Enum Event 

pub enum Event {
    TextMessageStart(TextMessageStartEvent),
    TextMessageContent(TextMessageContentEvent),
    TextMessageEnd(TextMessageEndEvent),
    TextMessageChunk(TextMessageChunkEvent),
    ToolCallStart(ToolCallStartEvent),
    ToolCallArgs(ToolCallArgsEvent),
    ToolCallEnd(ToolCallEndEvent),
    ToolCallChunk(ToolCallChunkEvent),
    ToolCallResult(ToolCallResultEvent),
    ThinkingStart(ThinkingStartEvent),
    ThinkingEnd(ThinkingEndEvent),
    ThinkingTextMessageStart(ThinkingTextMessageStartEvent),
    ThinkingTextMessageContent(ThinkingTextMessageContentEvent),
    ThinkingTextMessageEnd(ThinkingTextMessageEndEvent),
    StateSnapshot(StateSnapshotEvent),
    StateDelta(StateDeltaEvent),
    MessagesSnapshot(MessagesSnapshotEvent),
    ActivitySnapshot(ActivitySnapshotEvent),
    ActivityDelta(ActivityDeltaEvent),
    Raw(RawEvent),
    Custom(CustomEvent),
    RunStarted(RunStartedEvent),
    RunFinished(RunFinishedEvent),
    RunError(RunErrorEvent),
    StepStarted(StepStartedEvent),
    StepFinished(StepFinishedEvent),
    ReasoningStart(ReasoningStartEvent),
    ReasoningMessageStart(ReasoningMessageStartEvent),
    ReasoningMessageContent(ReasoningMessageContentEvent),
    ReasoningMessageEnd(ReasoningMessageEndEvent),
    ReasoningMessageChunk(ReasoningMessageChunkEvent),
    ReasoningEnd(ReasoningEndEvent),
    ReasoningEncryptedValue(ReasoningEncryptedValueEvent),
    SubagentStarted(SubagentStartedEvent),
    SubagentFinished(SubagentFinishedEvent),
    SubagentError(SubagentErrorEvent),
}

One event in an AG-UI stream.

Serializes as the payload’s fields plus a type discriminator, so there is no nesting on the wire.

Exhaustive on purpose

This enum is deliberately not #[non_exhaustive], unlike every error type in this workspace. A new protocol event should be a compile error where you match on events: that is what a typed SDK buys you over serde_json::Value, and the alternative — a _ arm in every consumer — is exactly how the previous Rust SDK came to be missing eight event types without anyone noticing.

The consequence is that adding an event is a major version of this crate. That is the intended price; see docs/DESIGN.md.

Variants

TextMessageStart(TextMessageStartEvent)

Opens a text message. See TextMessageStartEvent.

TextMessageContent(TextMessageContentEvent)

Appends to a text message. See TextMessageContentEvent.

TextMessageEnd(TextMessageEndEvent)

Closes a text message. See TextMessageEndEvent.

TextMessageChunk(TextMessageChunkEvent)

A whole text update in one event. See TextMessageChunkEvent.

ToolCallStart(ToolCallStartEvent)

Opens a tool call. See ToolCallStartEvent.

ToolCallArgs(ToolCallArgsEvent)

Appends tool-call arguments. See ToolCallArgsEvent.

ToolCallEnd(ToolCallEndEvent)

Closes a tool call. See ToolCallEndEvent.

ToolCallChunk(ToolCallChunkEvent)

A whole tool call in one event. See ToolCallChunkEvent.

ToolCallResult(ToolCallResultEvent)

A tool call’s result. See ToolCallResultEvent.

ThinkingStart(ThinkingStartEvent)

Opens a thinking block. See ThinkingStartEvent.

ThinkingEnd(ThinkingEndEvent)

Closes a thinking block. See ThinkingEndEvent.

ThinkingTextMessageStart(ThinkingTextMessageStartEvent)

Opens a thinking message. See ThinkingTextMessageStartEvent.

ThinkingTextMessageContent(ThinkingTextMessageContentEvent)

Appends thinking text. See ThinkingTextMessageContentEvent.

