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Class: AssemblyAISTTProvider

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:203

Speech-to-text provider that uses the AssemblyAI async transcription API.

Three-Step Workflow​

AssemblyAI uses an asynchronous transcription pipeline that requires three sequential HTTP requests:

  1. Upload — POST /v2/upload sends the raw audio bytes to AssemblyAI's CDN and returns an upload_url. This step is necessary because the transcript endpoint accepts URLs, not raw audio.

  2. Submit — POST /v2/transcript creates a transcription job referencing the upload URL. Returns a transcript id used for polling. Optional features like speaker_labels are enabled in this request's JSON body.

  3. Poll — GET /v2/transcript/:id is called every POLL_INTERVAL_MS (1 second) until the transcript status transitions to 'completed' or 'error'. The polling loop is bounded by DEFAULT_TIMEOUT_MS (120 seconds) to prevent indefinite waiting.

AbortController Usage​

An optional AbortSignal can be passed via options.providerSpecificOptions.signal to cancel the transcription at any point. The signal is forwarded to all three fetch calls and also checked at the top of each polling iteration. When aborted, an error is thrown immediately without waiting for the current fetch to complete.

Error Handling​

  • Non-2xx responses at any step throw an Error with the HTTP status and body.
  • status === 'error' on the transcript throws with AssemblyAI's error message.
  • Timeout expiry throws with the transcript ID for manual inspection.
  • Aborted signals throw with a descriptive cancellation message.

See​

AssemblyAISTTProviderConfig for configuration options See AssemblyAITranscript for the polling response shape.

Example​

const provider = new AssemblyAISTTProvider({
  apiKey: process.env.ASSEMBLYAI_API_KEY!,
});

// Basic transcription
const result = await provider.transcribe({ data: audioBuffer });

// With diarization and cancellation support
const controller = new AbortController();
const result = await provider.transcribe(
  { data: audioBuffer },
  {
    enableSpeakerDiarization: true,
    providerSpecificOptions: { signal: controller.signal },
  },
);

Implements​

Constructors​

Constructor​

new AssemblyAISTTProvider(config): AssemblyAISTTProvider

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:234

Parameters​

config​

AssemblyAISTTProviderConfig

Returns​

AssemblyAISTTProvider

Properties​

displayName​

readonly displayName: "AssemblyAI" = 'AssemblyAI'

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:208

Human-readable display name for UI and logging.

Implementation of​

SpeechToTextProvider.displayName

id​

readonly id: "assemblyai" = 'assemblyai'

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:205

Unique provider identifier used for registration and resolution.

Implementation of​

SpeechToTextProvider.id

supportsStreaming​

readonly supportsStreaming: false = false

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:215

Streaming is not supported by this provider's async pipeline. AssemblyAI does offer a separate real-time streaming API via WebSocket, but that would be a different provider implementation.

Implementation of​

SpeechToTextProvider.supportsStreaming

Methods​

getProviderName()​

getProviderName(): string

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:249

Returns the human-readable provider name.

Returns​

string

The display name string 'AssemblyAI'.

Example​

provider.getProviderName(); // 'AssemblyAI'

Implementation of​

SpeechToTextProvider.getProviderName

transcribe()​

transcribe(audio, options?): Promise<SpeechTranscriptionResult>

Defined in: packages/agentos/src/io/hearing/providers/AssemblyAISTTProvider.ts:282

Transcribes an audio buffer via the AssemblyAI three-step async pipeline: upload, submit, and poll.

Parameters​

audio​

SpeechAudioInput

Raw audio data and associated metadata. The data buffer is uploaded to AssemblyAI's CDN in step 1.

options?​

SpeechTranscriptionOptions = {}

Optional transcription settings. Pass providerSpecificOptions.signal (an AbortSignal) to cancel at any point in the pipeline.

Returns​

Promise<SpeechTranscriptionResult>

A promise resolving to the normalized transcription result.

Throws​

When the upload API returns a non-2xx status.

Throws​

When the transcript submit API returns a non-2xx status.

Throws​

When the polling API returns a non-2xx status.

Throws​

When the transcript status becomes 'error' (includes AssemblyAI's error message, e.g. "Audio file could not be decoded").

Throws​

When the 120-second timeout is exceeded (includes the transcript ID for manual inspection via the AssemblyAI dashboard).

Throws​

When the caller's AbortSignal is triggered.

Example​

const result = await provider.transcribe(
  { data: wavBuffer, mimeType: 'audio/wav' },
  { enableSpeakerDiarization: true, language: 'en' },
);
console.log(result.text);
console.log(result.segments?.map(s => `[${s.speaker}] ${s.text}`));

Implementation of​

SpeechToTextProvider.transcribe