From e98610e3813e2774b3fedefffa35029640a6f1d7 Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Sat, 16 May 2026 19:00:28 +0900
Subject: [PATCH 1/9] feat(github_copilot): route /v1/messages to Copilot
 native Anthropic endpoint

Add a GitHub Copilot Anthropic Messages transformation that routes supported Claude models through the native /v1/messages endpoint. This covers request URL construction, default headers, and supported model metadata.
---
 .../llms/github_copilot/messages/__init__.py  |   0
 .../github_copilot/messages/transformation.py |  81 ++++++++++++
 ...odel_prices_and_context_window_backup.json |   9 +-
 litellm/utils.py                              |   7 ++
 .../llms/github_copilot/messages/__init__.py  |   0
 ..._github_copilot_messages_transformation.py | 117 ++++++++++++++++++
 6 files changed, 211 insertions(+), 3 deletions(-)
 create mode 100644 litellm/llms/github_copilot/messages/__init__.py
 create mode 100644 litellm/llms/github_copilot/messages/transformation.py
 create mode 100644 tests/test_litellm/llms/github_copilot/messages/__init__.py
 create mode 100644 tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py

diff --git a/litellm/llms/github_copilot/messages/__init__.py b/litellm/llms/github_copilot/messages/__init__.py
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
new file mode 100644
index 000000000000..a30a81422302
--- /dev/null
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -0,0 +1,81 @@
+from typing import Any, List, Optional, Tuple
+
+from litellm.exceptions import AuthenticationError
+from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+    AnthropicMessagesConfig,
+)
+
+from ..authenticator import Authenticator
+from ..common_utils import (
+    DEFAULT_GITHUB_COPILOT_API_BASE,
+    GetAPIKeyError,
+    get_copilot_default_headers,
+)
+
+
+class GithubCopilotAnthropicMessagesConfig(AnthropicMessagesConfig):
+    """
+    GitHub Copilot implementation of Anthropic messages API.
+    Routes requests to Copilot's /v1/messages endpoint with appropriate authentication and headers.
+    """
+
+    def __init__(self) -> None:
+        super().__init__()
+        self.authenticator = Authenticator()
+
+    def validate_anthropic_messages_environment(
+        self,
+        headers: dict,
+        model: str,
+        messages: List[Any],
+        optional_params: dict,
+        litellm_params: dict,
+        api_key: Optional[str] = None,
+        api_base: Optional[str] = None,
+    ) -> Tuple[dict, Optional[str]]:
+        """
+        Validate environment for GitHub Copilot and add Copilot-specific headers.
+        """
+        # Get Copilot auth credentials
+        dynamic_api_base = (
+            api_base
+            or self.authenticator.get_api_base()
+            or DEFAULT_GITHUB_COPILOT_API_BASE
+        )
+        try:
+            dynamic_api_key = self.authenticator.get_api_key()
+        except GetAPIKeyError as e:
+            raise AuthenticationError(
+                model=model,
+                llm_provider="github_copilot",
+                message=str(e),
+            )
+
+        # Merge Copilot headers with provided headers
+        copilot_headers = get_copilot_default_headers(dynamic_api_key)
+        for key, value in copilot_headers.items():
+            if key not in headers:
+                headers[key] = value
+
+        # Set Anthropic version for messages API
+        if "anthropic-version" not in headers:
+            headers["anthropic-version"] = "2023-06-01"
+
+        return headers, dynamic_api_base
+
+    def get_complete_url(
+        self,
+        api_base: Optional[str],
+        api_key: Optional[str],
+        model: str,
+        optional_params: dict,
+        litellm_params: dict,
+        stream: Optional[bool] = None,
+    ) -> str:
+        """
+        Return the complete URL for GitHub Copilot /v1/messages endpoint.
+        """
+        api_base = api_base or DEFAULT_GITHUB_COPILOT_API_BASE
+        if not api_base.endswith("/v1/messages"):
+            api_base = f"{api_base}/v1/messages"
+        return api_base
diff --git a/litellm/model_prices_and_context_window_backup.json b/litellm/model_prices_and_context_window_backup.json
index b16e1015255e..c9dae4d9a473 100644
--- a/litellm/model_prices_and_context_window_backup.json
+++ b/litellm/model_prices_and_context_window_backup.json
@@ -19176,7 +19176,8 @@
         "max_tokens": 16000,
         "mode": "chat",
         "supported_endpoints": [
-            "/v1/chat/completions"
+            "/v1/chat/completions",
+            "/v1/messages"
         ],
         "supports_function_calling": true,
         "supports_parallel_function_calling": true,
@@ -19189,7 +19190,8 @@
         "max_tokens": 16000,
         "mode": "chat",
         "supported_endpoints": [
-            "/v1/chat/completions"
+            "/v1/chat/completions",
+            "/v1/messages"
         ],
         "supports_function_calling": true,
         "supports_parallel_function_calling": true,
@@ -19242,7 +19244,8 @@
         "max_tokens": 16000,
         "mode": "chat",
         "supported_endpoints": [
-            "/v1/chat/completions"
+            "/v1/chat/completions",
+            "/v1/messages"
         ],
         "supports_function_calling": true,
         "supports_parallel_function_calling": true,
diff --git a/litellm/utils.py b/litellm/utils.py
index 45ce5332f1d0..26d3ae32739a 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -7984,6 +7984,13 @@ def _get_provider_anthropic_messages_config_cached(
             )
 
             return DeepSeekAnthropicMessagesConfig()
+        elif litellm.LlmProviders.GITHUB_COPILOT == provider:
+            if "claude" in model_lower:
+                from litellm.llms.github_copilot.messages.transformation import (
+                    GithubCopilotAnthropicMessagesConfig,
+                )
+
+                return GithubCopilotAnthropicMessagesConfig()
         return None
 