ThinkingTextMessageEnd(ThinkingTextMessageEndEvent)

Closes a thinking message. See ThinkingTextMessageEndEvent.

StateSnapshot(StateSnapshotEvent)

Replaces the shared state. See StateSnapshotEvent.

StateDelta(StateDeltaEvent)

Patches the shared state. See StateDeltaEvent.

MessagesSnapshot(MessagesSnapshotEvent)

Replaces the message history. See MessagesSnapshotEvent.

ActivitySnapshot(ActivitySnapshotEvent)

Publishes an activity. See ActivitySnapshotEvent.

ActivityDelta(ActivityDeltaEvent)

Patches an activity. See ActivityDeltaEvent.

Raw(RawEvent)

Forwards a provider event. See RawEvent.

Custom(CustomEvent)

An application-defined event. See CustomEvent.

RunStarted(RunStartedEvent)

Starts a run. See RunStartedEvent.

RunFinished(RunFinishedEvent)

Finishes or pauses a run. See RunFinishedEvent.

RunError(RunErrorEvent)

Fails a run. See RunErrorEvent.

StepStarted(StepStartedEvent)

Starts a step. See StepStartedEvent.

StepFinished(StepFinishedEvent)

Finishes a step. See StepFinishedEvent.

ReasoningStart(ReasoningStartEvent)

Opens a reasoning block. See ReasoningStartEvent.

ReasoningMessageStart(ReasoningMessageStartEvent)

Opens a reasoning message. See ReasoningMessageStartEvent.

ReasoningMessageContent(ReasoningMessageContentEvent)

Appends reasoning text. See ReasoningMessageContentEvent.

ReasoningMessageEnd(ReasoningMessageEndEvent)

Closes a reasoning message. See ReasoningMessageEndEvent.

ReasoningMessageChunk(ReasoningMessageChunkEvent)

A whole reasoning update in one event. See ReasoningMessageChunkEvent.

ReasoningEnd(ReasoningEndEvent)

Closes a reasoning block. See ReasoningEndEvent.

ReasoningEncryptedValue(ReasoningEncryptedValueEvent)

Carries an encrypted reasoning blob. See ReasoningEncryptedValueEvent.

SubagentStarted(SubagentStartedEvent)

Announces a subagent invocation. See SubagentStartedEvent.

SubagentFinished(SubagentFinishedEvent)

Closes a subagent invocation. See SubagentFinishedEvent.

SubagentError(SubagentErrorEvent)

Fails a subagent invocation. See SubagentErrorEvent.

Implementations

impl Event

pub fn text_message_start( message_id: impl Into<MessageId>, role: TextMessageRole, ) -> Self

TEXT_MESSAGE_START — opens a text message.

pub fn text_message_content( message_id: impl Into<MessageId>, delta: impl Into<String>, ) -> Self

TEXT_MESSAGE_CONTENT — appends text to an open message.

pub fn text_message_end(message_id: impl Into<MessageId>) -> Self

TEXT_MESSAGE_END — closes a text message.

pub fn text_message_chunk( message_id: Option<MessageId>, delta: Option<String>, ) -> Self

TEXT_MESSAGE_CHUNK — a whole text update in one event.

pub fn tool_call_start( tool_call_id: impl Into<ToolCallId>, tool_call_name: impl Into<String>, ) -> Self

TOOL_CALL_START — opens a tool call.

pub fn tool_call_args( tool_call_id: impl Into<ToolCallId>, delta: impl Into<String>, ) -> Self

TOOL_CALL_ARGS — appends argument JSON to an open call.

pub fn tool_call_end(tool_call_id: impl Into<ToolCallId>) -> Self

TOOL_CALL_END — closes a tool call.

pub fn tool_call_chunk( tool_call_id: Option<ToolCallId>, tool_call_name: Option<String>, delta: Option<String>, ) -> Self

TOOL_CALL_CHUNK — a whole tool call in one event.

pub fn tool_call_result( message_id: impl Into<MessageId>, tool_call_id: impl Into<ToolCallId>, content: impl Into<String>, ) -> Self

TOOL_CALL_RESULT — reports what a tool returned.

