mod error

module error

Error types for the NeMo Flow runtime.

All fallible operations in the runtime return Result<T>, which uses FlowError as the error type. Errors are categorized by cause (duplicate registration, missing entity, guardrail rejection, etc.).

Types

type Result<T>

A specialized Result type for NeMo Flow operations.

Enums

enum FlowError

The error type for all NeMo Flow runtime operations.

Each variant represents a distinct failure mode that callers can match on to determine the appropriate recovery strategy.

AlreadyExists(String)

A resource with the given name is already registered.

Returned when attempting to register a guardrail, intercept, or subscriber with a name that is already in use. Deregister the existing entry first, or choose a different name.

NotFound(String)

The requested resource was not found.

Returned when attempting to remove a scope handle by UUID that does not exist in the scope stack, or when looking up a non-existent entity.

InvalidArgument(String)

A function argument was invalid for the requested operation.

Returned when a provided value is well-formed but violates an API precondition, such as attempting to pop a scope that is not currently at the top of the stack.

ScopeStackEmpty

The scope stack is empty.

This should not occur under normal operation because the root scope is always present and cannot be removed.

GuardrailRejected(String)

A conditional execution guardrail rejected the operation.

The contained string is the rejection reason provided by the guardrail. This is returned during tool_call_execute or llm_call_execute when a conditional guardrail returns Some(reason).

Internal(String)

An internal runtime error (e.g., lock poisoning).