diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 50722fa..8a826cd 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -14,6 +14,7 @@ jobs:
     strategy:
       matrix:
         python-version: ["3.11"]
+        ray-version: ["latest", "2.55.0"]
     timeout-minutes: 10
     steps:
       - name: Config mirrors
@@ -25,36 +26,43 @@ jobs:
 
       - name: Checkout code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
-      - name: Build Python ${{ matrix.python-version }} wheel
+      - name: Build Python ${{ matrix.python-version }} wheel (Ray ${{ matrix.ray-version }})
         run: |
           echo "Building for Python ${{ matrix.python-version }}..."
           pip${{ matrix.python-version }} install build
           pip${{ matrix.python-version }} install -r requirements.txt
           python${{ matrix.python-version }} -m build --wheel
           pip${{ matrix.python-version }} install "$(ls dist/*.whl)[test,yr]" --force-reinstall
+          if [ "${{ matrix.ray-version }}" != "latest" ]; then
+            pip${{ matrix.python-version }} install "ray[default]==${{ matrix.ray-version }}" --force-reinstall
+          fi
       - name: Run tests for Python ${{ matrix.python-version }}
         run: |
           echo "Running tests for Python ${{ matrix.python-version }}..."
           python${{ matrix.python-version }} -m pytest -v tests/
       - name: Install etcd
+        if: matrix.ray-version == 'latest'
         run: |
           apt-get update && apt-get install -y curl
           curl -s -L https://mirrors.huaweicloud.com/etcd/v3.6.5/etcd-v3.6.5-linux-arm64.tar.gz -o etcd-v3.6.5-linux-arm64.tar.gz
           tar -xzf etcd-v3.6.5-linux-arm64.tar.gz
           mv etcd-v3.6.5-linux-arm64/etcd /usr/local/bin/
       - name: Install openyuanrong-datasystem
+        if: matrix.ray-version == 'latest'
         run: |
           pip${{ matrix.python-version }} install "openyuanrong-datasystem>=0.8.0"
       - name: Run performance test (etcd mode)
+        if: matrix.ray-version == 'latest'
         run: |
           echo "start ray cluster"
           ray start --head
           echo "Running direct_transport_perftest.py (etcd mode)"
-          python${{ matrix.python-version }} tests/benchmarks/direct_transport_perftest.py --backend=yr --placement=local --device=npu --init-mode=etcd
+          python${{ matrix.python-version }} tests/benchmarks/direct_transport_perftest.py --backend=yr --placement=local --device=cpu --init-mode=etcd
           echo "stop ray cluster"
           ray stop
 
       - name: Run performance test (metastore mode)
+        if: matrix.ray-version == 'latest'
         run: |
           echo "start ray cluster"
           ray start --head
diff --git a/ray_ascend/__init__.py b/ray_ascend/__init__.py
index 2bb2603..0309265 100644
--- a/ray_ascend/__init__.py
+++ b/ray_ascend/__init__.py
@@ -157,10 +157,11 @@ def __init__(self):
             def transfer_npu_tensor_via_hccs(self):
                 return torch.tensor([1, 2, 3]).npu()
     """
+    register_hccl_collective_backend()
+
     import torch
     from ray.experimental import register_tensor_transport
 
     from .direct_transport.hccl_tensor_transport import HCCLTensorTransport
 
-    register_hccl_collective_backend()
     register_tensor_transport("HCCL", ["npu"], HCCLTensorTransport, torch.Tensor)
diff --git a/tests/test_backward_compat.py b/tests/test_backward_compat.py
new file mode 100644
index 0000000..16bfc15
--- /dev/null
+++ b/tests/test_backward_compat.py
@@ -0,0 +1,35 @@
+"""Verify backward compatibility of registration functions on Ray < 2.56.
+
+These tests use mock to simulate the absence of
+`ray.util.collective.backend_registry` (which was introduced in Ray 2.56),
+ensuring that both registration functions raise RuntimeError with a clear
+upgrade message instead of failing silently or crashing.
+"""
+
+from unittest.mock import patch
+
+import pytest
+
+from ray_ascend import register_hccl_collective_backend, register_hccl_tensor_transport
+
+
+class TestBackwardCompatibility:
+    """Verify registration functions raise RuntimeError on Ray < 2.56."""
+
+    @patch.dict("sys.modules", {"ray.util.collective.backend_registry": None})
+    def test_register_hccl_collective_backend_raises_on_old_ray(self):
+        """register_hccl_collective_backend should raise RuntimeError when
+        backend_registry module is unavailable (Ray < 2.56)."""
+        with pytest.raises(RuntimeError, match="requires Ray >= 2.56"):
+            register_hccl_collective_backend()
+
+    @patch.dict("sys.modules", {"ray.util.collective.backend_registry": None})
+    def test_register_hccl_tensor_transport_raises_on_old_ray(self):
+        """register_hccl_tensor_transport should raise RuntimeError when
+        backend_registry module is unavailable (Ray < 2.56).
+
+        It calls register_hccl_collective_backend first, so it inherits
+        the same RuntimeError behavior.
+        """
+        with pytest.raises(RuntimeError, match="requires Ray >= 2.56"):
+            register_hccl_tensor_transport()