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 writing-plans skill to create the implementation plan."

Context: This should be run in a dedicated worktree (created by brainstorming skill).

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

Requirements Restatement (Step 1 of Every Plan)

Before writing any plan content, always output:

Requirements as I understand them:

• [Requirement 1 — in your own words]
• [Requirement 2]
• [Assumption 1]

Wait for human confirmation before investing in plan detail. Misunderstandings caught here save hours of wasted implementation.

Plan Document Header

Every plan MUST start with this header:

# [Feature Name] Implementation Plan

> **For Claude:** REQUIRED SUB-SKILL: Use sp-ecc:executing-plans 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]

**Complexity:** High / Medium / Low

**Risks:**
- HIGH: [risk — mitigation]
- MEDIUM: [risk — mitigation]

**Testing:** Unit: [what], Integration: [what], E2E: [if applicable]

---

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`

**Depends on:** Task N (if applicable, omit if none)

**Step 1: Write the failing test**

```python
def test_specific_behavior():
    result = function(input)
    assert result == expected

Step 2: Run test to verify it fails

Run: pytest tests/path/test.py::test_name -v Expected: FAIL with "function not defined"

Step 3: Write minimal implementation

def function(input):
    return expected

Step 4: Run test to verify it passes

Run: pytest tests/path/test.py::test_name -v Expected: PASS

Step 5: Commit

git add tests/path/test.py src/path/file.py
git commit -m "feat: add specific feature"

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

## Phasing Large Features

For features spanning 10+ tasks, phase into independently shippable slices:
- **MVP:** Smallest slice that provides value
- **Core:** Complete happy path
- **Hardening:** Edge cases, error handling
- **Polish:** Optimization, monitoring

Each phase should be mergeable on its own.

## Plan Quality Red Flags

Before presenting the plan, check:
- [ ] Every task has exact file paths
- [ ] Testing strategy is included
- [ ] Dependencies between tasks are noted
- [ ] Each phase can ship independently (for large features)
- [ ] No steps say "add validation" — complete code is provided

## Execution Handoff

After saving the plan, ask for approval:

End every plan document with:

---
**READY?** Proceed / Modify: [changes] / Different approach: [alternative]

**"Plan complete and saved to `docs/plans/<filename>.md`. Ready to execute?"**

**If approved:**
- **REQUIRED SUB-SKILL:** Use sp-ecc:subagent-driven-development
- Stay in this session
- Fresh subagent per task + multi-stage review (spec, quality, security, verification gate)