As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/assemblyai-universal-3-5-pro/

# AssemblyAI Universal-3.5 Pro (async)

AssemblyAI, Universal-3 family. Status: current. Type: speech and audio. Released: 2026-07-07.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| AssemblyAI API | `universal-3-pro` | https://api.assemblyai.com/v2/transcript | https://www.assemblyai.com/docs/getting-started/universal-3-5-pro |
| OpenRouter |  |  | https://openrouter.ai/assemblyai/universal-3-5-pro |
| AssemblyAI Dictation API | `(Universal-3.5 Pro + LLM cleanup)` | https://dictation.assemblyai.com/v1/transcribe/live | https://www.assemblyai.com/blog/dictation-api |

## Pricing

- Per hour: $0.21
- Unit as published: per audio hour (pre-recorded); keyterms prompting +$0.05/hr, diarization +$0.02/hr, Medical Mode +$0.15/hr
- Source: https://www.assemblyai.com/pricing
- Last checked: 2026-09-29

## Specs

- Input: audio, text
- Output: text
- Context window: not published
- Max output: not published
- Open weights: no
- Licence: proprietary

## Where it stands

- Newer speech and audio models in the registry since its release: 46. The 5 newest:
  - NVIDIA Nemotron 3.5 Transcribe (30B-A4B) (2026-10-28) https://postcutoff.com/m/nemotron-3-5-transcribe/
  - Hy-SimulMT-30B-A3B (2026-10-22) https://postcutoff.com/m/hy-simulmt-30b-a3b/
  - Eleven Realtime v1 Max / Mini (2026-10-20) https://postcutoff.com/m/eleven-realtime-v1-max/
  - Voxtral Mini Transcribe 3 (+ Mini Transcribe Realtime 3) (2026-10-20) https://postcutoff.com/m/voxtral-mini-transcribe-3/
  - Voxtral Small Transcribe 3 (2026-10-20) https://postcutoff.com/m/voxtral-small-transcribe-3/
- After it from AssemblyAI: AssemblyAI Universal-3.6 Pro Realtime (2026-09-29) https://postcutoff.com/m/assemblyai-universal-3-6-pro-realtime/
- Closed weights; access is hosted only.

## What stands out

- 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: https://www.assemblyai.com/blog/introducing-universal-3-pro
- 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: https://www.assemblyai.com/blog/dictation-api
- Medical Mode (found after launch): `domain: medical-v1` for EN/ES/DE/FR clinical vocabulary; replaces deprecated Slam-1. Source: https://www.assemblyai.com/llms/models.md

## Notes

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).

Sources: https://www.assemblyai.com/llms/models.md , https://www.assemblyai.com/pricing

Model page: https://postcutoff.com/m/assemblyai-universal-3-5-pro/