Changes to Launch Subagents

removed the enum value claude_managed of the request property subagents/items/engine

removed the enum value pi of the request property subagents/items/engine

the engine request property default value pi was removed

request property subagents/items/engine list-of-types was widened by adding types null to media type application/json

added the new optional request property subagents/items/budget_usd

added the new optional request property subagents/items/engine

added the new optional request property subagents/items/page

added the new optional request property subagents/items/parent_harness_context/anyOf[subschema #1: ParentHarnessContext]/system_prompt_source

added the new optional request property peer_messaging

added the new optional request property subagents/items/inherit_context

added the new optional request property subagents/items/kind

added the new optional request property subagents/items/parent_harness_context