     @staticmethod
diff --git a/tests/test_litellm/llms/github_copilot/messages/__init__.py b/tests/test_litellm/llms/github_copilot/messages/__init__.py
new file mode 100644
index 000000000000..e69de29bb2d1
diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
new file mode 100644
index 000000000000..78bd5a8b34d9
--- /dev/null
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -0,0 +1,117 @@
+import os
+import sys
+from unittest.mock import MagicMock
+
+import pytest
+
+sys.path.insert(0, os.path.abspath("../.."))
+
+from litellm.llms.github_copilot.messages.transformation import (
+    GithubCopilotAnthropicMessagesConfig,
+)
+from litellm.llms.github_copilot.common_utils import GetAPIKeyError
+
+
+def test_github_copilot_anthropic_messages_config_init():
+    """Test GithubCopilotAnthropicMessagesConfig initialization."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    assert config is not None
+    assert hasattr(config, "authenticator")
+
+
+def test_github_copilot_anthropic_messages_get_complete_url():
+    """Test URL construction for GitHub Copilot messages endpoint."""
+    config = GithubCopilotAnthropicMessagesConfig()
+
+    # Test with default api_base
+    url = config.get_complete_url(
+        api_base=None,
+        api_key=None,
+        model="github_copilot/claude-haiku-4.5",
+        optional_params={},
+        litellm_params={},
+    )
+    assert url == "https://api.githubcopilot.com/v1/messages"
+
+    # Test with custom api_base
+    url = config.get_complete_url(
+        api_base="https://custom.api.com",
+        api_key=None,
+        model="github_copilot/claude-haiku-4.5",
+        optional_params={},
+        litellm_params={},
+    )
+    assert url == "https://custom.api.com/v1/messages"
+
+    # Test with api_base already ending with /v1/messages
+    url = config.get_complete_url(
+        api_base="https://custom.api.com/v1/messages",
+        api_key=None,
+        model="github_copilot/claude-haiku-4.5",
+        optional_params={},
+        litellm_params={},
+    )
+    assert url == "https://custom.api.com/v1/messages"
+
+
+def test_github_copilot_anthropic_messages_validate_environment():
+    """Test environment validation and header injection."""
+    config = GithubCopilotAnthropicMessagesConfig()
+
+    # Mock the authenticator
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key-123"
+    config.authenticator.get_api_base.return_value = None
+
+    headers = {}
+    validated_headers, api_base = config.validate_anthropic_messages_environment(
+        headers=headers,
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={},
+        litellm_params={},
+        api_key=None,
+        api_base=None,
+    )
+
+    # Check that Copilot headers were added
+    assert "copilot-integration-id" in validated_headers
+    assert validated_headers["copilot-integration-id"] == "vscode-chat"
+    assert "Authorization" in validated_headers
+    assert "anthropic-version" in validated_headers
+    assert validated_headers["anthropic-version"] == "2023-06-01"
+    assert api_base == "https://api.githubcopilot.com"
+
+
+def test_github_copilot_anthropic_messages_validate_environment_auth_error():
+    """Test error handling when authentication fails."""
+    config = GithubCopilotAnthropicMessagesConfig()
+
+    # Mock the authenticator to raise an error
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.side_effect = GetAPIKeyError(
+        status_code=401, message="No valid API key found"
+    )
+
+    with pytest.raises(Exception):  # AuthenticationError
+        config.validate_anthropic_messages_environment(
+            headers={},
+            model="github_copilot/claude-haiku-4.5",
+            messages=[{"role": "user", "content": "Hello"}],
+            optional_params={},
+            litellm_params={},
+            api_key=None,
+            api_base=None,
+        )
+
+
+def test_github_copilot_anthropic_messages_supported_params():
+    """Test supported parameters list."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    params = config.get_supported_anthropic_messages_params("github_copilot/claude-haiku-4.5")
+
+    # Should inherit from AnthropicMessagesConfig
+    assert "messages" in params
+    assert "model" in params
+    assert "max_tokens" in params
+    assert "thinking" in params

From 538c80181bd907b65b0b04a72f7f6783d9add207 Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Sat, 16 May 2026 19:42:58 +0900
Subject: [PATCH 2/9] fix(github_copilot): address PR review feedback

Tighten the Anthropic Messages environment validation and web search interception behavior after review feedback. Avoid treating non-web-search requests as web-search-only paths.
---
 .../websearch_interception/handler.py         | 24 ++++++---
 .../github_copilot/messages/transformation.py | 30 ++++++++---
 ..._github_copilot_messages_transformation.py | 53 +++++++++++++++----
 3 files changed, 80 insertions(+), 27 deletions(-)

diff --git a/litellm/integrations/websearch_interception/handler.py b/litellm/integrations/websearch_interception/handler.py
index bfae6d5b7b0f..e360927ab3c4 100644
--- a/litellm/integrations/websearch_interception/handler.py
+++ b/litellm/integrations/websearch_interception/handler.py
@@ -126,17 +126,25 @@ async def try_short_circuit_search(
         # includes a follow-up LLM call to synthesize the answer from search
         # results.  Short-circuiting those would skip that synthesis step and
         # return raw search text — a regression for existing users.
+        #
+        # github_copilot is the exception: it has a BaseAnthropicMessagesConfig
+        # (added for thinking passthrough), but Copilot does not handle
+        # web_search tools natively, so we still need the short-circuit for
+        # web-search-only requests against Copilot.
         try:
             provider_enum = LlmProviders(provider_str)
-            anthropic_config = ProviderConfigManager.get_provider_anthropic_messages_config(
-                model=model, provider=provider_enum
-            )
-            if anthropic_config is not None:
-                verbose_logger.debug(
-                    f"WebSearchInterception: Skipping short-circuit for {provider_str} "
-                    "(provider has native Anthropic Messages support, using agentic loop)"
+            if provider_enum != LlmProviders.GITHUB_COPILOT:
+                anthropic_config = (
+                    ProviderConfigManager.get_provider_anthropic_messages_config(
+                        model=model, provider=provider_enum
+                    )
                 )
-                return None
+                if anthropic_config is not None:
+                    verbose_logger.debug(
+                        f"WebSearchInterception: Skipping short-circuit for {provider_str} "
+                        "(provider has native Anthropic Messages support, using agentic loop)"
+                    )
+                    return None
         except (ValueError, Exception):
             pass  # unknown provider enum → safe to short-circuit
 
diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index a30a81422302..17b72a52b49a 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -35,12 +35,15 @@ def validate_anthropic_messages_environment(
     ) -> Tuple[dict, Optional[str]]:
         """
         Validate environment for GitHub Copilot and add Copilot-specific headers.
+
+        The caller-supplied ``api_base`` is intentionally ignored. Routing this
+        request anywhere other than the authenticated Copilot endpoint would
+        leak the Copilot bearer token to a caller-controlled URL.
         """
-        # Get Copilot auth credentials
+        # Always use the Copilot endpoint resolved from the authenticated
+        # session, never the caller-supplied api_base.
         dynamic_api_base = (
-            api_base
-            or self.authenticator.get_api_base()
-            or DEFAULT_GITHUB_COPILOT_API_BASE
+            self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
         )
         try:
             dynamic_api_key = self.authenticator.get_api_key()
@@ -61,6 +64,12 @@ def validate_anthropic_messages_environment(
         if "anthropic-version" not in headers:
             headers["anthropic-version"] = "2023-06-01"
 
