diff --git a/src/cliproxy/binary/lifecycle.ts b/src/cliproxy/binary/lifecycle.ts
index 30156777..effbfda5 100644
--- a/src/cliproxy/binary/lifecycle.ts
+++ b/src/cliproxy/binary/lifecycle.ts
@@ -10,19 +10,38 @@ import { downloadAndInstall, deleteBinary, getBinaryPath } from './installer';
 import { info } from '../../utils/ui';
 import { isCliproxyRunning } from '../stats-fetcher';
 import { CLIPROXY_DEFAULT_PORT } from '../config-generator';
+import { CLIPROXY_MAX_STABLE_VERSION } from '../platform-detector';
 
 /** Log helper */
 function log(message: string, verbose: boolean): void {
   if (verbose) console.error(`[cliproxy] ${message}`);
 }
 
+/**
+ * Clamp version to max stable if newer versions are unstable
+ */
+function clampToMaxStable(version: string, verbose: boolean): string {
+  if (isNewerVersion(version, CLIPROXY_MAX_STABLE_VERSION)) {
+    log(`Clamping ${version} to max stable ${CLIPROXY_MAX_STABLE_VERSION}`, verbose);
+    return CLIPROXY_MAX_STABLE_VERSION;
+  }
+  return version;
+}
+
 /** Handle auto-update when binary exists */
 async function handleAutoUpdate(config: BinaryManagerConfig, verbose: boolean): Promise<void> {
   const updateResult = await checkForUpdates(config.binPath, config.version, verbose);
   if (!updateResult.hasUpdate) return;
 
+  // Clamp to max stable version
+  const targetVersion = clampToMaxStable(updateResult.latestVersion, verbose);
+  if (!isNewerVersion(targetVersion, updateResult.currentVersion)) {
+    log(`Already at max stable version ${updateResult.currentVersion}`, verbose);
+    return;
+  }
+
   const proxyRunning = await isCliproxyRunning(CLIPROXY_DEFAULT_PORT);
-  const updateMsg = `CLIProxy Plus update available: v${updateResult.currentVersion} -> v${updateResult.latestVersion}`;
+  const updateMsg = `CLIProxy Plus update available: v${updateResult.currentVersion} -> v${targetVersion}`;
 
   if (proxyRunning) {
     console.log(info(updateMsg));
@@ -32,7 +51,7 @@ async function handleAutoUpdate(config: BinaryManagerConfig, verbose: boolean):
     console.log(info(updateMsg));
     console.log(info('Updating CLIProxy Plus...'));
     deleteBinary(config.binPath, verbose);
-    config.version = updateResult.latestVersion;
+    config.version = targetVersion;
     await downloadAndInstall(config, verbose);
   }
 }
@@ -70,9 +89,10 @@ export async function ensureBinary(config: BinaryManagerConfig): Promise<string>
   if (!config.forceVersion) {
     try {
       const latestVersion = await fetchLatestVersion(verbose);
-      if (latestVersion && isNewerVersion(latestVersion, config.version)) {
-        log(`Using latest version: ${latestVersion} (instead of ${config.version})`, verbose);
-        config.version = latestVersion;
+      const targetVersion = clampToMaxStable(latestVersion, verbose);
+      if (targetVersion && isNewerVersion(targetVersion, config.version)) {
+        log(`Using version: ${targetVersion} (instead of ${config.version})`, verbose);
+        config.version = targetVersion;
       }
     } catch {
       log(`Using pinned version: ${config.version}`, verbose);
diff --git a/src/cliproxy/platform-detector.ts b/src/cliproxy/platform-detector.ts
index 1d8333b2..bbe76688 100644
--- a/src/cliproxy/platform-detector.ts
+++ b/src/cliproxy/platform-detector.ts
@@ -14,6 +14,13 @@ import { PlatformInfo, SupportedOS, SupportedArch, ArchiveExtension } from './ty
  */
 export const CLIPROXY_FALLBACK_VERSION = '6.6.40-0';
 
+/**
+ * Maximum stable version cap - prevents auto-update to known unstable releases
+ * v81+ has context cancellation bugs causing intermittent 500 errors
+ * See: https://github.com/kaitranntt/ccs/issues/269
+ */
+export const CLIPROXY_MAX_STABLE_VERSION = '6.6.80-0';
+
 /** @deprecated Use CLIPROXY_FALLBACK_VERSION instead */
 export const CLIPROXY_VERSION = CLIPROXY_FALLBACK_VERSION;