tweakcc
tweakcc is a CLI tool that upgrades your Claude Code experience. Customize its system prompts, add custom themes, create toolsets, and personalize the UI. From the team behind 
Piebald.
NEW in 4.0.0: tweakcc now has an API; use npm i tweakcc to add to your project and see API!
NEW in 4.0.0: You can now create custom patches via sandboxed scripts! Works with native installations. No need to fork tweakcc just to make a quick patch! See tweakcc adhoc-patch.
NEW in 4.0.0: You can also apply customizations from a remote URL to a config file. See Remote Config.
Also see tweakcc --restore, tweakcc unpack, and tweakcc repack.
NEW: tweakcc 4.0.0 also introduces several new patches:
With tweakcc, you can
- Customize all of Claude Code’s system prompts (NEW: also see all of Claude Code’s system prompts)
- Create custom toolsets that can be used in Claude Code with the new
/toolset command
- Highlight custom patterns while you type in the CC input box with custom colors and styling, like how
ultrathink used to be rainbow-highlighted.
- Manually name sessions in Claude Code with
/title my chat name or /rename (see our blog post for implementation details)
- Create custom themes with a graphical HSL/RGB color picker
- Add custom thinking verbs that will show while Claude’s working
- Create custom thinking spinner animations with different speeds and phases
- Style the user messages in the chat history beyond the default plain gray text
- Remove the ASCII border from the input box
- Expand thinking blocks by default, so that you don’t need to use the transcript (Ctrl+O) to see them
- Configure which Claude model each subagent (Plan, Explore, and general-purpose) uses
- Switch between table formats - Claude Code default, Unicode (
┌─┬─┐), ASCII/markdown (|---|), Unicode without top/bottom borders.
tweakcc also
- Fixes a bug where the spinner animation is frozen if you have the
CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC environment variable set (#46)
- Allows you to change the context limit (default: 200k tokens) used with models from custom Anthropic-compatible APIs with a new environment variable,
CLAUDE_CODE_CONTEXT_LIMIT
- Adds the
opusplan[1m] model alias, combining Opus for planning with Sonnet’s 1M context for execution—reducing “context anxiety” (#108)
- Adds a message to Claude Code’s startup banner indicating that you’re running the patched version of CC (configurable)
- Speeds up Claude Code startup by ~50% with non-blocking MCP connections and configurable parallel connection batch size (#406)
tweakcc supports Claude Code installed on Windows, macOS, and Linux, both native/binary installations and those installed via npm, yarn, pnpm, bun, Homebrew/Linuxbrew, nvm, fnm, n, volta, nvs, nodenv, and Nix (including NixOS and nix-darwin), as well as custom locations.
tweakcc supports Claude Code’s native installation, which is a large platform-specific Bun executable. Current Claude Code releases store the application as a graph of code-split JavaScript modules rather than one embedded cli.js; tweakcc discovers and updates the owning modules while preserving Bun’s compiled graph layout. We support patching the native binary on macOS, Windows, and Linux, including ad-hoc signing on Apple Silicon, via node-lief, our Node.js bindings for LIEF (Library to Instrument Executables).
While tweakcc has a large library of built-in patches, you can create custom patches by using tweakcc’s API. If you don’t want to create an npm package, you can use tweakcc adhoc-patch, which applies a custom Node.js script to your default Claude Code installation. Because adhoc-patch supports running scripts from an HTTP URL, you can even host a script on a GitHub Gist or pastebin for easy distribution.
Run without installation:
$ npx tweakcc
# Or use pnpm:
$ pnpm dlx tweakcc
Table of contents
How it works
tweakcc works by patching Claude Code’s minified cli.js file, reading customizations from ~/.tweakcc/config.json. For npm-based installations cli.js is modified directly, but for native installations it’s extracted from the binary using node-lief, patched, and then the binary is repacked. When you update your Claude Code installation, your customizations will be overwritten, but they’re remembered in your configuration file, so they can be reapplied by just running npx tweakcc --apply (you’ll see a pre-apply summary and be asked to confirm; use --yes / -y to skip the prompt in scripts).
tweakcc is verified to work with Claude Code 2.1.162. In newer or earlier versions various patches might not work. However, if we have the system prompts for your version then system prompt patching is guaranteed to work with that version, even if it’s significantly different from the verified CC version—the version number stated above is only relevant for the non-system-prompt patches. We get the latest system prompts within minutes of each new CC release, so unless you’re using a CC version older than 2.0.14, your version is supported.
You can also create custom patches using tweakcc without having to fork it or open a PR. tweakcc adhoc-patch supports using custom scripts that work with native and npm-based installs and that automatically detect your Claude Code installation.
Remote Config
While tweakcc usually works by applying customizations from your local ~/.tweakcc/config.json, you can optionally pass the --config-url <http URL> flag when you use tweakcc --apply to have tweakcc fetch config from a remote URL and apply it to your local Claude Code installation. This is useful for testing someone else’s config when shared via a Gist or pastebin, for example.
Example:
npx tweakcc@latest --apply --config-url https://gist.githubusercontent.com/bl-ue/27323f9bfd4c18aaab51cad11c1148dc/raw/b24b5fe08874ce50f4be6c093d9589d184f91a70/config.json
Your local config will not be overwritten; the remote config will be copied into your config.json under remoteConfig.settings.
Guard automatic updates
The Prevent updates to unsupported versions toggle in Misc settings enables
settings.misc.preventUpdateToUnsupportedVersions (default: false). Native and
npm automatic updates then require an HTTP 200 response for the target version’s
prompt snapshot in the official TweakCC repository. Missing snapshots, network
errors, and checks taking longer than five seconds block that automatic update.
