fix(explorer): fix profile thread selection

src/sentry/seer/explorer/tools.py

@@ -582,6 +582,11 @@ def rpc_get_profile_flamegraph(profile_id: str, organization_id: int) -> dict[st
         )
         return {"error": "Failed to generate execution tree from profile data"}
 
+    # Extract thread_id from profile data
+    profile = profile_data.get("profile") or profile_data.get("chunk", {}).get("profile")
+    samples = profile.get("samples", []) if profile else []
+    thread_id = str(samples[0]["thread_id"]) if samples else None
+
     return {
         "execution_tree": execution_tree,
         "metadata": {
@@ -590,6 +595,7 @@ def rpc_get_profile_flamegraph(profile_id: str, organization_id: int) -> dict[st
             "is_continuous": is_continuous,
             "start_ts": min_start_ts,
             "end_ts": max_end_ts,
+            "thread_id": thread_id,
         },
     }
 

src/sentry/seer/explorer/utils.py

@@ -68,15 +68,12 @@ def _convert_profile_to_execution_tree(profile_data: dict) -> list[dict]:
     if not all([frames, stacks, samples]):
         return []
 
-    # Find the MainThread ID
-    thread_metadata = profile.get("thread_metadata", {}) or {}
-    main_thread_id = next(
-        (key for key, value in thread_metadata.items() if value.get("name") == "MainThread"), None
-    )
-    if (
-        not main_thread_id and len(thread_metadata) == 1
-    ):  # if there is only one thread, use that as the main thread
-        main_thread_id = list(thread_metadata.keys())[0]
+    # Use the thread ID from the first sample as this should be the one with the most application logic
+    if samples:
+        main_thread_id = str(samples[0]["thread_id"])
+    else:
+        # No samples - can't determine thread
+        main_thread_id = None
 
     def _get_elapsed_since_start_ns(
         sample: dict[str, Any], all_samples: list[dict[str, Any]]

tests/sentry/seer/autofix/test_autofix.py

@@ -81,7 +81,7 @@ def test_convert_profile_to_execution_tree(self) -> None:
         assert len(child["children"]) == 0  # No children for the last in_app frame
 
     def test_convert_profile_to_execution_tree_non_main_thread(self) -> None:
-        """Test that non-MainThread samples are excluded from execution tree"""
+        """Test that the first sample's thread is used (even if not MainThread)"""
         profile_data = {
             "profile": {
                 "frames": [
@@ -101,8 +101,10 @@ def test_convert_profile_to_execution_tree_non_main_thread(self) -> None:
 
         execution_tree = _convert_profile_to_execution_tree(profile_data)
 
-        # Should be empty since no MainThread samples
-        assert len(execution_tree) == 0
+        # Should include the worker thread since it's the first sample's thread
+        assert len(execution_tree) == 1
+        assert execution_tree[0]["function"] == "worker"
+        assert execution_tree[0]["filename"] == "worker.py"
 
     def test_convert_profile_to_execution_tree_merges_duplicate_frames(self) -> None:
         """Test that duplicate frames in different samples are merged correctly"""