test: add e2e regression test for issue #190 (streamObject flush error) (#373)

* test: add regression test for issue #190 (sparse tool call indices)

Co-Authored-By: Robert Yeakel <robert.yeakel@openrouter.ai>

* test: replace unit test with e2e regression test for issue #190

- Remove sparse array unit test from src/chat/index.test.ts
- Add e2e test using streamObject + jsonSchema (matches issue exactly)
- Test verifies streamObject works without TypeError in flush function

Co-Authored-By: Robert Yeakel <robert.yeakel@openrouter.ai>

* test: remove speculative root cause from issue #190 test comments

Keep only known facts from the issue report

Co-Authored-By: Robert Yeakel <robert.yeakel@openrouter.ai>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

Author: robert-j-y

.changeset/cyan-yaks-push.md

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+---
+---

e2e/issues/issue-190-streamobject-flush-error.test.ts

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+/**
+ * Regression test for GitHub issue #190
+ * https://github.com/OpenRouterTeam/ai-sdk-provider/issues/190
+ *
+ * Issue: streamObject with ai@4 + @openrouter/ai-sdk-provider@0.7.x threw
+ * TypeError in flush: "Cannot read properties of undefined (reading 'sent')"
+ *
+ * Reported: September 24, 2025
+ * Affected versions: ai@4.3.18 + @openrouter/ai-sdk-provider@0.7.5
+ * Working versions: ai@5.x + @openrouter/ai-sdk-provider@1.0.0
+ *
+ * This test verifies that streamObject with JSON Schema completes without error.
+ */
+import type { JSONSchema7 } from 'json-schema';
+
+import { jsonSchema, streamObject } from 'ai';
+import { describe, expect, it, vi } from 'vitest';
+import { createOpenRouter } from '@/src';
+
+vi.setConfig({
+  testTimeout: 60_000,
+});
+
+describe('Issue #190: streamObject flush TypeError', () => {
+  const openrouter = createOpenRouter({
+    apiKey: process.env.OPENROUTER_API_KEY,
+    baseUrl: `${process.env.OPENROUTER_API_BASE}/api/v1`,
+  });
+
+  // Use a model that supports structured output
+  const model = openrouter('openai/gpt-4o-mini');
+
+  it('should stream structured output without TypeError', async () => {
+    // This is the exact schema from the issue report
+    const schema: JSONSchema7 = {
+      type: 'object',
+      properties: {
+        title: { type: 'string', minLength: 3, maxLength: 60 },
+        priority: { type: 'string', enum: ['low', 'medium', 'high'] },
+      },
+      required: ['title', 'priority'],
+      additionalProperties: false,
+    };
+
+    const result = streamObject({
+      model,
+      temperature: 0,
+      system: 'You are a helpful assistant that outputs strictly valid JSON.',
+      messages: [
+        {
+          role: 'user',
+          content:
+            'Generate a concise title (<= 6 words) for a test task and pick priority medium.',
+        },
+      ],
+      schema: jsonSchema(schema),
+    });
+
+    const object = (await result.object) as { title: string; priority: string };
+
+    // Verify the output matches the schema
+    expect(object).toBeDefined();
+    expect(typeof object.title).toBe('string');
+    expect(object.title.length).toBeGreaterThan(0);
+    expect(['low', 'medium', 'high']).toContain(object.priority);
+  });
+
+  it('should handle streamObject with nested schema', async () => {
+    // Test with a more complex nested schema
+    const schema: JSONSchema7 = {
+      type: 'object',
+      properties: {
+        task: {
+          type: 'object',
+          properties: {
+            name: { type: 'string' },
+            status: { type: 'string', enum: ['pending', 'done'] },
+          },
+          required: ['name', 'status'],
+        },
+        tags: {
+          type: 'array',
+          items: { type: 'string' },
+        },
+      },
+      required: ['task', 'tags'],
+      additionalProperties: false,
+    };
+
+    const result = streamObject({
+      model,
+      temperature: 0,
+      messages: [
+        {
+          role: 'user',
+          content:
+            'Create a task named "Review PR" with status pending and tags ["code", "review"].',
+        },
+      ],
+      schema: jsonSchema(schema),
+    });
+
+    const object = (await result.object) as {
+      task: { name: string; status: string };
+      tags: string[];
+    };
+
+    expect(object).toBeDefined();
+    expect(object.task).toBeDefined();
+    expect(typeof object.task.name).toBe('string');
+    expect(['pending', 'done']).toContain(object.task.status);
+    expect(Array.isArray(object.tags)).toBe(true);
+  });
+});