feat: add Gemini third-party image provider

settings/providers:
- add a Google Gemini (Third-party API) media preset and match custom Gemini base URLs back to that preset
- keep official Google Gemini (Image) behavior unchanged for the default Google endpoint

runtime/tests:
- forward gemini-image provider base_url into createGoogleGenerativeAI in image-generator
- add regression tests for preset matching and image provider config resolution

Author: jingyang.jiang

src/__tests__/unit/image-generator.test.ts

@@ -0,0 +1,29 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import { resolveGeminiImageProviderConfig } from '../../lib/image-generator';
+
+describe('image-generator provider config', () => {
+  it('forwards custom base URL to Google SDK config', () => {
+    const config = resolveGeminiImageProviderConfig({
+      api_key: 'gemini-key',
+      base_url: 'https://proxy.example.com/google/v1beta',
+      extra_env: '{"GEMINI_IMAGE_MODEL":"gemini-3-pro-image-preview"}',
+    });
+
+    assert.equal(config.apiKey, 'gemini-key');
+    assert.equal(config.baseURL, 'https://proxy.example.com/google/v1beta');
+    assert.equal(config.model, 'gemini-3-pro-image-preview');
+  });
+
+  it('falls back to default model and omits empty base URL', () => {
+    const config = resolveGeminiImageProviderConfig({
+      api_key: 'gemini-key',
+      base_url: '',
+      extra_env: '{}',
+    });
+
+    assert.equal(config.apiKey, 'gemini-key');
+    assert.equal(config.baseURL, undefined);
+    assert.equal(config.model, 'gemini-3.1-flash-image-preview');
+  });
+});

src/__tests__/unit/provider-presets.test.ts

@@ -0,0 +1,48 @@
+import { describe, it } from 'node:test';
+import assert from 'node:assert/strict';
+import fs from 'fs';
+import path from 'path';
+import {
+  VENDOR_PRESETS,
+  findPresetForLegacy,
+} from '../../lib/provider-catalog';
+
+const providerPresetsSource = fs.readFileSync(
+  path.join(process.cwd(), 'src/components/settings/provider-presets.tsx'),
+  'utf-8',
+);
+
+describe('Gemini image third-party provider wiring', () => {
+  it('adds a Gemini third-party media preset to the vendor catalog', () => {
+    const preset = VENDOR_PRESETS.find(p => p.key === 'gemini-image-thirdparty');
+    assert.ok(preset, 'gemini-image-thirdparty preset not found in vendor catalog');
+    assert.equal(preset?.protocol, 'gemini-image');
+    assert.equal(preset?.category, 'media');
+    assert.ok(preset?.fields.includes('base_url'), 'third-party catalog preset should expose base_url');
+  });
+
+  it('matches gemini-image custom base URLs to the third-party preset', () => {
+    const preset = findPresetForLegacy('https://proxy.example.com/google/v1beta', 'gemini-image');
+    assert.ok(preset);
+    assert.equal(preset.key, 'gemini-image-thirdparty');
+  });
+
+  it('quick preset source includes Gemini third-party entry with base_url field', () => {
+    assert.match(providerPresetsSource, /key:\s*"gemini-image-thirdparty"/);
+    assert.match(providerPresetsSource, /name:\s*"Google Gemini \(Third-party API\)"/);
+    assert.match(providerPresetsSource, /provider_type:\s*"gemini-image"/);
+    assert.match(providerPresetsSource, /category:\s*"media"/);
+    assert.match(providerPresetsSource, /fields:\s*\["api_key",\s*"base_url"\]/);
+  });
+
+  it('quick preset matcher routes custom gemini-image URLs to the third-party preset', () => {
+    assert.match(
+      providerPresetsSource,
+      /provider\.provider_type === "gemini-image" && provider\.base_url === "https:\/\/generativelanguage\.googleapis\.com\/v1beta"/,
+    );
+    assert.match(
+      providerPresetsSource,
+      /provider\.provider_type === "gemini-image" && provider\.base_url[\s\S]*gemini-image-thirdparty/,
+    );
+  });
+});

src/components/settings/provider-presets.tsx

@@ -278,6 +278,19 @@ export const QUICK_PRESETS: QuickPreset[] = [
     fields: ["api_key"],
     category: "media",
   },
+  {
+    key: "gemini-image-thirdparty",
+    name: "Google Gemini (Third-party API)",
+    description: "Gemini image API via a third-party compatible endpoint",
+    descriptionZh: "通过第三方兼容端点接入 Gemini 图片 API",
+    icon: <Google size={18} />,
+    provider_type: "gemini-image",
+    protocol: "gemini-image",
+    base_url: "",
+    extra_env: '{"GEMINI_API_KEY":""}',
+    fields: ["api_key", "base_url"],
+    category: "media",
+  },
 ];
 
 // ---------------------------------------------------------------------------
@@ -315,6 +328,12 @@ export function findMatchingPreset(provider: ApiProvider): QuickPreset | undefin
   if (provider.provider_type === "bedrock") return QUICK_PRESETS.find(p => p.key === "bedrock");
   if (provider.provider_type === "vertex") return QUICK_PRESETS.find(p => p.key === "vertex");
   if (provider.provider_type === "openrouter") return QUICK_PRESETS.find(p => p.key === "openrouter");
+  if (provider.provider_type === "gemini-image" && provider.base_url === "https://generativelanguage.googleapis.com/v1beta") {
+    return QUICK_PRESETS.find(p => p.key === "gemini-image");
+  }
+  if (provider.provider_type === "gemini-image" && provider.base_url) {
+    return QUICK_PRESETS.find(p => p.key === "gemini-image-thirdparty");
+  }
   if (provider.provider_type === "gemini-image") return QUICK_PRESETS.find(p => p.key === "gemini-image");
   if (provider.provider_type === "anthropic" && provider.base_url === "https://api.anthropic.com") {
     return QUICK_PRESETS.find(p => p.key === "anthropic-official");

src/lib/image-generator.ts

@@ -26,6 +26,32 @@ export interface GenerateSingleImageResult {
   elapsedMs: number;
 }
 
