fix(ai): handle explicit thinking off across providers closes #2490

packages/ai/CHANGELOG.md

@@ -11,6 +11,7 @@
 
 - Fixed OpenAI Responses replay for foreign tool-call item IDs by hashing foreign `function_call.id` values into bounded `fc_<hash>` IDs instead of preserving backend-specific normalized shapes that OpenAI Codex rejects.
 - Fixed Anthropic thinking disable handling to send `thinking: { type: "disabled" }` for reasoning-capable models when thinking is explicitly off, and added payload and env-gated end-to-end coverage for the Anthropic provider ([#2022](https://github.com/badlogic/pi-mono/issues/2022))
+- Fixed explicit thinking disable handling across Google, Google Vertex, Gemini CLI, OpenAI Responses, Azure OpenAI Responses, and OpenRouter-backed OpenAI-compatible completions. Gemini 3 models now fall back to the lowest supported thinking level when full disable is not supported, and OpenAI/OpenRouter reasoning models now send explicit `none` effort instead of relying on provider defaults ([#2490](https://github.com/badlogic/pi-mono/issues/2490))
 
 ## [0.61.1] - 2026-03-20
 

packages/ai/src/providers/azure-openai-responses.ts

@@ -240,18 +240,7 @@ function buildParams(
 			};
 			params.include = ["reasoning.encrypted_content"];
 		} else {
-			if (model.name.toLowerCase().startsWith("gpt-5")) {
-				// Jesus Christ, see https://community.openai.com/t/need-reasoning-false-option-for-gpt-5/1351588/7
-				messages.push({
-					role: "developer",
-					content: [
-						{
-							type: "input_text",
-							text: "# Juice: 0 !important",
-						},
-					],
-				});
-			}
+			params.reasoning = { effort: "none" };
 		}
 	}
 

packages/ai/src/providers/google-gemini-cli.ts

@@ -889,6 +889,8 @@ export function buildRequest(
 		} else if (options.thinking.budgetTokens !== undefined) {
 			generationConfig.thinkingConfig.thinkingBudget = options.thinking.budgetTokens;
 		}
+	} else if (model.reasoning && options.thinking && !options.thinking.enabled) {
+		generationConfig.thinkingConfig = getDisabledThinkingConfig(model.id);
 	}
 
 	const request: CloudCodeAssistRequest["request"] = {
@@ -946,6 +948,21 @@ export function buildRequest(
 
 type ClampedThinkingLevel = Exclude<ThinkingLevel, "xhigh">;
 
+function getDisabledThinkingConfig(modelId: string): ThinkingConfig {
+	// Google docs: Gemini 3.1 Pro cannot disable thinking, and Gemini 3 Flash / Flash-Lite
+	// do not support full thinking-off either. For Gemini 3 models, use the lowest supported
+	// thinkingLevel without includeThoughts so hidden thinking remains invisible to pi.
+	if (isGemini3ProModel(modelId)) {
+		return { thinkingLevel: "LOW" as any };
+	}
+	if (isGemini3FlashModel(modelId)) {
+		return { thinkingLevel: "MINIMAL" as any };
+	}
+
+	// Gemini 2.x supports disabling via thinkingBudget = 0.
+	return { thinkingBudget: 0 };
+}
+
 function getGeminiCliThinkingLevel(effort: ClampedThinkingLevel, modelId: string): GoogleThinkingLevel {
 	if (isGemini3ProModel(modelId)) {
 		switch (effort) {

packages/ai/src/providers/google-vertex.ts

@@ -436,6 +436,8 @@ function buildParams(
 			thinkingConfig.thinkingBudget = options.thinking.budgetTokens;
 		}
 		config.thinkingConfig = thinkingConfig;
+	} else if (model.reasoning && options.thinking && !options.thinking.enabled) {
+		config.thinkingConfig = getDisabledThinkingConfig(model);
 	}
 
 	if (options.signal) {
@@ -464,6 +466,22 @@ function isGemini3FlashModel(model: Model<"google-generative-ai">): boolean {
 	return /gemini-3(?:\.\d+)?-flash/.test(model.id.toLowerCase());
 }
 
+function getDisabledThinkingConfig(model: Model<"google-vertex">): ThinkingConfig {
+	// Google docs: Gemini 3.1 Pro cannot disable thinking, and Gemini 3 Flash / Flash-Lite
+	// do not support full thinking-off either. For Gemini 3 models, use the lowest supported
+	// thinkingLevel without includeThoughts so hidden thinking remains invisible to pi.
+	const geminiModel = model as unknown as Model<"google-generative-ai">;
+	if (isGemini3ProModel(geminiModel)) {
+		return { thinkingLevel: ThinkingLevel.LOW };
+	}
+	if (isGemini3FlashModel(geminiModel)) {
+		return { thinkingLevel: ThinkingLevel.MINIMAL };
+	}
+
+	// Gemini 2.x supports disabling via thinkingBudget = 0.
+	return { thinkingBudget: 0 };
+}
+
 function getGemini3ThinkingLevel(
 	effort: ClampedThinkingLevel,
 	model: Model<"google-generative-ai">,

