Show HN: Customize Claude Code's System Prompt with Tweakcc (github.com)

tweakcc 2.0.0 is a lightweight interactive CLI that lets you deeply personalize Claude Code’s CLI experience — most notably it can now customize all of Claude Code’s system prompts. The tool provides a GUI HSL/RGB color picker for themes, custom thinking verbs and spinner animations, figlet banner text, styled user-message text, and options to remove the ASCII input-box border. It’s installable or runnable via npx/pnpm/dlx and supports Windows, macOS, and Linux across many JavaScript environment managers (not native installs yet). tweakcc is verified with Claude Code 2.0.25 and fixes a spinner-freeze bug when CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC is set; it also exposes CLAUDE_CODE_CONTEXT_LIMIT to change context limits for Anthropic-compatible custom APIs. Technically, tweakcc works by patching Claude Code’s minified cli.js while storing your customization state in ~/.tweakcc/config.js and backups of cli.js so changes can be reapplied after updates. It tracks system-prompt changes with hash caches in ~/.tweakcc and provides guidance for recovery if backups lead to a corrupted loop (delete cli.backup.js or reinstall a different Claude Code version). Limitations: some CLI output lacks coloring metadata and can’t be recolored, and native installs aren’t supported yet. Upcoming features include 70+ spinners, fine-grained markdown styling for responses, and configurable shimmering effects for thinking verbs. Overall, tweakcc enables reproducible, local UX experimentation and fine control over agent behavior and presentation.