python-architecture

# Python Architecture Skill [Python architect persona](../../agents/python-architect.agent.md) ## When to activate - Creating new Python modules or packages under `src/apm_cli/` - Refactoring class hierarchies or introducing base classes - Changes that touch 3+ files with shared logic patterns - Introducing new design patterns (Strategy, Observer, etc.) - Cross-cutting concerns (logging, auth, error handling) - Performance-sensitive paths (parallel downloads, large manifests) ## Key rules - Follow existing patterns (BaseIntegrator, CommandLogger, AuthResolver) before inventing new ones - Prefer composition over deep inheritance - Push shared logic into base classes, not duplicated across siblings - One canonical owner per decision: route through the existing authority (target_catalog, AuthResolver/host_providers, runtime registry, CommandLogger, CompiledOutputWriter, deployment_ledger, install-outcome, neutral hook IR, BaseIntegrator); extend it, never fork it. Full rule: `.apm/instructions/architecture.instructions.md` - Lock every centralization with a dual guardrail: a regression test plus a static check in `scripts/lint-architecture-boundaries.sh`