diff --git a/src/cliproxy/config/env-builder.ts b/src/cliproxy/config/env-builder.ts
index 4674ecd3..38b7cc28 100644
--- a/src/cliproxy/config/env-builder.ts
+++ b/src/cliproxy/config/env-builder.ts
@@ -10,6 +10,7 @@ import { getGlobalEnvConfig } from '../../config/unified-config-loader';
 import { getEffectiveApiKey } from '../auth-token-manager';
 import { expandPath } from '../../utils/helpers';
 import { warn } from '../../utils/ui';
+import { CompositeTierConfig } from '../../config/unified-config-types';
 import {
   validatePort,
   validateRemotePort,
@@ -413,3 +414,64 @@ export function getRemoteEnvVars(
 
   return env;
 }
+
+/**
+ * Get environment variables for composite variant.
+ * Uses root URL (no /api/provider/ path) for model-based routing.
+ * Each tier maps to a different provider's model, routed by CLIProxyAPI.
+ *
+ * @param tiers Per-tier provider+model mappings
+ * @param defaultTier Which tier ANTHROPIC_MODEL equals
+ * @param port Local CLIProxy port
+ * @param customSettingsPath Optional path to user's custom settings file
+ */
+export function getCompositeEnvVars(
+  tiers: { opus: CompositeTierConfig; sonnet: CompositeTierConfig; haiku: CompositeTierConfig },
+  defaultTier: 'opus' | 'sonnet' | 'haiku',
+  port: number = CLIPROXY_DEFAULT_PORT,
+  customSettingsPath?: string
+): Record<string, string> {
+  const globalEnv = getGlobalEnvVars();
+
+  // Load user settings if provided (may contain additional env vars like hooks)
+  let additionalEnvVars: Record<string, string> = {};
+  if (customSettingsPath) {
+    const expandedPath = expandPath(customSettingsPath);
+    if (fs.existsSync(expandedPath)) {
+      try {
+        const content = fs.readFileSync(expandedPath, 'utf-8');
+        const settings: ProviderSettings = JSON.parse(content);
+        if (settings.env && typeof settings.env === 'object') {
+          // Extract non-core env vars (hooks, etc.)
+          const {
+            ANTHROPIC_BASE_URL: _baseUrl,
+            ANTHROPIC_AUTH_TOKEN: _authToken,
+            ANTHROPIC_MODEL: _model,
+            ANTHROPIC_DEFAULT_OPUS_MODEL: _opus,
+            ANTHROPIC_DEFAULT_SONNET_MODEL: _sonnet,
+            ANTHROPIC_DEFAULT_HAIKU_MODEL: _haiku,
+            ...extra
+          } = settings.env as Record<string, string>;
+          additionalEnvVars = extra;
+        }
+      } catch {
+        // Invalid JSON — ignore
+      }
+    }
+  }
+
+  const validPort = validatePort(port);
+  const defaultModel = tiers[defaultTier].model;
+
+  return {
+    ...globalEnv,
+    ...additionalEnvVars,
+    // Root URL — CLIProxyAPI routes based on model name in request body
+    ANTHROPIC_BASE_URL: `http://127.0.0.1:${validPort}`,
+    ANTHROPIC_AUTH_TOKEN: getEffectiveApiKey(),
+    ANTHROPIC_MODEL: defaultModel,
+    ANTHROPIC_DEFAULT_OPUS_MODEL: tiers.opus.model,
+    ANTHROPIC_DEFAULT_SONNET_MODEL: tiers.sonnet.model,
+    ANTHROPIC_DEFAULT_HAIKU_MODEL: tiers.haiku.model,
+  };
+}
diff --git a/src/cliproxy/executor/env-resolver.ts b/src/cliproxy/executor/env-resolver.ts
index 2747a70a..bb452cd2 100644
--- a/src/cliproxy/executor/env-resolver.ts
+++ b/src/cliproxy/executor/env-resolver.ts
@@ -9,9 +9,15 @@
  * - WebSearch and ImageAnalysis hook integration
  */
 
