{"schema_version":"onlylabs.public_signal.v1","title":"Mistral AI Writing: Leanstral 1.5: Proof Abundance for All","description":"Mistral AI writing signal with public source context, captured evidence pages, related signals, and data-business radar classification.","url":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba","json_url":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba/signal.json","generated_at":"2026-07-26T22:25:34.658Z","evidence_latest_fetched_at":"2026-07-03T16:02:38.822579+00:00","signal_first_seen_at":"2026-07-03T16:00:52.322772+00:00","org":{"slug":"mistral","name":"Mistral AI","category":"frontier-lab","category_label":"Frontier lab","dossier_url":"https://onlylabs.fyi/labs/mistral","dossier_json_url":"https://onlylabs.fyi/labs/mistral/dossier.json"},"related_urls":{"signal":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba","signal_json":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba/signal.json","source":"https://mistral.ai/news/leanstral-1-5/","lab_dossier":"https://onlylabs.fyi/labs/mistral","lab_dossier_json":"https://onlylabs.fyi/labs/mistral/dossier.json","analysis":"https://onlylabs.fyi/analysis/mistral","analysis_json":"https://onlylabs.fyi/analysis/mistral/analysis.json","analysis_evidence_json":"https://onlylabs.fyi/analysis/mistral/evidence.json","category":"https://onlylabs.fyi/frontier","category_json":"https://onlylabs.fyi/frontier.json","category_feed":"https://onlylabs.fyi/frontier/feed.xml","category_signals_json":"https://onlylabs.fyi/signals.json","topic":"https://onlylabs.fyi/topics/talking","topic_signals_json":"https://onlylabs.fyi/topics/talking/signals.json","topic_feed":"https://onlylabs.fyi/topics/talking/feed.xml","data_business":null},"answer_pack":{"answer":"Mistral AI published Leanstral 1.5: Proof Abundance for All. This talking signal gives public context for research themes, product direction, policy, or launch framing. High-signal details: Low traction, likely routine post. · Leanstral 1.5: Proof Abundance for All Research Leanstral 1.5: Proof Abundance for All July 2, 2026 By Leanstral Team at Mistral AI Back to Blog 6 min read Share this.... onlylabs links this event to 1 captured evidence page and 6 related writing signals.","signal_desk":"talking","source_context":{"source_url":"https://mistral.ai/news/leanstral-1-5/","source_host":"mistral.ai","occurred_at":"2026-07-02T13:55:54+00:00","first_seen_at":"2026-07-03T16:00:52.322772+00:00","date_source":"rss.item_date","context":null},"context_markers":[{"label":"Lab","value":"Mistral AI","source":"signal"},{"label":"Signal desk","value":"talking","source":"signal"},{"label":"Source host","value":"mistral.ai","source":"source"},{"label":"Notability","value":"Low traction, likely routine post.","source":"signal"},{"label":"Watch term","value":"RL environments","source":"evidence"},{"label":"Watch term","value":"Eval 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narrative layer over raw signals and helps identify which frontier-lab priorities are becoming externally legible.","required_sources":[{"label":"signal_json","url":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba/signal.json","required":true},{"label":"source","url":"https://mistral.ai/news/leanstral-1-5/","required":true},{"label":"dossier_json","url":"https://onlylabs.fyi/labs/mistral/dossier.json","required":true},{"label":"analysis_evidence_json","url":"https://onlylabs.fyi/analysis/mistral/evidence.json","required":true},{"label":"topic_signals_json","url":"https://onlylabs.fyi/topics/talking/signals.json","required":false},{"label":"data_radar_json","url":null,"required":false}],"expected_output":["one-paragraph source-grounded interpretation","category-specific implication","confidence and missing evidence","recommended next source to inspect"],"prompt_seed":"Using only the linked onlylabs JSON, captured source context, and cited evidence, analyze Mistral AI's 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host","object":"mistral.ai","text":"Leanstral 1.5: Proof Abundance for All has source host mistral.ai."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has lab","object":"Mistral AI","text":"Leanstral 1.5: Proof Abundance for All has lab Mistral AI."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has signal desk","object":"talking","text":"Leanstral 1.5: Proof Abundance for All has signal desk talking."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has source host","object":"mistral.ai","text":"Leanstral 1.5: Proof Abundance for All has source host mistral.ai."