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feat(ai-gemini): add support for Gemini 3.1 Flash Lite Preview model #351

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feat(ai-gemini): add support for Gemini 3.1 Flash Lite Preview model #351

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1c8e2d7
feat: add support for gemini 3.1 flash-lite
NachoVazquez Mar 7, 2026
c138b57
chore: generate changeset
NachoVazquez Mar 8, 2026
e982818
feat(ai-gemini): add support for Gemini 3.1 Flash Lite Preview model
NachoVazquez Mar 8, 2026
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18 changes: 18 additions & 0 deletions .changeset/fluffy-rats-worry.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
---
'@tanstack/ai-gemini': minor
---

feat: add support for Gemini 3.1 Flash Lite Preview model

Added `gemini-3.1-flash-lite-preview` to the Gemini adapter with:

- Full multimodal support (text, image, audio, video, document)
- Thinking and structured output capabilities
- Available for summarization tasks
- Comprehensive type tests

Model specs:

- 1M input tokens, 65K output tokens
- $0.25/1M input, $1.50/1M output pricing
- Knowledge cutoff: 2025-01-01
1 change: 1 addition & 0 deletions packages/typescript/ai-gemini/src/adapters/summarize.ts
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Expand Up @@ -21,6 +21,7 @@ export interface GeminiSummarizeConfig extends GeminiClientConfig {}
* Available Gemini models for summarization
*/
export const GeminiSummarizeModels = [
'gemini-3.1-flash-lite-preview',
'gemini-2.0-flash',
'gemini-1.5-flash',
'gemini-1.5-pro',
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45 changes: 45 additions & 0 deletions packages/typescript/ai-gemini/src/model-meta.ts
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Expand Up @@ -228,6 +228,43 @@ const GEMINI_3_1_FLASH_IMAGE = {
GeminiThinkingOptions
>

const GEMINI_3_1_FLASH_LITE = {
name: 'gemini-3.1-flash-lite-preview',
max_input_tokens: 1_048_576,
max_output_tokens: 65_536,
knowledge_cutoff: '2025-01-01',
supports: {
input: ['text', 'image', 'audio', 'video', 'document'],
output: ['text'],
capabilities: [
'batch_api',
'caching',
'code_execution',
'file_search',
'function_calling',
'search_grounding',
'structured_output',
'thinking',
'url_context',
],
},
pricing: {
input: {
normal: 0.25,
},
output: {
normal: 1.5,
},
},
} as const satisfies ModelMeta<
GeminiToolConfigOptions &
GeminiSafetyOptions &
GeminiCommonConfigOptions &
GeminiCachedContentOptions &
GeminiStructuredOutputOptions &
GeminiThinkingOptions
>

const GEMINI_2_5_PRO = {
name: 'gemini-2.5-pro',
max_input_tokens: 1_048_576,
Expand Down Expand Up @@ -894,6 +931,7 @@ export const GEMINI_MODELS = [
GEMINI_3_1_PRO.name,
GEMINI_3_PRO.name,
GEMINI_3_FLASH.name,
GEMINI_3_1_FLASH_LITE.name,
GEMINI_2_5_PRO.name,
GEMINI_2_5_FLASH.name,
GEMINI_2_5_FLASH_PREVIEW.name,
Expand Down Expand Up @@ -1005,6 +1043,12 @@ export type GeminiChatModelProviderOptionsByName = {
GeminiStructuredOutputOptions &
GeminiThinkingOptions &
GeminiThinkingAdvancedOptions
[GEMINI_3_1_FLASH_LITE.name]: GeminiToolConfigOptions &
GeminiSafetyOptions &
GeminiCommonConfigOptions &
GeminiCachedContentOptions &
GeminiStructuredOutputOptions &
GeminiThinkingOptions
[GEMINI_2_5_PRO.name]: GeminiToolConfigOptions &
GeminiSafetyOptions &
GeminiCommonConfigOptions &
Expand Down Expand Up @@ -1066,6 +1110,7 @@ export type GeminiModelInputModalitiesByName = {
[GEMINI_3_1_PRO.name]: typeof GEMINI_3_1_PRO.supports.input
[GEMINI_3_PRO.name]: typeof GEMINI_3_PRO.supports.input
[GEMINI_3_FLASH.name]: typeof GEMINI_3_FLASH.supports.input
[GEMINI_3_1_FLASH_LITE.name]: typeof GEMINI_3_1_FLASH_LITE.supports.input
[GEMINI_2_5_PRO.name]: typeof GEMINI_2_5_PRO.supports.input
[GEMINI_2_5_FLASH_LITE.name]: typeof GEMINI_2_5_FLASH_LITE.supports.input
[GEMINI_2_5_FLASH_LITE_PREVIEW.name]: typeof GEMINI_2_5_FLASH_LITE_PREVIEW.supports.input
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54 changes: 54 additions & 0 deletions packages/typescript/ai-gemini/tests/model-meta.test.ts
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Expand Up @@ -151,6 +151,28 @@ describe('Gemini Model Provider Options Type Assertions', () => {
// Should have base options
expectTypeOf<Options>().toExtend<BaseOptions>()
})

it('gemini-3.1-flash-lite-preview should support thinking options', () => {
type Model = 'gemini-3.1-flash-lite-preview'
type Options = GeminiChatModelProviderOptionsByName[Model]

