Summary

Fix subagent completion delivery so completion announcements route back to the original requester session/conversation instead of leaking into the child agent's bound external window/account.

Problem

We hit a real Telegram routing bug in cross-agent subagent runs:

• main/default spawned a subagent targeting another agent (for example novel-agent)
• the child session correctly rebound to the target agent's own delivery context/window
• but the later completion announcement sometimes followed that child-bound route
• result: the completion marker appeared in the project bot window instead of the original main/default chat

This was reproduced in real Telegram live validation, not just tests.

Root cause

There were two routing mistakes that compounded:

1. In src/agents/subagent-spawn.ts, the registry stored requesterOrigin from the child-side delivery context (childSessionOrigin) instead of preserving the original requester route.

   • That meant completion delivery later reused a target-agent/project-bot account as if it were the requester return path.

2. In src/agents/subagent-announce-delivery.ts, completion delivery routing resolved bound destinations using params.childSessionKey and allowed non-fail-closed fallback.

   • That let completion delivery prefer the child session's external binding, or a stray single bound destination, instead of the requester/orchestrator session.

Fix

src/agents/subagent-spawn.ts

• preserve requesterOrigin from the incoming requester context
• compute childSessionOrigin separately via resolveRequesterOriginForChild(...)
• keep thread-binding / child agent delivery on childSessionOrigin
• register subagent runs with the original requesterOrigin
• merge thread binding delivery back into childSessionOrigin, not requesterOrigin

src/agents/subagent-announce-delivery.ts

• resolve completion delivery bindings against params.requesterSessionKey
• set failClosed: true for completion delivery routing

src/agents/subagent-spawn.thread-binding.test.ts

• update expectations to match the corrected split:
  • child delivery uses the child/target-agent route
  • registry requester origin stays on the original requester route

Validation

Automated

Ran targeted agent tests:

npx vitest --config test/vitest/vitest.agents.config.ts run \
  src/agents/subagent-spawn.thread-binding.test.ts \
  src/agents/subagent-spawn.test.ts

Observed passing results on the final minimal patch.

Live verification

We also validated with real Telegram routing using a novel-agent subagent completion marker flow:

• spawn subagent from main/default
• child replies with a unique marker line only
• observe where the completion marker actually lands in Telegram

The final minimal patch correctly delivered the completion back to the original main/default conversation instead of the Novel bot window.

Why this change is minimal

This PR intentionally keeps only the production fixes plus the single necessary thread-binding expectation update. Extra helper changes and regression-only scaffolding used during investigation were removed before preparing the PR.