Plan feature scaffold

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.

Process

1. Verify the product half is designed. The SPEC's ## Design status must read designed and Capability closure must be filled — plan-feature's redirect gate already checked this before calling this skill, but confirm before writing: an undesigned SPEC here is a caller bug, not something to silently patch over.

2. Resolve identity. From the roadmap, confirm the number and kebab-case slug the product half already used (or, for an already-scoped SPEC with no prior roadmap entry, pick the next free number). Record dependencies (features that must land first) and note ordering conflicts.

3. Fill the engineering half of the SPEC. In the existing docs/features/<NN>-<slug>/SPEC.md, complete every Engineering-half section — technical goals, architecture impact, design, decisions to confirm, branch name (feat/<NN>-<slug> or per project convention), phases, testing requirements, and dev scenarios (happy path and failure modes: empty/degraded state, races, outages — plus how to reproduce each locally). Never touch the Product half (goal, context, scope, capability closure, ## Design status) — that is design-feature's content; if it looks wrong or incomplete, stop and redirect rather than editing it here. No unfilled placeholders; record genuinely-unknown values as open questions in decisions.md, not blanks.

4. Scale the artifacts to the size.

   • XS/S → the SPEC is the only planning artifact (skip the set below — don't generate ceremony the feature doesn't need), but its ### Phases section must list ≥ 2 phases with checkbox tasks: P1 implementation (cut by the per-phase cheap-executability checklist below), final phase P2 — Hardening & PR carrying the literal close-out tasks (fixed wording — copy them from docs/fix/_TEMPLATE/SPEC.md ## Phases, never paraphrase). Register the roadmap entry and hand off to execute-phase <NN> (it runs one phase per invocation, ticking the SPEC's ### Phases checkboxes as its ledger).
   • Split — mandatory, not advisory. Before emitting the phase list for an M/L feature, split this feature into Depends on:-chained features if any holds: (a) the plan would exceed ~5 phases; (b) a phase touches more than one layer/concern; (c) a phase requires a design decision not resolved in SPEC.md/decisions.md. Use the existing dependency infrastructure (transitive dependency gate + workflow-status build order) — never invent a new mechanism. More, smaller, slower features is the accepted trade; a phase a weak model cannot execute without judgement is not well-cut.
   • Per-phase cheap-executability checklist. Each phase you emit passes only if: ✓ every task is independently checkable without judgement; ✓ zero open design decisions (all resolved in SPEC.md/ decisions.md); ✓ one layer/concern; ✓ its verification gate runs locally. A phase failing any box is re-cut or split (feeds the split rule above). State n/a: <reason> only where a box is genuinely inapplicable.
   • Phase-lint (mandatory, emit-time). Before emitting the phase list, run the canonical 8-box phase-lint (docs/fix/_TEMPLATE/SPEC.md ## Phases "Phase-lint" — the authoritative copy, also quoted in docs/features/_TEMPLATE/SPEC.md ### Phases) against every phase. Any FAIL → re-cut or split the phase using the mandatory-split rule above before emitting; never emit a phase with an unticked lint box.
   • Spec-lint (mandatory, emit-time). After filling the engineering half, run the SPEC template's ### Spec-lint — all boxes: the engineering boxes plus the product boxes as a regression check (design-feature already passed them; a FAIL here means the product half regressed or the scaffold left placeholders). Presence checks only — mechanical, no quality judgement. Any FAIL → fix before the completion report; never report over a failed box.
   • M/L → generate the full set, mirroring the recent features':
     • PLAN.md — phased plan labelled P1, P2, … and called phases; phases are an implementation sequence, not a delivery boundary. Naming is fixed: always P1, P2, … / "phases" — never S1/S2 or "Steps". The label is the executor's argument (execute-phase NN P2), so every artifact (PLAN.md, TASKS.md, progress.md) must use the same P1, P2, … labels. The last implementation phase is always a hardening phase: edge cases and the SPEC's dev-scenario failure modes (empty/degraded states, races, outages), implemented and tested — not just documented.
     • TASKS.md — per-phase checklists the executor ticks off. The final phase's checklist always ends with these literal close-out tasks: "[ ] open the PR (gh pr create --body-file <path> — body written as a Markdown file, real backticks, never inline --body/heredoc that leaves \-escaped backticks) and PRINT THE PR URL in the chat", "[ ] update the roadmap row to done · [#<pr>](<pr-url>)", "[ ] commit docs: link PR #<n> and push" — so the close-out is a ticked task, not an assumed behavior. Emit each command-checkable acceptance criterion as the command (a grep, a test invocation, a build) — not as prose; only genuinely judgement-only criteria stay prose, labelled read-verified (feature 07's testing.md is the reference shape). A weak executor verifies by running the command, not by judging prose.
     • progress.md — the phase handoff record, one entry per phase in execute-phase's fixed schema (## P<k> — <date> — <sha> + Done / Remains / Gotchas / Files / Next lines — see Phase handoff record in skills/execute-phase/SKILL.md). Create it with just the header line Last reviewed: —; execute-phase appends the entries.
     • testing.md — what is tested at which layer (prefer integration); same command-checkable-as-command rule as TASKS.md above.
     • known-issues.md — deferred items, each linked to (or destined for) an issue. Do not plan to implement deferred work inline.
     • decisions.md — architecture/scope decisions + open questions.
     • architecture-notes.md — layer impact, ports, schema, bindings touched.

5. Register in the roadmap with number, ordering, dependencies, and set the row's status to planned — the defined → planned transition this skill owns (see the roadmap's Status legend). The row must already read defined on entry (step 1 confirmed the product half is designed); if the row is missing entirely (an already-scoped SPEC with no prior roadmap entry), add it directly at planned since the SPEC + artifacts this step produces satisfy that state in the same edit. Verify the write before moving on: re-read the roadmap row and confirm it literally reads planned. If it doesn't (a dropped write), re-apply the edit and re-read again — never end this step, or the turn, with the write unverified.

6. Do not branch or code. That belongs to execute-phase; record the branch name in the SPEC only.

7. Hand off — return exactly (fixed completion report):

   SCAFFOLD <NN>-<slug> — size: <XS|S|M|L>
   Artifacts written: <SPEC.md [+ PLAN.md TASKS.md progress.md testing.md
     known-issues.md decisions.md architecture-notes.md for M/L]>
   Roadmap: registered as <NN> (deps: <list|none>)   Phases: <n> (P1…P<n>, last = <hardening (M/L) | Hardening & PR (XS/S)>)
   Spec-lint: PASS (<n>/<n> boxes)   Phase-lint: PASS (all phases)
   Open questions: <n> (in decisions.md) | none
   

   The caller (plan-feature) prints the closing → Next: block.

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.
• 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 + every 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.