+        # Auto-inject anthropic-beta headers for advanced features
+        # (context_management, tool_search, output_format, speed)
+        headers = self._update_headers_with_anthropic_beta(
+            headers, optional_params, custom_llm_provider="github_copilot"
+        )
+
         return headers, dynamic_api_base
 
     def get_complete_url(
@@ -74,8 +83,13 @@ def get_complete_url(
     ) -> str:
         """
         Return the complete URL for GitHub Copilot /v1/messages endpoint.
+
+        The caller-supplied ``api_base`` is intentionally ignored to avoid
+        leaking the Copilot bearer token to a caller-controlled URL.
         """
-        api_base = api_base or DEFAULT_GITHUB_COPILOT_API_BASE
-        if not api_base.endswith("/v1/messages"):
-            api_base = f"{api_base}/v1/messages"
-        return api_base
+        resolved = (
+            self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
+        )
+        if not resolved.endswith("/v1/messages"):
+            resolved = f"{resolved}/v1/messages"
+        return resolved
diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index 78bd5a8b34d9..38e8a6bdfe13 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -6,10 +6,11 @@
 
 sys.path.insert(0, os.path.abspath("../.."))
 
+from litellm.exceptions import AuthenticationError
+from litellm.llms.github_copilot.common_utils import GetAPIKeyError
 from litellm.llms.github_copilot.messages.transformation import (
     GithubCopilotAnthropicMessagesConfig,
 )
-from litellm.llms.github_copilot.common_utils import GetAPIKeyError
 
 
 def test_github_copilot_anthropic_messages_config_init():
@@ -20,10 +21,12 @@ def test_github_copilot_anthropic_messages_config_init():
 
 
 def test_github_copilot_anthropic_messages_get_complete_url():
-    """Test URL construction for GitHub Copilot messages endpoint."""
+    """URL is always resolved from the authenticator, never the caller."""
     config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_base.return_value = None
 
-    # Test with default api_base
+    # No api_base supplied -> default Copilot endpoint
     url = config.get_complete_url(
         api_base=None,
         api_key=None,
@@ -33,25 +36,28 @@ def test_github_copilot_anthropic_messages_get_complete_url():
     )
     assert url == "https://api.githubcopilot.com/v1/messages"
 
-    # Test with custom api_base
+    # Caller-supplied api_base must be ignored (token-exfiltration guard).
     url = config.get_complete_url(
-        api_base="https://custom.api.com",
+        api_base="https://attacker.example.com",
         api_key=None,
         model="github_copilot/claude-haiku-4.5",
         optional_params={},
         litellm_params={},
     )
-    assert url == "https://custom.api.com/v1/messages"
+    assert url == "https://api.githubcopilot.com/v1/messages"
 
-    # Test with api_base already ending with /v1/messages
+    # Authenticator-provided base is honored (e.g. business/enterprise tenants).
+    config.authenticator.get_api_base.return_value = (
+        "https://api.business.githubcopilot.com"
+    )
     url = config.get_complete_url(
-        api_base="https://custom.api.com/v1/messages",
+        api_base="https://attacker.example.com",
         api_key=None,
         model="github_copilot/claude-haiku-4.5",
         optional_params={},
         litellm_params={},
     )
-    assert url == "https://custom.api.com/v1/messages"
+    assert url == "https://api.business.githubcopilot.com/v1/messages"
 
 
 def test_github_copilot_anthropic_messages_validate_environment():
@@ -64,6 +70,7 @@ def test_github_copilot_anthropic_messages_validate_environment():
     config.authenticator.get_api_base.return_value = None
 
     headers = {}
+    # Pass a hostile api_base to confirm it is ignored.
     validated_headers, api_base = config.validate_anthropic_messages_environment(
         headers=headers,
         model="github_copilot/claude-haiku-4.5",
@@ -71,7 +78,7 @@ def test_github_copilot_anthropic_messages_validate_environment():
         optional_params={},
         litellm_params={},
         api_key=None,
-        api_base=None,
+        api_base="https://attacker.example.com",
     )
 
     # Check that Copilot headers were added
@@ -80,9 +87,33 @@ def test_github_copilot_anthropic_messages_validate_environment():
     assert "Authorization" in validated_headers
     assert "anthropic-version" in validated_headers
     assert validated_headers["anthropic-version"] == "2023-06-01"
+    # api_base must come from the authenticator, never the caller.
     assert api_base == "https://api.githubcopilot.com"
 
 
+def test_github_copilot_anthropic_messages_validate_environment_injects_beta_headers():
+    """Anthropic-beta headers must be auto-injected for advanced features
+    (context_management, output_format, etc.) — matches the parent
+    AnthropicMessagesConfig contract."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key"
+    config.authenticator.get_api_base.return_value = None
+
+    validated_headers, _ = config.validate_anthropic_messages_environment(
+        headers={},
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={"output_format": {"type": "json_object"}},
+        litellm_params={},
+        api_key=None,
+        api_base=None,
+    )
+
+    assert "anthropic-beta" in validated_headers
+    assert "structured-outputs-2025-11-13" in validated_headers["anthropic-beta"]
+
+
 def test_github_copilot_anthropic_messages_validate_environment_auth_error():
     """Test error handling when authentication fails."""
     config = GithubCopilotAnthropicMessagesConfig()
@@ -93,7 +124,7 @@ def test_github_copilot_anthropic_messages_validate_environment_auth_error():
         status_code=401, message="No valid API key found"
     )
 
