diff --git a/agent/dashboard/thread_api.py b/agent/dashboard/thread_api.py
index 0cebc979..6e5cdfbb 100644
--- a/agent/dashboard/thread_api.py
+++ b/agent/dashboard/thread_api.py
@@ -428,7 +428,7 @@ async def get_dashboard_thread(
         raise HTTPException(404, "thread not found") from exc
 
     metadata = thread.get("metadata") if isinstance(thread.get("metadata"), dict) else {}
-    _assert_thread_owner(metadata, login, email)
+    is_owner = _user_owns_thread(metadata, login, email)
 
     messages: list[dict[str, Any]] = []
     try:
@@ -454,7 +454,7 @@ async def get_dashboard_thread(
             else None
         ),
     )
-    if mark_viewed and status != "running":
+    if mark_viewed and is_owner and status != "running":
         metadata = await _mark_thread_viewed(
             client,
             thread_id,
diff --git a/tests/test_dashboard_thread_api_activity.py b/tests/test_dashboard_thread_api_activity.py
index 7393d397..60b18d66 100644
--- a/tests/test_dashboard_thread_api_activity.py
+++ b/tests/test_dashboard_thread_api_activity.py
@@ -83,6 +83,24 @@ async def test_get_dashboard_thread_marks_finished_thread_viewed(monkeypatch) ->
     assert client.threads.thread["metadata"]["last_viewed_run_id"] == "run-1"
 
 
+async def test_get_dashboard_thread_readable_by_non_owner(monkeypatch) -> None:
+    client = FakeClient(
+        {
+            "source": "slack",
+            "github_login": "octocat",
+            "latest_run_id": "run-1",
+            "latest_run_status": "success",
+        },
+        "success",
+    )
+    monkeypatch.setattr(thread_api, "langgraph_client", lambda: client)
+
+    result = await thread_api.get_dashboard_thread("tid", "someone-else")
+
+    assert result["status"] == "finished"
+    assert "last_viewed_run_id" not in client.threads.thread["metadata"]
+
+
 async def test_get_dashboard_thread_skips_mark_viewed_when_disabled(monkeypatch) -> None:
     client = FakeClient(
         {