Objective

Add durable agent bindings and invocations, then prove a child conversation can execute independently through the shared conversation worker without model-facing tools.

Scope

• Add a stable agent binding for named continuity and execution policy.
• Add a durable invocation for each delegated task, including input, lifecycle, terminal result, and parent-notification state.
• Create or reuse a child conversation with immutable parentConversationId lineage.
• Allow child conversation work to be runnable without a conversation-level provider delivery destination; the invocation supplies bounded execution authority and an internal result target.
• Enqueue invocation input as stable child mailbox work.
• Run the child through the same lease, start/resume decision, session records, execution slices, terminalization, and recovery workflow proven by Unify new and resumed turns in the conversation worker #876 and Migrate agent dispatch onto the conversation worker #882.
• Persist one terminal invocation result; parent delivery is added in Deliver subagent results through a durable parent outbox #878.
• Keep recursive delegation disabled.

Completion

• Named bindings may reuse one isolated child conversation; ephemeral work creates a new child conversation.
• Every invocation has a stable id used as, or to derive, the mailbox idempotency key.
• Child work survives execution-slice timeout, worker loss, queue redelivery, and missing wake-ups.
• Destinationless child conversation work can be woken, leased, started, and resumed through the normal conversation queue.
• Parent completion or idleness does not cancel the child.
• One invocation produces at most one durable terminal result.
• Child authority, credentials, tools, visibility, and workspace scope do not exceed the parent-provided bounds.
• The proof works without model-facing spawn/result tools.