Errors

Every error extends RungsError and has a stable code. Branch on the class or the code, never on the message, which may become more helpful over time.

Class	Code	When
FlowDefinitionError	FLOW_INVALID	Invalid flow definition
FlowNotFoundError	FLOW_NOT_FOUND	No flow with this key (and version) for the tenant or globally (EC-56). Exposes flowKey, version?, tenantId?
ConfigurationError	CONFIG_INVALID	createRungs was given unusable options (missing store, clock or ids, an invalid dispatchRetry duration, events: "discard" with onEvent), clock or ids returned unusable values, or dispatchPending was called without onEvent
InvalidCommandError	COMMAND_INVALID	Malformed command input (e.g. empty IDs, non-JSON payload, override without a comment). The message names each problem
FlowNotApplicableError	FLOW_NOT_APPLICABLE	Submit refused because every step was skipped and the flow uses onAllSkipped: "fail" (EC-39). Exposes flowKey, skippedStepIds
RequestNotFoundError	REQUEST_NOT_FOUND	Unknown request
NotAssignedError	NOT_ASSIGNED	Actor has no pending task on this request, or is not the requester for resubmit / withdraw
InvalidTransitionError	INVALID_TRANSITION	e.g. approving a closed request
ConflictError	VERSION_CONFLICT	expectedVersion mismatch or concurrent write (EC-15). Exposes requestId, expectedVersion, actualVersion
ResolutionError	RESOLUTION_FAILED	A host callback (role lookup, named resolver, isActiveUser) threw or returned invalid data (EC-05). Usually transient: nothing changed, so the command can be retried. The original error is in cause; exposes stepId
NoApproversError	NO_APPROVERS	Submit refused because a step has no approvers (onEmptyStep: "fail") or cannot reach its quorum (EC-02, EC-04, EC-43, EC-45). A configuration or data problem: retrying will not help. Exposes stepId, reason, removed
ConditionError	CONDITION_INVALID	A gt/gte/lt/lte condition meets a missing field or a type mismatch (EC-40). Exposes field, op, expected, received

Rungs checks workflow routing (is this actor assigned to a task?), not authentication or permissions. Your application signs people in and decides, for example, who is an administrator, before it calls a command.

ResolutionError is usually worth retrying: a callback failed and nothing changed. NoApproversError is not: a step has nobody who can approve it until your data or the flow changes.