new-spec

name	new-spec
description	Use this skill when the user wants to start a new feature with a spec, or wants to write a spec for something they're about to build. Triggers on "new spec", "write a spec for X", "let's spec this out", "start a feature for…". Spec-driven development; the spec drives implementation. Do NOT use for cross-cutting proposals (use `new-rfc`) or recording decisions (use `new-adr`).

Skill: new-spec

Create a new feature spec under docs/specs/<feature>/ with both spec.md and plan.md.

When to invoke

The spec is the contract; the plan is the strategy. Even a one-day feature benefits from a one-paragraph spec — it forces the question "what does done look like?" before any code.

Procedure

1. Pick a kebab-case feature name from the user's description. Keep it short and noun-y: user-onboarding, webhook-retries, not improve-the-onboarding-experience.

2. Create the directory and copy this skill's bundled assets/spec.md and assets/plan.md into it as docs/specs/<feature>/spec.md and docs/specs/<feature>/plan.md. (Paths are skill-relative — the assets/ folder lives next to this SKILL.md wherever your installer placed the skill.)

3. Surface assumptions before writing any spec body — and run one targeted verification check per candidate first. With the directory scaffolded, stop. The load-bearing rule: one targeted check per candidate assumption — a repo read, a web lookup, or a read-only probe script — not a sweep. Then split the result into what you confirmed and what still needs the user.

   Draft candidates covering the three categories below, generated from this repo's actual context — the template serves multiple project types, so don't carry assumptions across features:

   • Technical — runtime, data model, persistence, deployment target, transport. Canonical sources: package manifests (pyproject.toml, package.json, Cargo.toml, go.mod, etc.), build / orchestration configs (docker-compose.yml, CI workflows), and the module the feature touches.
   • Product — who this serves and where the feature ends. No canonical local source; goes straight to Unverified. Don't fabricate confirmation.
   • Process — review cadence, who signs off on Boundaries (especially the Never do subsection), how the spec moves Draft → Approved. Canonical sources: docs/CHARTER.md, docs/CONVENTIONS.md, recent docs/specs/<feature>/spec.md for shape precedent, prior ADRs / RFCs that named the rule.

   See the Source of truth table in AGENTS.md for the full repo map. For assumptions about an external library, standard, service, or runtime behavior, the right source is a web search (cite the URL) or a read-only probe script (paste the command and its output) — e.g. python -c "import x; print(x.__version__)", a GET on a list endpoint, git --version. Probes must be side-effect-free against any external service: no writes, no mutations, no calls that bill or page. If the only way to verify is to write, the assumption stays Unverified. If web search isn't available in the harness, mark the assumption Unverified with (web search unavailable) — never guess a URL.

   Emit the result in chat (not into spec.md — the body is gated below), under this shape:

   ASSUMPTIONS I'M MAKING:
   
   ## Verified
   - <category>: <fact> (<single-line citation: path | URL | command + one-line summary>)
   - …
   
   ## Unverified
   - <category>: <open item or reason it couldn't be settled>
   - …
   

   Each Verified bullet stays single-line. If a probe's output is too long to summarise in one line, paste the full transcript in a fenced block above the ASSUMPTIONS I'M MAKING: heading and reference it from the bullet (e.g. (probe #1 above: returned True)).

   Example Verified entries: Technical: runtime is Python 3.12 (pyproject.toml), Technical: HTTP client is undici 6.x (package.json), Process: top-level convention changes need an RFC (docs/CONVENTIONS.md §Living-docs).

   Three to seven candidate assumptions before verification is the usual shape; Verified is whatever subset of those candidates passed the check — no floor, no separate cap. Coverage check is across the three categories (Technical / Product / Process), not the two subsections.

   Surface the Unverified list and wait for human confirmation or correction before writing into Objective, Boundaries, Testing Strategy, or Acceptance Criteria. If Unverified is empty, surface the Verified list with the highest-stakes item called out and ask the user to confirm that one specifically — a vague "looks good" doesn't count when the user may not have read the list.

   Only once Unverified has been signed off (or the highest-stakes Verified item confirmed, if Unverified was empty):

   • Copy the now-confirmed assumption list into the spec's ## Assumptions section as a flat list — one bullet per item, each citing how it was settled. Verified entries keep their canonical source (path / URL / probe summary); previously- Unverified entries cite user confirmation YYYY-MM-DD with today's date. The chat block was the working surface; the spec section is the audit trail.
   • Write the spec's Constrained by: header from any Verified items that name an ADR or RFC the feature must cite. The header lands before any body section; Verified items don't gate the Unverified loop but they do gate Constrained by:.
   • Stamp the optional Brief: header only when this spec is derived from a product brief — i.e. you arrived here from receive-brief, which decomposes a received brief into specs. Set it to the brief's slug (docs/product/briefs/<slug>.md); leave it blank or none for a spec authored directly. It records product provenance and is distinct from Constrained by: (governance). A spec without it stays valid — the field is additive.