The native guard checks the final target after Claude Code’s canary selection and
version caps. Legacy npm automatic installers use the exact checked version rather
than resolving a moving stable or latest tag again. Manual claude update / claude install calls and package-manager
updates are intentionally unchanged. Verified layouts are the 2.1.20 npm bundle
and the split native bundle in 2.1.261; an unknown layout is reported as a failed
patch rather than partially instrumented.
A published snapshot means prompt data is available, not that every patch in
your installed TweakCC release supports that Claude Code version. A successful
update replaces the patched executable, so reapply TweakCC after updating to
restore this guard and your other customizations.
Keep customizations across Claude Code updates
A native Claude Code install keeps every version under
~/.local/share/claude/versions/ and re-checks an already-installed version
whenever it switches to it: claude update, claude install <version>, and the
auto-updater of any Claude Code session still running an older version all hash
the retained file and compare it with the checksum in Anthropic’s signed release
manifest. A tweakcc-patched binary never matches, so it is silently replaced by
the stock build of the same version. autoUpdates: false in ~/.claude.json
does not prevent this on a native install (the native installer sets
autoUpdatesProtectedForNative, which makes Claude Code ignore that setting);
only DISABLE_AUTOUPDATER=1 / DISABLE_UPDATES=1 in the environment or in the
env block of settings.json stop the automatic checks.
tweakcc handles this in two parts:
- Keep patched binary on update (
settings.misc.keepPatchedBinaryOnUpdate,
default true, native installs only). Each --apply records the SHA-256 of the
binary it wrote in applied.json in the tweakcc config directory. The patched
installer still fetches and verifies the signed manifest, but treats a retained
binary as valid when its SHA-256 equals the value recorded for that path and
version. Any other modification is still repaired by a re-download, and new
downloads are verified exactly as before. The trade-off: Claude Code no longer
repairs that one file, and anything that can write both the binary and
applied.json (both are owned by your user) can make a modified binary persist.
Only binaries that already contain this patch apply the rule, so the first
update from a Claude Code process started before you applied it can still
replace the binary.
- Re-apply after Claude Code replaces the binary:
tweakcc --install-hook
adds a SessionStart hook (matcher startup|resume) to Claude Code’s settings.json
($CLAUDE_CONFIG_DIR or ~/.claude). On each session start it checks, in about
0.2 s, whether the active binary is the one recorded in applied.json. If not
(a new version, or the same version downloaded again), it starts
tweakcc --apply detached, logs to auto-apply.log, shows a one-line
message, and returns immediately. The new customizations take effect the next
time Claude Code starts. A new version’s binary becomes the backup only after
its SHA-256 is found in Anthropic’s release manifest for that version, and
nothing is applied when tweakcc has no prompt data for the version yet. A failed
run is retried at most once an hour. The hook runs tweakcc with the Node and
script path that installed it, so install tweakcc globally rather than via
npx. Remove it with tweakcc --remove-hook. Restoring Claude Code
(--restore) clears applied.json, which also stops the hook from re-applying.
On Linux, a systemd user path unit watching
~/.local/share/claude/versions/ that runs tweakcc --apply --yes is an
alternative to the hook that also covers updates made while no session starts.
CLI Commands
In addition to the interactive TUI (npx tweakcc) and the --apply flag, tweakcc provides three subcommands for advanced use: unpack, repack, and adhoc-patch.
--apply and --patches
npx tweakcc --apply reads your saved customizations from config.json and patches Claude Code. Before applying, tweakcc restores Claude Code from its backup so patching always starts from a clean slate (see Troubleshooting).
Use tweakcc --apply with no filter as the default way to apply all enabled patches from your config.
--patches <ids> limits which patches are applied, but it is not additive: tweakcc still restores from backup first, then applies only the listed patch IDs. Any previously applied patches that are not in the list are removed from the binary. For example, if you have both themes and user-message-display enabled and run tweakcc --apply --patches themes, only the themes patch remains in Claude Code.
List available patch IDs with tweakcc --list-patches (or tweakcc --list-system-prompts [version] for system prompt IDs).
unpack
Extract the embedded JavaScript from a native Claude Code binary and write it to a file. This is useful for inspecting Claude Code’s source, writing custom patches, or making manual edits before repacking. Note that unpack only works with native/binary installations; it will error if pointed at an npm-based installation (cli.js), because it can already be read directly from disk. unpack takes the path to the JS file to write to, and an optional path to a native binary, which if omitted will default to the current installation.
npx tweakcc unpack <output-js-path> [binary-path]
repack
Read a JavaScript file and embed it back into a native Claude Code binary. This is the counterpart to unpack — after inspecting or modifying the extracted JS, use repack to write it back. Like unpack, this only works with native installations. repack takes a path to a JS file to read from, and an optional path to a native binary, which if omitted, as above, will default to the current installation.
npx tweakcc repack <input-js-path> [binary-path]
Example:
# Extract, edit, and repack
npx tweakcc unpack ./claude-code.js
# ... make your edits to claude-code.js ...
npx tweakcc repack ./claude-code.js
adhoc-patch
Apply a one-off or ad-hoc patch to a Claude Code installation without going through the tweakcc UI or config system. It supports three modes and works with both native and npm-based installations.
3 modes of patching are supported.
--string
A fixed/static old string is replaced with a fixed/static new string, analogous to grep -F.
- By default, all instances of the old string are replaced, but you can use
--index to specify a particular occurrence by 1-based index, e.g. --index 1 to replace only the first, --index 2 to replace only the second, etc.
--regex
All matches of a regular expression are replaced with a new string.
-
The new string can contain $D replacements, where D is the 0-based index of a group matched by the regular expression; $0 = the entire matched text, $1 = the first user-defined match group, etc.
