Plan

Plan

Purpose: Create detailed implementation plan without writing code Mode: Read-only — no code changes Usage: /plan [scope flags] <task description>

Iron Laws

1. NO CODE IN PLANNING — This is a read-only skill. Do not write, edit, or modify any source files. Planning only.
2. EVERY STEP MUST BE ACTIONABLE — Vague steps like "update the auth module" are not plans. Specify the file path, what changes, and what the result looks like.
3. NO PLAN WITHOUT APPROVAL — Do not proceed to implementation without explicit user approval of the plan.

When to Use

• Before implementing a new feature
• Before making significant changes to existing code
• When the approach is unclear and needs design
• When multiple files or components are affected

When NOT to Use

• Simple single-file changes with clear approach → just /implement
• You could describe the diff in one sentence → edit directly
• Bug investigation → /debug
• Refactoring with known pattern → /refactor

Scope Flags

Workflow

Step 1: Parse Scope

git branch --show-current
git status --porcelain

Step 2: Interview (for complex or ambiguous tasks)

Before exploring code, interview the user to clarify requirements:

1. What's the desired end state? (success criteria, not task description)
2. What constraints exist? (performance, compatibility, dependencies)
3. Any approaches you've considered or want to avoid?
4. Edge cases that matter to you?

Skip this step if the user provided a detailed spec or the task is straightforward.

Step 3: Explore Relevant Code

Delegate large explorations (6+ files) to parallel agents to preserve context.

1. Search for related files
2. Read key components
3. Understand existing patterns
4. Identify dependencies

Step 4: Assess Complexity

For Complex and Risky, present 2-3 alternative approaches with trade-offs before recommending one. Use this template:

### Alternatives Considered
| Option | Pros | Cons | Effort |
|--------|------|------|--------|
| A: [approach] | ... | ... | ... |
| B: [approach] | ... | ... | ... |
**Recommended:** [option] because [reasoning]

Step 5: Create Plan

Every step must include: exact file path, what specifically changes, representative code snippet showing the change shape, clear deliverable, and estimated scope.

## Implementation Plan

### Summary
[1-2 sentences]

### Files to Modify
| File | Change | Lines |
|------|--------|-------|
| `src/auth/login.ts` | Add input validation to handleSubmit | ~15 |

### Steps

**Step 1: [Action verb] [specific target]** (~2-5 min)
- File: `src/auth/login.ts`
- Change: [specific description]
- Code shape:
  ```typescript
  // Before → After showing the change

• Deliverable: [what's true after this step]

Edge Cases

Test Strategy

• [Specific test scenario with expected assertion]

Security Considerations

• Handles user input? → Validation required at entry point
• Touches auth/authz? → Verify access controls preserved
• Stores/transmits sensitive data? → Encryption and secrets management
• Calls external services? → Input sanitization and response validation
• N/A — no security-sensitive changes

When the plan involves security-sensitive work (auth, input handling, data access), connect security considerations to specific plan steps rather than listing them separately. Add a "Security:" annotation to each relevant step. Example: "Step 3: Add OAuth callback handler — Security: validate redirect URL against allowlist, use state parameter for CSRF prevention." This ensures security requirements are visible when /implement executes each step.

Risks

Approve this plan? (yes / no / modify)

For Complex/Risky plans, optionally include a Mermaid diagram showing component relationships or data flow.

### Step 6: Wait for Approval

**GATE: Do NOT proceed to implementation without explicit approval.**

See `ai-assistant-protocol` for valid approval terms and invalid responses.

**Plan/Implement Boundary:** The `/plan` skill produces a plan document that can be executed by `/implement`. The plan is complete when: (a) every step has a specific file path, (b) code shapes show the structure of changes, (c) edge cases are identified with handling strategies, (d) the user has approved the plan. Do NOT start implementation — that is `/implement`'s job.

### Step 7: Persist Plan as Todos

After approval, invoke `/add-todo` for each plan step to create trackable, persistent work items.

For each step in the approved plan, create a todo with:
- **Title:** The step's action (e.g., "Add input validation to handleSubmit")
- **Category:** `feature` (or `refactor`, `test`, etc. as appropriate)
- **Description:** The step's specific changes, file paths, and deliverable from the plan
- **Affected Files:** Exact files from the plan step
- **Acceptance Criteria:** The step's deliverable restated as checkable criteria

```markdown
## Todos Created

| Todo | File | Priority |
|------|------|----------|
| `add-input-validation.md` | `.ai-project/todos/` | medium |
| `update-api-handler.md` | `.ai-project/todos/` | medium |
| `add-validation-tests.md` | `.ai-project/todos/` | medium |

Each step is now a trackable todo. When completed, `/add-todo` will prompt
for an ADR capturing the decision, then remove the todo.

Skip this step for Trivial plans (1-2 files, single bullet list).

Step 8: Execution Handoff

## Next Steps

Choose execution mode:
- **`/implement`** — Execute the plan step by step (default)
- **`/tdd`** — Test-driven execution (write tests first, then implement)
- **Parallel dispatch** — Break independent tasks into parallel agent work (for Complex plans)
- **Manual** — You execute, I advise

Which approach?

Plan Quality Checklist

Before presenting the plan, verify (see references/plan-quality-checklist.md for detailed guidance with examples for each item):

• Every step has an exact file path
• Every step has a clear deliverable
• Code snippets show the shape of changes
• Edge cases have explicit handling
• Test strategy names specific scenarios
• Risks have mitigation strategies
• Steps are ordered by dependency
• No step takes longer than 5 minutes of focused work

Acceptance Tests

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