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# StreamErrorRetryProcessor

`StreamErrorRetryProcessor` is an **error processor** that retries transient LLM API and stream failures. It includes built-in matching for OpenAI Responses stream errors and supports additional matchers for other provider-specific error shapes.

Mastra adds this processor to every agent's `errorProcessors` by default, last, after the `ProviderHistoryCompat`, `PrefillErrorHandler`, and `UnsupportedFileHandler` defaults, so the processors that repair a request get their chance before this one retries it unchanged. The default instance uses `maxRetries: 2` with a connection-reset matcher alongside the built-in matching, and it doesn't retry unknown errors or replay bad-request (HTTP 400) responses the repair processors couldn't fix. Supply your own instance in `errorProcessors` to change its policy. Because a default is only added when its `id` is missing from your list, your instance is used and the default isn't added alongside it.

## Usage example

Configure `StreamErrorRetryProcessor`. Supplying the same `id` means the default isn't added:

```typescript
import { Agent } from '@mastra/core/agent'
import { StreamErrorRetryProcessor } from '@mastra/core/processors'

export const agent = new Agent({
  id: 'openai-agent',
  name: 'openai-agent',
  instructions: 'You are a helpful assistant.',
  model: 'openai/gpt-5',
  errorProcessors: [new StreamErrorRetryProcessor({ maxRetries: 5 })],
  maxProcessorRetries: 5,
})
```

Set `maxProcessorRetries` alongside a `maxRetries` above `3`, because the agent stops error-processor retries at `3` when it's unset. See [Retry limits](#retry-limits).

To run only the processors you configure, with none of the defaults merged in, set `errorProcessorDefaults: false`. Without an `errorProcessors` list, the agent then runs no error processors. An empty `errorProcessors` list still gets the defaults. Supplying your own processor for all three default ids replaces every default with your own implementation.

## How it works

The processor checks the error and its cause chain for:

- Provider retry metadata: `isRetryable === true`
- Built-in OpenAI Responses stream error matching
- Matcher results: Any configured matcher that returns `true`

When the error is retryable, the processor returns `{ retry: true }`. It doesn't mutate messages.

When `delayMs` is set, the processor waits before signaling a retry. This is useful for transient network errors like `ECONNRESET` where immediately retrying is likely to fail again. The delay can be a fixed number of milliseconds or a function evaluated with the error args (for example, to implement exponential backoff).

### Retry limits

`maxRetries` defaults to `1` and limits this processor's retry requests. The agent also limits processor retries with `maxProcessorRetries`. When error processors are configured without an agent limit, the runtime cap is `3`.

Set both values explicitly to the same bounded value when you need a single retry budget. Keep model `maxRetries` at `0` for that call to avoid multiplying provider attempts.

### `Retry-After` handling

For retryable errors with a `Retry-After` response header, the processor reads case-insensitive delta-seconds and HTTP-date values through the error cause chain. It waits for the longer of `delayMs` and the bounded server delay.

`maxRetryAfterMs` defaults to `30_000`. It caps only provider-provided wait time. A longer explicit `delayMs` remains unchanged. Invalid or expired headers are ignored.

## Retry unknown errors

Set `retryUnknownErrors` to retry errors that don't match provider metadata or the built-in OpenAI matcher, including a custom matcher. Unknown-error retries use the processor-level `maxRetries` and `delayMs` values. Known authorization failures, including HTTP `401` and `403` responses, aren't retried:

```typescript
import { Agent } from '@mastra/core/agent'
import { StreamErrorRetryProcessor } from '@mastra/core/processors'

export const agent = new Agent({
  id: 'resilient-agent',
  name: 'Resilient agent',
  instructions: 'You are a helpful assistant.',
  model: 'openai/gpt-5',
  errorProcessors: [
    new StreamErrorRetryProcessor({
      retryUnknownErrors: true,
      maxRetries: 2,
      delayMs: 3000,
    }),
  ],
})
```

Specific matcher policies still take precedence over the unknown-error values. The option defaults to `false`, so unknown errors aren't retried unless you enable it.

## Delaying retries

Use `delayMs` with a custom matcher to retry transient network resets with a wait:

```typescript
import { Agent } from '@mastra/core/agent'
import { StreamErrorRetryProcessor } from '@mastra/core/processors'

const isECONNRESET = (error: unknown) => {
  if (!error || typeof error !== 'object') return false
  const code = (error as { code?: unknown }).code
  if (typeof code === 'string' && code.toUpperCase() === 'ECONNRESET') return true
  const message = error instanceof Error ? error.message : undefined
  return typeof message === 'string' && /econnreset|socket hang up/i.test(message)
}

export const agent = new Agent({
  id: 'resilient-agent',
  name: 'resilient-agent',
  instructions: 'You are a helpful assistant.',
  model: 'openai/gpt-5',
  errorProcessors: [
    new StreamErrorRetryProcessor({
      maxRetries: 2,
      delayMs: ({ retryCount }) => Math.min(1000 * 2 ** retryCount, 30000),
      matchers: [isECONNRESET],
    }),
  ],
})
```

## Default OpenAI Responses matcher

`isRetryableOpenAIResponsesStreamError` matches OpenAI Responses stream error chunks with `type: 'error'` or `type: 'response.failed'`. It retries known transient OpenAI error codes. As a fallback, it retries errors with explicit retry guidance such as `You can retry your request`.

`StreamErrorRetryProcessor` includes this matcher by default. You can also import it and reuse it in custom retry logic.

## Constructor parameters

**options** (`StreamErrorRetryProcessorOptions`): Configuration for retry handling.

## Properties

**id** (`'stream-error-retry-processor'`): Processor identifier.

**name** (`'Stream Error Retry Processor'`): Processor display name.

**processAPIError** (`(args: ProcessAPIErrorArgs) => ProcessAPIErrorResult | void`): Retries stream errors up to the configured retry limit.

## Related

- [Processor interface](https://mastra.ai/reference/processors/processor-interface)
- [Processors](https://mastra.ai/docs/agents/processors)