Bug: GraphQLIndexer.query ignores GraphQL-level errors in an HTTP 20…

src/indexer.ts

@@ -1,3 +1,4 @@
+import { ConduitError, UNKNOWN_CONTRACT_ERROR_CODE } from './errors.js';
 import { IndexerTimeoutError } from './errors.js';
 
 export interface GraphQLQueryOptions {
@@ -106,7 +107,26 @@ export class GraphQLIndexer {
       throw new Error(`GraphQL query failed with status ${response.status}: ${response.statusText}`);
     }
 
-    return (await response.json()) as unknown;
+    const body = (await response.json()) as {
+      data?: unknown;
+      errors?: unknown[];
+    };
+
+    if (Array.isArray(body?.errors) && body.errors.length > 0) {
+      const messages = body.errors
+        .map((error) => {
+          if (error && typeof error === 'object' && 'message' in error) {
+            const message = (error as { message?: unknown }).message;
+            return typeof message === 'string' && message.length > 0 ? message : JSON.stringify(error);
+          }
+          return String(error);
+        })
+        .filter((message) => message.length > 0);
+
+      throw new ConduitError('stream', UNKNOWN_CONTRACT_ERROR_CODE, messages.join('; '));
+    }
+
+    return body?.data;
   }
 
   /**

src/tests/graphql-indexer-memory-leak.test.ts

@@ -70,6 +70,28 @@ describe('GraphQLIndexer Memory Leak & Real Network I/O Tests', () => {
     indexer.cleanup();
   });
 
+  it('throws when a GraphQL response contains query-level errors despite HTTP 200', async () => {
+    vi.spyOn(globalThis, 'fetch').mockResolvedValue({
+      ok: true,
+      status: 200,
+      json: async () => ({
+        data: null,
+        errors: [
+          { message: 'Cannot query field "doesNotExist" on type "Query".' },
+          { message: 'Resolver error: boom' },
+        ],
+      }),
+    } as Response);
+
+    const indexer = new GraphQLIndexer(endpoint);
+
+    await expect(indexer.query({ query: 'query { doesNotExist }' })).rejects.toThrow(
+      'Cannot query field "doesNotExist" on type "Query".'
+    );
+
+    indexer.cleanup();
+  });
+
   it('subscribes and properly cleans up active subscriptions on unsubscribe()', async () => {
     const indexer = new GraphQLIndexer(endpoint);