Define

/define -- Project Definition (Gates 0, WB, 1)

Single-session skill that produces codebase assessment (Gate 0), optional Working Backwards document (Gate WB), and an approved PRD (Gate 1). All three gates run as one continuous conversation -- the user does not leave between gates.

Rules

• Read fresh every time. Read progress.txt from disk on every invocation -- never rely on conversation memory or cached values (STATE-03).
• Single continuous session. Gates 0, WB, and 1 run in one conversation. The user does not leave between gates (DEF-14).
• Produce-then-review at every gate. Produce the full artifact, present it, offer Approve / Revise. Rejection = revision request (D-06, D-08).
• All checklist items must be resolved. Every review checklist item must be [x] or [-] (N/A with reason) before recording gate approval (DEF-06, D-07).
• Write-ordering contract. When writing to state files, follow STATE-04 ordering. For /define, only progress.txt is modified (gate entries).
• Interactive prompts. Use AskUserQuestion for all user-facing choices (2-4 options, max 12-character headers).
• No auto-dispatch. Tell the user what to run next after completion. Never auto-invoke another skill.

Prerequisites

• Working directory is the project root (where progress.txt lives or will be created by /project).
• progress.txt must exist. If it does not, instruct the user to run /project first to bootstrap project state.
• Gate 0 must not already be approved (unless this is a revision mode invocation).

Step 1 -- Detect Mode and State

Read progress.txt from the project root. Find the line starting with # Project-ID:, take the value after :, trim whitespace, and use it as <slug>. Construct the artifact base path: .project/<slug>/. All artifact reads and writes in this skill use this base path. If the header is missing, report the error and tell the user to run /project to re-bootstrap.

Revision mode detection (DEF-15): Check ALL of the following:

• prd.md exists on disk
• Gate 1 is already [x] approved in progress.txt
• The user's message signals revision intent (keywords: "revise", "update PRD", "goals changed", "pivot", "change direction", "scope change")

If ALL true: jump to Step 6 (Revision Mode).

Greenfield detection (DEF-01, D-11): Check ALL of the following (all must be true to classify as greenfield):

• No src/, app/, or lib/ directories exist
• No dependency manifests exist (package.json, pyproject.toml, Cargo.toml, go.mod, requirements.txt, Gemfile, pom.xml, build.gradle)
• Fewer than 5 non-config files
• Only boilerplate files (README, license, gitignore pattern)

If ALL true: record Gate 0 as [-] Gate 0: Codebase Alignment Skipped (greenfield) in progress.txt. Skip to Step 4 (Gate WB Offer). If ANY false: proceed to Step 2 (Gate 0).

Gate WB resume detection:

• If Gate WB is [ ] Pending in progress.txt (from a previous session where the user deferred): proceed to Step 4 (Gate WB Offer) with re-prompt context.
• If Gate 0 is not yet started [ ]: proceed to Step 2 (Gate 0).

Already-approved detection:

• If Gate 0 is [x] and Gate WB is [x] or [-] or [ ] Pending: proceed to Step 5 (Gate 1) or Step 4 if Gate WB is Pending.
• If Gate 1 is [x] and no revision intent: inform the user that Gate 1 is already complete. Ask if they want to revise (enters revision mode) or check status (run /project).

Step 2 -- Gate 0: Codebase Assessment

Read references/gate-0-codebase.md for the complete Gate 0 specification.

Follow the gate-0-codebase specification to:

1. Spawn a sub-agent to scan the codebase (20-40 files).
2. Synthesize findings into .project/<slug>/docs/codebase-assessment.md.
3. Present findings and enter produce-then-review cycle.
4. Generate review checklist (.project/<slug>/docs/reviews/gate-0-review.md) using references/review-checklist-template.md.
5. Validate checklist completeness before recording approval.
6. Record Gate 0 approval in progress.txt per references/progress-format.md.

Proceed to Step 3.

Step 3 -- Gate 0 Transition

Gate 0 is complete. Proceed to Step 4 (Gate WB Offer).

Step 4 -- Gate WB: Working Backwards (Optional)

Read references/gate-wb-working-backwards.md for the complete Gate WB specification.

Check current Gate WB state in progress.txt:

• If already [x] or [-]: skip to Step 5 (Gate 1).
• If [ ] Pending: re-prompt the user for their decision.
• If [ ] (not yet offered): offer Gate WB per the specification.

