tweakcc for Claude Code
Tailor Claude Code’s prompts, toolsets, and terminal UI to the way you work.
- Source repo
- Piebald-AI/tweakcc
- Stars
- ★ 2.6k
- Last updated
- today
- License
- MIT
- Primary language
- TypeScript
- FA score
- 63/100 · Some gaps
At a glance
- How it runs
- Works with
- Platform-specificClaude Code
- Cost
- Free, no paid service needed
- Setup effort
- Low · running in minutes
- You'll need
- Typical use
- Claude Code users who want to edit the main system prompt, tool descriptions, or subagent prompts and keep those files under version control.
- Not a fit if
- Developers who do not use Claude Code
- Source review
- 63/100 · Some gaps
What does this agent do, and when should you use it?
tweakcc is a CLI tool and an npm dependency for customizing a local Claude Code installation. It offers an interactive terminal UI, --apply, the unpack, repack, and adhoc-patch subcommands, and an API that projects can call. Its built-in customizations cover system prompts, toolsets, themes, input highlighting, thinking verbs and animations, plus other patches. It supports npm and native binary installs on Windows, macOS, and Linux; for native installs it uses node-lief to extract and repack JavaScript in Claude Code’s Bun binary. Applied changes modify the Claude Code installation, while configuration is stored locally; Claude Code updates can overwrite changes, so customizations may need to be reapplied.
Run npx tweakcc to open the interactive terminal UI. Settings are stored in ~/.tweakcc/config.json, and system prompt files are Markdown files under system-prompts/ in the config directory. tweakcc --apply reads the config, restores the installation from backup, and applies enabled patches; --patches can limit the patch IDs. For npm installs, tweakcc modifies cli.js directly. For native installs, it extracts the JavaScript from the binary, patches it, and repacks the binary. unpack and repack support inspecting and writing JavaScript for native installs; adhoc-patch applies one-off string, regex, or Node.js script changes. As an npm dependency, the API can discover Claude Code installations, read and write their content, and create or restore backups.
- Claude Code users who want to edit the main system prompt, tool descriptions, or subagent prompts and keep those files under version control.
- Developers who want different sets of built-in tools for research, planning, or other modes can create toolsets and switch them with
/toolset. - Users who want to personalize Claude Code’s terminal appearance can create themes, change thinking verbs and animations, style user messages, or remove the input border.
- Users who want paths, environment variables, or custom regex patterns highlighted while typing can configure input pattern highlighters.
- Developers integrating Claude Code installation discovery, content access, or backup and restore into a project can use tweakcc’s npm API.
- Developers who need to inspect or modify JavaScript embedded in a native Claude Code binary can use
unpack,repack, oradhoc-patch.
How do you install or deploy this agent?
You can launch the interactive UI with npx without a global install, or add tweakcc as a project dependency to use its API. The README does not require a Claude API key; tweakcc targets a local Claude Code installation.
How do you use this agent?
Start the UI to configure customizations, then apply them to Claude Code:
npx tweakcc
npx tweakcc --applyTo use the API, add tweakcc to a project:
npm i tweakccTo customize system prompts, edit the Markdown files under ~/.tweakcc/system-prompts and apply the changes. Script-based adhoc-patch requires Node.js 20+:
What are this agent's strengths and limitations?
- Stores system prompt parts as separate Markdown files, so users can customize tool descriptions, subagents, and other prompt sections independently.
- Supports npm and native binary installs, with discovery and patching workflows documented for Windows, macOS, and Linux.
- Toolsets control which built-in tools are sent to the model and can be bound to Claude Code modes or changed with
/toolset. - Provides both a project-usable patching API and
adhoc-patchfor custom changes beyond its built-in features.
- It targets Claude Code; the documentation provides no support path for other coding agents or model providers.
- It modifies Claude Code’s executable content. Updates can overwrite customizations, which may require rerunning
--apply. - The README identifies Claude Code 2.1.162 as verified; non-prompt patches may not work on other versions.
- Fetching npx packages, remote configs, or remote patches requires network access; script-based
adhoc-patchalso requires Node.js 20+.
How does this agent compare with similar options?
The README distinguishes tweakcc toolsets from Claude Code’s built-in permission system: built-in tools outside the active toolset are not sent to the model. It also documents native binary and npm installs as the two supported Claude Code installation types.
Key facts side by side with the most closely related agents.
| Agent | Source review | Form / cost | Stars | Updated | Language | Full support on |
|---|---|---|---|---|---|---|
| tweakcc for Claude Code This agent | 63 · Some gaps | CLIFree | ★ 2.6k | today | TypeScript | Claude Code |
| OpenGAP | 51 · Major gaps | CLIFree + model costs | ★ 3k | 3mo ago | TypeScript | Codex · Claude Code · OpenAI API |
| System Prompts Leaks — The System Prompt Archive | 25 · Major gaps | Web appFree | ★ 70k | 2d ago | Python | — |
| Reasonix | 66 · Some gaps | CLIFree + model costs | ★ 36k | today | Go | OpenAI API |
How does FollowAgents rate this agent?
Why each dimension lost points
The README says apply displays a summary and asks for confirmation, and --restore can recover from a backup; --yes can bypass the prompt, and some automatic reapplication runs at session startup. The tool directly modifies Claude Code executables, while remote configs and scripts affect the local installation. Script sandbox limits and the risk of malicious patches are disclosed, but evidence for sensitive-data handling, permission boundaries, and dependency security is limited.
The documentation describes backup restoration, version-compatibility limits, patch failure handling, and update behavior; tests also cover configuration and patch planning. However, Claude Code changes can break non-prompt patches, and evidence for dependency availability and the full compatibility range is limited.
Features cover prompts, themes, toolsets, UI, patches, and automation, with support stated for multiple operating systems and native/npm installation paths. Version and patch boundaries are documented, but many features lack documentation and patch suitability depends on the target version; trigger and adaptation rules are not fully explained.
The README has a contents list, install commands, CLI/API guidance, examples, FAQ, troubleshooting, and known limitations; the MIT license is explicit. A version and update notes are visible, but the supplied material does not provide a complete release history, and maintenance responsibility and support commitments are only partly clear.
The tool centralizes Claude Code customization and retains settings across applications, with broad capabilities and examples for key workflows. It can modify executables and needs reapplication after updates, increasing operational and maintenance costs; usefulness also depends on the target version.
Specific CLI behavior, configuration options, tests, and workflow files support several claims, and the README distinguishes a verified version from inferred compatibility. Sources provide some corroboration, but there is no execution evidence, and many feature descriptions remain incomplete, limiting verification of the full set of product claims.
- The tool modifies Claude Code executables. Review the proposed diff and account for the documented version-compatibility limits and need to reapply after updates.
- Remote configs and ad hoc scripts affect the local installation. The documentation describes script sandboxing but warns that a script could still patch malicious code into Claude Code.
FAQ
Does tweakcc require a paid service or API key?
Will customizations survive a Claude Code update?
tweakcc --apply again to reapply customizations saved in the local config.Which Claude Code versions do the patches support?
Can an ad hoc patch script access files or the network?
adhoc-patch --script runs in an isolated Node.js child process with the experimental permission option in Node.js 20+ to restrict filesystem and network APIs. Scripts can still modify Claude Code’s executable content, so the README advises reviewing the proposed diff before applying it.