Bun v1.4.3 adds built-in TypeScript checks and runtime efficiency gains

Bun v1.4.3, released October 10, 2026, combines a built-in TypeScript checker with runtime, build, and compatibility improvements. The release fixes 166 issues and gives teams already using Bun a faster checking path, lower idle CPU use, and more control over code generation and compilation output.

• Bun check type-checks 10,947 VS Code files in 1.75 seconds using 2.77 GiB, compared with 5.88 seconds and 9.23 GiB for tsc7 with 16 checkers, and 12.58 seconds and 7.73 GiB for tsc 7 with default settings.
• The release reports 67–89% less idle CPU, up to 2.7x faster handling of large node:http responses, and a JavaScriptCore upgrade with faster JSON.parse.
• Bun v1.4.3 fixes 166 issues, including Node.js compatibility improvements, and adds --disallow-code-generation-from-strings, Bun.FetchSession, and experimental Bun.ModuleGraph.
• Build and deployment changes include lower bun build memory use with many entry points, [hashN] output names, and profile-guided bytecode layout with faster startup for --compile --bytecode.

Bottom line If Bun is part of your toolchain, test v1.4.3 in CI and review the experimental and security-relevant flags before upgrading production workloads.