From ffc6d84f2762939d11cec4b0ee478e925134f441 Mon Sep 17 00:00:00 2001
From: netbrah <162479981+netbrah@users.noreply.github.com>
Date: Sun, 8 Mar 2026 08:16:22 -0400
Subject: [PATCH] fix: shallow copy input_schema to avoid caller mutation + add
 mutation guard test

Addresses Greptile review:
- dict(_input_schema) before mutation prevents cross-provider state leakage
- Test asserts original tool parameters dict is unchanged after call
---
 litellm/llms/anthropic/chat/transformation.py       |  7 +++++++
 .../chat/test_anthropic_chat_transformation.py      | 13 +++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/litellm/llms/anthropic/chat/transformation.py b/litellm/llms/anthropic/chat/transformation.py
index 41fcd3e752a..fd1859f7d17 100644
--- a/litellm/llms/anthropic/chat/transformation.py
+++ b/litellm/llms/anthropic/chat/transformation.py
@@ -399,6 +399,13 @@ class AnthropicConfig(AnthropicModelInfo, BaseConfig):
             # schemas from external sources (MCP servers, OpenAI callers) that
             # may omit the type field or use a non-object type.
             if _input_schema.get("type") != "object":
+                litellm.verbose_logger.debug(
+                    "_map_tool_helper: coercing input_schema type from %r to "
+                    "'object' for Anthropic compatibility (tool: %s)",
+                    _input_schema.get("type"),
+                    tool["function"].get("name"),
+                )
+                _input_schema = dict(_input_schema)  # avoid mutating caller's dict
                 _input_schema["type"] = "object"
                 if "properties" not in _input_schema:
                     _input_schema["properties"] = {}
diff --git a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
index a5388d19f2b..6f03f630b5f 100644
--- a/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
+++ b/tests/test_litellm/llms/anthropic/chat/test_anthropic_chat_transformation.py
@@ -3208,11 +3208,16 @@ def test_map_tool_helper_enforces_object_type_when_missing():
         },
     }
 
+    original_params = tool["function"]["parameters"].copy()
     result, _ = config._map_tool_helper(tool)
     assert result is not None
     assert result["input_schema"]["type"] == "object"
     assert "properties" in result["input_schema"]
     assert "query" in result["input_schema"]["properties"]
+    # Original parameters dict must not be modified in place
+    assert tool["function"]["parameters"] == original_params, (
+        "parameters dict was mutated; _map_tool_helper should not modify caller data"
+    )
 
 
 def test_map_tool_helper_enforces_object_type_when_wrong_type():
@@ -3234,9 +3239,17 @@ def test_map_tool_helper_enforces_object_type_when_wrong_type():
         },
     }
 
+    original_params = tool["function"]["parameters"].copy()
     result, _ = config._map_tool_helper(tool)
     assert result is not None
     assert result["input_schema"]["type"] == "object"
+    assert result["input_schema"].get("properties") == {}, (
+        "properties should be injected as {} when schema has non-object type and no properties key"
+    )
+    # Original parameters dict must not be modified in place
+    assert tool["function"]["parameters"] == original_params, (
+        "parameters dict was mutated; _map_tool_helper should not modify caller data"
+    )
 
 
 def test_map_tool_helper_preserves_valid_object_schema():