{"version":"2.1.280","anchor":"fast-mode-no-longer-restricted-to-opus-548-in-the-system-p","canonical_anchor":"fast-mode-no-longer-restricted-to-opus-548-in-the-system-p","heading":"Fast mode no longer restricted to Opus 5\/4.8 in the system prompt","tier":"notice","area":"Models","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.280\/e\/fast-mode-no-longer-restricted-to-opus-548-in-the-system-p","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.280","markdown":"### Fast mode no longer restricted to Opus 5\/4.8 in the system prompt\n\nThe system prompt no longer says fast mode is limited to Opus 5\/4.8, and now lists Opus 5.5 in the model catalog\n\n**What**\n\nThe system prompt Claude Code sends to the model describes fast mode, a setting toggled with `\/fast` that makes Claude Opus respond faster. Previously the prompt said fast mode \"is available on Opus 5\/4.8\"; that restriction has been dropped, and the prompt now just says it can be toggled with `\/fast`. The model catalog line in the same prompt now lists `claude-opus-5-5` (Opus 5.5) where it used to list `claude-opus-5`.\n\n**Why**\n\nDropping the model-restriction wording means the model is no longer told fast mode only works on specific Opus versions, in step with the newly listed Opus 5.5 model.\n\n- Area: Models\n- Names: `\/fast`, `claude-opus-5-5`\n- Tier: You'll notice\n- Useful: 4\/5\n- Signal: 4\/5"}