-    with pytest.raises(Exception):  # AuthenticationError
+    with pytest.raises(AuthenticationError):
         config.validate_anthropic_messages_environment(
             headers={},
             model="github_copilot/claude-haiku-4.5",

From c1ffdcaa9c7a904d3d2372809eea490768b41a1e Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Sat, 16 May 2026 19:49:02 +0900
Subject: [PATCH 3/9] style(github_copilot): apply black formatting

Apply Black formatting to the GitHub Copilot Anthropic Messages tests.
---
 litellm/llms/github_copilot/messages/transformation.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index 17b72a52b49a..036544a0cd93 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -87,9 +87,7 @@ def get_complete_url(
         The caller-supplied ``api_base`` is intentionally ignored to avoid
         leaking the Copilot bearer token to a caller-controlled URL.
         """
-        resolved = (
-            self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
-        )
+        resolved = self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
         if not resolved.endswith("/v1/messages"):
             resolved = f"{resolved}/v1/messages"
         return resolved

From 88ef1365b2099cd4024a5d3819c9d37dfda2401d Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Sat, 16 May 2026 23:51:39 +0900
Subject: [PATCH 4/9] test(github_copilot): cover ProviderConfigManager
 dispatch for Anthropic Messages

Add coverage for ProviderConfigManager dispatch when GitHub Copilot models use the Anthropic Messages API, including non-Anthropic models returning no config.
---
 ..._github_copilot_messages_transformation.py | 32 ++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index 38e8a6bdfe13..d4bd01e40926 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -139,10 +139,40 @@ def test_github_copilot_anthropic_messages_validate_environment_auth_error():
 def test_github_copilot_anthropic_messages_supported_params():
     """Test supported parameters list."""
     config = GithubCopilotAnthropicMessagesConfig()
-    params = config.get_supported_anthropic_messages_params("github_copilot/claude-haiku-4.5")
+    params = config.get_supported_anthropic_messages_params(
+        "github_copilot/claude-haiku-4.5"
+    )
 
     # Should inherit from AnthropicMessagesConfig
     assert "messages" in params
     assert "model" in params
     assert "max_tokens" in params
     assert "thinking" in params
+
+
+def test_provider_config_manager_dispatches_claude_to_copilot_messages_config():
+    """ProviderConfigManager must return the Copilot Anthropic Messages config
+    for Claude models served via github_copilot."""
+    from litellm.types.utils import LlmProviders
+    from litellm.utils import ProviderConfigManager
+
+    config = ProviderConfigManager.get_provider_anthropic_messages_config(
+        model="github_copilot/claude-haiku-4.5",
+        provider=LlmProviders.GITHUB_COPILOT,
+    )
+
+    assert isinstance(config, GithubCopilotAnthropicMessagesConfig)
+
+
+def test_provider_config_manager_skips_non_claude_copilot_models():
+    """Non-Claude github_copilot models (e.g. gpt-*) must not be routed through
+    the Anthropic Messages dispatch."""
+    from litellm.types.utils import LlmProviders
+    from litellm.utils import ProviderConfigManager
+
+    config = ProviderConfigManager.get_provider_anthropic_messages_config(
+        model="github_copilot/gpt-5-mini",
+        provider=LlmProviders.GITHUB_COPILOT,
+    )
+
+    assert config is None

From 518b0a123715aed6cdfede98ed9c4d06936e8005 Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Thu, 11 Jun 2026 04:34:22 +0900
Subject: [PATCH 5/9] fix(github_copilot): apply messages-proxy intent header
 to /v1/messages

Set the messages-proxy interaction header for GitHub Copilot Anthropic Messages requests so /v1/messages uses the expected Copilot intent.
---
 .../github_copilot/messages/transformation.py |  9 ++-
 ..._github_copilot_messages_transformation.py | 55 ++++++++++++++++++-
 2 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index 036544a0cd93..35ee168ef545 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -12,6 +12,8 @@
     get_copilot_default_headers,
 )
 
+_MESSAGES_PROXY_API_VERSION = "2026-06-01"
+
 
 class GithubCopilotAnthropicMessagesConfig(AnthropicMessagesConfig):
     """
@@ -60,12 +62,13 @@ def validate_anthropic_messages_environment(
             if key not in headers:
                 headers[key] = value
 
-        # Set Anthropic version for messages API
+        headers["openai-intent"] = "messages-proxy"
+        headers["x-interaction-type"] = "messages-proxy"
+        headers["x-github-api-version"] = _MESSAGES_PROXY_API_VERSION
+
         if "anthropic-version" not in headers:
             headers["anthropic-version"] = "2023-06-01"
 
-        # Auto-inject anthropic-beta headers for advanced features
-        # (context_management, tool_search, output_format, speed)
         headers = self._update_headers_with_anthropic_beta(
             headers, optional_params, custom_llm_provider="github_copilot"
         )
diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index d4bd01e40926..9e5cc51bb1ef 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -81,13 +81,16 @@ def test_github_copilot_anthropic_messages_validate_environment():
         api_base="https://attacker.example.com",
     )
 
-    # Check that Copilot headers were added
     assert "copilot-integration-id" in validated_headers
     assert validated_headers["copilot-integration-id"] == "vscode-chat"
     assert "Authorization" in validated_headers
     assert "anthropic-version" in validated_headers
     assert validated_headers["anthropic-version"] == "2023-06-01"
-    # api_base must come from the authenticator, never the caller.
+    # /v1/messages must use the messages-proxy intent so the Copilot backend
+    # enables Anthropic-native features (context_management, thinking, etc.).
+    assert validated_headers["openai-intent"] == "messages-proxy"
+    assert validated_headers["x-interaction-type"] == "messages-proxy"
+    assert validated_headers["x-github-api-version"] == "2026-06-01"
     assert api_base == "https://api.githubcopilot.com"
 
 
@@ -114,6 +117,54 @@ def test_github_copilot_anthropic_messages_validate_environment_injects_beta_hea
     assert "structured-outputs-2025-11-13" in validated_headers["anthropic-beta"]
 
