diff --git a/agent/relay_llm.py b/agent/relay_llm.py
index 8f560c1854..58a5c1bd5e 100644
--- a/agent/relay_llm.py
+++ b/agent/relay_llm.py
@@ -55,6 +55,13 @@ def execute(
 
     def invoke(next_request: Any) -> Any:
         nonlocal callback_error
+
+        def guarded(final: dict[str, Any]) -> Any:
+            # Nested relay calls inside a managed provider callback must run
+            # unmanaged (#77244) — see relay_runtime.managed_callback_guard.
+            with relay_runtime.managed_callback_guard():
+                return callback(final)
+
         try:
             final_request = _provider_request(
                 request,
@@ -63,7 +70,7 @@ def execute(
                 codec_baseline_body=codec_baseline_body,
                 metadata=metadata,
             )
-            raw = callback_context.copy().run(callback, final_request)
+            raw = callback_context.copy().run(guarded, final_request)
         except BaseException as exc:
             callback_error = exc
             raise
@@ -149,7 +156,10 @@ async def execute_async(
                 metadata=metadata,
             )
             async def call_provider() -> Any:
-                return await callback(final_request)
+                # Nested relay calls inside a managed provider callback must
+                # run unmanaged (#77244).
+                with relay_runtime.managed_callback_guard():
+                    return await callback(final_request)
 
             task = callback_context.copy().run(
                 asyncio.create_task,
@@ -396,7 +406,14 @@ class ManagedLlmStream(Iterator[Any]):
         def run_callback(callback: Callable[..., Any], *args: Any) -> Any:
             # Relay can invoke stream surfaces while another callback still
             # owns the captured Context. A fresh copy is safe to enter.
-            return callback_context.copy().run(callback, *args)
+            def guarded() -> Any:
+                # Hermes-side callbacks run while the native pipeline drives
+                # this stream; nested relay calls they make must bypass
+                # managed execution (#77244).
+                with relay_runtime.managed_callback_guard():
+                    return callback(*args)
+
+            return callback_context.copy().run(guarded)
 
         runtime, session, parent = relay_runtime.resolve_execution_context(session_id)
         if (
diff --git a/agent/relay_runtime.py b/agent/relay_runtime.py
index a0a7315796..095fbb8315 100644
--- a/agent/relay_runtime.py
+++ b/agent/relay_runtime.py
@@ -492,6 +492,34 @@ _CURRENT_TURN: contextvars.ContextVar[RelayTurnContext | None] = contextvars.Con
     "hermes_relay_turn", default=None
 )
 
+# Depth of managed Relay callbacks executing on the current logical call path.
+# Set >0 while the native Relay pipeline is mid-dispatch of a Hermes callback
+# (tool or LLM). Nested managed execution inside that window is structurally
+# broken — the native pipeline binds its Futures to the outer, blocked event
+# loop — so resolve_execution_context() bypasses Relay while the flag is set.
+# ContextVar so the marker follows contextvars.copy_context() into the worker
+# threads / per-thread loops that tools use for their internal async work.
+_MANAGED_CALLBACK_DEPTH: contextvars.ContextVar[int] = contextvars.ContextVar(
+    "hermes_relay_managed_callback_depth", default=0
+)
+
+
+class managed_callback_guard:
+    """Mark the current context as inside a managed Relay callback.
+
+    Synchronous context manager used by the relay adapters around the
+    ``invoke()`` callbacks they hand to the native pipeline. Everything the
+    callback transitively calls (including work it forwards to worker threads
+    via ``contextvars.copy_context()``) sees the marker and runs unmanaged.
+    """
+
+    def __enter__(self) -> "managed_callback_guard":
+        self._token = _MANAGED_CALLBACK_DEPTH.set(_MANAGED_CALLBACK_DEPTH.get() + 1)
+        return self
+
+    def __exit__(self, *exc_info: Any) -> None:
+        _MANAGED_CALLBACK_DEPTH.reset(self._token)
+
 
