Support thinking level configuration for Gemini 3 Pro models (#176)

* support Google thinking level configuration for Gemini 3 Pro models

* relax model ID check for gemini 3 pro

packages/ai/src/providers/google.ts

@@ -6,6 +6,8 @@ import {
 	type GenerateContentParameters,
 	GoogleGenAI,
 	type Part,
+	type ThinkingConfig,
+	type ThinkingLevel,
 } from "@google/genai";
 import { calculateCost } from "../models.js";
 import type {
@@ -31,6 +33,7 @@ export interface GoogleOptions extends StreamOptions {
 	thinking?: {
 		enabled: boolean;
 		budgetTokens?: number; // -1 for dynamic, 0 to disable
+		level?: ThinkingLevel;
 	};
 }
 
@@ -293,10 +296,13 @@ function buildParams(
 	}
 
 	if (options.thinking?.enabled && model.reasoning) {
-		config.thinkingConfig = {
+		const thinkingConfig: ThinkingConfig = { includeThoughts: true };
-			includeThoughts: true,
+		if (options.thinking.level !== undefined) {
-			...(options.thinking.budgetTokens !== undefined && { thinkingBudget: options.thinking.budgetTokens }),
+			thinkingConfig.thinkingLevel = options.thinking.level;
-		};
+		} else if (options.thinking.budgetTokens !== undefined) {
+			thinkingConfig.thinkingBudget = options.thinking.budgetTokens;
+		}
+		config.thinkingConfig = thinkingConfig;
 	}
 
 	if (options.signal) {

packages/ai/src/stream.ts

@@ -1,3 +1,4 @@
+import { ThinkingLevel } from "@google/genai";
 import { type AnthropicOptions, streamAnthropic } from "./providers/anthropic.js";
 import { type GoogleOptions, streamGoogle } from "./providers/google.js";
 import { type OpenAICompletionsOptions, streamOpenAICompletions } from "./providers/openai-completions.js";
@@ -159,15 +160,26 @@ function mapOptionsForApi<TApi extends Api>(
 		case "google-generative-ai": {
 			if (!options?.reasoning) return base as any;
 
-			const googleBudget = getGoogleBudget(
+			const googleModel = model as Model<"google-generative-ai">;
-				model as Model<"google-generative-ai">,
+			const effort = clampReasoning(options.reasoning)!;
-				clampReasoning(options.reasoning)!,
+
-			);
+			// Gemini 3 Pro models use thinkingLevel exclusively instead of thinkingBudget.
+			// https://ai.google.dev/gemini-api/docs/thinking#set-budget
+			if (isGemini3ProModel(googleModel)) {
 				return {
 					...base,
 					thinking: {
 						enabled: true,
-					budgetTokens: googleBudget,
+						level: getGoogleThinkingLevel(effort),
+					},
+				} satisfies GoogleOptions;
+			}
+
+			return {
+				...base,
+				thinking: {
+					enabled: true,
+					budgetTokens: getGoogleBudget(googleModel, effort),
 				},
 			} satisfies GoogleOptions;
 		}
@@ -182,6 +194,23 @@ function mapOptionsForApi<TApi extends Api>(
 
 type ClampedReasoningEffort = Exclude<ReasoningEffort, "xhigh">;
 
+function isGemini3ProModel(model: Model<"google-generative-ai">): boolean {
+	// Covers gemini-3-pro, gemini-3-pro-preview, and possible other prefixed ids in the future
+	return model.id.includes("3-pro");
+}
+
+function getGoogleThinkingLevel(effort: ClampedReasoningEffort): ThinkingLevel {
+	// Gemini 3 Pro only supports LOW/HIGH (for now)
+	switch (effort) {
+		case "minimal":
+		case "low":
+			return ThinkingLevel.LOW;
+		case "medium":
+		case "high":
+			return ThinkingLevel.HIGH;
+	}
+}
+
 function getGoogleBudget(model: Model<"google-generative-ai">, effort: ClampedReasoningEffort): number {
 	// See https://ai.google.dev/gemini-api/docs/thinking#set-budget
 	if (model.id.includes("2.5-pro")) {