+interface GeminiImageProviderRecord {
+  api_key: string;
+  base_url?: string;
+  extra_env?: string;
+}
+
+export function resolveGeminiImageProviderConfig(provider: GeminiImageProviderRecord): {
+  apiKey: string;
+  baseURL?: string;
+  model: string;
+} {
+  let configuredModel = 'gemini-3.1-flash-image-preview';
+  try {
+    const env = JSON.parse(provider.extra_env || '{}');
+    if (env.GEMINI_IMAGE_MODEL) configuredModel = env.GEMINI_IMAGE_MODEL;
+  } catch {
+    // keep default model when extra_env is missing or invalid
+  }
+
+  return {
+    apiKey: provider.api_key,
+    baseURL: provider.base_url?.trim() || undefined,
+    model: configuredModel,
+  };
+}
+
 /**
  * Shared image generation function.
  * Handles: Provider lookup → Gemini API call → file save → project dir copy → DB record.
@@ -35,25 +61,21 @@ export async function generateSingleImage(params: GenerateSingleImageParams): Pr
 
   const db = getDb();
   const provider = db.prepare(
-    "SELECT api_key, extra_env FROM api_providers WHERE provider_type = 'gemini-image' AND api_key != '' LIMIT 1"
-  ).get() as { api_key: string; extra_env?: string } | undefined;
+    "SELECT api_key, base_url, extra_env FROM api_providers WHERE provider_type = 'gemini-image' AND api_key != '' ORDER BY sort_order ASC, created_at ASC LIMIT 1"
+  ).get() as GeminiImageProviderRecord | undefined;
 
   if (!provider) {
     throw new Error('No Gemini Image provider configured. Please add a provider with type "gemini-image" in Settings.');
   }
 
-  // Read configured model from extra_env, fall back to default
-  let configuredModel = 'gemini-3.1-flash-image-preview';
-  try {
-    const env = JSON.parse(provider.extra_env || '{}');
-    if (env.GEMINI_IMAGE_MODEL) configuredModel = env.GEMINI_IMAGE_MODEL;
-  } catch { /* use default */ }
-
-  const requestedModel = params.model || configuredModel;
+  const providerConfig = resolveGeminiImageProviderConfig(provider);
+  const requestedModel = params.model || providerConfig.model;
   const aspectRatio = (params.aspectRatio || '1:1') as `${number}:${number}`;
   const imageSize = params.imageSize || '1K';
-
-  const google = createGoogleGenerativeAI({ apiKey: provider.api_key });
+  const google = createGoogleGenerativeAI({
+    apiKey: providerConfig.apiKey,
+    baseURL: providerConfig.baseURL,
+  });
 
   // Build prompt: plain string or { text, images } for reference images
   // Combine both base64 data and file paths — both can be provided simultaneously

src/lib/provider-catalog.ts

@@ -438,6 +438,26 @@ export const VENDOR_PRESETS: VendorPreset[] = [
     iconKey: 'google',
   },
 
+  // ── Google Gemini (Third-party API) ──
+  {
+    key: 'gemini-image-thirdparty',
+    name: 'Google Gemini (Third-party API)',
+    description: 'Gemini image API via a third-party compatible endpoint',
+    descriptionZh: '通过第三方兼容端点接入 Gemini 图片 API',
+    protocol: 'gemini-image',
+    authStyle: 'api_key',
+    baseUrl: '',
+    defaultEnvOverrides: { GEMINI_API_KEY: '' },
+    defaultModels: [
+      { modelId: 'gemini-3.1-flash-image-preview', displayName: 'Nano Banana 2' },
+      { modelId: 'gemini-3-pro-image-preview', displayName: 'Nano Banana Pro' },
+      { modelId: 'gemini-2.5-flash-image', displayName: 'Nano Banana' },
+    ],
+    fields: ['api_key', 'base_url'],
+    category: 'media',
+    iconKey: 'google',
+  },
+
   // ── Custom API (OpenAI-compatible) ──
   {
     key: 'custom-openai',
@@ -556,7 +576,11 @@ export function findPresetForLegacy(baseUrl: string, providerType: string, proto
   if (providerType === 'bedrock') return VENDOR_PRESETS.find(p => p.key === 'bedrock');
   if (providerType === 'vertex') return VENDOR_PRESETS.find(p => p.key === 'vertex');
   if (providerType === 'openrouter') return VENDOR_PRESETS.find(p => p.key === 'openrouter');
-  if (providerType === 'gemini-image') return VENDOR_PRESETS.find(p => p.key === 'gemini-image');
+  if (providerType === 'gemini-image') {
+    return VENDOR_PRESETS.find(
+      p => p.key === (baseUrl === 'https://generativelanguage.googleapis.com/v1beta' ? 'gemini-image' : 'gemini-image-thirdparty'),
+    );
+  }
   if (providerType === 'anthropic' && baseUrl === 'https://api.anthropic.com') {
     return VENDOR_PRESETS.find(p => p.key === 'anthropic-official');
   }