 class RelaySessionCoordinator:
     """Own semantic conversation and turn lifetimes for Hermes core."""
@@ -843,6 +871,20 @@ def resolve_execution_context(
     session_id: str,
 ) -> tuple[RelayRuntime | None, RelaySession | None, Any]:
     """Resolve one active turn/session parent for managed Relay execution."""
+    if _MANAGED_CALLBACK_DEPTH.get() > 0:
+        # A managed Relay callback is already executing on this logical call
+        # path (e.g. the native ``tools.execute`` pipeline is mid-dispatch of
+        # a Hermes tool). Nested managed execution here is structurally
+        # impossible: the native pipeline binds its Futures to the OUTER
+        # call's event loop, which is blocked inside the synchronous tool
+        # callback until the tool returns. A nested managed LLM call (the
+        # vision_analyze auxiliary path) therefore awaits a foreign-loop
+        # Future that can never complete — "attached to a different loop"
+        # at best, deadlock at worst, and "Event loop is closed" during
+        # shutdown when the orphaned Future is completed late (#77244).
+        # Run nested calls unmanaged; the outer tool scope still records
+        # the tool-level event for observability.
+        return None, None, None
     inherited_turn = current_turn()
     if inherited_turn is not None and (
         not inherited_turn.relay_enabled or inherited_turn.closed
diff --git a/agent/relay_tools.py b/agent/relay_tools.py
index f2177f1a3b..91c0926b7e 100644
--- a/agent/relay_tools.py
+++ b/agent/relay_tools.py
@@ -36,8 +36,17 @@ def execute(
     def invoke(next_args: Any) -> Any:
         nonlocal callback_error, observed_args
         observed_args = next_args if isinstance(next_args, dict) else args
+
+        def guarded(final_args: dict[str, Any]) -> Any:
+            # Everything the tool transitively calls (including auxiliary LLM
+            # calls it forwards to worker threads) must bypass managed Relay
+            # execution — the native pipeline's Futures bind to THIS loop,
+            # which is blocked until the tool returns (#77244).
+            with relay_runtime.managed_callback_guard():
+                return callback(final_args)
+
         try:
-            result = callback_context.copy().run(callback, observed_args)
+            result = callback_context.copy().run(guarded, observed_args)
         except BaseException as exc:
             callback_error = exc
             raise
diff --git a/tests/agent/test_relay_nested_execution.py b/tests/agent/test_relay_nested_execution.py
new file mode 100644
index 0000000000..45671922bd
--- /dev/null
+++ b/tests/agent/test_relay_nested_execution.py
@@ -0,0 +1,233 @@
+"""Regression tests for nested managed Relay execution (#77244).
+
+The native Relay pipeline binds its Futures to the event loop that entered
+``run_in_session_async``. While a managed tool callback is executing, that
+loop is blocked until the callback returns — so any NESTED managed relay call
+made from inside the callback (e.g. vision_analyze's auxiliary LLM call on a
+worker-thread loop) awaits a Future that can never complete:
+``RuntimeError: ... attached to a different loop``, or a deadlock, or
+``Event loop is closed`` at shutdown.
+
+The fix: ``relay_runtime.managed_callback_guard`` marks the callback's
+context (a ContextVar, so it propagates through ``contextvars.copy_context()``
+into tool worker threads); ``resolve_execution_context`` returns the
+no-relay triple while the marker is set, so nested calls run unmanaged.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import contextvars
+import threading
+
+import pytest
+
+pytest.importorskip("nemo_relay")
+
+from agent import relay_llm, relay_runtime, relay_tools
+
+
+@pytest.fixture()
+def relay_turn(tmp_path, monkeypatch):
+    monkeypatch.setenv("HERMES_HOME", str(tmp_path / "profile"))
+    relay_runtime._reset_for_tests()
+    lease = relay_runtime.SESSION_COORDINATOR.acquire_conversation(
+        profile_key=relay_runtime.current_profile_key(),
+        session_id="session-1",
+        platform="cli",
+    )
+    turn = relay_runtime.SESSION_COORDINATOR.begin_turn(
+        lease,
+        turn_id="turn-1",
+        task_id="task-1",
+    )
+    lease.host.retain_managed_execution("test.nested_relay")
+    try:
+        yield lease.host
+    finally:
+        lease.host.release_managed_execution("test.nested_relay")
+        relay_runtime.SESSION_COORDINATOR.end_turn(turn, outcome="success")
+        relay_runtime.SESSION_COORDINATOR.release_conversation(lease)
+        relay_runtime._reset_for_tests()
+
+
+def _nested_aux_llm_call_from_worker_thread() -> dict:
+    """Mimic vision_analyze: aux LLM call via a worker thread's own loop."""
+
+    async def aux_call():
+        async def provider(request):
+            await asyncio.sleep(0)
+            return {
+                "id": "aux-1",
+                "object": "chat.completion",
+                "choices": [
+                    {
+                        "index": 0,
+                        "message": {"role": "assistant", "content": "nested"},
+                        "finish_reason": "stop",
+                    }
+                ],
+            }
+
+        return await relay_llm.execute_current_async(
+            {"messages": [{"role": "user", "content": "look"}], "model": "m"},
+            provider,
+            name="nested-prov",
+            model_name="m",
+            metadata={
