diff --git a/.github/run-eval/resolve_model_config.py b/.github/run-eval/resolve_model_config.py
index 00b4ed9358..c21ecc8888 100755
--- a/.github/run-eval/resolve_model_config.py
+++ b/.github/run-eval/resolve_model_config.py
@@ -127,6 +127,11 @@
         "display_name": "GPT-5.2 Codex",
         "llm_config": {"model": "litellm_proxy/gpt-5.2-codex"},
     },
+    "gpt-5-3-codex": {
+        "id": "gpt-5-3-codex",
+        "display_name": "GPT-5.3 Codex",
+        "llm_config": {"model": "litellm_proxy/gpt-5-3-codex"},
+    },
     "gpt-5.2-high-reasoning": {
         "id": "gpt-5.2-high-reasoning",
         "display_name": "GPT-5.2 High Reasoning",
@@ -339,6 +344,10 @@ def check_model(
         return False, f"✗ {display_name}: {type(e).__name__} - {e}"
 
 
+# Alias for backward compatibility with tests
+test_model = check_model
+
+
 def run_preflight_check(models: list[dict[str, Any]]) -> bool:
     """Run preflight LLM check for all models.
 
diff --git a/tests/github_workflows/test_resolve_model_config.py b/tests/github_workflows/test_resolve_model_config.py
index 297cf4dd03..2ed496df68 100644
--- a/tests/github_workflows/test_resolve_model_config.py
+++ b/tests/github_workflows/test_resolve_model_config.py
@@ -249,6 +249,15 @@ def test_gpt_oss_20b_config():
     assert model["llm_config"]["model"] == "litellm_proxy/gpt-oss-20b"
 
 
+def test_gpt_5_3_codex_config():
+    """Test that gpt-5-3-codex has correct configuration."""
+    model = MODELS["gpt-5-3-codex"]
+
+    assert model["id"] == "gpt-5-3-codex"
+    assert model["display_name"] == "GPT-5.3 Codex"
+    assert model["llm_config"]["model"] == "litellm_proxy/gpt-5-3-codex"
+
+
 def test_glm_5_config():
     """Test that glm-5 has correct configuration."""
     model = MODELS["glm-5"]