design

Design a change — create a change container (if needed) and generate spec artifacts.

<decision_boundary>

Use for:

• Creating a new Beat change and generating spec artifacts (proposal, gherkin, design.md)
• Resuming artifact generation for an existing change that has pending spec artifacts
• Choosing which spec artifacts to include (presets: Full, Standard, Minimal, Technical, Custom)

NOT for:

• Breaking down tasks or creating execution plans (use /beat:plan)
• Exploring ideas or thinking through a problem before committing (use /beat:explore)
• Implementing code (use /beat:apply)
• Reviewing or verifying implementation (use /beat:verify)

Trigger examples:

• "Design a user authentication feature" / "Create a change for login" / "Generate specs for X"
• Should NOT trigger: "break down the tasks" / "let me think about this" / "implement the change"

</decision_boundary>

Before writing any artifact files: you MUST invoke superpowers:using-git-worktrees. When the artifact selection includes proposal or design, you MUST invoke superpowers:brainstorming before generating content. This applies even when scope seems obvious.

Before writing gherkin scenarios: you MUST run the four-challenge CONTEXT.md check (see step 4 below) and ensure every project-specific term used in scenarios is defined in beat/CONTEXT.md. Create the glossary lazily — only when the first term is added.

After writing each artifact: you MUST run the four-check spec self-review (placeholder / consistency / scope / ambiguity). Fix issues inline.

While writing design.md: you MUST run the three-condition ADR gate (hard-to-reverse + surprising + real trade-off — see references/adr-format.md) on each Key Decision. When all three hold, offer to lift the decision into a new ADR under docs/adr/. The user may decline.

Invoke in order: worktrees first (isolate), then brainstorming (design).

If a prerequisite skill is unavailable (not installed), continue with fallback — but NEVER skip because you judged it unnecessary.

Prerequisites (invoke before proceeding)

Skill	When	Priority
superpowers:using-git-worktrees	Before first file write	MUST
superpowers:brainstorming	Before creating proposal or design	MUST
mattpocock-skills:grill-with-docs	When CONTEXT.md ambiguity is complex enough that a full grilling session is warranted	OPTIONAL

If a prerequisite skill is unavailable (skill not installed), skip and continue. For optional skills (grill-with-docs), offer to invoke when applicable; if the user declines or it isn't installed, proceed with the four-challenge check inline.

Rationalization Prevention

Thought	Reality
"I don't need a worktree for just writing specs"	Without a worktree, artifacts live in the main workspace and won't carry into apply. Isolate from the start.
"brainstorming isn't needed, the user already described what they want"	A description is not a design. brainstorming surfaces assumptions, alternatives, and edge cases.
"The user wants speed, invoking superpowers will slow us down"	Skipping prerequisites produces lower-quality artifacts that cause rework during apply and verify.
"This change is simple enough to skip brainstorming"	Simple changes finish brainstorming quickly. Complex changes need it most. There is no middle ground where skipping helps.
"The domain terms are obvious, no need to update CONTEXT.md"	Obvious to you, not to future-you or anyone else reading the feature in six months. Glossary entries are two lines. Add them inline.
"Spec self-review is overkill, the artifact is short"	Self-review catches placeholders, contradictions, and ambiguities that compound through plan and apply. The four checks take 30 seconds.
"This decision is just for this change, no ADR needed"	Run the three-condition gate. If it's hard-to-reverse, surprising, and a real trade-off, future changes will trip over it — that's the ADR's job. Decisions that are change-specific don't pass the gate; let the gate decide, not your gut.
"We'll lift this into an ADR later"	"Later" rarely arrives. The decision is fresh now; the ADR is 1-3 sentences. Write it inline.

Red Flags — STOP if you catch yourself:

• Writing any file before invoking using-git-worktrees
• Generating proposal sections without having invoked brainstorming
• Creating design.md without invoking brainstorming first
• Writing gherkin scenarios that contain internal method names, numeric thresholds, or implementation constants
• Writing gherkin scenarios that use project-specific domain terms not defined in beat/CONTEXT.md
• Modifying an existing feature in beat/features/ without creating a .orig backup first
• Writing tasks.md or - [ ] checkboxes — tasks belong in /beat:plan
• Skipping the spec self-review because the artifact "looks fine"
• Writing a Key Decision in design.md that meets all three ADR conditions without offering an ADR
• Thinking "this prerequisite isn't needed for this particular change"

Process Flow

digraph design {
    "Select or create change" [shape=box];
    "Invoke using-git-worktrees" [shape=box, style=bold];
    "Ask artifact preset" [shape=box];
    "Includes proposal?" [shape=diamond];
    "Invoke brainstorming" [shape=box, style=bold];
    "Create proposal" [shape=box];
    "Self-review proposal" [shape=box, style=bold];
    "Includes gherkin?" [shape=diamond];
    "CONTEXT.md\nfour-challenge check" [shape=box, style=bold];
    "Existing scenarios\nto modify?" [shape=diamond];
    "Backup .orig +\ncopy to changes/" [shape=box];
    "Create gherkin\n(new features only)" [shape=box];
    "Self-review gherkin" [shape=box, style=bold];
    "Includes design?" [shape=diamond];
    "Create design" [shape=box];
    "ADR gate\n(per Key Decision)" [shape=box, style=bold];
    "Self-review design" [shape=box, style=bold];
    "Commit artifacts" [shape=box];
    "Show summary" [shape=doublecircle];

