A crowbar for Claude Code's minified JavaScript innards

What it does

tweakcc is a CLI patcher for Claude Code. It modifies the tool’s minified cli.js—extracting and repacking the Bun native binary when necessary—to inject custom system prompts, themes, thinking verbs, spinner animations, and input highlighters. Your changes live in a local config file and get reapplied after official updates inevitably overwrite them.

The interesting bit

The project treats a closed-source terminal binary as a modding target. It uses node-lief to surgically extract JavaScript from Bun executables on macOS, Windows, and Linux, then patches and repacks them, effectively turning Claude Code into a user-tunable platform despite its monolithic packaging.

Key highlights

• Rewrites Claude Code’s system prompts and adds custom toolsets accessible via /toolset
• Themes, thinking verbs, spinners, and input-pattern highlighters for the terminal UI
• Supports both npm-based and native Bun-binary installations across all major platforms
• Includes an API and sandboxed adhoc-patch scripts for custom modifications without forking
• Claims roughly 50% faster startup by making MCP connections non-blocking

Caveats

• Verified only against Claude Code 2.1.62; newer or older versions may break non-system-prompt patches
• Several newer features listed in the README still carry the note: “Missing documentation for above features coming soon”

Verdict

Worth a look if you live in Claude Code and want to tune its personality, visuals, or behavior. Skip it if you prefer your terminal tools unmodified and update-safe.