{"schema_version":"onlylabs.public_signal.v1","title":"Anthropic Writing: Claude Fable 5 Mythos 5","description":"Anthropic writing signal with public source context, captured evidence pages, related signals, and data-business radar classification.","url":"https://onlylabs.fyi/signals/2648db51-9d6a-42a9-aece-a0ca5f9ce64f","json_url":"https://onlylabs.fyi/signals/2648db51-9d6a-42a9-aece-a0ca5f9ce64f/signal.json","generated_at":"2026-06-10T07:04:34.035566+00:00","org":{"slug":"anthropic","name":"Anthropic","category":"frontier-lab","category_label":"Frontier lab","dossier_url":"https://onlylabs.fyi/labs/anthropic","dossier_json_url":"https://onlylabs.fyi/labs/anthropic/dossier.json"},"related_urls":{"signal":"https://onlylabs.fyi/signals/2648db51-9d6a-42a9-aece-a0ca5f9ce64f","signal_json":"https://onlylabs.fyi/signals/2648db51-9d6a-42a9-aece-a0ca5f9ce64f/signal.json","source":"https://www.anthropic.com/news/claude-fable-5-mythos-5","lab_dossier":"https://onlylabs.fyi/labs/anthropic","lab_dossier_json":"https://onlylabs.fyi/labs/anthropic/dossier.json","analysis":"https://onlylabs.fyi/analysis/anthropic","analysis_json":"https://onlylabs.fyi/analysis/anthropic/analysis.json","analysis_evidence_json":"https://onlylabs.fyi/analysis/anthropic/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":"Anthropic published Claude Fable 5 Mythos 5. This talking signal gives public context for research themes, product direction, policy, or launch framing. High-signal details: Creative post, not a major model release · Claude Fable 5 and Claude Mythos 5 \\ Anthropic Announcements Claude Fable 5 and Claude Mythos 5 Jun 9, 2026 Today we’re launching Claude Fable 5 : a Mythos-class 1 model.... onlylabs links this event to 1 captured evidence page and 6 related writing signals.","signal_desk":"talking","source_context":{"source_url":"https://www.anthropic.com/news/claude-fable-5-mythos-5","source_host":"anthropic.com","occurred_at":"2026-06-09T20:27:50+00:00","first_seen_at":"2026-06-10T07:01:05.666054+00:00","date_source":"sitemap.lastmod","context":null},"context_markers":[{"label":"Lab","value":"Anthropic","source":"signal"},{"label":"Signal desk","value":"talking","source":"signal"},{"label":"Source host","value":"anthropic.com","source":"source"},{"label":"Notability","value":"Creative post, not a major model release","source":"signal"},{"label":"Watch term","value":"RL environments","source":"evidence"},{"label":"Watch 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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/2648db51-9d6a-42a9-aece-a0ca5f9ce64f/signal.json","required":true},{"label":"source","url":"https://www.anthropic.com/news/claude-fable-5-mythos-5","required":true},{"label":"dossier_json","url":"https://onlylabs.fyi/labs/anthropic/dossier.json","required":true},{"label":"analysis_evidence_json","url":"https://onlylabs.fyi/analysis/anthropic/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, 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This talking signal gives public context for research themes, product direction, policy, or launch framing. 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It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research, and many other areas. The longer and more complex the task, the larger Fable 5’s lead over our other models. Releasing a model this capable comes with risks. Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused to cause serious damage. We’ve therefore launched the model with safeguards that mean queries on some topics will instead receive a response from our next-most-capable model, Claude Opus 4.8. To release the model both safely and quickly, we’ve tuned these safeguards conservatively—they’ll sometimes catch harmless requests, though they trigger, on average, in less than 5% of sessions. 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