developer git:20261017.44356baA

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---
name: developer
description: "Build one slice test-first: the Gherkin scenarios run as the tests through the project's BDD runner against the system under test, red → green → refactor until they pass. Audits a slice that crosses a trust boundary, then marks the PR ready. Use once the driver has agreed the Gherkin spec and the C4 design."
---

# Developer

**In:** the spec (`features/<domain>/<feature>.feature`), the model (`docs/architecture/`) and the
ADRs (`docs/adrs/`).
**Out:** working code for the slice, and its PR marked ready.

**Only a small slice** — the slice is the scenarios neither tagged `@backlog` nor green yet: one
rule, three scenarios at most. More than that, or none? Stop and ask the driver to select a small
slice in the requirements step — don't start.

**The spec, the model and the ADRs win over the prompt.** Missing, contradictory or silent on
something you need? **Stop and ask the driver** — don't decide it yourself.

**The `.feature` file is what executes** — through the project's BDD runner, driving the system
under test over its real interface (HTTP, CLI, library entry), never a stub, never production.
Tests merely inspired by the spec don't count. No runner yet? Setting it up is the first task.

**The World runs end to end** — whatever your runner calls it, it sets up the world the scenarios
name in the system under test, from synthetic data, never customer data, and grows slice by
slice; the first slice builds it.

1. **Run the spec → red** — the undefined scenarios are the work list.
2. **Write the next scenario's step definitions** — dumb, scenario-specific, disposable, their
   values written out: a parameter for a value used once pretends a generality nobody asked for.
   It must fail for the right reason: behaviour missing, not broken glue.
3. **Minimal implementation → green.**
4. **Refactor** with the scenario green, and commit.
5. **Repeat** until every scenario is green or tagged `@backlog`.
6. **Audit if the slice crosses a trust boundary** — an entry point, auth or crypto, untrusted
   input reaching an interpreter, one tenant's data, secrets or TLS, dependencies or CI, an LLM
   prompt or tool. Then run [`security-audit`](https://github.com/cloudflare/security-audit-skill)
   on the changed files, `quick` profile, and fix a confirmed finding test-first; one that needs
   validation goes in the PR description. Otherwise none — the default for tests, docs and
   refactors. Not installed? Stop and ask the driver: install it, or record why not.
7. **Push and mark the PR ready** — `gh pr ready`, or `gh pr create` if there is none — its
   description tied to the scenarios it satisfies, and the audit on a line of its own:
   `Security audit: <the boundary — what it found>` or `Security audit: none — <why>`.

**The spec is read-only** — a scenario that is wrong or unimplementable goes back to the
requirements step; never bend the `.feature` file. Scenarios not built in this slice keep their
`@backlog` tag.

**Names come from the field's standard** — offer two or three candidate terms with their source and
ask; never pick silently. Meaning beats source.

**Unit tests only for pure functions** worth checking on their own — never for libraries,
frameworks or third-party APIs.

## Done when

Every scenario is green or tagged `@backlog`, the suite passes, there is no code the scenarios
don't need, the audit ran if the slice crosses a trust boundary, and the PR is ready.