diff --git a/products/tasks/backend/facade/api.py b/products/tasks/backend/facade/api.py
index 6c436d9e495b..21e15c649f50 100644
--- a/products/tasks/backend/facade/api.py
+++ b/products/tasks/backend/facade/api.py
@@ -1784,10 +1784,17 @@ def task_accessible_for_run_view(
     read actions, which the caller signals via ``bypass_visibility``. Run-mutating actions pass
     ``for_control`` to use the narrower ``task_control_q`` — public-channel visibility lets
     teammates watch a run, not drive it.
+
+    Slack-originated tasks are the exception: those threads are multiplayer, so any same-team
+    user can already steer the run from Slack (follow-ups record them as the run's actor, with
+    sandbox credentials minted for them). The runs API mirrors that and lets team members drive
+    and watch Slack tasks' runs — otherwise a non-creator actor's sandbox 404s on every callback
+    (reply relay, log-append heartbeat, completion PATCH) and the thread dies silently.
     """
     task_filter = Task.objects.filter(id=task_id, team_id=team_id)
     if not bypass_visibility:
-        task_filter = task_filter.filter(task_control_q(user_id) if for_control else task_visibility_q(user_id))
+        scope_q = task_control_q(user_id) if for_control else task_visibility_q(user_id)
+        task_filter = task_filter.filter(scope_q | Q(origin_product=Task.OriginProduct.SLACK))
     return task_filter.exists()
 
 
diff --git a/products/tasks/backend/tests/test_api.py b/products/tasks/backend/tests/test_api.py
index 90b7ae51e211..a6a27288f06f 100644
--- a/products/tasks/backend/tests/test_api.py
+++ b/products/tasks/backend/tests/test_api.py
@@ -9944,3 +9944,66 @@ def test_build_falls_back_to_stored_spec_when_builder_sandbox_gone(self, mock_wo
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(response.json()["status"], "scanning")
         mock_workflow.assert_called_once()
+
+
+class TestTaskRunSlackTaskTeamControl(BaseTaskAPITest):
+    """Slack-originated tasks are multiplayer: any same-team user may drive their runs.
+
+    Guards the incident where a non-creator's thread follow-up resumed a run whose sandbox
+    then 404'd on every callback (status PATCH, log append, Slack relay), so the workflow
+    starved of heartbeats and the thread died silently.
+    """
+
+    def _create_run(self, *, origin_product: Task.OriginProduct) -> tuple[Task, TaskRun]:
+        creator = self.create_organization_user("thread-starter")
+        task = Task.objects.create(
+            team=self.team,
+            created_by=creator,
+            title="Thread task",
+            description="Test Description",
+            origin_product=origin_product,
+        )
+        run = TaskRun.objects.create(
+            task=task,
+            team=self.team,
+            status=TaskRun.Status.IN_PROGRESS,
+            environment=TaskRun.Environment.CLOUD,
+        )
+        return task, run
+
+    @parameterized.expand(
+        [
+            ("teammate_can_patch_slack_run", Task.OriginProduct.SLACK, "patch", status.HTTP_200_OK),
+            ("teammate_can_retrieve_slack_run", Task.OriginProduct.SLACK, "get", status.HTTP_200_OK),
+            (
+                "teammate_cannot_patch_user_created_run",
+                Task.OriginProduct.USER_CREATED,
+                "patch",
+                status.HTTP_404_NOT_FOUND,
+            ),
+            (
+                "teammate_cannot_retrieve_user_created_run",
+                Task.OriginProduct.USER_CREATED,
+                "get",
+                status.HTTP_404_NOT_FOUND,
+            ),
+        ]
+    )
+    @patch("products.tasks.backend.models.TaskRun.publish_stream_state_event")
+    def test_non_creator_run_access_by_origin(
+        self,
+        _case_name: str,
+        origin_product: Task.OriginProduct,
+        method: str,
+        expected_status: int,
+        _mock_publish_stream_state_event: MagicMock,
+    ) -> None:
+        task, run = self._create_run(origin_product=origin_product)
+
+        url = f"/api/projects/@current/tasks/{task.id}/runs/{run.id}/"
+        if method == "patch":
+            response = self.client.patch(url, {"output": {"marker": "from-teammate"}}, format="json")
+        else:
+            response = self.client.get(url)
+
+        self.assertEqual(response.status_code, expected_status)