4/4 The fix upstream? Two characters, basically:uint32_t → size_t Weeks of debugging for one tiny type-width bug. Great reminder that in RL infra, the hardest part is often finding the right boundary around the failure. 👉Blog with the full investigation + the upstream vLLM PR: ai21.com/blog/vllm-cuda-inte…

→ View original post on X — @ai21labs, 2026-03-26 11:42 UTC