diff --git a/run_agent.py b/run_agent.py
index b53d1c823..71f9e8d16 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -9662,7 +9662,81 @@ class AIAgent:
                                 ),
                             }}
                         except Exception:
-                            pass
+                            # GLM-5.1 and similar models can generate
+                            # malformed tool_call arguments (truncated JSON,
+                            # trailing commas, Python None, etc.).  The API
+                            # proxy rejects these with HTTP 400 "invalid tool
+                            # call arguments".  Attempt common repairs; if
+                            # all fail, replace with "{}" so the request
+                            # succeeds (better than crashing the session).
+                            raw_args = tc["function"]["arguments"]
+                            repaired = False
+                            raw_stripped = raw_args.strip() if isinstance(raw_args, str) else ""
+
+                            # Fast-path: empty / whitespace-only → empty object
+                            if not raw_stripped:
+                                tc["function"]["arguments"] = "{}"
+                                repaired = True
+                                logger.warning(
+                                    "Sanitized empty tool_call arguments for %s",
+                                    tc["function"].get("name", "?"),
+                                )
+                            # Python-literal None → JSON null → normalise to {}
+                            elif raw_stripped == "None":
+                                tc["function"]["arguments"] = "{}"
+                                repaired = True
+                                logger.warning(
+                                    "Sanitized Python-None tool_call arguments for %s",
+                                    tc["function"].get("name", "?"),
+                                )
+
+                            if not repaired:
+                                # Attempt common JSON repairs
+                                import re as _re
+                                fixed = raw_stripped
+                                # 1. Strip trailing commas before } or ]
+                                fixed = _re.sub(r',\s*([}\]])', r'\1', fixed)
+                                # 2. Close unclosed structures
+                                open_curly = fixed.count('{') - fixed.count('}')
+                                open_bracket = fixed.count('[') - fixed.count(']')
+                                if open_curly > 0:
+                                    fixed += '}' * open_curly
+                                if open_bracket > 0:
+                                    fixed += ']' * open_bracket
+                                # 3. Remove extra closing braces/brackets
+                                while True:
+                                    try:
+                                        json.loads(fixed)
+                                        break
+                                    except json.JSONDecodeError:
+                                        if fixed.endswith('}') and fixed.count('}') > fixed.count('{'):
+                                            fixed = fixed[:-1]
+                                        elif fixed.endswith(']') and fixed.count(']') > fixed.count('['):
+                                            fixed = fixed[:-1]
+                                        else:
+                                            break
+                                try:
+                                    json.loads(fixed)
+                                    tc["function"]["arguments"] = fixed
+                                    repaired = True
+                                    logger.warning(
+                                        "Repaired malformed tool_call arguments for %s: %s → %s",
+                                        tc["function"].get("name", "?"),
+                                        raw_stripped[:80], fixed[:80],
+                                    )
+                                except json.JSONDecodeError:
+                                    pass
+
+                            if not repaired:
+                                # Last resort: replace with empty object so the
+                                # API request doesn't crash the entire session.
+                                tc["function"]["arguments"] = "{}"
+                                logger.warning(
+                                    "Unrepairable tool_call arguments for %s — "
+                                    "replaced with empty object (was: %s)",
+                                    tc["function"].get("name", "?"),
+                                    raw_stripped[:80],
+                                )
                     new_tcs.append(tc)
                 am["tool_calls"] = new_tcs