You'll notice
Useful3 Signal2
When fast mode can't toggle, the message says whether it timed out, was refused, or the model changed.
What's wrong with this entry?
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What
When fast mode cannot be turned on or off, the message now says which of the three causes applied: a timeout, an explicit refusal, or the model changing while hooks that run before a model switch were still executing.
Evidence
Fast mode was not ${o}: the model changed while PreModelSwitch hooks ran; try again
Strings lifted out of the shipped bundle, so the claim above can be checked against them.