-
The regular expression must begin and end with a forward slash in JavaScript style, e.g. /my.+regex/. An optional list of flags—characters from the set g, i, m, s, u, and y—may be appended after the last delimiting forward slash, e.g. /claude/ig
-
Like --string, --regex supports the use of --index to specify by index which occurrence to replace, without which all occurrences are replaced.
--script
This is the most powerful option. A short snippet of JavaScript code running in Node.js takes the JavaScript content of the CC installation as input and returns the entire input, modified as output.
-
Security: The script is run in a sandboxed/isolated node child process with the --experimental-permission option to prevent the script from using file system and network APIs. This option requires that you have Node.js 20+ installed and on your PATH. Due to this sandboxing, scripts themselves (including those downloaded from HTTP URLs) are safe to run without prior review; however, because the scripts are patching Claude Code, which is an executable, it’s technically possible for a script to patch malicious code into your Claude Code executable that would execute when you run claude. As a result, it’s highly advised to review the diff tweakcc prints when it asks you if you’d like to apply the changes proposed by the patch.
-
Input/output: Claude Code’s JavaScript code is passed to the script via a global variable, js, available inside the script’s execution context. To return the modified file content, simply use the return keyword. For example, to write a very simple script that replaced all instances of "Claude Code" with "My App", you could write the following:
js = js.replace(/"Claude Code"/g, '"My App"');
return js;
-
Utility vars: Because complicated patches may need to make use of common functions and global variables like chalk, React, require, and the low-level module loader function, and also common Ink/React components like Text and Box, tweakcc also provides a vars global variable to the script. vars is an object containing the names of the common variables listed above; here’s an example:
const vars = {
chalkVar: 'K6',
moduleLoaderFunction: 's',
reactVar: 'Yt8',
requireFuncName: 'C1',
textComponent: 'f',
boxComponent: 'NZ5',
};
-
Script source: Scripts can be passed in 3 ways: directly on the command-line, via a local file on disk, and via an HTTP URL. In order to specify a file, pass the path to the file prefixed with @ (similar to curl -d). To specify an HTTP URL, use @ and ensure the URL is prefixed with http:// or https://. HTTP scripts themselves are safe to run as a result of our sandboxing, with one notable pitfall, as mentioned above.
Usage
# Replace a fixed string with another string:
npx tweakcc adhoc-patch --string '"Claude Code"' '"My App"'
# Replace all CSS-style RGB colors with bright red:
npx tweakcc adhoc-patch --regex 'rgb\(\d+,\d+,\d+\)' 'rgb(255,0,0)'
# Erase all of CC's code and replace it with a simple console.log:
npx tweakcc adhoc-patch --script $'return "(function(){console.log(\"Hi\")})()"'
# Run a script from a local file:
npx tweakcc adhoc-patch --script '@path/to/script.js'
# Run a script from an HTTP URL (warning: this script makes everything in CC blue and changes "Claude Code" to "ABC Code CLI", which BREAKS CC):
# Its contents are:
#
# js = js.replace(/Claude Code/g, "ABC Code CLI")
# js = js.replace(/rgb\(\d+,\d+,\d+\)/g, "rgb(0,128,255)")
# return js
#
npx tweakcc adhoc-patch --script '@https://gist.githubusercontent.com/bl-ue/2402a16b966176c994ea7bd5d11b0b09/raw/eeb0b78a6387f0e6a15182eeabd95f0e84e4ccd7/patch_cc.js'
Here’s a demo of adhoc-patch using a script from an HTTP URL (link to Gist):
https://github.com/user-attachments/assets/221ce577-933e-41d9-ae14-88ce5457a321
adhoc-patch does not create a backup of the Claude Code installation that is modified. You’ll need to use --apply first to get a backup created if you want to be able to use --restore/--revert after an adhoc-patch.
API
tweakcc can be used as an npm dependency and provides an easy API that projects can use to patch Claude Code without worrying about where it’s installed and whether it’s native or npm-based. The functions are divided into 5 groups: config, installation, I/O, backup, and utilities.
Config • Functions to access tweakcc's own config, if it exists on the machine.
/**
* Returns the absolute path to tweakcc's config dir. By default it's
* `~/.tweakcc` but it also can use `~/.claude/tweakcc` and it also respects
* `XDG_CONFIG_HOME`—see [Configuration Directory](#configuration-directory).
*/
function getTweakccConfigDir(): string;
/**
* Returns the absolute path to tweakcc's config file. It's named `config.json`
* and lives in the config dir as returned by `getTweakccConfigDir`.
*/
function getTweakccConfigPath(): string;
/**
* Returns the absolute path to the directory containing the user-editable
* system prompt markdown files. It's named `system-prompts/` and lives in the
* config dir.
*/
function getTweakccSystemPromptsDir(): string;
/**
* Reads and returns the tweakcc config (as determined by `getTweakccConfigDir`).
*/
function readTweakccConfig(): Promise<TweakccConfig | null>;
Demo:
> tweakcc.getTweakccConfigDir()
'/home/user/.tweakcc'
> tweakcc.getTweakccConfigPath()
'/home/user/.tweakcc/config.json'
> tweakcc.getTweakccSystemPromptsDir()
'/home/user/.tweakcc/system-prompts'
> await tweakcc.readTweakccConfig()
{
ccVersion: '2.1.32',
ccInstallationPath: '/home/user/.local/bin/claude',
lastModified: '2026-02-05T21:18:48.551Z',
changesApplied: true,
settings: { ... }
}
Installation • Utilities to find installed versions of Claude Code.
/**
* Finds all Claude Code installations on the machine via `$PATH` and hard-coded
* search directories.