 
+def test_github_copilot_anthropic_messages_validate_environment_preserves_caller_anthropic_version():
+    """Caller-supplied anthropic-version must be forwarded verbatim."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key"
+    config.authenticator.get_api_base.return_value = None
+
+    validated_headers, _ = config.validate_anthropic_messages_environment(
+        headers={"anthropic-version": "2024-10-22"},
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={},
+        litellm_params={},
+        api_key=None,
+        api_base=None,
+    )
+
+    assert validated_headers["anthropic-version"] == "2024-10-22"
+
+
+def test_github_copilot_anthropic_messages_validate_environment_injects_context_management_beta():
+    """context_management in optional_params must trigger the corresponding
+    anthropic-beta header so the Copilot backend accepts the field."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key"
+    config.authenticator.get_api_base.return_value = None
+
+    validated_headers, _ = config.validate_anthropic_messages_environment(
+        headers={},
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={
+            "context_management": {
+                "edits": [{"type": "clear_tool_uses_20250919"}]
+            }
+        },
+        litellm_params={},
+        api_key=None,
+        api_base=None,
+    )
+
+    assert validated_headers["openai-intent"] == "messages-proxy"
+    assert validated_headers["x-interaction-type"] == "messages-proxy"
+    assert "anthropic-beta" in validated_headers
+    assert "context-management-2025-06-27" in validated_headers["anthropic-beta"]
+
+
 def test_github_copilot_anthropic_messages_validate_environment_auth_error():
     """Test error handling when authentication fails."""
     config = GithubCopilotAnthropicMessagesConfig()

From 0e0eff97ee05a1f1ce11794cf14083963b67d6d1 Mon Sep 17 00:00:00 2001
From: ririnto <ririnto@kakao.com>
Date: Sat, 20 Jun 2026 21:14:31 +0900
Subject: [PATCH 6/9] fix(github_copilot): use modern generic annotations

Replace legacy typing generics in the GitHub Copilot Anthropic Messages transformation so the strict Ruff budget gate stays within its ceiling.
---
 litellm/integrations/websearch_interception/handler.py |  6 ++----
 litellm/llms/github_copilot/messages/transformation.py | 10 ++++------
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/litellm/integrations/websearch_interception/handler.py b/litellm/integrations/websearch_interception/handler.py
index e360927ab3c4..ef2fd1354456 100644
--- a/litellm/integrations/websearch_interception/handler.py
+++ b/litellm/integrations/websearch_interception/handler.py
@@ -134,10 +134,8 @@ async def try_short_circuit_search(
         try:
             provider_enum = LlmProviders(provider_str)
             if provider_enum != LlmProviders.GITHUB_COPILOT:
-                anthropic_config = (
-                    ProviderConfigManager.get_provider_anthropic_messages_config(
-                        model=model, provider=provider_enum
-                    )
+                anthropic_config = ProviderConfigManager.get_provider_anthropic_messages_config(
+                    model=model, provider=provider_enum
                 )
                 if anthropic_config is not None:
                     verbose_logger.debug(
diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index 35ee168ef545..60b0e6d54f14 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -1,4 +1,4 @@
-from typing import Any, List, Optional, Tuple
+from typing import Any, Optional
 
 from litellm.exceptions import AuthenticationError
 from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
@@ -29,12 +29,12 @@ def validate_anthropic_messages_environment(
         self,
         headers: dict,
         model: str,
-        messages: List[Any],
+        messages: list[Any],
         optional_params: dict,
         litellm_params: dict,
         api_key: Optional[str] = None,
         api_base: Optional[str] = None,
-    ) -> Tuple[dict, Optional[str]]:
+    ) -> tuple[dict, Optional[str]]:
         """
         Validate environment for GitHub Copilot and add Copilot-specific headers.
 
@@ -44,9 +44,7 @@ def validate_anthropic_messages_environment(
         """
         # Always use the Copilot endpoint resolved from the authenticated
         # session, never the caller-supplied api_base.
-        dynamic_api_base = (
-            self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
-        )
+        dynamic_api_base = self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
         try:
             dynamic_api_key = self.authenticator.get_api_key()
         except GetAPIKeyError as e:

From ada5fcc9a17779ad53accd200e61139bd146b99b Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Wed, 1 Jul 2026 04:30:27 +0000
Subject: [PATCH 7/9] refactor(github_copilot): decouple web-search
 short-circuit and harden /v1/messages URL

Address review feedback on the Copilot native Anthropic messages path.

Replace the hardcoded LlmProviders.GITHUB_COPILOT check in the web-search
interception handler with a handles_web_search_natively() method on
BaseAnthropicMessagesConfig (default True), overridden to False in
GithubCopilotAnthropicMessagesConfig. Provider-specific behavior now lives in
llms/ and the handler stays provider-agnostic, so a future provider in the same
situation needs no carve-out here.

In get_complete_url, reuse the already-resolved api_base returned by
validate_anthropic_messages_environment instead of reading the authenticator a
second time, removing redundant I/O and the mid-request inconsistency window.
The caller-supplied base is still discarded in validate, which is the security
boundary. Normalize a trailing slash on the base in both methods so a
tenant-specific host never yields a double-slash //v1/messages URL.
---
 .../websearch_interception/handler.py         | 37 ++++----
 .../anthropic_messages/transformation.py      | 13 +++
 .../github_copilot/messages/transformation.py | 24 ++++--
 ..._github_copilot_messages_transformation.py | 86 +++++++++++++++++--
 4 files changed, 129 insertions(+), 31 deletions(-)

diff --git a/litellm/integrations/websearch_interception/handler.py b/litellm/integrations/websearch_interception/handler.py
index ef2fd1354456..60100e8c2fdd 100644
--- a/litellm/integrations/websearch_interception/handler.py
+++ b/litellm/integrations/websearch_interception/handler.py
@@ -120,29 +120,28 @@ async def try_short_circuit_search(
         if self.enabled_providers is not None and provider_str not in self.enabled_providers:
             return None
 
