{"version":"2.1.219","anchor":"fast-mode-advertised-on-opus-5-in-the-environment-prompt","canonical_anchor":"fast-mode-advertised-on-opus-5-in-the-environment-prompt","heading":"Fast mode advertised on Opus 5 in the environment prompt","tier":"internal","area":"Models","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.219\/e\/fast-mode-advertised-on-opus-5-in-the-environment-prompt","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.219","markdown":"### Fast mode advertised on Opus 5 in the environment prompt\n\nClaude is now told Fast mode applies to Opus 5 as well as earlier models.\n\n**What**\n\nThe two environment-info prompt builders that describe Fast mode now list Opus 5 alongside 4.8 and 4.7, so the model is told Fast mode applies to the new default.\n\n**Details**\n\n- Applies to both environment-info prompt builders.\n- No gate; the line is emitted for everyone.\n\n**Evidence**\n\n`It can be toggled with \/fast and is available on Opus 5\/4.8\/4.7.`\n\n- Area: Models\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 0\/5"}