/x/text v0.3.8 h1:nAL+RVCQ9uMn3vJZbV+MRnydTJFPf8qqY42YiA6MrqY=
+golang.org/x/text v0.3.8/go.mod h1:E6s5w1FMmriuDzIBO73fBruAKo1PCIq6d2Q6DHfQ8WQ=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/internal/azure/client.go b/internal/azure/client.go
new file mode 100644
index 0000000..b2a0d82
--- /dev/null
+++ b/internal/azure/client.go
@@ -0,0 +1,153 @@
+package azure
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// Common errors.
+var (
+	ErrAzureCLINotInstalled = errors.New("azure CLI is not installed")
+	ErrNotLoggedIn          = errors.New("not logged in to Azure CLI")
+	ErrCommandFailed        = errors.New("azure CLI command failed")
+)
+
+// Client defines the interface for Azure CLI operations.
+type Client interface {
+	// CheckCLI verifies that Azure CLI is installed.
+	CheckCLI(ctx context.Context) error
+
+	// CheckLogin verifies that the user is logged in.
+	CheckLogin(ctx context.Context) error
+
+	// GetCurrentAccount returns the current Azure account information.
+	GetCurrentAccount(ctx context.Context) (*Account, error)
+
+	// ListSubscriptions returns all available subscriptions.
+	ListSubscriptions(ctx context.Context) ([]Subscription, error)
+
+	// ListTenants returns all available tenants.
+	ListTenants(ctx context.Context) ([]Tenant, error)
+
+	// SetSubscription switches to the specified subscription.
+	SetSubscription(ctx context.Context, subscriptionIDOrName string) error
+
+	// LoginToTenant logs in to a specific tenant.
+	LoginToTenant(ctx context.Context, tenantID string) error
+}
+
+// CLIClient implements Client using the Azure CLI.
+type CLIClient struct {
+	// azPath is the path to the az CLI binary.
+	azPath string
+}
+
+// NewCLIClient creates a new Azure CLI client.
+func NewCLIClient() *CLIClient {
+	return &CLIClient{
+		azPath: "az",
+	}
+}
+
+// CheckCLI verifies that Azure CLI is installed.
+func (c *CLIClient) CheckCLI(ctx context.Context) error {
+	_, err := exec.LookPath(c.azPath)
+	if err != nil {
+		return ErrAzureCLINotInstalled
+	}
+	return nil
+}
+
+// CheckLogin verifies that the user is logged in.
+func (c *CLIClient) CheckLogin(ctx context.Context) error {
+	_, err := c.GetCurrentAccount(ctx)
+	if err != nil {
+		if strings.Contains(err.Error(), "Please run 'az login'") ||
+			strings.Contains(err.Error(), "not logged in") {
+			return ErrNotLoggedIn
+		}
+		return err
+	}
+	return nil
+}
+
+// GetCurrentAccount returns the current Azure account information.
+func (c *CLIClient) GetCurrentAccount(ctx context.Context) (*Account, error) {
+	output, err := c.runCommand(ctx, "account", "show", "--output", "json")
+	if err != nil {
+		return nil, err
+	}
+
+	var account Account
+	if err := json.Unmarshal(output, &account); err != nil {
+		return nil, fmt.Errorf("failed to parse account: %w", err)
+	}
+
+	return &account, nil
+}
+
+// ListSubscriptions returns all available subscriptions.
+func (c *CLIClient) ListSubscriptions(ctx context.Context) ([]Subscription, error) {
+	output, err := c.runCommand(ctx, "account", "list", "--output", "json")
+	if err != nil {
+		return nil, err
+	}
+
+	var subscriptions []Subscription
+	if err := json.Unmarshal(output, &subscriptions); err != nil {
+		return nil, fmt.Errorf("failed to parse subscriptions: %w", err)
+	}
+
+	return subscriptions, nil
+}
+
+// ListTenants returns all available tenants.
+func (c *CLIClient) ListTenants(ctx context.Context) ([]Tenant, error) {
+	output, err := c.runCommand(ctx, "account", "tenant", "list", "--output", "json")
+	if err != nil {
+		return nil, err
+	}
+
+	var tenants []Tenant
+	if err := json.Unmarshal(output, &tenants); err != nil {
+		return nil, fmt.Errorf("failed to parse tenants: %w", err)
+	}
+
+	return tenants, nil
+}
+
+// SetSubscription switches to the specified subscription.
+func (c *CLIClient) SetSubscription(ctx context.Context, subscriptionIDOrName string) error {
+	_, err := c.runCommand(ctx, "account", "set", "--subscription", subscriptionIDOrName)
+	return err
+}
+
+// LoginToTenant logs in to a specific tenant.
+func (c *CLIClient) LoginToTenant(ctx context.Context, tenantID string) error {
+	_, err := c.runCommand(ctx, "login", "--tenant", tenantID, "--output", "none")
+	return err
+}
+
+// runCommand executes an Azure CLI command and returns the output.
