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.md or the active scope boundary
• Current repo status and frozen Git base
• 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. When SCOPE.md and scripts/scope_gate.py exist, run the scope gate against the frozen base before the first new implementation write. Existing FAIL or unresolved REVIEW_REQUIRED state blocks further edits.
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.

1. If full analysis returns BLOCKED, stop before implementation and resolve the contradiction or decision.
2. 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.
3. If the implementation needs behavior outside that ceiling, stop and renegotiate or update the spec before making that expansion.
4. If SPEC.md has an ENFORCED implementation diff budget, treat it as an early warning boundary while building. Do not knowingly grow past the declared file/added-line limits without surfacing the expansion; do not edit the budget after the fact merely to fit the patch.
5. Make the minimum useful change.
6. Run relevant verification.
7. Run the scope gate before declaring the slice complete when SCOPE.md and the helper exist:

    python scripts/scope_gate.py --base <frozen-base>

A scope-gate FAIL blocks completion and requires a revert or pre-write scope renegotiation. REVIEW_REQUIRED must be surfaced and resolved; it is not permission to continue silently.

1. 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
• Scope gate: PASS | FAIL | REVIEW_REQUIRED
• Diff budget: PASS | REVIEW_REQUIRED | NOT_APPLICABLE
• Spec ceiling respected: yes/no
• Unexpected behavior added: none | describe
• Tests changed: yes/no
• Verification run
• Stop reason

1. Update task status.
2. Stop after one task.
3. Summarize changed files and result.

Outputs

• One implemented slice
• Changed file summary
• Verification result
• Scope-gate result when a persisted scope contract exists
• Build note
• Updated TODO.md if appropriate

Stop conditions

• The selected task is complete, verified, and inside the frozen write boundary.
• The task needs a scope or spec change.
• Scope gate returns FAIL or unresolved REVIEW_REQUIRED.
• The implementation exceeds an enforced diff budget and the expansion has not been reviewed.
• 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.
• Changing SCOPE.md after an out-of-scope edit to make the final diff look compliant.
• Continuing after a scope-gate failure because the changed code appears useful.
• Continuing into the next task without approval.
• Refactoring unrelated code.
• Adding "helpful" behavior beyond the acceptance criteria because it is nearby or easy.
• Enlarging a declared diff budget after implementation grows instead of reviewing the expansion.
• Treating partial infrastructure as a completed slice.