Under the hood
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Plugin host calls are now blocked if the hooks module behind them hasn't been fully admitted yet
What
A guard was added before Claude Code runs any host-provided $.* call originating from a plugin or hooks module. The call is now refused if the caller chain or its environment ID is still marked as not yet admitted, since plugin.register runs once per admitted set of plugins and a call from an unadmitted hooks module means that module isn't part of the built set yet.
Why
This prevents a plugin's hooks module from making host calls before it has actually been admitted into the running set, closing a window where such a call could otherwise slip through.
Names in the bundleplugin.register