-        # Only short-circuit for providers without native Anthropic Messages
-        # support.  Providers that have a BaseAnthropicMessagesConfig (bedrock,
-        # vertex_ai, azure_ai, anthropic) already use the agentic loop, which
-        # includes a follow-up LLM call to synthesize the answer from search
-        # results.  Short-circuiting those would skip that synthesis step and
-        # return raw search text — a regression for existing users.
+        # Only short-circuit for providers whose Anthropic Messages agentic loop
+        # does not run web_search itself. Providers that have a
+        # BaseAnthropicMessagesConfig which handles web search natively (bedrock,
+        # vertex_ai, azure_ai, anthropic) already perform the search plus a
+        # follow-up LLM synthesis step; short-circuiting those would skip that
+        # synthesis and return raw search text — a regression for existing users.
         #
-        # github_copilot is the exception: it has a BaseAnthropicMessagesConfig
-        # (added for thinking passthrough), but Copilot does not handle
-        # web_search tools natively, so we still need the short-circuit for
-        # web-search-only requests against Copilot.
+        # github_copilot has a BaseAnthropicMessagesConfig (added for thinking
+        # passthrough) but does not handle web_search natively, so its config
+        # returns handles_web_search_natively() == False and we still short-circuit
+        # web-search-only requests against it.
         try:
             provider_enum = LlmProviders(provider_str)
-            if provider_enum != LlmProviders.GITHUB_COPILOT:
-                anthropic_config = ProviderConfigManager.get_provider_anthropic_messages_config(
-                    model=model, provider=provider_enum
+            anthropic_config = ProviderConfigManager.get_provider_anthropic_messages_config(
+                model=model, provider=provider_enum
+            )
+            if anthropic_config is not None and anthropic_config.handles_web_search_natively():
+                verbose_logger.debug(
+                    f"WebSearchInterception: Skipping short-circuit for {provider_str} "
+                    "(provider handles web search natively via the agentic loop)"
                 )
-                if anthropic_config is not None:
-                    verbose_logger.debug(
-                        f"WebSearchInterception: Skipping short-circuit for {provider_str} "
-                        "(provider has native Anthropic Messages support, using agentic loop)"
-                    )
-                    return None
+                return None
         except (ValueError, Exception):
             pass  # unknown provider enum → safe to short-circuit
 
diff --git a/litellm/llms/base_llm/anthropic_messages/transformation.py b/litellm/llms/base_llm/anthropic_messages/transformation.py
index 966995bc571f..448c1d070096 100644
--- a/litellm/llms/base_llm/anthropic_messages/transformation.py
+++ b/litellm/llms/base_llm/anthropic_messages/transformation.py
@@ -114,6 +114,19 @@ def should_filter_anthropic_beta_headers(self) -> bool:
         """
         return True
 
+    def handles_web_search_natively(self) -> bool:
+        """
+        Whether the upstream this config routes to executes ``web_search`` tools
+        itself as part of its Anthropic Messages agentic loop.
+
+        The web-search interception handler short-circuits web-search-only
+        requests (running the search itself and returning synthetic results) only
+        for providers that do NOT. Providers whose agentic loop already performs
+        the search plus a follow-up synthesis step (bedrock, vertex_ai, ...)
+        return True so those requests flow through untouched.
+        """
+        return True
+
     def get_async_streaming_response_iterator(
         self,
         model: str,
diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index 60b0e6d54f14..f787a01ff62f 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -25,6 +25,14 @@ def __init__(self) -> None:
         super().__init__()
         self.authenticator = Authenticator()
 
+    def handles_web_search_natively(self) -> bool:
+        """
+        Copilot's /v1/messages endpoint does not execute ``web_search`` tools, so
+        the interception handler must short-circuit web-search-only requests
+        instead of routing them here.
+        """
+        return False
+
     def validate_anthropic_messages_environment(
         self,
         headers: dict,
@@ -43,8 +51,10 @@ def validate_anthropic_messages_environment(
         leak the Copilot bearer token to a caller-controlled URL.
         """
         # Always use the Copilot endpoint resolved from the authenticated
-        # session, never the caller-supplied api_base.
-        dynamic_api_base = self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
+        # session, never the caller-supplied api_base. rstrip so a
+        # tenant-specific base with a trailing slash does not yield a
+        # double-slash URL once "/v1/messages" is appended downstream.
+        dynamic_api_base = (self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE).rstrip("/")
         try:
             dynamic_api_key = self.authenticator.get_api_key()
         except GetAPIKeyError as e:
@@ -85,10 +95,14 @@ def get_complete_url(
         """
         Return the complete URL for GitHub Copilot /v1/messages endpoint.
 
-        The caller-supplied ``api_base`` is intentionally ignored to avoid
-        leaking the Copilot bearer token to a caller-controlled URL.
+        ``api_base`` here is the value already resolved by
+        ``validate_anthropic_messages_environment`` (the authenticated Copilot
+        host), not the raw caller-supplied base — that one is discarded there to
+        avoid leaking the Copilot bearer token to a caller-controlled URL. We
+        reuse it to avoid a second authenticator read, falling back to a fresh
+        resolution only if it was not provided.
         """
-        resolved = self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE
+        resolved = (api_base or self.authenticator.get_api_base() or DEFAULT_GITHUB_COPILOT_API_BASE).rstrip("/")
         if not resolved.endswith("/v1/messages"):
             resolved = f"{resolved}/v1/messages"
         return resolved
diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index 9e5cc51bb1ef..6c74955a4b9d 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -21,12 +21,17 @@ def test_github_copilot_anthropic_messages_config_init():
 
 
 def test_github_copilot_anthropic_messages_get_complete_url():
-    """URL is always resolved from the authenticator, never the caller."""
+    """get_complete_url builds the /v1/messages URL from the base it is handed.
+
+    In the request flow that ``api_base`` is the value already resolved by
+    validate_anthropic_messages_environment (the authenticated Copilot host); the
+    caller-supplied base is discarded there, not here (see the validate tests).
+    """
     config = GithubCopilotAnthropicMessagesConfig()
     config.authenticator = MagicMock()
     config.authenticator.get_api_base.return_value = None
 
-    # No api_base supplied -> default Copilot endpoint
+    # No api_base supplied and no authenticator base -> default Copilot endpoint.
     url = config.get_complete_url(
         api_base=None,
         api_key=None,
@@ -35,10 +40,34 @@ def test_github_copilot_anthropic_messages_get_complete_url():
         litellm_params={},
     )
     assert url == "https://api.githubcopilot.com/v1/messages"
+    # Falls back to a single authenticator read, not a hard-coded second one.
+    config.authenticator.get_api_base.assert_called()
 
