Scope a new build phase with testable acceptance criteria

Turn a vague "next thing to build" into a phase-gated chunk of work — not a vision document.

What to build next: {{short description}}
Current project state: {{what exists, what's wired up, what's stubbed}}
Constraints: {{time, dependencies, what must not break}}

Produce:

1. **Phase name** — verb-led, scoped, no marketing language.
2. **Entry conditions** — what must already be true before this phase can start. Be specific. Flag fuzzy dependencies.
3. **In scope / Out of scope** — two lists. Out of scope is mandatory and should include things that might be assumed in.
4. **Acceptance criteria** — 4–8 testable assertions. Each verifiable by running something, reading an output, or pointing at a file. No "feels right" criteria.
5. **Exit gate checklist** — what to check before declaring the phase done and moving on.
6. **Risks** — top 3, with the cheapest signal that would tell you each one is materializing.

Before writing, list any assumptions made about the project that weren't stated. If any are load-bearing, ask before proceeding.