Enum AgentError 

#[non_exhaustive]
pub enum AgentError {
    Memory(MemoryError),
    Provider(ProviderError),
    TooManyToolRounds(usize),
    Cancelled,
    StructuredParse(String),
    StructuredRetriesExhausted(usize),
    DeadlineExceeded,
    EffectRequiresHarness(String),
    InvalidStep(String),
}

Reasons an Agent run can fail.

A tool execution failure is not an AgentError — it is fed back to the model as text, and the model decides what to do next. #[non_exhaustive] ensures future error categories won’t be a breaking change.

Examples

use molo::AgentError;

// The round-limit error carries the limit value, useful for prompting
// the user to adjust the config
let err = AgentError::TooManyToolRounds(10);
assert!(err.to_string().contains("10"));

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.

Memory(MemoryError)

Context access failed.

Provider(ProviderError)

Communication with the LLM failed.

TooManyToolRounds(usize)

The model kept requesting tools past the implementation’s maximum number of rounds without giving a final answer. Increase via AgentConfig::with_max_tool_rounds.

Cancelled

The run was cooperatively cancelled (via the CancellationToken passed to run/run_stream); already-recorded messages are kept, not rolled back.

StructuredParse(String)

Structured output: validation passed but deserializing into the target type failed — triggered when the JSON the schema allows is inconsistent with the serde representation of run_typed’s type parameter U (auto-generated schemas agree with U by default; conflicts come from #[schemars(...)] custom derives).

StructuredRetriesExhausted(usize)

Structured output: validation failed more times than the configured limit. Increase via AgentConfig::with_max_structured_retries.

DeadlineExceeded

The run-level deadline elapsed before the run completed.

EffectRequiresHarness(String)

A tool requested a side effect, but this high-level agent run has no harness driver to govern and execute it.

InvalidStep(String)

A step-wise kernel received an observation that does not match its current state.

Trait Implementations

impl Clone for AgentError

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for AgentError

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

Formats the value using the given formatter.

impl Display for AgentError

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

Formats the value using the given formatter.

impl Eq for AgentError

impl Error for AgentError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<MemoryError> for AgentError

fn from(source: MemoryError) -> Self

Converts to this type from the input type.

impl From<ProviderError> for AgentError

fn from(source: ProviderError) -> Self

Converts to this type from the input type.

impl PartialEq for AgentError

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for AgentError