dev-design

name	dev-design
description	This skill should be used when the user asks to 'design the approach', 'propose architecture', or 'choose between approaches'.
user-invocable	false
disable-model-invocation	true
hooks	{"PreToolUse":[{"matcher":"Agent","hooks":[{"type":"command","command":"GATE_ARTIFACT=.planning/SPEC_REVIEWED.md GATE_STATUS=APPROVED GATE_BLOCKED_TOOLS=Agent GATE_DESCRIPTION=\"Spec reviewed\" GATE_REMEDY=\"SPEC.md must exist AND have passed dev-spec-reviewer (SPEC_REVIEWED.md status: APPROVED) before designing. Complete brainstorm, spec review, and exploration first.\" uv run python3 ${CLAUDE_PLUGIN_ROOT}/hooks/phase-gate-guard.py"}]},{"matcher":"Write|Edit","hooks":[{"type":"command","command":"uv run python3 ${CLAUDE_PLUGIN_ROOT}/hooks/dev-plan-executable-guard.py"}]}]}

Announce: "Using dev-design (Phase 4) to propose implementation approaches and obtain user approval."

Iteration topology: one-shot + fresh-subagent plan review (dev-plan-reviewer)

Context Check

Before starting this phase, check remaining context:

Level	Remaining	Action
Normal	>35%	Proceed
Warning	25-35%	Finish the current step, then invoke dev-handoff
Critical	≤25%	Invoke dev-handoff immediately — resume fresh

At Warning/Critical: Read ${CLAUDE_SKILL_DIR}/../../skills/dev-handoff/SKILL.md and follow its instructions.

Contents

• The Iron Law of Design
• What Design Does
• Process
• Approach Categories
• PLAN.md Format
• Design Facts
• Output

Architecture Design with User Gate

Propose implementation approaches, explain trade-offs, get user approval. Prerequisites: SPEC.md finalized, exploration complete, clarifications resolved.

Prerequisite: dev-clarify Must Be Complete

dev-design REQUIRES dev-clarify to be complete. This is not optional.

Before writing PLAN.md, verify these clarify gates passed:

• Testing approach documented (unit/integration/E2E)
• Test framework specified
• First test described
• Test command documented
• User workflow confirmed

If ANY gate is unchecked → DO NOT START DESIGN. Return to dev-clarify.

## The Iron Law of Design

YOU MUST GET USER APPROVAL BEFORE IMPLEMENTATION. This is not negotiable.

After presenting approaches:

1. Show 2-3 options with trade-offs
2. Lead with your recommendation
3. Ask user which approach
4. Wait for explicit approval

Implementation CANNOT start without user saying "Yes" or choosing an approach.

STOP - you're about to implement without user approval.

What Design Does

DO	DON'T
Propose 2-3 approaches	Implement anything
Explain trade-offs clearly	Make the choice for user
Lead with recommendation	Present without opinion
Get explicit approval	Assume approval
Write PLAN.md	Skip the user gate

Design answers: HOW to build it and WHY this approach Implement executes: the approved approach (next phase, after gate)

Process

1. Review Inputs

Before designing, ensure the following exist:

• .planning/SPEC.md - final requirements
• Exploration findings - key files, patterns
• Clarified decisions - edge cases, integrations

2. Propose 2-3 Approaches

Each approach should address the same requirements differently:

Approach A: Minimal Changes

• Smallest diff, maximum reuse
• Trade-off: May be less clean, tech debt

Approach B: Clean Architecture

• Best patterns, maintainability
• Trade-off: More changes, longer implementation

Approach C: Pragmatic Balance

• Balance of speed and quality
• Trade-off: Compromise on both

3. Present with Trade-offs

Use the AskUserQuestion tool to present approaches:

# AskUserQuestion: Present 2-3 architecture approaches with trade-offs for user selection
AskUserQuestion(questions=[{
  "question": "Which architecture approach should we use?",
  "header": "Architecture",
  "options": [
    {
      "label": "Pragmatic Balance (Recommended)",
      "description": "Extend existing AuthService with new method. ~150 lines changed. Balances reuse with clean separation."
    },
    {
      "label": "Minimal Changes",
      "description": "Add logic to existing endpoint. ~50 lines changed. Fast but increases coupling."
    },
    {
      "label": "Clean Architecture",
      "description": "New service with full abstraction. ~300 lines. Most maintainable but longest to build."
    }
  ],
  "multiSelect": false
}])

Key principles:

• Lead with recommendation (first option + "Recommended")
• Concrete numbers (lines changed, files affected)
• Clear trade-offs for each
• Reference specific files from exploration

Log the review pattern (observe → record → offer)

After the user makes this decision selection, append one line to .planning/LEARNINGS.md recording what the user attended to before choosing — e.g. "compared lines-changed across options", "asked for the dependency graph", "approved on the recommendation without detail", "wanted to see affected files". Do NOT build any visualization speculatively.