4. Fill in the spec — including the Testing Strategy section. Push back hard on these failure modes:

   • Objective is vague. "It should be fast" is not an objective. "Returns within 200ms at p99 for payloads under 1KB" is. Every user-visible outcome named in the Objective must be precise enough that a test could be derived from it.
   • Testing Strategy left as the template's mode list. The template shows three modes (TDD, goal-based, manual QA); naming them without pairing each user-visible outcome from the Objective with a mode and a one-sentence why isn't a strategy.
   • Boundaries left empty. The three subsections — Always do, Ask first, Never do — keep an implementing agent inside the lines. Make the user name at least one entry per subsection, and at least one structural entry under Never do (no new top-level dependency, no new module boundary) so the diff can't sprawl into hypothetical futures.
   • No Acceptance Criteria. Without a checklist, "done" is opinion.
   • Body narrates history or the future. Write the spec in the present tense, as if the feature already exists and always worked this way — the retcon discipline. No "will be implemented", no "previously X, now Y", no deprecation timelines, no version-stamped history in the body. Mixed tenses make an agent reading the spec guess wrong about what is current; a present-tense body reads as a clean description of the contract as it stands. Decision history lives in ADRs and the changelog, not the spec body — the plan (plan.md) is the one exception, since it carries its own changelog of how the approach evolved.

   While writing Testing Strategy, sanity-check that each TDD-mode AC is concrete enough to stub — see work-loop's references/tdd-stubs.md. This is a self-check only: do not commit stubs at spec-authoring time — the stack and Contract: may not be settled yet, so committed stubs are generated later, in work-loop PLAN. An AC you can't imagine typing a test against is the signal to sharpen it now.

4b. Author the interface contract — only if this feature exposes an interface surface. This conditional step sits between the spec body and the plan, and is contract-type-agnostic — it handles any interface, not just REST APIs. If the feature exposes no interface surface, skip it: the spec→plan path runs unchanged.

• Detect & confirm the type. From the Objective's interface-facing Acceptance Criteria, auto-detect whether the feature exposes a contract surface and of which type — a synchronous REST API (openapi), an event interface (asyncapi), an RPC service (proto), a GraphQL schema (graphql), a standalone schema (jsonschema), … The type drives everything below. Confirm with the user — it's a judgment, not a flag.
• Locate or create the contract at its type's conventional path contracts/<type>/<domain>.<ext> (CONVENTIONS § 4 Contracts; references/contract-types.md maps every type to its location) — a new file for a new interface, the existing file when this spec modifies a known one. The location convention is the anchor: anyone finds contracts by globbing contracts/<type>/, no installed skill required, so any type (events included) lands in its canonical place.
• Author it. Look up the type's authoring skill in references/contract-types.md and check your available-skills roster (the same roster step 6 uses). If a skill is present (today: api-contract for openapi), invoke it to author/modify the contract against the active standard. If absent (today: every non-OpenAPI type, e.g. events), edit the file directly and note it was authored without rule-enforcement — a serviceable file for YAML-shaped types (AsyncAPI, JSON Schema), a stub + note for formats you can't reliably hand-author unaided (proto, GraphQL). A missing skill degrades enforcement, never the integration, and never blocks the spec.
• Link it (both ways). Fill the spec's - **Contract:** header with the contract file(s) this spec defines or touches, and add the backward pointer in the contract (an x-spec extension, or a contracts/REGISTRY.md row for extensionless formats) — CONVENTIONS § 4 Contracts.
• Point the plan at it. The plan's construction tests reference the contract as the artifact the implementation is verified against.

