Buck2 vs Bun

Buck2 is a free build system from Meta for large-scale repositories that combine multiple programming languages. It uses Starlark rules, a dynamic dependency graph, and incremental actions to support extensible builds. Its language table lists prelude rules for C/C++, Erlang, Go, Haskell, Java, Kotlin, OCaml, Python, and Rust, though usability varies by language. Build actions can run remotely through services exposing Bazel's remote execution API; the project lists BuildBarn, BuildBuddy, EngFlow, and NativeLink as compatible with its distributed compilation support. Buck2 supports filesystem watching and can integrate with Meta's optional Eden virtual filesystem. Rules are hermetic by default and missing dependencies are errors, but local-only build steps are not sandboxed. The project describes Buck2 as early-stage and says it has no stable release tag; its latest binary tag changes with repository pushes. It warns that outside users may encounter rough edges, missing features, and missing toolchains. Source and binaries are available under MIT and Apache-2.0 licenses. The project directs users to GitHub for issue reports and offers a community Discord server.

Bun combines a JavaScript runtime, package manager, test runner, and bundler in one binary. It runs JavaScript and TypeScript on JavaScriptCore, with support for Node.js APIs and node_modules. Its npm-compatible package manager supports workspaces, catalogs, overrides, patches, readable lockfiles, private registry authentication, dependency resolution, and offline installation. The test runner includes Jest-compatible expectations, mocks, snapshots, DOM testing, and coverage. For builds, Bun handles TypeScript, JSX, CSS, and HTML for browsers and servers, and includes a development server with hot module reloading and single-file executables. Built-in APIs cover PostgreSQL, MySQL, SQLite, Redis, S3-compatible storage, HTTP, and WebSockets. The project names Next.js, Remix, Nuxt, Astro, SvelteKit, Hono, and Elysia among frameworks that run on Bun. It is MIT-licensed and developed publicly on GitHub. Bun runs on Linux, macOS, and Windows, subject to minimum OS versions and x64 processors with SSE4.2. Install options include an official script, npm, Homebrew, Windows package managers, and Docker. Support and discussion are available through Discord.