*/
async function findAllInstallations(): Promise<Installation[]>;
/**
* Prompts the user to select one of the specified Claude Code installations
* interactively using the same UI tweakcc uses, powered by [Ink + React](https://github.com/vadimdemedes/ink).
*/
async function showInteractiveInstallationPicker(
candidates: Installation[]
): Promise<Installation | null>;
/**
* Attempts to detect the user's preferred Claude Code installation. Detection procedure:
* 0. options.path
* 1. Uses $TWEAKCC_CC_INSTALLATION_PATH if set.
* 2. Uses ccInstallationPath in tweakcc config.
* 3. Discovers installation from `claude` in PATH
* 4. Looks in hard-coded search paths:
* a. If the search yields one installation, uses it
* b. If it yields multiple and options.interactive is true, display a picker
* via showInteractiveInstallationPicker().
*/
async function tryDetectInstallation(
options: DetectInstallationOptions = {}
): Promise<Installation>;
Demo:
> const insts = await tweakcc.findAllInstallations()
[
{
path: 'C:\\Users\\user\\.local\\share\\claude\\versions\\2.0.60',
version: '2.0.60',
kind: 'native'
},
{
path: 'C:\\Users\\user\\.local\\share\\claude\\versions\\2.0.76',
version: '2.0.76',
kind: 'native'
},
{
path: 'C:\\Users\\user\\AppData\\Local\\Volta\\tools\\image\\packages\\@anthropic-ai\\claude-code\\node_modules\\@anthropic-ai\\claude-code\\cli.js',
version: '2.1.32',
kind: 'npm'
}
]
> await tweakcc.tryDetectInstallation()
{
path: 'C:\\Users\\user\\AppData\\Local\\Volta\\tools\\image\\packages\\@anthropic-ai\\claude-code\\node_modules\\@anthropic-ai\\claude-code\\cli.js',
version: '2.1.32',
kind: 'npm'
}
> await tweakcc.showInteractiveInstallationPicker(insts)
No claude executable was found in PATH, but multiple Claude Code installations were found on this machine. Please select one:
❯ C:\Users\user\.local\share\claude\versions\2.0.60 (native-binary, v2.0.60)
C:\Users\user\.local\share\claude\versions\2.0.76 (native-binary, v2.0.76)
C:\Users\user\AppData\Local\Volta\tools\image\packages\@anthropic-ai\claude-code\node_modules\@anthropic-ai\claude-code\cli.js (npm-based, v2.1.32)
Your choice will be saved to ccInstallationPath in ~\.tweakcc/config.json.
Use ↑↓ arrows to navigate, Enter to select, Esc to quit
I/O • Functions to read and write the content of an npm-based or native (Bun-based) installation.
/**
* Read Claude Code's JavaScript content.
*
* - npm installs: reads cli.js directly
* - native installs: extracts embedded JS from binary
*/
async function readContent(installation: Installation): Promise<string>;
/**
* Write modified JavaScript content back to Claude Code.
*
* - npm installs: writes to cli.js (handles permissions, hard links)
* - native installs: repacks JS into binary
*/
async function writeContent(
installation: Installation,
content: string
): Promise<void>;
Demo:
> const native2076Inst = { path: 'C:\\Users\\user\\.local\\share\\claude\\versions\\2.0.76', kind: 'native' };
> let content = await tweakcc.readContent(native2076Inst);
> content.length
10639722
> content.slice(4153122, 4153122+236)
"var be$=\"You are Claude Code, Anthropic's official CLI for Claude.\",UBD=\"You are Claude Code, Anthropic's official CLI for Claude, running within the Claude Agent SDK.\",GBD=\"You are a Claude agent, built on Anthropic's Claude Agent SDK.\""
> content = content.replace(/Claude Code/g, 'My App')
> content = content.replace(/Anthropic(?: PBC)?/g, 'My Corp')
> await tweakcc.writeContent(native2076Inst, content)
undefined
> (await tweakcc.readContent(native2076Inst)).slice(4153122+16, 4153122+172)
"var be$=\"You are My App, My Corp's official CLI for Claude.\",UBD=\"You are My App, My Corp's official CLI for Claude, running within the Claude Agent SDK.\",GBD=\"You are a Claude agent, built on My Corp's Claude Agent SDK.\""
Backup • Simple utilities to handle creating and restoring backups of the native binary or `cli.js` in order to revert patches.
/**
* Backup a file to a specified location, creating parent directories if needed.
* Leaves the original file untouched.
*/
async function backupFile(
sourcePath: string,
backupPath: string
): Promise<void>;
/**
* Restore a file from a backup, breaking hard links, which are common with pnpm/bun
* installations, and preserving execute permissions.
*/
async function restoreBackup(
backupPath: string,
targetPath: string
): Promise<void>;
Demo:
> const native2076Inst = { path: 'C:\\Users\\user\\.local\\share\\claude\\versions\\2.0.76', kind: 'native' };
> const backupPath = path.join(os.homedir(), ".myapp", `cc-${native2076Inst.kind}-backup`);
> await tweakcc.backupFile(native2076Inst.path, backupPath);
undefined
> fs.statSync(backupPath).size
234454688
> await tweakcc.writeContent(native2076Inst, "(function(){console.log(\"Hi\")})");
> (await tweakcc.readContent(native2076Inst)).length
31
> await tweakcc.restoreBackup(backupPath, native2076Inst.path)
> (await tweakcc.readContent(native2076Inst)).length
234454688
Utilities • General utilities to help with patching.