packages/ai/src/providers/google.ts

@@ -371,6 +371,8 @@ function buildParams(
 			thinkingConfig.thinkingBudget = options.thinking.budgetTokens;
 		}
 		config.thinkingConfig = thinkingConfig;
+	} else if (model.reasoning && options.thinking && !options.thinking.enabled) {
+		config.thinkingConfig = getDisabledThinkingConfig(model);
 	}
 
 	if (options.signal) {
@@ -399,6 +401,21 @@ function isGemini3FlashModel(model: Model<"google-generative-ai">): boolean {
 	return /gemini-3(?:\.\d+)?-flash/.test(model.id.toLowerCase());
 }
 
+function getDisabledThinkingConfig(model: Model<"google-generative-ai">): ThinkingConfig {
+	// Google docs: Gemini 3.1 Pro cannot disable thinking, and Gemini 3 Flash / Flash-Lite
+	// do not support full thinking-off either. For Gemini 3 models, use the lowest supported
+	// thinkingLevel without includeThoughts so hidden thinking remains invisible to pi.
+	if (isGemini3ProModel(model)) {
+		return { thinkingLevel: "LOW" as any };
+	}
+	if (isGemini3FlashModel(model)) {
+		return { thinkingLevel: "MINIMAL" as any };
+	}
+
+	// Gemini 2.x supports disabling via thinkingBudget = 0.
+	return { thinkingBudget: 0 };
+}
+
 function getGemini3ThinkingLevel(
 	effort: ClampedThinkingLevel,
 	model: Model<"google-generative-ai">,

packages/ai/src/providers/openai-completions.ts

@@ -410,12 +410,16 @@ function buildParams(model: Model<"openai-completions">, context: Context, optio
 		(params as any).enable_thinking = !!options?.reasoningEffort;
 	} else if (compat.thinkingFormat === "qwen-chat-template" && model.reasoning) {
 		(params as any).chat_template_kwargs = { enable_thinking: !!options?.reasoningEffort };
-	} else if (compat.thinkingFormat === "openrouter" && options?.reasoningEffort && model.reasoning) {
+	} else if (compat.thinkingFormat === "openrouter" && model.reasoning) {
 		// OpenRouter normalizes reasoning across providers via a nested reasoning object.
 		const openRouterParams = params as typeof params & { reasoning?: { effort?: string } };
-		openRouterParams.reasoning = {
-			effort: mapReasoningEffort(options.reasoningEffort, compat.reasoningEffortMap),
-		};
+		if (options?.reasoningEffort) {
+			openRouterParams.reasoning = {
+				effort: mapReasoningEffort(options.reasoningEffort, compat.reasoningEffortMap),
+			};
+		} else {
+			openRouterParams.reasoning = { effort: "none" };
+		}
 	} else if (options?.reasoningEffort && model.reasoning && compat.supportsReasoningEffort) {
 		// OpenAI-style reasoning_effort
 		(params as any).reasoning_effort = mapReasoningEffort(options.reasoningEffort, compat.reasoningEffortMap);

packages/ai/src/providers/openai-responses.ts

@@ -221,18 +221,7 @@ function buildParams(model: Model<"openai-responses">, context: Context, options
 			};
 			params.include = ["reasoning.encrypted_content"];
 		} else {
-			if (model.name.startsWith("gpt-5")) {
-				// Jesus Christ, see https://community.openai.com/t/need-reasoning-false-option-for-gpt-5/1351588/7
-				messages.push({
-					role: "developer",
-					content: [
-						{
-							type: "input_text",
-							text: "# Juice: 0 !important",
-						},
-					],
-				});
-			}
+			params.reasoning = { effort: "none" };
 		}
 	}
 

