diff --git a/mini_swe_runner.py b/mini_swe_runner.py
index 2f98249f2..9be7b7348 100644
--- a/mini_swe_runner.py
+++ b/mini_swe_runner.py
@@ -200,13 +200,7 @@ class MiniSWERunner:
         else:
             client_kwargs["base_url"] = "https://openrouter.ai/api/v1"
 
-        if base_url and "api.anthropic.com" in base_url.strip().lower():
-            raise ValueError(
-                "Anthropic's native /v1/messages API is not supported yet (planned for a future release). "
-                "Hermes currently requires OpenAI-compatible /chat/completions endpoints. "
-                "To use Claude models now, route through OpenRouter (OPENROUTER_API_KEY) "
-                "or any OpenAI-compatible proxy that wraps the Anthropic API."
-            )
+
         
         # Handle API key - OpenRouter is the primary provider
         if api_key:
diff --git a/run_agent.py b/run_agent.py
index 89e1ad00e..75e3dfc95 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -253,13 +253,7 @@ class AIAgent:
             self.provider = "openai-codex"
         else:
             self.api_mode = "chat_completions"
-        if base_url and "api.anthropic.com" in base_url.strip().lower():
-            raise ValueError(
-                "Anthropic's native /v1/messages API is not supported yet (planned for a future release). "
-                "Hermes currently requires OpenAI-compatible /chat/completions endpoints. "
-                "To use Claude models now, route through OpenRouter (OPENROUTER_API_KEY) "
-                "or any OpenAI-compatible proxy that wraps the Anthropic API."
-            )
+
         self.tool_progress_callback = tool_progress_callback
         self.clarify_callback = clarify_callback
         self.step_callback = step_callback
diff --git a/tests/test_run_agent.py b/tests/test_run_agent.py
index 226b29a6d..55f96f942 100644
--- a/tests/test_run_agent.py
+++ b/tests/test_run_agent.py
@@ -280,22 +280,21 @@ class TestMaskApiKey:
 
 
 class TestInit:
-    def test_anthropic_base_url_fails_fast(self):
-        """Anthropic native endpoints should error before building an OpenAI client."""
+    def test_anthropic_base_url_accepted(self):
+        """Anthropic base URLs should be accepted (OpenAI-compatible endpoint)."""
         with (
             patch("run_agent.get_tool_definitions", return_value=[]),
             patch("run_agent.check_toolset_requirements", return_value={}),
             patch("run_agent.OpenAI") as mock_openai,
         ):
-            with pytest.raises(ValueError, match="not supported yet"):
-                AIAgent(
-                    api_key="test-key-1234567890",
-                    base_url="https://api.anthropic.com/v1/messages",
-                    quiet_mode=True,
-                    skip_context_files=True,
-                    skip_memory=True,
-                )
-            mock_openai.assert_not_called()
+            AIAgent(
+                api_key="test-key-1234567890",
+                base_url="https://api.anthropic.com/v1/",
+                quiet_mode=True,
+                skip_context_files=True,
+                skip_memory=True,
+            )
+            mock_openai.assert_called_once()
 
     def test_prompt_caching_claude_openrouter(self):
         """Claude model via OpenRouter should enable prompt caching."""