-import { getEffectiveEnvVars, getRemoteEnvVars, applyThinkingConfig } from '../config-generator';
+import {
+  getEffectiveEnvVars,
+  getRemoteEnvVars,
+  getCompositeEnvVars,
+  applyThinkingConfig,
+} from '../config-generator';
 import { applyExtendedContextConfig } from '../config/extended-context-config';
 import { CLIProxyProvider } from '../types';
+import { CompositeTierConfig } from '../../config/unified-config-types';
 import { getWebSearchHookEnv } from '../../utils/websearch-manager';
 import { getImageAnalysisHookEnv } from '../../utils/hooks/get-image-analysis-hook-env';
 import { CodexReasoningProxy } from '../codex-reasoning-proxy';
@@ -41,6 +47,16 @@ export interface ProxyChainConfig {
   /** Extended context override: true = force on, false = force off, undefined = auto */
   extendedContextOverride?: boolean;
   verbose: boolean;
+  /** Composite variant: true when mixing providers per tier */
+  isComposite?: boolean;
+  /** Composite variant: per-tier provider+model mappings */
+  compositeTiers?: {
+    opus: CompositeTierConfig;
+    sonnet: CompositeTierConfig;
+    haiku: CompositeTierConfig;
+  };
+  /** Composite variant: which tier is the default */
+  compositeDefaultTier?: 'opus' | 'sonnet' | 'haiku';
 }
 
 /**
@@ -60,12 +76,23 @@ export function buildClaudeEnvironment(config: ProxyChainConfig): Record<string,
     extendedContextOverride,
     codexReasoningPort,
     toolSanitizationPort,
+    isComposite,
+    compositeTiers,
+    compositeDefaultTier,
   } = config;
 
-  // Build base env vars - remote or local
+  // Build base env vars - composite, remote, or local
   let envVars: NodeJS.ProcessEnv;
 
-  if (useRemoteProxy && remoteConfig) {
+  if (isComposite && compositeTiers && compositeDefaultTier) {
+    // Composite variant: root URL, per-tier models from different providers
+    envVars = getCompositeEnvVars(
+      compositeTiers,
+      compositeDefaultTier,
+      localPort,
+      customSettingsPath
+    );
+  } else if (useRemoteProxy && remoteConfig) {
     if (httpsTunnel && tunnelPort) {
       // HTTPS remote via local tunnel - use HTTP to tunnel
       envVars = getRemoteEnvVars(
diff --git a/src/cliproxy/executor/index.ts b/src/cliproxy/executor/index.ts
index 4f7d430d..fedd70b7 100644
--- a/src/cliproxy/executor/index.ts
+++ b/src/cliproxy/executor/index.ts
@@ -113,6 +113,12 @@ export async function execClaudeWithCLIProxy(
     }
   };
 
+  // Helper: Extract unique providers from composite tiers
+  const compositeProviders =
+    cfg.isComposite && cfg.compositeTiers
+      ? [...new Set(Object.values(cfg.compositeTiers).map((t) => t.provider))]
+      : [];
+
   // 0. Resolve proxy configuration (CLI > ENV > config.yaml > defaults)
   const unifiedConfig = loadOrCreateUnifiedConfig();
 
@@ -421,7 +427,14 @@ export async function execClaudeWithCLIProxy(
 
   // Handle --config
   if (forceConfig && supportsModelConfig(provider)) {
-    await configureProviderModel(provider, true, cfg.customSettingsPath);
+    // Block --config for composite variants (per-tier models in config.yaml)
+    if (cfg.isComposite) {
+      console.log(
+        warn('Composite variants use per-tier config. Edit config.yaml to change tier models.')
+      );
+    } else {
+      await configureProviderModel(provider, true, cfg.customSettingsPath);
+    }
     process.exit(0);
   }
 
@@ -477,7 +490,22 @@ export async function execClaudeWithCLIProxy(
   if (providerConfig.requiresOAuth && !skipLocalAuth) {
     log(`Checking authentication for ${provider}`);
 
-    if (forceAuth || !isAuthenticated(provider)) {
+    // Multi-provider auth check for composite variants
+    if (compositeProviders.length > 0) {
+      const unauthenticatedProviders: string[] = [];
+      for (const p of compositeProviders) {
+        if (!isAuthenticated(p)) {
+          unauthenticatedProviders.push(p);
+        }
+      }
+      if (unauthenticatedProviders.length > 0) {
+        console.error(fail('Composite variant requires authentication for multiple providers:'));
+        for (const p of unauthenticatedProviders) {
+          console.error(`    - ${p} (run "ccs ${p} --auth")`);
+        }
+        process.exit(1);
+      }
+    } else if (forceAuth || !isAuthenticated(provider)) {
       const { triggerOAuth } = await import('../auth-handler');
       const authSuccess = await triggerOAuth(provider, {
         verbose,
@@ -498,8 +526,14 @@ export async function execClaudeWithCLIProxy(
       log(`${provider} already authenticated`);
     }
 
-    // 3a. Proactive token refresh
-    await handleTokenExpiration(provider, verbose);
+    // 3a. Proactive token refresh (multi-provider for composite)
+    if (compositeProviders.length > 0) {
+      for (const p of compositeProviders) {
+        await handleTokenExpiration(p, verbose);
+      }
+    } else {
+      await handleTokenExpiration(provider, verbose);
+    }
 
