feat: Add Zhipu (智谱) image generation provider

tests/providers/test_image_generation.py

@@ -18,6 +18,7 @@ from nanobot.providers.image_generation import (
     OpenAIImageGenerationClient,
     OpenRouterImageGenerationClient,
     StepFunImageGenerationClient,
+    ZhipuImageGenerationClient,
 )
 
 PNG_BYTES = (
@@ -1027,3 +1028,102 @@ async def test_openai_no_images_raises() -> None:
 
     with pytest.raises(ImageGenerationError, match="returned no images"):
         await client.generate(prompt="draw", model="dall-e-3")
+
+
+# ---------------------------------------------------------------------------
+# Zhipu
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_payload_and_response() -> None:
+    fake = FakeClient(FakeResponse({"data": [{"url": "https://cdn.example/image.png"}]}))
+    fake.get_response = FakeResponse({}, content=PNG_BYTES)
+    client = ZhipuImageGenerationClient(
+        api_key="sk-zhipu-test",
+        api_base="https://open.bigmodel.cn/api/paas/v4",
+        extra_headers={"X-Test": "1"},
+        extra_body={"watermark_enabled": False},
+        client=fake,  # type: ignore[arg-type]
+    )
+
+    response = await client.generate(
+        prompt="a sunset over the ocean",
+        model="glm-image",
+        aspect_ratio="16:9",
+        image_size="2K",
+    )
+
+    assert response.images[0].startswith("data:image/png;base64,")
+    call = fake.calls[0]
+    assert call["url"] == "https://open.bigmodel.cn/api/paas/v4/images/generations"
+    assert call["headers"]["Authorization"] == "Bearer sk-zhipu-test"
+    assert call["headers"]["X-Test"] == "1"
+    body = call["json"]
+    assert body["model"] == "glm-image"
+    assert body["prompt"] == "a sunset over the ocean"
+    assert body["size"] == "1728x960"
+    assert body["watermark_enabled"] is False
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_with_explicit_size() -> None:
+    fake = FakeClient(FakeResponse({"data": [{"url": "https://cdn.example/image.png"}]}))
+    fake.get_response = FakeResponse({}, content=PNG_BYTES)
+    client = ZhipuImageGenerationClient(
+        api_key="sk-zhipu-test",
+        client=fake,  # type: ignore[arg-type]
+    )
+
+    await client.generate(
+        prompt="a cat",
+        model="cogview-4",
+        image_size="1024x1024",
+    )
+
+    body = fake.calls[0]["json"]
+    assert body["size"] == "1024x1024"
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_downloads_url_response() -> None:
+    fake = FakeClient(FakeResponse({"data": [{"url": "https://cdn.example/image.png"}]}))
+    fake.get_response = FakeResponse({}, content=PNG_BYTES)
+    client = ZhipuImageGenerationClient(
+        api_key="sk-zhipu-test",
+        client=fake,  # type: ignore[arg-type]
+    )
+
+    response = await client.generate(prompt="draw", model="glm-image")
+
+    assert response.images[0].startswith("data:image/png;base64,")
+    assert fake.get_calls[0]["url"] == "https://cdn.example/image.png"
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_requires_api_key() -> None:
+    client = ZhipuImageGenerationClient(api_key=None)
+
+    with pytest.raises(ImageGenerationError, match="API key"):
+        await client.generate(prompt="draw", model="glm-image")
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_no_images_raises() -> None:
+    fake = FakeClient(FakeResponse({"data": [{"text": "sorry"}]}))
+    client = ZhipuImageGenerationClient(api_key="sk-zhipu-test", client=fake)  # type: ignore[arg-type]
+
+    with pytest.raises(ImageGenerationError, match="returned no images"):
+        await client.generate(prompt="draw", model="glm-image")
+
+
+@pytest.mark.asyncio
+async def test_zhipu_image_generation_rejects_reference_images() -> None:
+    client = ZhipuImageGenerationClient(api_key="sk-zhipu-test")
+
+    with pytest.raises(ImageGenerationError, match="reference images"):
+        await client.generate(
+            prompt="edit this",
+            model="glm-image",
+            reference_images=["ref.png"],
+        )