findChalkVar(fileContents: string): string | undefined;
getModuleLoaderFunction(fileContents: string): string | undefined;
getReactVar(fileContents: string): string | undefined;
getRequireFuncName(fileContents: string): string | undefined;
findTextComponent(fileContents: string): string | undefined;
findBoxComponent(fileContents: string): string | undefined;
clearCaches(): void;
export const showDiff = (
oldFileContents: string,
newFileContents: string,
injectedText: string,
startIndex: number,
endIndex: number,
numContextChars: number = 40
): void;
export const globalReplace = (
content: string,
pattern: RegExp,
replacement: string | ((substring: string, ...args: unknown[]) => string)
): string;
Demo of showDiff:
const pattern = /function [$\w]+\(\)\{return [$\w]+\("my_feature_flag"/;
const match = file.match(pattern)!;
const insertIndex = match.index + match[0].indexOf('{') + 1;
const insertion = 'return true;';
const newFile = file.slice(0, insertIndex) + insertion + file.slice(insertIndex);
showDiff(file, newFile, insertion, insertIndex, insertIndex);
Demo of globalReplace:
newFile = globalReplace(newFile, /"Claude Code",/g, '"My App"');
System prompts
tweakcc allows you to customize the various parts of Claude Code’s system prompt, including
- the main system prompt and any conditional bits,
- descriptions for all 17 builtin tools like
Bash, TodoWrite, Read, etc.,
- prompts for builtin Task/Plan/Explore subagents, and
- prompts for utilities such as conversation compaction, WebFetch summarization, Bash command analysis, CLAUDE.md/output style/statusline creation, and many more.
👉 See Claude Code System Prompts for a breakdown of all the system prompt parts, as well as a changelog and diffs for each CC version.
Because the system prompt is dynamically composed based on several factors, it’s not one string that can be simply modified in a text editor. It’s a bunch of smaller strings sprinkled throughout Claude Code’s source code.
tweakcc’s method for modifying the system prompts involves maintaining one markdown file for each individual portion of the prompt, resulting in a file for each tool description, each agent/utility prompt, and one for the main system prompt and a few more for various large notes inserted into other prompt parts.
How the prompt files are created
When tweakcc starts up, it downloads a list of system prompt parts for your Claude Code installation from GitHub (the data/prompts folder in the tweakcc repo). It then checks if each prompt part has a corresponding markdown file on disk, creating ones that don’t exist and populating them with the default text for the version.
:star: To customize any part of the system prompt, simply edit the markdown files in ~/.tweakcc/system-prompts (or $XDG_CONFIG_HOME/tweakcc/system-prompts) and then run npx tweakcc --apply.
Claude Code does not send every part to every model. On recent models it uses a short “lean” main prompt: the Harness instructions part replaces the System section, Doing tasks, Executing actions with care, Tone and style and Communication style parts, so edits to those have no effect there. To get the full main prompt back, start Claude Code with CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT=0.
What happens when Anthropic changes the prompts?
When your Claude Code installation is updated, tweakcc will automatically update all of your markdown files that correspond to parts of the system prompt that were changed in the new version, unless you’ve modified any of them. But if you did modify ones that Anthropic has also modified, then tweakcc will leave the ones you modified unchanged, and rely on you to resolve the conflict.
To assist you with resolving the conflicts, tweakcc will generate an HTML file that shows on the left, the diff of the change you’ve made, and on the right, the diff of Anthropic’s changes. That way you can recall at a glance what you’ve changed in the prompt, and easily see what’s changed in the new prompt. Then you can modify the markdown file for the prompt, incorporate or ignore new changes as you see fit.
Make sure to update the ccVersion field at the top of the file when you’re done resolving the conflicts. If you don’t, tweakcc won’t know that you’ve resolved the conflicts and will continue to report conflicts and generate the HTML diff file. Important: Also note that the version you update ccVersion to is not necessarily the new version of CC that you installed; rather, it’s the most recent version this particular system prompt was updated in. Different prompt files have different most-recently-modified versions.
Screenshot of the HTML file:
Git for version control over your customized prompts
This is a great idea, and we recommend it; in fact, we have one ourselves here. It allows you to keep your modified prompt safe in GitHub or elsewhere, and you can also switch from one set of prompts to another via branches, for example. In the future we plan to integrate git repo management for the system prompt markdown files into tweakcc. For now you’ll need to manually initialize a git repository in ~/.tweakcc directory. tweakcc automatically generates a recommended .gitignore file in that directory (which you can modify if you’d like).
Toolsets are collections of built-in tools that Claude is allowed to call. Unlike Claude Code’s builtin permission system, however, built-in tools that are not in the currently active toolset are not even sent to the model. As a result, Claude has no idea of tools that are not enabled in the current toolset (unless they happen to be mentioned in other parts of the system prompt), and it’s not able to call them.
Toolsets can be helpful both for using Claude in different modes, e.g. a research mode where you might only include WebFetch and WebSearch, and for reducing the size of your system prompt by trimming out tools you don’t ever want Claude to call. The description of each tool call is placed in the system prompt (see here), and if there are multiple tools you don’t care about (like Skill, SlashCommand, BashOutput, etc.), the accumulated size of their descriptions and parameters can bloat the context by several thousand tokens.
To create a toolset, run npx tweakcc, go to Toolsets, and hit n to create a new toolset. Set a name and enable/disable some tools, run tweakcc --apply to apply your customizations, and then run claude. If you marked a toolset as the default in tweakcc, it will be automatically selected.
- Mode bindings. In the
Toolsets menu, d, a and p bind a toolset to the default, accept-edits and plan modes. The toolset for the mode Claude Code starts in applies at startup. Shift+Tab switches to the toolset bound to the new mode.
- Override at startup. Set
TWEAKCC_TOOLSET_DEFAULT, TWEAKCC_TOOLSET_ALLOW_EDITS, TWEAKCC_TOOLSET_PLAN or TWEAKCC_TOOLSET_AUTO to a toolset name. These override the bindings from the menu for that run. No re-apply is needed.
- Switch in a session.
