diff --git a/src/cliproxy/services/variant-service.ts b/src/cliproxy/services/variant-service.ts
index a2372961..5915424e 100644
--- a/src/cliproxy/services/variant-service.ts
+++ b/src/cliproxy/services/variant-service.ts
@@ -253,7 +253,7 @@ export function updateVariant(name: string, updates: UpdateVariantOptions): Vari
           existing.port
         );
       } else if (updates.model !== undefined) {
-        updateSettingsModel(settingsPath, updates.model);
+        updateSettingsModel(settingsPath, updates.model, existing.provider);
       }
     }
 
diff --git a/src/cliproxy/services/variant-settings.ts b/src/cliproxy/services/variant-settings.ts
index 3dd93b4d..8dc6425d 100644
--- a/src/cliproxy/services/variant-settings.ts
+++ b/src/cliproxy/services/variant-settings.ts
@@ -44,8 +44,7 @@ function buildSettingsEnv(
   port: number = CLIPROXY_DEFAULT_PORT
 ): SettingsEnv {
   const baseEnv = getClaudeEnvVars(provider as CLIProxyProvider, port);
-  const codexSonnetModel =
-    provider === 'codex' && !model.match(/-(xhigh|high|medium)$/) ? `${model}-high` : model;
+  const codexSonnetModel = normalizeCodexSonnetModel(provider, model);
 
   return {
     ANTHROPIC_BASE_URL: baseEnv.ANTHROPIC_BASE_URL || '',
@@ -57,6 +56,14 @@ function buildSettingsEnv(
   };
 }
 
+function normalizeCodexSonnetModel(
+  provider: CLIProxyProfileName | undefined,
+  model: string
+): string {
+  if (provider !== 'codex') return model;
+  return /-(xhigh|high|medium)$/.test(model) ? model : `${model}-high`;
+}
+
 /**
  * Ensure directory exists
  */
@@ -268,7 +275,11 @@ export function deleteSettingsFile(settingsPath: string): boolean {
 /**
  * Update model in an existing settings file
  */
-export function updateSettingsModel(settingsPath: string, model: string): void {
+export function updateSettingsModel(
+  settingsPath: string,
+  model: string,
+  provider?: CLIProxyProfileName
+): void {
   const fileName = path.basename(settingsPath);
   if (fileName.startsWith('composite-')) {
     console.log(
@@ -288,9 +299,10 @@ export function updateSettingsModel(settingsPath: string, model: string): void {
 
     if (model) {
       settings.env = settings.env || ({} as SettingsEnv);
+      const codexSonnetModel = normalizeCodexSonnetModel(provider, model);
       settings.env.ANTHROPIC_MODEL = model;
       settings.env.ANTHROPIC_DEFAULT_OPUS_MODEL = model;
-      settings.env.ANTHROPIC_DEFAULT_SONNET_MODEL = model;
+      settings.env.ANTHROPIC_DEFAULT_SONNET_MODEL = codexSonnetModel;
     } else {
       // Clear model settings to use defaults
       delete (settings.env as unknown as Record<string, string>).ANTHROPIC_MODEL;
diff --git a/tests/unit/cliproxy/variant-update-service.test.ts b/tests/unit/cliproxy/variant-update-service.test.ts
index d23a2e4e..e75c80f7 100644
--- a/tests/unit/cliproxy/variant-update-service.test.ts
+++ b/tests/unit/cliproxy/variant-update-service.test.ts
@@ -107,4 +107,28 @@ cliproxy:
     const config = loadOrCreateUnifiedConfig();
     expect(config.cliproxy?.variants?.demo?.provider).toBe('codex');
   });
+
+  it('preserves codex sonnet alias on model-only updates', () => {
+    const toCodex = updateVariant('demo', {
+      provider: 'codex',
+      model: 'gpt-5.3-codex',
+    });
+    expect(toCodex.success).toBe(true);
+
+    const settingsPath = path.join(tmpDir, 'gemini-demo.settings.json');
+    let settings = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string>;
+    };
+    expect(settings.env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('gpt-5.3-codex-high');
+
+    const modelOnly = updateVariant('demo', { model: 'gpt-5.3-codex' });
+    expect(modelOnly.success).toBe(true);
+
+    settings = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string>;
+    };
+    expect(settings.env.ANTHROPIC_MODEL).toBe('gpt-5.3-codex');
+    expect(settings.env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe('gpt-5.3-codex');
+    expect(settings.env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('gpt-5.3-codex-high');
+  });
 });