Add safety checks for missing QKV keys

If a hook fails silently, the layer's qkv_captures dict might exist but
be missing the 'q', 'k', or 'v' keys. This would cause a KeyError.
Now we check for each key's existence before accessing it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/model_service.py

@@ -1859,11 +1859,16 @@ async def analyze_research_attention(request: Dict[str, Any], authenticated: boo
                         k_matrix = None
                         v_matrix = None
                         if layer_idx in qkv_captures:
+                            layer_qkv = qkv_captures[layer_idx]
                             # Q/K/V shape: [seq_len, n_heads, head_dim]
                             # Convert to float32 for numpy (bfloat16 not supported)
-                            q_matrix = qkv_captures[layer_idx]['q'][:, head_idx, :].float().numpy().tolist()
-                            k_matrix = qkv_captures[layer_idx]['k'][:, head_idx, :].float().numpy().tolist()
-                            v_matrix = qkv_captures[layer_idx]['v'][:, head_idx, :].float().numpy().tolist()
+                            # Check each key exists (hooks may have failed for some)
+                            if 'q' in layer_qkv:
+                                q_matrix = layer_qkv['q'][:, head_idx, :].float().numpy().tolist()
+                            if 'k' in layer_qkv:
+                                k_matrix = layer_qkv['k'][:, head_idx, :].float().numpy().tolist()
+                            if 'v' in layer_qkv:
+                                v_matrix = layer_qkv['v'][:, head_idx, :].float().numpy().tolist()
 
                         critical_heads.append({
                             "head_idx": head_idx,
@@ -2414,9 +2419,14 @@ async def analyze_research_attention_stream(request: Dict[str, Any], authenticat
                             k_matrix = None
                             v_matrix = None
                             if layer_idx in qkv_captures:
-                                q_matrix = qkv_captures[layer_idx]['q'][:, head_idx, :].float().numpy().tolist()
-                                k_matrix = qkv_captures[layer_idx]['k'][:, head_idx, :].float().numpy().tolist()
-                                v_matrix = qkv_captures[layer_idx]['v'][:, head_idx, :].float().numpy().tolist()
+                                layer_qkv = qkv_captures[layer_idx]
+                                # Check each key exists (hooks may have failed for some)
+                                if 'q' in layer_qkv:
+                                    q_matrix = layer_qkv['q'][:, head_idx, :].float().numpy().tolist()
+                                if 'k' in layer_qkv:
+                                    k_matrix = layer_qkv['k'][:, head_idx, :].float().numpy().tolist()
+                                if 'v' in layer_qkv:
+                                    v_matrix = layer_qkv['v'][:, head_idx, :].float().numpy().tolist()
 
                             critical_heads.append({
                                 "head_idx": head_idx,