+func (c *CLIClient) runCommand(ctx context.Context, args ...string) ([]byte, error) {
+	cmd := exec.CommandContext(ctx, c.azPath, args...)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	if err := cmd.Run(); err != nil {
+		errMsg := stderr.String()
+		if errMsg == "" {
+			errMsg = err.Error()
+		}
+		return nil, fmt.Errorf("%w: %s", ErrCommandFailed, strings.TrimSpace(errMsg))
+	}
+
+	return stdout.Bytes(), nil
+}
diff --git a/internal/azure/client_test.go b/internal/azure/client_test.go
new file mode 100644
index 0000000..3860aba
--- /dev/null
+++ b/internal/azure/client_test.go
@@ -0,0 +1,180 @@
+package azure
+
+import (
+	"context"
+	"testing"
+)
+
+func TestMockClient_GetCurrentAccount(t *testing.T) {
+	client := NewMockClient()
+	ctx := context.Background()
+
+	account, err := client.GetCurrentAccount(ctx)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if account.Name != "Test Subscription" {
+		t.Errorf("expected name 'Test Subscription', got '%s'", account.Name)
+	}
+
+	if account.User.Name != "test@example.com" {
+		t.Errorf("expected user 'test@example.com', got '%s'", account.User.Name)
+	}
+
+	if client.Calls.GetCurrentAccount != 1 {
+		t.Errorf("expected 1 call, got %d", client.Calls.GetCurrentAccount)
+	}
+}
+
+func TestMockClient_ListSubscriptions(t *testing.T) {
+	client := NewMockClient()
+	ctx := context.Background()
+
+	subs, err := client.ListSubscriptions(ctx)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(subs) != 2 {
+		t.Errorf("expected 2 subscriptions, got %d", len(subs))
+	}
+
+	if subs[0].Name != "Test Subscription 1" {
+		t.Errorf("expected 'Test Subscription 1', got '%s'", subs[0].Name)
+	}
+
+	if !subs[0].IsDefault {
+		t.Error("expected first subscription to be default")
+	}
+}
+
+func TestMockClient_ListTenants(t *testing.T) {
+	client := NewMockClient()
+	ctx := context.Background()
+
+	tenants, err := client.ListTenants(ctx)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(tenants) != 2 {
+		t.Errorf("expected 2 tenants, got %d", len(tenants))
+	}
+
+	if tenants[0].DisplayName != "Test Tenant" {
+		t.Errorf("expected 'Test Tenant', got '%s'", tenants[0].DisplayName)
+	}
+}
+
+func TestMockClient_SetSubscription(t *testing.T) {
+	client := NewMockClient()
+	ctx := context.Background()
+
+	err := client.SetSubscription(ctx, "test-subscription-id")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(client.Calls.SetSubscription) != 1 {
+		t.Errorf("expected 1 call, got %d", len(client.Calls.SetSubscription))
+	}
+
+	if client.Calls.SetSubscription[0] != "test-subscription-id" {
+		t.Errorf("expected 'test-subscription-id', got '%s'", client.Calls.SetSubscription[0])
+	}
+}
+
+func TestMockClient_LoginToTenant(t *testing.T) {
+	client := NewMockClient()
+	ctx := context.Background()
+
+	err := client.LoginToTenant(ctx, "test-tenant-id")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(client.Calls.LoginToTenant) != 1 {
+		t.Errorf("expected 1 call, got %d", len(client.Calls.LoginToTenant))
+	}
+
+	if client.Calls.LoginToTenant[0] != "test-tenant-id" {
+		t.Errorf("expected 'test-tenant-id', got '%s'", client.Calls.LoginToTenant[0])
+	}
+}
+
+func TestSubscription_Methods(t *testing.T) {
+	sub := Subscription{
+		Name: "My Subscription",
+		ID:   "00000000-0000-0000-0000-000000000001",
+	}
+
+	if sub.Title() != "My Subscription" {
+		t.Errorf("expected Title() to return 'My Subscription', got '%s'", sub.Title())
+	}
+
+	if sub.Description() != "00000000-0000-0000-0000-000000000001" {
+		t.Errorf("expected Description() to return subscription ID")
+	}
+
+	if sub.FilterValue() != "My Subscription" {
+		t.Errorf("expected FilterValue() to return name")
+	}
+}
+
+func TestTenant_Methods(t *testing.T) {
+	t.Run("with display name", func(t *testing.T) {
+		tenant := Tenant{
+			DisplayName:   "My Tenant",
+			DefaultDomain: "mytenant.onmicrosoft.com",
+			TenantID:      "00000000-0000-0000-0000-000000000002",
+		}
+
+		if tenant.Title() != "My Tenant" {
+			t.Errorf("expected Title() to return 'My Tenant', got '%s'", tenant.Title())
+		}
+
+		if tenant.FilterValue() != "My Tenant" {
+			t.Errorf("expected FilterValue() to return display name")
+		}
+	})
+
+	t.Run("without display name", func(t *testing.T) {
+		tenant := Tenant{
+			DefaultDomain: "mytenant.onmicrosoft.com",
+			TenantID:      "00000000-0000-0000-0000-000000000002",
+		}
+
+		if tenant.Title() != "mytenant.onmicrosoft.com" {
+			t.Errorf("expected Title() to return domain, got '%s'", tenant.Title())
+		}
+
+		if tenant.FilterValue() != "mytenant.onmicrosoft.com" {
+			t.Errorf("expected FilterValue() to return domain")
+		}
+	})
+
+	t.Run("description returns tenant ID", func(t *testing.T) {
+		tenant := Tenant{
+			TenantID: "00000000-0000-0000-0000-000000000002",
+		}
+
+		if tenant.Description() != "00000000-0000-0000-0000-000000000002" {
+			t.Errorf("expected Description() to return tenant ID")
+		}
+	})
+}
+
+func TestMockClient_CustomBehavior(t *testing.T) {
+	client := NewMockClient()
+
+	// Override default behavior
+	client.CheckCLIFunc = func(_ context.Context) error {
+		return ErrAzureCLINotInstalled
+	}
+
+	err := client.CheckCLI(context.Background())
+	if err != ErrAzureCLINotInstalled {
+		t.Errorf("expected ErrAzureCLINotInstalled, got %v", err)
+	}
+}
diff --git a/internal/azure/mock.go b/internal/azure/mock.go
new file mode 100644
index 0000000..e56c114
--- /dev/null
+++ b/internal/azure/mock.go
@@ -0,0 +1,151 @@
+package azure
+
+import (
+	"context"
+)
+
+// MockClient is a mock implementation of the Azure Client interface for testing.
+type MockClient struct {
+	// CheckCLIFunc is called when CheckCLI is invoked.
+	CheckCLIFunc func(ctx context.Context) error
+
+	// CheckLoginFunc is called when CheckLogin is invoked.
