features

# Backend Feature Development Use this skill for Python backend changes. ## Workflow 1. Read `AGENTS.md` before coding. 2. Read the required specs listed in `AGENTS.md` for the affected protocol or feature area. 3. Read scoped AGENTS files for touched subtrees, such as `src/merchant/AGENTS.md`, `src/apps_sdk/AGENTS.md`, or `src/agents/AGENTS.md`. 4. Implement minimal, spec-aligned changes. 5. Add or update tests for new behavior, edge cases, and failure paths. 6. Run the relevant quality gates and report exact evidence. ## Python Standards - Use type hints for public APIs and non-trivial logic. - Prefer explicit, readable code over clever abstractions. - Avoid side effects at import time. - Mock external services and I/O in tests. - Do not add secrets, credentials, or sensitive data. - Add comments only where they clarify non-obvious behavior. ## CI Parity Run these commands from the repo root before committing backend-related changes: ```bash uv run ruff check src/merchant/ src/payment/ src/apps_sdk/ tests/ uv run ruff format --check src/merchant/ src/payment/ src/apps_sdk/ tests/ uv run pyright src/merchant/ src/payment/ src/apps_sdk/ uv run pytest tests/ -v --tb=short ``` Rules: - Do not commit if any required command fails. - If changes touch both backend and UI, run the UI CI parity commands in `skills/ui/SKILL.md`. - Targeted tests are fine while iterating, but full relevant checks are required before commit unless explicitly skipped with a reason. ## Testing Standards - Name tests `test_*.py`. - Assert behavior, not implementation details. - Prefer fixtures over ad hoc setup/teardown logic. - Use parametrized tests for related cases. - Cover happy paths, edge cases, and failure paths when behavior changes. ## Review Expectations - No commented-out code. - No TODOs without an issue reference. - No dead code. - No ignored warnings or silenced type errors unless justified. - Clear, descriptive function and variable names. The work is incomplete if tests are missing for changed behavior, Ruff or type checks are unresolved, or code behavior conflicts with the required docs.