writing-plans

name	writing-plans
description	Use when you have a spec or requirements for a multi-step task, before touching code. Use this skill whenever the user wants to plan an implementation, break down a complex task, or needs a structured approach before coding.

Writing Plans

Overview

Write comprehensive implementation plans assuming the engineer has zero context for our codebase and questionable taste. Document everything they need to know: which files to touch for each task, code, testing, docs they might need to check, how to test it. Give them the whole plan as bite-sized tasks. DRY. YAGNI. Frequent commits.

Assume they are a skilled developer, but know almost nothing about our toolset or problem domain.

Announce at start: "Je vais utiliser la skill writing-plans pour créer le plan d'implémentation."

Save plans to: docs/plans/YYYY-MM-DD-<feature-name>.md

Scope Check

If the spec covers multiple independent subsystems, suggest breaking this into separate plans — one per subsystem. Each plan should produce working, testable software on its own.

File Structure

Before defining tasks, map out which files will be created or modified and what each one is responsible for.

• Design units with clear boundaries and well-defined interfaces
• Prefer smaller, focused files over large ones that do too much
• Files that change together should live together
• In existing codebases, follow established patterns

Bite-Sized Task Granularity

Each step is one action (2-5 minutes):

• "Write the failing test" - step
• "Run it to make sure it fails" - step
• "Implement the minimal code to make the test pass" - step
• "Run the tests and make sure they pass" - step
• "Commit" - step

Plan Document Header

Every plan MUST start with this header:

# [Feature Name] Implementation Plan

**Goal:** [One sentence describing what this builds]

**Architecture:** [2-3 sentences about approach]

**Tech Stack:** [Key technologies/libraries]

---

Task Structure

### Task N: [Component Name]

**Files:**
- Create: `exact/path/to/file.py`
- Modify: `exact/path/to/existing.py:123-145`
- Test: `tests/exact/path/to/test.py`

- [ ] **Step 1: Write the failing test**
- [ ] **Step 2: Run test to verify it fails**
- [ ] **Step 3: Write minimal implementation**
- [ ] **Step 4: Run test to verify it passes**
- [ ] **Step 5: Commit**

No Placeholders

Every step must contain the actual content an engineer needs. These are plan failures — never write them:

• "TBD", "TODO", "implement later", "fill in details"
• "Add appropriate error handling" / "add validation" / "handle edge cases"
• "Write tests for the above" (without actual test code)
• "Similar to Task N" (repeat the content)
• Steps that describe what to do without showing how

Remember

• Exact file paths always
• Complete code in every step
• Exact commands with expected output
• DRY, YAGNI, frequent commits

Self-Review

After writing the complete plan, check against the spec:

1. Spec coverage: Skim each requirement. Can you point to a task that implements it?
2. Placeholder scan: Search for red flags from the "No Placeholders" section
3. Type consistency: Do types and method names match across tasks?

Fix issues inline. No need to re-review.