Phase 0 — how each step is built

Each step of Phase 0 goes through the same loop, each part run by a separate agent:

1. Spec (Opus, senior engineer): writes docs/phase-0/step-N-<name>.md — the detailed task list, acceptance criteria and test plan for the step.
2. Build (Sonnet, developer): implements exactly that spec, with tests.
3. Review (Opus, senior engineer): reviews the implementation against the spec and writes docs/phase-0/reviews/step-N-review-R.md with a verdict (APPROVED or CHANGES REQUESTED) and numbered findings.
4. Fix (Sonnet, a fresh developer): addresses every finding; then back to 3 until approved.
5. The step is committed, then the next step starts.

Source documents: MVP spec, development plan.

Constraints for every step

• Everything must build and test offline on a laptop: no real GitHub App, no Claude API key, no internet. GitHub is reached through Octokit and is mocked in tests (recorded/fixture webhook payloads, nock or an injected client). The Claude API is behind an interface with a deterministic fake for tests.
• Postgres runs from docker compose (OrbStack is available). Tests that need a database use that container or a throwaway schema; pure logic is unit-tested without it.
• Things only a human can do (registering the real GitHub App, creating API keys, recruiting pilots, labeling real PRs) are written down in docs/phase-0/HUMAN-TODO.md, never faked.
• Graft stores no source code: diffs may be read in memory and sent to the model, never persisted.
• Package manager: pnpm. Node 24. TypeScript strict mode.