diff --git a/routes.js b/routes.js
index b994e0d..d5cbe46 100644
--- a/routes.js
+++ b/routes.js
@@ -392,10 +392,13 @@ async function handleDirectMessages(req, res) {
 
     logInfo(`Direct forwarding to ${model.type} endpoint: ${endpoint.base_url}`);
 
-    // Get API key
+    // Get API key - support client x-api-key for anthropic endpoint
     let authHeader;
     try {
-      authHeader = await getApiKey(req.headers.authorization);
+      const clientAuthFromXApiKey = req.headers['x-api-key']
+        ? `Bearer ${req.headers['x-api-key']}`
+        : null;
+      authHeader = await getApiKey(req.headers.authorization || clientAuthFromXApiKey);
     } catch (error) {
       logError('Failed to get API key', error);
       return res.status(500).json({ 
diff --git a/transformers/request-anthropic.js b/transformers/request-anthropic.js
index 003edf9..0c88377 100644
--- a/transformers/request-anthropic.js
+++ b/transformers/request-anthropic.js
@@ -163,9 +163,6 @@ export function getAnthropicHeaders(authHeader, clientHeaders = {}, isStreaming
     'accept': 'application/json',
     'content-type': 'application/json',
     'anthropic-version': clientHeaders['anthropic-version'] || '2023-06-01',
-    // Prefer client-provided x-api-key for anthropic endpoint format
-    ...(clientHeaders['x-api-key'] ? { 'x-api-key': clientHeaders['x-api-key'] } : {}),
-    'authorization': authHeader || '',
     'x-api-provider': 'anthropic',
     'x-factory-client': 'cli',
     'x-session-id': sessionId,
@@ -175,6 +172,14 @@ export function getAnthropicHeaders(authHeader, clientHeaders = {}, isStreaming
     'connection': 'keep-alive'
   };
 
+  // Prefer client-provided x-api-key for anthropic endpoint format
+  if (clientHeaders['x-api-key']) {
+    headers['x-api-key'] = clientHeaders['x-api-key'];
+  } else if (authHeader) {
+    // If no client x-api-key, use authorization header (from FACTORY_API_KEY or refresh token)
+    headers['authorization'] = authHeader;
+  }
+
   // Handle anthropic-beta header based on reasoning configuration
   const reasoningLevel = modelId ? getModelReasoning(modelId) : null;
   let betaValues = [];