diff --git a/libs/partners/openrouter/langchain_openrouter/data/_profiles.py b/libs/partners/openrouter/langchain_openrouter/data/_profiles.py
index f1fc7636dc3..1778e52d6dc 100644
--- a/libs/partners/openrouter/langchain_openrouter/data/_profiles.py
+++ b/libs/partners/openrouter/langchain_openrouter/data/_profiles.py
@@ -1462,6 +1462,26 @@ _PROFILES: dict[str, dict[str, Any]] = {
         "attachment": True,
         "temperature": True,
     },
+    "mistralai/mistral-small-2603": {
+        "name": "Mistral Small 4",
+        "release_date": "2026-03-16",
+        "last_updated": "2026-03-16",
+        "open_weights": True,
+        "max_input_tokens": 262144,
+        "max_output_tokens": 262144,
+        "text_inputs": True,
+        "image_inputs": True,
+        "audio_inputs": False,
+        "video_inputs": False,
+        "text_outputs": True,
+        "image_outputs": False,
+        "audio_outputs": False,
+        "video_outputs": False,
+        "reasoning_output": True,
+        "tool_calling": True,
+        "attachment": True,
+        "temperature": True,
+    },
     "mistralai/mistral-small-3.1-24b-instruct": {
         "name": "Mistral Small 3.1 24B Instruct",
         "release_date": "2025-03-17",