4c. Derive the spec's Shape: and the implementation stack — this primes the plan's ## Design (LLD). Between the spec body and the plan, settle two things so the design scaffolds at the right size and against the right stack:

• Shape. Pick the spec's Shape: — ui | service | data | integration | mixed — from the feature itself: a screen or flow is ui, a backend endpoint or worker is service, a schema/model change is data, a wiring of external systems is integration, anything spanning several is mixed. If you arrived here from receive-brief, the brief's framing usually decides it; otherwise ask the user. The shape selects which ## Design (LLD) sub-sections the plan scaffolds — a narrower shape keeps the plan thin. Stamp the resolved value on the spec's Shape: header.
• Stack. Determine the stack the ## Design (LLD) sub-sections will name:
  • When docs/architecture/reference.md is present, read it and conform the design to it — reference its named components, stereotypes, layers, and standards by name rather than inventing parallel ones. The reference architecture is the source of truth for the stack; the LLD is an instance of it.
  • When it is absent, degrade to detecting the established stack from the repo — lockfiles (package.json, pyproject.toml, go.mod, Cargo.toml, …), build / orchestration files, and the imports in the module the feature touches — plus any stack context a brief carried.
  • Elicit, don't invent. When detection is ambiguous or the repo is greenfield, ask which stack to target. Never guess a framework into the design — an invented stack is worse than one asked question.

The headings in ## Design (LLD) stay universal; the prose under them is the stack-specific instance you resolved here.

5. Fill in the plan second. The plan should:

   • Cite any ADRs or RFCs it follows from.
   • Break the work into tasks small enough to be a single PR each.
   • Carry construction tests per task — Tests: before Approach: in each task, designed up front. "We'll test it" is not a strategy.

   Push back hard on these plan-stage failure modes (mirror of step 4):

   • Task too big. "Implement the feature" is not a task; "add the validation function for X" is. Each task should fit a single PR and a single context window. Split coarse tasks until they do.
   • Depends on: omitted. Every task must state Depends on: explicitly — prior task IDs or none. Don't let authors lean on task order to imply dependency; that hides serial-by-default thinking and makes the plan unparseable.
   • Verification mode unstated. Every task must declare its mode — TDD, goal-based check, or visual / manual QA. Silent defaults produce mock-shape tests on config-shape tasks and untested invariants on logic-shape tasks.
   • Tasks without spec mapping. Each task should reference which behavior from the spec's Objective it implements, and the Testing Strategy mode for that behavior. Orphan tasks are scope creep in disguise; behaviors with no implementing task are gaps.
   • Specificity miss. Task descriptions should reference exact file paths and function or symbol names where they're known. "Update the parser" is too coarse to verify; "add a null-check in parser/lex.ts:Lexer.next" is the right level.

6. Spec-mode adversarial review. Before announcing the spec in the README, select a subagent matching adversarial-reviewer and ask it to review the freshly drafted spec.md + plan.md in spec mode — the role supports this explicitly. Iterate on findings until the reviewer returns Clean — ready to commit. Spec-mode reviews should converge in 1-2 passes; if you can't reach clean in 3, the spec has a structural problem — surface to a human rather than grinding. Absence of any subagent matching this role is a note in the final summary (adversarial-reviewer: no matching subagent installed; review skipped), not a blocker.

7. Update docs/specs/README.md to add the feature to the active list.

8. Keep the spec the single source of truth — drift is a bug. When implementation diverges from the spec, the spec is wrong: update it in the same PR. The failure mode this discipline prevents has a name — context poisoning: an agent loads a stale, duplicated, or self-contradicting doc and makes a confident, wrong decision from it, because nothing in the document tells it which part is current. Two habits are the defense, one for each way a doc poisons: one canonical home per fact (the Source of truth map in AGENTS.md) stops a fact from living in two places that can drift apart, and the present-tense retcon body (the failure mode in step 4) stops a single document from contradicting itself across tenses. Remind the user of both.

Anti-patterns to refuse

• Drafting a spec for something already half-built without checking against the existing code → ask the user to either align the spec with current behavior (and note any divergences) or write a new spec for what should change.
• Writing a spec that reads like a design doc (full of implementation) → the spec is the contract, not the design. Move implementation detail to plan.md.
• Skipping Boundaries → mandatory section. Each of the three subsections needs at least one entry.
• Writing into the spec body before the Unverified list has been confirmed → the headers can stay scaffolded; the bodies are the commitment and stay empty until the user has signed off on or revised the Unverified entries, even if the original prompt sounded definitive.
• Classifying a Technical or Process assumption as Unverified without recording the one check you attempted (path read, URL fetched, or read-only probe command + output) → attempt and cite the check. An attempted check that came back ambiguous is fine; a skipped check is not. The user's time is the scarce resource; burning a round-trip on a fact a single command would have answered is a tax on every spec.
• Fabricating a URL when web search isn't available → mark the assumption Unverified with (web search unavailable) and let the user supply the source. Plausible-looking citations the agent didn't actually fetch are worse than honest Unverified items.