/toolset <name> switches toolsets. /toolset default or /toolset none clears the choice and goes back to the mode binding (unless you have a toolset with that name).
- MCP tools. An entry ending in
* matches by prefix. Pick mcp__* in the toolset editor to allow every MCP tool. For one server, add an entry such as mcp__github__* to the toolset’s allowedTools in config.json.
- If Claude calls a tool that is not in the active toolset, the error names the toolset and lists the tools it allows.
Feature: Thinking verbs customization
Customize the thinking verbs that appear while Claude is generating responses, along with the format string. You can change from the default "Thinking… " format to something more fun like "Claude is {verb}ing..." or anything else you prefer.
Here’s a demo showing a custom thinking verb format in action:
To customize thinking verbs, you can use the tweakcc UI or edit ~/.tweakcc/config.json manually.
Via the UI:
- Run
npx tweakcc
- Navigate to the “Thinking verbs” section
- Use the tab key to switch between Format and Verbs sections
- Edit the format string: the
{} placeholder will be replaced with a randomly selected verb
- Add, edit, or remove verbs from the list
- Apply changes when satisfied
Via config.json:
In .settings.thinkingVerbs, configure the format and verbs:
"thinkingVerbs": {
"format": "{}… ",
"verbs": [
"Accomplishing",
"Baking",
"Cogitating",
"Fermenting",
"Moonwalking",
"Noodling"
]
}
Here’s the schema:
{
format: string; // Format string, use {} as placeholder for the verb
verbs: string[]; // Array of verbs (Claude randomly selects one)
}
Examples of different formats:
- Default format:
"{}… " → displays as "Thinking… "
- Custom format:
"Claude is {verb}ing..." → displays as "Claude is Baking..."
- Custom format:
"✻ {verb} (generating)" → displays as "✻ Baking (generating)"
- Custom format:
"<{verb}> " → displays as "<Baking> "
Reset to defaults:
To reset to the default verbs and format, run npx tweakcc, navigate to Thinking verbs, and press Ctrl+R to restore defaults (which include 200+ fun verbs like “Beboppin’”, “Fermenting”, “Moonwalking”, etc.).
Feature: Thinking indicator customizations
Customize the thinking indicator (spinner) animation that appears alongside the thinking verb. You can change the animation phases, speed, and whether it reverses direction.
The thinking indicator consists of a sequence of characters that cycle through while Claude is thinking, displayed alongside the thinking verb (e.g., Thinking· → Thinking✢ → Thinking✳ → etc.).
Via config.json:
In .settings.thinkingStyle, configure the animation:
"thinkingStyle": {
"updateInterval": 120,
"phases": [
"·",
"✢",
"✳",
"✶",
"✻",
"✽"
],
"reverseMirror": true
}
Here’s the schema:
{
updateInterval: number; // Animation speed in milliseconds (lower = faster)
phases: string[]; // Array of characters that cycle through
reverseMirror: boolean; // Whether to reverse the animation sequence
}
Examples of different animations:
| Animation |
Phases |
Description |
| Default stars |
['·', '✢', '✳', '✶', '✻', '✽'] |
Classic star burst animation |
| Simple dots |
['.', '..', '...'] |
Classic loading dots |
| Braille spinner |
['⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'] |
Braille-style spinner |
| Arrow spinner |
['←', '↖', '↑', '↗', '→', '↘', '↓', '↙'] |
Rotating arrow |
| Minimal |
['○', '◐', '◑', '●'] |
Minimal circle animation |
Speed customization:
updateInterval: 60 → Very fast animation (60ms per phase)updateInterval: 120 → Default speed (120ms per phase)updateInterval: 250 → Slower animation (250ms per phase)
For a few weeks, when you typed the word “ultrathink” into the Claude Code input box, it would be highlighted rainbow. That’s gone now, but the underlying highlighting infrastructure is still present in Claude Code today, and tweakcc lets you specify custom highlighters comprised of a regular expression, format string, and colors & styling.
Here’s a demo where every word is assigned a different color based on its first letter:
Here’s one where various common patterns like environment variables, file paths, numbers, and markdown constructs are highlighted:
Finally, here’s one showing how you can render extra characters that aren’t really part of the prompt by customizing the format string. The first line shows a copy of what I’ve actually got typed into the prompt, and in the prompt itself you can see that cluade was visually (but not in reality) replaced with Claude Code, ..., etc.
To add some patterns, you can use the tweakcc UI or edit ~/.tweakcc/config.json manually.
Via the UI:
| Listing |
Edit |
 |
 |
Via config.json:
In .settings.inputPatternHighlighters (an array), add a new object:
"inputPatternHighlighters": [
...
{
"name": "File path",
"regex": "(?:[a-zA-Z]:)?[/\\\\]?[a-zA-Z0-9._\\-]+(?:[/\\\\][a-zA-Z0-9._\\-]+)+",
"regexFlags": "g",
"format": "{MATCH}",
"styling": [
"bold"
],
"foregroundColor": "rgb(71,194,10)",
"backgroundColor": null,
"enabled": true
},
]
Here’s the schema for the object format:
{
name: string; // User-friendly name
regex: string; // Regex pattern (stored as string)
regexFlags: string; // Flags for the regex, must include 'g' for matchAll
format: string; // Format string, use {MATCH} as placeholder
styling: string[]; // ['bold', 'italic', 'underline', 'strikethrough', 'inverse']
foregroundColor: string | null; // null = don't specify, otherwise rgb(r,g,b)
backgroundColor: string | null; // null = don't specify, otherwise rgb(r,g,b)
enabled: boolean; // Temporarily disable this pattern
}
Feature: Opus Plan 1M mode
tweakcc adds support for a new model alias: opusplan[1m]. This combines the best of both worlds:
- Plan mode: Uses Opus 4.5 for complex reasoning and architecture decisions
- Execution mode: Uses Sonnet 4.5 with 1M context for code generation
Why use this?
