Merge provider metadata with header metadata in RequestContext class

src/handlers/services/requestContext.ts

@@ -109,9 +109,19 @@ export class RequestContext {
 
   get metadata(): Record<string, string> {
     try {
-      return JSON.parse(this.requestHeaders[HEADER_KEYS.METADATA] ?? '{}');
+      const headerMetadata = JSON.parse(
+        this.requestHeaders[HEADER_KEYS.METADATA] ?? '{}'
+      );
+      const configMetadata = this.providerOption.metadata || {};
+
+      // Merge: config metadata + header metadata (headers win conflicts)
+      return {
+        ...configMetadata,
+        ...headerMetadata,
+      };
     } catch (error) {
-      return {};
+      // Fallback to config metadata only
+      return this.providerOption.metadata || {};
     }
   }
 

tests/unit/src/handlers/services/requestContext.test.ts

@@ -371,24 +371,81 @@ describe('RequestContext', () => {
       expect(requestContext.metadata).toEqual({ userId: 'user123' });
     });
 
-    it('should return empty object for invalid JSON', () => {
+    it('should merge provider metadata with header metadata', () => {
+      const providerOptionWithMetadata = {
+        ...mockProviderOption,
+        metadata: { region: 'us-east-1', environment: 'prod', team: 'ai' },
+      };
+      const headers = {
+        [HEADER_KEYS.METADATA]: JSON.stringify({
+          userId: 'user123',
+          team: 'overridden',
+        }),
+      };
+      const context = new RequestContext(
+        mockContext,
+        providerOptionWithMetadata,
+        'chatComplete' as endpointStrings,
+        headers,
+        {},
+        'POST',
+        0
+      );
+
+      expect(context.metadata).toEqual({
+        region: 'us-east-1',
+        environment: 'prod',
+        team: 'overridden', // Header metadata wins
+        userId: 'user123',
+      });
+    });
+
+    it('should return provider metadata when no header metadata', () => {
+      const providerOptionWithMetadata = {
+        ...mockProviderOption,
+        metadata: { region: 'us-east-1', environment: 'prod' },
+      };
+      const context = new RequestContext(
+        mockContext,
+        providerOptionWithMetadata,
+        'chatComplete' as endpointStrings,
+        {},
+        {},
+        'POST',
+        0
+      );
+
+      expect(context.metadata).toEqual({
+        region: 'us-east-1',
+        environment: 'prod',
+      });
+    });
+
+    it('should fallback to provider metadata for invalid JSON header', () => {
+      const providerOptionWithMetadata = {
+        ...mockProviderOption,
+        metadata: { region: 'us-east-1', fallback: 'true' },
+      };
       const headers = {
         [HEADER_KEYS.METADATA]: '{invalid json}',
       };
       const context = new RequestContext(
         mockContext,
-        mockProviderOption,
+        providerOptionWithMetadata,
         'chatComplete' as endpointStrings,
         headers,
         {},
         'POST',
         0
       );
 
-      expect(context.metadata).toEqual({});
+      expect(context.metadata).toEqual({
+        region: 'us-east-1',
+        fallback: 'true',
+      });
     });
 
-    it('should return empty object when no metadata header', () => {
+    it('should return empty object when no metadata header and no provider metadata', () => {
       const context = new RequestContext(
         mockContext,
         mockProviderOption,