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has notability","object":"Low traction, likely routine post.","text":"Leanstral 1.5: Proof Abundance for All has notability Low traction, likely routine post.."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has watch term","object":"RL environments","text":"Leanstral 1.5: Proof Abundance 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This talking signal gives public context for research themes, product direction, policy, or launch framing. High-signal details: Low traction, likely routine post. · Leanstral 1.5: Proof Abundance for All Research Leanstral 1.5: Proof Abundance for All July 2, 2026 By Leanstral Team at Mistral AI Back to Blog 6 min read Share this.... onlylabs links this event to 1 captured evidence page and 6 related writing signals.","semantic_triples":[{"subject":"Mistral AI","predicate":"published","object":"Leanstral 1.5: Proof Abundance for All","text":"Mistral AI published Leanstral 1.5: Proof Abundance for All."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"is classified as","object":"writing signal","text":"Leanstral 1.5: Proof Abundance for All is classified as writing signal."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"belongs to","object":"talking desk","text":"Leanstral 1.5: Proof Abundance for All belongs to talking desk."},{"subject":"Leanstral 1.5: Proof Abundance for All","predicate":"has evidence coverage","object":"1 captured evidence page","text":"Leanstral 1.5: Proof Abundance for All has evidence coverage 1 captured evidence page."}]},"signal":{"id":"1a07786f-a0ba-4f85-994e-0844b256eaba","url":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba","json_url":"https://onlylabs.fyi/signals/1a07786f-a0ba-4f85-994e-0844b256eaba/signal.json","source_url":"https://mistral.ai/news/leanstral-1-5/","title":"Leanstral 1.5: Proof Abundance for All","summary":"Mistral AI published a writing signal. onlylabs watches public writing for research themes, product direction, and model-launch context.","context":null,"kind":{"key":"post_published","label":"Writing"},"org":{"slug":"mistral","name":"Mistral AI","category":"frontier-lab"},"occurred_at":"2026-07-02T13:55:54+00:00","first_seen_at":"2026-07-03T16:00:52.322772+00:00","date_source":"rss.item_date","evidence_coverage":{"target_pages":1,"captured_pages":1,"readable_pages":1,"capture_methods":["plain"],"missing_page_urls":[],"failed_page_urls":[],"blocked_page_urls":[],"page_urls":["https://mistral.ai/news/leanstral-1-5/"]},"facets":{},"traction":{"github_stars":null,"hn_points":6,"hn_comments":1,"hn_story_id":"48775384","hf_downloads":null,"hf_likes":null},"data_radar":null},"primary_evidence_page":{"is_primary":true,"source_match":true,"url":"https://mistral.ai/news/leanstral-1-5/","final_url":"https://mistral.ai/news/leanstral-1-5/","title":"Leanstral 1.5: Proof Abundance for All","http_status":200,"content_type":"text/html; charset=UTF-8","capture_method":"plain","fetched_at":"2026-07-03T16:02:38.822579+00:00","bytes":242561,"raw_path":"1929444a4216300742aa7054989f6fe7c4c6224c580b4d8746c871fbff87114c.html","content_hash":"b79b01a839b8d04160982265d0e0ad017941259d53eca3d10a6bbf46f170d6c4","excerpt_chars":1200,"truncated":true,"excerpt":"Leanstral 1.5: Proof Abundance for All Research Leanstral 1.5: Proof Abundance for All July 2, 2026 By Leanstral Team at Mistral AI Back to Blog 6 min read Share this post Copy url to clipboard Copied Thinking Summary Leanstral 1.5, a free Apache-2.0 licensed model with 6B active parameters, delivers a major performance upgrade in formal verification, saturating miniF2F, solving 587/672 PutnamBench problems, and achieving state-of-the-art results on FATE-H (87%) and FATE-X (34%). Trained through mid-training, supervised fine-tuning, and reinforcement learning with CISPO, it excels in agentic proof engineering and real-world code verification, uncovering 5 previously unknown bugs across 57 repositories tested. Fully open-sourced and available via Hugging Face and a free API, Leanstral 1.5 is now accessible for practical proof engineering in Lean 4. Since its launch, Leanstral has offered an open, practical approach to proof engineering in Lean 4 . Today, we are releasing Leanstral 1.5 , a free Apache-2.0 licensed model with 119B total and only 6B active parameters, delivering a performance upgrade that makes formal verification more powerful and accessible than ever. 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