diff --git a/tests/tools/test_delegate_capacity_interrupt.py b/tests/tools/test_delegate_capacity_interrupt.py
new file mode 100644
index 0000000000..071cc81343
--- /dev/null
+++ b/tests/tools/test_delegate_capacity_interrupt.py
@@ -0,0 +1,304 @@
+"""A rejected background batch retains synchronous cancellation ownership."""
+
+from __future__ import annotations
+
+import json
+import queue
+import threading
+import time
+from concurrent.futures import Future
+from types import SimpleNamespace
+
+import pytest
+
+from agent.interrupt_control import InterruptControlMixin
+from agent.turn_context import _bind_interrupt_scope
+from tools import async_delegation
+from tools.delegate_tool_dispatch import _Batch, _dispatch_background
+from tools.interrupt import is_interrupted, set_interrupt
+from tools.process_registry import process_registry
+
+
+class _Parent(InterruptControlMixin):
+    def __init__(self):
+        self.session_id = "capacity-interrupt-parent"
+        self._active_children = []
+        self._active_children_lock = threading.Lock()
+        self._execution_thread_id = None
+        self._interrupt_requested = False
+        self._hard_interrupt_requested = threading.Event()
+        self.quiet_mode = True
+
+
+class _ControlledChild(_Parent):
+    """Replace model work while retaining real interrupt and worker-start semantics."""
+
+    def __init__(self):
+        super().__init__()
+        self.session_id = "capacity-interrupt-child"
+        self._delegate_role = "leaf"
+        self._delegate_depth = 1
+        self._delegate_saved_tool_names = []
+        self._credential_pool = None
+        self._subagent_id = None
+        self.tool_progress_callback = None
+        self.model = "test-model"
+        self.started = threading.Event()
+        self.stop_received = threading.Event()
+        self.unwinding = threading.Event()
+        self.allow_finish = threading.Event()
+        self.finished = threading.Event()
+        self.closed = threading.Event()
+        self.close_count = 0
+        self.closed_while_running = False
+        self.observed_interrupt = None
+
+    def interrupt(self, message=None, **kwargs):
+        accepted = super().interrupt(message, **kwargs)
+        self.stop_received.set()
+        return accepted
+
+    def hard_interrupt(self, message=None, **kwargs):
+        super().hard_interrupt(message, **kwargs)
+        self.stop_received.set()
+
+    def run_conversation(self, **_kwargs):
+        # A stop can arrive before this thread exists. Use the real turn-start
+        # binding so the pending agent interrupt must reach the tool thread too.
+        _bind_interrupt_scope(self, lambda: SimpleNamespace(_set_interrupt=set_interrupt))
+        self.started.set()
+        try:
+            assert self.stop_received.wait(30), "child never received cancellation"
+            assert self._interrupt_requested
+            assert is_interrupted(), "stop did not reach the child execution thread"
+            self.observed_interrupt = (
+                self._interrupt_message, self._hard_interrupt_requested.is_set(),
+            )
+            self.unwinding.set()
+            assert self.allow_finish.wait(30), "test did not release child cleanup"
+            return {
+                "final_response": "", "completed": False, "interrupted": True,
+                "api_calls": 0, "messages": [],
+            }
+        finally:
+            self.clear_interrupt()
+            self.finished.set()
+
+    def get_activity_summary(self):
+        return {"api_call_count": 0}
+
+    def close(self):
+        self.closed_while_running |= not self.finished.is_set()
+        self.close_count += 1
+        self.closed.set()
+
+
+def _batch(parent, *children):
+    tasks = [{"goal": f"wait until cancelled {i}"} for i in range(len(children))]
+    parent._active_children.extend(children)
+    return _Batch(
+        task_list=tasks, children=[(i, tasks[i], child) for i, child in enumerate(children)], parent_agent=parent,
+        creds={"model": children[0].model}, context=None, top_role="leaf", max_children=len(children),
+        live_deleg_id=None, live_writers=[], live_paths=[], origin_wake_sid="",
+        origin_ui_session_id="", origin_owner_transport=None,
+        origin_owner_session_record=None, overall_start=time.monotonic(),
+    )
+
+
+@pytest.fixture
+def registry_state(tmp_path, monkeypatch):
+    monkeypatch.setenv("HERMES_HOME", str(tmp_path))
+    monkeypatch.delenv("HERMES_IGNORE_USER_CONFIG", raising=False)
+    (tmp_path / "config.yaml").write_text(
+        "delegation:\n  max_concurrent_children: 1\n  worktree_isolation: false\n",
+        encoding="utf-8",
+    )
+    async_delegation._reset_for_tests()
+    completion_queue = queue.Queue()
+    monkeypatch.setattr(process_registry, "completion_queue", completion_queue)
+    yield completion_queue
+    # Test bodies release their gates and join their workers before registry teardown.
