{"name":"tengu_sunset_penguin_opus46","slug":"tengu-sunset-penguin-opus46","family":"flag","title":"Feature flags","noun":"feature flag","description":"Default `\"2026-06-29\"`. Date (parsed with `Date.parse`) on which Opus 4.6 fast mode is removed: when fast mode is turned on while the current model is `claude-opus-4-6` and the date is still in the future, Claude Code shows the warning `Opus 4.6 fast mode is deprecated and will be removed on <date>`, with the date formatted like `Jun 29` in UTC. An unparseable or past date shows no warning.","description_source":"code","described_by":{"bundle":"2.1.191","author":"claude-opus-5-5"},"presence":{"first_seen":"2.1.174","removed_in":"2.1.193","in_current_build":false,"newest_mined":"2.1.309","builds":14,"mined_builds":150,"first_cited":{"version":"2.1.174","released_at":"2026-06-11 22:27:52","spans":1}},"aliases":[],"entries":[{"version":"2.1.174","anchor":"opus-4-6-sunset-date-notification","heading":"Opus 4.6 Sunset Date Notification","line":null,"released_at":"2026-06-11 22:27:52","reason":"gate cited by this entry, found in this entry's text"}],"entries_total":1,"docs":[],"docs_total":0,"gates":[{"version":"2.1.174","state":"unknown","account":null,"baseline":null,"code_default":null}],"related":[{"name":"tengu_sunset_penguin_opus47","slug":"tengu-sunset-penguin-opus47","description":"Default `\"2026-07-25\"`. Removal date for Opus 4.7 fast mode: when fast mode is turned on (via `\/fast` or the picker) while the current model is `claude-opus-4-7` and the date is still in the future, a warning notice `Opus 4.7 fast mode is deprecated and will be removed on <date>` appears, with the date shown like `Jul 25` in UTC. An unparseable or past date shows no notice."}],"url":"https:\/\/changelogs.core-directive.com\/reference\/flag\/tengu-sunset-penguin-opus46","family_url":"https:\/\/changelogs.core-directive.com\/reference\/flag.json"}