# Snapshots

In Mastra, a snapshot is a serializable representation of a workflow's complete execution state at a specific point in time. Snapshots capture all the information needed to resume a workflow from exactly where it left off, including:

- The current state of each step in the workflow
- The outputs of completed steps
- The execution path taken through the workflow
- Any suspended steps and their metadata
- The remaining retry attempts for each step
- Additional contextual data needed to resume execution

Snapshots are automatically created and managed by Mastra whenever a workflow is suspended, and are persisted to the configured storage system.

## The role of snapshots in suspend and resume

Snapshots are the key mechanism enabling Mastra's suspend and resume capabilities. When a workflow step calls `await suspend()`:

1. The workflow execution is paused at that exact point
2. The current state of the workflow is captured as a snapshot
3. The snapshot is persisted to storage
4. The workflow step is marked as "suspended" with a status of `'suspended'`
5. Later, when `resume()` is called on the suspended step, the snapshot is retrieved
6. The workflow execution resumes from exactly where it left off

This mechanism provides a powerful way to implement human-in-the-loop workflows, handle rate limiting, wait for external resources, and implement complex branching workflows that may need to pause for extended periods.

## Snapshot anatomy

Each snapshot includes the `runId`, input, step status (`success`, `suspended`, etc.), any suspend and resume payloads, and the final output. This ensures full context is available when resuming execution.

```json
{
  "runId": "34904c14-e79e-4a12-9804-9655d4616c50",
  "status": "success",
  "value": {},
  "context": {
    "input": {
      "value": 100,
      "user": "Michael",
      "requiredApprovers": ["manager", "finance"]
    },
    "approval-step": {
      "payload": {
        "value": 100,
        "user": "Michael",
        "requiredApprovers": ["manager", "finance"]
      },
      "startedAt": 1758027577955,
      "status": "success",
      "suspendPayload": {
        "message": "Workflow suspended",
        "requestedBy": "Michael",
        "approvers": ["manager", "finance"]
      },
      "suspendedAt": 1758027578065,
      "resumePayload": { "confirm": true, "approver": "manager" },
      "resumedAt": 1758027578517,
      "output": { "value": 100, "approved": true },
      "endedAt": 1758027578634
    }
  },
  "activePaths": [],
  "serializedStepGraph": [
    {
      "type": "step",
      "step": {
        "id": "approval-step",
        "description": "Accepts a value, waits for confirmation"
      }
    }
  ],
  "suspendedPaths": {},
  "waitingPaths": {},
  "result": { "value": 100, "approved": true },
  "requestContext": {},
  "timestamp": 1758027578740
}
```

## How snapshots are saved and retrieved

Snapshots are saved to the configured storage system. By default, they use libSQL, but you can configure Upstash or PostgreSQL instead. Each snapshot is saved in the `workflow_snapshots` table and identified by the workflow's `runId`.

Read more about:

- [libSQL Storage](https://mastra.ai/reference/storage/libsql)
- [Upstash Storage](https://mastra.ai/reference/storage/upstash)
- [PostgreSQL Storage](https://mastra.ai/reference/storage/postgresql)

### Saving snapshots

When a workflow is suspended, Mastra automatically persists the workflow snapshot with these steps:

1. The `suspend()` function in a step execution triggers the snapshot process
2. The `WorkflowInstance.suspend()` method records the suspended machine
3. `persistWorkflowSnapshot()` is called to save the current state
4. The snapshot is serialized and stored in the configured database in the `workflow_snapshots` table
5. The storage record includes the workflow name, run ID, and the serialized snapshot

### Retrieving snapshots

When a workflow is resumed, Mastra retrieves the persisted snapshot with these steps:

1. The `resume()` method is called with a specific step ID
2. The snapshot is loaded from storage using `loadWorkflowSnapshot()`
3. The snapshot is parsed and prepared for resumption
4. The workflow execution is recreated with the snapshot state
5. The suspended step is resumed, and execution continues

```typescript
const storage = mastra.getStorage()
const workflowStore = await storage?.getStore('workflows')

const snapshot = await workflowStore?.loadWorkflowSnapshot({
  runId: '<run-id>',
  workflowName: '<workflow-id>',
})

console.log(snapshot)
```

