Bun

Active advisories

1. mediumInvestigating

   Bun Startup Time Scales Excessively with Large Directories in CWD or Ancestor Paths

   Bun startup performance degrades significantly when executed in or beneath directories containing large numbers of entries. The issue affects macOS (Darwin arm64) users on versions 1.4.2 through 1.4.4 and higher.

   Bun

   since Nov 7, 17:08 UTC·2 h 47 minv1.4.2+744846f84, 1.4.4+38afee6c8

   Velocity

   7.5

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2. highInvestigating

   Bun Build --no-bundle Rewrites Top-Level This to Exports, Breaking Browser Scripts

   When using `bun build --no-bundle` for transpile only, Bun replaces every top-level `this` in a non-module file with `exports`, which breaks browser scripts and UMD libraries where top-level `this` refers to the global object. This affects browser targets with or without minification across all formats.

   Bun

   since Nov 7, 16:36 UTC·3 h 18 minv1.4.4+38afee6c8, 1.4.4-canary.1+7ca0042d3

   Velocity

   6.7

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3. minorInvestigating

   Bun Lint Reports False prefer-readonly-parameter-types Findings Based on File Sharing

   Bun lint with typeAware = true produces inconsistent findings on the same code tree depending on which files share a checker. This causes false @typescript-eslint/prefer-readonly-parameter-types findings due to cached synthesized properties.

   Bun

   since Nov 7, 14:49 UTC·5 h 6 min

   Velocity

   6.3

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4. minorInvestigating

   Bun 1.4.4 bun fmt --doctor Incorrectly Flags Required Prettier Plugins

   In Bun v1.4.4, running `bun fmt --doctor` incorrectly instructs users to remove a Prettier plugin that is still required and loaded by a script in `.prettierrc`. Developers using Bun's formatting diagnostics alongside custom Prettier configurations are affected.

   Bun

   since Nov 7, 02:59 UTC·16 h 56 minv1.4.4

   Velocity

   3.8

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5. mediumInvestigating

   Bun Transpiler Incorrectly Rewrites `return undefined` in Async Generators

   In Bun 1.4.4, the transpiler simplifies `return undefined;` and `return void 0;` to `return;` inside async generator bodies, skipping the required microtask tick. This affects `bun run`, `Bun.Transpiler`, and `bun build`, altering promise resolution order.

   Bun

   since Nov 7, 02:37 UTC·17 h 17 minv1.4.4

   Velocity

   3.7

   Share
6. minorInvestigating

   Bun Bun.WebView navigate() and Chrome screenshot() Slower Than Playwright

   A performance issue was reported in Bun where Bun.WebView navigate() is 1.6x slower and Chrome screenshot() is 1.5x slower compared to Playwright. The behavior was observed on Bun 1.4.4 running on macOS arm64.

   Bun

   since Nov 6, 11:45 UTC·1 d 8 hv1.4.4+38afee6c8

   Velocity

   2.1

   Share
7. mediumWorkaround available

   Bun 1.4.4 Module Cache Eviction Failure on Link Error

   Bun 1.4.4 introduced a regression where a module left unevaluated due to its importer's link error can no longer be evicted from require.cache. This issue works correctly in version 1.4.2.

   Bun

   since Nov 6, 10:07 UTC·1 d 9 hv1.4.4

   Velocity

   2.0

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8. mediumInvestigating

   Bun `bun lint` Fails With Script Not Found Error in Workspaces

   Users running `bun lint` within a workspace encounter an "error: Script not found "lint"" message, despite the documentation stating it requires no installation or configuration. Meanwhile, `bun fmt` continues to function as expected.

   Bun

   since Oct 29, 10:58 UTC·9 d 8 hv1.4.4+38afee6c8

   Velocity

   0.3

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9. mediumInvestigating

   Bun Isolated Linker Duplicates Expo Modules When expo-router Added

   An issue in Bun 1.4.4-canary.1+6bb5dc195 on Windows x64 causes the isolated linker to duplicate Expo modules when expo-router is added after a specific fix. Developers working with workspaces and Expo are affected.

   Bun

   since Oct 20, 15:25 UTC·18 d 4 hv1.4.4-canary.1+6bb5dc195

   Velocity

   0.1

   Share

Version hazard notices

• Avoid:Bun 1.4.4+38afee6c8, 1.4.4-canary.1+7ca0042d31 active high-severity incident
  • highInvestigatingBun Build --no-bundle Rewrites Top-Level This to Exports, Breaking Browser Scripts
• Use with caution:Bun 1.4.2+744846f84, 1.4.4+38afee6c81 active medium-severity incident
  • mediumInvestigatingBun Startup Time Scales Excessively with Large Directories in CWD or Ancestor Paths
• Use with caution:Bun 1.4.43 active medium-severity incidents
  • mediumInvestigatingBun Transpiler Incorrectly Rewrites `return undefined` in Async Generators
  • mediumWorkaround availableBun 1.4.4 Module Cache Eviction Failure on Link Error
  • minorInvestigatingBun 1.4.4 bun fmt --doctor Incorrectly Flags Required Prettier Plugins
• Use with caution:Bun 1.4.4-canary.1+6bb5dc1951 active medium-severity incident
  • mediumInvestigatingBun Isolated Linker Duplicates Expo Modules When expo-router Added
• Use with caution:Bun 1.4.4+38afee6c82 active medium-severity incidents
  • mediumInvestigatingBun `bun lint` Fails With Script Not Found Error in Workspaces
  • minorInvestigatingBun Bun.WebView navigate() and Chrome screenshot() Slower Than Playwright

Resolved incident history

No resolved incidents on record yet.