Claude Code Hooks (Go Implementation)

Claude Code hooks implemented in Go for better performance, zero runtime dependencies, and native integration with the Nix ecosystem.

Migrated from TypeScript/Bun implementation in dots/.claude/hooks/.

Hooks Included

1. claude-hooks-initialize-session

Event: SessionStart

What it does:

• Detects and skips subagent sessions
• Sets terminal tab title to “Claude Ready”
• Logs session start to ~/.config/claude/history/sessions/YYYY-MM/YYYY-MM-DD_session-log.txt
• Implements debouncing to prevent duplicate triggers (2 second window)

2. claude-hooks-capture-tool-output

Event: PostToolUse

What it does:

• Captures outputs from interesting tools (Bash, Edit, Write, Read, Task, NotebookEdit, Skill, SlashCommand)
• Logs to JSONL files: ~/.config/claude/history/tool-outputs/YYYY-MM/YYYY-MM-DD_tool-outputs.jsonl
• Silent failure - doesn’t disrupt workflow if logging fails
• Automatically creates directory structure

3. claude-hooks-validate-docs

Event: Manual/Pre-commit

What it does:

• Scans all markdown files for internal links
• Checks if linked files exist
• Reports broken links with file:line numbers
• Exit code 0 if valid, 1 if broken links found
• Skips external URLs, anchors, and mailto links

4. claude-hooks-save-session

Event: SessionEnd

What it does:

• Prompts user to save session summary when ending a Claude Code session
• Skips subagent sessions (silent)
• Displays a message asking if session should be saved
• Works with /save-session slash command for creating session entries
• Saves to ~/.config/claude/history/sessions/YYYY-MM/YYYY-MM-DD-HHMMSS_SESSION_description.md

5. claude-hooks-validate-git-push

Event: PreToolUse (via extensions)

What it does:

• Validates git commands to prevent dangerous operations
• Blocks git add -A, git add --all, and git add . to prevent adding unintended files
• Blocks git push commands without explicit refspecs (e.g., git push origin main)
• Warns about pushes to protected branches (main/master)
• Exit code 0 if command is safe, non-zero if command should be blocked

Architecture

tools/claude-hooks/
├── cmd/
│   ├── capture-tool-output/main.go   # PostToolUse hook
│   ├── initialize-session/main.go    # SessionStart hook
│   ├── save-session/main.go          # SessionEnd hook
│   └── validate-docs/main.go         # Documentation validator
├── internal/
│   └── paths/paths.go                # Shared path utilities
├── default.nix                       # Nix package definition
├── go.mod                            # Go module definition
├── go.sum                            # Go dependencies
├── setup-hooks.sh                    # Configuration script
└── README.md                         # This file

Installation

Via Nix (Recommended)

1. Build the package:

   nix build .#claude-hooks
   

2. Install to your profile:

   nix profile install .#claude-hooks
   

3. Or add to home-manager (in home/common/dev/default.nix or similar):

   home.packages = with pkgs; [
     claude-hooks
   ];
   

4. Configure hooks (run setup script):

   ./tools/claude-hooks/setup-hooks.sh
   

   Or manually update ~/.claude/settings.json:

   {
     "hooks": {
       "SessionStart": [
         {
           "hooks": [
             {
               "type": "command",
               "command": "claude-hooks-initialize-session"
             }
           ]
         }
       ],
       "PostToolUse": [
         {
           "hooks": [
             {
               "type": "command",
               "command": "claude-hooks-capture-tool-output"
             }
           ]
         }
       ],
       "SessionEnd": [
         {
           "hooks": [
             {
               "type": "command",
               "command": "claude-hooks-save-session"
             }
           ]
         }
       ]
     }
   }
   

5. Enable the session-manager plugin (for /save-session command):

   # Symlink the plugin if not already linked
   ln -s ~/src/home/dots/.claude/plugins/session-manager ~/.claude/plugins/session-manager
   

Manual Build (without Nix)

cd tools/claude-hooks

# Build all hooks
go build -o bin/claude-hooks-capture-tool-output ./cmd/capture-tool-output
go build -o bin/claude-hooks-initialize-session ./cmd/initialize-session
go build -o bin/claude-hooks-save-session ./cmd/save-session
go build -o bin/claude-hooks-validate-docs ./cmd/validate-docs

# Copy to PATH
sudo cp bin/* /usr/local/bin/

# Then run setup script
./setup-hooks.sh

Development

Running hooks directly with go run

cd tools/claude-hooks

# Test initialize-session
go run ./cmd/initialize-session

# Test capture-tool-output (requires JSON input)
echo '{"tool_name":"Bash","tool_input":{},"tool_response":{},"conversation_id":"test"}' | \
  go run ./cmd/capture-tool-output

# Test validate-docs
go run ./cmd/validate-docs

Testing

# Run all tests
go test ./...

# Test with verbose output
go test -v ./internal/paths

# Test specific package
go test ./cmd/validate-docs

Updating vendorHash

If you add/update Go dependencies:

cd tools/claude-hooks
go mod tidy
nix build .#claude-hooks 2>&1 | grep "got:" | awk '{print $2}'
# Copy the hash to default.nix vendorHash field

Advantages over TypeScript/Bun

1. Zero runtime dependencies - Compiled to native binary, no Bun required
2. Faster execution - Native code vs interpreted JavaScript
3. Easier distribution - Single binary per hook
4. Cross-compilation - Build for any architecture from any platform
5. Nix integration - Proper package management and reproducible builds
6. Type safety - Compile-time checks without runtime overhead
7. Standard library - Excellent built-in support for JSON, file I/O, paths

Migration Notes

The Go implementation is functionally equivalent to the TypeScript version with these improvements:

• Performance: Faster startup and execution
• Reliability: Compile-time type checking
• Portability: Works on all systems where Go binaries run
• Integration: Native Nix packaging for declarative installation

The old TypeScript hooks in dots/.claude/hooks/ can be removed after verifying the Go versions work correctly.

Troubleshooting

Hook not running:

• Check ~/.claude/settings.json syntax
• Verify binaries are in PATH: which claude-hooks-initialize-session
• Check stderr output in terminal
• Verify hooks are executable: ls -la $(which claude-hooks-initialize-session)

Permission errors:

• Ensure directories exist: mkdir -p ~/.config/claude/history/{sessions,tool-outputs}
• Check write permissions on ~/.config/claude/history

Debugging:

• Hooks write errors to stderr - check terminal output
• Run hooks manually to test: claude-hooks-initialize-session
• Check log files: ls -la ~/.config/claude/history/

Build errors:

• Run go mod tidy to update dependencies
• Check Go version: go version (requires Go 1.23+)
• Verify vendorHash in default.nix is correct

Environment Variables

• CLAUDE_DIR - Override default ~/.config/claude directory (optional)
• CLAUDE_PROJECT_DIR - Set by Claude Code (used for subagent detection)
• CLAUDE_AGENT_TYPE - Set by Claude Code for subagents (used for detection)

License

Same as the rest of the home repository.