     // 3a-1. Update lastUsedAt
     const usedAccount = getDefaultAccount(provider);
@@ -510,7 +544,14 @@ export async function execClaudeWithCLIProxy(
 
   // 3b. Preflight quota check (Antigravity only)
   if (!skipLocalAuth) {
-    await handleQuotaCheck(provider);
+    // Multi-tier quota check for composite variants (check if ANY tier uses 'agy')
+    if (compositeProviders.length > 0) {
+      if (compositeProviders.includes('agy')) {
+        await handleQuotaCheck('agy');
+      }
+    } else {
+      await handleQuotaCheck(provider);
+    }
   }
 
   // 3c. Account safety: enforce cross-provider isolation
@@ -533,23 +574,46 @@ export async function execClaudeWithCLIProxy(
     await configureProviderModel(provider, false, cfg.customSettingsPath);
   }
 
-  // 5. Check for broken models
-  const currentModel = getCurrentModel(provider, cfg.customSettingsPath);
-  if (currentModel && isModelBroken(provider, currentModel)) {
-    const modelEntry = findModel(provider, currentModel);
-    const issueUrl = getModelIssueUrl(provider, currentModel);
-    console.error('');
-    console.error(warn(`${modelEntry?.name || currentModel} has known issues with Claude Code`));
-    console.error('    Tool calls will fail. Use "gemini-3-pro-preview" instead.');
-    if (issueUrl) {
-      console.error(`    Tracking: ${issueUrl}`);
+  // 5. Check for broken models (multi-tier for composite)
+  if (compositeProviders.length > 0 && cfg.compositeTiers) {
+    // Check all tier models in composite variant
+    const tiers: Array<'opus' | 'sonnet' | 'haiku'> = ['opus', 'sonnet', 'haiku'];
+    for (const tier of tiers) {
+      const tierConfig = cfg.compositeTiers[tier];
+      if (tierConfig && isModelBroken(tierConfig.provider, tierConfig.model)) {
+        const modelEntry = findModel(tierConfig.provider, tierConfig.model);
+        const issueUrl = getModelIssueUrl(tierConfig.provider, tierConfig.model);
+        console.error('');
+        console.error(
+          warn(
+            `${tier} tier: ${modelEntry?.name || tierConfig.model} has known issues with Claude Code`
+          )
+        );
+        console.error('    Tool calls will fail. Consider changing the model in config.yaml.');
+        if (issueUrl) {
+          console.error(`    Tracking: ${issueUrl}`);
+        }
+        console.error('');
+      }
     }
-    if (skipLocalAuth) {
-      console.error('    Note: Model may be overridden by remote proxy configuration.');
-    } else {
-      console.error(`    Run "ccs ${provider} --config" to change model.`);
+  } else {
+    const currentModel = getCurrentModel(provider, cfg.customSettingsPath);
+    if (currentModel && isModelBroken(provider, currentModel)) {
+      const modelEntry = findModel(provider, currentModel);
+      const issueUrl = getModelIssueUrl(provider, currentModel);
+      console.error('');
+      console.error(warn(`${modelEntry?.name || currentModel} has known issues with Claude Code`));
+      console.error('    Tool calls will fail. Use "gemini-3-pro-preview" instead.');
+      if (issueUrl) {
+        console.error(`    Tracking: ${issueUrl}`);
+      }
+      if (skipLocalAuth) {
+        console.error('    Note: Model may be overridden by remote proxy configuration.');
+      } else {
+        console.error(`    Run "ccs ${provider} --config" to change model.`);
+      }
+      console.error('');
     }
-    console.error('');
   }
 
   // 6. Ensure user settings file exists
@@ -640,6 +704,9 @@ export async function execClaudeWithCLIProxy(
     thinkingOverride,
     extendedContextOverride,
     verbose,
+    isComposite: cfg.isComposite,
+    compositeTiers: cfg.compositeTiers,
+    compositeDefaultTier: cfg.compositeDefaultTier,
   });
 
   if (initialEnvVars.ANTHROPIC_BASE_URL) {
@@ -729,6 +796,9 @@ export async function execClaudeWithCLIProxy(
     thinkingOverride,
     extendedContextOverride,
     verbose,
+    isComposite: cfg.isComposite,
+    compositeTiers: cfg.compositeTiers,
+    compositeDefaultTier: cfg.compositeDefaultTier,
   });
 
   const webSearchEnv = getWebSearchHookEnv();