{"slug": "leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4", "title": "Leanstral 1.5: ICYMI: Mistral released Leanstral 1.5, a SOTA open model for Lean 4 proof engineering. > Developers use Lean 4 as a general-purpose functional language (for CLI tools and libraries)…", "summary": "Mistral AI has not yet released Leanstral 1.5, a state-of-the-art open model for Lean 4 proof engineering, despite a social media post suggesting otherwise. The model is designed to help developers verify properties of code, protocols, and algorithms using Lean 4 as both a functional language and proof assistant. OutYet.ai continues to monitor Mistral AI's official channels for the release.", "body_md": "[Mistral AI](/providers/mistral-ai)Leanstral 1.5\n\n# Is Leanstral 1.5 out yet?\n\nNo.\n\n## When is Leanstral 1.5 coming out?\n\nLeanstral 1.5 is not out yet. There is no announced date yet, and no firm estimate. OutYet.ai rechecks Mistral AI's official release surfaces every minute and flips this page the moment access goes live. Last checked Jul 4, 2026.\n\nOne click creates your free account (or signs you into an existing one) and turns on alerts for Leanstral 1.5. There's no password to set, and you can unsubscribe any time.\n\nLast checked just now\n\nCrowd estimate\n\nNo guesses yet. Cast the first one below.\n\nPick your release guess\n\nCommunity consensus\n\nAn AI summary of the public comments here. Not a sourced fact.\n\nNot enough public feedback yet to summarize. Add a comment to help build the picture.\n\n[Compare Leanstral 1.5 with another model →](/compare?models=leanstral-1-5)\n\nAlso waiting on: [ChatGPT 5.6](/models/chatgpt-5-6), [Gemini 3.5 Pro](/models/gemini-3-5-pro), [Claude Fable 5.1](/models/claude-fable-5-1), [Claude Mythos 5.1](/models/claude-mythos-5-1)\n\n## Comments\n\nMissing a model, or wishing OutYet did something it doesn't? [Tell us what to build](/submit).", "url": "https://wpnews.pro/news/leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4", "canonical_source": "https://outyet.ai/models/leanstral-1-5", "published_at": "2026-07-04 00:00:00+00:00", "updated_at": "2026-07-04 13:57:56.993853+00:00", "lang": "en", "topics": ["ai-tools", "ai-research", "large-language-models"], "entities": ["Mistral AI", "Leanstral 1.5", "Lean 4", "OutYet.ai"], "alternates": {"html": "https://wpnews.pro/news/leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4", "markdown": "https://wpnews.pro/news/leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4.md", "text": "https://wpnews.pro/news/leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4.txt", "jsonld": "https://wpnews.pro/news/leanstral-1-5-icymi-mistral-released-leanstral-1-5-a-sota-open-model-for-lean-4.jsonld"}}