diff --git a/litellm/llms/bedrock/chat/converse_transformation.py b/litellm/llms/bedrock/chat/converse_transformation.py
index ac3c92d1fed..23bf2d841dd 100644
--- a/litellm/llms/bedrock/chat/converse_transformation.py
+++ b/litellm/llms/bedrock/chat/converse_transformation.py
@@ -1300,10 +1300,12 @@ class AmazonConverseConfig(BaseConfig):
                     continue
                 filtered_tools.append(tool)
 
+        # Defensive copy so we don't mutate caller data (router fallback/retry may reuse optional_params).
         # Strip custom field from tools before sending to Bedrock Converse.
         # Claude Code sends custom: {eager_input_streaming: true} etc. which Anthropic
         # accepts but Bedrock rejects for some models (e.g. Haiku 4.5) with
         # "Extra inputs are not permitted". Ref: https://github.com/BerriAI/litellm/issues/23825
+        filtered_tools = [copy.deepcopy(t) for t in filtered_tools]
         strip_custom_from_tools_list(filtered_tools)
 
         # Only separate tools if computer use tools are actually present
diff --git a/litellm/llms/bedrock/common_utils.py b/litellm/llms/bedrock/common_utils.py
index 630808aa58b..e753dbc2bf9 100644
--- a/litellm/llms/bedrock/common_utils.py
+++ b/litellm/llms/bedrock/common_utils.py
@@ -62,10 +62,7 @@ def remove_custom_field_from_tools(request_body: dict) -> None:
 
     Ref: https://github.com/BerriAI/litellm/issues/22847
     """
-    tools = request_body.get("tools")
-    if not tools or not isinstance(tools, list):
-        return
-    strip_custom_from_tools_list(tools)
+    strip_custom_from_tools_list(request_body.get("tools"))
 
 
 def strip_custom_from_tools_list(tools: list) -> None:
diff --git a/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py b/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
index cff0d20cee8..944a9ae48d4 100644
--- a/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
+++ b/tests/test_litellm/llms/bedrock/chat/test_converse_transformation.py
@@ -354,8 +354,8 @@ def test_process_tools_and_beta_strips_custom_field():
     assert len(bedrock_tools) == 1
     assert "toolSpec" in bedrock_tools[0]
     assert bedrock_tools[0]["toolSpec"]["name"] == "get_weather"
-    # Original tools list should have been modified in-place (custom stripped)
-    assert "custom" not in tools_with_custom[0]
+    # Caller data should not be mutated (defensive copy used for router fallback safety)
+    assert "custom" in tools_with_custom[0]
 
 
 def test_transform_request_helper_includes_anthropic_beta_and_tools():