Two contracts, matched to their audience (see docs/design.md §6):

• asyncapi.yaml — client-facing WebSocket protocol, JSON messages spec'd in AsyncAPI 2.6. Message categories: narrative.*, map.*, roll.*, audio.*, character.*, safety.*, tool.*, system.* (design doc §5). First draft: a representative message or two per category, not an exhaustive enumeration — extend it as each message is actually implemented. Validate with npx @asyncapi/cli validate protocol/asyncapi.yaml.
• system_engine.proto — System Engine contract, gRPC/protobuf. ResolveCheck, ApplyEffect, GetCharacterSchema, GetCharacterStatus, ValidateCharacter, ToJson/FromJson, plus a StreamEvents server-streaming feed for the sidecar to relay OpenCombatEngine's internal combat events across the process boundary (design doc §6.1, §12).

generate.sh regenerates the Go client/server stubs for system_engine.proto directly into master/internal/systemenginepb/ — inside the Master module's own tree, not a repo-level gen/, because a Go module can't cleanly import generated code living outside its own directory tree without workspace/multi-module machinery this project doesn't need with only one Go consumer so far. If a second Go consumer shows up later, revisit this (a go.work workspace tying multiple modules together is the natural next step).

Requires on PATH: protoc, and the Go plugins (go install google.golang.org/protobuf/cmd/protoc-gen-go@latest and go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest, then make sure $(go env GOPATH)/bin is on PATH). Run it from the repo root:

./protocol/generate.sh

The well-known-types (google.protobuf.Struct, google.protobuf.Timestamp) this contract imports are vendored under third_party/ rather than requiring every contributor to install libprotobuf-dev — see that directory's README.

Generated *.pb.go files are gitignored (**/*.pb.go) — regenerate, don't commit. A future non-Go reference SDK (Python, per design doc §6) would get its own generation step and its own output location, following that language's own conventions rather than this one.