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Bun Vendored libuv Lacks PROC_THREAD_ATTRIBUTE_HANDLE_LIST Fix

  1. Investigating(current)
  2. Trending(upcoming)
  3. Workaround available(upcoming)
  4. Resolved(upcoming)

Executive summary

Bun versions v1.4.3, v1.4.4, and main vendor a libuv branch that predates libuv upstream commit #5100, which adds Windows PROC_THREAD_ATTRIBUTE_HANDLE_LIST support in uv_spawn. The issue is tracked in GitHub issue #48351.

No verified workaround yet

None of the linked reports describe a mitigation. Follow this incident to hear when one appears.

Official fix
Technical root cause

The vendored libuv commit pinned in scripts/build/deps/libuv.ts is older than upstream libuv's fix for PROC_THREAD_ATTRIBUTE_HANDLE_LIST on Windows.

Evidence

1 report · 1 GitHubShow
  1. [1]
    GitHub First report
    src/deps/libuv: the vendored bun branch predates libuv#5100 (PROC_THREAD_ATTRIBUTE_HANDLE_LIST)(opens GitHub issue in a new tab)

    What The libuv source Bun vendors is pinned in scripts/build/deps/libuv.ts to LIBUV_COMMIT = "8023581113b276e7c1aee3f82da57ca0893faab1" at bun-v1.4.3, bun-v1.4.4 and main. That commit is the tip of oven-sh/libuv's bun branch, based on upstream f3ce527ea940d926c40878ba5de219640c362811 (2025-10-07). It does not contain libuv#5100 (win: use PROC_THREAD_ATTRIBUTE_HANDLE_LIST in uv_spawn, merged 2026-05-13, merge commit 9f5306fa36b2f39aed6470189269cba5e4c9ab42): GET…

    by mq1n 0upvotes 2comments

Timeline

  1. First report on GitHub issue

    src/deps/libuv: the vendored bun branch predates libuv#5100 (PROC_THREAD_ATTRIBUTE_HANDLE_LIST)

    Source