Offer rule: if .planning/LEARNINGS.md shows the same review artifact requested 3+ times across episodes (e.g. the user keeps asking for a dependency graph or a diff summary before approving), offer to bundle a script under skills/dev-design/scripts/ that generates that view automatically. Build it only after the 3rd occurrence — observed behavior first, automation after.

When the offer triggers, map the observed request to a concrete artifact:

If the user keeps asking for…	Consider building
"show me what changed / a diff"	Interactive diff explorer (self-contained HTML)
"what's the architecture / dependencies?"	Dependency graph or codebase tree
"which files does this touch?"	Affected-files map from PLAN.md affects:
"how big is each approach?"	Lines-changed / files-touched comparison table

Bundle the script in skills/dev-design/scripts/; the phase offers to run it — it never forces it.

4. Feature Decomposition Check

CRITICAL: Before writing PLAN.md, check if this is actually multiple features.

Review the scope and ask:

# AskUserQuestion: Determine if feature should be split into independent tasks
AskUserQuestion(questions=[{
  "question": "Is this one cohesive feature or multiple independent features?",
  "header": "Scope",
  "options": [
    {
      "label": "One feature",
      "description": "Implement everything together in one branch/worktree"
    },
    {
      "label": "Multiple features",
      "description": "Break into separate features, each with own branch/worktree/PR"
    }
  ],
  "multiSelect": false
}])

If "Multiple features":

1. List the independent features identified from SPEC.md:

   Based on the requirements, this breaks into:
   1. Theme infrastructure (color system, theme provider)
   2. Settings UI (theme selector component)
   3. Component updates (update 20+ components to use theme)
   4. Persistence layer (save user preference)
   
   Each can be implemented and PR'd independently.
   

2. Ask which to tackle first:

   # AskUserQuestion: Prioritize which feature to implement first
   AskUserQuestion(questions=[{
     "question": "Which feature should we implement first?",
     "header": "Priority",
     "options": [
       {"label": "Theme infrastructure (Recommended)", "description": "Foundation that others depend on"},
       {"label": "Settings UI", "description": "UI for theme selection"},
       {"label": "Component updates", "description": "Apply themes to components"},
       {"label": "Persistence layer", "description": "Save user preference"}
     ],
     "multiSelect": false
   }])
   

3. Write PLAN.md for ONLY the chosen feature

4. Document remaining features in .planning/BACKLOG.md:

   # Feature Backlog
   
   ## Dark Mode Implementation
   
   ### Completed
   - [ ] None yet
   
   ### Next Up
   - [ ] Theme infrastructure
   - [ ] Settings UI
   - [ ] Component updates
   - [ ] Persistence layer
   
   **Current Focus:** Theme infrastructure
   

If "One feature":

Proceed to write PLAN.md for the entire scope (step 5 below).

Why this matters:

• Multiple features in one branch = massive PR, review hell, merge conflicts
• Separate features = clean PRs, incremental progress, easier reviews
• After first feature PR merges, come back and tackle next feature

4b. Prose Section Audit (MANDATORY)

Before writing PLAN.md, scan ALL sections of SPEC.md for behavioral statements that lack CATEGORY-NN IDs.

Check these sections specifically:

• Design Decisions
• Discovered Protocol
• Clarified Requirements
• Any other prose sections outside the Requirements table

Any prose that describes an implementable feature, user-facing behavior, protocol handling, or UI element MUST have a corresponding CATEGORY-NN ID in the Requirements table.

If any implementable feature lacks an ID → STOP. Add it to the Requirements table before writing PLAN.md.

Un-ID'd requirements in prose are invisible to PLAN.md task mapping, VALIDATION.md coverage, and dev-verify tracing. They will be silently dropped from the entire implementation.

5. Write PLAN.md

After user chooses approach AND confirms scope, write .planning/PLAN.md:

PLAN.md Template

Use the template from references/plan-template.md for the PLAN.md structure. Load it before writing the plan:

Read ${CLAUDE_SKILL_DIR}/../../skills/dev-design/references/plan-template.md and follow its instructions.

6. User Gate - Final Approval

Checkpoint type: decision (user chooses architecture — cannot auto-advance)

After writing PLAN.md, get explicit approval:

AskUserQuestion(questions=[{
  "question": "Ready to start implementation?",
  "header": "Approval",
  "options": [
    {"label": "Yes, proceed", "description": "Start implementation with TDD"},
    {"label": "No, discuss changes", "description": "Modify the plan first"}
  ],
  "multiSelect": false
}])

If "No": Wait for user feedback, modify plan, ask again.

