AssemblyAI Universal-3.5 Pro (async)
API id stays `universal-3-pro` (pass in `speech_models`, plural; singular `speech_model` is deprecated). 18 languages; use universal-2 ($0.15/hr, 99+ languages) for broad coverage and legacy features (auto_chapters/summarization fail on 3.5 Pro). Added to OpenRouter 2026-09-22. Launch date 2026-07-07 from AssemblyAI releases collection via search (not opened directly). Streaming sibling: assemblyai-universal-3-6-pro-realtime. Related AssemblyAI products: Voice Agent API (GA April 2026, $4.50/hr all-in) and LLM Gateway (OpenAI-compatible multi-provider LLM API that replaced LeMUR; migration guide at assemblyai.com/docs/llm-gateway/migration-from-lemur; exact rename date not verified).
- Input
- audio, text
- Output
- text
- License
- proprietary
- Pricing
- per hour: $0.21 (per audio hour (pre-recorded); keyterms prompting +$0.05/hr, diarization +$0.02/hr, Medical Mode +$0.15/hr) source
- Verified
- 2026-09-29
How to call it
| Provider | Model id | Endpoint / URL | Docs |
|---|---|---|---|
| AssemblyAI API | universal-3-pro | https://api.assemblyai.com/v2/transcript | docs |
| OpenRouter | — | openrouter.ai/assemblyai/universal-3-5-pro | — |
| AssemblyAI Dictation API | (Universal-3.5 Pro + LLM cleanup) | https://dictation.assemblyai.com/v1/transcribe/live | docs |
Notable capabilities (3)
- Promptable speech language model: Universal-3 Pro (Feb 2026) introduced plain-language prompts controlling transcription (disfluencies, multilingual handling, PII, formatting); 3.5 Pro focuses on entities, rare words and domain terms with an LLM-based decoder. source
- Dictation API (polished text from short utterances) (found after launch): Launched 2026-09-15: up to 5 s audio per request (chunked upload), removes fillers, resolves self-corrections and fixes name spellings via `llm_instruction`, `keyterms_prompt` and `stt_prompt`; 0.36 s average response, 3.87% WER on short-form audio (vendor-cited), 19 languages, $0.62/hour all-in. Open-source MIT macOS demo app 'Blurt'. source
- Medical Mode (found after launch): `domain: medical-v1` for EN/ES/DE/FR clinical vocabulary; replaces deprecated Slam-1. source