+    if async_delegation._executor is not None:
+        async_delegation._executor.shutdown(wait=True)
+    async_delegation._reset_for_tests()
+
+
+@pytest.mark.parametrize("rejection", ["capacity", "schedule_failure", "partial_schedule_failure"])
+@pytest.mark.parametrize("stop_timing", ["running", "during_admission"])
+@pytest.mark.parametrize("stop_kind", ["soft", "hard"])
+def test_rejected_background_child_stops_with_parent(
+    registry_state, monkeypatch, tmp_path, rejection, stop_timing, stop_kind,
+):
+    parent, child = _Parent(), _ControlledChild()
+    background_child = pending_child = None
+    if rejection == "partial_schedule_failure":
+        # Three independent units: one accepted, one rejected, one not yet submitted.
+        # The model-facing batch width is legal under the configured limit.
+        (tmp_path / "config.yaml").write_text(
+            "delegation:\n  max_concurrent_children: 3\n  worktree_isolation: false\n",
+            encoding="utf-8",
+        )
+        background_child, pending_child = _ControlledChild(), _ControlledChild()
+        background_child.session_id += "-background"
+        pending_child.session_id += "-pending"
+        batch = _batch(parent, background_child, child, pending_child)
+    else:
+        batch = _batch(parent, child)
+    occupied = threading.Event()
+    release_occupier = threading.Event()
+    admission_started = threading.Event()
+    continue_admission = threading.Event()
+    outcome = Future()
+
+    def occupy_slot():
+        occupied.set()
+        assert release_occupier.wait(30)
+        return {"status": "completed", "summary": "slot released"}
+
+    if rejection == "capacity":
+        accepted = async_delegation.dispatch_async_delegation(
+            goal="occupy the only slot", context=None, toolsets=None, role="leaf",
+            model=child.model, session_key="other-session", runner=occupy_slot,
+            max_async_children=1,
+        )
+        assert accepted["status"] == "dispatched"
+        assert occupied.wait(5)
+    elif rejection == "schedule_failure":
+        class RejectingExecutor:
+            def submit(self, *_args, **_kwargs):
+                raise RuntimeError("executor shut down")
+
+        monkeypatch.setattr(async_delegation, "_get_executor", lambda _n: RejectingExecutor())
+    else:
+        executor = async_delegation._get_executor(3)
+
+        class PartiallyRejectingExecutor:
+            submitted = 0
+
+            def submit(self, *args, **kwargs):
+                self.submitted += 1
+                if self.submitted == 2:
+                    raise RuntimeError("unit submission failed")
+                return executor.submit(*args, **kwargs)
+
+        partial_executor = PartiallyRejectingExecutor()
+        monkeypatch.setattr(async_delegation, "_get_executor", lambda _n: partial_executor)
+
+    dispatch = async_delegation.dispatch_async_delegation_batch
+    admissions = 0
+    accepted_ids = []
+
+    def pause_admission(**kwargs):
+        nonlocal admissions
+        admissions += 1
+        rejected_admission = 2 if background_child is not None else 1
+        if admissions == rejected_admission:
+            admission_started.set()
+            assert continue_admission.wait(5)
+        result = dispatch(**kwargs)
+        if result.get("status") == "dispatched":
+            accepted_ids.append(result["delegation_id"])
+        return result
+
+    monkeypatch.setattr(async_delegation, "dispatch_async_delegation_batch", pause_admission)
+
+    def run_dispatch():
+        try:
+            outcome.set_result(json.loads(_dispatch_background(batch)))
+        except BaseException as exc:
+            outcome.set_exception(exc)
+
+    worker = threading.Thread(target=run_dispatch, daemon=True)
+    worker.start()
+    try:
+        assert admission_started.wait(5)
+        if background_child is not None:
+            assert background_child.started.wait(5)
+        request_stop = parent.hard_interrupt if stop_kind == "hard" else parent.interrupt
+        stop_message = "user correction or stop request"
+        if stop_timing == "during_admission":
+            request_stop(stop_message)
+        continue_admission.set()
+        assert child.started.wait(5)
+        if stop_timing == "running":
+            request_stop(stop_message)
+
+        assert child.stop_received.wait(5), "fallback lost parent cancellation ownership"
+        assert child.unwinding.wait(5)
+        assert child.observed_interrupt == (stop_message, stop_kind == "hard")
+        if background_child is not None:
+            assert not background_child.stop_received.is_set()
+            assert pending_child.stop_received.is_set(), "unsubmitted unit lost parent cancellation ownership"