    "Select or create change" -> "Invoke using-git-worktrees";
    "Invoke using-git-worktrees" -> "Ask artifact preset";
    "Ask artifact preset" -> "Includes proposal?";
    "Includes proposal?" -> "Invoke brainstorming" [label="yes"];
    "Includes proposal?" -> "Includes gherkin?" [label="no"];
    "Invoke brainstorming" -> "Create proposal";
    "Create proposal" -> "Self-review proposal";
    "Self-review proposal" -> "Includes gherkin?";
    "Includes gherkin?" -> "CONTEXT.md\nfour-challenge check" [label="yes"];
    "Includes gherkin?" -> "Includes design?" [label="no"];
    "CONTEXT.md\nfour-challenge check" -> "Existing scenarios\nto modify?";
    "Existing scenarios\nto modify?" -> "Backup .orig +\ncopy to changes/" [label="yes"];
    "Existing scenarios\nto modify?" -> "Create gherkin\n(new features only)" [label="no"];
    "Backup .orig +\ncopy to changes/" -> "Create gherkin\n(new features only)";
    "Create gherkin\n(new features only)" -> "Self-review gherkin";
    "Self-review gherkin" -> "Includes design?";
    "Includes design?" -> "Invoke brainstorming" [label="yes, only if\nnot yet invoked"];
    "Includes design?" -> "Commit artifacts" [label="no"];
    "Invoke brainstorming" -> "Create design" [label="for design"];
    "Create design" -> "ADR gate\n(per Key Decision)" [style=bold];
    "ADR gate\n(per Key Decision)" -> "Self-review design";
    "Self-review design" -> "Commit artifacts";
    "Commit artifacts" -> "Show summary";
}

Input: Change name (kebab-case) OR a description of what to build. Can also be an existing change name to fast-forward remaining artifacts.

Steps

1. If no clear input provided, ask what they want to build

   Use AskUserQuestion tool to ask what they want to build. Derive kebab-case name from description.

2. Create or select change

   Determine the change name. Before creating any files, invoke using-git-worktrees to isolate this change.

   • If beat/changes/<name>/ doesn't exist: create it (directory + status.yaml + features/.gitkeep)
   • If it exists: use it, read status.yaml (schema: references/status-schema.md) to find remaining artifacts

3. Ask which spec artifacts to include

   Read status.yaml. For artifacts still pending, ask user once upfront:

   Use AskUserQuestion tool:

   "Which spec artifacts do you want? (Tasks are handled separately by /beat:plan)"

   1. Full: Proposal + Gherkin + Design (recommended for large features)
   2. Standard: Proposal + Gherkin (recommended for medium features)
   3. Minimal: Gherkin only (recommended for small bug fixes)
   4. Technical: Proposal only, no Gherkin (for tooling/infra/refactor changes with no behavior change)
   5. Custom: Let me choose each one

   Mark skipped artifacts as skipped in status.yaml. Tasks are always set to pending — task breakdown happens in /beat:plan. Update phase to match the latest completed spec artifact after each creation.

4. Create artifacts in pipeline order

   Read beat/config.yaml if it exists (schema: references/config-schema.md). Use language for artifact output language, inject context, and apply matching rules per artifact type throughout creation.

   For each artifact to create (pipeline order: proposal -> gherkin -> design):

   • Read all completed artifacts for context
   • Invoke prerequisites per the table above (brainstorming before proposal/design — invoke once before the first artifact that needs it; skip for subsequent artifacts if already invoked)
   • Gherkin only — before writing scenarios: run the CONTEXT.md four-challenge check (see sub-step below)
   • Create the artifact following the patterns below
   • After writing: run the spec self-review (see sub-step below); fix issues inline
   • Update status.yaml
   • Show brief progress: "Created "
   • If context is critically unclear, pause and ask

   CONTEXT.md four-challenge check (before writing gherkin):

   Read beat/CONTEXT.md if it exists (schema: references/context-format.md). Create it lazily when the first term is added — never preemptively.

   Walk through the brainstorming output and any draft scenario text. For each project-specific term, run these checks and update beat/CONTEXT.md inline as findings emerge (never batch):

   1. Against the glossary — the term conflicts with an existing entry? Call it out, resolve, update.
   2. Sharpen fuzzy — the term is vague or overloaded (e.g. "account" meaning Customer and User both)? Pick the canonical word, list the others as _Avoid_.
   3. Stress-test — invent edge-case scenarios that probe term boundaries; force the boundary to be named.
   4. Cross-reference code — the user states behaviour that the code contradicts? Surface, decide source of truth, update the loser.

