fix: cap uv concurrency to prevent ENFILE errors during bundling#14
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eoinsha merged 1 commit intofourTheorem:feat/builder-containerfrom Apr 17, 2026
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When uv extracts many wheel files in parallel, the builder container can exhaust the system-wide file descriptor limit (os error 23: Too many open files), especially on Docker Desktop/macOS environments. Add UV_CONCURRENT_DOWNLOADERS=4 and UV_CONCURRENT_BUILDS=2 to the builder environment to limit uv's internal parallelism. This prevents the FD exhaustion without meaningfully impacting performance, since most wheels are served from cache on subsequent builds. Fixes intermitent 'CommandExitedWithNonZeroStatus: docker exited with status 1' errors caused by failed wheel extraction.
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Problem
When
uvextracts many wheel files in parallel, the builder container canexhaust the system-wide file descriptor limit (
os error 23: Too many open files), especially on Docker Desktop/macOS environments.This causes intermittent failures like:
Solution
Add
UV_CONCURRENT_DOWNLOADERS=4andUV_CONCURRENT_BUILDS=2to the buildercontainer environment to limit
uv's internal parallelism.These are official uv concurrency settings that prevent FD exhaustion without meaningfully impacting performance.\n\n## Verification
All 30 tests pass consistently across 5 consecutive runs (150 total executions, zero failures).