Enum Event 

pub enum Event {
    AgentStart,
    ContextUsage {
        used_tokens: usize,
        context_window: usize,
        auto_compact_at: usize,
    },
    Usage {
        model: String,
        usage: TokenUsage,
        estimated: bool,
    },
    CompactionStart {
        reason: String,
        before_tokens: usize,
    },
    CompactionEnd {
        reason: String,
        result: CompactionResult,
    },
    SkillActivated {
        id: String,
        name: String,
    },
    ToolSource {
        tool: String,
        source: ToolSource,
    },
    TurnStart {
        turn: usize,
    },
    MessageStart {
        role: Role,
    },
    MessageDelta {
        delta: String,
    },
    MessageEnd {
        role: Role,
        content: String,
    },
    ToolCall(ToolCall),
    ApprovalRequired(ApprovalRequest),
    PlanProposed(PlanProposal),
    PlanDecided {
        decision: PlanDecision,
    },
    GuardrailWarning {
        tool: String,
        reason: String,
    },
    GuardrailStop {
        tool: String,
        reason: String,
    },
    SelfHealing {
        attempt: u8,
        max_attempts: u8,
        errors: Vec<String>,
    },
    ToolExecutionStart(ToolCall),
    ToolExecutionEnd(ToolResult),
    TodoUpdated {
        todos: TodoState,
    },
    TurnEnd {
        turn: usize,
    },
    TurnEnded {
        turn: usize,
        metadata: TurnEndMetadata,
    },
    CacheAudit(CacheAudit),
    GateResult(GateResult),
    MemoryRecalled {
        recalls: Vec<MemoryRecall>,
    },
    AgentEnd,
    Error(String),
    BudgetExceeded {
        reason: String,
    },
    RetryReason {
        retry_reason: String,
        layer: String,
    },
    Recovery {
        action: RecoveryKind,
        reason: String,
    },
    ProcessStdin {
        process_id: String,
        bytes: usize,
    },
    ProcessStart {
        process_id: String,
        program: String,
    },
    ProcessEnd {
        process_id: String,
        exit_code: Option<i32>,
    },
    ToolSpill {
        status: SpillStatus,
        locator: String,
        original_bytes: usize,
    },
    RequestPermissions {
        tool: String,
        paths: Vec<String>,
    },
    PatchHunk {
        path: String,
        hunk: String,
    },
}

Stable event ordering (pi_agent_rust pattern).

Variants

AgentStart

ContextUsage

Fields

used_tokens: usize

context_window: usize

auto_compact_at: usize

Usage

Fields

model: String

usage: TokenUsage

estimated: bool

CompactionStart

Fields

reason: String

before_tokens: usize

CompactionEnd

Fields

reason: String

result: CompactionResult

SkillActivated

Fields

id: String

name: String

ToolSource

Fields

tool: String

source: ToolSource

TurnStart

Fields

turn: usize

MessageStart

Fields

role: Role

MessageDelta

Fields

delta: String

MessageEnd

Fields

role: Role

content: String

ToolCall(ToolCall)

ApprovalRequired(ApprovalRequest)

Host UX: tool needs approval (Codex-style ask payload).

PlanProposed(PlanProposal)

Host UX: the whole turn’s plan needs approval before anything runs.

PlanDecided

The host answered a Event::PlanProposed.

Fields

decision: PlanDecision

GuardrailWarning

Loop detection fired but the turn continues; the warning is also fed back to the model.

Fields

tool: String

reason: String

GuardrailStop

Loop detection ended the turn.

Fields

tool: String

reason: String

SelfHealing

A failing turn is being re-prompted with error context.

Fields

attempt: u8

max_attempts: u8

errors: Vec<String>

ToolExecutionStart(ToolCall)

ToolExecutionEnd(ToolResult)

TodoUpdated

The session todo list changed through the opt-in engine todo tool.

Fields

todos: TodoState

Full replacement state, suitable for hosts to render directly.

TurnEnd

Retained so existing host matches still compile. The loop emits only Event::TurnEnded.

Fields

turn: usize

TurnEnded

The one turn-complete event. Hosts that implement auto-continue policy read metadata.

Fields

turn: usize

Completed loop iteration.

metadata: TurnEndMetadata

Engine-observed completion facts; hosts decide whether to poke.

CacheAudit(CacheAudit)

Debug report describing prompt-cache stability for one provider request.

GateResult(GateResult)

Result of an opt-in workspace quality gate.

MemoryRecalled

Semantic graph memories selected for this prompt.

Fields

recalls: Vec<MemoryRecall>

AgentEnd

Error(String)

BudgetExceeded

Fields

reason: String

RetryReason

Fields

retry_reason: String

layer: String

Recovery

Empty-turn or stuck-tool recovery the host can forward.

Fields

action: RecoveryKind

reason: String

ProcessStdin

Fields

process_id: String

bytes: usize

ProcessStart

Fields

process_id: String

program: String

ProcessEnd

Fields

process_id: String

exit_code: Option<i32>

ToolSpill

Fields

status: SpillStatus

locator: String

original_bytes: usize

RequestPermissions

Fields

tool: String

paths: Vec<String>

PatchHunk

Fields

path: String

hunk: String

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 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.