Enum AgentEvent 

#[non_exhaustive]
pub enum AgentEvent {
    AgentStart,
    AgentEnd {
        messages: Vec<Message>,
    },
    TurnStart,
    TurnEnd {
        message: Message,
        tool_results: Vec<ToolResult>,
    },
    MessageStart {
        message: Message,
    },
    MessageDelta {
        delta: String,
        tokens_generated: u32,
        tokens_per_sec: f64,
    },
    MessageEnd {
        message: Message,
    },
    GenerationStats {
        tokens_generated: u32,
        prompt_tokens: u32,
        tokens_per_sec: f64,
        time_to_first_token_ms: f64,
        generation_time_ms: f64,
    },
    ToolExecStart {
        tool_call_id: String,
        tool_name: String,
        args: Value,
    },
    ToolExecUpdate {
        tool_call_id: String,
        tool_name: String,
        partial: String,
    },
    ToolExecEnd {
        tool_call_id: String,
        tool_name: String,
        result: ToolResult,
    },
    ContextBudget {
        used_tokens: u32,
        max_tokens: u32,
        messages_in_context: u32,
        messages_pruned: u32,
    },
    Warning {
        message: String,
    },
    Error {
        message: String,
    },
}

Events emitted by the agent loop. Mirrors pi-agent-core’s event system for UI reactivity.

This enum is #[non_exhaustive]: match it with a wildcard arm, as new event variants may be added in a minor release.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

AgentStart

Agent begins processing a prompt.

AgentEnd

Agent finished all processing.

Fields

messages: Vec<Message>

All messages produced during this prompt() call.

TurnStart

A new turn begins (one LLM call + any tool executions).

TurnEnd

A turn completed.

Fields

message: Message

The assistant message produced by the turn.

tool_results: Vec<ToolResult>

Results of any tools the turn executed.

MessageStart

A message was added (user, assistant, or tool_result).

Fields

message: Message

The message that was added.

MessageDelta

Streaming delta for the current assistant message.

Fields

delta: String

The new token/chunk of text.

tokens_generated: u32

Tokens generated so far in this response.

tokens_per_sec: f64

Current generation speed.

MessageEnd

A message is complete.

Fields

message: Message

The completed message.

GenerationStats

Final timing statistics for a completed generation. Emitted once per successful response so the UI / observability layer can record the real time-to-first-token and generation time (not approximated from tps).

Fields

tokens_generated: u32

Tokens generated in the response.

prompt_tokens: u32

Tokens in the formatted prompt.

tokens_per_sec: f64

Average generation speed in tokens per second.

time_to_first_token_ms: f64

Time to the first emitted token, in milliseconds.

generation_time_ms: f64

Total generation time, in milliseconds.

ToolExecStart

A tool execution started.

Fields

tool_call_id: String

Id of the tool call being executed.

tool_name: String

Name of the tool being executed.

args: Value

Arguments passed to the tool.

ToolExecUpdate

Streaming progress from a tool execution.

Fields

tool_call_id: String

Id of the tool call reporting progress.

tool_name: String

Name of the tool reporting progress.

partial: String

Partial output emitted so far.

ToolExecEnd

A tool execution completed.

Fields

tool_call_id: String

Id of the completed tool call.

tool_name: String

Name of the completed tool.

result: ToolResult

The tool’s result.

ContextBudget

Context budget info after formatting.

Fields

used_tokens: u32

Tokens used by the prepared prompt.

max_tokens: u32

Maximum context tokens available.

messages_in_context: u32

Number of messages kept in the prompt.

messages_pruned: u32

Number of messages pruned to fit.

Warning

Non-fatal warning during processing.

Fields

message: String

Human-readable warning text.

Error

Fatal error that stopped processing.

Fields

message: String

Human-readable error text.

Trait Implementations

impl Clone for AgentEvent

fn clone(&self) -> AgentEvent

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for AgentEvent

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for AgentEvent

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for AgentEvent

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

where __S: Serializer,

Serialize this value into the given Serde serializer.