Universal-3.5 Pro is now on OpenRouter

AssemblyAI has made its Universal-3.5 Pro speech-to-text model available through OpenRouter’s transcription endpoint, allowing developers to access it with an existing OpenRouter API key, billing relationship, and OpenAI-compatible request format. The Sync Speech-to-Text API is designed for short, turn-based audio interactions such as voice agents, dictation, phone trees, and push-to-talk messages, returning a complete transcript in a single request without polling or persistent WebSocket connections. The service supports WAV clips from 80 milliseconds to two minutes and up to 40 MB, with direct API median latency reported at about 134 milliseconds plus OpenRouter routing time. Developers can improve recognition for specialized or contextual audio through prompts, per-request key terms, and conversation history, while word timestamps are available through OpenRouter’s verbose JSON response options. AssemblyAI states that Universal-3.5 Pro achieves a 1.59% normalized word error rate on short-form audio and supports 19 native languages, with particular emphasis on recognizing proper nouns, alphanumeric strings, email addresses, and postal addresses. Pricing is listed at $0.45 per hour of audio, passed through by OpenRouter without markup, with an introductory first-week discount of 50%.

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