If "Yes": Proceed to workspace setup question in Step 7 below.

7. Workspace Setup Question

Checkpoint type: decision (user chooses workspace setup — cannot auto-advance)

After user approves implementation, ask about worktree isolation:

AskUserQuestion(questions=[{
  "question": "Create isolated worktree for this feature?",
  "header": "Workspace",
  "options": [
    {"label": "Yes (Recommended)", "description": "Work in isolated .worktrees/ directory - keeps main workspace clean"},
    {"label": "No", "description": "Work in current directory"}
  ],
  "multiSelect": false
}])

If "Yes (Recommended)":

Invoke the dev-worktree skill:

# dev-worktree: Create isolated git worktree for feature development
Skill(skill="workflows:dev-worktree")

Then after worktree is created, invoke dev-implement.

If "No":

Directly invoke dev-implement in current directory without worktree isolation.

Approach Categories

Category	When to Use	Trade-off
Minimal	Bug fixes, small features	Speed vs cleanliness
Clean	New systems, core features	Quality vs time
Pragmatic	Most features	Balance

PLAN.md Format

Required sections:

• Chosen Approach - What was selected and why
• Testing Strategy - Framework, command, first test, location, skill
• REAL Test Criteria - User workflow, protocol, UI elements, what user sees
• Files to Modify - Specific paths with change descriptions
• New Files - If any, with purposes
• Implementation Order - the MANDATORY machine-executable table: Task | Deps | Files | Failing Test | Verify Command | Implements, one row per task, every column filled (see references/plan-template.md). dev-implement reads this table to build the dependency DAG and the per-task verify gates — record tasks as table ROWS, never as prose ### Phase headings. Enforced: dev-plan-executable-guard.py blocks PLAN_REVIEWED.md until the table is complete and the Deps graph is an acyclic, resolvable DAG. Self-check before approving: uv run python3 ${CLAUDE_SKILL_DIR}/../../hooks/dev-plan-executable-guard.py .planning/PLAN.md.
• Global Constraints (recommended) - a ## Global Constraints block of invariants binding every task; Task Interfaces (recommended) - one ### Task N Consumes/Produces block per task. Both are OPTIONAL and backward-compatible (the guard does not require them, and task-brief.sh produces valid briefs without them). When present, task-brief.sh folds the Global Constraints + the task's Interfaces into each per-task brief, so the implementer reads ONE self-contained file instead of re-reading the whole plan — see references/plan-template.md.

PLAN Self-Containment Facts

• A pasted task and a re-read of the full PLAN.md are the two failure modes the brief sits between: pasting parks the bytes in the controller's context, "go read PLAN.md" makes the implementer guess scope. The brief (task-brief.sh → .planning/handoff/task-N-brief.md) is the scoped middle — pin Global Constraints + Interfaces in the plan so the brief is genuinely self-contained, or the implementer falls back to one of the two failure modes.

The Gate Function

This is the canonical IDENTIFY → RUN → READ → VERIFY → CLAIM gate, expanded into 12 ordered steps. The phases map as: IDENTIFY/RUN = steps 1-2 (read SPEC.md + exploration), READ/VERIFY = steps 6b, 8 (prose audit + testing-table checks), CLAIM = step 12 (start /dev-implement). CLAIM is reachable ONLY if every prior step passed — the PLAN_REVIEWED.md hook downstream blocks implement if it did not.

Complete all steps before starting implementation:

1. REVIEW → Read SPEC.md and exploration findings
2. VERIFY TESTING → Check SPEC.md has automated testing strategy
   └─ If missing → STOP. Go back to clarify phase.
3. PROPOSE → Present 2-3 approaches with trade-offs
4. ASK → Use AskUserQuestion with clear options
5. DECOMPOSE → Ask "One feature or multiple?" (CRITICAL)
   └─ If multiple → List features, ask which first, write BACKLOG.md
6. WAIT → Do NOT proceed until user responds
6b. PROSE AUDIT → Scan ALL SPEC.md prose sections for un-ID'd behavioral requirements (MANDATORY)
   └─ If found → STOP. Add CATEGORY-NN IDs to Requirements table before proceeding.
7. DOCUMENT → Write PLAN.md with Testing Strategy section FILLED
8. VERIFY PLAN → Check PLAN.md Testing Strategy table has all boxes checked
   └─ If any unchecked → STOP. Fill them before proceeding.
9. CONFIRM → Ask "Ready to proceed?"
10. WORKSPACE → Ask "Create worktree?" (Yes recommended / No)
11. SETUP → If worktree Yes, invoke dev-worktree
12. GATE → Only start /dev-implement after all approvals

Mandatory steps (NEVER skip): VERIFY TESTING, DECOMPOSE, PROSE AUDIT, VERIFY PLAN, WAIT, WORKSPACE, and GATE.

