What
Plugins can hook into the step where Claude Code describes each tool to Claude. The built-in sec-default plugin is meant only to pass that step along unchanged.
Claude Code now checks that the sec-default plugin did not change a tool's description or whether the tool is deferred (held back until needed). If it did, Claude Code logs an error and reports it. Previously a hook could change a description with no check.
The check that decides whether a hook runs now also takes the kind of event into account.
Why
This guards the plugin system: a built-in plugin that unexpectedly rewrites how tools are described is now caught and recorded.
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 what the new per-event input to the hook check changes in practice.