Anthropic will remove Opus 4.8 fast mode on November 30. Claude Code users can move to Opus 5.5 or keep 4.8 at standard speed.
If Claude Code still starts with Opus 4.8 and fast mode enabled, check both settings before November 30, 2026. In the Claude Code 2.1.316 release notes, Anthropic says those requests will return an error after removal, without falling back to standard speed. The notice concerns fast mode; it does not announce the retirement of Opus 4.8 itself.
To keep fast mode, Anthropic's documentation directs users to select Opus 5.5 through /model, using Claude Code 2.1.280 or later. To keep Opus 4.8 at standard speed, run /fast off. These are vendor-documented migration paths, which NODVIEW has not executed. An error after the deadline should not be expected to choose a path for you.
A change in the current window needs a fresh-session check. The model configuration documentation says /model saves the choice in user settings. In the /model picker, Enter switches and saves, while s changes only the current session. A startup --model argument, ANTHROPIC_MODEL, or project settings can explain why another session returns to the old model. Check the model actually selected after restarting, rather than relying only on the earlier switch confirmation.
A useful migration record contains the Claude Code version, the model and fast-mode state before the change, the chosen path, and the state in a new session afterward. If that session returns to 4.8 with fast mode enabled, investigate the model-selection source and the saved toggle separately. This distinguishes a temporary switch from a corrected startup configuration. It does not establish that another model will handle your workload equally well.
Fast mode also has separate pricing and access conditions. At review time, the documentation lists Opus 5.5 fast mode at $8 per million input tokens and $40 per million output tokens. For Claude Code subscriptions, it uses usage credits rather than included limits. Check current rates and organization access on the fast-mode page before changing the setup; NODVIEW has not measured speed or spending.