Add patch to prevent updates to unsupported versions

src/defaultSettings.ts

@@ -755,6 +755,7 @@ export const DEFAULT_SETTINGS: Settings = {
     increaseFileReadLimit: false,
     suppressLineNumbers: true,
     suppressRateLimitOptions: false,
+    preventUpdateToUnsupportedVersions: false,
   },
   toolsets: [],
   defaultToolset: null,

src/patches/index.ts

@@ -70,6 +70,7 @@ import {
   restoreClijsFromBackup,
 } from '../installationBackup';
 import { compareVersions } from '../systemPromptSync';
+import { writePreventUnsupportedUpdates } from './preventUnsupportedUpdates';
 
 export interface LocationResult {
   startIndex: number;
@@ -736,6 +737,11 @@ export const applyCustomization = async (
     if ((result = writeSuppressRateLimitOptions(content))) content = result;
   }
 
+  // Apply prevent update to unsupported versions patch (if enabled)
+  if (config.settings.misc?.preventUpdateToUnsupportedVersions) {
+    if ((result = writePreventUnsupportedUpdates(content))) content = result;
+  }
+
   // Write the modified content back
   if (ccInstInfo.nativeInstallationPath) {
     // For native installations: repack the modified claude.js back into the binary

src/patches/preventUnsupportedUpdates.ts

@@ -0,0 +1,136 @@
+// Please see the note about writing patches in ./index
+//
+// This patch prevents Claude Code from auto-updating to versions that tweakcc
+// doesn't yet support. It works by checking if the prompts file exists on GitHub
+// for the target version before allowing the update.
+
+import { LocationResult, showDiff } from './index';
+
+/**
+ * Finds the location in the auto-updater where the latest version is fetched
+ * and the update decision is made.
+ *
+ * The pattern we're looking for (minified):
+ *   BUILD_TIME:"..."}.VERSION,CHANNEL_VAR=hq()?.autoUpdatesChannel??"latest",VERSION_VAR=await FUNC(CHANNEL_VAR),OTHER_VAR=FUNC2();
+ *
+ * We'll inject code after VERSION_VAR assignment to check if it's supported.
+ */
+const getAutoUpdaterLocation = (oldFile: string): LocationResult | null => {
+  // Pattern to match the auto-updater version fetch in minified code
+  // The key markers are:
+  // - BUILD_TIME:"..." followed by }.VERSION,
+  // - hq()?.autoUpdatesChannel??"latest"
+  // - await FUNC(VAR) pattern
+  // Captures: [1]=channel var, [2]=version var, [3]=fetch function, [4]=next var, [5]=next func
+  const pattern =
+    /BUILD_TIME:"[^"]+"\}\.VERSION,([$\w]+)=hq\(\)\?\.autoUpdatesChannel\?\?"latest",([$\w]+)=await ([$\w]+)\(\1\),([$\w]+)=([$\w]+)\(\);/;
+
+  const match = oldFile.match(pattern);
+
+  if (!match || match.index === undefined) {
+    console.error(
+      'patch: preventUnsupportedUpdates: failed to find auto-updater pattern'
+    );
+    return null;
+  }
+
+  return {
+    startIndex: match.index,
+    endIndex: match.index + match[0].length,
+    identifiers: [
+      match[0], // Full match
+      match[1], // channel var (e.g., _)
+      match[2], // version var (e.g., Z)
+      match[3], // fetch function (e.g., _t)
+      match[4], // next var (e.g., G)
+      match[5], // next var's function (e.g., Ed)
+    ],
+  };
+};
+
+/**
+ * Gets the variable name used for the current version.
+ * This is typically $ in the code pattern:
+ *   let $={...}.VERSION,
+ */
+const getCurrentVersionVar = (
+  oldFile: string,
+  autoUpdaterLocation: LocationResult
+): string | null => {
+  // Look backwards from our match to find the current version variable
+  // Pattern: let CURRENT_VAR={...ISSUES_EXPLAINER:...
+  const searchStart = Math.max(0, autoUpdaterLocation.startIndex - 500);
+  const searchChunk = oldFile.slice(
+    searchStart,
+    autoUpdaterLocation.startIndex
+  );
+
+  // Find the last "let VAR={" pattern with ISSUES_EXPLAINER reference (minified format)
+  const pattern = /let ([$\w]+)=\{[^}]*ISSUES_EXPLAINER:/g;
+  let lastMatch = null;
+  let match;
+
+  while ((match = pattern.exec(searchChunk)) !== null) {
+    lastMatch = match;
+  }
+
+  if (!lastMatch) {
+    console.error(
+      'patch: preventUnsupportedUpdates: failed to find current version variable'
+    );
+    return null;
+  }
+
+  return lastMatch[1];
+};
+
+export const writePreventUnsupportedUpdates = (
+  oldFile: string
+): string | null => {
+  const location = getAutoUpdaterLocation(oldFile);
+  if (!location) {
+    return null;
+  }
+
+  const currentVersionVar = getCurrentVersionVar(oldFile, location);
+  if (!currentVersionVar) {
+    return null;
+  }
+
+  const channelVar = location.identifiers![1];
+  const versionVar = location.identifiers![2];
+  const fetchFunc = location.identifiers![3];
+  const nextVar = location.identifiers![4];
+  const nextFunc = location.identifiers![5];
+
+  // Construct the replacement with the tweakcc version check injected
+  // The check wraps the version fetch to check if tweakcc supports the version.
+  // If the prompts file doesn't exist (404), it returns the current version to block the update.
+  const tweakccVersionCheck = `${versionVar}=await(async()=>{let v=await ${fetchFunc}(${channelVar});if(!v)return v;try{const r=await fetch(\`https://raw.githubusercontent.com/Piebald-AI/tweakcc/refs/heads/main/data/prompts/prompts-\${v}.json\`,{method:'HEAD'});if(!r.ok)return ${currentVersionVar};}catch(e){}return v;})(),`;
+
+  // Reconstruct the original prefix (BUILD_TIME part) which we matched but want to preserve
+  const buildTimeMatch = location.identifiers![0].match(/BUILD_TIME:"[^"]+"\}/);
+  const buildTimePrefix = buildTimeMatch ? buildTimeMatch[0] : '';
+
+  const replacement =
+    buildTimePrefix +
+    `.VERSION,` +
+    `${channelVar}=hq()?.autoUpdatesChannel??"latest",` +
+    tweakccVersionCheck +
+    `${nextVar}=${nextFunc}();`;
+
+  const newFile =
+    oldFile.slice(0, location.startIndex) +
+    replacement +
+    oldFile.slice(location.endIndex);
+
+  showDiff(
+    oldFile,
+    newFile,
+    replacement,
+    location.startIndex,
+    location.endIndex
+  );
+
+  return newFile;
+};

