swift-feature-implementation

name	swift-feature-implementation
description	Use for implementing a non-trivial Swift 6.3 feature, bug fix, or refactor. It coordinates repository inspection, relevant domain skills, implementation, and proof; it does not authorize unrelated cleanup.

Swift feature implementation

Own the requested behavior from baseline to proof. Route domain knowledge only when the task needs it.

Workflow

1. Read repository instructions, inspect the affected targets and call sites, and state the user-visible behavior and invariant.
2. Establish a baseline: reproduce the bug, run focused tests, or record the current behavior. Identify existing edits and preserve them.
3. Select the smallest relevant domain skills from the routing map; do not load the entire suite. Identify a design that fits existing ownership, isolation, and boundary conventions.
4. Write or update a failing focused test when behavior is missing. Implement the smallest coherent change, keeping unsafe/effectful code at its boundary.
5. Run formatter/linter, focused tests, target tests, and the repository's real gate. Add adversarial cases for malformed input, errors, cancellation, lifetime, and compatibility when relevant.
6. Review the diff for scope, API, ownership, concurrency, performance claims, and test quality. Report failures as code, infrastructure, or unavailable platform evidence.

Read references/implementation-checklist.md when the task spans multiple targets or has a release boundary.

Guardrails

• Do not weaken strict concurrency, remove tests, broaden public API, or add compatibility shims to make the change easier.
• Do not call a focused pass a full repository gate.
• Do not claim hardware/private-API behavior from a host-only test.

Completion contract

Summarize behavior, invariant, files changed, checks run and their scope, manual evidence, and any remaining proof gap.