Change Summary Hook

Runs when Claude finishes a task, providing TypeScript type checking and a summary of all changes made during the session.

What It Does

This Stop hook fires when Claude completes its work. It performs two functions:

1. TypeScript Type Checking (blocking) — If TypeScript files were modified, runs tsc --noEmit and blocks if there are type errors
2. Change Summary (informational) — Displays a summary of all files changed during the session

Behavior

TypeScript Checking

If any .ts or .tsx files were modified:

1. Locates tsconfig.json (checks git root, then src/, app/, packages/)
2. Runs npx tsc --noEmit to check types
3. Blocks Claude from stopping if type errors are found
4. Claude must fix the errors before finishing

This ensures you never end a session with broken TypeScript.

Go Linting

If any .go files were modified:

1. Runs golangci-lint on modified files
2. Reports issues but doesn't block (non-blocking)
3. Shows installation hint if golangci-lint isn't found

Change Summary

Always displays at the end:

═══════════════════════════════════════════════════════════════
                    SESSION CHANGE SUMMARY
═══════════════════════════════════════════════════════════════

📊 Overall Statistics:
───────────────────────────────────────────────────────────────
 3 files changed, 45 insertions(+), 12 deletions(-)

📁 Modified Files:
───────────────────────────────────────────────────────────────
M  src/auth/jwt.ts
A  src/middleware/auth.ts
M  src/routes/index.ts

🔍 Change Preview (per file):
───────────────────────────────────────────────────────────────

► src/auth/jwt.ts
  ─────────────────────────────────────────────────────────────
  +import { sign, verify } from 'jsonwebtoken';
  +
  +export function generateToken(payload: object) {
  ...

Prerequisites

# For TypeScript checking
npm install -g typescript
# Or have it as a project dependency

# For Go linting (optional)
go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest

Installation

Step 1: Copy the hook

cp change-summary.sh ~/.claude/hooks/change-summary.sh
chmod +x ~/.claude/hooks/change-summary.sh

Step 2: Configure in settings.json

Add to ~/.claude/settings.json:

{
  "hooks": {
    "Stop": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "$HOME/.claude/hooks/change-summary.sh"
          }
        ]
      }
    ]
  }
}

Why TypeScript Checking is Blocking

The auto-format hook doesn't run TypeScript checking because:

1. Type checking is slow compared to formatting
2. Running it after every edit would interrupt flow
3. Type errors often span multiple files

Instead, type checking runs once at the end. If there are errors, Claude is told to fix them before finishing. This ensures:

• Fast feedback during editing (formatting only)
• No broken TypeScript when the session ends
• Claude takes responsibility for type safety

Customization

Make TypeScript non-blocking

Change exit 1 to exit 0 in the TypeScript section:

if [[ $tsc_exit -ne 0 ]]; then
  # ... error output ...
  exit 0  # Changed from exit 1
fi

Add other language checks

Add sections for other languages before the change summary:

# Example: Python type checking with mypy
python_files_changed=$(git diff --name-only HEAD 2>/dev/null | grep -E '\\.py$' || true)
if [[ -n "$python_files_changed" ]]; then
  mypy $python_files_changed
fi

Customize change summary output

Modify the git commands in the summary section to show more or less detail.

Troubleshooting

TypeScript errors but I want to stop anyway

Use /stop to force stop, or temporarily modify the hook to be non-blocking.

tsconfig.json not found

The hook checks these locations:

• $git_root/tsconfig.json
• $git_root/src/tsconfig.json
• $git_root/app/tsconfig.json
• $git_root/packages/tsconfig.json

Add your location to the script if needed.

golangci-lint not found

Install it with:

go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest

Or remove the Go linting section if you don't need it.

Related Hooks

• auto-format — Formats files after each edit (complements this hook by handling formatting during the session)
• compaction — Improves context preservation when compacting