Handle iii engine and SDK errors across Node, Python, Rust, and browser workers. Use when interpreting error codes, retryability, RBAC denial, timeouts, handler failures, or SDK-specific exception surfaces.

Error Handling iii has two broad error classes: SDK/local errors and engine/remote invocation errors. Agents should branch on the error code instead of matching only message strings. Error Codes Branch on exact code strings, but keep engine wire codes separate from SDK local codes. Code Emitted by Meaning Typical handling function not found Engine and SDK local dispatch No registered function is available under that ID Check function ID, worker install/startup, discovery, and trigger type hints invocation error Engine invocation/router path Engine failed to route, remember, or complete the invocation Inspect engine logs, protocol state, and worker connectivity invocation stopped Engine invocation handler Invocation was cancelled or stopped by the engine/runtime Treat as failed work; decide whether caller should retry FORBIDDEN RBAC / worker gated engine functions RBAC denied the action Do not retry blindly; inspect policy, auth context, and allowed functions timeout Engine/worker wire error when a worker reports lowercase timeout Invocation exceeded a timeout reported through the wire protocol Treat as timeout, but do not assume every SDK maps it to a timeout subclass function not invokable SDK local dispatch Registration exists but cannot be invoked as a normal local function Inspect registration/invocation type invocation failed SDK worker handler wrappers Local worker handler, HTTP invoked function wrapper, or SDK side handler path failed Inspect handler logs, stacktrace, and payload validation TIMEOUT Node/Python SDK caller timeout Client waited longer than trigger() timeout Increase timeout only if the workload is expected to run long; otherwise optimize or enqueue Handler vs Engine Errors Handler errors originate in user function code, SDK local dispatch, or HTTP invoked endpoints. Engine errors originate in routing, invocation state, RBAC, protocol handling, or worker reported wire errors. Queue retries only apply to enqueued work. Synchronous failures are returned directly to the caller. Void dispatch does not return handler results, so use logs/observability for failures. Retryability Retry transient timeout , TIMEOUT , transport, or worker reconnect failures only when the operation is idempotent. Do not retry FORBIDDEN without changing auth/policy. Do not retry function not found by calling the same ID repeatedly; discover functions or install/start the missing worker. For reliable background work, use TriggerAction.Enqueue({ queue }) and queue retry/DLQ policy. SDK Surfaces Node Python Rust Browser Browser trigger calls reject with JavaScript errors. Preserve the engine provided code/message when present and show policy failures as permission errors in UI. Pattern Boundaries For invocation modes and enqueue decisions, prefer iii core primitives . For SDK specific exception classes and syntax, prefer iii sdk reference . For workflow level retry and DLQ design, prefer iii architecture patterns . For RBAC policy design and logs/traces around worker failures, use the matching worker docs under engine/src/workers/ /skills . When to Use Use this skill when the task mentions iii errors, exception handling, failed invocations, timeouts, forbidden calls, retry behavior, or SDK error classes. Boundaries Do not retry non idempotent work automatically unless it is enqueued under queue policy. Do not treat RBAC denial as a missing worker. Do not generate removed service APIs or adapter extension APIs.

iii-error-handling