On an organization, team, project or key, the narrowest winning: llmgw ctl kb default, POST /api/v1/kb/defaults, and the console's Knowledge screen. A request's own X-Llmgw-Knowledge overrides it and none turns it off. A default never refuses a request: a collection the caller cannot read is left out, and a failed search answers without passages. Removing a collection takes it out of every default. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>