+            assert not pending_child.started.is_set()
+        assert not outcome.done(), "dispatch returned while its child still owned resources"
+        assert child.close_count == 0
+        child.allow_finish.set()
+        result = outcome.result(timeout=5)
+        if background_child is None:
+            assert "SYNCHRONOUSLY" in result["note"]
+            assert result["results"][0]["status"] == "interrupted"
+        else:
+            assert result["status"] == "dispatched"
+            assert result["inline_results"][0]["status"] == "interrupted"
+            assert not background_child.stop_received.is_set()
+            assert pending_child.unwinding.wait(5)
+            assert pending_child.observed_interrupt == (stop_message, stop_kind == "hard")
+        assert child.finished.is_set()
+        assert child.close_count == 1
+        assert not child.closed_while_running
+        assert parent._active_children == []
+    finally:
+        continue_admission.set()
+        if not child.finished.is_set():
+            child.hard_interrupt("test teardown")
+        child.allow_finish.set()
+        worker.join(timeout=5)
+        release_occupier.set()
+        if background_child is not None:
+            async_delegation.interrupt_for_session(parent_session_id=parent.session_id)
+            for extra in (background_child, pending_child):
+                extra.allow_finish.set()
+                assert extra.closed.wait(5)
+                assert extra.finished.is_set()
+                assert extra.close_count == 1
+                assert not extra.closed_while_running
+            completed_ids = {registry_state.get(timeout=5)["delegation_id"] for _ in accepted_ids}
+            assert completed_ids == set(accepted_ids)
+        if rejection == "capacity":
+            completion = registry_state.get(timeout=5)
+            assert completion["delegation_id"] == accepted["delegation_id"]
+        assert not worker.is_alive()
+
+
+def test_accepted_background_child_keeps_registry_cancellation_ownership(registry_state):
+    parent, child = _Parent(), _ControlledChild()
+    try:
+        result = json.loads(_dispatch_background(_batch(parent, child)))
+        assert result["status"] == "dispatched"
+        assert child.started.wait(5)
+        parent.interrupt()
+        # Parent interrupt fan-out is synchronous; observing it return establishes
+        # that a detached child did not receive it without a timing-based wait.
+        assert parent._interrupt_requested
+        assert not child.stop_received.is_set()
+        assert not child.finished.is_set()
+        parent.hard_interrupt("stop the current parent turn")
+        assert parent._hard_interrupt_requested.is_set()
+        assert not child.stop_received.is_set()
+        assert async_delegation.interrupt_for_session(parent_session_id=parent.session_id) == 1
+        assert child.unwinding.wait(5)
+        assert child.observed_interrupt[1] is True
+        assert child.close_count == 0
+        child.allow_finish.set()
+        completion = registry_state.get(timeout=5)
+        assert completion["delegation_id"] == result["delegation_id"]
+        assert completion["results"][0]["status"] == "interrupted"
+        assert child.finished.is_set()
+        assert child.close_count == 1
+        assert not child.closed_while_running
+        assert parent._active_children == []
+    finally:
+        if not child.finished.is_set():
+            child.hard_interrupt("test teardown")
+        child.allow_finish.set()
+        assert child.closed.wait(5)
diff --git a/tools/delegate_tool_dispatch.py b/tools/delegate_tool_dispatch.py
index da75fd9d8a..7f768416b8 100644
--- a/tools/delegate_tool_dispatch.py
+++ b/tools/delegate_tool_dispatch.py
@@ -14,7 +14,7 @@ from dataclasses import dataclass, replace
 from typing import Any, Dict, List, Optional
 
 from tools.async_delegation import _new_delegation_id, record_unit_child
-from tools.delegate_tool_child_run import _detach_child, _fabricated_entry, _signal_child_stop
+from tools.delegate_tool_child_run import _attach_child, _detach_child, _fabricated_entry, _signal_child_stop
 from tools.delegate_tool_progress import (
     SUBAGENT_FAILURE_STATUSES, _clean_error_text, _print_completion_line, _quiet, format_batch_tag,
 )
@@ -374,6 +374,21 @@ def _dispatch_unit(unit: _Batch, unit_id: Optional[str], slot_key: Optional[str]
         progress_fn=lambda: _batch_progress_token(child_agents), **routing,
     )
 
+def _restore_parent_cancellation(unit: _Batch) -> None:
+    # Rejected children remain owned by the parent. Attach before replaying a
+    # cancellation that may have arrived while async admission had them detached.
