TL;DR
Bun 1.3 bundles many new capabilities into the Zig-written JavaScript runtime, adding server tooling, database clients, Redis support, isolated installs and more. The fast pace and growing scope have drawn both praise for performance improvements and criticism about feature creep and stability.
What happened
Bun 1.3 was released on October 13, 2025, continuing the project’s stated aim to replace fragmented JavaScript toolchains with a single runtime and toolkit. The update, described in a roughly 14,000-word post by creator Jarred Sumner and team, adds a full-stack development server with hot reloading, a SQL API with PostgreSQL, MySQL and SQLite clients, Redis support, enhanced routing, cross-platform compilation to standalone executables, a security scanner API, and isolated installs to limit dependency scope. The release also includes integration work between JavaScriptCore’s garbage collector and Bun’s event loop; an engineer claimed this reduced idle CPU by 100x and idle memory by 40%. Some components such as a Redis client were rolled out earlier in minor releases. Bun remains written in Zig and runs on Apple-sponsored JavaScriptCore; the project is open source under the MIT license. The team says this 1.3 release is the start of a series, with the Bake server postponed until it is ready.
Why it matters
- Consolidation: Bun’s all-in-one approach aims to simplify multiple frontend and backend tools into a single runtime, which could reduce configuration and integration overhead.
- Performance: Claimed reductions in idle CPU and memory use may lower hosting costs for some workloads if validated in production.
- Dependency safety: Isolated installs are designed to limit accidental cross-package dependency usage, addressing a common source of runtime errors.
- Ecosystem impact: Rapid expansion of features could reshape choices among Node.js, bundlers, test runners and other tools if adoption grows.
Key facts
- Bun 1.3 release date: October 13, 2025.
- The project is written in Zig and uses Apple-sponsored JavaScriptCore as its JS engine.
- New features announced include a full-stack dev server with hot reloading, a SQL API (Postgres, MySQL, SQLite), Redis support, enhanced routing, cross-platform compilation to standalone executables, a security scanner API, and isolated installs.
- Integration of JavaScriptCore’s garbage collector with Bun’s event loop was reported to reduce idle CPU by 100x and idle memory by 40%, per engineer Dylan Conway.
- The Bun team published about 14,000 words describing the 1.3 update.
- Bake, a built-in server intended to support React server components and server actions, was postponed and not included in 1.3.
- Bun is open source under the MIT license and claims over 5 million monthly downloads.
- Some users and contributors expressed concerns about rapid feature growth and occasional quality issues; reports of segmentation faults appear in the project’s issue list.
- The Zig language is still evolving (preview status cited; latest noted release was 0.15.1 at time of writing).
- Business model remains unclear; Sumner previously mentioned fast serverless hosting and a Reddit posting alluded to a future revenue product combining Bun with AI capabilities.
What to watch next
- The internal release and readiness of Bake, the built-in server for React server components and server actions.
- Stability reports after 1.3 adoption—particularly any frequency of segmentation faults or other memory errors.
- Whether Bun’s proposed business model (fast serverless hosting) or other revenue products materialize: not confirmed in the source.
Quick glossary
- JavaScript runtime: Software that executes JavaScript code outside a browser, providing APIs for file I/O, networking and other system services.
- Hot reloading: A development feature that applies code changes to a running application so developers can see updates without a full restart.
- Isolated installs: A dependency installation approach that confines package dependencies to package-specific directories to reduce accidental cross-package dependency usage.
- JavaScriptCore: Apple’s JavaScript engine used in WebKit; Bun uses an Apple-sponsored build of this engine.
- Zig: A general-purpose programming language focused on performance and safety; Bun is implemented in Zig.
Reader FAQ
Is Bake included in Bun 1.3?
No. Bake was intended for 1.3 but was postponed; the team said it was not ready and declined to delay the release.
Does Bun 1.3 include database clients?
Yes. The release adds a SQL API with PostgreSQL, MySQL and SQLite clients.
Are the claimed performance improvements independently verified?
Not confirmed in the source.
What is Bun’s business model?
Not confirmed in the source. Sumner has previously mentioned fast serverless hosting; a Reddit post hinted at a future AI-related revenue product.
DEVOPS 5 Bun 1.3 stuffs everything and kitchen sink into JS runtime All-in-one toolkit or over-ambitious feature creep? You decide Tim Anderson Mon 13 Oct 2025 // 15:17 UTC Version 1.3 of the Bun…
Sources
- Bun 1.3 stuffs everything and kitchen sink into JS runtime
- Bun 1.3 | Bun Blog
- Bun — A fast all-in-one JavaScript runtime
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