pub fn thinking_start(title: Option<String>) -> Self

👎Deprecated:

use Event::reasoning_start

THINKING_START — opens a thinking block.

pub fn thinking_end() -> Self

👎Deprecated:

use Event::reasoning_end

THINKING_END — closes a thinking block.

pub fn thinking_text_message_start() -> Self

👎Deprecated:

use Event::reasoning_message_start

THINKING_TEXT_MESSAGE_START — opens a thinking message.

pub fn thinking_text_message_content(delta: impl Into<String>) -> Self

👎Deprecated:

use Event::reasoning_message_content

THINKING_TEXT_MESSAGE_CONTENT — appends thinking text.

pub fn thinking_text_message_end() -> Self

👎Deprecated:

use Event::reasoning_message_end

THINKING_TEXT_MESSAGE_END — closes a thinking message.

pub fn state_snapshot(snapshot: impl Into<Value>) -> Self

STATE_SNAPSHOT — replaces the shared state.

pub fn state_delta(delta: impl Into<Vec<PatchOperation>>) -> Self

STATE_DELTA — patches the shared state.

pub fn messages_snapshot(messages: impl Into<Vec<Message>>) -> Self

MESSAGES_SNAPSHOT — replaces the message history.

pub fn activity_snapshot( message_id: impl Into<MessageId>, activity_type: impl Into<String>, content: JsonObject, ) -> Self

ACTIVITY_SNAPSHOT — publishes an activity payload.

pub fn activity_delta( message_id: impl Into<MessageId>, activity_type: impl Into<String>, patch: impl Into<Vec<PatchOperation>>, ) -> Self

ACTIVITY_DELTA — patches an activity payload.

pub fn raw(event: impl Into<Value>) -> Self

RAW — forwards a provider event verbatim.

pub fn custom(name: impl Into<String>, value: impl Into<Value>) -> Self

CUSTOM — an application-defined event.

pub fn run_started( thread_id: impl Into<ThreadId>, run_id: impl Into<RunId>, ) -> Self

RUN_STARTED — starts a run.

pub fn run_finished( thread_id: impl Into<ThreadId>, run_id: impl Into<RunId>, ) -> Self

RUN_FINISHED without an outcome — the legacy shape, which consumers read as success.

pub fn run_finished_success( thread_id: impl Into<ThreadId>, run_id: impl Into<RunId>, ) -> Self

RUN_FINISHED with an explicit success outcome.

pub fn run_finished_interrupt( thread_id: impl Into<ThreadId>, run_id: impl Into<RunId>, interrupts: impl Into<Vec<Interrupt>>, ) -> Self

RUN_FINISHED with an interrupt outcome — the run is paused until the client answers.

pub fn run_error(message: impl Into<String>) -> Self

RUN_ERROR — fails the run.

pub fn step_started(step_name: impl Into<StepName>) -> Self

STEP_STARTED — opens a named step.

pub fn step_finished(step_name: impl Into<StepName>) -> Self

STEP_FINISHED — closes a named step.

pub fn reasoning_start(message_id: impl Into<MessageId>) -> Self

REASONING_START — opens a reasoning block.

pub fn reasoning_message_start(message_id: impl Into<MessageId>) -> Self

REASONING_MESSAGE_START — opens a reasoning message.

pub fn reasoning_message_content( message_id: impl Into<MessageId>, delta: impl Into<String>, ) -> Self

REASONING_MESSAGE_CONTENT — appends reasoning text.

pub fn reasoning_message_end(message_id: impl Into<MessageId>) -> Self

REASONING_MESSAGE_END — closes a reasoning message.

pub fn reasoning_message_chunk( message_id: Option<MessageId>, delta: Option<String>, ) -> Self

REASONING_MESSAGE_CHUNK — a whole reasoning update in one event.

pub fn reasoning_end(message_id: impl Into<MessageId>) -> Self

REASONING_END — closes a reasoning block.

pub fn reasoning_encrypted_value( subtype: ReasoningEncryptedValueSubtype, entity_id: impl Into<String>, encrypted_value: impl Into<String>, ) -> Self