+    parent = unit.parent_agent
+    for _, _, child in unit.children:
+        _attach_child(parent, child)
+    if getattr(parent, "_interrupt_requested", False) is True:
+        hard_stop = getattr(parent, "_hard_interrupt_requested", None)
+        for _, _, child in unit.children:
+            if hard_stop is not None and hard_stop.is_set():
+                _signal_child_stop(child, getattr(parent, "_interrupt_message", None))
+            else:
+                with _quiet("Failed to propagate interrupt to fallback child: %s"):
+                    child.interrupt(getattr(parent, "_interrupt_message", None))
+
 def _dispatch_background(batch: _Batch) -> str:
     """Dispatch the call as independent async units (see ``_units_of``) and return the tool result JSON. Every unit
     of one call shares ONE pool slot (``slot_key``), so grouping never changes capacity accounting. Falls back to
@@ -387,10 +402,6 @@ def _dispatch_background(batch: _Batch) -> str:
 
     parent_agent = batch.parent_agent
     session_key, origin_ui_session_id = _resolve_async_session_key(parent_agent, batch.origin_ui_session_id)
-    # The children's lifecycle is owned by the async registry now: drop them from the parent's
-    # interrupt-propagation list (_build_child_agent attached them, which is correct for sync runs).
-    for (_, _, c) in batch.children:
-        _detach_child(parent_agent, c)
     routing = dict(
         session_key=session_key, origin_ui_session_id=origin_ui_session_id, origin_session_id=wake_sid,
         parent_session_id=getattr(parent_agent, "session_id", None), max_async_children=_get_max_async_children(),
@@ -405,11 +416,16 @@ def _dispatch_background(batch: _Batch) -> str:
         # cache/delegation/live/<id>/; several units suffix it (-1, -2, ...) and the call keeps the bare id.
         unit_id = batch.live_deleg_id if len(units) == 1 else (f"{batch.live_deleg_id}-{k + 1}" if batch.live_deleg_id else None)
         unit.unit_id = unit_id = unit_id or _new_delegation_id()  # fixed before the runner can start
+        # The worker can start before admission returns. Detach only this unit:
+        # unsubmitted units must still receive parent stops while a fallback runs.
+        for _, _, child in unit.children:
+            _detach_child(parent_agent, child)
         dispatch = _dispatch_unit(unit, unit_id, slot_key, routing)
         if dispatch.get("status") == "dispatched":
             slot_key = slot_key or dispatch["delegation_id"]
             dispatched.append((unit, dispatch["delegation_id"]))
             continue
+        _restore_parent_cancellation(unit)
         if not dispatched:
             logger.info(
                 "delegate_task: async pool at capacity (%s); running the whole batch synchronously instead.",
@@ -419,7 +435,7 @@ def _dispatch_background(batch: _Batch) -> str:
         # Later units of an admitted call share its slot and cannot be capacity-rejected; a scheduler failure runs
         # the unit inline so no task is silently dropped.
         logger.warning("delegate_task: unit %d/%d not accepted (%s); running it inline.", k + 1, len(units), dispatch.get("error"))
-        inline_results.extend(_execute_and_aggregate(unit, honor_parent_interrupt=False)["results"])
+        inline_results.extend(_execute_and_aggregate(unit)["results"])
     payload = _dispatched_payload(batch, dispatched)
     if inline_results:
         payload["inline_results"] = inline_results