What
The "Switch model?" and "Change effort level?" dialogs now show a hook-supplied message, "A PreModelSwitch hook asked you to confirm", in place of the usual prompt-caching warning.
Details
- Only when a hook supplies a reason; otherwise the caching-warning text is shown as before.
Evidence
A PreModelSwitch hook asked you to confirm
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundlePreModelSwitch
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up PreModelSwitch, on Hooks reference.
| PreModelSwitch | `hookSpecificOutput` or top-level `decision` | `permissionDecision` (allow/deny/ask), `permissionDecisionReason`. `decision: "block"` also [cancels the switch](#premodelswitch-decision-control) |hooks see the edit
Two sources agreeTwo things we can check say the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up PreModelSwitch, on Hooks reference.
Anthropic's release notes agree
Added PreModelSwitch and PostModelSwitch hook events (block, confirm, or annotate a model switch); SessionStart resume hooks now receive…