explore_tool_action tool call — a read-only codebase
exploration action (e.g. codebase_search, read_file, grep_search)
surfaced to the user.
Discriminated by the required explore_tool_name field: only
explore_tool_action events carry cognition.ai/exploreToolName. It is a
non-Option String with no #[serde(default)], so serde’s untagged enum
dispatch only picks this variant when the incoming _meta actually has
cognition.ai/exploreToolName. Mirrors the pattern used by
ReportBlockerMeta and CognitionRecordingStoppedMeta.