+	CheckLoginFunc func(ctx context.Context) error
+
+	// GetCurrentAccountFunc is called when GetCurrentAccount is invoked.
+	GetCurrentAccountFunc func(ctx context.Context) (*Account, error)
+
+	// ListSubscriptionsFunc is called when ListSubscriptions is invoked.
+	ListSubscriptionsFunc func(ctx context.Context) ([]Subscription, error)
+
+	// ListTenantsFunc is called when ListTenants is invoked.
+	ListTenantsFunc func(ctx context.Context) ([]Tenant, error)
+
+	// SetSubscriptionFunc is called when SetSubscription is invoked.
+	SetSubscriptionFunc func(ctx context.Context, subscriptionIDOrName string) error
+
+	// LoginToTenantFunc is called when LoginToTenant is invoked.
+	LoginToTenantFunc func(ctx context.Context, tenantID string) error
+
+	// Calls tracks function call history.
+	Calls struct {
+		CheckCLI          int
+		CheckLogin        int
+		GetCurrentAccount int
+		ListSubscriptions int
+		ListTenants       int
+		SetSubscription   []string
+		LoginToTenant     []string
+	}
+}
+
+// NewMockClient creates a new mock client with default implementations.
+func NewMockClient() *MockClient {
+	return &MockClient{
+		CheckCLIFunc: func(_ context.Context) error {
+			return nil
+		},
+		CheckLoginFunc: func(_ context.Context) error {
+			return nil
+		},
+		GetCurrentAccountFunc: func(_ context.Context) (*Account, error) {
+			return &Account{
+				Name:              "Test Subscription",
+				ID:                "00000000-0000-0000-0000-000000000001",
+				TenantID:          "00000000-0000-0000-0000-000000000002",
+				TenantDisplayName: "Test Tenant",
+				IsDefault:         true,
+				State:             "Enabled",
+				User: User{
+					Name: "test@example.com",
+					Type: "user",
+				},
+			}, nil
+		},
+		ListSubscriptionsFunc: func(_ context.Context) ([]Subscription, error) {
+			return []Subscription{
+				{
+					Name:              "Test Subscription 1",
+					ID:                "00000000-0000-0000-0000-000000000001",
+					TenantID:          "00000000-0000-0000-0000-000000000002",
+					TenantDisplayName: "Test Tenant",
+					IsDefault:         true,
+					State:             "Enabled",
+				},
+				{
+					Name:              "Test Subscription 2",
+					ID:                "00000000-0000-0000-0000-000000000003",
+					TenantID:          "00000000-0000-0000-0000-000000000002",
+					TenantDisplayName: "Test Tenant",
+					IsDefault:         false,
+					State:             "Enabled",
+				},
+			}, nil
+		},
+		ListTenantsFunc: func(_ context.Context) ([]Tenant, error) {
+			return []Tenant{
+				{
+					DisplayName:   "Test Tenant",
+					TenantID:      "00000000-0000-0000-0000-000000000002",
+					DefaultDomain: "test.onmicrosoft.com",
+				},
+				{
+					DisplayName:   "Another Tenant",
+					TenantID:      "00000000-0000-0000-0000-000000000004",
+					DefaultDomain: "another.onmicrosoft.com",
+				},
+			}, nil
+		},
+		SetSubscriptionFunc: func(_ context.Context, _ string) error {
+			return nil
+		},
+		LoginToTenantFunc: func(_ context.Context, _ string) error {
+			return nil
+		},
+	}
+}
+
+// CheckCLI implements Client.
+func (m *MockClient) CheckCLI(ctx context.Context) error {
+	m.Calls.CheckCLI++
+	return m.CheckCLIFunc(ctx)
+}
+
+// CheckLogin implements Client.
+func (m *MockClient) CheckLogin(ctx context.Context) error {
+	m.Calls.CheckLogin++
+	return m.CheckLoginFunc(ctx)
+}
+
+// GetCurrentAccount implements Client.
+func (m *MockClient) GetCurrentAccount(ctx context.Context) (*Account, error) {
+	m.Calls.GetCurrentAccount++
+	return m.GetCurrentAccountFunc(ctx)
+}
+
+// ListSubscriptions implements Client.
+func (m *MockClient) ListSubscriptions(ctx context.Context) ([]Subscription, error) {
+	m.Calls.ListSubscriptions++
+	return m.ListSubscriptionsFunc(ctx)
+}
+
+// ListTenants implements Client.
+func (m *MockClient) ListTenants(ctx context.Context) ([]Tenant, error) {
+	m.Calls.ListTenants++
+	return m.ListTenantsFunc(ctx)
+}
+
+// SetSubscription implements Client.
+func (m *MockClient) SetSubscription(ctx context.Context, subscriptionIDOrName string) error {
+	m.Calls.SetSubscription = append(m.Calls.SetSubscription, subscriptionIDOrName)
+	return m.SetSubscriptionFunc(ctx, subscriptionIDOrName)
+}
+
+// LoginToTenant implements Client.
+func (m *MockClient) LoginToTenant(ctx context.Context, tenantID string) error {
+	m.Calls.LoginToTenant = append(m.Calls.LoginToTenant, tenantID)
+	return m.LoginToTenantFunc(ctx, tenantID)
+}
+
+// Ensure MockClient implements Client.
+var _ Client = (*MockClient)(nil)
diff --git a/internal/azure/types.go b/internal/azure/types.go
new file mode 100644
index 0000000..3712f81
--- /dev/null
+++ b/internal/azure/types.go
@@ -0,0 +1,91 @@
+// Package azure provides Azure CLI wrapper functionality.
+package azure
+
+// Account represents the current Azure account information.
+type Account struct {
+	EnvironmentName   string `json:"environmentName"`
+	HomeTenantID      string `json:"homeTenantId"`
+	ID                string `json:"id"`
+	IsDefault         bool   `json:"isDefault"`
+	ManagedByTenants  []any  `json:"managedByTenants"`
+	Name              string `json:"name"`
+	State             string `json:"state"`
+	TenantDisplayName string `json:"tenantDisplayName"`
+	TenantID          string `json:"tenantId"`
+	User              User   `json:"user"`
+}
+
+// User represents the user information within an account.
