BatchPartsProcessor

The BatchPartsProcessor is an output processor that batches multiple stream parts together to reduce the frequency of emissions during streaming. This processor is useful for reducing network overhead and consolidating small text chunks for users, while controlling emissions to optimize streaming performance.

Usage example

import { BatchPartsProcessor } from '@mastra/core/processors'

const processor = new BatchPartsProcessor({
  batchSize: 5,
  maxWaitTime: 100,
  emitOnNonText: true,
})

Constructor parameters

options?:

Options

Configuration options for batching stream parts

Options

batchSize?:

number

Number of parts to batch together before emitting

maxWaitTime?:

number

Maximum time to wait before emitting a batch (in milliseconds). If set, will emit the current batch even if it hasn't reached batchSize

emitOnNonText?:

boolean

Whether to emit immediately when a non-text part is encountered

Returns

id:

string

Processor identifier set to 'batch-parts'

name:

string

Processor display name. Always Batch Parts.

processOutputStream:

(args: { part: ChunkType; streamParts: ChunkType[]; state: Record<string, any>; abort: (reason?: string) => never }) => Promise<ChunkType | null>

Processes streaming output parts to batch them together

flush:

(state?: BatchPartsState) => ChunkType | null

Force flush any remaining batched parts when the stream ends

Extended usage example

src/mastra/agents/batched-agent.ts

import { Agent } from '@mastra/core/agent'
import { BatchPartsProcessor } from '@mastra/core/processors'

export const agent = new Agent({
  id: 'batched-agent',
  name: 'batched-agent',
  instructions: 'You are a helpful assistant',
  model: 'openai/gpt-5.6-sol',
  outputProcessors: [
    new BatchPartsProcessor({
      batchSize: 5,
      maxWaitTime: 100,
      emitOnNonText: true,
    }),
  ],
})

Related

• Guardrails