diff --git a/agent/agent_init.py b/agent/agent_init.py
index 6b85f9ef1d..d5798f163f 100644
--- a/agent/agent_init.py
+++ b/agent/agent_init.py
@@ -617,6 +617,9 @@ def init_agent(
             if base_url_host_matches(effective_base, "openrouter.ai"):
                 from agent.auxiliary_client import build_or_headers
                 client_kwargs["default_headers"] = build_or_headers()
+            elif base_url_host_matches(effective_base, "integrate.api.nvidia.com"):
+                from agent.auxiliary_client import build_nvidia_nim_headers
+                client_kwargs["default_headers"] = build_nvidia_nim_headers(effective_base)
             elif base_url_host_matches(effective_base, "api.routermint.com"):
                 client_kwargs["default_headers"] = _ra()._routermint_headers()
             elif base_url_host_matches(effective_base, "api.githubcopilot.com"):
@@ -655,9 +658,15 @@ def init_agent(
                 }
                 if _provider_timeout is not None:
                     client_kwargs["timeout"] = _provider_timeout
-                # Preserve any default_headers the router set
-                if hasattr(_routed_client, '_default_headers') and _routed_client._default_headers:
-                    client_kwargs["default_headers"] = dict(_routed_client._default_headers)
+                # Preserve provider-specific headers the router set.  The
+                # OpenAI SDK stores caller-provided default_headers in
+                # _custom_headers; older/mocked clients may expose
+                # _default_headers instead.
+                _routed_headers = getattr(_routed_client, "_custom_headers", None)
+                if not _routed_headers:
+                    _routed_headers = getattr(_routed_client, "_default_headers", None)
+                if _routed_headers:
+                    client_kwargs["default_headers"] = dict(_routed_headers)
             else:
                 # When the user explicitly chose a non-OpenRouter provider
                 # but no credentials were found, fail fast with a clear
@@ -706,8 +715,11 @@ def init_agent(
                             }
                             if _provider_timeout is not None:
                                 client_kwargs["timeout"] = _provider_timeout
-                            if hasattr(_fb_client, "_default_headers") and _fb_client._default_headers:
-                                client_kwargs["default_headers"] = dict(_fb_client._default_headers)
+                            _fb_headers = getattr(_fb_client, "_custom_headers", None)
+                            if not _fb_headers:
+                                _fb_headers = getattr(_fb_client, "_default_headers", None)
+                            if _fb_headers:
+                                client_kwargs["default_headers"] = dict(_fb_headers)
                             _fb_resolved = True
                             break
                     if not _fb_resolved:
diff --git a/run_agent.py b/run_agent.py
index c976eba969..f4157807e0 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -2644,12 +2644,18 @@ class AIAgent:
         return True
 
     def _apply_client_headers_for_base_url(self, base_url: str) -> None:
-        from agent.auxiliary_client import _AI_GATEWAY_HEADERS, build_or_headers
+        from agent.auxiliary_client import (
+            _AI_GATEWAY_HEADERS,
+            build_nvidia_nim_headers,
+            build_or_headers,
+        )
 
         if base_url_host_matches(base_url, "openrouter.ai"):
             self._client_kwargs["default_headers"] = build_or_headers()
         elif base_url_host_matches(base_url, "ai-gateway.vercel.sh"):
             self._client_kwargs["default_headers"] = dict(_AI_GATEWAY_HEADERS)
+        elif base_url_host_matches(base_url, "integrate.api.nvidia.com"):
+            self._client_kwargs["default_headers"] = build_nvidia_nim_headers(base_url)
         elif base_url_host_matches(base_url, "api.routermint.com"):
             self._client_kwargs["default_headers"] = _routermint_headers()
         elif base_url_host_matches(base_url, "api.githubcopilot.com"):