fix: strip 'openrouter/' prefix from model names (#24234)

Remove early return in get_llm_provider_logic.py that prevented
the 'openrouter/' prefix from being stripped. The early return was
intended for 'native OpenRouter models' like 'openrouter/free',
but no such models exist in the model registry — all OpenRouter
models are multi-segment (e.g. 'openrouter/anthropic/claude-3.5-sonnet')
and need the prefix stripped before being sent to the OpenRouter API.

This regression was introduced in v1.82.3 and caused 400 Bad Request
errors for all OpenRouter models.

litellm/litellm_core_utils/get_llm_provider_logic.py

@@ -158,14 +158,6 @@ def get_llm_provider(  # noqa: PLR0915
         ):  # handle scenario where model="azure/*" and custom_llm_provider="azure"
             model = custom_llm_provider + "/" + model
 
-        # Native OpenRouter models have IDs like "openrouter/free" where the
-        # "openrouter/" prefix is part of the actual model name on the API.
-        # When called from a bridge (e.g. anthropic_messages adapter),
-        # custom_llm_provider is already resolved, so return early to prevent
-        # the provider-list stripping below from removing the prefix.
-        if custom_llm_provider == "openrouter" and model.startswith("openrouter/"):
-            return model, custom_llm_provider, dynamic_api_key, api_base
-
         if api_key and api_key.startswith("os.environ/"):
             dynamic_api_key = get_secret_str(api_key)
 

tests/local_testing/test_get_llm_provider.py

@@ -420,3 +420,19 @@ def test_get_llm_provider_use_proxy_arg_true_with_direct_args():
     assert provider == "litellm_proxy"
     assert key == arg_api_key  # Should use the argument key
     assert base == arg_api_base # Should use the argument base
+
+
+def test_openrouter_model_prefix_stripped():
+    """
+    GH#24234: OpenRouter models like "openrouter/anthropic/claude-3.5-sonnet"
+    should have the "openrouter/" prefix stripped before being sent to the API.
+    The API expects "anthropic/claude-3.5-sonnet", not the full prefixed name.
+    """
+    model, provider, _, _ = litellm.get_llm_provider(
+        model="openrouter/anthropic/claude-3.5-sonnet"
+    )
+    assert provider == "openrouter"
+    assert model == "anthropic/claude-3.5-sonnet", (
+        f"Expected 'anthropic/claude-3.5-sonnet' but got '{model}'. "
+        "The 'openrouter/' prefix was not stripped."
+    )