// Should have thinking options
expectTypeOf<Options>().toExtend<GeminiThinkingOptions>()

// Should have structured output options
expectTypeOf<Options>().toExtend<GeminiStructuredOutputOptions>()

// Should have base options
expectTypeOf<Options>().toExtend<BaseOptions>()

// Verify specific properties exist
expectTypeOf<Options>().toHaveProperty('generationConfig')
expectTypeOf<Options>().toHaveProperty('safetySettings')
expectTypeOf<Options>().toHaveProperty('toolConfig')
expectTypeOf<Options>().toHaveProperty('cachedContent')
expectTypeOf<Options>().toHaveProperty('responseMimeType')
expectTypeOf<Options>().toHaveProperty('responseSchema')
})
})

describe('Models WITHOUT thinking support', () => {
Expand Down Expand Up @@ -195,6 +217,7 @@ describe('Gemini Model Provider Options Type Assertions', () => {

expectTypeOf<'gemini-3-pro-preview'>().toExtend<Keys>()
expectTypeOf<'gemini-3-flash-preview'>().toExtend<Keys>()
expectTypeOf<'gemini-3.1-flash-lite-preview'>().toExtend<Keys>()
expectTypeOf<'gemini-2.5-pro'>().toExtend<Keys>()
expectTypeOf<'gemini-2.5-flash'>().toExtend<Keys>()
expectTypeOf<'gemini-2.5-flash-preview-09-2025'>().toExtend<Keys>()
Expand Down Expand Up @@ -244,6 +267,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.5-flash-lite-preview-09-2025']
>().toHaveProperty('safetySettings')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-3.1-flash-lite-preview']
>().toHaveProperty('safetySettings')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.0-flash']
>().toHaveProperty('safetySettings')
Expand Down Expand Up @@ -274,6 +300,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.5-flash-lite-preview-09-2025']
>().toHaveProperty('toolConfig')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-3.1-flash-lite-preview']
>().toHaveProperty('toolConfig')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.0-flash']
>().toHaveProperty('toolConfig')
Expand Down Expand Up @@ -304,6 +333,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.5-flash-lite-preview-09-2025']
>().toHaveProperty('cachedContent')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-3.1-flash-lite-preview']
>().toHaveProperty('cachedContent')
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.0-flash']
>().toHaveProperty('cachedContent')
Expand Down Expand Up @@ -336,6 +368,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.5-flash-lite-preview-09-2025']
>().toExtend<GeminiThinkingOptions>()
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-3.1-flash-lite-preview']
>().toExtend<GeminiThinkingOptions>()
})

it('models without thinking should NOT extend GeminiThinkingOptions', () => {
Expand Down Expand Up @@ -369,6 +404,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.5-flash-lite-preview-09-2025']
>().toExtend<GeminiStructuredOutputOptions>()
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-3.1-flash-lite-preview']
>().toExtend<GeminiStructuredOutputOptions>()
expectTypeOf<
GeminiChatModelProviderOptionsByName['gemini-2.0-flash']
>().toExtend<GeminiStructuredOutputOptions>()
Expand All @@ -387,7 +425,9 @@ describe('Gemini Model Provider Options Type Assertions', () => {
*
* Models with full multimodal (text + image + audio + video + document):
* - gemini-3-pro-preview
* - gemini-3-flash-preview
* - gemini-2.5-pro
* - gemini-3.1-flash-lite-preview
* - gemini-2.5-flash-lite (and preview)
*
* Models with limited multimodal (text + image + audio + video, NO document):
Expand Down Expand Up @@ -439,6 +479,20 @@ describe('Gemini Model Input Modality Type Assertions', () => {
})
})

describe('gemini-3.1-flash-lite-preview (full multimodal)', () => {
type Modalities =
GeminiModelInputModalitiesByName['gemini-3.1-flash-lite-preview']
type Message = ConstrainedModelMessage<Modalities>

it('should allow all content part types', () => {
expectTypeOf<MessageWithContent<TextPart>>().toExtend<Message>()
expectTypeOf<MessageWithContent<ImagePart>>().toExtend<Message>()
expectTypeOf<MessageWithContent<AudioPart>>().toExtend<Message>()
expectTypeOf<MessageWithContent<VideoPart>>().toExtend<Message>()
expectTypeOf<MessageWithContent<DocumentPart>>().toExtend<Message>()
})
})

describe('gemini-2.5-flash-lite (full multimodal)', () => {
type Modalities = GeminiModelInputModalitiesByName['gemini-2.5-flash-lite']
type Message = ConstrainedModelMessage<Modalities>
Expand Down