REASONING_ENCRYPTED_VALUE — carries an opaque reasoning blob.

pub fn subagent_started( subagent_run_id: impl Into<SubagentRunId>, name: impl Into<String>, ) -> Self

SUBAGENT_STARTED — announces a subagent invocation.

pub fn subagent_finished(subagent_run_id: impl Into<SubagentRunId>) -> Self

SUBAGENT_FINISHED without an outcome — the legacy shape, which consumers read as success.

pub fn subagent_finished_success( subagent_run_id: impl Into<SubagentRunId>, ) -> Self

SUBAGENT_FINISHED with an explicit success outcome.

pub fn subagent_finished_suspended( subagent_run_id: impl Into<SubagentRunId>, interrupt_ids: impl Into<Vec<String>>, ) -> Self

SUBAGENT_FINISHED with a suspended outcome — the subagent is waiting on the named interrupts.

pub fn subagent_error( subagent_run_id: impl Into<SubagentRunId>, message: impl Into<String>, ) -> Self

SUBAGENT_ERROR — fails a subagent invocation.

impl Event

pub const fn event_type(&self) -> EventType

The discriminator for this event.

pub const fn base(&self) -> &BaseEvent

The timestamp and raw-event fields, whatever the variant.

pub const fn base_mut(&mut self) -> &mut BaseEvent

Mutable access to the timestamp and raw-event fields.

impl Event

pub fn with_timestamp(self, timestamp: i64) -> Self

Stamps the event with a millisecond Unix timestamp.

pub fn with_raw_event(self, raw_event: impl Into<Value>) -> Self

Attaches the provider event this was translated from.

pub fn with_metadata(self, metadata: JsonObject) -> Self

Attaches metadata, replacing any the event already carried. See crate::metadata.

pub const fn metadata(&self) -> Option<&JsonObject>

The event’s metadata, if it carries any.

pub const fn is_deprecated(&self) -> bool

Whether this event’s type is deprecated in favour of a REASONING_* one.

pub fn subagent_run_id(&self) -> Option<&SubagentRunId>

The subagent this event belongs to.

None means the parent agent — or an event type that carries no attribution at all; EventType::is_attributable tells the two apart. For the three SUBAGENT_* lifecycle events this is the subagent they announce, which is required rather than optional.

pub fn set_subagent_run_id(&mut self, id: impl Into<SubagentRunId>) -> bool

Attributes the event to id.

Returns false, leaving the event untouched, for the nine event types the protocol defines without the field: RUN_*, MESSAGES_SNAPSHOT and the deprecated THINKING_* family. On a SUBAGENT_* event it sets the subject.

pub fn clear_subagent_run_id(&mut self) -> Option<SubagentRunId>

Removes attribution from an attributable event and returns it.

The SUBAGENT_* events carry their id as a required subject, so this leaves them alone and returns None, as it does for the event types that never carry the field.

pub fn with_subagent_run_id(self, id: impl Into<SubagentRunId>) -> Self

Builder form of set_subagent_run_id; a no-op on the event types that cannot carry attribution.

Trait Implementations

impl Clone for Event

fn clone(&self) -> Event

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl ComposeSchema for Event

fn compose(generics: Vec<RefOr<Schema>>) -> RefOr<Schema>

impl Debug for Event

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Event

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<ActivityDeltaEvent> for Event

fn from(payload: ActivityDeltaEvent) -> Self

Converts to this type from the input type.

impl From<ActivitySnapshotEvent> for Event

fn from(payload: ActivitySnapshotEvent) -> Self

Converts to this type from the input type.

impl From<CustomEvent> for Event

fn from(payload: CustomEvent) -> Self

Converts to this type from the input type.

impl From<MessagesSnapshotEvent> for Event

fn from(payload: MessagesSnapshotEvent) -> Self

Converts to this type from the input type.

