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/benchmarks/run_structured_output_benchmark.sh

@@ -0,0 +1,131 @@
+#!/bin/bash
+
+# default values
+MODEL=${MODEL:-"Qwen/Qwen2.5-7B-Instruct"}
+BACKEND=${BACKEND:-"vllm"}
+DATASET=${DATASET:-"xgrammar_bench"}
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+OUTPUT_DIR=${OUTPUT_DIR:-"$SCRIPT_DIR/structured_output_benchmark_results"}
+PORT=${PORT:-8000}
+STRUCTURED_OUTPUT_RATIO=${STRUCTURED_OUTPUT_RATIO:-1}
+TOTAL_SECONDS=${TOTAL_SECONDS:-90}
+MAX_NEW_TOKENS=${MAX_NEW_TOKENS:-300}
+TOKENIZER_MODE=${TOKENIZER_MODE:-"auto"}
+
+usage() {
+    echo "Usage: $0 [options]"
+    echo "Options:"
+    echo "  --model MODEL                  Model to benchmark (default: $MODEL)"
+    echo "  --backend BACKEND              Backend to use (default: $BACKEND)" 
+    echo "  --dataset DATASET              Dataset to use (default: $DATASET)"
+    echo "  --max-new-tokens N             Maximum number of tokens to generate (default: $MAX_NEW_TOKENS)"
+    echo "  --output-dir DIR               Output directory for results (default: $OUTPUT_DIR)"
+    echo "  --port PORT                    Port to use (default: $PORT)"
+    echo "  --structured-output-ratio N    Ratio of structured outputs (default: $STRUCTURED_OUTPUT_RATIO)"
+    echo "  --tokenizer-mode MODE          Tokenizer mode to use (default: $TOKENIZER_MODE)"
+    echo "  --total-seconds N              Total seconds to run the benchmark (default: $TOTAL_SECONDS)"
+    echo "  -h, --help                     Show this help message and exit"
+    exit 0
+}
+
+# parse command line arguments
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --model)
+      MODEL="$2"
+      shift 2
+      ;;
+    --backend)
+      BACKEND="$2"
+      shift 2
+      ;;
+    --dataset)
+      DATASET="$2"
+      shift 2
+      ;;
+    --max-new-tokens)
+      MAX_NEW_TOKENS="$2"
+      shift 2
+      ;;
+    --output-dir)
+      OUTPUT_DIR="$2"
+      shift 2
+      ;;
+    --port)
+      PORT="$2"
+      shift 2
+      ;;
+    --structured-output-ratio)
+      STRUCTURED_OUTPUT_RATIO="$2"
+      shift 2
+      ;;
+    --tokenizer-mode)
+      TOKENIZER_MODE="$2"
+      shift 2
+      ;;
+    --total-seconds)
+      TOTAL_SECONDS="$2"
+      shift 2
+      ;;
+    -h|--help)
+      usage
+      ;;
+    *)
+      printf "Unknown argument: %s\n" "$1"
+      usage
+      ;;
+  esac
+done
+
+# Create output directory if it doesn't exist
+mkdir -p "$OUTPUT_DIR"
+
+# Define QPS values to test
+QPS_VALUES=(25 20 15 10 5 1)
+
+# Common parameters
+COMMON_PARAMS=(
+  --backend "$BACKEND"
+  --model "$MODEL"
+  --dataset "$DATASET"
+  --structured-output-ratio "$STRUCTURED_OUTPUT_RATIO"
+  --save-results
+  --result-dir "$OUTPUT_DIR"
+  --output-len "$MAX_NEW_TOKENS"
+  --port "$PORT"
+  --tokenizer-mode "$TOKENIZER_MODE"
+)
+
+echo "Starting structured output benchmark with model: $MODEL"
+echo "Backend: $BACKEND"
+echo "Dataset: $DATASET"
+echo "Results will be saved to: $OUTPUT_DIR"
+echo "----------------------------------------"
+
+# Run benchmarks with different QPS values
+for qps in "${QPS_VALUES[@]}"; do
+  echo "Running benchmark with QPS: $qps"
+
+  # Get git hash and branch for the filename
+  GIT_HASH=$(git rev-parse --short HEAD 2>/dev/null || echo "unknown")
+  GIT_BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null || echo "unknown")
+
+  # Construct filename for this run
+  FILENAME="${BACKEND}_${qps}qps_$(basename "$MODEL")_${DATASET}_${GIT_HASH}_${GIT_BRANCH}.json"
+
+  NUM_PROMPTS=$(echo "$TOTAL_SECONDS * $qps" | bc)
+  NUM_PROMPTS=${NUM_PROMPTS%.*}  # Remove fractional part
+  echo "Running benchmark with $NUM_PROMPTS prompts"
+
+  # Run the benchmark
+  python "$SCRIPT_DIR/benchmark_serving_structured_output.py" "${COMMON_PARAMS[@]}" \
+    --request-rate "$qps" \
+    --result-filename "$FILENAME" \
+    --num-prompts "$NUM_PROMPTS"
+
+  echo "Completed benchmark with QPS: $qps"
+  echo "----------------------------------------"
+done
+
+echo "All benchmarks completed!"
+echo "Results saved to: $OUTPUT_DIR"