diff --git a/headroom/proxy/memory_tool_adapter.py b/headroom/proxy/memory_tool_adapter.py
index 1bf0d6c76..542b39c6f 100644
--- a/headroom/proxy/memory_tool_adapter.py
+++ b/headroom/proxy/memory_tool_adapter.py
@@ -791,13 +791,15 @@ class MemoryToolAdapter:
         if provider == "anthropic":
             return str(tool_call.get("name", ""))
         elif provider == "openai":
-            return str(tool_call.get("function", {}).get("name", ""))
+            return str((tool_call.get("function") or {}).get("name", ""))
         elif provider == "gemini":
-            func_call = tool_call.get("functionCall", {})
+            func_call = tool_call.get("functionCall") or {}
             return str(func_call.get("name", ""))
         else:
             # Generic - try both
-            return str(tool_call.get("name", "") or tool_call.get("function", {}).get("name", ""))
+            return str(
+                tool_call.get("name", "") or (tool_call.get("function") or {}).get("name", "")
+            )
 
     def _get_tool_id(self, tool_call: dict[str, Any], provider: Provider) -> str:
         """Get the tool call ID."""
@@ -807,7 +809,7 @@ class MemoryToolAdapter:
             return str(tool_call.get("id", ""))
         elif provider == "gemini":
             # Gemini doesn't use IDs in the same way
-            return str(tool_call.get("functionCall", {}).get("name", ""))
+            return str((tool_call.get("functionCall") or {}).get("name", ""))
         else:
             return str(tool_call.get("id", ""))
 
@@ -821,25 +823,28 @@ class MemoryToolAdapter:
             result = tool_call.get("input", {})
             return dict(result) if isinstance(result, dict) else {}
         elif provider == "openai":
-            args_str = tool_call.get("function", {}).get("arguments", "{}")
+            # `or {}` guards {"function": null}; `or "{}"` guards {"arguments": null}
+            # (json.loads(None) raises TypeError, which the bare JSONDecodeError
+            # catch would miss).
+            args_str = (tool_call.get("function") or {}).get("arguments") or "{}"
             try:
                 parsed = json.loads(args_str)
                 return dict(parsed) if isinstance(parsed, dict) else {}
-            except json.JSONDecodeError:
+            except (json.JSONDecodeError, TypeError):
                 return {}
         elif provider == "gemini":
-            result = tool_call.get("functionCall", {}).get("args", {})
+            result = (tool_call.get("functionCall") or {}).get("args", {})
             return dict(result) if isinstance(result, dict) else {}
         else:
             # Generic - try both
             if "input" in tool_call:
                 result = tool_call["input"]
                 return dict(result) if isinstance(result, dict) else {}
-            args_str = tool_call.get("function", {}).get("arguments", "{}")
+            args_str = (tool_call.get("function") or {}).get("arguments") or "{}"
             try:
                 parsed = json.loads(args_str)
                 return dict(parsed) if isinstance(parsed, dict) else {}
-            except json.JSONDecodeError:
+            except (json.JSONDecodeError, TypeError):
                 return {}
 
     async def handle_tool_calls(
diff --git a/tests/test_memory_tool_adapter_null_fields.py b/tests/test_memory_tool_adapter_null_fields.py
new file mode 100644
index 000000000..b3f6d4cc5
--- /dev/null
+++ b/tests/test_memory_tool_adapter_null_fields.py
@@ -0,0 +1,35 @@
+"""A tool call with a null ``function`` / ``arguments`` must not crash the
+memory tool adapter's provider-format parsing.
+
+``dict.get("function", {})`` returns ``None`` for a present-but-null key, so the
+following ``.get`` raised ``AttributeError``; a null ``arguments`` makes
+``json.loads(None)`` raise ``TypeError`` that the bare ``JSONDecodeError`` catch
+missed. Both are reachable from the untrusted upstream response. The parse
+helpers read only the ``tool_call`` argument, so we exercise them on a bare
+instance via ``object.__new__``.
+"""
+
+from __future__ import annotations
+
+from headroom.proxy.memory_tool_adapter import MemoryToolAdapter
+
+_adapter = object.__new__(MemoryToolAdapter)
+
+
+def test_get_tool_name_survives_null_function():
+    tc = {"id": "c1", "type": "function", "function": None}
+    assert _adapter._get_tool_name(tc, "openai") == ""
+    assert _adapter._get_tool_id(tc, "openai") == "c1"
+    assert _adapter._get_tool_input(tc, "openai") == {}
+
+
+def test_get_tool_input_survives_null_arguments():
+    # json.loads(None) raises TypeError, not JSONDecodeError.
+    tc = {"function": {"name": "memory_save", "arguments": None}}
+    assert _adapter._get_tool_input(tc, "openai") == {}
+
+
+def test_get_tool_helpers_still_parse_real_calls():
+    tc = {"function": {"name": "memory_save", "arguments": '{"content": "hi"}'}}
+    assert _adapter._get_tool_name(tc, "openai") == "memory_save"
+    assert _adapter._get_tool_input(tc, "openai") == {"content": "hi"}