Module event 

The AG-UI event stream.

An agent run is a sequence of these events. Event is the closed union of all of them, tagged on the wire by a type field holding a SCREAMING_SNAKE_CASE name:

let event = Event::text_message_content("msg-1", "Hello");
assert_eq!(event.event_type(), EventType::TextMessageContent);
assert_eq!(
    serde_json::to_string(&event).unwrap(),
    r#"{"type":"TEXT_MESSAGE_CONTENT","messageId":"msg-1","delta":"Hello"}"#
);

Every event also carries the optional BaseEvent fields — a timestamp, the provider event it was translated from, and metadata — flattened into the same JSON object. Most events additionally accept an optional subagentRunId saying which subagent produced them; see subagent.

Re-exports

pub use activity::ActivityDeltaEvent;

pub use activity::ActivitySnapshotEvent;

pub use lifecycle::RunErrorEvent;

pub use lifecycle::RunFinishedEvent;

pub use lifecycle::RunStartedEvent;

pub use lifecycle::StepFinishedEvent;

pub use lifecycle::StepStartedEvent;

pub use reasoning::ReasoningEncryptedValueEvent;

pub use reasoning::ReasoningEncryptedValueSubtype;

pub use reasoning::ReasoningEndEvent;

pub use reasoning::ReasoningMessageChunkEvent;

pub use reasoning::ReasoningMessageContentEvent;

pub use reasoning::ReasoningMessageEndEvent;

pub use reasoning::ReasoningMessageStartEvent;

pub use reasoning::ReasoningRole;

pub use reasoning::ReasoningStartEvent;

pub use reasoning::ThinkingEndEvent;

pub use reasoning::ThinkingStartEvent;

pub use reasoning::ThinkingTextMessageContentEvent;

pub use reasoning::ThinkingTextMessageEndEvent;

pub use reasoning::ThinkingTextMessageStartEvent;

pub use special::CustomEvent;

pub use special::RawEvent;

pub use state::MessagesSnapshotEvent;

pub use state::StateDeltaEvent;

pub use state::StateSnapshotEvent;

pub use subagent::SubagentErrorEvent;

pub use subagent::SubagentFinishedEvent;

pub use subagent::SubagentOutcome;

pub use subagent::SubagentStartedEvent;

pub use text::TextMessageChunkEvent;

pub use text::TextMessageContentEvent;

pub use text::TextMessageEndEvent;

pub use text::TextMessageRole;

pub use text::TextMessageStartEvent;

pub use tool::ToolCallArgsEvent;

pub use tool::ToolCallChunkEvent;

pub use tool::ToolCallEndEvent;

pub use tool::ToolCallResultEvent;

pub use tool::ToolCallStartEvent;

pub use tool::ToolResultRole;

Modules

activity

Structured progress updates: ACTIVITY_SNAPSHOT, ACTIVITY_DELTA.

factories

Ergonomic constructors for every event type.

lifecycle

Run and step lifecycle: RUN_* and STEP_*.

reasoning

Model reasoning: REASONING_*, plus the deprecated THINKING_* events they replaced.

special

Escape hatches: RAW and CUSTOM.

state

Shared state and message-history snapshots: STATE_SNAPSHOT, STATE_DELTA, MESSAGES_SNAPSHOT.

subagent

Subagent lifecycle: SUBAGENT_STARTED, SUBAGENT_FINISHED, SUBAGENT_ERROR.

text

Streaming assistant text: TEXT_MESSAGE_*.

tool

Tool invocation: TOOL_CALL_*.

Structs

BaseEvent

The fields every event may carry, flattened into the event’s own JSON object rather than nested under a key.

Enums

Event

One event in an AG-UI stream.

EventType

The type discriminator of an Event, on its own.