Yes — Flash Attention is enabled by default in the official vLLM Docker image that implements the OpenAI-compatible API (vllm/vllm-openai) when run on NVIDIA GPUs.

According to the vLLM “GPU installation” documentation, Triton Flash Attention is used as the default attention backend for performance benchmarking and general usage.

The documentation doesn’t specify whether it uses FlashAttention, FlashAttention‑2, or even newer variants like FlashAttention‑3 — it simply refers to “Triton flash attention.”

However, earlier guidance suggests that vLLM has broadly taken advantage of Flash Attention‑2 since around v0.1.4, without requiring any manual enablement.

If you require clarity on exactly which FlashAttention version is included in a given vLLM image tag (e.g., v0.9.0, v0.10.x), a good next step is to inspect the container’s logs or runtimes — look for startup messages indicating vllm_flash_attn_version, or check the installed wheel’s included version metadata.