-    # Caller-supplied api_base must be ignored (token-exfiltration guard).
+    # The resolved (validated) base passed in is reused verbatim; no extra read.
+    config.authenticator.get_api_base.reset_mock()
     url = config.get_complete_url(
-        api_base="https://attacker.example.com",
+        api_base="https://api.business.githubcopilot.com",
+        api_key=None,
+        model="github_copilot/claude-haiku-4.5",
+        optional_params={},
+        litellm_params={},
+    )
+    assert url == "https://api.business.githubcopilot.com/v1/messages"
+    config.authenticator.get_api_base.assert_not_called()
+
+    # A trailing slash on the base must not produce a double-slash URL.
+    url = config.get_complete_url(
+        api_base="https://api.business.githubcopilot.com/",
+        api_key=None,
+        model="github_copilot/claude-haiku-4.5",
+        optional_params={},
+        litellm_params={},
+    )
+    assert url == "https://api.business.githubcopilot.com/v1/messages"
+
+    # An already-complete /v1/messages base is left untouched.
+    url = config.get_complete_url(
+        api_base="https://api.githubcopilot.com/v1/messages",
         api_key=None,
         model="github_copilot/claude-haiku-4.5",
         optional_params={},
@@ -46,12 +75,18 @@ def test_github_copilot_anthropic_messages_get_complete_url():
     )
     assert url == "https://api.githubcopilot.com/v1/messages"
 
-    # Authenticator-provided base is honored (e.g. business/enterprise tenants).
+
+def test_github_copilot_anthropic_messages_get_complete_url_normalizes_authenticator_trailing_slash():
+    """A tenant base with a trailing slash from the authenticator fallback must
+    not yield a double-slash URL."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
     config.authenticator.get_api_base.return_value = (
-        "https://api.business.githubcopilot.com"
+        "https://api.business.githubcopilot.com/"
     )
+
     url = config.get_complete_url(
-        api_base="https://attacker.example.com",
+        api_base=None,
         api_key=None,
         model="github_copilot/claude-haiku-4.5",
         optional_params={},
@@ -227,3 +262,40 @@ def test_provider_config_manager_skips_non_claude_copilot_models():
     )
 
     assert config is None
+
+
+def test_github_copilot_anthropic_messages_validate_environment_normalizes_trailing_slash():
+    """A tenant base with a trailing slash from the authenticator must be
+    normalized so the URL built downstream has no double slash."""
+    config = GithubCopilotAnthropicMessagesConfig()
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key"
+    config.authenticator.get_api_base.return_value = (
+        "https://api.business.githubcopilot.com/"
+    )
+
+    _, api_base = config.validate_anthropic_messages_environment(
+        headers={},
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={},
+        litellm_params={},
+        api_key=None,
+        api_base="https://attacker.example.com",
+    )
+
+    assert api_base == "https://api.business.githubcopilot.com"
+
+
+def test_github_copilot_config_does_not_handle_web_search_natively():
+    """Copilot's /v1/messages does not run web_search, so its config must report
+    handles_web_search_natively() == False. This is what keeps the web-search
+    interception handler short-circuiting Copilot instead of routing to it, even
+    though Copilot now has a BaseAnthropicMessagesConfig. The base Anthropic
+    config (bedrock/vertex/anthropic path) must report True."""
+    from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+        AnthropicMessagesConfig,
+    )
+
+    assert GithubCopilotAnthropicMessagesConfig().handles_web_search_natively() is False
+    assert AnthropicMessagesConfig().handles_web_search_natively() is True

From 210bc94cb73728ddd80e010264f3a5bbe50e167b Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Wed, 1 Jul 2026 04:45:06 +0000
Subject: [PATCH 8/9] fix(github_copilot): forward anthropic-beta headers on
 /v1/messages

The Copilot config inherited should_filter_anthropic_beta_headers()==True
from BaseAnthropicMessagesConfig, so update_headers_with_filtered_beta
stripped every anthropic-beta value after validate_anthropic_messages_environment
injected them (github_copilot has no mapping in
anthropic_beta_headers_config.json). That silently disabled header-gated
features like context_management and structured outputs on the native
passthrough. Override the hook to False, matching OpenAILikeAnthropicMessagesConfig.
---
 .../github_copilot/messages/transformation.py | 10 +++++
 ..._github_copilot_messages_transformation.py | 37 +++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/litellm/llms/github_copilot/messages/transformation.py b/litellm/llms/github_copilot/messages/transformation.py
index f787a01ff62f..fb3f0a4e1596 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -33,6 +33,16 @@ def handles_web_search_natively(self) -> bool:
         """
         return False
 
+    def should_filter_anthropic_beta_headers(self) -> bool:
+        """
+        Copilot's /v1/messages is a native Anthropic Messages passthrough, so
+        ``anthropic-beta`` values injected by ``_update_headers_with_anthropic_beta``
+        (context_management, structured outputs, ...) must reach the upstream
+        verbatim. The default provider-scoped filter would drop them because
+        github_copilot has no entry in ``anthropic_beta_headers_config.json``.
+        """
+        return False
+
     def validate_anthropic_messages_environment(
         self,
         headers: dict,
diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index 6c74955a4b9d..7168eefc588f 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -287,6 +287,43 @@ def test_github_copilot_anthropic_messages_validate_environment_normalizes_trail
     assert api_base == "https://api.business.githubcopilot.com"
 
