baoyu-electron-extract

Electron App Extract

Extracts resources and code from an installed Electron app's app.asar. When a .js.map is present, restores the original source files from the embedded sourcesContent; otherwise formats the minified code with Prettier. Source-map paths are resolved relative to the .js.map file first, so bundled paths like ../../src/main.ts restore to readable paths such as restored/src/main.ts instead of hashed placeholders. Always skips node_modules. Works on macOS and Windows.

User Input Tools

When this skill prompts the user, follow this tool-selection rule (priority order):

1. Prefer built-in user-input tools exposed by the current agent runtime — e.g., AskUserQuestion, request_user_input, clarify, ask_user, or any equivalent.
2. Fallback: if no such tool exists, emit a numbered plain-text message and ask the user to reply with the chosen number/answer for each question.
3. Batching: if the tool supports multiple questions per call, combine all applicable questions into a single call; if only single-question, ask them one at a time in priority order.

Concrete AskUserQuestion references below are examples — substitute the local equivalent in other runtimes.

Script Directory

Scripts in scripts/ subdirectory. {baseDir} = this SKILL.md's directory path. Resolve ${BUN_X} runtime: if bun installed → bun; if npx available → npx -y bun; else suggest installing bun. Replace {baseDir} and ${BUN_X} with actual values.

When to use

Use this skill whenever the user wants to look inside an installed Electron application or inspect its bundled code. Trigger phrases include:

• "extract Electron app", "decompile this Electron app", "unpack app.asar"
• "show me the source of <app>", "look inside <app>", "how is <app> built"
• "get the source code of Codex / Cursor / Discord / Slack / VS Code / Notion / Obsidian / ChatGPT desktop"
• "提取 Electron 应用", "看 <app> 的源码", "反编译 Electron", "解包 app.asar", "还原 source map"

Both app name (e.g., Codex) and absolute path (e.g., /Applications/Codex.app, a .asar file, or a Windows install dir) are accepted. The script handles discovery for both platforms.

Workflow

1. Determine the input. Ask the user for the app name or path if they haven't given one. If they want a custom output directory, ask for that too.

2. Run the script.

${BUN_X} {baseDir}/scripts/main.ts "<app>" [--output <dir>] [--asar <path>] [--force]

Start with --dry-run first if you're unsure whether discovery will find the right bundle — it prints the resolved paths and exits without touching the filesystem.

3. Handle the result.

• Success → report the output paths and the counts (extracted / restored / formatted).
• Multiple matches → the script lists candidates and exits non-zero. Show the user the candidates, ask which one to use (via AskUserQuestion or the runtime equivalent), then re-run with the chosen absolute path.
• Existing non-empty output dir → the script refuses without --force. Ask the user whether to overwrite (--force) or pick a new --output path.
• Unsupported platform / no match → suggest passing --asar /full/path/to/app.asar if the user knows where the bundle lives.

4. Point the user at the result. The default output dir is ~/Downloads/<AppName>-electron-extract/. The most interesting subdirectory depends on what was found:

• restored/ exists → the original source tree was reconstructed from .js.map files; this is what to read first.
• Only extracted/ exists (no maps) → the JS/CSS in extracted/ was Prettier-formatted in place; read from there.

Source-map path restoration

The script should preserve original source names and directory structure as much as the source map allows:

• Resolve each sources[] entry with sourceRoot when present, then relative to the .js.map file's directory inside extracted/.
• Collapse normal bundler-relative paths into the restored project tree. For example, .vite/main/index.js.map + ../../src/main.ts becomes restored/src/main.ts.
• If a source path climbs above extracted/, keep the readable remaining path under restored/ instead of hashing it. For example, .vite/main/index.js.map + ../../../shared/src/lib/foo.ts becomes restored/shared/src/lib/foo.ts.
• Strip URL/query decorations from source names, including common webpack://, file://, and ?loader suffixes.
• Use restored/__unknown/<hash>.<ext> only when the source name is empty or cannot be reduced to a safe file path.
• Continue skipping node_modules and webpack/runtime/* entries; these are bundler/runtime noise, not app sources.

Usage

# Extract by app name (default output: ~/Downloads/Codex-electron-extract/)
${BUN_X} {baseDir}/scripts/main.ts Codex

# Extract by absolute path (works for .app bundles, install dirs, or .asar files)
${BUN_X} {baseDir}/scripts/main.ts "/Applications/Visual Studio Code.app"
${BUN_X} {baseDir}/scripts/main.ts "C:\Users\you\AppData\Local\Programs\codex"
${BUN_X} {baseDir}/scripts/main.ts --asar /Applications/Codex.app/Contents/Resources/app.asar Codex

# Custom output
${BUN_X} {baseDir}/scripts/main.ts Codex --output ~/work/codex-source

# Preview discovery without writing anything
${BUN_X} {baseDir}/scripts/main.ts Codex --dry-run

# Overwrite an existing output dir
${BUN_X} {baseDir}/scripts/main.ts Codex --force

# Machine-readable result (one JSON line on stdout)
${BUN_X} {baseDir}/scripts/main.ts Codex --json

Options

Output layout

~/Downloads/<AppName>-electron-extract/
├── extract-report.json          # JSON summary: counts, warnings, resolved paths
├── extracted/                   # raw asar contents (JS/CSS Prettier-formatted when no map)
│   └── ...                      # node_modules left untouched (skipped from format)
├── extracted.unpacked/          # copied from <asar>.unpacked/ if present
│   └── ...                      # native modules (.node), large assets
└── restored/                    # only present if at least one .js.map was usable
    └── <original/source/tree>   # rebuilt from sourcesContent in each .js.map

Notes

• node_modules is always skipped — both for source-map restoration and Prettier formatting — because vendored dependencies are noise when inspecting an app.
• Source-map restoration only works when the .js.map embeds sourcesContent. This is the common case for modern bundlers (webpack, esbuild, Vite, rollup). If a map references external .ts/.js files without embedding them, that map is skipped and the corresponding .js is Prettier-formatted instead. Skipped maps are listed in extract-report.json under warnings.
• Readable paths over hashes — don't treat ../ segments in source-map paths as automatically unsafe. First resolve them from the map location and then sanitize the final output path so it still stays under restored/. Hash fallback is only for unusable source names.
• App discovery searches /Applications + ~/Applications on macOS, and %LOCALAPPDATA%\Programs, %PROGRAMFILES%, %PROGRAMFILES(X86)%, %APPDATA% on Windows. If discovery finds multiple matches, the script exits and lists them — re-run with an absolute path. On Linux or other platforms, pass --asar /path/to/app.asar explicitly.
• Safety — the script refuses to write to /, the user home directly, or the current working directory, and refuses to populate an existing non-empty output dir without --force.
• No global installs — @electron/asar and prettier are resolved on-the-fly via npx -y. First run will be slower while npx caches them.