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Leanstral 1.5

Mistral · Devstral & Leanstral line · coding · open weights

Released July 2, 2026Latest in the line

What changed

Apache 2.0 model for Lean 4 proof engineering with 119B parameters and 6B active, solving 587 of 672 PutnamBench problems.

Sources: Mistral · Hugging Face

Where the Devstral & Leanstral line stands

Leanstral 1.5 is the current model in this line. The card shows how long it has been since the last release against the line's usual gap and its recent ones — the rhythm, not a date.

Leanstral 1.5

Mistral · Devstral & Leanstral line · coding · open weights
Mid-cycle69 of ~108 days into its usual cycle
Released Jul 2, 2026 · what changed →
Days since last release
Leanstral 1.5 · Jul 2, 2026
69
days
Usual gap
108
days
Recent gaps
Leanstral 1.5 · Jul 2026
108
Leanstral · Mar 2026
97
Devstral 2 · Dec 2025
202

Every Devstral & Leanstral release

Newest first. See the full line with every card →

  1. Jul 2, 2026Leanstral 1.5 · this page
  2. Mar 16, 2026Leanstral
  3. Dec 9, 2025Devstral 2
  4. May 21, 2025Devstral

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