feat(ai): Add thinking levels parameter

.changeset/plenty-bulldogs-complain.md

@@ -0,0 +1,6 @@
+---
+'@firebase/ai': minor
+'firebase': minor
+---
+
+Added ability to specify thinking levels in `thinkingConfig`.

common/api-review/ai.api.md

@@ -1371,8 +1371,20 @@ export interface TextPart {
 export interface ThinkingConfig {
     includeThoughts?: boolean;
     thinkingBudget?: number;
+    thinkingLevel?: ThinkingLevel;
 }
 
+// @public
+export const ThinkingLevel: {
+    MINIMAL: string;
+    LOW: string;
+    MEDIUM: string;
+    HIGH: string;
+};
+
+// @public
+export type ThinkingLevel = (typeof ThinkingLevel)[keyof typeof ThinkingLevel];
+
 // Warning: (ae-incompatible-release-tags) The symbol "Tool" is marked as @public, but its signature references "CodeExecutionTool" which is marked as @beta
 // Warning: (ae-incompatible-release-tags) The symbol "Tool" is marked as @public, but its signature references "URLContextTool" which is marked as @beta
 //

docs-devsite/ai.md

@@ -176,6 +176,7 @@ The Firebase AI Web SDK.
 |  [POSSIBLE\_ROLES](./ai.md#possible_roles) | Possible roles. |
 |  [ResponseModality](./ai.md#responsemodality) | <b><i>(Public Preview)</i></b> Generation modalities to be returned in generation responses. |
 |  [SchemaType](./ai.md#schematype) | Contains the list of OpenAPI data types as defined by the [OpenAPI specification](https://swagger.io/docs/specification/data-models/data-types/) |
+|  [ThinkingLevel](./ai.md#thinkinglevel) | A preset that controls the model's "thinking" process. Use <code>ThinkingLevel.LOW</code> for faster responses on less complex tasks, and <code>ThinkingLevel.HIGH</code> for better reasoning on more complex tasks. |
 |  [URLRetrievalStatus](./ai.md#urlretrievalstatus) | <b><i>(Public Preview)</i></b> The status of a URL retrieval. |
 
 ## Type Aliases
@@ -208,6 +209,7 @@ The Firebase AI Web SDK.
 |  [ResponseModality](./ai.md#responsemodality) | <b><i>(Public Preview)</i></b> Generation modalities to be returned in generation responses. |
 |  [Role](./ai.md#role) | Role is the producer of the content. |
 |  [SchemaType](./ai.md#schematype) | Contains the list of OpenAPI data types as defined by the [OpenAPI specification](https://swagger.io/docs/specification/data-models/data-types/) |
+|  [ThinkingLevel](./ai.md#thinkinglevel) | A preset that controls the model's "thinking" process. Use <code>ThinkingLevel.LOW</code> for faster responses on less complex tasks, and <code>ThinkingLevel.HIGH</code> for better reasoning on more complex tasks. |
 |  [Tool](./ai.md#tool) | Defines a tool that model can call to access external knowledge. |
 |  [TypedSchema](./ai.md#typedschema) | A type that includes all specific Schema types. |
 |  [URLRetrievalStatus](./ai.md#urlretrievalstatus) | <b><i>(Public Preview)</i></b> The status of a URL retrieval. |
@@ -827,6 +829,21 @@ SchemaType: {
 }
 ```
 
+## ThinkingLevel
+
+A preset that controls the model's "thinking" process. Use `ThinkingLevel.LOW` for faster responses on less complex tasks, and `ThinkingLevel.HIGH` for better reasoning on more complex tasks.
+
+<b>Signature:</b>
+
+```typescript
+ThinkingLevel: {
+    MINIMAL: string;
+    LOW: string;
+    MEDIUM: string;
+    HIGH: string;
+}
+```
+
 ## URLRetrievalStatus
 
 > This API is provided as a preview for developers and may change based on feedback that we receive. Do not use this API in a production environment.
@@ -1142,6 +1159,16 @@ Contains the list of OpenAPI data types as defined by the [OpenAPI specification
 export type SchemaType = (typeof SchemaType)[keyof typeof SchemaType];
 ```
 
+## ThinkingLevel
+
+A preset that controls the model's "thinking" process. Use `ThinkingLevel.LOW` for faster responses on less complex tasks, and `ThinkingLevel.HIGH` for better reasoning on more complex tasks.
+
+<b>Signature:</b>
+
+```typescript
+export type ThinkingLevel = (typeof ThinkingLevel)[keyof typeof ThinkingLevel];
+```
+
 ## Tool
 
