/implement

Make failing tests pass with minimal code.

Usage

/implement

The implementer will automatically find failing tests from the most recent /write-tests run.

When to Use

• After /write-tests has created failing tests

• When you have specific tests that need implementation

• Never before tests exist

When NOT to Use

• No failing tests exist (run /write-tests first)

• You want to add features not covered by tests

• You want to refactor (use /simplify instead)

What It Does

• Finds the failing tests from /write-tests

• Reads tests to understand requirements

• Writes the minimum code to make tests pass

• Runs tests after each change

• Stops when ALL tests pass

Output

The implementer agent will produce:

Implementation Complete

Tests Passed

• test_client_reset_returns_observation ✓
• test_client_step_advances_state ✓
• test_client_handles_invalid_action ✓

Changes Made

Verification

PYTHONPATH=src:envs uv run pytest tests/test_client.py -v All 3 tests passed

Next Steps

• Mark todo as complete
• Consider /simplify if change was large
• Move to next pending todo

Rules

• Read the failing tests first to understand exactly what's needed

• Write the MINIMUM code needed to pass tests

• Run tests after each change to verify progress

• Do NOT add extra features not covered by tests

• Do NOT refactor existing code (that's /simplify 's job)

• Stop when all tests pass

Anti-patterns (NEVER do these)

• Adding features not covered by tests

• Refactoring existing code

• Writing additional tests (that's /write-tests 's job)

• Over-engineering solutions

• Adding comments or documentation beyond what's necessary

• "Improving" code that already works

Completion Criteria

Before returning, verify:

• ALL tests pass

• No new test failures introduced

• Implementation is minimal and focused

Philosophy

The implementer is a "code machine" - it takes test specifications and produces the minimal code to satisfy them. This keeps implementations focused and prevents scope creep.

Think of it as TDD's second phase: Red → Green → Refactor. You are "Green" - make tests pass, nothing more.