We rely on the OpenAI audio/speech endpoint for production text-to-speech.
The current gpt-4o-mini-tts model, with current snapshot gpt-4o-mini-tts-2025-12-15, still appears to have a serious truncation issue: generated audio often cuts off the final sentence or the end of the final sentence.
This is not an API error response. The request succeeds and returns audio, but the returned audio is incomplete. Retrying the same input sometimes produces complete audio, which makes this difficult to safely detect without post-generation validation.
Because of this, we have had to keep using gpt-4o-mini-tts-2025-03-20, which has been much more reliable for this failure mode in our usage. The problem is that the deprecation docs now list gpt-4o-mini-tts-2025-03-20 for shutdown on 2026-07-23.
That leaves us without a viable migration path for this use case. Current gpt-4o-mini-tts still truncates final sentences. The 2025-03-20 snapshot is the only reliable option we have found, but it is being deprecated. tts-1 and tts-1-hd are not equivalent replacements for promptable voice control and quality. The deprecation table suggests gpt-realtime, but that is not a drop-in replacement for existing audio/speech generation workflows.
Please fix the truncation bug in the current gpt-4o-mini-tts model, or keep/provide at least one stable audio/speech model or snapshot that can reliably generate complete audio. At minimum, please confirm the recommended migration path for developers who need non-realtime TTS and cannot accept final-sentence truncation.
Happy to provide concrete request IDs or audio samples via a private support channel if useful.
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gpt-4o-mini-tts-2025-12-15 also ignores TTS instructions. So it is a worse model than gpt-4o-mini-tts-2025-03-20.
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There a has been a few threads about this prior but I think the issue lost attention once people realized you can still use gpt-4o-mini-tts-2025-03-20. Now OpenAI is removing this version and this is very bad.
The newer version, gpt-4o-mini-tts-2025-12-15, is TERRIBLE at acting and its not usable for me. If gpt-4o-mini-tts-2025-12-15 is not fixed, and gpt-4o-mini-tts-2025-03-20 goes away, I will not be able to use OpenAI TTS anymore.
To illustrate the issue, go into the OpenAI playground and use these instructions for each model:
“Speak in an exaggerated, theatrical tone, reminiscent of a Shakespearean stage actor from the Elizabethan era. Emphasize every syllable with dramatic flair, rolling R’s and elongating vowels. Your cadence should rise and fall as if declaiming poetry Occasionally add chuckles, groans, or grunts of faux embarrassment.”
You’ll see that gpt-4o-mini-tts-2025-03-20 plays along and acts aa directed while gpt-4o-mini-tts-2025-12-15 ignores instructions and just speaks in a plain monotone style.
Please OpenAI, fix this issue BEFORE depreciating gpt-4o-mini-tts-2025-03-20.
I want to illustrate the issue. Here are two TTS generated audio files. The first is the 2025-03-20 and the second is the latest model.
TTS instcutions used:
Speak in an exaggerated, theatrical tone, reminiscent of a Shakespearean stage actor from the Elizabethan era. Emphasize every syllable with dramatic flair, rolling R’s and elongating vowels. Your cadence should rise and fall as if declaiming poetry Occasionally add chuckles, groans, or grunts of faux embarrassment.
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