cf-chat-engine

The Chat Engine gear: multi-tenant conversational infrastructure with a plugin-driven backend.

Chat Engine owns session state, the immutable message tree, streaming, and routing — but zero business logic. All message processing (response generation, summarization, etc.) is delegated to backend plugins that implement the ChatEngineBackendPlugin trait from cf-chat-engine-sdk.

What this crate provides

• ChatEngineModule — the #[toolkit::gear(...)]-annotated entrypoint registered with the platform (capabilities: db, rest, stateful). It wires config, SeaORM repositories, the plugin ClientHub, domain services, and the REST router, then runs the retention-cleanup background task for the lifetime of the gear.
• Two first-party reference plugins, registered by default under ChatEngineBackendPlugin:
  • infra::llm_gateway::LlmGatewayPlugin — integrates with the internal LLM Gateway service.
  • infra::webhook_compat::WebhookCompatPlugin — forwards events to legacy HTTP webhook backends.

Module layout

• api — REST surface (routes, request/response DTOs) mounted onto the gear's Router.
• config — gear configuration, validated on load.
• domain — sessions, messages, reactions, variants, retention policy, and the domain services that implement the business rules Chat Engine itself owns (as opposed to plugin-owned response generation).
• infra — SeaORM repositories, the leader-election gate for the retention sweep, and the first-party plugin implementations above.

api, config, domain, and infra are pub (integration tests in tests/ reach into them) but marked #[doc(hidden)] so they don't pollute the public docs surface — chat_engine_sdk's re-exported types plus ChatEngineModule are the intended public API.

Relationship to cf-chat-engine-sdk

cf-chat-engine-sdk is the stable contract plugin authors compile against (traits, shared models, error types). This crate is the runtime that consumes that contract: it owns persistence, HTTP, streaming, and multi-tenancy, and calls into plugins for anything that requires backend-specific logic.

License

Same as the parent workspace.