SDD Lifecycle

Boundaries

Choose the mode covering the full authorized request; complete its stop point without pausing at intermediate modes. A still-applicable review-only, analysis-only, read-only, no-file-changes, “只分析”, or “不要改文件” request means zero writes.

Mode	Allowed work	Stop point
plan-only	Scope approved work; create a Plan only when phased/risky delivery needs one	Before implementation design/code
sdd-only	Write or review source-verified implementation design	Before runtime edits
implement-approved-spec	Create justified prerequisites, implement, test, review, fix, and validate	Validated implementation; no closeout/commit
full-lifecycle	Delivery plus explicitly requested closeout	Contracts reconciled and process artifacts disposed

“Plan and implement” is implement-approved-spec; it never implies closeout, archive, or commit. If target resolution remains ambiguous after explicit ID/slug, current-conversation package, and the only Active Package, ask one target question and perform zero writes.

Read Set

Read AGENTS.md, the owning Product Spec or Governance Contract, the matching Tracker, and nearby architecture/code/tests. Read North Star for product work. Read Plan/SDD only when they exist or the change justifies creating them. Treat Archive as historical evidence, not approval.

Artifacts

• Use exactly one authority lane: Product Decision/Spec for product behavior; Governance Contract for repo-only docs/checker/CI/release/Agent rules.
• Baseline Active Package: README.md + tracker.md.
• Add plan.md for phased delivery, material dependencies, risk, rollback, or cross-session execution.
• Add sdd.md for multi-module design, shared infrastructure, behavior/data/ privacy/lifecycle changes, compatibility, migration, or non-trivial UI state.
• Tracker is the only execution status and validation log. Active Registry and Feature Home contain links, not status mirrors.
• Enforce 1 Now + 1 Next: at most one Implementing | Validating | Blocked package plus one Planned package. At Validated, continue already-authorized closeout; ask once only if closeout authority is missing.
• Tracker Current Snapshot is the cross-session handoff. Never create standalone handoff*.md or closeout.md in an Active Package.
• Follow docs/development/documentation-workflow.md for exact lifecycle and retention rules; do not duplicate its templates inside this skill.

Plan And Design

Before implementation:

1. Verify approved product scope or explicit governance authority from current contracts and the conversation; do not ask again for an already-made choice.
2. Search the actual dependency surface with rg.
3. Create/update Feature Home and Tracker; register the Feature Home.
4. Create a Plan only when its delivery/risk content would not fit concisely in Tracker.
5. Create an SDD only when the design criteria above apply. Verify every named method, type, setting, command, locale key, and CSS class against source.
6. Record compatibility, rollback, and a requirement-to-test mapping where relevant. Close or explicitly defer P0/P1/P2 design findings.

Missing Plan/SDD in implement-approved-spec is not a separate user approval gate: create only what the implementation genuinely requires. Stop if product scope or risk acceptance is unresolved.

Implement And Validate

For each behavior slice:

implement -> focused validation -> review -> fix -> verify

Keep the Tracker current and use existing module boundaries. Before a slice, map its REQ/AC or risk to the change, minimum sufficient evidence, pass condition, and rerun/expansion trigger. Follow Validation Planning And Reuse and Test Failure Diagnosis in AGENTS.md; add tests for uncovered behavior or regression risk, and select the correct source/tooling/artifact group. Satisfy the Local Validation Gate at the justified scope, reusing covered checks only with verified inputs/results. Use PA review/follow-up skills for implementation review; fix-driven verification covers the affected risk.

Retain required broad and app/device gates at each phase exit. For app proof, use make deploy or the eligible current-build reuse target under AGENTS.md Local Deployment, then observe the affected behavior. Do not claim app or iOS validation without observed evidence; docs/skills-only work uses the docs gate.

Closeout

Enter only in full-lifecycle or after explicit close/archive intent.

1. Reconcile actual behavior, current Product/Architecture/Governance contract, Tracker, and release state.
2. Record final checks, residual risk, and artifact disposition in Tracker; move unresolved work to Backlog.
3. Absorb durable outcomes into current contracts/tests.
4. Delete Feature Home, Tracker, Plan, SDD, handoff, and round-by-round logs after absorption unless one contains unique evidence.
5. Retain only a compact closeout or evidence document when a current authority needs the historical rationale. Place it in docs/archive/<year>/ and link it from that authority; do not preserve a complete package by default.
6. Update the link-only Active Registry and run docs validation.

If a selected archive path exists, fail closed before mutating source state; do not overwrite, merge, auto-suffix, or partially move it.

Git Boundary And Output

Do not stage, commit, push, tag, publish, or release without explicit authority. For a requested local commit, inspect status and focused diffs, stage only the intended files, use a signed-off Conventional Commit, and add no Co-Authored-By trailer.

Report the selected mode, artifacts justified or omitted, validation performed, open decisions, residual risk, and the exact stop point.