Claude Sonnet 4.5 is aware of its context window, so when it gets close to full, the model exhibits context anxiety, where it thinks there may not be enough context to complete the given task, so it takes shortcuts or leaves subtasks incomplete.
By using the 1M context model, Claude thinks it has plenty of room and doesn’t skip things, and as long as you ensure you stay under 200k tokens you’ll be charged the normal input/output rates even though you’re using the 1M model. However, once you exceed 200k tokens when using the 1M model, you’ll be automatically charged premium rates (2x for input tokens and 1.5x for output tokens)—see the 1M context window docs.
How to use it
After applying tweakcc patches, you can use opusplan[1m] like any other model alias:
# Via CLI flag
claude --model opusplan[1m]
# Or set it permanently via /model command in Claude Code
/model opusplan[1m]
| Mode |
Model Used |
Context Window |
| Plan mode (Shift+Tab twice) |
Opus 4.5 |
200k |
| Execution mode (default) |
Sonnet 4.5 |
1M |
Feature: MCP startup optimization
If you use multiple MCP servers, Claude Code’s startup can be slow—waiting 10-15+ seconds for all servers to connect before you can start typing.
tweakcc fixes this with two optimizations (based on this blog post):
- Non-blocking MCP connections (enabled by default): Start typing immediately while MCP servers connect in the background
- Configurable batch size: Connect more servers in parallel (default: 3, configurable from 1-20)
Results
| Configuration |
Startup Time |
Improvement |
| Default Claude Code |
~15s |
— |
| With non-blocking |
~7s |
~50% faster |
Configuration
Via the UI: Run npx tweakcc, go to Misc, and adjust:
- Non-blocking MCP startup — Toggle on/off (default: on)
- MCP server batch size — Use ←/→ arrows to adjust (1-20)
Via config.json:
{
"settings": {
"misc": {
"mcpConnectionNonBlocking": true,
"mcpServerBatchSize": 8
}
}
}
| Setting |
Default |
Description |
mcpConnectionNonBlocking |
true |
Start immediately, connect MCPs in background |
mcpServerBatchSize |
null (uses CC’s default of 3) |
Number of parallel MCP connections (1-20) |
Recent Claude Code versions render tables using Unicode box-drawing characters. While these have a more elegant look compared to the traditional plain markdown table rendering, they take up more room due to the row dividers:
default — Original box-drawing with all row separators:
┌───────────┬───────────────────────────────┬───────┐
│ Library │ Purpose │ Size │
├───────────┼───────────────────────────────┼───────┤
│ React │ UI components, virtual DOM │ ~40kb │
├───────────┼───────────────────────────────┼───────┤
│ Vue │ Progressive framework │ ~34kb │
├───────────┼───────────────────────────────┼───────┤
│ Svelte │ Compile-time framework │ ~2kb │
└───────────┴───────────────────────────────┴───────┘
tweakcc provides three alternative formats:
ascii — ASCII/Markdown style using | and - (easy to copy-paste):
| Library | Purpose | Size |
|-----------|-------------------------------|-------|
| React | UI components, virtual DOM | ~40kb |
| Vue | Progressive framework | ~34kb |
| Svelte | Compile-time framework | ~2kb |
clean — Box-drawing without top/bottom borders or row separators:
│ Library │ Purpose │ Size │
├───────────┼───────────────────────────────┼───────┤
│ React │ UI components, virtual DOM │ ~40kb │
│ Vue │ Progressive framework │ ~34kb │
│ Svelte │ Compile-time framework │ ~2kb │
clean-top-bottom — Box-drawing with top/bottom borders but no row separators:
┌───────────┬───────────────────────────────┬───────┐
│ Library │ Purpose │ Size │
├───────────┼───────────────────────────────┼───────┤
│ React │ UI components, virtual DOM │ ~40kb │
│ Vue │ Progressive framework │ ~34kb │
│ Svelte │ Compile-time framework │ ~2kb │
└───────────┴───────────────────────────────┴───────┘
Via the UI: Run npx tweakcc, go to Misc, and cycle through the Table format options with spacebar. Then apply your customizations.
Via config.json:
{
"settings": {
"misc": {
"tableFormat": "ascii"
}
}
}
Valid values are "default", "ascii", "clean", and "clean-top-bottom".
Feature: Token count rounding
In the generation status, where the thinking verb is displayed, e.g. ✻ Improvising… (35s · ↓ 279 tokens), the token count estimate will increase very rapidly at times. While it’s helpful to know that the connection isn’t stalled, such frequent UI updates can cause rendering issues in slow terminals, and if Claude Code is being run from a network, frequent updates can clog the network.
tweakcc can automatically round the token counters to the nearest multiple of a custom base number. For example, here are two demo clips showing the token count rounded to multiples of 50, and multiples of 1000:
| Description |
GIF |
| Multiples of 50 |
 |
| Multiples of 1000 |
 |
Configuration via UI: Go to Misc → Token count rounding towards the bottom.
Configuration via config.json: While the tweakcc UI only allows common values like 10, 25, 500, 1000, etc., you can use any integer value for the setting itself in config.json. Open ~/.tweakcc/config.json and set the settings.misc.tokenCountRounding field to your desired rounding base:
{
"settings": {
"misc": {
"tokenCountRounding": 123
}
}
}
Now token counts will be rounded to the nearest multiple of 123, e.g. 123, 246, 369, etc.
Feature: Statusline update customization
Claude Code’s statusline feature operates by running a specific command (e.g. a shell script) whenever the conversation history changes (i.e., a message is added), capturing the command’s output—including ANSI escape codes for coloring—and rendering it in Claude Code under the input box.
