Run.timeTravel()

The .timeTravel() method re-executes a workflow starting from any specific step, using either stored snapshot data or custom context you provide. Use it to debug failed workflows and test individual steps with different inputs. It can also recover from errors without re-running the entire workflow.

Usage example

const run = await workflow.createRun()

const result = await run.timeTravel({
  step: 'step2',
  inputData: { value: 10 },
})

Parameters

step:

Step<string, any, TInputSchema, any, any, any, TEngineType> | [...Step<string, any, any, any, any, any, TEngineType>[], Step<string, any, TInputSchema, any, any, any, TEngineType>] | string | string[]

The target step to start execution from. It can be a Step instance, array of Steps (for nested workflows), step ID string, or array of step ID strings. Use dot notation or arrays for nested workflow steps (e.g., 'nestedWorkflow.step3' or ['nestedWorkflow', 'step3'])

inputData?:

z.infer<TInputSchema>

Input data for the target step. Must match the step's input schema. If not provided, uses data from the workflow snapshot

resumeData?:

any

Resume data to provide if the workflow was previously suspended

initialState?:

z.infer<TState>

Initial state to set for the workflow run. Used to set workflow-level state before execution

context?:

TimeTravelContext<any, any, any, any>

Execution context containing step results for steps before the target step. Each key is a step ID with a StepResult object containing status, payload, output, startedAt, endedAt, suspendPayload, and resumePayload

nestedStepsContext?:

Record<string, TimeTravelContext<any, any, any, any>>

Context for nested workflow steps. Keyed by nested workflow ID, each containing step results for that nested workflow

requestContext?:

RequestContext

Request Context data to use during time travel execution

outputWriter?:

(chunk: TOutput) => Promise<void>

Optional asynchronous function to handle output chunks as they are produced

tracingContext?:

TracingContext

Tracing context for creating child spans and adding metadata. Automatically injected when using Mastra's tracing system.

currentSpan?:

Span

Current span for creating child spans and adding metadata. Use this to create custom child spans or update span attributes during execution.

tracingOptions?:

TracingOptions

Options for Tracing configuration.

rootSpanName?:

string

Display name for the root span of this trace, replacing the default workflow run: '<id>' or agent run: '<id>' name. Use it to tell runs apart in trace lists.

metadata?:

Record<string, any>

Metadata to add to the root trace span. Useful for adding custom attributes like user IDs, session IDs, or feature flags.

requestContextKeys?:

string[]

Additional RequestContext keys to extract as metadata for this trace. Supports dot notation for nested values (e.g., 'user.id').

traceId?:

string

Trace ID to use for this execution (1-32 hexadecimal characters). If provided, this trace will be part of the specified trace.

parentSpanId?:

string

Parent span ID to use for this execution (1-16 hexadecimal characters). If provided, the root span will be created as a child of this span.

nestUnderParent?:

boolean

Set to true together with parentSpanId to attach this run as a child of that span inside the existing trace, for example an LLM judge under the run it scores. Exporters then keep the trace's own name, input, output, and tags. Leave unset when parentSpanId comes from your own tracing system. Ignored without a valid traceId and parentSpanId.

tags?:

string[]

Tags to apply to this trace. String labels for categorizing and filtering traces.

outputOptions?:

OutputOptions

Options for output configuration.

includeState?:

boolean

Whether to include the workflow run state in the result.

includeResumeLabels?:

boolean

Whether to include resume labels in the result.

Returns

result:

Promise<WorkflowResult<TState, TInput, TOutput, TSteps>>

A promise that resolves to the workflow execution result containing step outputs and status

traceId?:

string

The trace ID associated with this execution when Tracing is enabled. Use this to correlate logs and debug execution flow.

spanId?:

string

The root span ID associated with this execution when Tracing is enabled. Use this for span-level lookup and correlation.

Extended usage examples

Time travel with custom context

const result = await run.timeTravel({
  step: 'step2',
  context: {
    step1: {
      status: 'success',
      payload: { value: 0 },
      output: { step1Result: 2 },
      startedAt: Date.now(),
      endedAt: Date.now(),
    },
  },
})

Time travel to nested workflow step

// Using dot notation
const result = await run.timeTravel({
  step: 'nestedWorkflow.step3',
  inputData: { value: 10 },
})

// Using array of step IDs
const result = await run.timeTravel({
  step: ['nestedWorkflow', 'step3'],
  inputData: { value: 10 },
})

Time travel with initial state

const result = await run.timeTravel({
  step: 'step2',
  inputData: { value: 10 },
  initialState: {
    counter: 5,
    metadata: { source: 'time-travel' },
  },
})

Time travel with nested workflows context

const result = await run.timeTravel({
  step: 'nestedWorkflow.step3',
  context: {
    step1: {
      status: 'success',
      payload: { value: 0 },
      output: { step1Result: 2 },
      startedAt: Date.now(),
      endedAt: Date.now(),
    },
    nestedWorkflow: {
      status: 'running',
      payload: { step1Result: 2 },
      startedAt: Date.now(),
    },
  },
  nestedStepsContext: {
    nestedWorkflow: {
      step2: {
        status: 'success',
        payload: { step1Result: 2 },
        output: { step2Result: 3 },
        startedAt: Date.now(),
        endedAt: Date.now(),
      },
    },
  },
})

Concurrent time travel calls

timeTravel() doesn't claim the run before it executes. It only rejects runs whose stored status is running. If two timeTravel() calls target the same run at the same time, both can proceed, and the target step and every step after it run once per call.

This matters whenever time travel can be triggered more than once for the same run, such as a "retry from step" button pressed twice or a retried API request. Make sure only one call proceeds per run in your application, for example with a per-run lock or an idempotency key:

const inFlight = new Set<string>()

async function retryFromStep(runId: string, step: string) {
  if (inFlight.has(runId)) {
    throw new Error(`Time travel already in progress for run ${runId}`)
  }
  inFlight.add(runId)
  try {
    const run = await workflow.createRun({ runId })
    return await run.timeTravel({ step })
  } finally {
    inFlight.delete(runId)
  }
}

The in-memory set above only protects a single process. If several server instances can handle the same run, use a shared lock instead, such as a database row lock.

Unlike resume(), timeTravel() has no WORKFLOW_RESUME_ALREADY_CLAIMED equivalent, and the HTTP endpoint doesn't return 409 Conflict for concurrent calls.

Notes

• Time travel requires storage to be configured since it relies on persisted workflow snapshots
• When re-executing a workflow, the workflow loads the existing snapshot from storage (if available)
• Step results before the target step are reconstructed from the snapshot or provided context
• Execution begins from the specified step with the provided or reconstructed input data
• If a step that precedes the target in the current workflow definition has no recorded entry in the snapshot (for example, the step was renamed since the run was recorded, or the run never reached it), timeTravel rejects with a descriptive error before anything executes and the stored snapshot is left unchanged
• The workflow continues to completion from that point forward
• Time travel can be used on workflows that haven't been run yet by providing custom context or input data for the step to start from.

Related

• Time Travel
• Workflows overview
• Workflow.createRun()
• Snapshots
• Suspend and Resume