Enum Event 

pub enum Event {
    Init {
        model: String,
        tools: Vec<String>,
        working_directory: Option<String>,
        metadata: HashMap<String, Value>,
    },
    UserMessage {
        content: Vec<ContentBlock>,
    },
    AssistantMessage {
        content: Vec<ContentBlock>,
        usage: Option<Usage>,
        parent_tool_use_id: Option<String>,
    },
    ToolExecution {
        tool_name: String,
        tool_id: String,
        input: Value,
        result: ToolResult,
        parent_tool_use_id: Option<String>,
    },
    TurnComplete {
        stop_reason: Option<String>,
        turn_index: u32,
        usage: Option<Usage>,
    },
    Result {
        success: bool,
        message: Option<String>,
        duration_ms: Option<u64>,
        num_turns: Option<u32>,
    },
    Error {
        message: String,
        details: Option<Value>,
    },
    PermissionRequest {
        tool_name: String,
        description: String,
        granted: bool,
    },
}

A single event in an agent session.

Events represent discrete steps in the conversation flow, such as initialization, messages, tool calls, and results.

Variants

Init

Session initialization event

Fields

model: String

tools: Vec<String>

working_directory: Option<String>

metadata: HashMap<String, Value>

UserMessage

Message from the user (replayed via –replay-user-messages)

Fields

content: Vec<ContentBlock>

AssistantMessage

Message from the assistant

Fields

content: Vec<ContentBlock>

usage: Option<Usage>

parent_tool_use_id: Option<String>

If this message comes from a sub-agent, the tool_use_id of the parent Agent tool call that spawned it.

ToolExecution

Tool execution event

Fields

tool_name: String

tool_id: String

input: Value

result: ToolResult

parent_tool_use_id: Option<String>

If this execution belongs to a sub-agent, the tool_use_id of the parent Agent tool call that spawned it.

TurnComplete

End of a single assistant turn.

In bidirectional streaming mode, this fires exactly once per turn, after the final Event::AssistantMessage / Event::ToolExecution of the turn and immediately before the per-turn Event::Result. Prefer this over Result as the turn-boundary signal in new code.

For providers that don’t expose a bidirectional streaming session (currently everything except Claude), this event is not emitted.

Fields

stop_reason: Option<String>

Reason the turn stopped, as reported by the provider.

For Claude, well-known values are end_turn, tool_use, max_tokens, and stop_sequence. None when the provider didn’t surface a stop reason (for example, interrupted turns or providers that don’t report one).

turn_index: u32

Zero-based monotonic turn index within the streaming session.

usage: Option<Usage>

Usage reported for the final assistant message of this turn.

Result

Session-final or per-turn result summary from the provider.

In bidirectional streaming mode this fires after Event::TurnComplete at the end of every turn. In batch mode it fires once when the provider reports the session-final result.

Fields

success: bool

message: Option<String>

duration_ms: Option<u64>

num_turns: Option<u32>

Error

An error occurred

Fields

message: String

details: Option<Value>

PermissionRequest

Permission was requested

Fields

tool_name: String

description: String

granted: bool

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 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 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.