sandbox-agent/research.md

Research: Subagents

Summary of subagent support across providers based on current agent schemas and docs.

OpenCode

• Schema includes Part variants with type = "subtask" and fields like agent, prompt, and description.
• These parts are emitted via message.part.updated, which can be used to render subagent activity.

Codex

• Schema includes SessionSource with a subagent variant (e.g., review/compact), attached to Thread.source.
• This indicates the origin of a thread, not active subagent status updates in the event stream.

Claude

• CLI schema does not expose subagent events.
• The Task tool supports subagent_type, but it is not represented as a structured event; it may be inferred only from tool usage output.

Amp

• Schema has no subagent event types.
• Permission rules include context: "subagent" and delegate actions, but no event stream for subagent status.

Current universal behavior

• Subagent activity is normalized into the standard message/tool flow; no dedicated subagent fields yet.