engine-adapter-scaffold

Every engine gets one package: packages/mcp-<engine>, an MCP server speaking IR.

Layout to generate

packages/mcp-<engine>/
├── package.json          # name @openbench/mcp-<engine>, deps: @openbench/ir-schema, @modelcontextprotocol/sdk
├── tsconfig.json         # extends ../../tsconfig.base.json
├── src/
│   ├── index.ts          # public API: importNative, exportNative, validate (pure functions)
│   ├── server.ts         # MCP server registering the tools (thin wrapper over index.ts)
│   └── <engine>/         # engine-specific parsing/serialization
└── test/
    ├── contract.test.ts  # THE round-trip contract: import(export(doc)) toEqual doc
    └── fixtures/         # real native-format samples (checked in, small)

The standard tool contract (non-negotiable)

• import(nativeFormat) -> IR document(s) — never throws raw engine errors; returns structured { ok, documents | errors }.
• export(IR document) -> nativeFormat
• validate(IR document) -> { valid, errors: [{ path, message }] } — delegates to @openbench/ir-schema then adds engine-specific constraints.
• Every produced document is stamped provenance: { source: "mcp-<engine>", at: ISO }.

Order of work (TDD)

1. Red: contract.test.ts with a minimal fixture → commit.
2. Green: parser/serializer until round-trip holds.
3. Lossy fields discovered → document them in .context/engine-status.md (same PR; the reviewer gate enforces this for packages/mcp-* changes).
4. MCP server.ts last — it is a thin adapter over tested pure functions.
5. Update .context/engine-status.md status row + .context/architecture.md if the engine adds a new capability class.