diff --git a/agent/relay_runtime.py b/agent/relay_runtime.py
index 5434cbe4a5..8981001c1b 100644
--- a/agent/relay_runtime.py
+++ b/agent/relay_runtime.py
@@ -445,8 +445,8 @@ class RelayRuntime:
         with session.lock:
             if session.closing:
                 return None
-            if isinstance(cwd, str) and cwd.strip():
-                session.cwd = cwd.strip()
+            if cwd is not None:
+                session.cwd = _scope_input(cwd).get("cwd", "")
             if session.handle is None:
                 self._open_session_scope(
                     session, {**(metadata or {}), **runtime_metadata(self.runtime_id)},
@@ -950,12 +950,15 @@ class RelaySessionCoordinator:
                 "parent_session_id": parent_session_id, "model": model, "cwd": session_cwd,
             }
             session = _warn_on_error("conversation initialization", self._open_conversation_session, host, context)
-        effective_turn_cwd = (
-            _scope_input(turn_cwd).get("cwd") or _scope_input(session_cwd).get("cwd") or ""
-        )
-        if not effective_turn_cwd and session is not None:
+        if turn_cwd is not None:
+            effective_turn_cwd = _scope_input(turn_cwd).get("cwd", "")
+        elif session_cwd is not None:
+            effective_turn_cwd = _scope_input(session_cwd).get("cwd", "")
+        elif session is not None:
             with session.lock:
                 effective_turn_cwd = session.cwd
+        else:
+            effective_turn_cwd = ""
         return ConversationLease(
             profile_key=profile_key, session_id=session_id, platform=platform, host=host,
             session=session, parent_session_id=parent_session_id, turn_cwd=effective_turn_cwd,
diff --git a/agent/turn_facade.py b/agent/turn_facade.py
index 67a2834d4f..3c901a41cb 100644
--- a/agent/turn_facade.py
+++ b/agent/turn_facade.py
@@ -96,7 +96,10 @@ class TurnFacadeMixin:
             conversation_history = admission.conversation_history
 
             relay_session_cwd, relay_turn_cwd = resolve_relay_scope_cwds(
-                self, effective_task_id, session_id, task_context["platform"]
+                self,
+                effective_task_id,
+                task_context["session_id"],
+                task_context["platform"],
             )
             relay_lease = relay_runtime.SESSION_COORDINATOR.acquire_conversation(
                 profile_key=relay_runtime.current_profile_key(),
diff --git a/tests/agent/test_relay_session_segments.py b/tests/agent/test_relay_session_segments.py
index 9287d6141a..72feeb06f2 100644
--- a/tests/agent/test_relay_session_segments.py
+++ b/tests/agent/test_relay_session_segments.py
@@ -297,6 +297,26 @@ class TestCwdProjection:
         assert fake.scope.pushes[-1]["input"] == {"cwd": "/workspace/next-task"}
         coordinator.end_turn(turn, outcome="success")
 
+    def test_explicit_unknown_cwd_clears_prior_scope_input(self, coordinator):
+        fake = _FakeRelay()
+        runtime = _make_runtime(fake)
+        lease = _acquire(
+            coordinator, runtime,
+            session_cwd="/workspace/session", turn_cwd="/workspace/task",
+        )
+        coordinator.end_turn(
+            coordinator.begin_turn(lease, turn_id="t1", task_id="task1"),
+            outcome="success",
+        )
+
+        lease = _acquire(coordinator, runtime, session_cwd="", turn_cwd="")
+        runtime.rotate_session_scope(lease.session, reason="compaction")
+        turn = coordinator.begin_turn(lease, turn_id="t2", task_id="task2")
+
+        assert _session_pushes(fake)[-1]["input"] == {}
+        assert fake.scope.pushes[-1]["input"] == {}
+        coordinator.end_turn(turn, outcome="success")
+
 
 class TestCompactionRotation:
     def test_compaction_rotates_at_next_begin_turn_not_immediately(