 
+def test_github_copilot_config_disables_anthropic_beta_filtering():
+    """Copilot's /v1/messages is a native Anthropic passthrough, so injected
+    anthropic-beta values (context_management, structured outputs, ...) must be
+    forwarded verbatim. The default provider-scoped filter would drop them
+    because github_copilot has no entry in the beta headers config; a regression
+    here would silently disable header-gated Anthropic features for Copilot."""
+    from litellm.anthropic_beta_headers_manager import update_headers_with_filtered_beta
+    from litellm.llms.anthropic.experimental_pass_through.messages.transformation import (
+        AnthropicMessagesConfig,
+    )
+
+    config = GithubCopilotAnthropicMessagesConfig()
+    assert config.should_filter_anthropic_beta_headers() is False
+    assert AnthropicMessagesConfig().should_filter_anthropic_beta_headers() is True
+
+    config.authenticator = MagicMock()
+    config.authenticator.get_api_key.return_value = "gh.test-key"
+    config.authenticator.get_api_base.return_value = None
+
+    headers, _ = config.validate_anthropic_messages_environment(
+        headers={},
+        model="github_copilot/claude-haiku-4.5",
+        messages=[{"role": "user", "content": "Hello"}],
+        optional_params={
+            "context_management": {"edits": [{"type": "clear_tool_uses_20250919"}]}
+        },
+        litellm_params={},
+        api_key=None,
+        api_base=None,
+    )
+
+    assert "context-management-2025-06-27" in headers["anthropic-beta"]
+    if config.should_filter_anthropic_beta_headers():
+        headers = update_headers_with_filtered_beta(headers=dict(headers), provider="github_copilot")
+    assert "context-management-2025-06-27" in headers.get("anthropic-beta", "")
+
+
 def test_github_copilot_config_does_not_handle_web_search_natively():
     """Copilot's /v1/messages does not run web_search, so its config must report
     handles_web_search_natively() == False. This is what keeps the web-search

From 54bff776da18970e65e88cad134f590a0142730a Mon Sep 17 00:00:00 2001
From: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
Date: Wed, 1 Jul 2026 06:44:52 +0000
Subject: [PATCH 9/9] test(github_copilot): remove dead branch in beta-header
 regression test

The anthropic-beta filtering test guarded the fix with an if branch on
should_filter_anthropic_beta_headers(), which is always False, so the branch was
unreachable. Replace it with a direct assertion that running the provider-scoped
filter for github_copilot strips every beta value, proving why the override is
load-bearing and catching a regression that flips it back on.
---
 ..._github_copilot_messages_transformation.py | 36 +++++++------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
index 7168eefc588f..01787c07d272 100644
--- a/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
+++ b/tests/test_litellm/llms/github_copilot/messages/test_github_copilot_messages_transformation.py
@@ -81,9 +81,7 @@ def test_github_copilot_anthropic_messages_get_complete_url_normalizes_authentic
     not yield a double-slash URL."""
     config = GithubCopilotAnthropicMessagesConfig()
     config.authenticator = MagicMock()
-    config.authenticator.get_api_base.return_value = (
-        "https://api.business.githubcopilot.com/"
-    )
+    config.authenticator.get_api_base.return_value = "https://api.business.githubcopilot.com/"
 
     url = config.get_complete_url(
         api_base=None,
@@ -184,11 +182,7 @@ def test_github_copilot_anthropic_messages_validate_environment_injects_context_
         headers={},
         model="github_copilot/claude-haiku-4.5",
         messages=[{"role": "user", "content": "Hello"}],
-        optional_params={
-            "context_management": {
-                "edits": [{"type": "clear_tool_uses_20250919"}]
-            }
-        },
+        optional_params={"context_management": {"edits": [{"type": "clear_tool_uses_20250919"}]}},
         litellm_params={},
         api_key=None,
         api_base=None,
@@ -206,9 +200,7 @@ def test_github_copilot_anthropic_messages_validate_environment_auth_error():
 
     # Mock the authenticator to raise an error
     config.authenticator = MagicMock()
-    config.authenticator.get_api_key.side_effect = GetAPIKeyError(
-        status_code=401, message="No valid API key found"
-    )
+    config.authenticator.get_api_key.side_effect = GetAPIKeyError(status_code=401, message="No valid API key found")
 
     with pytest.raises(AuthenticationError):
         config.validate_anthropic_messages_environment(
@@ -225,9 +217,7 @@ def test_github_copilot_anthropic_messages_validate_environment_auth_error():
 def test_github_copilot_anthropic_messages_supported_params():
     """Test supported parameters list."""
     config = GithubCopilotAnthropicMessagesConfig()
-    params = config.get_supported_anthropic_messages_params(
-        "github_copilot/claude-haiku-4.5"
-    )
+    params = config.get_supported_anthropic_messages_params("github_copilot/claude-haiku-4.5")
 
     # Should inherit from AnthropicMessagesConfig
     assert "messages" in params
@@ -270,9 +260,7 @@ def test_github_copilot_anthropic_messages_validate_environment_normalizes_trail
     config = GithubCopilotAnthropicMessagesConfig()
     config.authenticator = MagicMock()
     config.authenticator.get_api_key.return_value = "gh.test-key"
-    config.authenticator.get_api_base.return_value = (
-        "https://api.business.githubcopilot.com/"
-    )
+    config.authenticator.get_api_base.return_value = "https://api.business.githubcopilot.com/"
 
     _, api_base = config.validate_anthropic_messages_environment(
         headers={},
@@ -310,18 +298,20 @@ def test_github_copilot_config_disables_anthropic_beta_filtering():
         headers={},
         model="github_copilot/claude-haiku-4.5",
         messages=[{"role": "user", "content": "Hello"}],
-        optional_params={
-            "context_management": {"edits": [{"type": "clear_tool_uses_20250919"}]}
-        },
+        optional_params={"context_management": {"edits": [{"type": "clear_tool_uses_20250919"}]}},
         litellm_params={},
         api_key=None,
         api_base=None,
     )
 
     assert "context-management-2025-06-27" in headers["anthropic-beta"]
-    if config.should_filter_anthropic_beta_headers():
-        headers = update_headers_with_filtered_beta(headers=dict(headers), provider="github_copilot")
-    assert "context-management-2025-06-27" in headers.get("anthropic-beta", "")
+
+    # The override is load-bearing: had the config opted into the provider-scoped
+    # filter, the handler would have run it and dropped every value, since
+    # github_copilot has no mapping. Prove that here so a regression that flips
+    # should_filter back on is caught as the silent feature breakage it causes.
+    stripped = update_headers_with_filtered_beta(headers=dict(headers), provider="github_copilot")
+    assert "anthropic-beta" not in stripped
 
 
 def test_github_copilot_config_does_not_handle_web_search_natively():