You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
PermissionsArea: what it touches
ImprovementsKind: in v2.1.323,
ImprovementsSection of the release
Unclear It is not known which sessions run this security hook, so it may not apply to every setup.
What
permissions.deny is the setting that lists tool uses Claude must refuse. A built-in security hook (a check Claude Code runs on the list of available tools) now removes any tool matching those rules from that list. That includes rules that block every tool from one MCP server, an add-on that supplies extra tools. It does this whether the step before it succeeded or failed. If the settings cannot be read, it reports "sec-default could not read the tool list".
Why
Tools you have denied no longer slip back into the list through this hook.
