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/entrypoints/pooling/basic/test_encode.py

@@ -0,0 +1,92 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import weakref
+
+import pytest
+
+from vllm import LLM, PoolingParams
+from vllm.distributed import cleanup_dist_env_and_memory
+from vllm.platforms import current_platform
+
+MODEL_NAME = "intfloat/multilingual-e5-small"
+
+PROMPTS = [
+    "Hello, my name is",
+    "The president of the United States is",
+    "The capital of France is",
+    "The future of AI is",
+]
+
+TOKEN_IDS = [
+    # Using ID={0, 1, 2, 3} results in NaN values,
+    # so we add this offset of 1000
+    [1000],
+    [1000, 1001],
+    [1000, 1002, 1001],
+    [1000, 1003, 1001, 1002],
+]
+
+
+@pytest.fixture(scope="module")
+def llm():
+    # ROCm: Use FLEX_ATTENTION backend as it's the only attention backend
+    # that supports encoder-only models on ROCm.
+    attention_config = None
+    if current_platform.is_rocm():
+        attention_config = {"backend": "FLEX_ATTENTION"}
+
+    # pytest caches the fixture so we use weakref.proxy to
+    # enable garbage collection
+    llm = LLM(
+        model=MODEL_NAME,
+        max_num_batched_tokens=32768,
+        tensor_parallel_size=1,
+        gpu_memory_utilization=0.75,
+        enforce_eager=True,
+        seed=0,
+        attention_config=attention_config,
+    )
+
+    yield weakref.proxy(llm)
+
+    del llm
+
+    cleanup_dist_env_and_memory()
+
+
+@pytest.mark.skip_global_cleanup
+def test_multiple_pooling_params(llm: LLM):
+    pooling_params = [
+        PoolingParams(),
+        PoolingParams(),
+        PoolingParams(),
+        PoolingParams(),
+    ]
+
+    # Multiple PoolingParams should be matched with each prompt
+    outputs = llm.encode(PROMPTS, pooling_params=pooling_params, pooling_task="embed")
+    assert len(PROMPTS) == len(outputs)
+
+    # Exception raised, if the size of params does not match the size of prompts
+    with pytest.raises(ValueError):
+        outputs = llm.encode(
+            PROMPTS, pooling_params=pooling_params[:3], pooling_task="embed"
+        )
+
+    # Single PoolingParams should be applied to every prompt
+    single_pooling_params = PoolingParams()
+    outputs = llm.encode(
+        PROMPTS, pooling_params=single_pooling_params, pooling_task="embed"
+    )
+    assert len(PROMPTS) == len(outputs)
+
+    # pooling_params is None, default params should be applied
+    outputs = llm.encode(PROMPTS, pooling_params=None, pooling_task="embed")
+    assert len(PROMPTS) == len(outputs)
+
+
+def test_right_side_truncation(llm: LLM):
+    # Embeddings models should truncate the end of the prompt
+    tokenizer = llm.get_tokenizer()
+    assert tokenizer.truncation_side == "right"