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claude-code - 💡(How to fix) Fix `/fast` toggle off leaves model on Opus 4.6 instead of restoring default (4.7) [1 participants]

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anthropics/claude-code#56022•Fetched 2026-05-05 06:00:12
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Root Cause

Related: #44819 (VS Code model picker not updating on fast mode switch — different surface, possibly shared state-management root cause).

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Preflight Checklist

  • I have searched existing issues and this hasn't been reported yet
  • This is a single bug report
  • I am using the latest version of Claude Code

What's Wrong?

Toggling /fast on then off leaves the session on Opus 4.6 instead of restoring the default model (Opus 4.7). Opus 4.6 is not available as a selection in /model, so the user ends up on a model they cannot normally choose.

What Should Happen?

Either:

  • /fast off restores the model that was active before /fast was toggled on, or
  • Opus 4.6 is available as a /model selection, so the post-fast state is reachable through normal UI

Currently /fast off puts the user on a model (Opus 4.6 non-fast) that cannot be selected via /model.

Steps to Reproduce

  1. Launch Claude Code on Claude Max 20x (default model: Opus 4.7)
  2. Run /model — confirms Opus 4.7 (1M context) (default). Note: Opus 4.6 is not listed as a choice
  3. Run /fast — fast mode ON, model switches to Opus 4.6
  4. Run /fast — fast mode OFF
  5. Check status bar → shows Model: Opus 4.6 (1M context)

Expected at step 5: Model restored to Opus 4.7 (the default) Actual at step 5: Model stuck on Opus 4.6 — a model not available via /model

Additionally, the model's system prompt metadata still claims Opus 4.7 after step 5, so the model self-reports as 4.7 when asked, contradicting the status bar.

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.126

Platform

Claude Max 20x

Operating System

Linux (Kubuntu, 6.19.4)

Terminal/Shell

bash

Additional Information

Since Opus 4.6 is not a /model selection, /fast on→off is currently the only way to land on it — making this both a bug (wrong model restored) and an unintended state (model not normally reachable through the UI).

Related: #44819 (VS Code model picker not updating on fast mode switch — different surface, possibly shared state-management root cause).

extent analysis

TL;DR

The most likely fix involves updating the model restoration logic when toggling /fast off to ensure it reverts to the default model, Opus 4.7, instead of staying on Opus 4.6.

Guidance

  • Review the code handling the /fast toggle to identify why it's not restoring the previous model correctly.
  • Verify that the model selection logic is correctly updating the internal state when /fast is toggled on and off.
  • Check for any inconsistencies in how the model is reported (e.g., status bar vs. system prompt metadata) to ensure a unified model state representation.
  • Consider adding Opus 4.6 as a selectable model via /model to prevent unintended states, or ensure that /fast off always reverts to a selectable model.

Example

No specific code example can be provided without access to the Claude Code base, but the fix likely involves modifying the logic that handles the /fast toggle to correctly restore the previous model state.

Notes

The issue might be related to a shared state management problem, as hinted by the reference to #44819. Solving this issue may require a deeper look into how model states are managed across different features.

Recommendation

Apply a workaround by manually selecting the default model (Opus 4.7) after toggling /fast off, until a permanent fix can be implemented to correctly restore the model state.

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claude-code - 💡(How to fix) Fix `/fast` toggle off leaves model on Opus 4.6 instead of restoring default (4.7) [1 participants]