+type User struct {
+	Name string `json:"name"`
+	Type string `json:"type"`
+}
+
+// Subscription represents an Azure subscription.
+type Subscription struct {
+	CloudName         string `json:"cloudName"`
+	HomeTenantID      string `json:"homeTenantId"`
+	ID                string `json:"id"`
+	IsDefault         bool   `json:"isDefault"`
+	ManagedByTenants  []any  `json:"managedByTenants"`
+	Name              string `json:"name"`
+	State             string `json:"state"`
+	TenantDisplayName string `json:"tenantDisplayName"`
+	TenantID          string `json:"tenantId"`
+	User              User   `json:"user"`
+}
+
+// Tenant represents an Azure AD tenant/directory.
+type Tenant struct {
+	DefaultDomain   string   `json:"defaultDomain"`
+	DisplayName     string   `json:"displayName"`
+	ID              string   `json:"id"`
+	TenantID        string   `json:"tenantId"`
+	TenantCategory  string   `json:"tenantCategory"`
+	TenantType      string   `json:"tenantType"`
+	Domains         []string `json:"domains,omitempty"`
+	CountryCode     string   `json:"countryCode,omitempty"`
+	TenantBrandName string   `json:"tenantBrandingLogoUrl,omitempty"`
+}
+
+// Title returns a display title for the subscription.
+func (s Subscription) Title() string {
+	return s.Name
+}
+
+// Description returns a description for the subscription.
+func (s Subscription) Description() string {
+	return s.ID
+}
+
+// FilterValue returns the value used for filtering.
+func (s Subscription) FilterValue() string {
+	return s.Name
+}
+
+// Title returns a display title for the tenant.
+func (t Tenant) Title() string {
+	if t.DisplayName != "" {
+		return t.DisplayName
+	}
+	if t.DefaultDomain != "" {
+		return t.DefaultDomain
+	}
+	return t.TenantID
+}
+
+// Description returns a description for the tenant.
+func (t Tenant) Description() string {
+	return t.TenantID
+}
+
+// FilterValue returns the value used for filtering.
+func (t Tenant) FilterValue() string {
+	if t.DisplayName != "" {
+		return t.DisplayName
+	}
+	if t.DefaultDomain != "" {
+		return t.DefaultDomain
+	}
+	return t.TenantID
+}
diff --git a/internal/tui/keys.go b/internal/tui/keys.go
new file mode 100644
index 0000000..c83dacc
--- /dev/null
+++ b/internal/tui/keys.go
@@ -0,0 +1,67 @@
+package tui
+
+import "github.com/charmbracelet/bubbles/key"
+
+// KeyMap defines the key bindings for the application.
+type KeyMap struct {
+	Up      key.Binding
+	Down    key.Binding
+	Select  key.Binding
+	Tab     key.Binding
+	Help    key.Binding
+	Quit    key.Binding
+	Refresh key.Binding
+	Back    key.Binding
+}
+
+// DefaultKeyMap returns the default key bindings.
+func DefaultKeyMap() KeyMap {
+	return KeyMap{
+		Up: key.NewBinding(
+			key.WithKeys("up", "k"),
+			key.WithHelp("↑/k", "up"),
+		),
+		Down: key.NewBinding(
+			key.WithKeys("down", "j"),
+			key.WithHelp("↓/j", "down"),
+		),
+		Select: key.NewBinding(
+			key.WithKeys("enter"),
+			key.WithHelp("enter", "select"),
+		),
+		Tab: key.NewBinding(
+			key.WithKeys("tab"),
+			key.WithHelp("tab", "switch view"),
+		),
+		Help: key.NewBinding(
+			key.WithKeys("?"),
+			key.WithHelp("?", "help"),
+		),
+		Quit: key.NewBinding(
+			key.WithKeys("q", "ctrl+c"),
+			key.WithHelp("q", "quit"),
+		),
+		Refresh: key.NewBinding(
+			key.WithKeys("r"),
+			key.WithHelp("r", "refresh"),
+		),
+		Back: key.NewBinding(
+			key.WithKeys("esc"),
+			key.WithHelp("esc", "back"),
+		),
+	}
+}
+
+// ShortHelp returns a short help text.
+func (k KeyMap) ShortHelp() []key.Binding {
+	return []key.Binding{k.Up, k.Down, k.Select, k.Tab, k.Quit}
+}
+
+// FullHelp returns the full help text.
+func (k KeyMap) FullHelp() [][]key.Binding {
+	return [][]key.Binding{
+		{k.Up, k.Down, k.Select},
+		{k.Tab, k.Refresh, k.Back},
+		{k.Help, k.Quit},
+	}
+}
diff --git a/internal/tui/model.go b/internal/tui/model.go
new file mode 100644
index 0000000..3069c32
--- /dev/null
+++ b/internal/tui/model.go
@@ -0,0 +1,477 @@
+package tui
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"strings"
+
+	"github.com/charmbracelet/bubbles/help"
+	"github.com/charmbracelet/bubbles/key"
+	"github.com/charmbracelet/bubbles/spinner"
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/l2D/azswitch/internal/azure"
+)
+
+// ViewType represents the current view.
+type ViewType int
+
+const (
+	ViewSubscriptions ViewType = iota
+	ViewDirectories
+)
+
+// State represents the application state.
+type State int
+
+const (
+	StateLoading State = iota
+	StateReady
+	StateError
+	StateSwitching
+	StateSuccess
+)
+
+// Model represents the TUI model.