impl From<RawEvent> for Event

fn from(payload: RawEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningEncryptedValueEvent> for Event

fn from(payload: ReasoningEncryptedValueEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningEndEvent> for Event

fn from(payload: ReasoningEndEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningMessageChunkEvent> for Event

fn from(payload: ReasoningMessageChunkEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningMessageContentEvent> for Event

fn from(payload: ReasoningMessageContentEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningMessageEndEvent> for Event

fn from(payload: ReasoningMessageEndEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningMessageStartEvent> for Event

fn from(payload: ReasoningMessageStartEvent) -> Self

Converts to this type from the input type.

impl From<ReasoningStartEvent> for Event

fn from(payload: ReasoningStartEvent) -> Self

Converts to this type from the input type.

impl From<RunErrorEvent> for Event

fn from(payload: RunErrorEvent) -> Self

Converts to this type from the input type.

impl From<RunFinishedEvent> for Event

fn from(payload: RunFinishedEvent) -> Self

Converts to this type from the input type.

impl From<RunStartedEvent> for Event

fn from(payload: RunStartedEvent) -> Self

Converts to this type from the input type.

impl From<StateDeltaEvent> for Event

fn from(payload: StateDeltaEvent) -> Self

Converts to this type from the input type.

impl From<StateSnapshotEvent> for Event

fn from(payload: StateSnapshotEvent) -> Self

Converts to this type from the input type.

impl From<StepFinishedEvent> for Event

fn from(payload: StepFinishedEvent) -> Self

Converts to this type from the input type.

impl From<StepStartedEvent> for Event

fn from(payload: StepStartedEvent) -> Self

Converts to this type from the input type.

impl From<SubagentErrorEvent> for Event

fn from(payload: SubagentErrorEvent) -> Self

Converts to this type from the input type.

impl From<SubagentFinishedEvent> for Event

fn from(payload: SubagentFinishedEvent) -> Self

Converts to this type from the input type.

impl From<SubagentStartedEvent> for Event

fn from(payload: SubagentStartedEvent) -> Self

Converts to this type from the input type.

impl From<TextMessageChunkEvent> for Event

fn from(payload: TextMessageChunkEvent) -> Self

Converts to this type from the input type.

impl From<TextMessageContentEvent> for Event

fn from(payload: TextMessageContentEvent) -> Self

Converts to this type from the input type.

impl From<TextMessageEndEvent> for Event

fn from(payload: TextMessageEndEvent) -> Self

Converts to this type from the input type.

impl From<TextMessageStartEvent> for Event

fn from(payload: TextMessageStartEvent) -> Self

Converts to this type from the input type.

impl From<ThinkingEndEvent> for Event

fn from(payload: ThinkingEndEvent) -> Self

Converts to this type from the input type.

impl From<ThinkingStartEvent> for Event

fn from(payload: ThinkingStartEvent) -> Self

Converts to this type from the input type.

impl From<ThinkingTextMessageContentEvent> for Event

fn from(payload: ThinkingTextMessageContentEvent) -> Self

Converts to this type from the input type.

impl From<ThinkingTextMessageEndEvent> for Event

fn from(payload: ThinkingTextMessageEndEvent) -> Self

Converts to this type from the input type.

impl From<ThinkingTextMessageStartEvent> for Event

fn from(payload: ThinkingTextMessageStartEvent) -> Self

Converts to this type from the input type.

impl From<ToolCallArgsEvent> for Event

fn from(payload: ToolCallArgsEvent) -> Self

Converts to this type from the input type.

impl From<ToolCallChunkEvent> for Event

fn from(payload: ToolCallChunkEvent) -> Self

Converts to this type from the input type.

impl From<ToolCallEndEvent> for Event

fn from(payload: ToolCallEndEvent) -> Self

Converts to this type from the input type.

impl From<ToolCallResultEvent> for Event

fn from(payload: ToolCallResultEvent) -> Self

Converts to this type from the input type.

impl From<ToolCallStartEvent> for Event

fn from(payload: ToolCallStartEvent) -> Self

Converts to this type from the input type.

impl JsonSchema for Event

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for Event

fn eq(&self, other: &Event) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Event

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Event

impl ToSchema for Event

fn name() -> Cow<'static, str>

Return name of the schema.

fn schemas(schemas: &mut Vec<(String, RefOr<Schema>)>)

Implement reference [utoipa::openapi::schema::Schema]s for this type.