It’s neat functionality but the updates occur at what appear to be sporadic intervals. According to the docs, “Updates run at most every 300 ms,” but this is inaccurate—technically, updates are queued for 300 milliseconds, meaning an update is triggered each time the chat history is updated, but is then delayed before execution for 300ms.
In the majority of cases, this behavior is fine. However, if you have a specialized use case, you may need updates to be throttled at 300ms like the documentation states, or even have updates automatically triggered at a specific interval.
tweakcc can patch Claude Code to correct this erratic queuing behavior, making it properly throttle updates at a customizable interval. It can also pace the updating, making it be performed at a regular interval, independent of changes to the chat history.
Here are two demos showing 1) updates triggered every 150ms, and 2) updates triggered by history updates, throttled at 1s. The update = X is a custom statusline, where X increments each time the statusline is re-rendered.
| 150ms interval |
1000ms throttling |
 |
 |
Configuration via UI: Go to Misc → Statusline throttle
Configuration via config.json: While the tweakcc UI only allows increments of 50ms for the statusline update interval, you can use any integer value for it by editing config.json. Open ~/.tweakcc/config.json and set the settings.misc.statuslineThrottleMs field to your desired interval, and set settings.misc.statuslineUseFixedInterval to true for a fixed-pace interval or false for throttling.
{
"settings": {
"misc": {
"statuslineThrottleMs": 500,
"statuslineUseFixedInterval": false
}
}
}
Supported Claude Code versions: 1.0.24 (and likely older) to 2.1.32+.
Claude Code is the only coding agent that doesn’t support AGENTS.md; it only supports CLAUDE.md and CLAUDE.local.md. (This issue has over 2200 upvotes.) tweakcc automatically patches Claude Code to fall back to AGENTS.md and several others when CLAUDE.md doesn’t exist.
The patch happens automatically, with a default set of AGENTS.md, GEMINI.md, CRUSH.md, QWEN.md, IFLOW.md, WARP.md, and copilot-instructions.md—you don’t need to configure it specifically. However, if you’d like to support other file names, you can do so easily:
Via UI: Run npx tweakcc@latest and go to CLAUDE.md alternate names. Use e to edit a name, d to delete one, n to add a new one, u/j to move one up/down, and ctrl + r to reset to the default list mentioned above:
Via config.json: To configure the list of alternate CLAUDE.md names headlessly, set settings.claudeMdAltNames to a list of your desired names, in descending order of priority:
{
"settings": {
"claudeMdAltNames": ["AGENTS.md", "context.md"]
}
}
Note that CLAUDE.md is always used above all alternatives when it’s available, so it’s not required to include it in the list.
Here’s a demo video of AGENTS.md working:
https://github.com/user-attachments/assets/27513489-bb89-4174-b62f-ab17b0fce7bd
Feature: Bypass permissions check in sudo
⚠️ Warning: This feature disables a security check. Only enable it if you understand the implications.
By default, Claude Code prevents the use of --dangerously-skip-permissions when running under sudo to avoid accidental system-wide permission bypasses. This patch removes that restriction.
Why you might need this: Some system administration tasks or automated deployment scripts may require running Claude Code with elevated privileges while also bypassing permission checks. For example, when deploying to restricted directories or modifying system configuration files.
Security implications: When enabled, you can run Claude Code with sudo and bypass permission checks, potentially allowing Claude to perform system-level operations without prompts. Use extreme caution.
Via the UI: Run npx tweakcc, go to Misc, and toggle Allow bypass permissions in sudo.
Via config.json:
{
"settings": {
"misc": {
"allowBypassPermissionsInSudo": true
}
}
}
Usage:
sudo claude --dangerously-skip-permissions
Feature: Auto-accept plan mode
Supported Claude Code versions: 2.1.22 to 2.1.32+.
When Claude finishes writing a plan and calls ExitPlanMode, you’re normally shown a “Ready to code?” dialog with options to approve or continue editing. This patch automatically selects “Yes, clear context and auto-accept edits” without requiring user interaction.
Via UI: Run npx tweakcc@latest and navigate to Miscellaneous Settings. Scroll down to find Auto-accept plan mode and press space to enable it.
Via config.json: Set settings.misc.autoAcceptPlanMode to true:
{
"settings": {
"misc": {
"autoAcceptPlanMode": true
}
}
}
To auto-accept only for some runs, leave autoAcceptPlanMode off and set settings.misc.autoAcceptPlanModeEnv to true (UI: Auto-accept plan mode via env). Plans are then auto-accepted only when Claude Code starts with TWEAKCC_AUTO_ACCEPT_PLAN=1, e.g. TWEAKCC_AUTO_ACCEPT_PLAN=1 claude --permission-mode plan. Without the variable the normal dialog is shown.
Feature: Suppress native installer warning
When Claude Code detects that you’ve installed via npm, it warns you to use the native installer.
Via the UI: Run npx tweakcc, go to Misc, and toggle Suppress native installer warning.
Via config.json:
{
"settings": {
"misc": {
"suppressNativeInstallerWarning": true
}
}
}
Some terminals may experience unwanted scrolling behavior caused by certain cursor positioning escape sequences (e.g., \x1b[H and \x1b[A). This patch filters out these problematic escape sequences from Claude Code’s output to prevent scrolling issues.
Via the UI: Run npx tweakcc, go to Misc, and toggle Filter scroll escape sequences.
Via config.json:
{
"settings": {
"misc": {
"filterScrollEscapeSequences": true
}
}
}
Feature: WebFetch Use
README 内容过长，已截取前 64 KB。完整内容请前往 GitHub 仓库查看。
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