PostModelSwitch
A Claude Code hook event, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.
After the session's model changes, including changes Claude Code makes on its own, such as restoring the model when you resume a session
Anthropic's own wording. Read off Hooks reference, captured 2026-11-11.
In the changelogs
3Releases whose published page names PostModelSwitch.
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v2.1.318
/clear keeps a record of tools used, and model-switch hooks can wait to start
/clear now saves a record of the tools used and undoes it if the clear fails, and PostModelSwitch hooks can be held back
found in this entry's text
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v2.1.260
PreModelSwitch/PostModelSwitch hook-load failures now give more actionable errors
Failed model-switch hook loads now give a specific, actionable error message.
found in this entry's text, named in this entry
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v2.1.251
New PreModelSwitch and PostModelSwitch hooks
New PreModelSwitch and PostModelSwitch hooks let you gate or annotate every model change.
named in this entry, found in this entry's text
First cited
1The earliest release whose published evidence quoted PostModelSwitch was v2.1.251, 28 Aug 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
0The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the hook event does. All hook events.