 Defines a tool that model can call to access external knowledge.

docs-devsite/ai.thinkingconfig.md

@@ -25,7 +25,8 @@ export interface ThinkingConfig
 |  Property | Type | Description |
 |  --- | --- | --- |
 |  [includeThoughts](./ai.thinkingconfig.md#thinkingconfigincludethoughts) | boolean | Whether to include "thought summaries" in the model's response. |
-|  [thinkingBudget](./ai.thinkingconfig.md#thinkingconfigthinkingbudget) | number | The thinking budget, in tokens.<!-- -->This parameter sets an upper limit on the number of tokens the model can use for its internal "thinking" process. A higher budget may result in higher quality responses for complex tasks but can also increase latency and cost.<!-- -->If you don't specify a budget, the model will determine the appropriate amount of thinking based on the complexity of the prompt.<!-- -->An error will be thrown if you set a thinking budget for a model that does not support this feature or if the specified budget is not within the model's supported range. |
+|  [thinkingBudget](./ai.thinkingconfig.md#thinkingconfigthinkingbudget) | number | The thinking budget, in tokens. |
+|  [thinkingLevel](./ai.thinkingconfig.md#thinkingconfigthinkinglevel) | [ThinkingLevel](./ai.md#thinkinglevel) | If not specified, Gemini will use the model's default dynamic thinking level. |
 
 ## ThinkingConfig.includeThoughts
 
@@ -45,12 +46,34 @@ The thinking budget, in tokens.
 
 This parameter sets an upper limit on the number of tokens the model can use for its internal "thinking" process. A higher budget may result in higher quality responses for complex tasks but can also increase latency and cost.
 
-If you don't specify a budget, the model will determine the appropriate amount of thinking based on the complexity of the prompt.
+The range of supported thinking budget values depends on the model.
+
+<ul> <li>To use the default thinking budget or thinking level for a model, leave this value undefined.</li>
+
+<li>To disable thinking, when supported by the model, set this value to `0`<!-- -->.</li>
+
+<li>To use dynamic thinking, allowing the model to decide on the thinking budget based on the task, set this value to `-1`<!-- -->.</li> </ul>
 
 An error will be thrown if you set a thinking budget for a model that does not support this feature or if the specified budget is not within the model's supported range.
 
+The model will also error if `thinkingLevel` and `thinkingBudget` are both set.
+
 <b>Signature:</b>
 
 ```typescript
 thinkingBudget?: number;
 ```
+
+## ThinkingConfig.thinkingLevel
+
+If not specified, Gemini will use the model's default dynamic thinking level.
+
+Note: The model will error if `thinkingLevel` and `thinkingBudget` are both set.
+
+Important: Gemini 2.5 series models do not support thinking levels; use `thinkingBudget` to set a thinking budget instead.
+
+<b>Signature:</b>
+
+```typescript
+thinkingLevel?: ThinkingLevel;
+```

packages/ai/src/models/generative-model.test.ts

@@ -21,7 +21,8 @@ import {
   AI,
   InferenceMode,
   AIErrorCode,
-  ChromeAdapter
+  ChromeAdapter,
+  ThinkingLevel
 } from '../public-types';
 import * as request from '../requests/request';
 import { SinonStub, match, restore, stub } from 'sinon';
@@ -53,6 +54,20 @@ const fakeAI: AI = {
 };
 
 describe('GenerativeModel', () => {
+  it('throws if generationConfig is invalid', () => {
+    expect(
+      () =>
+        new GenerativeModel(fakeAI, {
+          model: 'my-model',
+          generationConfig: {
+            thinkingConfig: {
+              thinkingBudget: 1000,
+              thinkingLevel: ThinkingLevel.LOW
+            }
+          }
+        })
+    ).to.throw(AIErrorCode.UNSUPPORTED);
+  });
   it('passes params through to generateContent', async () => {
     const genModel = new GenerativeModel(
       fakeAI,

packages/ai/src/models/generative-model.ts

@@ -41,9 +41,10 @@ import {
   formatGenerateContentInput,
   formatSystemInstruction
 } from '../requests/request-helpers';
-import { AI } from '../public-types';
+import { AI, AIErrorCode } from '../public-types';
 import { AIModel } from './ai-model';
 import { ChromeAdapter } from '../types/chrome-adapter';
+import { AIError } from '../errors';
 
