Speech-to-text REST API v3.0 will be retired by 31 March 2026.

Speech-to-text REST API v3.0 will be retired by 31 March 2026. Update your code that uses Speech-to-text REST API.

We recently updated the Speech-to-text REST API to version 3.1. Version 3.1 builds on the capabilities of the previous version and adds new features including language identification and multi-speaker diarization. With these enhancements, we’ll retire version 3.0 of the API on 31 March 2026.
Source: Azure Roadmap