ADR-0004 — Minimal runtime document

Status: Accepted (with a scoped deferral)

Context

The Cloud Run serving path must not drag in the build-time foundry, and should not carry more of AIR than execution needs.

Decision & current state

• Dependency boundary (done + enforced). @anvil/runtime and @anvil/mcp-runtime import only @anvil/air — never @anvil/compiler, @anvil/generators, or @anvil/harness. A boundary test (packages/cli/src/architecture.test.ts) fails the build if that edge ever appears, and asserts the same for the declared dependencies.
• Compiled projections (done). The generator emits operations.manifest.json, schemas.compiled.json, and errors.compiled.json — minimal projections with no descriptions, examples, or provenance — and only approved operations are compiled in.
• Deferred, honestly. buildMcpServer still binds the full AIR Operation type on the execute path. This is a type-shape coupling, not a dependency-graph leak (the serving packages already pull in nothing from the foundry). Trimming the bound Operation to a dedicated RuntimeOperation type is low residual value and is listed as a remaining risk rather than done with a fake seam.

Consequences

• Cold-start-sensitive imports on the serving path are already minimal and guarded by tests.
• The residual (full Operation shape at runtime) is documented, not hidden.