fix(anthropic): override SDK User-Agent for third-party endpoints (#24293)

agent/anthropic_adapter.py

@@ -327,6 +327,27 @@ def _get_claude_code_version() -> str:
     return _claude_code_version_cache
 
 
+_HERMES_AGENT_VERSION_FALLBACK = "0.0.0"
+_hermes_agent_version_cache: Optional[str] = None
+
+
+def _get_hermes_agent_version() -> str:
+    """Lazily resolve the installed hermes-agent version for User-Agent headers.
+
+    Used when overriding the Anthropic SDK's default ``Anthropic/Python <ver>``
+    user-agent on third-party endpoints; self-hosted proxies behind Cloudflare
+    bot-detection 403 the SDK fingerprint, but accept any non-SDK UA.
+    """
+    global _hermes_agent_version_cache
+    if _hermes_agent_version_cache is None:
+        try:
+            from hermes_cli import __version__ as _v
+            _hermes_agent_version_cache = str(_v) if _v else _HERMES_AGENT_VERSION_FALLBACK
+        except Exception:
+            _hermes_agent_version_cache = _HERMES_AGENT_VERSION_FALLBACK
+    return _hermes_agent_version_cache
+
+
 def _is_oauth_token(key: str) -> bool:
     """Check if the key is an Anthropic OAuth/setup token.
 
@@ -734,13 +755,20 @@ def build_anthropic_client(
         if common_betas:
             kwargs["default_headers"] = {"anthropic-beta": ",".join(common_betas)}
     elif _is_third_party_anthropic_endpoint(base_url):
-        # Third-party proxies (Microsoft Foundry, AWS Bedrock, etc.) use their
-        # own API keys with x-api-key auth. Skip OAuth detection — their keys
-        # don't follow Anthropic's sk-ant-* prefix convention and would be
-        # misclassified as OAuth tokens.
+        # Third-party proxies (Microsoft Foundry, AWS Bedrock, self-hosted
+        # relays, GLM proxies, etc.) use their own API keys with x-api-key
+        # auth. Skip OAuth detection — their keys don't follow Anthropic's
+        # sk-ant-* prefix convention and would be misclassified as OAuth
+        # tokens.
+        #
+        # Override the SDK's default ``Anthropic/Python <ver>`` user-agent
+        # because Cloudflare-style WAF bot detection on self-hosted proxies
+        # 403s the SDK fingerprint by default. (#24293)
         kwargs["api_key"] = api_key
+        headers = {"User-Agent": f"hermes-agent/{_get_hermes_agent_version()}"}
         if common_betas:
-            kwargs["default_headers"] = {"anthropic-beta": ",".join(common_betas)}
+            headers["anthropic-beta"] = ",".join(common_betas)
+        kwargs["default_headers"] = headers
     elif _is_oauth_token(api_key):
         # OAuth access token / setup-token → Bearer auth + Claude Code identity.
         # Anthropic routes OAuth requests based on user-agent and headers;

tests/agent/test_anthropic_adapter.py

@@ -109,9 +109,40 @@ def test_custom_base_url(self):
             build_anthropic_client("sk-ant-api03-x", base_url="https://custom.api.com")
             kwargs = mock_sdk.Anthropic.call_args[1]
             assert kwargs["base_url"] == "https://custom.api.com"
-            assert kwargs["default_headers"] == {
-                "anthropic-beta": "interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14"
-            }
+            headers = kwargs["default_headers"]
+            assert headers["anthropic-beta"] == (
+                "interleaved-thinking-2025-05-14,fine-grained-tool-streaming-2025-05-14"
+            )
+            # Third-party endpoints override the SDK's default User-Agent so
+            # Cloudflare-style WAF bot detection doesn't 403 the SDK fingerprint.
+            assert headers["User-Agent"].startswith("hermes-agent/")
+
+    def test_third_party_endpoint_overrides_sdk_user_agent(self):
+        """Custom-provider endpoints get a hermes-agent UA instead of the
+        Anthropic SDK's default ``Anthropic/Python <ver>``, which Cloudflare
+        WAF rules block on self-hosted proxies (#24293)."""
+        with patch("agent.anthropic_adapter._anthropic_sdk") as mock_sdk:
+            build_anthropic_client(
+                "proxy-key-xyz",
+                base_url="https://proxy.example.com/v1",
+            )
+            kwargs = mock_sdk.Anthropic.call_args[1]
+            assert kwargs["api_key"] == "proxy-key-xyz"
+            ua = kwargs["default_headers"]["User-Agent"]
+            assert ua.startswith("hermes-agent/"), ua
+            # The Anthropic SDK default fingerprint must NOT leak through.
+            assert "Anthropic/Python" not in ua
+
+    def test_native_anthropic_endpoint_does_not_override_user_agent(self):
+        """Direct anthropic.com requests must NOT carry the third-party UA
+        override — the SDK's default ``Anthropic/Python`` UA is expected by
+        Anthropic's own infrastructure and routing."""
+        with patch("agent.anthropic_adapter._anthropic_sdk") as mock_sdk:
+            build_anthropic_client("sk-ant-api03-direct")
+            kwargs = mock_sdk.Anthropic.call_args[1]
+            headers = kwargs.get("default_headers", {}) or {}
+            assert "User-Agent" not in headers
+            assert "user-agent" not in headers
 
     def test_azure_anthropic_endpoint_keeps_context_1m_beta(self):
         with patch("agent.anthropic_adapter._anthropic_sdk") as mock_sdk: