{"name":"claude-mythos-5-1","slug":"claude-mythos-5-1","family":"model","title":"Models","noun":"model","description":"A claude-fable-5-1 model id is recognized and becomes the fable family default, with UI text updated to Fable 5.1.","description_source":"entry","described_by":{"version":"2.1.257","anchor":"fable-51-model-introduced"},"presence":{"first_seen":null,"removed_in":null,"in_current_build":false,"newest_mined":"2.1.322","builds":0,"mined_builds":161,"first_cited":{"version":"2.1.257","released_at":"2026-09-01 17:15:33","spans":1}},"aliases":[],"entries":[{"version":"2.1.257","anchor":"fable-51-model-introduced","heading":"Fable 5.1 model introduced","line":"A claude-fable-5-1 model id is recognized and becomes the fable family default, with UI text updated to Fable 5.1.","released_at":"2026-09-01 17:15:33","reason":"found in this entry's text, named in this entry"},{"version":"2.1.257","anchor":"new-model-mythos-51-added-to-model-registry","heading":"New model: Mythos 5.1 added to model registry","line":"Mythos 5.1 joins the model catalog with a 1M context window and effort levels up to max.","released_at":"2026-09-01 17:15:33","reason":"found in this entry's text, named in this entry"},{"version":"2.1.257","anchor":"fable-5-branding-shortened-to-fable-in-usage-limit-messa","heading":"'Fable 5' branding shortened to 'Fable' in usage-limit messages","line":"Usage-limit text now says Fable limit, and fable-5-1 and mythos-5-1 aliases were added.","released_at":"2026-09-01 17:15:33","reason":"found in this entry's text"}],"entries_total":3,"docs":[{"source":"api","path":"about-claude\/model-deprecations","title":"model-deprecations","documented":false},{"source":"api","path":"agents-and-tools\/agent-skills\/overview","title":"PDF Processing","documented":false},{"source":"api","path":"agents-and-tools\/mcp-connector","title":"mcp-connector","documented":false},{"source":"api","path":"agents-and-tools\/mcp-tunnels\/overview","title":"overview","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/advisor-tool","title":"advisor-tool","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/bash-tool","title":"bash-tool","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/browser-use-sdk","title":"browser-use-sdk","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/browser-use-tool","title":"browser-use-tool","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/code-execution-tool","title":"code-execution-tool","documented":false},{"source":"api","path":"agents-and-tools\/tool-use\/computer-use-tool","title":"computer-use-tool","documented":false}],"docs_total":12,"gates":[],"related":[{"name":"claude-mythos-5","slug":"claude-mythos-5","description":"The model picker now colours Fable 5, Mythos 5 and Sonnet 5 in its list."},{"name":"claude-mythos-5-2","slug":"claude-mythos-5-2","description":"Claude Code now knows claude-fable-5-2 and claude-mythos-5-2, accepts the short names `fable-5-2` and `mythos-5-2`, and lists Fable 5.2 as latest"}],"url":"https:\/\/changelogs.core-directive.com\/reference\/model\/claude-mythos-5-1","family_url":"https:\/\/changelogs.core-directive.com\/reference\/model.json"}