Protocol overview
Boundary statement
A protocol adapter changes a wire shape; it does not create a second runtime authority. Identity, effective configuration, provider/model routing, tool governance, execution, and runtime-owned outcomes remain inside UAR.
Diagram in words
UAR, OpenAI-compatible, and Anthropic-compatible HTTP requests enter adapters before calling shared runtime services. A transport-free embedded host calls those services directly. MCP connects external tools and context; A2A connects peer agents. Both still pass through host-owned identity and execution boundaries. Runtime execution emits normalized events that server adapters map to SSE forms, A2UI state, or an embedded host callback.
Choose an entrance
| Need | Entrance | Output | State ownership |
|---|---|---|---|
| UAR chat | POST /api/chat/completion | JSON or SSE | runtime session plus caller-carried session id |
| OpenAI-shaped chat | POST /v1/chat/completions | OpenAI JSON/chunks and documented UAR extensions | same runtime authority as UAR chat |
| Anthropic-shaped messages | POST /v1/messages | Anthropic message or event vocabulary | same provider/model router and runtime |
| Governed agent lifecycle | /api/uar/runs | resource responses and normalized run-event SSE | run manager, replay buffer, configured persistence |
| Tool/context federation | configured MCP servers and /mcp/uar | MCP messages and tool results | MCP registry plus trusted host |
| Peer-agent transport | A2A routes and optional gRPC | A2A tasks, messages, and artifacts | tenant-aware A2A stores |
| Declarative UI | A2UI run routes | validated surface state and actions | A2UI registry and realtime backbone |
| Embedded application | Rust in-process API | host callbacks and return values | embedding host plus shared runtime services |
Authority and compatibility
Compatibility applies to the implemented adapter, fields, and event forms. It
does not assert every upstream extension or transport is present. Provider
selection remains provider/model routing even when the client wire shape is
OpenAI- or Anthropic-compatible.
Resource APIs and live events have different authority. A database-backed resource can be reloaded after a process restart. A live event explains a transition but is not automatically durable history. Each protocol guide names its replay and retention boundary.
Profile limits
minimal and server-full contain the HTTP/SSE surface. server-full adds the
A2A transport and broader release feature set. embedded-mobile is
transport-free: the host supplies persistence and inference and consumes
in-process events. Evidence from one entrance or profile applies only to that
entrance and profile.
Next: HTTP compatibility.