Mistral AI retired two models on September 30, 2026: OCR 4.0 (mistral-ocr-4-0) and the experimental Leanstral 1.5 (labs-leanstral-1-5). The Mistral changelog entry dated September 29 deprecated both and set retirement for the following day, and the models overview now lists them under “Deprecated & retired models.”
For OCR 4.0, Mistral names OCR 4.1 as the replacement and tells developers to use mistral-ocr-4-1 or mistral-ocr-latest. Leanstral 1.5 has no successor in the table.
On this page
The two retirements
| Model | API name | Released | Deprecated | Retired | Alternative listed by Mistral |
|---|---|---|---|---|---|
| OCR 4.0 | mistral-ocr-4-0 | June 23, 2026 | September 29, 2026 | September 30, 2026 | OCR 4.1 |
| Leanstral 1.5 | labs-leanstral-1-5 | June 30, 2026 | September 29, 2026 | September 30, 2026 | None |
Release dates are from Mistral’s model pages for OCR 4.0 and Leanstral 1.5.
OCR 4.0: one day’s notice, but the aliases moved in July
The formal deprecation notice for OCR 4.0 came one day before shutdown. The general model names had changed much earlier. When Mistral released OCR 4.1 on July 16, its changelog said that mistral-ocr-latest and mistral-ocr-4 “now point to it.” OCR 4.1 became generally available on August 31.
So the retirement mainly affects code that called the dated name mistral-ocr-4-0 directly. Mistral describes OCR 4.1 as its latest OCR service, with “paragraph-level bounding boxes, structural block labels, and block-level confidence scores.” The block-level confidence scores are what OCR 4.1 adds over OCR 4.0, whose model page lists bounding boxes and block labels. OCR 3 stays available for existing integrations, according to the models overview.
Leanstral 1.5: retirement set at launch
Leanstral 1.5 was a Mistral Labs release: an experimental model for formal proof engineering in the Lean 4 language. Its short life was planned. The changelog entry for its June 30 release already said the model “will be retired on September 30, 2026,” and the September 29 notice confirmed that date. Mistral’s model page now says the model “is deprecated and is being phased out.”
What developers should check
- Code that calls
mistral-ocr-4-0by name must switch tomistral-ocr-4-1ormistral-ocr-latest. - Code using
labs-leanstral-1-5has no direct API replacement listed by Mistral.
Retired and current models are tracked in our AI model release timeline, including the entries for Mistral OCR 4.0, Mistral OCR 4.1 and Leanstral 1.5. Another retirement from the same week is xAI’s grok-voice-transcribe-1.0, and more are in AI model news.
