Patch Creation & Registration

Overview

Patches are code modifications applied to Claude Code's

cli.js

Creating a New Patch

1. Create the patch file

Create

src/patches/myPatch.ts

// Please see the note about writing patches in ./index

import { showDiff } from './index';

/**
 * Description of what this patch does.
 *
 * CC X.Y.Z:
 * ```diff
 *  // Show before/after of the code change
 * -oldCode
 * +newCode
 * ```
 */
export const writeMyPatch = (
  file: string,
  configValue: string // Add parameters as needed
): string | null => {
  // Pattern to find in minified code
  // IMPORTANT: Use [$\w]+ for identifiers (not \w+) because $ is valid in JS identifiers
  // IMPORTANT: Start patterns with a boundary char (,;}{) for HIGH performance (e.g. 1.5s -> 30ms)
  const pattern = /,somePattern([$\w]+)/;

  const match = file.match(pattern);

  if (!match || match.index === undefined) {
    console.error('patch: myPatch: failed to find pattern');
    return null;
  }

  const replacement = `,newCode${match[1]}`;

  const startIndex = match.index;
  const endIndex = startIndex + match[0].length;

  const newFile =
    file.slice(0, startIndex) + replacement + file.slice(endIndex);

  showDiff(file, newFile, replacement, startIndex, endIndex);

  return newFile;
};

2. Add config type (if patch is configurable)

Edit

src/types.ts

MiscConfig

export interface MiscConfig {
  // ... existing fields ...
  myNewSetting: string | null; // null = disabled
}

3. Add default value

Edit

src/defaultSettings.ts

misc: {
  // ... existing fields ...
  myNewSetting: null,  // or a sensible default
},

4. Register in index.ts

Edit

src/patches/index.ts

4a. Add import:

import { writeMyPatch } from './myPatch';

4b. Add patch definition (in

PATCH_DEFINITIONS

{
  id: 'my-patch',
  name: 'My patch',
  group: PatchGroup.FEATURES,  // or ALWAYS_APPLIED, MISC_CONFIGURABLE
  description: 'What this patch does for the user',
},

4c. Add patch implementation (in

patchImplementations

'my-patch': {
  fn: c => writeMyPatch(c, config.settings.misc!.myNewSetting!),
  condition: !!config.settings.misc?.myNewSetting,
},

5. Add UI (optional)

Edit

src/ui/components/MiscView.tsx

Key Files

src/patches/*.ts

src/patches/index.ts

src/types.ts

MiscConfig

src/defaultSettings.ts

src/ui/components/MiscView.tsx

Registration Checklist

When adding a new patch, update these locations:

• src/patches/myPatch.ts

  - Create the patch file with exported function

• src/types.ts

  - Add config type (if configurable)

• src/defaultSettings.ts

  - Add default value (if configurable)

• src/patches/index.ts

  :
  • Import the patch function
  • Add to

    PATCH_DEFINITIONS

    array (id, name, group, description)
  • Add to

    patchImplementations

    object (fn, condition)

• src/ui/components/MiscView.tsx

  - Add UI controls (optional)

Patch Groups

• PatchGroup.ALWAYS_APPLIED

  - Core patches that are always applied

• PatchGroup.MISC_CONFIGURABLE

  - User-configurable misc settings

• PatchGroup.FEATURES

  - Feature patches that can be enabled/disabled

Pattern Writing Tips

1. Use

   [$\w]+

   for identifiers - Not

   \w+

   , because

   $

   is valid in JS identifiers and common in minified code

2. Start patterns with boundary characters - Use

   ,

   ,

   ;

   ,

   {

   ,

   }

   at the start to dramatically speed up matching (can reduce 1.5s to 30ms)

3. Don't use

   \b

   for word boundaries - It doesn't treat

   $

   as a word character, so

   \b[$\w]+

   won't match

   ,$=

4. Extract function bodies carefully - Count braces to find matching

   }

   when you need the full function

5. Use

   showDiff()

   for debugging - Always call it to log what the patch is changing

6. Return

   null

   on failure - Let the patch system know the patch couldn't be applied

7. Handle multiple CC versions - Code patterns may change between versions; try multiple patterns if needed

Example: Simple Toggle Patch

// Bypass a feature flag check
const pattern = /function [$\w]+\(\)\{return [$\w]+\("my_feature_flag"/;
const match = file.match(pattern);

if (!match || match.index === undefined) {
  console.error('patch: myPatch: failed to find feature flag');
  return null;
}

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);
return newFile;

Example: Replace a Value

// Replace a hardcoded value
const pattern = /(someConfig=)\d+(;)/;
const match = file.match(pattern);

if (!match || match.index === undefined) {
  console.error('patch: myPatch: failed to find config value');
  return null;
}

const replacement = match[1] + newValue + match[2];
const startIndex = match.index;
const endIndex = startIndex + match[0].length;

const newFile = file.slice(0, startIndex) + replacement + file.slice(endIndex);

showDiff(file, newFile, replacement, startIndex, endIndex);
return newFile;

Testing

1. Run

   npm run build

   to compile
2. Run

   npx tweakcc --apply

   to apply patches
3. Check console output for patch success/failure
4. Run Claude Code to verify behavior