If you don't block it locally, you can't block it in CI. Connect Gemini CLI to your local Git hooks to prevent bad code from ever reaching the server.
1. What is a Hook?
Git hooks are scripts that automatically execute when specific Git events occur, such as a commit or push. By connecting Gemini CLI's Headless mode here, the AI acts as your "pair programmer," reviewing code right before a commit.
2. Setting Up a Pre-commit Hook
The most useful is the pre-commit hook, which runs the moment a user types git commit.
Create a .git/hooks/pre-commit file in your project (ensure it's executable: chmod +x), and write the following script:
#!/bin/bash
# Get the list of staged files
STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACM)
if [ -z "$STAGED_FILES" ]; then
exit 0
fi
echo "🤖 Gemini CLI is inspecting staged files..."
# Request inspection from Gemini (Headless mode)
# GEMINI_API_KEY must be set in the environment
REVIEW_OUTPUT=$(gemini --headless "@$STAGED_FILES Check this code for security vulnerabilities, exposed API keys, or debugging code like console.log. If there is a problem, answer only 'FAIL', otherwise answer 'PASS'.")
if [[ "$REVIEW_OUTPUT" == *"FAIL"* ]]; then
echo "❌ Gemini found an issue in the code. Commit aborted."
echo "Detailed review:"
# You can ask for details again, or prompt the user to enter interactive mode.
gemini --headless "@$STAGED_FILES Point out exactly the security vulnerabilities or debugging code you found earlier."
exit 1
else
echo "✅ Gemini inspection passed. Proceeding with commit."
exit 0
fi3. Practical Hook Pattern: Auto-generating Commit Messages
Hooks can also be used to reduce busywork. Use the prepare-commit-msg hook to auto-generate a commit message summarizing the staged changes.
#!/bin/bash
# .git/hooks/prepare-commit-msg
COMMIT_MSG_FILE=$1
# Summarize changes
DIFF=$(git diff --cached)
echo "🤖 Gemini CLI is proposing a commit message..."
# Enforce Conventional Commits format
SUGGESTED_MSG=$(gemini --headless "Read the following changes and write a 1-line commit message in Conventional Commits format (feat/fix/docs/refactor, etc). Changes: $DIFF")
# Insert the suggested message at the top of the existing file
echo "$SUGGESTED_MSG" > tmp_msg
cat $COMMIT_MSG_FILE >> tmp_msg
mv tmp_msg $COMMIT_MSG_FILE4. Cautions When Applying Hooks
- Ensure Execution Speed: If local hooks take too long (e.g., over 30 seconds), developers will experience fatigue. Keep prompts in hooks as narrow and specific as possible (e.g., "Only find console logs").
- Token Costs: API calls happen on every commit. Consider your team's token usage policy. It's even better if you can heavily utilize token caching.
- Share the Bypass Method: Sometimes you need to ignore the AI's misjudgment and force a commit. Let your teammates know about the
--no-verifyflag (git commit --no-verify).
Next to Read
- Extending to the CI/CD environment: Gemini GitHub Actions
- Distributing this hook across the organization: Gemini Extensions & MCP