> ## Documentation Index
> Fetch the complete documentation index at: https://docs.qredence.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Chat stream event (`ChatStreamEvent`)

> Event protocol for streaming agent turns (packages/agent/src/types.ts). Types: start (partial AssistantMessage), text_start/delta/end, thinking_start/delta/end,...

Event protocol for streaming agent turns (`packages/agent/src/types.ts`). Types: `start` (partial `AssistantMessage`), `text_start`/`delta`/`end`, `thinking_start`/`delta`/`end`, `toolcall_start`/`delta`/`end`, `done` (`AssistantMessage` with `stopReason`), `error` (`stopReason` "error"/"aborted" + `errorMessage`). Stream functions (`streamSimple`, provider-specific `stream<Provider>()`) must return `AssistantMessageEventStream` and encode errors in events, not throw.

Related: [Agent message](/fleet-prime-agent/primitives--agent-message), [Streaming chat](/fleet-prime-agent/guides/streaming-chat)