fix(websearch): keep the provider prefix on the responses follow-up model too

The responses patch builder still used the old "a slash means already qualified" test, so
a provider-stripped sub-path model reached the follow-up unqualified on that surface. It
now resolves the model the same way the chat completion builder does.

litellm/integrations/websearch_interception/handler.py

@@ -36,6 +36,7 @@ from litellm.integrations.websearch_interception.transformation import (
 from litellm.litellm_core_utils.agentic_loop_settings import (
     validated_max_agentic_loops,
 )
+from litellm.litellm_core_utils.core_helpers import qualify_provider_stripped_model
 from litellm.llms.base_llm.search.transformation import SearchResponse
 from litellm.types.integrations.custom_logger import (
     CHAT_COMPLETION_AGENTIC_SURFACE,
@@ -1242,9 +1243,10 @@ class WebSearchInterceptionLogger(CustomLogger):
             }
         }
 
-        full_model_name = model
-        if "/" not in model and isinstance(kwargs.get("custom_llm_provider"), str):
-            full_model_name = f"{kwargs['custom_llm_provider']}/{model}"
+        custom_llm_provider: Final = kwargs.get("custom_llm_provider")
+        full_model_name: Final = qualify_provider_stripped_model(
+            model, custom_llm_provider if isinstance(custom_llm_provider, str) else ""
+        )
 
         verbose_logger.debug(
             "WebSearchInterception: Built responses request patch model=%s input_items=%d searches=%d",
@@ -1910,8 +1912,6 @@ class WebSearchInterceptionLogger(CustomLogger):
             k: v for k, v in kwargs.items() if not k.startswith("_websearch_interception") and k not in internal_params
         }
 
-        from litellm.litellm_core_utils.core_helpers import qualify_provider_stripped_model
-
         full_model_name: Final = qualify_provider_stripped_model(model, kwargs.get("custom_llm_provider", ""))
 
         verbose_logger.debug(

tests/unit/integrations/websearch_interception/test_websearch_responses.py

@@ -252,6 +252,52 @@ async def test_build_responses_plan_produces_responses_input():
     assert patch_obj.model == "openai/gpt-4o"
 
 
+@pytest.mark.asyncio
+async def test_build_responses_plan_keeps_the_provider_on_a_sub_path_model():
+    """#38829 on the Responses surface: a provider-stripped model whose remainder still holds a
+    slash was left unqualified, so the follow-up could not resolve a provider."""
+    logger = WebSearchInterceptionLogger(enabled_providers=[LlmProviders.BEDROCK])
+
+    tools_dict = {
+        "tool_calls": [
+            {
+                "id": "fc_1",
+                "call_id": "fc_1",
+                "type": "function_call",
+                "name": "litellm_web_search",
+                "arguments": '{"query": "latest ai news"}',
+                "input": {"query": "latest ai news"},
+            }
+        ],
+        "tool_type": "websearch",
+        "provider": "bedrock",
+        "response_format": "responses",
+    }
+
+    with patch.object(
+        logger,
+        "_execute_search",
+        new=AsyncMock(return_value=("a search result", None)),
+    ):
+        plan = await logger.async_build_responses_agentic_loop_plan(
+            tools=tools_dict,
+            model="mantle/anthropic.claude-sonnet-5",
+            messages=[{"role": "user", "content": "What's the latest AI news?"}],
+            response=_responses_output_with_web_search(),
+            optional_params={"tools": [{"type": "function", "name": "litellm_web_search"}]},
+            logging_obj=MagicMock(),
+            stream=False,
+            kwargs={
+                "custom_llm_provider": "bedrock",
+                "_agentic_loop_api_surface": RESPONSES_AGENTIC_SURFACE,
+            },
+        )
+
+    patch_obj = plan.request_patch
+    assert patch_obj is not None
+    assert patch_obj.model == "bedrock/mantle/anthropic.claude-sonnet-5"
+
+
 @pytest.mark.asyncio
 async def test_deployment_hook_converts_native_responses_web_search_tool():
     """async_pre_call_deployment_hook converts a native Responses web_search tool