test(cliproxy): add regression coverage for update consistency

- verify provider change requires model and rewrites provider-specific env

- verify composite updates preserve custom settings path and fields

tests/unit/cliproxy/composite-variant-service.test.ts

@@ -221,6 +221,67 @@ cliproxy:
     expect(result.variant?.tiers?.opus.account).toBe('team-a');
   });
 
+  it('should preserve existing custom settings path and custom settings fields', () => {
+    const customSettingsPath = path.join(tmpDir, 'custom', 'my-composite.settings.json');
+    const initialConfig: CompositeVariantConfig = {
+      type: 'composite',
+      default_tier: 'sonnet',
+      tiers: {
+        opus: { provider: 'gemini', model: 'gemini-3-pro-preview' },
+        sonnet: { provider: 'agy', model: 'claude-sonnet-4-5-thinking' },
+        haiku: { provider: 'agy', model: 'claude-haiku-4-5-20251001' },
+      },
+      settings: customSettingsPath,
+      port: 8318,
+    };
+    saveCompositeVariantUnified('test', initialConfig);
+
+    fs.mkdirSync(path.dirname(customSettingsPath), { recursive: true });
+    fs.writeFileSync(
+      customSettingsPath,
+      JSON.stringify(
+        {
+          env: {
+            ANTHROPIC_BASE_URL: 'http://127.0.0.1:8318',
+            ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+            ANTHROPIC_MODEL: 'claude-sonnet-4-5-thinking',
+            ANTHROPIC_DEFAULT_OPUS_MODEL: 'gemini-3-pro-preview',
+            ANTHROPIC_DEFAULT_SONNET_MODEL: 'claude-sonnet-4-5-thinking',
+            ANTHROPIC_DEFAULT_HAIKU_MODEL: 'claude-haiku-4-5-20251001',
+            CUSTOM_ENV: 'preserve-this',
+          },
+          hooks: { PreToolUse: [{ matcher: 'WebSearch', hooks: [] }] },
+          customPreset: true,
+        },
+        null,
+        2
+      ),
+      'utf-8'
+    );
+
+    const result = updateCompositeVariant('test', {
+      tiers: {
+        sonnet: { provider: 'agy', model: 'claude-sonnet-4-5-thinking(high)' },
+      },
+    });
+
+    expect(result.success).toBe(true);
+    expect(result.variant?.settings).toBe(customSettingsPath);
+
+    const updatedSettings = JSON.parse(fs.readFileSync(customSettingsPath, 'utf-8')) as {
+      env: Record<string, string>;
+      hooks: { PreToolUse: unknown[] };
+      customPreset: boolean;
+    };
+    expect(updatedSettings.env.ANTHROPIC_MODEL).toBe('claude-sonnet-4-5-thinking(high)');
+    expect(updatedSettings.env.CUSTOM_ENV).toBe('preserve-this');
+    expect(updatedSettings.hooks.PreToolUse.length).toBe(1);
+    expect(updatedSettings.customPreset).toBe(true);
+
+    const variants = listVariantsFromConfig();
+    expect(variants.test.settings).toBe(customSettingsPath);
+  });
+
   it('should return error when variant does not exist', () => {
     const result = updateCompositeVariant('nonexistent', {
       tiers: {

tests/unit/cliproxy/variant-update-service.test.ts

@@ -0,0 +1,110 @@
+/**
+ * Unit tests for single-variant provider/model update behavior.
+ */
+
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import { updateVariant } from '../../../src/cliproxy/services/variant-service';
+import { loadOrCreateUnifiedConfig } from '../../../src/config/unified-config-loader';
+
+describe('updateVariant - provider/model consistency', () => {
+  let tmpDir: string;
+  let originalCcsDir: string | undefined;
+
+  beforeEach(() => {
+    tmpDir = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-variant-update-test-'));
+    originalCcsDir = process.env.CCS_DIR;
+    process.env.CCS_DIR = tmpDir;
+
+    const settingsPath = path.join(tmpDir, 'gemini-demo.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify(
+        {
+          env: {
+            ANTHROPIC_BASE_URL: 'http://127.0.0.1:8318/api/provider/gemini',
+            ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+            ANTHROPIC_MODEL: 'gemini-2.5-pro',
+            ANTHROPIC_DEFAULT_OPUS_MODEL: 'gemini-2.5-pro',
+            ANTHROPIC_DEFAULT_SONNET_MODEL: 'gemini-2.5-pro',
+            ANTHROPIC_DEFAULT_HAIKU_MODEL: 'gemini-2.5-flash',
+            CUSTOM_FLAG: 'keep-me',
+          },
+          hooks: { PreToolUse: [{ matcher: 'WebSearch', hooks: [] }] },
+        },
+        null,
+        2
+      ),
+      'utf-8'
+    );
+
+    fs.writeFileSync(
+      path.join(tmpDir, 'config.yaml'),
+      `version: 2
+accounts: {}
+profiles: {}
+preferences:
+  theme: system
+  telemetry: false
+  auto_update: true
+cliproxy:
+  oauth_accounts: {}
+  providers:
+    - gemini
+    - codex
+    - agy
+  variants:
+    demo:
+      provider: gemini
+      settings: ${settingsPath}
+      port: 8318
+`,
+      'utf-8'
+    );
+  });
+
+  afterEach(() => {
+    if (originalCcsDir !== undefined) {
+      process.env.CCS_DIR = originalCcsDir;
+    } else {
+      delete process.env.CCS_DIR;
+    }
+
+    if (tmpDir && fs.existsSync(tmpDir)) {
+      fs.rmSync(tmpDir, { recursive: true, force: true });
+    }
+  });
+
+  it('rejects provider change without model update', () => {
+    const result = updateVariant('demo', { provider: 'codex' });
+    expect(result.success).toBe(false);
+    expect(result.error).toContain('Changing provider requires model update');
+  });
+
+  it('updates provider and regenerates provider-specific core env in same settings file', () => {
+    const result = updateVariant('demo', {
+      provider: 'codex',
+      model: 'gpt-5.1-codex-mini',
+    });
+
+    expect(result.success).toBe(true);
+    expect(result.variant?.provider).toBe('codex');
+    expect(result.variant?.model).toBe('gpt-5.1-codex-mini');
+
+    const settingsPath = path.join(tmpDir, 'gemini-demo.settings.json');
+    const settings = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string>;
+      hooks: { PreToolUse: unknown[] };
+    };
+
+    expect(settings.env.ANTHROPIC_BASE_URL).toContain('/api/provider/codex');
+    expect(settings.env.ANTHROPIC_MODEL).toBe('gpt-5.1-codex-mini');
+    expect(settings.env.CUSTOM_FLAG).toBe('keep-me');
+    expect(settings.hooks.PreToolUse.length).toBe(1);
+
+    const config = loadOrCreateUnifiedConfig();
+    expect(config.cliproxy?.variants?.demo?.provider).toBe('codex');
+  });
+});