 /**
  * Class for generative model APIs.
@@ -65,6 +66,7 @@ export class GenerativeModel extends AIModel {
   ) {
     super(ai, modelParams.model);
     this.generationConfig = modelParams.generationConfig || {};
+    validateGenerationConfig(this.generationConfig);
     this.safetySettings = modelParams.safetySettings || [];
     this.tools = modelParams.tools;
     this.toolConfig = modelParams.toolConfig;
@@ -165,3 +167,20 @@ export class GenerativeModel extends AIModel {
     );
   }
 }
+
+/**
+ * Client-side validation of some common `GenerationConfig` pitfalls, in order
+ * to save the developer a wasted request.
+ */
+function validateGenerationConfig(generationConfig: GenerationConfig): void {
+  if (
+    // != allows for null and undefined. 0 is considered "set" by the model
+    generationConfig.thinkingConfig?.thinkingBudget != null &&
+    generationConfig.thinkingConfig?.thinkingLevel
+  ) {
+    throw new AIError(
+      AIErrorCode.UNSUPPORTED,
+      `Cannot set both thinkingBudget and thinkingLevel in a config.`
+    );
+  }
+}

packages/ai/src/types/enums.ts

@@ -432,3 +432,26 @@ export const Language = {
  * @beta
  */
 export type Language = (typeof Language)[keyof typeof Language];
+
+/**
+ * A preset that controls the model's "thinking" process. Use
+ * `ThinkingLevel.LOW` for faster responses on less complex tasks, and
+ * `ThinkingLevel.HIGH` for better reasoning on more complex tasks.
+ *
+ * @public
+ */
+export const ThinkingLevel = {
+  MINIMAL: 'MINIMAL',
+  LOW: 'LOW',
+  MEDIUM: 'MEDIUM',
+  HIGH: 'HIGH'
+};
+
+/**
+ * A preset that controls the model's "thinking" process. Use
+ * `ThinkingLevel.LOW` for faster responses on less complex tasks, and
+ * `ThinkingLevel.HIGH` for better reasoning on more complex tasks.
+ *
+ * @public
+ */
+export type ThinkingLevel = (typeof ThinkingLevel)[keyof typeof ThinkingLevel];

packages/ai/src/types/requests.ts

@@ -27,7 +27,8 @@ import {
   HarmBlockThreshold,
   HarmCategory,
   InferenceMode,
-  ResponseModality
+  ResponseModality,
+  ThinkingLevel
 } from './enums';
 import { ObjectSchemaRequest, SchemaRequest } from './schema';
 
@@ -436,18 +437,44 @@ export interface ThinkingConfig {
   /**
    * The thinking budget, in tokens.
    *
+   * @remarks
    * This parameter sets an upper limit on the number of tokens the model can use for its internal
    * "thinking" process. A higher budget may result in higher quality responses for complex tasks
    * but can also increase latency and cost.
    *
-   * If you don't specify a budget, the model will determine the appropriate amount
-   * of thinking based on the complexity of the prompt.
+   * The range of supported thinking budget values depends on the model.
+   *
+   * <ul>
+   * <li>To use the default thinking budget or thinking level for a model, leave
+   * this value undefined.</li>
+   *
+   * <li>To disable thinking, when supported by the model, set this value
+   * to `0`.</li>
+   *
+   * <li>To use dynamic thinking, allowing the model to decide on the thinking
+   * budget based on the task, set this value to `-1`.</li>
+   * </ul>
    *
    * An error will be thrown if you set a thinking budget for a model that does not support this
    * feature or if the specified budget is not within the model's supported range.
+   *
+   * The model will also error if `thinkingLevel` and `thinkingBudget` are
+   * both set.
    */
   thinkingBudget?: number;
 
+  /**
+   * If not specified, Gemini will use the model's default dynamic thinking level.
+   *
+   * @remarks
+   * Note: The model will error if `thinkingLevel` and `thinkingBudget` are
+   * both set.
+   *
+   * Important: Gemini 2.5 series models do not support thinking levels; use
+   * `thinkingBudget` to set a thinking budget instead.
+   */
+  thinkingLevel?: ThinkingLevel;
+
   /**
    * Whether to include "thought summaries" in the model's response.
    *