test: add regression test for issue #181 (tool response for image) (#371)

* test: add regression test for issue #181 (tool response for image)

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

* test: add image-data type test case for issue #181

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

* test: use exact format from original issue #181 (type: media)

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

* test: use AI SDK v3 file-data format for issue #181 regression test

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

* test: remove root cause analysis from issue #181 test comments

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/cold-kiwis-admire.md

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+---
+---

e2e/issues/issue-181-tool-response-image.test.ts

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+/**
+ * Regression test for GitHub issue #181
+ * https://github.com/OpenRouterTeam/ai-sdk-provider/issues/181
+ *
+ * Issue: "tool response for image not working"
+ *
+ * Reported behavior: When a tool returns an image in its response using the AI SDK's
+ * toModelOutput with multimodal content, the model cannot view or interpret the image.
+ *
+ * Observed behavior: Tool results with multimodal content (images) are JSON.stringified.
+ */
+import { describe, expect, it } from 'vitest';
+import { convertToOpenRouterChatMessages } from '@/src/chat/convert-to-openrouter-chat-messages';
+
+describe('Issue #181: Tool response for image not working', () => {
+  it('should stringify tool result with content type containing image', () => {
+    const result = convertToOpenRouterChatMessages([
+      {
+        role: 'tool',
+        content: [
+          {
+            type: 'tool-result',
+            toolCallId: 'call-123',
+            toolName: 'screenshot_tool',
+            output: {
+              type: 'content',
+              value: [
+                {
+                  type: 'text',
+                  text: 'Here is the screenshot:',
+                },
+                {
+                  type: 'file-data',
+                  data: 'iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+M9QDwADhgGAWjR9awAAAABJRU5ErkJggg==',
+                  mediaType: 'image/png',
+                },
+              ],
+            },
+          },
+        ],
+      },
+    ]);
+
+    expect(result).toHaveLength(1);
+    expect(result[0]).toMatchObject({
+      role: 'tool',
+      tool_call_id: 'call-123',
+    });
+
+    expect(typeof result[0]?.content).toBe('string');
+
+    const content = result[0]?.content as string;
+    expect(content).toContain('"type":"text"');
+    expect(content).toContain('"type":"file-data"');
+    expect(content).toContain('iVBORw0KGgo'); // Base64 image data
+  });
+
+  it('should stringify tool result with content type containing image URL', () => {
+    const result = convertToOpenRouterChatMessages([
+      {
+        role: 'tool',
+        content: [
+          {
+            type: 'tool-result',
+            toolCallId: 'call-456',
+            toolName: 'image_generator',
+            output: {
+              type: 'content',
+              value: [
+                {
+                  type: 'text',
+                  text: 'Generated image:',
+                },
+                {
+                  type: 'file-url',
+                  url: 'https://example.com/generated-image.png',
+                },
+              ],
+            },
+          },
+        ],
+      },
+    ]);
+
+    expect(result).toHaveLength(1);
+    expect(typeof result[0]?.content).toBe('string');
+
+    const content = result[0]?.content as string;
+    expect(content).toContain('"type":"file-url"');
+    expect(content).toContain('https://example.com/generated-image.png');
+  });
+
+  it('should handle text-only tool results normally', () => {
+    const result = convertToOpenRouterChatMessages([
+      {
+        role: 'tool',
+        content: [
+          {
+            type: 'tool-result',
+            toolCallId: 'call-789',
+            toolName: 'calculator',
+            output: {
+              type: 'text',
+              value: 'The result is 42',
+            },
+          },
+        ],
+      },
+    ]);
+
+    expect(result).toHaveLength(1);
+    expect(result[0]).toMatchObject({
+      role: 'tool',
+      tool_call_id: 'call-789',
+      content: 'The result is 42',
+    });
+  });
+
+  it('should handle JSON tool results normally', () => {
+    const result = convertToOpenRouterChatMessages([
+      {
+        role: 'tool',
+        content: [
+          {
+            type: 'tool-result',
+            toolCallId: 'call-abc',
+            toolName: 'weather_api',
+            output: {
+              type: 'json',
+              value: { temperature: 72, unit: 'F', location: 'San Francisco' },
+            },
+          },
+        ],
+      },
+    ]);
+
+    expect(result).toHaveLength(1);
+    expect(result[0]).toMatchObject({
+      role: 'tool',
+      tool_call_id: 'call-abc',
+    });
+
+    const content = result[0]?.content as string;
+    expect(content).toBe(
+      '{"temperature":72,"unit":"F","location":"San Francisco"}',
+    );
+  });
+
+  it('should stringify tool result with file-data type (reproduces issue #181)', () => {
+    // Reproduces issue #181 using AI SDK v3 format (file-data instead of V2's media type)
+    const result = convertToOpenRouterChatMessages([
+      {
+        role: 'tool',
+        content: [
+          {
+            type: 'tool-result',
+            toolCallId: 'call-original-issue',
+            toolName: 'webFetch',
+            output: {
+              type: 'content',
+              value: [
+                {
+                  type: 'file-data',
+                  mediaType: 'image/jpeg',
+                  // Truncated JPEG from the original issue
+                  data: '/9j/4AAQSkZJRgABAQAAAQABAAD/2wCEAAkGBwgHBgkIBwgKCgkLDRYPDQwMDRsUFRAWIB0iIiAdHx8kKDQsJCYxJx8fLT0tMTU3Ojo6Iys/RD84QzQ5OjcBCgoKDQwNGg8PGjclHyU3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3Nzc3N//AABEIAFgAXAMBIgACEQEDEQH/xAAcAAACAgMBAQAA',
+                },
+              ],
+            },
+          },
+        ],
+      },
+    ]);
+
+    expect(result).toHaveLength(1);
+    expect(result[0]).toMatchObject({
+      role: 'tool',
+      tool_call_id: 'call-original-issue',
+    });
+
+    expect(typeof result[0]?.content).toBe('string');
+
+    const content = result[0]?.content as string;
+    expect(content).toContain('"type":"file-data"');
+    expect(content).toContain('"mediaType":"image/jpeg"');
+    expect(content).toContain('/9j/4AAQSkZJRgABAQAAAQABAAD'); // JPEG magic bytes
+  });
+});