+type Model struct {
+	// Azure client
+	client azure.Client
+
+	// Current state
+	state State
+
+	// Current view
+	view ViewType
+
+	// Data
+	account       *azure.Account
+	subscriptions []azure.Subscription
+	tenants       []azure.Tenant
+
+	// UI state
+	cursor       int
+	tenantCursor int
+	err          error
+	message      string
+
+	// Components
+	spinner spinner.Model
+	help    help.Model
+	keys    KeyMap
+
+	// Window size
+	width  int
+	height int
+
+	// Show help
+	showHelp bool
+
+	// Quit flag
+	quitting bool
+}
+
+// Messages
+type (
+	// errMsg is sent when an error occurs.
+	errMsg struct{ err error }
+
+	// dataLoadedMsg is sent when data is loaded.
+	dataLoadedMsg struct {
+		account       *azure.Account
+		subscriptions []azure.Subscription
+		tenants       []azure.Tenant
+	}
+
+	// switchedMsg is sent when a switch operation completes.
+	switchedMsg struct {
+		message string
+	}
+)
+
+// NewModel creates a new TUI model.
+func NewModel(client azure.Client) Model {
+	s := spinner.New()
+	s.Spinner = spinner.Dot
+	s.Style = SpinnerStyle
+
+	h := help.New()
+	h.ShowAll = false
+
+	return Model{
+		client:  client,
+		state:   StateLoading,
+		view:    ViewSubscriptions,
+		spinner: s,
+		help:    h,
+		keys:    DefaultKeyMap(),
+	}
+}
+
+// Init initializes the model.
+func (m Model) Init() tea.Cmd {
+	return tea.Batch(
+		m.spinner.Tick,
+		m.loadData(),
+	)
+}
+
+// loadData loads the Azure data.
+func (m Model) loadData() tea.Cmd {
+	return func() tea.Msg {
+		ctx := context.Background()
+
+		account, err := m.client.GetCurrentAccount(ctx)
+		if err != nil {
+			return errMsg{err}
+		}
+
+		subs, err := m.client.ListSubscriptions(ctx)
+		if err != nil {
+			return errMsg{err}
+		}
+
+		tenants, err := m.client.ListTenants(ctx)
+		if err != nil {
+			return errMsg{err}
+		}
+
+		return dataLoadedMsg{
+			account:       account,
+			subscriptions: subs,
+			tenants:       tenants,
+		}
+	}
+}
+
+// Update handles messages and updates the model.
+func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		return m.handleKeyMsg(msg)
+
+	case tea.WindowSizeMsg:
+		m.width = msg.Width
+		m.height = msg.Height
+		m.help.Width = msg.Width
+		return m, nil
+
+	case spinner.TickMsg:
+		var cmd tea.Cmd
+		m.spinner, cmd = m.spinner.Update(msg)
+		return m, cmd
+
+	case errMsg:
+		m.state = StateError
+		m.err = msg.err
+		return m, nil
+
+	case dataLoadedMsg:
+		m.state = StateReady
+		m.account = msg.account
+		m.subscriptions = msg.subscriptions
+		m.tenants = msg.tenants
+		// Set cursor to current subscription
+		for i := range m.subscriptions {
+			if m.subscriptions[i].IsDefault {
+				m.cursor = i
+				break
+			}
+		}
+		return m, nil
+
+	case switchedMsg:
+		m.state = StateSuccess
+		m.message = msg.message
+		return m, m.loadData()
+	}
+
+	return m, nil
+}
+
+// handleKeyMsg handles keyboard input.
+func (m Model) handleKeyMsg(msg tea.KeyMsg) (tea.Model, tea.Cmd) {
+	// Always allow quit
+	if msg.String() == "ctrl+c" {
+		m.quitting = true
+		return m, tea.Quit
+	}
+
+	// Don't handle keys while loading or switching
+	if m.state == StateLoading || m.state == StateSwitching {
+		return m, nil
+	}
+
+	switch {
+	case key.Matches(msg, m.keys.Quit):
+		m.quitting = true
+		return m, tea.Quit
+
+	case key.Matches(msg, m.keys.Help):
+		m.showHelp = !m.showHelp
+		m.help.ShowAll = m.showHelp
+		return m, nil
+
+	case key.Matches(msg, m.keys.Tab):
+		if m.view == ViewSubscriptions {
+			m.view = ViewDirectories
+		} else {
+			m.view = ViewSubscriptions
+		}
+		return m, nil
+
+	case key.Matches(msg, m.keys.Up):
+		if m.view == ViewSubscriptions {
+			if m.cursor > 0 {
+				m.cursor--
+			}
+		} else {
+			if m.tenantCursor > 0 {
+				m.tenantCursor--
+			}
+		}
+		return m, nil
+
+	case key.Matches(msg, m.keys.Down):
+		if m.view == ViewSubscriptions {
+			if m.cursor < len(m.subscriptions)-1 {
+				m.cursor++
+			}
+		} else {
+			if m.tenantCursor < len(m.tenants)-1 {
+				m.tenantCursor++
+			}
+		}
+		return m, nil
+
+	case key.Matches(msg, m.keys.Select):
+		return m.handleSelect()
+
+	case key.Matches(msg, m.keys.Refresh):
+		m.state = StateLoading
+		return m, tea.Batch(m.spinner.Tick, m.loadData())
+	}
+
+	return m, nil
+}
+
+// handleSelect handles the selection.
+func (m Model) handleSelect() (tea.Model, tea.Cmd) {
+	if m.view == ViewSubscriptions && len(m.subscriptions) > 0 {
+		sub := m.subscriptions[m.cursor]
+		if sub.IsDefault {
+			// Already selected
+			return m, nil
+		}
+		m.state = StateSwitching
+		return m, tea.Batch(
+			m.spinner.Tick,
+			m.switchSubscription(sub.ID),
+		)
+	} else if m.view == ViewDirectories && len(m.tenants) > 0 {
+		tenant := m.tenants[m.tenantCursor]
+		m.state = StateSwitching
+		return m, tea.Batch(
+			m.spinner.Tick,
+			m.switchTenant(tenant.TenantID),
+		)
+	}
+	return m, nil
+}
+
+// switchSubscription switches to the specified subscription.
