Package and Bun bootstrap

This page documents how the extracted Claude Code package reaches the bundled cli.js runtime. It complements CLI main paths, which starts once the JavaScript entrypoint is executing.

Source anchors

Semantic alias	Source file	Approximate location	Anchor	Meaning
PackageInputExtractor	scripts/extract-claude-code-pkg.mjs	repository script	WRAPPER_PACKAGE, native package selection, .bun section extraction	Downloads package inputs and dumps the raw Bun payload section.
FinalArtifactExtractor	scripts/extract-claude-code-final-artifacts.mjs	repository script	TRAILER, MODULE_RECORD_SIZE, FINAL_ROOT_FILES, UNWANTED_FINAL_OUTPUTS	Parses the Bun graph in memory, keeps only selected JS files, and prunes graph/JSC/prompt/native generated outputs.
BunEntrypointWrapper	cli.js	line ~1, byte 0x3	// @bun @bytecode @bun-cjs	Bun wrapper header.
EmbeddedRuntimeVersion	cli.js	line ~11, byte 0xdc5	VERSION:"2.1.143"	Embedded runtime version constant.
OuterBootstrap	cli.js	line ~19590, byte 0xddd998	async function J9A	Outer JavaScript bootstrap.
BootstrapLazyMainImport	cli.js	line ~19592, byte 0xddfe32	let{main:f}=await Promise.resolve().then(() => (p08(),zo6))	Lazy initialization of the main bundled module.

Startup layers

sequenceDiagram
    autonumber
    participant Npm as npm wrapper
    participant Native as platform package
    participant Bun as Bun standalone executable
    participant Graph as .bun StandaloneModuleGraph
    participant Cli as cli.js
    participant Main as Main bundle export / top-level main

    Npm->>Native: selects platform-native package
    Native->>Bun: runs native `claude` executable
    Bun->>Graph: loads .bun section payload
    Graph->>Cli: executes graph entrypoint
    Cli->>Cli: outer bootstrap handles version/daemon shortcuts
    Cli->>Main: initializes main module and calls exported main

Bun payload contents

The Bun payload contains five modules. Only one is the full runtime entrypoint; two are JavaScript shims; two are stripped native shared objects. The final retained artifact set keeps the three readable JavaScript files and prunes the native .node binaries.

Module	Loader	Role
/$bunfs/root/src/entrypoints/cli.js	js	Main CLI/runtime bundle and the primary readable analysis target.
/$bunfs/root/image-processor.js	js	Shim requiring image-processor.node.
/$bunfs/root/audio-capture.js	js	Shim requiring audio-capture.node.
/$bunfs/root/image-processor.node	napi	Embedded stripped Linux x86-64 image-processing native module.
/$bunfs/root/audio-capture.node	napi	Embedded stripped Linux x86-64 audio-capture native module.

Temporary graph inspection found no serialized sourcemap payload, so analysis must use the bundled JavaScript, exact strings, and byte offsets. JSC bytecode dumps remain possible with the optional helper script, but they are not retained as final artifacts.

Outer bootstrap behavior

OuterBootstrap is the outer JavaScript bootstrap. It performs a few fast paths before importing the full main module:

1. Reads process.argv.slice(2).
2. Handles --version, -v, or -V with optional --verbose before full main import.
3. Checks background/daemon helper paths.
4. Records startup profiling events such as cli_entry and cli_before_main_import.
5. Lazily initializes the main module, reads the exported main, and awaits it.

The important runtime boundary is the lazy edge from OuterBootstrap to the main bundle export: everything before it is startup shell, while TopLevelMain and CommanderRoot own the full CLI runtime.

Caveats

• The wrapper/native package directories and generated metadata.json are pruned by the final-artifact extractor.
• JavaScriptCore bytecode is not recovered source and is not retained in the simplified final artifact layout.
• Minified bootstrap symbols are version-specific. Use exact strings and offsets when comparing package versions.

Related docs

• CLI main paths
• cli.js overview