Plan Feature — Scaffold (internal)

Turn a designed feature into the project's complete planning artifact set, ready for phase-by-phase execution. Fills only the SPEC's engineering half — the product half (goal, context, scope, capability closure) already exists and is marked designed before this skill ever runs (plan-feature's redirect gate guarantees it). Docs only — never code.

When to use

• The plan-feature router calls this once a feature's product half is designed — from design-feature, plan-feature-from-issue, or an already-scoped slug/SPEC — to fill the engineering half of its docs/features/<NN>-<slug>/SPEC.md and the rest of the folder, then update the roadmap.

Not for product definition (that is design-feature) or writing code (that is execute-phase) or deciding whether to build (that is the plan-feature router / triage-issue).

Step 0 — Discover the project (always first)

Per the agent guide's Workflow conventions + documentation map, then read what THIS skill needs: the feature SPEC template, the roadmap (numbering/order/deps), 1–2 recent feature folders to mirror the artifact set, and the architecture/domain docs the map points to. No template/roadmap → fall back to the agent guide and state the assumption.

Progressive loading — scaffold only after discovery

The reference allowlist is exactly one path. After Step 0, read and execute the complete scaffold process. It owns the product- half gate, artifact scaling, roadmap transition, re-read, and fixed completion report. The phase contract owns the 8-box phase-lint and the normalized phase fingerprint.

The resource is normative and one hop from this file. Missing resource → stop; never reconstruct phase or close-out wording from memory.

The verification contract owns the ACCEPTANCE.md schema, validation ladder, and anti-weakening rules. Consume it after the engineering plan is complete and before registering planned.

Research and reference trace (plan stage)

• Conditional web research. Plan-stage research runs only when a bounded question (ROWS.md Q1–Q5) cannot be answered from repository evidence: run exactly one web pass before the phases are emitted and freeze what it returns as evidence rows (URL and access date). A question the repository answers is never re-fetched.
• Mandatory reference trace. Affected code is located by symbol/reference search — LSP/serena when the environment offers it, grep otherwise — and the blast radius is derived from that search, never from model memory: added or changed code can break callers the plan must name.

Guardrails

• Docs only. No source edits, migrations, or dependencies.
• Respect the architecture: honor layer rules (inner layers don't import outer) and any domain/i18n/SEO/a11y rules from the docs map.
• Architectural invariants. The planning preflight owns the normalized repository state read and the ONE final architectural classification for the whole plan; consume it here. Its absence is compatible: record n/a: no project invariants declared in the engineering half. For every applicable rule, record its ID, repository evidence, and preserves | violates | introduces | changes classification in ### Architecture impact. Only preserves may produce phases; the other classifications stop for an explicit architectural decision through the project's declared authority — and only after the full plan exists, never converted into a phase task or inferred from the product half.
• Surface conflicts (numbering clashes, dependency cycles, scope overlap) before writing, not after.
• Otherwise honor the project's Workflow conventions (branch/PR, docs-language).

Relationship to other skills

Invoked by the plan-feature router (after design-feature / plan-feature-from-issue designed the product half, or directly for an already-designed scoped slug/SPEC). Hands off to execute-phase for P1; audit-docs audits anytime.

Done when

• docs/features/<NN>-<slug>/ exists with the SPEC's engineering half + ACCEPTANCE.md + every scaled planning artifact filled — the product half untouched from what design-feature / plan-feature-from-issue wrote.
• The roadmap lists the feature with correct number, order, dependencies, and status planned (the defined → planned write this skill owns) — re-read and confirmed after the write, not assumed from having run it.
• No code changed; open questions captured in decisions.md.