+func (m Model) switchSubscription(id string) tea.Cmd {
+	return func() tea.Msg {
+		ctx := context.Background()
+		if err := m.client.SetSubscription(ctx, id); err != nil {
+			return errMsg{err}
+		}
+		return switchedMsg{message: "Subscription switched successfully"}
+	}
+}
+
+// switchTenant switches to the specified tenant using interactive login.
+func (m Model) switchTenant(id string) tea.Cmd {
+	cmd := exec.Command("az", "login", "--tenant", id)
+	return tea.ExecProcess(cmd, func(err error) tea.Msg {
+		if err != nil {
+			return errMsg{err}
+		}
+		return switchedMsg{message: "Directory switched successfully"}
+	})
+}
+
+// View renders the UI.
+func (m Model) View() string {
+	if m.quitting {
+		return ""
+	}
+
+	var s strings.Builder
+
+	// Header with current account
+	s.WriteString(m.renderHeader())
+	s.WriteString("\n")
+
+	// Main content
+	switch m.state {
+	case StateLoading:
+		s.WriteString(m.renderLoading())
+	case StateError:
+		s.WriteString(m.renderError())
+	case StateSwitching:
+		s.WriteString(m.renderSwitching())
+	default:
+		s.WriteString(m.renderTabs())
+		s.WriteString("\n")
+		if m.view == ViewSubscriptions {
+			s.WriteString(m.renderSubscriptions())
+		} else {
+			s.WriteString(m.renderDirectories())
+		}
+	}
+
+	// Help
+	s.WriteString("\n")
+	s.WriteString(HelpStyle.Render(m.help.View(m.keys)))
+
+	return s.String()
+}
+
+// renderHeader renders the header section.
+func (m Model) renderHeader() string {
+	if m.account == nil {
+		return TitleStyle.Render("Azure Account Switcher")
+	}
+
+	var content strings.Builder
+	content.WriteString(TitleStyle.Render("Azure Account Switcher"))
+	content.WriteString("\n")
+	content.WriteString(fmt.Sprintf("  %s %s\n", MutedStyle.Render("User:"), m.account.User.Name))
+	content.WriteString(fmt.Sprintf("  %s %s\n", MutedStyle.Render("Tenant:"), m.account.TenantDisplayName))
+	content.WriteString(fmt.Sprintf("  %s %s", MutedStyle.Render("Subscription:"), CurrentStyle.Render(m.account.Name)))
+
+	return HeaderBoxStyle.Render(content.String())
+}
+
+// renderTabs renders the tab bar.
+func (m Model) renderTabs() string {
+	subsTab := "Subscriptions"
+	dirsTab := "Directories"
+
+	if m.view == ViewSubscriptions {
+		subsTab = ActiveTabStyle.Render(subsTab)
+		dirsTab = InactiveTabStyle.Render(dirsTab)
+	} else {
+		subsTab = InactiveTabStyle.Render(subsTab)
+		dirsTab = ActiveTabStyle.Render(dirsTab)
+	}
+
+	return fmt.Sprintf("  %s  |  %s", subsTab, dirsTab)
+}
+
+// renderLoading renders the loading state.
+func (m Model) renderLoading() string {
+	return fmt.Sprintf("\n  %s Loading...", m.spinner.View())
+}
+
+// renderSwitching renders the switching state.
+func (m Model) renderSwitching() string {
+	return fmt.Sprintf("\n  %s Switching...", m.spinner.View())
+}
+
+// renderError renders the error state.
+func (m Model) renderError() string {
+	return fmt.Sprintf("\n  %s %s", ErrorStyle.Render("Error:"), m.err.Error())
+}
+
+// renderSubscriptions renders the subscriptions list.
+func (m Model) renderSubscriptions() string {
+	if len(m.subscriptions) == 0 {
+		return MutedStyle.Render("\n  No subscriptions found")
+	}
+
+	var s strings.Builder
+	s.WriteString("\n")
+
+	for i := range m.subscriptions {
+		sub := &m.subscriptions[i]
+		cursor := "  "
+		if i == m.cursor {
+			cursor = CursorStyle.Render("> ")
+		}
+
+		name := sub.Name
+		switch {
+		case sub.IsDefault:
+			name = CurrentStyle.Render(name + " ✓")
+		case i == m.cursor:
+			name = SelectedStyle.Render(name)
+		default:
+			name = NormalStyle.Render(name)
+		}
+
+		s.WriteString(fmt.Sprintf("%s%s\n", cursor, name))
+		s.WriteString(fmt.Sprintf("    %s\n", MutedStyle.Render(sub.ID)))
+	}
+
+	return s.String()
+}
+
+// renderDirectories renders the directories (tenants) list with their subscriptions.
