Enum HookEvent 

#[non_exhaustive]
pub enum HookEvent<'a> {
    SessionStart {
        goal: &'a str,
    },
    PreToolCall {
        name: &'a str,
        args: &'a Value,
    },
    PostToolCall {
        name: &'a str,
        args: &'a Value,
        result: &'a str,
        duration_ms: u64,
    },
    PreCompact {
        transcript_len: usize,
    },
    PostCompact {
        removed: usize,
        summary_chars: usize,
    },
    SessionEnd {
        outcome: &'a AgentOutcome,
    },
}

Events emitted at lifecycle points during an agent run.

This enum is #[non_exhaustive] — new variants may be added in future releases without a breaking change.

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.

SessionStart

Fired at the start of Agent::run(), before any LLM call.

Fields

goal: &'a str

The goal text passed to Agent::run().

PreToolCall

Fired before a tool is dispatched (after the permission hook).

Fields

name: &'a str

Name of the tool about to be called.

args: &'a Value

Arguments that will be passed to the tool.

PostToolCall

Fired after a tool returns.

Fields

name: &'a str

Name of the tool that was called.

args: &'a Value

Arguments that were passed to the tool.

result: &'a str

The result string returned by the tool (or error message).

duration_ms: u64

Wall-clock duration of the tool execution in milliseconds.

PreCompact

Fired before compaction is attempted.

Fields

transcript_len: usize

Current transcript length in characters.

PostCompact

Fired after compaction completes.

Fields

removed: usize

Number of messages removed during compaction.

summary_chars: usize

Character count of the summary message added.

SessionEnd

Fired just before returning from Agent::run().

Fields

outcome: &'a AgentOutcome

The outcome that will be returned.

Trait Implementations

impl<'a> Clone for HookEvent<'a>

fn clone(&self) -> HookEvent<'a>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<'a> Debug for HookEvent<'a>

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

Formats the value using the given formatter.