/design -- Architecture and Design (Gate 2)

Produces .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md from an approved PRD and
optional codebase assessment, with in-session revision before gate approval. Supports
refresh mode to consolidate accumulated architectural deviations from feature
plans.

Rules

• Read fresh every time. Read progress.txt from disk on every invocation --
  never rely on conversation memory or cached values (STATE-03).
• Produce-then-review at every gate. Produce the full artifact, present it,
  offer Approve / Revise / Partial. Rejection = revision request (D-10).
• All checklist items must be resolved. Every review checklist item must be
  [x] or [-] (N/A with reason) before recording gate approval (D-11).
• Write-ordering contract. When writing to state files, follow STATE-04
  ordering. For /design, only progress.txt is modified (gate entry).
• 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).
• progress.txt must exist. If it does not, instruct the user to run /project
  first to bootstrap project state.
• Gate 1 must be [x] approved in progress.txt (DES-01).

Step 1 -- Detect Mode and State

Read progress.txt from the project root. Parse # Project-ID: <slug> from the
header and construct the artifact base path: .project/<slug>/. Use this base path
for all artifact reads and writes throughout this session.

Prerequisite check (DES-01):
If Gate 1 is not [x] approved in progress.txt, inform the user:
"Gate 1 (Scope Review) must be approved before running /design. Run /define to
complete the PRD first."
Do not proceed. End the session.

Refresh mode detection (DES-08):
Check ALL of the following:

• Gate 2 is [x] approved in progress.txt
• .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md exists on disk

If ALL true: jump to Step 4 (Refresh Mode).

Already-approved detection (no refresh intent):
If Gate 2 is [x] approved AND .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md exists AND
the user's message does NOT signal refresh intent (keywords: "refresh", "update
architecture", "consolidate deviations", "sync deviations"):
Inform the user Gate 2 is already approved. Use AskUserQuestion with options:
Refresh (enters refresh mode) or Status (suggests running /project).

Normal mode:
If Gate 2 is not yet approved: proceed to Step 2 (Architecture Generation).
Before generating, Step 2 checks whether .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md
already exists on disk and integrates into it rather than overwriting (see
references/gate-2-design.md for details).

Step 2 -- Architecture Generation

Read references/gate-2-design.md for the complete Gate 2 specification.

Follow the gate-2-design specification to:

1. Read prd.md and .project/{slug}/docs/codebase-assessment.md (if exists) (DES-02).
2. Spawn architecture sub-agent to scan 15-30 files (D-05, D-06).
3. Synthesize findings + PRD into .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md using
   assets/architecture-template.md (DES-03).
4. Present tradeoff callouts for 2-4 key decisions (D-09).
5. Enter produce-then-review cycle with section-by-section partial approval
   (DES-05, DES-06, D-08).
6. Generate and validate review checklist .project/{slug}/docs/reviews/gate-2-review.md
   (DES-04, D-11).
7. Record Gate 2 approval in progress.txt (DES-07).

Proceed to Step 3.

Step 3 -- Completion Report

Display summary of what was produced:

DESIGN COMPLETE: [Project Title]

ARTIFACTS CREATED:
- .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md (Gate 2)

REVIEW CHECKLISTS:
- .project/{slug}/docs/reviews/gate-2-review.md

NEXT: Run /project to see updated status, then /milestone for Gate 3.

Step 4 -- Refresh Mode

Read references/refresh-mode.md for the complete refresh mode specification.

Follow the refresh-mode specification to:

1. Scan .project/{slug}/milestones/*/plans/*.md for Architectural Deviations sections.
2. If zero deviations found: report "No architectural deviations found.
   Architecture doc is current." and exit (D-14).
3. Present each deviation with original design decision context (D-12).
4. User selects which deviations to consolidate via multiSelect.
5. Apply selected deviations to .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md (D-13).
6. Present updated doc for section-by-section review.
7. Update Gate 2 date in progress.txt.

Display refresh completion summary:

DESIGN REFRESHED: [Project Title]

DEVIATIONS CONSOLIDATED: N of M
ARTIFACTS UPDATED:
- .project/{slug}/docs/ARCHITECTURE_AND_DESIGN.md (refreshed)

NEXT: Run /project to see updated status.

Error Handling

• Missing progress.txt: Do not proceed. Tell the user to run /project first
  to bootstrap project state.
• Gate 1 not approved: Do not proceed. Tell the user to run /define first
  (DES-01).
• Gate 2 already approved without refresh intent: Inform the user, offer
  Refresh or Status check.
• Agent scan failure: Report failure, offer manual architecture input (user
  describes system) or retry.
• Existing architecture doc found (Gate 2 not approved): The document is
  preserved and new content is integrated. If the existing document is
  unreadable, empty, non-text/binary, or does not resemble Markdown, inform
  the user that it cannot be used as the existing architecture document and
  offer: Overwrite (start fresh) or Abort (user fixes manually).
• Missing prd.md: This should not happen if Gate 1 is approved. Report
  inconsistency -- Gate 1 is marked approved but prd.md is missing. Suggest
  running /project to check state.
• Interrupted session: User can re-invoke /design. Skill re-reads
  progress.txt and resumes from appropriate state.