Tdd Plan

Step 4 — Write the implementation plan

Output a structured plan with the following sections:

## Implementation Plan — <feature name>

### Summary
<1–2 sentences: what this change does and why>

### Files to change
- <file path> — <what changes and why>

### Files to leave untouched
- <file path> — <why it must not change>

### Test plan (in order)
1. <Test: what behaviour it covers>
2. <Test: what behaviour it covers>
...

### Implementation steps (in order)
1. <Step: what to do, which file, what the change achieves>
2. ...

### Risks and unknowns
- <Anything uncertain that tdd-implement should watch for>

Stop after producing the plan. Hand off to tdd-implement to execute it.

Rules

• Do not write implementation code. Plan only.
• Do not start the plan until the requirement is fully understood.
• Be specific — file paths, method names, test descriptions. No vague steps.
• If the investigation reveals the feature is larger than expected, say so before producing the plan.