Events and streaming

SSE streams provide live output. Durable events provide replay, resume, and recovery. WebSocket notifications tell clients when related state changed.

Live transport

Conversation streams return text/event-stream for AG-UI execution. Clients render text, tool calls, tool results, reasoning, and terminal state while the run is active.

Durable event log

The durable mirror converts stream chunks into persisted run events. Later reads can replay the event log or continue following a run. Veryfront uses the AG-UI events specification for streamed agent output.

SSE run stream

The durable run stream returns text/event-stream. It starts from the persisted event log. It accepts Last-Event-ID, emits heartbeats, and closes after a terminal run event.

AG-UI event reference

The public stream forwards these AG-UI event types.

Event	Family	Purpose
`RUN_STARTED`	Lifecycle	Run began
`RUN_FINISHED`	Lifecycle	Run completed successfully
`RUN_ERROR`	Lifecycle	Run failed or was cancelled
`TEXT_MESSAGE_START`	Text	Assistant message began
`TEXT_MESSAGE_CONTENT`	Text	Assistant text delta
`TEXT_MESSAGE_END`	Text	Assistant message ended
`TOOL_CALL_START`	Tool	Tool call began
`TOOL_CALL_ARGS`	Tool	Tool argument delta
`TOOL_CALL_CHUNK`	Tool	Tool-call chunk from compatible runtimes
`TOOL_CALL_END`	Tool	Tool call arguments ended
`TOOL_CALL_RESULT`	Tool	Tool result or tool error
`STATE_SNAPSHOT`	State	Full runtime state snapshot
`STATE_DELTA`	State	Incremental runtime state update
`MESSAGES_SNAPSHOT`	State	Full message snapshot
`REASONING_MESSAGE_START`	Reasoning	Public reasoning message began
`REASONING_MESSAGE_CONTENT`	Reasoning	Public reasoning message delta
`REASONING_MESSAGE_END`	Reasoning	Public reasoning message ended
`CUSTOM`	Custom	Named Veryfront extension event

Custom event names

CUSTOM events use a constrained public name set.

Name	Purpose
`message-metadata`	Message metadata attached to streamed output
`source-url`	URL citation or source reference
`source-document`	Document citation or source reference
`file`	File reference emitted by a run
`tool-call-status`	Tool execution status update
`stream-heartbeat`	Run stream heartbeat emitted during SSE follow

WebSocket notification events

WebSocket notifications are lightweight invalidation events. They do not carry AG-UI token deltas. Clients use project event notifications to refresh child-run and message data.

Event	Purpose
`message.created`	Conversation message created
`message.updated`	Conversation message changed
`message.status_changed`	Message status changed
`message.deleted`	Conversation message deleted
`agent_run.created`	Conversation-owned agent run created
`agent_run.updated`	Conversation-owned agent run changed
`participant.joined`	Participant joined a conversation
`participant.left`	Participant left a conversation
`conversation.updated`	Conversation metadata changed
`typing.start`	Participant started typing
`typing.stop`	Participant stopped typing

Getting Started

Concepts

Conversations API

Guides

Integrations

API Reference

REST API

GraphQL API

MCP API

Events and streaming

Live transport

Durable event log

SSE run stream

AG-UI event reference

Custom event names

WebSocket notification events

​Live transport

​Durable event log

​SSE run stream

​AG-UI event reference

​Custom event names

​WebSocket notification events

Live transport

Durable event log

SSE run stream

AG-UI event reference

Custom event names

WebSocket notification events