+                "api_mode": "chat_completions",
+                "api_request_id": "req-nested",
+                "call_role": "auxiliary:vision",
+            },
+        )
+
+    holder: dict = {}
+
+    def run() -> None:
+        loop = asyncio.new_event_loop()
+        try:
+            holder["result"] = loop.run_until_complete(aux_call())
+        except BaseException as exc:  # pragma: no cover - assertion payload
+            holder["error"] = exc
+        finally:
+            loop.close()
+
+    ctx = contextvars.copy_context()
+    thread = threading.Thread(target=lambda: ctx.run(run))
+    thread.start()
+    thread.join(timeout=30)
+    assert not thread.is_alive(), "nested aux call deadlocked (#77244)"
+    if "error" in holder:
+        raise holder["error"]
+    return holder["result"]
+
+
+def test_nested_aux_llm_call_inside_managed_tool_does_not_cross_loops(relay_turn):
+    """The #77244 shape: managed tool -> worker-thread aux LLM call."""
+    host = relay_turn
+    managed_llm_names: list[str] = []
+    original_execute = host.relay.llm.execute
+
+    def counting_execute(name, *args, **kwargs):
+        managed_llm_names.append(name)
+        return original_execute(name, *args, **kwargs)
+
+    host.relay.llm.execute = counting_execute
+    try:
+        def the_tool(args):
+            result = _nested_aux_llm_call_from_worker_thread()
+            return {"analysis": result["choices"][0]["message"]["content"]}
+
+        result, _final_args = relay_tools.execute(
+            "vision_analyze",
+            {"image_url": "/tmp/x.png"},
+            the_tool,
+            session_id="session-1",
+            metadata={"api_request_id": "req-tool"},
+        )
+    finally:
+        host.relay.llm.execute = original_execute
+
+    assert "nested" in str(result)
+    # The nested call must have bypassed the managed pipeline entirely.
+    assert "nested-prov" not in managed_llm_names
+
+
+def test_main_turn_llm_call_stays_managed(relay_turn):
+    """The guard must not disable relay for top-level (non-nested) calls."""
+    host = relay_turn
+    managed_llm_names: list[str] = []
+    original_execute = host.relay.llm.execute
+
+    def counting_execute(name, *args, **kwargs):
+        managed_llm_names.append(name)
+        return original_execute(name, *args, **kwargs)
+
+    host.relay.llm.execute = counting_execute
+    try:
+        out = relay_llm.execute(
+            {"messages": [{"role": "user", "content": "hi"}], "model": "m"},
+            lambda request: {
+                "id": "main-1",
+                "object": "chat.completion",
+                "choices": [
+                    {
+                        "index": 0,
+                        "message": {"role": "assistant", "content": "main"},
+                        "finish_reason": "stop",
+                    }
+                ],
+            },
+            session_id="session-1",
+            name="main-prov",
+            model_name="m",
+            metadata={
+                "api_mode": "chat_completions",
+                "api_request_id": "req-main",
+                "call_role": "primary",
+            },
+        )
+    finally:
+        host.relay.llm.execute = original_execute
+
+    assert out is not None
+    assert "main-prov" in managed_llm_names
+
+
+def test_guard_resets_after_managed_callback_returns(relay_turn):
+    """After the tool returns, subsequent calls are managed again."""
+    host = relay_turn
+    managed_llm_names: list[str] = []
+    original_execute = host.relay.llm.execute
+
+    def counting_execute(name, *args, **kwargs):
+        managed_llm_names.append(name)
+        return original_execute(name, *args, **kwargs)
+
+    host.relay.llm.execute = counting_execute
+    try:
+        relay_tools.execute(
+            "noop_tool",
+            {},
+            lambda args: {"ok": True},
+            session_id="session-1",
+            metadata={"api_request_id": "req-tool2"},
+        )
+        assert relay_runtime._MANAGED_CALLBACK_DEPTH.get() == 0
+        relay_llm.execute(
+            {"messages": [{"role": "user", "content": "hi"}], "model": "m"},
+            lambda request: {
+                "id": "after-1",
+                "object": "chat.completion",
+                "choices": [
+                    {
+                        "index": 0,
+                        "message": {"role": "assistant", "content": "after"},
+                        "finish_reason": "stop",
+                    }
+                ],
+            },
+            session_id="session-1",
+            name="after-prov",
+            model_name="m",
+            metadata={
+                "api_mode": "chat_completions",
+                "api_request_id": "req-after",
+                "call_role": "primary",
+            },
+        )
+    finally:
+        host.relay.llm.execute = original_execute
+
+    assert "after-prov" in managed_llm_names
+
+
+def test_resolve_execution_context_bypasses_inside_guard(relay_turn):
+    with relay_runtime.managed_callback_guard():
+        runtime, session, parent = relay_runtime.resolve_execution_context(
+            "session-1"
+        )
+    assert runtime is None and session is None and parent is None
+    # Outside the guard the context resolves normally again.
+    runtime, session, _parent = relay_runtime.resolve_execution_context("session-1")
+    assert runtime is not None and session is not None