The LLM seam and its provider adapters. The `llm` package owns both the Service Definition and Consumer roles: the abstract service, content-block vocabulary, and stream-chunk assembler. Provider adapters register on `ctx.llm`. All **product** packages.
Adapters register provider routes on the seam; retry and token measurement remain separate consumers. The child READMEs own routing, metadata, replay, and provider-wire details; the [LLM architecture decisions](../../.agents/notes/implemented/architecture/2026-06-13-twin-llm-adapters.md) own the rationale.
The subsystem reference — messages and blocks, the model request, the `StreamChunk` protocol, the adapter contract — is [docs/subsystems/llm-streaming.md](../../docs/subsystems/llm-streaming.md) (token measurement: [token-meter.md](../../docs/subsystems/token-meter.md)); see the [twin adapters](../../.agents/notes/implemented/architecture/2026-06-13-twin-llm-adapters.md), [replay token meter](../../.agents/notes/implemented/architecture/2026-07-15-replay-token-meter-service.md), and [routed model context](../../.agents/notes/implemented/architecture/2026-07-20-routed-model-context-and-compaction-policy.md) Agent Notes.