Fast mode handles models that reject it, with a notice when it falls back

What

Fast mode makes Claude respond faster on models that support it. This release changes what happens when the model in use does not accept it.

• When fast mode is rejected for a fallback model (a model used in place of the one you picked), Claude Code remembers this for the session and uses standard speed for that model. The fast mode state and the labels in the model picker now check this model by model.
• A warning appears straight away: "Using standard speed on · fast mode wasn't available". Before, the switch to standard speed was not announced.
• In remote sessions, a report that fast mode is off because of model_not_allowed is now ignored instead of changing the fast mode state.
• When a controlling program sets fastMode to true through apply_flag_settings and the model changes too, or the current settings disagree, a fast mode check now runs after the settings are applied. Before, it only replied to the request.

Why

If your model cannot use fast mode, you now see why Claude Code dropped to standard speed, and it stops retrying fast mode for that model during the session.