Enum SuspendTrigger 

pub enum SuspendTrigger {
    DagPosition,
    ValidationExhausted {
        task_name: String,
        retry_count: u32,
        last_attempt: String,
        validation_errors: Vec<ValidationErrorWire>,
    },
    AgentUnable {
        task_name: String,
        unable: UnableRecord,
    },
    AgentVariant {
        task_name: String,
        variant: String,
        payload: Value,
    },
}

Why the engine suspended execution at a checkpoint. This is the canonical wire-shape for the trigger discriminator on EngineEvent::Suspended; Stream 4 (#149 + #156 approach C) populates the AgentUnable variant, and Stream 6 (this stream, #156 approach B) populates ValidationExhausted.

Serde-tagged with an internal "kind" discriminator so deserializers can match on a single field without peeking at shape. Each variant carries its payload inline — there is no sidecar unable_payload / exhaustion field on Suspended itself.

Spec: docs/superpowers/specs/2026-04-18-epa-checkpoint-validation-design.md. The wire shape is locked per the Wave-1 round-3 tracker decision (“Suspended wire shape (S4 ↔ S6) = S6’s embedded-payload shape”).

Variants

DagPosition

The DAG reached an explicit checkpoint cp(...) call site. This is today’s only behaviour; the variant carries no payload because the checkpoint’s own expects: schema fully describes what comes back on resume.

ValidationExhausted

The task’s on_validation_exhausted: property fired: all validation retries consumed without producing a payload that passes the parse→schema→custom pipeline. Studio / SDKs render the last failing attempt + its errors so the human can correct in place.

Fields

task_name: String

retry_count: u32

last_attempt: String

validation_errors: Vec<ValidationErrorWire>

AgentUnable

Reserved for Stream 4 (#149 + #156 approach C) — emitted when a task with a T | Unable return type produces an Unable value and the flow routes it to a checkpoint via on unable <cp>. Shape is invariant across Stream 4’s four on unable forms: the payload is always the Unable record (reason/missing/category). Not produced by the engine in Stream 6 — defined here because Stream 6 owns the canonical SuspendTrigger type so Stream 4’s engine-emit site is pure code addition, no wire-shape change.

Fields

task_name: String

unable: UnableRecord

AgentVariant

Emitted when a task whose declared return type is a discriminated union A | B | ... | Unable produces a non-Unable variant and the flow routes that variant to a checkpoint via on <Variant> <cp>. variant is the canonical record name (PascalCase, matches the source identifier); payload is the parsed record (with the kind discriminator stripped). Studio renders a generic “agent returned variant ” badge on this trigger.

AgentUnable remains a specialization for the Unable arm — rather than AgentVariant { variant: "Unable", ... } — to preserve the existing Studio rendering path from #157 (zero-day compat).

Fields

task_name: String

variant: String

payload: Value

Trait Implementations

impl Clone for SuspendTrigger

fn clone(&self) -> SuspendTrigger

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SuspendTrigger

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

Formats the value using the given formatter.

impl Default for SuspendTrigger

fn default() -> SuspendTrigger

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for SuspendTrigger

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for SuspendTrigger

fn eq(&self, other: &SuspendTrigger) -> 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 SuspendTrigger

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for SuspendTrigger

impl StructuralPartialEq for SuspendTrigger