Bun 1.1.13 addresses memory leaks as developers report production crashes

Bun 1.1.13 has been released with critical memory management improvements following widespread developer complaints about memory leaks causing production crashes and slowdowns. The update, from Anthropic's JavaScript runtime, addresses stability issues that have plagued long-running Bun deployments.

The new version introduces several key improvements beyond memory fixes. The test runner now includes an isolate flag for running each test in a fresh environment, a parallel flag for concurrent test execution across user-defined processes, and a shard flag for splitting tests across multiple runners - all designed to match Jest's syntax for easier migration.

Compression performance has also been enhanced through adoption of zlib-ng, an optimized fork of zlib that delivers up to five times faster compression without requiring code changes.

However, the most significant changes target memory management. Bun inventor Jared Sumner claims the runtime now uses 5% less memory overall. More importantly, an upgraded memory allocator combined with a Libpas scavenger implementation returns unused memory to the operating system more quickly. According to Sumner, these changes "reduce baseline memory usage and fix a class of hangs and crashes in long-running processes."

These improvements directly address developer complaints that have circulated widely. One Reddit user stated bluntly that "Bun is not stable enough for production nor faster than Node in production," attributing this to memory leaks. The user noted that while developers using Bun as a build toolkit might not notice issues, production deployments with "long running workloads amplifying problems that short benchmarks never reveal" face significant challenges.

The memory issues have prompted some developers to abandon Bun entirely. Jay V, founder of OpenCode, announced on X that his team is "moving to Node and Electron, away from Bun and Tauri," citing memory issues, crashes, and "terrible Windows support." He advised that "Bun is not a good fit for apps with a large user base, you should just stick to Node."

Despite these criticisms, Bun maintains a strong following for its speed and rich feature set. Many developers report satisfaction with the runtime, praising its performance and comprehensive standard library. The divide between positive experiences and production failures suggests that Bun's stability may depend heavily on specific use cases and deployment patterns.

Reports of garbage collection failures with certain functions leading to out-of-memory errors have been particularly concerning. These issues appear to manifest primarily in long-running processes, where memory leaks accumulate over time rather than in short benchmark tests.

Bun's rapid development cycle since its first production release in September 2023 has contributed to both its feature richness and stability challenges. Some users have expressed a preference for slower feature development in exchange for greater stability focus.

The memory management improvements in 1.1.13 represent Anthropic's response to these production concerns. Whether these fixes will be sufficient to address the stability issues that have driven some developers away remains to be seen, but the attention to memory leaks suggests the company is taking production reliability seriously.

For developers currently using Bun in production environments, the update appears essential. Those considering Bun for new projects should weigh the performance benefits against the documented stability concerns, particularly for applications requiring long-running processes or serving large user bases.

Bun continues to compete with Node.js (version 25.9) and Deno, developed by Node.js creator Ryan Dahl. Its acquisition by Anthropic in December 2025 has brought additional resources but also heightened scrutiny of its production readiness.