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Python architecture patterns including KISS, SRP, separation of concerns, composition over inheritance, dependency injection, project structure, module organization, and public API design. Use when designing new components, organizing projects, planning directory layouts, refactoring complex code, or deciding between inheritance and composition.

Python code quality patterns including style, formatting, naming conventions, docstrings, type annotations, generics, protocols, and anti-pattern avoidance. Use when writing new code, reviewing style, configuring ruff/mypy/pyright, adding type hints, implementing generics or protocols, or reviewing code for common mistakes.

Python robustness patterns including input validation, exception hierarchies, retry logic, timeouts, and fault-tolerant decorators. Use when implementing validation, designing exception strategies, adding retry logic, handling transient failures, handling batch partial failures, or building fault-tolerant services.

Use when designing test suites, planning test coverage, choosing which layer (unit/integration/E2E) to test at, writing test cases for microservice chains, state machines, or complex business logic. Use when asking how to scope tests, how to avoid over-testing across service boundaries, or how to apply equivalence partitioning, boundary value analysis, or decision tables.

Playwright implementation reference for E2E tests: Page Object Model, auth state reuse, artifact management (screenshots/traces/video), CI/CD integration, and flaky test handling. Use when implementing Playwright tests in Python/pytest. For E2E test design strategy and scope decisions, see designing-tests skill.

Use when building Go Web projects with DDD and Clean Architecture on the github.com/go-jimu/template ecosystem. Covers: project bootstrapping with gonew, layer isolation (domain/application/infrastructure), Aggregate Roots with validation and events, Value Objects, CQRS (Commands + Queries), Domain Events via Mediator, Repository pattern with XORM, ConnectRPC API layer, fx dependency injection wiring, error handling with oops, and testing strategy. Use when: (1) creating a new Go DDD project from scratch, (2) adding a new bounded context/domain module, (3) defining entities, VOs, or repositories, (4) implementing CQRS handlers, (5) wiring fx modules, (6) writing proto/ConnectRPC APIs.

Use when a major project step has been completed and needs to be reviewed against the original plan and coding standards.

Use when designing database schemas, implementing repository patterns, writing optimized queries, managing migrations, or working with indexes and transactions for SQL/NoSQL databases.

Use when reviewing concrete backend implementation changes before merge or release for Design Realization and House-Style Conformance with accepted domain decisions, Tactical Design, and ddd-expert guidance.

Use when house-style backend coding must implement accepted Tactical Design, make an unambiguous mechanical change, or repair a Guard finding already covered by accepted authority.

Use when domain discovery must clarify a backend request before Tactical Design, either through scenario/lifecycle/rule analysis or language/authority/context-boundary analysis.

Use when a ddd-expert phase needs to inspect DDD artifacts or apply an already accepted artifact transaction; validates declared phase-operation compatibility, layout, templates, and model-design revisions without making domain or tactical decisions.

Use when Tactical Design must be created from accepted backend domain facts or an existing Tactical Design needs pre-code evaluation.

Use when a ddd-expert phase needs to inspect DDD artifacts or apply an already accepted artifact transaction; validates declared phase-operation compatibility, layout, templates, and model-design revisions without making domain or tactical decisions.

Use when explicitly maintaining Project Knowledge Base: user asks to ingest/refresh/repair memory, a task is at final handoff/commit/PR/merge, or the KB needs bootstrap or full-refresh

Use to health-check Project Knowledge Base without writing — reports stale references, shape violations, SSOT issues, retrieval cost, split candidates, and suggested ingest targets