diff --git a/explorer.py b/explorer.py
index 056a1ae..d770950 100644
--- a/explorer.py
+++ b/explorer.py
@@ -19,6 +19,7 @@ import logging
 import os
 import re
 import traceback
+from datetime import datetime
 from typing import Dict, List, Optional, Tuple
 
 try:
@@ -2096,6 +2097,36 @@ def choose_trajectory_title(axis_def: dict, axis: str, threshold: float = 0.65)
     except Exception:
         pass
     debug_enabled = get_debug_trajectories_enabled()
+    # Add detailed diagnostics to understand why trace_count is 0
+    if trace_count == 0:
+        _last_trajectories_diagnostics.update(
+            {
+                "stage": "zero_traces",
+                "positions_count": sum(len(pos) for pos in positions_by_window.values())
+                if positions_by_window
+                else 0,
+                "party_map_count": len(party_map) if party_map else 0,
+                "centroids_count": len(centroids) if centroids else 0,
+                "selected_parties_count": len(selected_parties)
+                if selected_parties
+                else 0,
+                "timestamp": datetime.now().isoformat(),
+            }
+        )
+        # Check if there are positions but no centroids (name mismatch)
+        if positions_by_window and party_map and not centroids:
+            # Sample some MP names from positions
+            sample_mps = []
+            for window, positions in list(positions_by_window.items())[:1]:
+                sample_mps = list(positions.keys())[:5]
+                break
+            # Check if these MPs are in party_map
+            matched = sum(1 for mp in sample_mps if mp in party_map)
+            _last_trajectories_diagnostics["name_match_check"] = {
+                "sample_mps": sample_mps,
+                "matched_in_party_map": matched,
+                "sample_size": len(sample_mps),
+            }
     if trace_count == 0:
         try:
             st.info(