Inspect Claude Code Source

Extract and search Claude Code’s JavaScript source from its compiled binary.

Step 1: Determine current version

VERSION=$(basename "$(readlink ~/.local/bin/claude)")

Step 2: Extract source (if not already done)

Check if /tmp/claude-source/$VERSION/claude.js exists. If not, run the extraction script bundled with this skill:

python3 ~/.claude/skills/inspect-claude-source/extract.py --text-only

The script:

1. Finds the claude binary at ~/.local/bin/claude and follows the symlink to get the version
2. Uses otool -l to locate the __BUN/__bun Mach-O section (no hardcoded offsets)
3. Parses the Bun StandaloneModuleGraph footer to find module boundaries
4. Extracts all embedded JS modules, strips bytecode prefixes
5. Prettifies with prettier (via bunx)
6. Saves to /tmp/claude-source/<version>/
7. Skips if already extracted for this version

Options:

• --text-only – skip binary modules (.node, .wasm)
• --no-prettify – skip prettier formatting
• --binary PATH – use a different binary path
• --output-dir DIR – change output directory (default: /tmp/claude-source)

Step 3: Search or read the source

The main source file is /tmp/claude-source/<version>/claude.js (~520K lines prettified).

Other extracted modules:

• ripgrep.js – Native ripgrep addon wrapper
• image-processor.js – Image processing addon wrapper
• file-index.js – File indexing addon wrapper
• color-diff.js – Color diff addon wrapper

If the user provided a search term ($ARGUMENTS), search for it:

grep -n "$ARGUMENTS" /tmp/claude-source/$VERSION/claude.js | head -50

For broader exploration, use the Grep tool against /tmp/claude-source/<version>/claude.js.

Tips for reading the source

• The source is minified then prettified. Variable names are short (single letters or short identifiers like T, R, A, _, $).
• Function names from external packages are preserved (e.g. getUint32, randomUUID).
• String literals are preserved verbatim — search for user-facing strings, CLI flag names, error messages, and event type names to find relevant code.
• The code uses CommonJS (require, module.exports) wrapped in Bun’s CJS shim.
• Look for patterns like type: "assistant", type: "result", type: "system" to find event handling code.

Binary structure reference

Claude Code is a Bun-compiled single-file executable (Mach-O on macOS):

[Mach-O headers + Bun runtime]
[__BUN segment, __bun section]
  [8-byte header]
  [modules data: paths + contents interleaved]
  [modules metadata: 52 bytes per module]
  [32-byte footer fields]
  [16-byte trailer: "\n---- Bun! ----\n"]

The extraction uses otool -l to find the __BUN/__bun section offset and size, then parses the footer to locate module boundaries. This is stable across versions since it relies on the Mach-O segment/section structure rather than hardcoded byte offsets.