fix(ai-gemini): allow native image generation with store: false

.changeset/gemini-image-store-false.md

@@ -0,0 +1,5 @@
+---
+'@tanstack/ai-gemini': patch
+---
+
+Native Gemini image generation no longer throws `image interaction returned no id.` when `modelOptions.store` is `false`. Gemini leaves the interaction id out of an unstored interaction, so the result gets a local id, which cannot be passed as `previous_interaction_id`. A stored interaction without an id still throws.

docs/media/image-generation.md

@@ -227,7 +227,7 @@ const edited = await generateImage({
 
 Rules for the edit:
 
-- Leave `store` unset. The API default is `true`. If you set `store` to `false`, a later call cannot use that id.
+- Leave `store` unset. The API default is `true`. If you set `store` to `false`, Gemini does not keep the interaction, so `id` is a local id and a later call cannot use it as `previous_interaction_id`.
 - A free tier keeps a stored interaction for 1 day. A paid tier keeps it for 55 days.
 - If the edit needs a new reference image, add that image part on this call. Do not send the image from `first` again.
 

packages/ai-gemini/src/adapters/image.ts

@@ -4,7 +4,11 @@ import {
   resolveMediaPrompt,
 } from '@tanstack/ai'
 import { BaseImageAdapter } from '@tanstack/ai/adapters'
-import { createGeminiClient, getGeminiApiKeyFromEnv } from '../utils'
+import {
+  createGeminiClient,
+  generateId,
+  getGeminiApiKeyFromEnv,
+} from '../utils'
 import { flattenModalityTokenCounts, hasModalityTokens } from '../usage'
 import {
   parseNativeImageSize,
@@ -196,7 +200,11 @@ export class GeminiImageAdapter<
         })
       : await this.client.interactions.create(request)
 
-    return this.transformInteractionResponse(model, interaction)
+    return this.transformInteractionResponse(
+      model,
+      interaction,
+      modelOptions?.store !== false,
+    )
   }
 
   /**
@@ -261,13 +269,17 @@ export class GeminiImageAdapter<
   private transformInteractionResponse(
     model: string,
     interaction: Interactions.Interaction,
+    stored: boolean,
   ): ImageGenerationResult {
     if (interaction.status !== 'completed') {
       throw new Error(
         `Gemini ${model} image interaction ended with status "${interaction.status}".`,
       )
     }
-    if (!interaction.id) {
+    // The interaction id only matters for chaining an edit through
+    // `previous_interaction_id`, and an unstored interaction cannot be chained.
+    // Gemini leaves the id out when `store` is false, so use a local one.
+    if (!interaction.id && stored) {
       throw new Error(`Gemini ${model} image interaction returned no id.`)
     }
 
@@ -302,7 +314,7 @@ export class GeminiImageAdapter<
 
     const usage = interactionImageUsage(interaction.usage)
     return {
-      id: interaction.id,
+      id: interaction.id ?? generateId(this.name),
       model,
       images,
       ...(usage ? { usage } : {}),

packages/ai-gemini/tests/image-adapter.test.ts

@@ -627,6 +627,47 @@ describe('Gemini Image Adapter', () => {
       expect(result.id).toBe('int_test')
     })
 
+    it('returns the images with a local id when store is false and Gemini returns no interaction id', async () => {
+      const mockCreate = vi
+        .fn()
+        .mockResolvedValueOnce(interactionWithImages('out', { id: undefined }))
+      const adapter = createGeminiImage(
+        'gemini-3.1-flash-image',
+        'test-api-key',
+      )
+      stubCreate(adapter, mockCreate)
+
+      const result = await generateImage({
+        threadId: 'thread-1',
+        adapter,
+        prompt: 'A red apple',
+        modelOptions: { store: false },
+      })
+
+      expect(result.images).toHaveLength(1)
+      expect(result.id).toEqual(expect.any(String))
+      expect(result.id).not.toBe('')
+    })
+
+    it('still throws when a stored interaction comes back without an id', async () => {
+      const mockCreate = vi
+        .fn()
+        .mockResolvedValueOnce(interactionWithImages('out', { id: undefined }))
+      const adapter = createGeminiImage(
+        'gemini-3.1-flash-image',
+        'test-api-key',
+      )
+      stubCreate(adapter, mockCreate)
+
+      await expect(
+        generateImage({
+          threadId: 'thread-1',
+          adapter,
+          prompt: 'A red apple',
+        }),
+      ).rejects.toThrow(/returned no id/)
+    })
+
     it('passes abortSignal only when one is set', async () => {
       const { adapter, mockCreate } = mockedNativeAdapter()
       const controller = new AbortController()