diff --git a/libs/partners/openrouter/langchain_openrouter/chat_models.py b/libs/partners/openrouter/langchain_openrouter/chat_models.py
index 5ea9943786d..a31c4386940 100644
--- a/libs/partners/openrouter/langchain_openrouter/chat_models.py
+++ b/libs/partners/openrouter/langchain_openrouter/chat_models.py
@@ -152,14 +152,27 @@ class ChatOpenRouter(BaseChatModel):
     """OpenRouter API base URL. Maps to SDK `server_url`."""
 
     app_url: str | None = Field(
-        default_factory=from_env("OPENROUTER_APP_URL", default=None),
+        default_factory=from_env(
+            "OPENROUTER_APP_URL",
+            default="https://docs.langchain.com/oss",
+        ),
     )
-    """Application URL for OpenRouter attribution. Maps to `HTTP-Referer` header."""
+    """Application URL for OpenRouter attribution.
+
+    Maps to `HTTP-Referer` header.
+
+    See https://openrouter.ai/docs/app-attribution for details.
+    """
 
     app_title: str | None = Field(
-        default_factory=from_env("OPENROUTER_APP_TITLE", default=None),
+        default_factory=from_env("OPENROUTER_APP_TITLE", default="langchain"),
     )
-    """Application title for OpenRouter attribution. Maps to `X-Title` header."""
+    """Application title for OpenRouter attribution.
+
+    Maps to `X-Title` header.
+
+    See https://openrouter.ai/docs/app-attribution for details.
+    """
 
     request_timeout: int | None = Field(default=None, alias="timeout")
     """Timeout for requests in milliseconds. Maps to SDK `timeout_ms`."""
diff --git a/libs/partners/openrouter/tests/unit_tests/__snapshots__/test_standard.ambr b/libs/partners/openrouter/tests/unit_tests/__snapshots__/test_standard.ambr
index 2e4d376538a..f0574a19267 100644
--- a/libs/partners/openrouter/tests/unit_tests/__snapshots__/test_standard.ambr
+++ b/libs/partners/openrouter/tests/unit_tests/__snapshots__/test_standard.ambr
@@ -7,6 +7,8 @@
       'ChatOpenRouter',
     ]),
     'kwargs': dict({
+      'app_title': 'langchain',
+      'app_url': 'https://docs.langchain.com/oss',
       'max_retries': 2,
       'max_tokens': 100,
       'model_name': 'openai/gpt-4o-mini',
diff --git a/libs/partners/openrouter/tests/unit_tests/test_chat_models.py b/libs/partners/openrouter/tests/unit_tests/test_chat_models.py
index e35bcf9f2dc..2e41c43c3e0 100644
--- a/libs/partners/openrouter/tests/unit_tests/test_chat_models.py
+++ b/libs/partners/openrouter/tests/unit_tests/test_chat_models.py
@@ -310,6 +310,32 @@ class TestChatOpenRouterInstantiation:
             call_kwargs = mock_cls.call_args[1]
             assert call_kwargs["x_title"] == "My App"
 
+    def test_default_attribution_headers(self) -> None:
+        """Test that default attribution headers are sent when not overridden."""
+        with patch("openrouter.OpenRouter") as mock_cls:
+            mock_cls.return_value = MagicMock()
+            ChatOpenRouter(
+                model=MODEL_NAME,
+                api_key=SecretStr("test-key"),
+            )
+            call_kwargs = mock_cls.call_args[1]
+            assert call_kwargs["http_referer"] == ("https://docs.langchain.com/oss")
+            assert call_kwargs["x_title"] == "langchain"
+
+    def test_user_attribution_overrides_defaults(self) -> None:
+        """Test that user-supplied attribution overrides the defaults."""
+        with patch("openrouter.OpenRouter") as mock_cls:
+            mock_cls.return_value = MagicMock()
+            ChatOpenRouter(
+                model=MODEL_NAME,
+                api_key=SecretStr("test-key"),
+                app_url="https://my-custom-app.com",
+                app_title="My Custom App",
+            )
+            call_kwargs = mock_cls.call_args[1]
+            assert call_kwargs["http_referer"] == "https://my-custom-app.com"
+            assert call_kwargs["x_title"] == "My Custom App"
+
     def test_reasoning_in_params(self) -> None:
         """Test that `reasoning` is included in default params."""
         model = _make_model(reasoning={"effort": "high"})
diff --git a/libs/partners/openrouter/uv.lock b/libs/partners/openrouter/uv.lock
index ce01861a456..85487c9ef5b 100644
--- a/libs/partners/openrouter/uv.lock
+++ b/libs/partners/openrouter/uv.lock
@@ -318,7 +318,7 @@ wheels = [
 
 [[package]]
 name = "langchain-core"
-version = "1.2.13"
+version = "1.2.15"
 source = { editable = "../../core" }
 dependencies = [
     { name = "jsonpatch" },