Subagent Orchestration Plugin (migrated from Pi ecosystem subagent/).

Adds the delegate_subagent tool. A call starts a child conversation with its own model loop and its own context window, and returns at once. Pass tasks to start several children.

Flow

1. The tool creates the children and one pi.subagent task per child (owned by the parent's running task), enqueues one SuperPi.Workers.SubagentWorker job per child, puts the parent task in waiting (TaskEngine.wait_for_children/4) and returns an acknowledgement that names the children. Its control directive %{"await" => ...} tells the machine to park.
2. The parent's machine parks in :awaiting_children. It still answers cancel, get_state and compact. The children run on any node of the cluster, under the :subagents queue limit.
3. When every child has ended (wait_policy: "all"), or at once when one fails (wait_policy: "fail_fast"), the parent wakes. The machine appends one message per child with its summary and the turn goes on. The model sees the summaries as new messages in its next request, not as the result of the tool call.

What a child gets

• Its own durable conversation (owner_kind: "task", owned by the parent's running task), so the work is recorded and inspectable.
• The parent's model, workspace and settings, and a system prompt for its role.
• Never more permission than the parent. The roles scout, planner, reviewer and researcher run the Planner harness: plan mode with read-only tools. A worker runs the Code harness in the parent's execution mode. Permission settings and dangerouslySkipPermissions are copied, not raised.
• No delegate_subagent, ask_question or handoff tools: a child cannot spawn children beyond config :super_pi, subagent_max_depth (default 1) and has no human to ask.

Limits

• Children use the same provider and credentials as the parent. There is no separate budget.
• A child ends at the timeout (timeout_ms, default config :super_pi, subagent_timeout_ms = 120 s, counted from the start of its job) and is then failed and stopped.
• session.cancel on the parent aborts the whole subtree: the children's tasks are aborted and their machines stop.
• One delegation at a time: a second call while children run is refused. Give all tasks in one call (tasks).
• Only the child's final text returns to the parent, not its intermediate steps. It is cut at 8000 bytes.

Events

subagent_started when a child's job begins, subagent_finished when its task settles. Both go to the parent conversation.

Tests

config :super_pi, :subagent_machine_opts is merged into every child machine's options (an llm_responder). Oban runs in testing: :manual there: drain the :subagents queue to run the children.