| name | implementation |
| description | Use when requirements are clear and code must be added, changed, or fixed against an observable success criterion. |
This skill defines the implementation phase. Use the `engineer` agent when a bounded implementation can proceed independently; otherwise work locally. Produce tested changes in coherent slices and report material deviations.
Use lifecycle-documentation only when the result needs a durable artifact or handoff.
Build it, test-first. Write the failing test that defines the behavior, then write the code that makes it pass. Deliver one step at a time, keeping the tree green at every step.
Make the smallest diff that meets the requirement. Touch only what the task demands, and respect the out_of_scope fence.
The loop
- Write a failing test that captures the next slice of behavior.
- Make it pass with the simplest code that works.
- Run the verify command. Green → next slice. Red → fix before moving on.
Principles
- Incremental over big-bang — small, verified steps.
- Smallest diff that solves the problem; no refactoring of unbroken code.
- Match the surrounding code's style and idioms.
- The code's own tests are yours — write them test-first. The
tester adds adversarial tests later, never instead of these.
