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These errors surface from the workflow runtime when a multi-step DAG fails to validate or complete. All inherit from InternalMcpError (not safe to surface verbatim to clients — the runtime maps them to a generic JSON-RPC error before sending).

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Reference

ClassInheritsWhen
WorkflowStepNotFoundErrorInternalMcpErrorA step alias was referenced before it completed
WorkflowTimeoutErrorInternalMcpErrorThe whole workflow exceeded its timeoutMs
WorkflowDagValidationErrorInternalMcpErrorThe declared DAG had a cycle, missing dependency, or bad ref
WorkflowJobTimeoutErrorInternalMcpErrorAn individual job step exceeded its timeoutMs

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Usage

import {
  WorkflowStepNotFoundError,
  WorkflowTimeoutError,
  WorkflowDagValidationError,
  WorkflowJobTimeoutError,
} from '@frontmcp/sdk';

// Inside a workflow runtime extension
if (!completed.has(alias)) {
  throw new WorkflowStepNotFoundError(alias);
}