Testing Strategy Verification (Step 2 & 8)

Before proceeding past step 2, verify SPEC.md contains:

[ ] Testing approach (unit/integration/E2E)
[ ] Test framework (pytest/jest/playwright)
[ ] Test command (how to run)
[ ] Testing skill specified (dev-test-electron/playwright/etc.)

Before proceeding past step 8, verify PLAN.md Testing Strategy table:

[ ] Framework filled
[ ] Test Command filled
[ ] First Failing Test described
[ ] Test File Location specified
[ ] Testing Skill specified

If any box is unchecked → STOP. Do not proceed.

REAL Test Verification (Step 8 - CRITICAL)

Before proceeding past step 8, verify PLAN.md REAL Test Criteria table:

[ ] User workflow documented (exact steps user takes)
[ ] Protocol matches production (WebSocket/HTTP/IPC/etc.)
[ ] UI elements identified (what user interacts with)
[ ] User-visible output documented (what user sees)
[ ] Code path specified (same path as production)

If any box is unchecked → You WILL write fake tests. Fix now.

Fake Test Prevention Check (Step 8)

Ask yourself before proceeding:

1. Will the test use the SAME protocol as production? (Not a substitute)
2. Will the test follow the EXACT user workflow? (Not shortcuts)
3. Will the test use the SPECIFIED testing skill? (Not your own approach)
4. Will the test verify what the USER sees? (Not internal state)

If ANY answer is "no" → STOP. Fix the REAL Test Criteria section.

Design Facts

• Behavioral requirements without REQ-IDs hide in SPEC.md prose sections — Design Decisions, Discovered Protocol, Clarified Requirements. A PLAN.md written without the Prose Section Audit (step 4b) silently drops them from the entire traceability chain, and implementers execute the plan literally: what the plan omits never gets built.
• "Only one viable option" still gets presented as an option with trade-offs — the user routinely has context you lack and sees alternatives you missed; choosing for them converts their approval gate into a notification.

Output

Design complete when:

• 2-3 approaches presented with trade-offs
• User chose an approach
• .planning/PLAN.md written with chosen approach
• User explicitly approved ("Yes, proceed")

Phase Complete

Phase summary (append to LEARNINGS.md):

## Phase: Design

---
phase: design
status: completed
requires: [SPEC.md, clarified-requirements]
provides: [PLAN.md, PLAN_REVIEWED.md, architecture-decision]
chosen-approach: [one-liner describing selected approach]
---

After user approves ("Yes, proceed"):

1. Plan Review Gate (MANDATORY — produces .planning/PLAN_REVIEWED.md): Discover and read the plan reviewer skill:Read ${CLAUDE_SKILL_DIR}/../../skills/dev-plan-reviewer/SKILL.md and follow its instructions. Follow the plan reviewer's instructions:

   • If >15 tasks → chunk the plan first, review per-chunk
   • Dispatch reviewer subagent
   • If ISSUES_FOUND → fix PLAN.md → re-dispatch (max 5 iterations)
   • If APPROVED → write .planning/PLAN_REVIEWED.md (per dev-plan-reviewer instructions) → proceed to worktree question
   **`.planning/PLAN_REVIEWED.md` is the structural handoff artifact.** dev-implement will REFUSE to start without it. You CANNOT skip this step. If you proceed to step 2 without PLAN_REVIEWED.md existing, implementation will be blocked.

2. Ask about worktree (Step 7 above)

3. If worktree chosen:

   • Invoke Skill(skill="workflows:dev-worktree")
   • After worktree created, discover and read skills/dev-implement/SKILL.md via cache lookup, then invoke with Read()

4. If no worktree:

   • Directly discover and read skills/dev-implement/SKILL.md via cache lookup, then invoke with Read()

Required before proceeding:

• Explicit user approval for implementation
• Feature scope decision (one feature vs multiple)
• .planning/PLAN_REVIEWED.md exists with status: APPROVED
• User choice on worktree (Yes/No)

After this feature is implemented and PR'd:

If multiple features were identified in step 4, check .planning/BACKLOG.md for remaining features:

1. View remaining features in BACKLOG.md
2. Invoke /dev again to tackle the next feature
3. Repeat until all features are complete

This enables incremental development: one feature → PR → merge → next feature.