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. TDD. Frequent commits.

Assume they are a skilled developer, but know almost nothing about our toolset or problem domain. Assume they don't know good test design very well.

Announce at start: "I'm using the sd-plan skill to create the implementation plan."

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

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

> **For Claude:** REQUIRED SUB-SKILL: Use sd-plan-dev to implement this plan task-by-task.

**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.ts`
- Modify: `exact/path/to/existing.ts:123-145`
- Test: `exact/path/to/tests/file.spec.ts`

**Step 1: Write the failing test**

```typescript
test("specific behavior", () => {
  const result = functionUnderTest(input);
  expect(result).toBe(expected);
});

Step 2: Run test to verify it fails

Run: pnpm vitest exact/path/to/tests/file.spec.ts --run Expected: FAIL with "functionUnderTest is not defined"

Step 3: Write minimal implementation

function functionUnderTest(input: InputType): OutputType {
  return expected;
}

Step 4: Run test to verify it passes

Run: pnpm vitest exact/path/to/tests/file.spec.ts --run Expected: PASS

Step 5: Commit

git add exact/path/to/tests/file.spec.ts exact/path/to/file.ts
git commit -m "feat: add specific feature"

## Remember
- Exact file paths always
- Complete code in plan (not "add validation")
- Exact commands with expected output
- DRY, YAGNI, TDD, frequent commits

## Execution Handoff

After saving the plan:

**"Plan complete and saved to `docs/plans/<filename>.md`. Ready to execute with sd-plan-dev?"**

- **REQUIRED SUB-SKILL:** Use sd-plan-dev
- Fresh fork per task + two-stage review (spec compliance → code quality)