diff --git a/tests/entrypoints/openai/realtime/test_realtime_validation.py b/tests/entrypoints/openai/realtime/test_realtime_validation.py
index 672894d0c..bb6b02f5c 100644
--- a/tests/entrypoints/openai/realtime/test_realtime_validation.py
+++ b/tests/entrypoints/openai/realtime/test_realtime_validation.py
@@ -15,6 +15,13 @@ from tests.entrypoints.openai.conftest import add_attention_backend
 from tests.utils import ROCM_ENV_OVERRIDES, ROCM_EXTRA_ARGS, RemoteOpenAIServer
 from vllm.assets.audio import AudioAsset
 
+# Increase engine iteration timeout for ROCm where first-use JIT compilation
+# can exceed the default 60s, causing a silent deadlock in feed_tokens.
+REALTIME_ENV_OVERRIDES = {
+    **ROCM_ENV_OVERRIDES,
+    "VLLM_ENGINE_ITERATION_TIMEOUT_S": "600",
+}
+
 MISTRAL_FORMAT_ARGS = [
     "--tokenizer_mode",
     "mistral",
@@ -77,7 +84,7 @@ async def test_multi_chunk_streaming(
     add_attention_backend(server_args, rocm_aiter_fa_attention)
 
     with RemoteOpenAIServer(
-        model_name, server_args, env_dict=ROCM_ENV_OVERRIDES
+        model_name, server_args, env_dict=REALTIME_ENV_OVERRIDES
     ) as remote_server:
         ws_url = _get_websocket_url(remote_server)
         async with websockets.connect(ws_url) as ws:
@@ -180,7 +187,7 @@ async def test_empty_commit_does_not_crash_engine(
     add_attention_backend(server_args, rocm_aiter_fa_attention)
 
     with RemoteOpenAIServer(
-        model_name, server_args, env_dict=ROCM_ENV_OVERRIDES
+        model_name, server_args, env_dict=REALTIME_ENV_OVERRIDES
     ) as remote_server:
         ws_url = _get_websocket_url(remote_server)
 
@@ -257,3 +264,68 @@ async def test_empty_commit_does_not_crash_engine(
                 elif event["type"] == "error":
                     pytest.fail(f"Engine error after empty commit: {event}")
             assert done_received
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+async def test_session_update_invalid_model_returns_error(
+    model_name, rocm_aiter_fa_attention
+):
+    """Test that session.update with an invalid model returns an error."""
+    server_args = ["--enforce-eager", "--max-model-len", "2048"]
+
+    if model_name.startswith("mistralai"):
+        server_args += MISTRAL_FORMAT_ARGS
+
+    add_attention_backend(server_args, rocm_aiter_fa_attention)
+
+    with RemoteOpenAIServer(
+        model_name, server_args, env_dict=REALTIME_ENV_OVERRIDES
+    ) as remote_server:
+        ws_url = _get_websocket_url(remote_server)
+        async with websockets.connect(ws_url) as ws:
+            event = await receive_event(ws, timeout=30.0)
+            assert event["type"] == "session.created"
+
+            # Send session.update with a model that doesn't exist
+            await send_event(
+                ws,
+                {"type": "session.update", "model": "nonexistent-model"},
+            )
+
+            event = await receive_event(ws, timeout=10.0)
+            assert event["type"] == "error"
+            assert "nonexistent-model" in event["error"]
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("model_name", [MODEL_NAME])
+async def test_commit_without_session_update_returns_error(
+    model_name, rocm_aiter_fa_attention
+):
+    """Test that committing before validating the model returns an error
+    and does not fall through to processing."""
+    server_args = ["--enforce-eager", "--max-model-len", "2048"]
+
+    if model_name.startswith("mistralai"):
+        server_args += MISTRAL_FORMAT_ARGS
+
+    add_attention_backend(server_args, rocm_aiter_fa_attention)
+
+    with RemoteOpenAIServer(
+        model_name, server_args, env_dict=REALTIME_ENV_OVERRIDES
+    ) as remote_server:
+        ws_url = _get_websocket_url(remote_server)
+        async with websockets.connect(ws_url) as ws:
+            event = await receive_event(ws, timeout=30.0)
+            assert event["type"] == "session.created"
+
+            # Send commit without sending session.update first
+            await send_event(
+                ws,
+                {"type": "input_audio_buffer.commit", "final": True},
+            )
+
+            event = await receive_event(ws, timeout=10.0)
+            assert event["type"] == "error"
+            assert "model_not_validated" in event.get("code", "")
diff --git a/vllm/entrypoints/openai/realtime/connection.py b/vllm/entrypoints/openai/realtime/connection.py
index c958004bb..58af32905 100644
--- a/vllm/entrypoints/openai/realtime/connection.py
+++ b/vllm/entrypoints/openai/realtime/connection.py
@@ -102,7 +102,14 @@ class RealtimeConnection:
         event_type = event.get("type")
         if event_type == "session.update":
             logger.debug("Session updated: %s", event)
-            self._check_model(event["model"])
+            model = event.get("model")
+            if model is None:
+                await self.send_error("Missing required field: model", "invalid_event")
+                return
+            err = self._check_model(model)
+            if err is not None:
+                await self.send_error(err.error.message, "model_not_found")
+                return
             self._is_model_validated = True
         elif event_type == "input_audio_buffer.append":
             append_event = InputAudioBufferAppend(**event)
@@ -140,6 +147,7 @@ class RealtimeConnection:
                     err_msg,
                     "model_not_validated",
                 )
+                return
 
             commit_event = InputAudioBufferCommit(**event)
             # final signals that the audio is finished