Best for
- Turning a written spec into working code without scope creep
- Codebases with established patterns worth respecting
- Teams that want diffs small enough to actually review
What you give it
- One change, specified: what it does and what done means
- The codebase, and any rules it must respect
What you get back
- The change implemented in your project's own style
- Tests that prove the specified behaviour, run and passing
- A short report: files touched, decisions taken, anything left open
How it works
- Reads the spec, then the surrounding code, before writing anything.
- Finds the project's existing pattern for this kind of work and extends it.
- Implements the smallest change that fully satisfies the spec.
- Writes or updates tests for the specified behaviour and runs them.
- Reports what changed and surfaces every judgement call it had to make.
Example
You: Spec: an account holder can export their invoices as one PDF per year. Done means: button on the invoices page, a generated file per calendar year, covered by a test.
Result: Three files changed and one added, reusing the existing PDF helper and button styles; two tests added and green; report notes the empty-year case and how it chose to handle it (shown, not silently decided).
Limits — please read
- No spec, no build — it will ask for one rather than guess.
- It improves what it touches, not everything it sees; refactors need their own ask.
- Unfamiliar stacks slow it down; it reads docs rather than bluffing.