diff --git a/agent/agent_runtime_helpers.py b/agent/agent_runtime_helpers.py
index 14c7c73321d..bf4d31b4f4d 100644
--- a/agent/agent_runtime_helpers.py
+++ b/agent/agent_runtime_helpers.py
@@ -1953,6 +1953,11 @@ def switch_model(agent, new_model, new_provider, api_key='', base_url='', api_mo
             _sm_timeout = get_provider_request_timeout(agent.provider, agent.model)
             if _sm_timeout is not None:
                 agent._client_kwargs["timeout"] = _sm_timeout
+            # Reapply provider-specific headers (e.g. OpenRouter HTTP-Referer,
+            # X-Title) that were lost when _client_kwargs was rebuilt from
+            # scratch.  Without this, model switches clear attribution headers
+            # and OpenRouter logs show "Unknown" for subsequent requests.
+            agent._apply_client_headers_for_base_url(effective_base)
             agent.client = agent._create_openai_client(
                 dict(agent._client_kwargs),
                 reason="switch_model",