How to Generate Conventional Commit Messages Automatically

What You'll Build

A git hook or CI step that reads your staged diff and returns a properly formatted conventional commit message — scoped, typed, and ready to commit.

Prerequisites

Option A — Git Prepare-Commit-Msg Hook

#!/bin/sh
# .git/hooks/prepare-commit-msg

DIFF=$(git diff --cached | head -c 6000)
if [ -z "$DIFF" ]; then exit 0; fi

RESPONSE=$(curl -sS -X POST https://www.runcept.com/api/v1/run \
  -H "Authorization: Bearer $RUNCEPT_API_KEY" \
  -H "Content-Type: application/json" \
  -d "{\"agent\": \"commit-messages\", \"input\": {\"diff\": \"$(echo "$DIFF" | head -c 4000 | python3 -c "import sys,json; print(json.dumps(sys.stdin.read()))" | tr -d '"')\"}}")

JOB_ID=$(echo $RESPONSE | jq -r '.job_id')

for i in {1..15}; do
  sleep 3
  RESULT=$(curl -sS https://www.runcept.com/api/v1/jobs/$JOB_ID \
    -H "Authorization: Bearer $RUNCEPT_API_KEY")
  if [ "$(echo $RESULT | jq -r '.status')" = "complete" ]; then
    MSG=$(echo $RESULT | jq -r '.output.message')
    echo "$MSG" > "$1"
    break
  fi
done

Make it executable: chmod +x .git/hooks/prepare-commit-msg

Option B — Node.js Script

import { execSync } from 'child_process'

const diff = execSync('git diff --cached').toString().slice(0, 6000)

const { job_id } = await fetch('https://www.runcept.com/api/v1/run', {
  method: 'POST',
  headers: {
    Authorization: Bearer ${process.env.RUNCEPT_API_KEY},
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ agent: 'commit-messages', input: { diff } }),
}).then(r => r.json())

// Poll
while (true) {
  await new Promise(r => setTimeout(r, 3000))
  const job = await fetch(https://www.runcept.com/api/v1/jobs/${job_id}, {
    headers: { Authorization: Bearer ${process.env.RUNCEPT_API_KEY} },
  }).then(r => r.json())
  if (job.status === 'complete') {
    console.log(job.output.message)
    // e.g. "feat(auth): add OAuth2 PKCE flow"
    break
  }
}

Output Format

The agent returns conventional commit format:

{
  "message": "feat(api): add rate limiting per API key tier",
  "type": "feat",
  "scope": "api",
  "breaking": false,
  "body": "Adds per-key rate limiting using Redis sliding window..."
}

Next Steps

Use this agent on Runcept

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