Architecture-Design Companion

Why this loads automatically

This is a companion gate. Implementation skills (t3:code, t3:ticket for new features, t3:retro when a retro touches skills) declare requires: [architecture-design] so it loads BEFORE coding starts. The flywheel (BLUEPRINT § 17.1 invariant 2) is enforcement encoded as structure, not prose vigilance — this companion is the structure for the "design first, then code" step.

Generic planning methodology is delegated to obra/superpowers/writing-plans. The teatree-specific value-add is the ten-check architecture pass below, plus the template the implementer fills in before touching src/ — worktree-local as ARCHITECTURE.md (gitignored scratch) and surfaced to the reviewer as a ## Architecture pre-check section in the PR body.

Scope, and the OPTIONAL vendor architecture skill

This skill is scoped to THIS repo's conventions — BLUEPRINT alignment, FSM phase boundaries, extension-point contracts, dependency direction. It answers "does this change fit teatree's architecture", not "how do you structure agent work at all".

The layer beneath that — provider-level agent-architecture decision-trees (single call vs workflow vs agent, tool-surface orchestration, agent tiering, resiliency patterns) — is covered by the agent-platform vendor's claude-api skill. That skill is Anthropic-specific: its guidance is load-bearing on Claude/Anthropic API primitives (adaptive thinking, effort, programmatic tool calling, context editing, prompt-caching breakpoints, the Managed Agents API), and its own frontmatter directs the reader to SKIP it for non-Claude providers. So teatree does not install it by default — it is an OPTIONAL recommendation (t3 doctor check surfaces it as an INFO when absent) that an operator running on Claude may install with apm install anthropics/skills/skills/claude-api#<pin>. There is no scope overlap to reconcile: local = repo conventions; vendor = provider-level agent architecture. The recommendation datum (source pin, caveat, boundary) lives in src/teatree/provisioning/recommended.py.

When the gate fires

The ten checks apply when the work meets any of: