What
The permission mode decides how much Claude Code asks you before it acts. When the mode is switched, Claude Code now checks again, at the moment of applying it, that the switch is still allowed given the current state. If it is not, the switch is refused instead of applied. The step that announces the mode change now runs only when the switch succeeds.
Why
Before, a switch decided on out-of-date information could still be applied after things had changed. Now it is turned down, so the mode you end up in matches the current state.
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not clear which of the ways you can change permission mode go through this check.