From ee237054ed3fba4c4d9a563af5707f5db092d9ad Mon Sep 17 00:00:00 2001
From: Timothy Oluwatobi Ojebiyi <tobiojebiyi@gmail.com>
Date: Sat, 16 May 2026 08:53:53 +0100
Subject: [PATCH] fix(transformation): prevent 'reasoning_effort' promotion for
 non-Claude models

---
 litellm/llms/github_copilot/chat/transformation.py |  5 ++++-
 .../test_github_copilot_transformation.py          | 14 ++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/litellm/llms/github_copilot/chat/transformation.py b/litellm/llms/github_copilot/chat/transformation.py
index b18ed73f073..24d18a1d52b 100644
--- a/litellm/llms/github_copilot/chat/transformation.py
+++ b/litellm/llms/github_copilot/chat/transformation.py
@@ -174,7 +174,10 @@ class GithubCopilotConfig(OpenAIConfig):
             else:
                 reasoning_effort = "minimal"
             optional_params["reasoning_effort"] = reasoning_effort
-        elif non_default_params.get("reasoning_effort") is not None:
+        elif (
+            "claude" in model.lower()
+            and non_default_params.get("reasoning_effort") is not None
+        ):
             optional_params["reasoning_effort"] = non_default_params.pop(
                 "reasoning_effort"
             )
diff --git a/tests/test_litellm/llms/github_copilot/test_github_copilot_transformation.py b/tests/test_litellm/llms/github_copilot/test_github_copilot_transformation.py
index 8d64b0030ca..cd51bc2b02c 100644
--- a/tests/test_litellm/llms/github_copilot/test_github_copilot_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/test_github_copilot_transformation.py
@@ -563,6 +563,20 @@ def test_map_openai_params_thinking_not_popped_for_non_claude_model():
     assert "reasoning_effort" not in optional_params
 
 
+def test_map_openai_params_reasoning_effort_not_promoted_for_non_claude_model():
+    """For non-Claude models, ``reasoning_effort`` must not be force-promoted
+    to ``optional_params``; the parent's supported-params filtering must run."""
+    config = GithubCopilotConfig()
+
+    optional_params = config.map_openai_params(
+        non_default_params={"reasoning_effort": "high"},
+        optional_params={},
+        model="gpt-4",
+        drop_params=True,
+    )
+    assert "reasoning_effort" not in optional_params
+
+
 def test_copilot_vision_request_header_with_image():
     """Test that Copilot-Vision-Request header is added when messages contain images"""
     config = GithubCopilotConfig()