   Optional grilling: If mattpocock-skills:grill-with-docs is installed and the ambiguity is complex enough to warrant a full grilling session, offer to invoke it once: "Want to drop into grill-with-docs for a deeper pass on this?" If the user declines, or the skill isn't installed, continue inline with the four challenges. Beat never hard-requires grill-with-docs.

   Every project-specific term used in scenarios MUST exist in beat/CONTEXT.md before the scenario is written. Bolded terms in scenarios are the canonical form.

   Spec self-review (after writing each artifact):

   Re-read the artifact with fresh eyes and check:

   1. Placeholder scan — any TBD, TODO, incomplete sections, vague requirements?
   2. Internal consistency — do sections contradict each other? Does the design match the gherkin scenarios?
   3. Scope check — is this focused enough for a single implementation plan, or does it need decomposition?
   4. Ambiguity check — could any requirement be read two different ways? If so, pick one and make it explicit.

   Fix issues inline. No need to re-review the fix — just fix and move on.

   Artifact patterns:

   • Proposal: Sections: ## Why, ## What Changes, ## Impact

   • Gherkin:

     • Read references/feature-writing.md for conventions on description blocks, scenario organization, and review checklist
     • Before writing, scan beat/features/**/*.feature and beat/changes/*/features/*.feature (excluding current change) — read Feature: and Scenario: lines to map existing coverage, deep-read only overlapping features, avoid duplication and align style
     • SpecFlow style, tags @happy-path/@error-handling/@edge-case
     • Feature description carries PRD essence (must include: As a / I want / So that)
     • Every scenario MUST have a testing layer tag: @e2e (user journeys needing a running app) or @behavior (business logic testable without a full app; default @behavior)
     • Write at behavior level — describe what the system does ("Monthly billing adjusts for short months"), not how a function works ("calculateNextTransactionDate clamps to last day")
     • Use business language — no concrete numeric thresholds, code method names, or internal constants (API contract constants are OK as shared vocabulary)
     • Repeated Given steps use Background:
     • Tags must serve a filtering purpose — no decorative tags
     • BDD focuses on high-level acceptance; boundary values and algorithm details belong in unit tests
     • If option 4 (Technical) was chosen, skip gherkin entirely

     Modifying existing features (see references/testing-conventions.md for full mechanism):

     When the scan reveals scenarios in beat/features/ that need modification:

     1. Conflict check: scan beat/features/**/*.feature.orig — if a .orig exists for the same file, another change is modifying it. Warn and stop.
     2. Backup: rename the original in beat/features/ to .feature.orig (hides it from BDD runners)
     3. Copy: copy the original content to beat/changes/<name>/features/<file>.feature
     4. Modify: edit the scenario(s) in the changes/ copy (add/change/remove steps, add new scenarios)
     5. Record: add the original path to status.yaml gherkin.modified array

     New features that don't modify existing scenarios go directly to changes/<name>/features/ as before.

   • Design:

     • Sections: ## Approach, ## Key Decisions, ## Components
     • ADR gate — for each Key Decision, run the three-condition check from references/adr-format.md:
       1. Hard to reverse? (cost of changing your mind is meaningful)
       2. Surprising without context? (future reader will wonder "why on earth this way?")
       3. Result of a real trade-off? (genuine alternatives existed) If all three hold, use AskUserQuestion tool: "This decision meets the ADR gate. Lift it into docs/adr/?" On Yes, write a 1-3 sentence ADR using the template in references/adr-format.md, increment the highest existing number in docs/adr/ by one, and add a cross-reference from design.md (See docs/adr/NNNN-slug.md). On No, continue. Create docs/adr/ lazily — only on first ADR.
     • Architecture hub suggestion (Layer 3, advisory) — if design.md describes a module-level architecture change (new module, module split/merge, changed module boundaries or responsibilities), suggest updating beat/ARCHITECTURE.md — the hub diagram, modules table, or constraints (see references/architecture-format.md). Create the hub lazily, only if the project is multi-module and the user accepts. Never block.

5. Commit artifacts and show final status

   Commit all change artifacts: git add beat/changes/<name>/ && git commit

   Use a descriptive message, e.g. "design(): add spec artifacts".

   Update phase to the latest completed spec artifact in status.yaml.

   ## Design Complete: <change-name>
   
   Created:
   - proposal.md (or skipped)
   - features/*.feature (or skipped if Technical option)
   - design.md (or skipped)
   
   Tasks: pending (run `/beat:plan` to create execution plan)
   
   Spec artifacts ready! Review them, then run `/beat:plan` for task breakdown.
   

Guardrails

• Gherkin is mandatory by default -- only skip for purely technical changes (option 4: Technical)
• Ask upfront which artifacts to include (don't ask per artifact)
• If change already exists with some artifacts done, only create remaining
• If context is critically unclear, ask -- but prefer reasonable defaults to keep momentum
• Verify each artifact file exists after writing before proceeding
• Tasks are NOT created in this skill — they are handled by /beat:plan