Run a Claude Code review in CI with one claude -p line

#claudecode #ai #productivity #devops

Most people only use Claude Code interactively. But the same CLI has a headless mode: claude -p "<prompt>" runs one prompt, prints the answer, and exits. That makes it a normal script step you can drop into CI or a git hook.

The one line

git diff origin/main...HEAD | claude -p "Review this diff. List real bugs only. If there are none, print exactly: LGTM" --output-format text

Piped stdin becomes context, -p runs non-interactively, and the output is plain text you can grep.

Make it fail the build

#!/usr/bin/env bash
set -euo pipefail
out=$(git diff origin/main...HEAD | claude -p \
  "Review this diff for bugs, missing error handling and leaked secrets. If nothing is wrong, reply with exactly LGTM." \
  --allowedTools "Read,Grep" --max-turns 3)
echo "$out"
[[ "$out" == "LGTM" ]] || exit 1

--allowedTools "Read,Grep" keeps the CI run read-only: it can look at files but not edit or run shell commands.
--max-turns 3 caps how long it can wander.
Need structured results? Use --output-format json and parse .result with jq.

GitHub Actions step

- name: Claude review
  env:
    ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
  run: |
    npm i -g @anthropic-ai/claude-code
    ./scripts/claude-review.sh

Keep the key in repository secrets, never in the script.

Tips

Keep the prompt strict ("bugs only", "exactly LGTM") so the output is easy to check.
Your project CLAUDE.md and .claude/settings.json still load in headless mode, so your house rules apply in CI too.
Start as a non-blocking job (continue-on-error: true) for a week before you let it fail builds.

Want the rest of the setup?

I keep copy-ready Claude Code configs (CLAUDE.md templates, slash commands, hooks, permission rules) in Vildanden Agent Config. There's a free sample: https://justly-mia-429.rehost.page/

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