diff --git a/litellm/integrations/websearch_interception/handler.py b/litellm/integrations/websearch_interception/handler.py
index f29b378fcde..3ab650eb9c9 100644
--- a/litellm/integrations/websearch_interception/handler.py
+++ b/litellm/integrations/websearch_interception/handler.py
@@ -130,19 +130,25 @@ class WebSearchInterceptionLogger(CustomLogger):
         # 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 provider_enum != LlmProviders.GITHUB_COPILOT:
+                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)"
-                )
-                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 a30a8142230..17b72a52b49 100644
--- a/litellm/llms/github_copilot/messages/transformation.py
+++ b/litellm/llms/github_copilot/messages/transformation.py
@@ -35,12 +35,15 @@ class GithubCopilotAnthropicMessagesConfig(AnthropicMessagesConfig):
     ) -> 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 @@ class GithubCopilotAnthropicMessagesConfig(AnthropicMessagesConfig):
         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 @@ class GithubCopilotAnthropicMessagesConfig(AnthropicMessagesConfig):
     ) -> 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 78bd5a8b34d..38e8a6bdfe1 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 @@ import pytest
 
 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",