Apps

Bun ships as a single executable with many subcommands. Each "app" in this section is one subcommand or one major user-facing surface. They share a process, an event loop, and most subsystems — they are not separate binaries.

The CLI dispatcher is in src/cli.zig (~78,000 lines of Zig). It parses argv via src/cli/Arguments.zig, picks a Command enum variant, and calls the matching *_command.zig file under src/cli/.

Subcommands and their entry points

Subcommand	Entry point	Page
bun run, bun ./script, bun -e ...	src/cli/run_command.zig	Runtime
bun install, bun add, bun remove, bun update, bun pm, bun outdated, bun audit, bun publish, bun pack, bun why, bun link/unlink, bun patch/patch-commit	src/cli/install_command.zig and friends	Package manager
bun build, Bun.build	src/cli/build_command.zig, src/bundler/bundle_v2.zig	Bundler
bun test	src/cli/test_command.zig	Test runner
bun x, bunx	src/cli/bunx_command.zig	bunx
bun init, bun create	src/cli/init_command.zig, src/cli/create_command.zig	Misc commands
bun repl	src/cli/repl_command.zig	Misc commands
bun upgrade	src/cli/upgrade_command.zig	Misc commands
bun completions	src/cli/install_completions_command.zig	Misc commands
Embedded shell (Bun.$)	src/shell/interpreter.zig	Shell
Dev server (Bake)	src/bake/DevServer.zig	Bake (dev server)

How a command is dispatched

sequenceDiagram
    participant Sh as Shell
    participant Main as src/main.zig
    participant Bun as src/bun.zig
    participant CLI as src/cli.zig
    participant Args as src/cli/Arguments.zig
    participant Cmd as src/cli/<cmd>_command.zig

    Sh->>Main: argv
    Main->>Bun: bun.main()
    Bun->>Bun: install allocator + crash handler + signals
    Bun->>CLI: Cli.start(allocator)
    CLI->>Args: Arguments.parse(argv)
    Args-->>CLI: parsed options + Command tag
    CLI->>Cmd: Command.exec(ctx)
    Cmd-->>CLI: exit code
    CLI-->>Sh: exit

The dispatcher is also responsible for recognising bun invocations made through node shims (bun --bun node ...), Yarn-equivalent commands (bun add ↔ yarn add), and shell completions.

Shared building blocks

Every app pulls from the same core library:

• Logger — src/logger.zig (~55 KB) — diagnostics, error rendering, source-mapped stack traces.
• Output — src/output.zig (~46 KB) — stdout/stderr with <r><red>...</r> ANSI markup.
• fs / sys — src/fs.zig, src/sys.zig (~165 KB) — POSIX/Windows abstractions. All file I/O goes through sys.zig.
• HTTP client — src/http/HTTPThread.zig — used by fetch(), bun install, bunx, bun upgrade.
• JSON parser — src/json_parser.zig — used by every package.json reader.

When you change one of these, audit every command that uses it.

Active contributors

For per-subsystem ownership and active contributors, see maintainers.