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, record, 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`	A target worker's handler, forwarded verbatim by the engine	Not produced by the engine or the Node/Python SDKs (they emit `TIMEOUT`); appears only if the worker you called returns it	Treat as a timeout if you know the target worker emits it; otherwise branch on `TIMEOUT`
`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

iii-error-handling

Error Handling

Error Codes