Fix: strip non-ASCII chars before sending to llama-server

agent.py

@@ -66,6 +66,11 @@ class AgentState(TypedDict):
 
 # ── Helpers ────────────────────────────────────────────────────────────────────
 
+def _sanitize(text: str) -> str:
+    import re
+    return re.sub(r'[^\x00-\x7F]', '-', text)
+
+
 def _call_model(prompt: str, max_tokens: int = 600, json_mode: bool = False) -> str:
     """Call Modal llama.cpp endpoint (or local fallback)."""
     if MODAL_ENDPOINT:
@@ -213,7 +218,7 @@ def node_build_context(state: AgentState) -> AgentState:
             break
         parts.append(snippet)
         total += len(snippet)
-    state["context"] = "\n\n---\n\n".join(parts)
+    state["context"] = _sanitize("\n\n---\n\n".join(parts))
     return state