src/types.ts

@@ -115,6 +115,7 @@ export interface MiscConfig {
   increaseFileReadLimit: boolean;
   suppressLineNumbers: boolean;
   suppressRateLimitOptions: boolean;
+  preventUpdateToUnsupportedVersions: boolean;
 }
 
 export interface InputPatternHighlighter {

src/ui/components/MiscView.tsx

@@ -33,6 +33,7 @@ export function MiscView({ onSubmit }: MiscViewProps) {
     increaseFileReadLimit: false,
     suppressLineNumbers: false,
     suppressRateLimitOptions: false,
+    preventUpdateToUnsupportedVersions: false,
   };
 
   const ensureMisc = () => {
@@ -195,6 +196,21 @@ export function MiscView({ onSubmit }: MiscViewProps) {
           });
         },
       },
+      {
+        id: 'preventUnsupportedUpdates',
+        title: 'Prevent updates to unsupported versions',
+        description:
+          'Blocks Claude Code auto-updates to versions not yet supported by tweakcc.',
+        getValue: () =>
+          settings.misc?.preventUpdateToUnsupportedVersions ?? false,
+        toggle: () => {
+          updateSettings(settings => {
+            ensureMisc();
+            settings.misc!.preventUpdateToUnsupportedVersions =
+              !settings.misc!.preventUpdateToUnsupportedVersions;
+          });
+        },
+      },
     ],
     [settings, updateSettings]
   );