Follow the gate-wb specification to handle the 3-outcome offer:

• Yes: run WB interview, produce .project/<slug>/docs/working-backwards.md, generate review checklist (.project/<slug>/docs/reviews/gate-wb-review.md), review cycle, record approval.
• Skip: record [-] Gate WB: Working Backwards Skipped in progress.txt. Proceed to Step 5.
• Defer: record [ ] Gate WB: Working Backwards Pending -- offered, awaiting decision in progress.txt. Proceed to Step 5.

Gate WB Pending does NOT block Gate 1. The Pending state is tracked for /project to remind the user later (D-09 overrides PROJ-07).

Proceed to Step 5.

Step 5 -- Gate 1: Scope Review

Read references/gate-1-prd.md for the complete Gate 1 specification.

Follow the gate-1 specification to:

1. Silently re-read .project/<slug>/docs/codebase-assessment.md from disk for context (DEF-16). Do NOT recap or summarize it to the user -- use internally only.
2. Read .project/<slug>/docs/working-backwards.md if it exists (D-14 -- context only, does not auto-populate PRD sections).
3. Gather the initial project concept (seed the PRD).
4. Conduct the 5-round interview (Scope, Inputs/Outputs, Security, Operational, Milestone Scoping). One round at a time via AskUserQuestion.
5. Produce prd.md using assets/prd-template.md.
6. Present PRD for review (produce-then-review cycle: Approve / Revise / Partial Approve).
7. Handle partial approval if needed (DEF-12 -- section checklist for focused revision of unchecked sections).
8. Generate review checklist (.project/<slug>/docs/reviews/gate-1-review.md) using references/review-checklist-template.md.
9. Validate checklist completeness.
10. Record Gate 1 approval in progress.txt.

Proceed to Step 7 (Completion Report).

Step 6 -- Revision Mode

Read references/gate-1-prd.md for the revision mode specification. Read existing prd.md from disk. Re-read .project/<slug>/docs/codebase-assessment.md from disk if it exists (DEF-16 silent re-read -- no recap to user).

Follow the revision mode specification to:

1. Ask "What changed?" -- focused interview on affected sections only.
2. Revise prd.md with edits. Show each change before and after.
3. Present for review (produce-then-review cycle).
4. Generate or update review checklist (.project/<slug>/docs/reviews/gate-1-review.md).
5. Surface downstream artifact impacts without auto-resetting (DD-6). List affected artifacts and ask the user which need re-review.
6. Record Gate 1 re-approval with updated date in progress.txt.

Proceed to Step 7.

Step 7 -- Completion Report

Display a summary of what was produced:

DEFINITION COMPLETE: [Project Title]

ARTIFACTS CREATED:
- .project/<slug>/docs/codebase-assessment.md (Gate 0) [or "Skipped (greenfield)"]
- .project/<slug>/docs/working-backwards.md (Gate WB) [or "Skipped" / "Pending"]
- prd.md (Gate 1)

REVIEW CHECKLISTS:
- .project/<slug>/docs/reviews/gate-0-review.md [if applicable]
- .project/<slug>/docs/reviews/gate-wb-review.md [if applicable]
- .project/<slug>/docs/reviews/gate-1-review.md

NEXT: Run /project to see updated status, then /design for Gate 2.

Error Handling

• Missing progress.txt: Do not proceed. Tell the user to run /project first to bootstrap project state.
• Gate 0 already approved: Skip Gate 0 (it was already done in a previous session). Proceed from the appropriate gate based on progress.txt state.
• Gate 1 already approved without revision intent: Inform the user that Gate 1 is already complete. Use AskUserQuestion with options: Revise (enters revision mode) or Status (suggests running /project).
• Missing Project-ID header: If progress.txt exists but has no # Project-ID: line, do not proceed. Tell the user to run /project to re-bootstrap and add the Project-ID header.
• Interrupted session: If the conversation is interrupted mid-gate, the user can re-invoke /define. The skill re-reads progress.txt and resumes from the appropriate gate based on which gates are already approved.
• Agent scan failure: If the codebase scan agent fails or returns empty results, report the failure to the user and offer to proceed with a manual assessment (user describes the codebase) or retry.