Add vLLM v0.18.1 source tree with KV transfer abort fix

third_party/vllm/ now tracked in git for direct patch management.
Based on vLLM v0.18.1 release with one patch applied:

  vllm/v1/core/sched/scheduler.py:
    Replace fatal assert with graceful skip when KV transfer callback
    arrives for an already-aborted request during PD disaggregated serving.

Future vLLM modifications should be made directly in third_party/vllm/
and committed normally. The patches/ directory is kept as documentation
of what changed from upstream.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

third_party/vllm/tests/compile/test_rotary_embedding_compile.py

@@ -0,0 +1,68 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import pytest
+import torch
+
+import vllm.envs as envs
+from vllm.compilation.decorators import support_torch_compile
+from vllm.config import (
+    CompilationConfig,
+    ModelConfig,
+    VllmConfig,
+    set_current_vllm_config,
+)
+from vllm.config.compilation import CompilationMode, CUDAGraphMode
+from vllm.model_executor.layers.rotary_embedding import get_rope
+from vllm.platforms import current_platform
+
+
+@support_torch_compile
+class RotaryEmbeddingCompileModule(torch.nn.Module):
+    def __init__(self, *, vllm_config: VllmConfig, prefix: str = "") -> None:
+        super().__init__()
+        self.rotary_emb = get_rope(
+            head_size=32,
+            max_position=128,
+            dtype=torch.float32,
+            rope_parameters={"rope_type": "default", "rope_theta": 10000},
+            is_neox_style=True,
+        )
+
+    def forward(
+        self, positions: torch.Tensor, query: torch.Tensor, key: torch.Tensor
+    ) -> torch.Tensor:
+        q_rot, k_rot = self.rotary_emb(positions, query, key)
+        return q_rot + k_rot
+
+
+@pytest.mark.skipif(current_platform.is_cpu(), reason="Requires GPU for torch.compile")
+def test_rotary_embedding_torch_compile_with_custom_op(monkeypatch):
+    # Ensure env toggles take effect for this test only.
+    # The bytecode hook is required to detect buffer mutation in compiled code,
+    # and AOT compile bypasses that hook entirely.
+    envs.disable_envs_cache()
+    monkeypatch.setenv("VLLM_USE_BYTECODE_HOOK", "1")
+    monkeypatch.setenv("VLLM_USE_AOT_COMPILE", "0")
+
+    device = "cuda"
+    positions = torch.arange(16, device=device)
+    query = torch.randn(16, 32, device=device, dtype=torch.bfloat16)
+    key = torch.randn(16, 32, device=device, dtype=torch.bfloat16)
+
+    vllm_config = VllmConfig(
+        model_config=ModelConfig(dtype=torch.bfloat16),
+        compilation_config=CompilationConfig(
+            mode=CompilationMode.VLLM_COMPILE,
+            backend="inductor",
+            custom_ops=["+rotary_embedding"],
+            cudagraph_mode=CUDAGraphMode.NONE,
+            cudagraph_num_of_warmups=0,
+        ),
+    )
+
+    with set_current_vllm_config(vllm_config):
+        model = RotaryEmbeddingCompileModule(vllm_config=vllm_config)
+        model(positions, query, key)
+        assert model._compiled_bytecode is not None
+        assert "update" not in model._compiled_bytecode.co_names