What /code-review Does That the GitHub App Doesn't: Effort Levels, --fix, and REVIEW.md

/code-review runs a background bug-hunting subagent that doesn't consume your session context — tune effort, auto-apply fixes, and give it a project-specific mandate with REVIEW.md.

Claude Code's /code-review command is distinct from the GitHub App-based Code Review service. It runs locally as a forked background subagent — the findings arrive in your conversation when the review completes, without filling your context window with intermediate reasoning.

Effort controls confidence vs. coverage

low and medium report only high-confidence findings, so you see fewer false positives but narrower coverage. high through max broaden coverage but include findings the review is less certain about. Claude remembers the last level you typed explicitly, so always pass one in scripts:

/code-review high          # background review, report findings
/code-review high --fix    # same, plus auto-apply findings to working tree

Caveat: --fix edits land outside your session checkpoints. /rewind won't undo them — use git if you want to inspect before applying.

REVIEW.md gives the review a project mandate

A REVIEW.md file at your repo root is injected at highest priority into every agent in the pipeline — higher than your CLAUDE.md. Use it to define what "Important" means in your codebase, which paths to skip, and what checks to always run:

## What Important means here
Reserve 🔴 for bugs that break behavior or leak data.
Style and naming are Nit at most.

## Always check
- New API routes have an integration test
- Log lines exclude email addresses and user IDs

## Skip
- Generated code under src/gen/
- Any *.lock file

Keep REVIEW.md focused: a long file dilutes the rules that matter most.

For cloud-level review

/code-review ultra (Team/Enterprise) escalates to a multi-agent swarm on Anthropic infrastructure, with findings posted inline to your PR via --post. From CI scripts: claude -p '/code-review ultra' launches the review non-interactively.

Sources: Claude Code Review — code.claude.com · REVIEW.md reference — code.claude.com · Ultrareview — code.claude.com