+func (m Model) renderDirectories() string {
+	if len(m.tenants) == 0 {
+		return MutedStyle.Render("\n  No directories found")
+	}
+
+	// Group subscriptions by tenant ID
+	subsByTenant := make(map[string][]azure.Subscription)
+	for i := range m.subscriptions {
+		sub := &m.subscriptions[i]
+		subsByTenant[sub.TenantID] = append(subsByTenant[sub.TenantID], *sub)
+	}
+
+	var s strings.Builder
+	s.WriteString("\n")
+	s.WriteString(WarningStyle.Render("  ⚠ Switching directories will open browser for re-authentication"))
+	s.WriteString("\n\n")
+
+	for i := range m.tenants {
+		tenant := &m.tenants[i]
+		cursor := "  "
+		if i == m.tenantCursor {
+			cursor = CursorStyle.Render("> ")
+		}
+
+		name := tenant.Title()
+		isCurrent := m.account != nil && tenant.TenantID == m.account.TenantID
+
+		switch {
+		case isCurrent:
+			name = CurrentStyle.Render(name + " ✓")
+		case i == m.tenantCursor:
+			name = SelectedStyle.Render(name)
+		default:
+			name = NormalStyle.Render(name)
+		}
+
+		s.WriteString(fmt.Sprintf("%s%s\n", cursor, name))
+
+		// Show subscriptions for this directory
+		if subs, ok := subsByTenant[tenant.TenantID]; ok && len(subs) > 0 {
+			for j := range subs {
+				subName := subs[j].Name
+				if subs[j].IsDefault {
+					subName = CurrentStyle.Render("• " + subName)
+				} else {
+					subName = MutedStyle.Render("• " + subName)
+				}
+				s.WriteString(fmt.Sprintf("    %s\n", subName))
+			}
+		} else {
+			s.WriteString(fmt.Sprintf("    %s\n", MutedStyle.Render("(no subscriptions)")))
+		}
+	}
+
+	return s.String()
+}
diff --git a/internal/tui/model_test.go b/internal/tui/model_test.go
new file mode 100644
index 0000000..6e16f7d
--- /dev/null
+++ b/internal/tui/model_test.go
@@ -0,0 +1,254 @@
+package tui
+
+import (
+	"testing"
+
+	tea "github.com/charmbracelet/bubbletea"
+
+	"github.com/l2D/azswitch/internal/azure"
+)
+
+func TestNewModel(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+
+	if model.state != StateLoading {
+		t.Errorf("expected state to be StateLoading, got %v", model.state)
+	}
+
+	if model.view != ViewSubscriptions {
+		t.Errorf("expected view to be ViewSubscriptions, got %v", model.view)
+	}
+}
+
+func TestModel_Update_DataLoaded(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+
+	msg := dataLoadedMsg{
+		account: &azure.Account{
+			Name:              "Test Sub",
+			TenantDisplayName: "Test Tenant",
+			User:              azure.User{Name: "test@test.com"},
+		},
+		subscriptions: []azure.Subscription{
+			{Name: "Sub 1", ID: "id-1", IsDefault: false},
+			{Name: "Sub 2", ID: "id-2", IsDefault: true},
+		},
+		tenants: []azure.Tenant{
+			{DisplayName: "Tenant 1", TenantID: "tid-1"},
+		},
+	}
+
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.state != StateReady {
+		t.Errorf("expected state to be StateReady, got %v", m.state)
+	}
+
+	if m.account == nil {
+		t.Fatal("expected account to be set")
+	}
+
+	if len(m.subscriptions) != 2 {
+		t.Errorf("expected 2 subscriptions, got %d", len(m.subscriptions))
+	}
+
+	// Cursor should be on the default subscription (index 1)
+	if m.cursor != 1 {
+		t.Errorf("expected cursor to be 1 (default sub), got %d", m.cursor)
+	}
+}
+
+func TestModel_Update_KeyNavigation(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+
+	// Load data first
+	model.state = StateReady
+	model.subscriptions = []azure.Subscription{
+		{Name: "Sub 1", ID: "id-1"},
+		{Name: "Sub 2", ID: "id-2"},
+		{Name: "Sub 3", ID: "id-3"},
+	}
+	model.cursor = 0
+
+	// Test down navigation
+	msg := tea.KeyMsg{Type: tea.KeyDown}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.cursor != 1 {
+		t.Errorf("expected cursor to be 1 after down, got %d", m.cursor)
+	}
+
+	// Test up navigation
+	msg = tea.KeyMsg{Type: tea.KeyUp}
+	newModel, _ = m.Update(msg)
+	m = newModel.(Model)
+
+	if m.cursor != 0 {
+		t.Errorf("expected cursor to be 0 after up, got %d", m.cursor)
+	}
+}
+
+func TestModel_Update_TabSwitch(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.state = StateReady
+
+	if model.view != ViewSubscriptions {
+		t.Errorf("expected initial view to be ViewSubscriptions")
+	}
+
+	// Press tab
+	msg := tea.KeyMsg{Type: tea.KeyTab}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.view != ViewDirectories {
+		t.Errorf("expected view to be ViewDirectories after tab, got %v", m.view)
+	}
+
+	// Press tab again
+	newModel, _ = m.Update(msg)
+	m = newModel.(Model)
+
+	if m.view != ViewSubscriptions {
+		t.Errorf("expected view to be ViewSubscriptions after second tab, got %v", m.view)
+	}
+}
+
+func TestModel_Update_ErrorMsg(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+
+	msg := errMsg{err: azure.ErrNotLoggedIn}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.state != StateError {
+		t.Errorf("expected state to be StateError, got %v", m.state)
+	}
+
+	if m.err != azure.ErrNotLoggedIn {
+		t.Errorf("expected error to be ErrNotLoggedIn")
+	}
+}
+
+func TestModel_Update_WindowSize(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+
+	msg := tea.WindowSizeMsg{Width: 100, Height: 50}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.width != 100 {
+		t.Errorf("expected width to be 100, got %d", m.width)
+	}
+
+	if m.height != 50 {
+		t.Errorf("expected height to be 50, got %d", m.height)
+	}
+}
+
+func TestModel_View_Loading(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.state = StateLoading
+
+	view := model.View()
+
+	if view == "" {
+		t.Error("expected non-empty view")
+	}
+}
+
+func TestModel_View_Ready(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.state = StateReady
+	model.account = &azure.Account{
+		Name:              "Test Sub",
+		TenantDisplayName: "Test Tenant",
+		User:              azure.User{Name: "test@test.com"},
+	}
+	model.subscriptions = []azure.Subscription{
+		{Name: "Sub 1", ID: "id-1", IsDefault: true},
+	}
+
+	view := model.View()
+
+	if view == "" {
+		t.Error("expected non-empty view")
+	}
+}
+
+func TestModel_View_Quitting(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.quitting = true
+
+	view := model.View()
+
+	if view != "" {
+		t.Error("expected empty view when quitting")
+	}
+}
+
+func TestModel_CursorBounds(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.state = StateReady
+	model.subscriptions = []azure.Subscription{
+		{Name: "Sub 1", ID: "id-1"},
+	}
+	model.cursor = 0
+
+	// Try to go up when at top
+	msg := tea.KeyMsg{Type: tea.KeyUp}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if m.cursor != 0 {
+		t.Errorf("cursor should stay at 0, got %d", m.cursor)
+	}
+
+	// Try to go down when at bottom
+	msg = tea.KeyMsg{Type: tea.KeyDown}
+	newModel, _ = m.Update(msg)
+	m = newModel.(Model)
+
+	if m.cursor != 0 {
+		t.Errorf("cursor should stay at 0 (only 1 item), got %d", m.cursor)
+	}
+}
+
+func TestModel_HelpToggle(t *testing.T) {
+	client := azure.NewMockClient()
+	model := NewModel(client)
+	model.state = StateReady
+
+	if model.showHelp {
+		t.Error("expected showHelp to be false initially")
+	}
+
+	// Press ?