## Storage options for snapshots

Snapshots are persisted using a `storage` instance configured on the `Mastra` class. This storage layer is shared across all workflows registered to that instance. Mastra supports multiple storage options for flexibility in different environments.

```typescript
import { Mastra } from '@mastra/core'
import { LibSQLStore } from '@mastra/libsql'
import { approvalWorkflow } from './workflows'

export const mastra = new Mastra({
  storage: new LibSQLStore({
    id: 'mastra-storage',
    url: ':memory:',
  }),
  workflows: { approvalWorkflow },
})
```

- [libSQL Storage](https://mastra.ai/reference/storage/libsql)
- [PostgreSQL Storage](https://mastra.ai/reference/storage/postgresql)
- [MongoDB Storage](https://mastra.ai/reference/storage/mongodb)
- [Upstash Storage](https://mastra.ai/reference/storage/upstash)
- [Cloudflare D1](https://mastra.ai/reference/storage/cloudflare-d1)
- [DynamoDB](https://mastra.ai/reference/storage/dynamodb)
- [More storage providers](https://mastra.ai/docs/memory/storage)

## Best practices

1. **Ensure Serializability**: Any data that needs to be included in the snapshot must be serializable (convertible to JSON).
2. **Minimize Snapshot Size**: Avoid storing large data objects directly in the workflow context. Instead, store references to them (like IDs) and retrieve the data when needed.
3. **Handle Resume Context Carefully**: When resuming a workflow, carefully consider what context to provide. This will be merged with the existing snapshot data.
4. **Set Up Proper Monitoring**: Implement monitoring for suspended workflows, especially long-running ones, to ensure they're properly resumed.
5. **Consider Storage Scaling**: For applications with many suspended workflows, ensure your storage solution is appropriately scaled.

## Custom snapshot metadata

You can attach custom metadata when suspending a workflow by defining a `suspendSchema`. This metadata is stored in the snapshot and made available when the workflow is resumed.

```typescript
import { createWorkflow, createStep } from '@mastra/core/workflows'
import { z } from 'zod'

const approvalStep = createStep({
  id: 'approval-step',
  description: 'Accepts a value, waits for confirmation',
  inputSchema: z.object({
    value: z.number(),
    user: z.string(),
    requiredApprovers: z.array(z.string()),
  }),
  suspendSchema: z.object({
    message: z.string(),
    requestedBy: z.string(),
    approvers: z.array(z.string()),
  }),
  resumeSchema: z.object({
    confirm: z.boolean(),
    approver: z.string(),
  }),
  outputSchema: z.object({
    value: z.number(),
    approved: z.boolean(),
  }),
  execute: async ({ inputData, resumeData, suspend }) => {
    const { value, user, requiredApprovers } = inputData
    const { confirm } = resumeData ?? {}

    if (!confirm) {
      return await suspend({
        message: 'Workflow suspended',
        requestedBy: user,
        approvers: [...requiredApprovers],
      })
    }

    return {
      value,
      approved: confirm,
    }
  },
})
```

### Providing resume data

Use `resumeData` to pass structured input when resuming a suspended step. It must match the step’s `resumeSchema`.

```typescript
const workflow = mastra.getWorkflow('approvalWorkflow')

const run = await workflow.createRun()

const result = await run.start({
  inputData: {
    value: 100,
    user: 'Michael',
    requiredApprovers: ['manager', 'finance'],
  },
})

if (result.status === 'suspended') {
  const resumedResult = await run.resume({
    step: 'approval-step',
    resumeData: {
      confirm: true,
      approver: 'manager',
    },
  })
}
```

## Related

- [Control Flow](https://mastra.ai/docs/workflows/control-flow)
- [Suspend & Resume](https://mastra.ai/docs/workflows/suspend-and-resume)
- [Time Travel](https://mastra.ai/docs/workflows/time-travel)
- [Human-in-the-loop](https://mastra.ai/docs/workflows/human-in-the-loop)