diff --git a/src/defaultSettings.ts b/src/defaultSettings.ts
index 626fadd4..3785f102 100644
--- a/src/defaultSettings.ts
+++ b/src/defaultSettings.ts
@@ -703,6 +703,7 @@ export const DEFAULT_SETTINGS: Settings = {
     mcpServerBatchSize: null,
     tableFormat: 'default',
     enableSwarmMode: true,
+    preventUpdateToUnsupportedVersions: false,
   },
   toolsets: [],
   defaultToolset: null,
diff --git a/src/patches/index.ts b/src/patches/index.ts
index 3c4fdd9c..8beadf73 100644
--- a/src/patches/index.ts
+++ b/src/patches/index.ts
@@ -66,6 +66,7 @@ import {
   restoreClijsFromBackup,
 } from '../installationBackup';
 import { compareVersions } from '../systemPromptSync';
+import { writePreventUnsupportedUpdates } from './preventUnsupportedUpdates';
 
 export { showDiff, showPositionalDiff, globalReplace } from './patchDiffing';
 export {
@@ -336,6 +337,13 @@ const PATCH_DEFINITIONS = [
     group: PatchGroup.FEATURES,
     description: '/title command will be created & enabled',
   },
+  {
+    id: 'prevent-unsupported-updates',
+    name: 'prevent unsupported updates',
+    group: PatchGroup.MISC_CONFIGURABLE,
+    description:
+      'Auto-updates blocked for CC versions not yet supported by tweakcc',
+  },
 ] as const;
 
 /** Union type of all valid patch IDs */
@@ -715,6 +723,10 @@ export const applyCustomization = async (
           compareVersions(ccInstInfo.version, '2.0.64') < 0
         ),
     },
+    'prevent-unsupported-updates': {
+      fn: c => writePreventUnsupportedUpdates(c),
+      condition: !!config.settings.misc?.preventUpdateToUnsupportedVersions,
+    },
   };
 
   // ==========================================================================
diff --git a/src/patches/preventUnsupportedUpdates.ts b/src/patches/preventUnsupportedUpdates.ts
new file mode 100644
index 00000000..59068f78
--- /dev/null
+++ b/src/patches/preventUnsupportedUpdates.ts
@@ -0,0 +1,152 @@
+// 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=FUNC()?.autoUpdatesChannel??"latest",VERSION_VAR=await FUNC(CHANNEL_VAR),OTHER_VAR=FUNC2();
+ *
+ * Note: The function name for autoUpdatesChannel (e.g., hq, z5) varies between builds.
+ *
+ * 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,
+  // - FUNC()?.autoUpdatesChannel??"latest" (function name varies between builds)
+  // - await FUNC(VAR) pattern
+  // Captures:
+  //   [1] = channel var (e.g., _)
+  //   [2] = autoUpdatesChannel function (e.g., z5, hq - varies between builds)
+  //   [3] = version var (e.g., G)
+  //   [4] = fetch function (e.g., v3A)
+  //   [5] = next var (e.g., Z)
+  //   [6] = next func (e.g., Oc)
+  const pattern =
+    /BUILD_TIME:"[^"]+"\}\.VERSION,([$\w]+)=([$\w]+)\(\)\?\.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], // autoUpdatesChannel function (e.g., z5)
+      match[3], // version var (e.g., G)
+      match[4], // fetch function (e.g., v3A)
+      match[5], // next var (e.g., Z)
+      match[6], // next var's function (e.g., Oc)
+    ],
+  };
+};
+
+/**
+ * Gets the variable name used for the current version.
+ * This is typically $ in the code pattern:
+ *   let $={...ISSUES_EXPLAINER:...}.VERSION,
+ */
+const getCurrentVersionVar = (
+  oldFile: string,
+  autoUpdaterLocation: LocationResult
+): string | null => {
+  // Look backwards from our match to find the current version variable
+  // Pattern: let CURRENT_VAR={...ISSUES_EXPLAINER:...
+  const searchStart = Math.max(0, autoUpdaterLocation.startIndex - 500);
+  const searchChunk = oldFile.slice(
+    searchStart,
+    autoUpdaterLocation.startIndex
+  );
+
+  // Find the last "let VAR={" pattern with ISSUES_EXPLAINER reference (minified format)
+  const pattern = /let ([$\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;
+  }
+
+  // Extract captured groups from the pattern match
+  // identifiers: [0]=full match, [1]=channel var, [2]=autoUpdatesChannel func,
+  //              [3]=version var, [4]=fetch func, [5]=next var, [6]=next func
+  const channelVar = location.identifiers![1];
+  const autoUpdatesChannelFunc = location.identifiers![2];
+  const versionVar = location.identifiers![3];
+  const fetchFunc = location.identifiers![4];
+  const nextVar = location.identifiers![5];
+  const nextFunc = location.identifiers![6];
+
+  // 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) or check fails, it returns the current version to block the update.
+  // Fails closed: if we can't verify support, we block the update to be safe.
+  // Wrapped in outer try-catch to ensure no errors propagate that could affect module initialization.
+  const tweakccVersionCheck = `${versionVar}=await(async()=>{try{let v=await ${fetchFunc}(${channelVar});if(!v)return v;try{const r=await fetch(\`https://raw.githubusercontent.com/georpar/tweakcc/refs/heads/main/data/prompts/prompts-\${v}.json\`,{method:'HEAD'});if(!r.ok)return ${currentVersionVar};}catch(e){return ${currentVersionVar};}return v;}catch(e){return null;}})(),`;
+
+  // Extract the BUILD_TIME portion from the matched string (minified format)
+  const buildTimeMatch = location.identifiers![0].match(/BUILD_TIME:"[^"]+"\}/);
+  const buildTimePrefix = buildTimeMatch ? buildTimeMatch[0] : '';
+
+  // Reconstruct the replacement using the captured function name (not hardcoded)
+  const replacement =
+    buildTimePrefix +
+    `.VERSION,` +
+    `${channelVar}=${autoUpdatesChannelFunc}()?.autoUpdatesChannel??"latest",` +
+    tweakccVersionCheck +
+    `${nextVar}=${nextFunc}();`;
+
+  const newFile =
+    oldFile.slice(0, location.startIndex) +
+    replacement +
+    oldFile.slice(location.endIndex);
+
+  showDiff(
+    oldFile,
+    newFile,
+    replacement,
+    location.startIndex,
+    location.endIndex
+  );
+
+  return newFile;
+};
diff --git a/src/types.ts b/src/types.ts
index 57b4f8da..63e5c734 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -121,6 +121,7 @@ export interface MiscConfig {
   mcpServerBatchSize: number | null;
   tableFormat: TableFormat;
   enableSwarmMode: boolean;
+  preventUpdateToUnsupportedVersions: boolean;
 }
 
 export interface InputPatternHighlighter {
diff --git a/src/ui/components/MiscView.tsx b/src/ui/components/MiscView.tsx
index f80a53fc..57b9a93d 100644
--- a/src/ui/components/MiscView.tsx
+++ b/src/ui/components/MiscView.tsx
@@ -47,6 +47,7 @@ export function MiscView({ onSubmit }: MiscViewProps) {
     mcpServerBatchSize: null as number | null,
     tableFormat: 'default' as TableFormat,
     enableSwarmMode: true,
+    preventUpdateToUnsupportedVersions: false,
   };
 
   const ensureMisc = () => {
@@ -324,6 +325,21 @@ 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]
   );