Patch Claude Code's System Prompt with tweakcc

Claude Code’s built-in system prompt is large (50K+ tokens). tweakcc lets you patch it to remove sections you don’t need or inject custom instructions.

Install

npm install -g tweakcc

View the Current System Prompt

tweakcc show

This prints the full system prompt so you can see what Claude Code sends on every turn.

Remove Sections

# Remove the git commit instructions (if you never ask Claude to commit)
tweakcc patch --remove "Committing changes with git"

# Remove the PR creation instructions
tweakcc patch --remove "Creating pull requests"

Add Custom System Instructions

tweakcc patch --prepend "Always respond in British English. Never use American spellings."

Token Savings

A typical unmodified system prompt uses 50-60K tokens. Removing sections you never use can save 10-20K tokens per conversation, which adds up fast across sessions.

Reset to Default

tweakcc reset

Caution

Patches apply to your local Claude Code installation. Updates to Claude Code may overwrite your patches. Re-apply after updates.

When to Use

• You’ve audited the system prompt and found sections irrelevant to your work
• You want to enforce global behavior that CLAUDE.md can’t override
• You’re optimizing for token costs on high-volume usage