MessageId

MessageId = Brand<string, "MessageId">

Defined in: packages/protocol/src/lib/message.ts:18

Opaque identifier for messages sent to the engine.

Every EngineMessage variant carries one. Used for:

1. Correlation — EngineOutput echoes the input id, so callers can match responses to requests without external bookkeeping.
2. Deduplication — HistoryManager skips duplicate entries when the same MessageId arrives twice in the same session for an assistant_message variant.
3. Audit and trace — log lines and history entries are keyed by MessageId, enabling end-to-end request correlation.