+	msg := tea.KeyMsg{Type: tea.KeyRunes, Runes: []rune{'?'}}
+	newModel, _ := model.Update(msg)
+	m := newModel.(Model)
+
+	if !m.showHelp {
+		t.Error("expected showHelp to be true after pressing ?")
+	}
+
+	// Press ? again
+	newModel, _ = m.Update(msg)
+	m = newModel.(Model)
+
+	if m.showHelp {
+		t.Error("expected showHelp to be false after pressing ? again")
+	}
+}
diff --git a/internal/tui/styles.go b/internal/tui/styles.go
new file mode 100644
index 0000000..0f2d4bf
--- /dev/null
+++ b/internal/tui/styles.go
@@ -0,0 +1,102 @@
+package tui
+
+import "github.com/charmbracelet/lipgloss"
+
+// Color palette.
+var (
+	primaryColor   = lipgloss.Color("39")  // Azure blue
+	secondaryColor = lipgloss.Color("208") // Orange
+	successColor   = lipgloss.Color("82")  // Green
+	errorColor     = lipgloss.Color("196") // Red
+	mutedColor     = lipgloss.Color("241") // Gray
+	highlightColor = lipgloss.Color("212") // Pink
+)
+
+// Styles for the TUI.
+var (
+	// Title style for headers.
+	TitleStyle = lipgloss.NewStyle().
+			Bold(true).
+			Foreground(primaryColor).
+			MarginBottom(1)
+
+	// Subtitle style.
+	SubtitleStyle = lipgloss.NewStyle().
+			Foreground(mutedColor).
+			MarginBottom(1)
+
+	// Selected item style.
+	SelectedStyle = lipgloss.NewStyle().
+			Foreground(highlightColor).
+			Bold(true)
+
+	// Current item indicator style.
+	CurrentStyle = lipgloss.NewStyle().
+			Foreground(successColor).
+			Bold(true)
+
+	// Normal item style.
+	NormalStyle = lipgloss.NewStyle().
+			Foreground(lipgloss.Color("252"))
+
+	// Muted style for secondary text.
+	MutedStyle = lipgloss.NewStyle().
+			Foreground(mutedColor)
+
+	// Error style.
+	ErrorStyle = lipgloss.NewStyle().
+			Foreground(errorColor).
+			Bold(true)
+
+	// Warning style.
+	WarningStyle = lipgloss.NewStyle().
+			Foreground(secondaryColor).
+			Italic(true)
+
+	// Success style.
+	SuccessStyle = lipgloss.NewStyle().
+			Foreground(successColor)
+
+	// Help style.
+	HelpStyle = lipgloss.NewStyle().
+			Foreground(mutedColor).
+			MarginTop(1)
+
+	// Box style for sections.
+	BoxStyle = lipgloss.NewStyle().
+			Border(lipgloss.RoundedBorder()).
+			BorderForeground(primaryColor).
+			Padding(0, 1)
+
+	// Header box style.
+	HeaderBoxStyle = lipgloss.NewStyle().
+			Border(lipgloss.RoundedBorder()).
+			BorderForeground(primaryColor).
+			Padding(0, 1).
+			MarginBottom(1)
+
+	// Cursor style.
+	CursorStyle = lipgloss.NewStyle().
+			Foreground(secondaryColor).
+			Bold(true)
+
+	// Tab style.
+	ActiveTabStyle = lipgloss.NewStyle().
+			Bold(true).
+			Foreground(primaryColor).
+			Underline(true)
+
+	// Inactive tab style.
+	InactiveTabStyle = lipgloss.NewStyle().
+				Foreground(mutedColor)
+
+	// Spinner style.
+	SpinnerStyle = lipgloss.NewStyle().
+			Foreground(secondaryColor)
+
+	// Status bar style.
+	StatusBarStyle = lipgloss.NewStyle().
+			Background(lipgloss.Color("235")).
+			Foreground(lipgloss.Color("252")).
+			Padding(0, 1)
+)
diff --git a/internal/version/version.go b/internal/version/version.go
new file mode 100644
index 0000000..9c7fba7
--- /dev/null
+++ b/internal/version/version.go
@@ -0,0 +1,28 @@
+// Package version provides build version information.
+package version
+
+import (
+	"fmt"
+	"runtime"
+)
+
+// Build information. Populated at build-time via ldflags.
+var (
+	Version   = "dev"
+	CommitSHA = "unknown"
+	BuildTime = "unknown"
+)
+
+// Info returns formatted version information.
+func Info() string {
+	return fmt.Sprintf("azswitch %s (%s) built %s with %s",
+		Version, CommitSHA, BuildTime, runtime.Version())
+}
+
+// Short returns a short version string.
+func Short() string {
+	if len(CommitSHA) > 7 {
+		return fmt.Sprintf("%s (%s)", Version, CommitSHA[:7])
+	}
+	return fmt.Sprintf("%s (%s)", Version, CommitSHA)
+}