🪦 Dead

Mistral Leanstral 1.5

Model deprecation · Model Deprecation · shut down September 30, 2026

Born
Died
Lifespan
3m 2d
Cause of death
Model Deprecation
Killed by
Mistral
Type
Model

Mistral's Lean 4 formal-proof model was retired on September 30, exactly as its own launch note promised: 'We released Leanstral 1.5... This model will be retired on September 30, 2026.' A 92-day advertised lifespan, announced in the same sentence as its birth, with no replacement named.

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Questions about Mistral Leanstral 1.5

Is Mistral Leanstral 1.5 dead?

Yes. Mistral Leanstral 1.5 was shut down on September 30, 2026, 3m 2d after its launch on June 30, 2026. The cause of death was model deprecation; it was killed by Mistral. Classification: model deprecation. Details and the source are above.

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