diff --git a/tests/e2e/online_serving/test_bagel_expansion.py b/tests/e2e/online_serving/test_bagel_expansion.py
new file mode 100644
index 00000000000..75e18ecfa3d
--- /dev/null
+++ b/tests/e2e/online_serving/test_bagel_expansion.py
@@ -0,0 +1,132 @@
+"""
+Comprehensive tests of diffusion features that are available in online serving mode
+and are supported by the following models:
+- ByteDance-Seed/BAGEL-7B-MoT
+Coverage:
+- TeaCache
+- Cache-DiT
+- CFG-Parallel
+- Tensor-Parallel
+
+assert_diffusion_response validates successful generation and the expected
+512x512 resolution.
+"""
+
+import pytest
+
+from tests.conftest import (
+    OmniServer,
+    OmniServerParams,
+    OpenAIClientHandler,
+    dummy_messages_from_mix_data,
+)
+from tests.utils import hardware_marks
+
+PROMPT = "A futuristic city skyline at twilight, cyberpunk style, ultra-detailed, high resolution."
+NEGATIVE_PROMPT = "low quality, blurry, distorted, deformed, watermark"
+
+SINGLE_CARD_FEATURE_MARKS = hardware_marks(res={"cuda": "H100"})
+PARALLEL_FEATURE_MARKS = hardware_marks(res={"cuda": "H100"}, num_cards=2)
+
+
+def _get_diffusion_feature_cases(model: str):
+    """Return L4 diffusion feature cases for Bagel.
+    TeaCache, Cache-DiT, CFG-Parallel, Tensor-Parallel.
+    """
+
+    return [
+        # TeaCache (single-card)
+        pytest.param(
+            OmniServerParams(
+                model=model,
+                server_args=[
+                    "--cache-backend",
+                    "tea_cache",
+                ],
+            ),
+            id="single_card_teacache",
+            marks=SINGLE_CARD_FEATURE_MARKS,
+        ),
+        # Cache-DiT (single-card)
+        pytest.param(
+            OmniServerParams(
+                model=model,
+                server_args=[
+                    "--cache-backend",
+                    "cache_dit",
+                ],
+            ),
+            id="single_card_cache_dit",
+            marks=SINGLE_CARD_FEATURE_MARKS,
+        ),
+        # CFG-Parallel size 2 (2 GPUs, TeaCache backend)
+        pytest.param(
+            OmniServerParams(
+                model=model,
+                server_args=[
+                    "--cache-backend",
+                    "tea_cache",
+                    "--cfg-parallel-size",
+                    "2",
+                ],
+            ),
+            id="parallel_cfg_2",
+            marks=PARALLEL_FEATURE_MARKS,
+        ),
+        # Tensor-Parallel size 2 (2 GPUs, Cache-DiT backend)
+        pytest.param(
+            OmniServerParams(
+                model=model,
+                server_args=[
+                    "--cache-backend",
+                    "cache_dit",
+                    "--tensor-parallel-size",
+                    "2",
+                ],
+            ),
+            id="parallel_tp_2",
+            marks=PARALLEL_FEATURE_MARKS,
+        ),
+    ]
+
+
+@pytest.mark.advanced_model
+@pytest.mark.diffusion
+@pytest.mark.parametrize(
+    "omni_server",
+    _get_diffusion_feature_cases("ByteDance-Seed/BAGEL-7B-MoT"),
+    indirect=True,
+)
+def test_bagel(
+    omni_server: OmniServer,
+    openai_client: OpenAIClientHandler,
+):
+    """L4 diffusion feature coverage for Bagel on H100.
+
+    This test exercises:
+    - TeaCache
+    - Cache-DiT
+    - CFG-Parallel (size=2)
+    - Tensor-Parallel (size=2)
+
+    Validation is delegated to assert_diffusion_response in tests.conftest,
+    which checks output dimensions and basic correctness.
+    """
+
+    messages = dummy_messages_from_mix_data(content_text=PROMPT)
+
+    request_config = {
+        "model": omni_server.model,
+        "messages": messages,
+        "extra_body": {
+            "height": 512,
+            "width": 512,
+            "num_inference_steps": 2,
+            # Enable CFG for models that use classifier-free guidance
+            "negative_prompt": NEGATIVE_PROMPT,
+            "true_cfg_scale": 4.0,
+            "seed": 42,
+        },
+    }
+
+    openai_client.send_diffusion_request(request_config)