{"version":"2.1.165","anchor":"subagent-sessions-identified-in-billing-attribution-header","canonical_anchor":"subagent-sessions-identified-in-billing-attribution-header","heading":"Subagent Sessions Identified in Billing Attribution Header","tier":null,"area":null,"scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.165\/e\/subagent-sessions-identified-in-billing-attribution-header","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.165","markdown":"### Subagent Sessions Identified in Billing Attribution Header\n\nThe `x-anthropic-billing-header` sent with every API request now includes `cc_is_subagent=true;` when the request originates from a subagent session rather than the top-level interactive session. The main CLI session is tagged `isMainSession: true` internally; any agent that lacks that flag gets the subagent marker appended.\n\nThis is an internal attribution change with no user-visible behavior. It helps Anthropic distinguish API usage generated directly by the user from usage generated by orchestrated subagents, which improves billing analytics and usage reporting.\n\n**Evidence**\n\nAttribution header builder now appends `cc_is_subagent=true;` for non-main-session callers (search for `\"cc_is_subagent=true;\"` in the source); main session agent config now sets `isMainSession: !0`."}