build-one git:20260727.5a2073aA

Immutable. This exact content is served forever at /api/v1/blob/49d8c50559af3185.

---
name: build-one
description: Implement exactly one planned slice after scope is frozen, without exceeding the spec ceiling or carrying known analysis debt into the build.
---

# Build One

## Purpose

Implement exactly one planned slice without expanding the behavioral contract or building through a known stale/required analysis checkpoint.

## When to use

Use after a task is selected and scope is frozen.

## Inputs

- `SPEC.md`
- `PLAN.md`
- `TODO.md`
- Scope boundary
- Current repo status
- Analysis checkpoint when present in `HANDOFF.md` or other current state

## Workflow

1. Read `SPEC.md`, `PLAN.md`, and `TODO.md`.
2. Select one task.
3. Confirm the scope boundary.
4. Perform the cheap `analyze-mini` eligibility check using artifacts already loaded for this build:
   - `REQUIRED` or `STALE` checkpoint -> invoke `analyze-mini` before editing.
   - `FRESH` checkpoint -> confirm its task-defining inputs still match current state; if not, mark it `STALE` and invoke `analyze-mini`.
   - missing checkpoint or `NOT_NEEDED` -> invoke `analyze-mini` only when a current trigger exists.
   - **Missing prior analysis alone does not require `analyze-mini`.**
   - Do not broaden discovery merely to prove that analysis is unnecessary.
5. If full analysis returns `BLOCKED`, stop before implementation and resolve the contradiction or decision.
6. Confirm the spec ceiling: each intended behavior change must satisfy an acceptance criterion or be necessary support for one. Explicit non-goals remain out of scope.
7. If the implementation needs behavior outside that ceiling, stop and renegotiate or update the spec before making that expansion.
8. Make the minimum useful change.
9. Run relevant verification.
10. Update `VERIFY.md` or `HANDOFF.md` with a compact build note:
    - Selected slice
    - Files touched
    - Why each file was touched
    - Compatibility seams preserved
    - Analysis checkpoint: `FRESH | NOT_NEEDED`
    - Spec ceiling respected: yes/no
    - Unexpected behavior added: none | describe
    - Tests changed: yes/no
    - Verification run
    - Stop reason
11. Update task status.
12. Stop after one task.
13. Summarize changed files and result.

## Outputs

- One implemented slice
- Changed file summary
- Verification result
- Build note
- Updated `TODO.md` if appropriate

## Stop conditions

- The selected task is complete and verified.
- The task needs a scope or spec change.
- Analysis is `REQUIRED`, `STALE`, or `BLOCKED` and must be resolved before editing.
- Verification fails and diagnosis is needed.
- A useful adjacent improvement is discovered but is not required by the current acceptance criteria.

## Anti-patterns

- Running `analyze-mini` before every build as a ritual.
- Treating absence of an analysis checkpoint as a blocker by itself.
- Continuing into the next task without approval.
- Refactoring unrelated code.
- Adding "helpful" behavior beyond the acceptance criteria because it is nearby or easy.
- Treating partial infrastructure as a completed slice.