packages/ai/test/google-thinking-disable.test.ts

@@ -0,0 +1,183 @@
+import { describe, expect, it } from "vitest";
+import { getModel } from "../src/models.js";
+import { streamSimple } from "../src/stream.js";
+import type { Api, Context, Model, SimpleStreamOptions } from "../src/types.js";
+import { resolveApiKey } from "./oauth.js";
+
+type SimpleOptionsWithExtras = SimpleStreamOptions & Record<string, unknown>;
+
+interface RunResult {
+	thinkingEventCount: number;
+	thinkingCharCount: number;
+	text: string;
+	outputTokens: number;
+	contentTypes: string[];
+}
+
+interface DisableExpectations {
+	requestOptions?: SimpleOptionsWithExtras;
+	minPongs?: number;
+	maxOutputTokens?: number;
+}
+
+const oauthTokens = await Promise.all([resolveApiKey("google-gemini-cli"), resolveApiKey("google-antigravity")]);
+const [geminiCliToken, antigravityToken] = oauthTokens;
+
+function makeContext(): Context {
+	return {
+		systemPrompt: "You are a precise assistant. Follow the requested output format exactly.",
+		messages: [
+			{
+				role: "user",
+				content:
+					"Before replying, carefully solve 36863 * 5279 internally. Then reply with the word pong repeated exactly 40 times, separated by single spaces. Do not add any other text.",
+				timestamp: Date.now(),
+			},
+		],
+	};
+}
+
+function countPongs(text: string): number {
+	return text.match(/\bpong\b/gi)?.length ?? 0;
+}
+
+async function runWithoutReasoning<TApi extends Api>(
+	model: Model<TApi>,
+	options: SimpleOptionsWithExtras = {},
+): Promise<RunResult> {
+	const s = streamSimple(model, makeContext(), {
+		maxTokens: 160,
+		temperature: 0,
+		...options,
+	});
+
+	let thinkingEventCount = 0;
+	let thinkingCharCount = 0;
+
+	for await (const event of s) {
+		if (event.type === "thinking_start" || event.type === "thinking_end") {
+			thinkingEventCount += 1;
+		}
+		if (event.type === "thinking_delta") {
+			thinkingEventCount += 1;
+			thinkingCharCount += event.delta.length;
+		}
+	}
+
+	const response = await s.result();
+	expect(response.stopReason, response.errorMessage).toBe("stop");
+
+	const text = response.content
+		.filter((block) => block.type === "text")
+		.map((block) => block.text)
+		.join("")
+		.trim();
+
+	return {
+		thinkingEventCount,
+		thinkingCharCount,
+		text,
+		outputTokens: response.usage.output,
+		contentTypes: response.content.map((block) => block.type),
+	};
+}
+
+async function expectThinkingDisabledE2E<TApi extends Api>(model: Model<TApi>, expectations: DisableExpectations = {}) {
+	const result = await runWithoutReasoning(model, expectations.requestOptions);
+
+	expect(result.thinkingEventCount).toBe(0);
+	expect(result.thinkingCharCount).toBe(0);
+	expect(result.contentTypes).not.toContain("thinking");
+	expect(countPongs(result.text)).toBeGreaterThanOrEqual(expectations.minPongs ?? 35);
+	if (expectations.maxOutputTokens !== undefined) {
+		expect(result.outputTokens).toBeLessThan(expectations.maxOutputTokens);
+	}
+}
+
+describe.skipIf(!process.env.ANTHROPIC_API_KEY)("Anthropic thinking disable E2E", () => {
+	it("disables thinking for budget-based reasoning models", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("anthropic", "claude-sonnet-4-5"), {
+			requestOptions: { maxTokens: 320, temperature: 0 },
+		});
+	});
+
+	it("disables thinking for adaptive reasoning models", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("anthropic", "claude-sonnet-4-6"), {
+			requestOptions: { maxTokens: 320, temperature: 0 },
+		});
+	});
+});
+
+describe.skipIf(!process.env.GEMINI_API_KEY)("Google thinking disable E2E", () => {
+	it("disables thinking for Gemini 2.5", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google", "gemini-2.5-flash"));
+	});
+
+	it("disables thinking for Gemini 3.x", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google", "gemini-3-flash-preview"));
+	});
+
+	it("does not error when thinking is off for Gemini 3.1 Pro", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google", "gemini-3.1-pro-preview"), {
+			requestOptions: { maxTokens: 512 },
+			minPongs: 20,
+		});
+	});
+});
+
+describe("Google Vertex thinking disable E2E", () => {
+	const vertexProject = process.env.GOOGLE_CLOUD_PROJECT || process.env.GCLOUD_PROJECT;
+	const vertexLocation = process.env.GOOGLE_CLOUD_LOCATION;
+	const vertexApiKey = process.env.GOOGLE_CLOUD_API_KEY;
+	const vertexOptions = vertexApiKey
+		? ({ apiKey: vertexApiKey } satisfies SimpleOptionsWithExtras)
+		: vertexProject && vertexLocation
+			? ({ project: vertexProject, location: vertexLocation } satisfies SimpleOptionsWithExtras)
+			: undefined;
+
+	it.skipIf(!vertexOptions)("disables thinking for Gemini 2.5", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google-vertex", "gemini-2.5-flash"), {
+			requestOptions: vertexOptions,
+		});
+	});
+
+	it.skipIf(!vertexOptions)("disables thinking for Gemini 3.x", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google-vertex", "gemini-3-flash-preview"), {
+			requestOptions: vertexOptions,
+		});
+	});
+});
+
+describe("Google Gemini CLI thinking disable E2E", () => {
+	it.skipIf(!geminiCliToken)("disables thinking for Gemini 2.5", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google-gemini-cli", "gemini-2.5-flash"), {
+			requestOptions: { apiKey: geminiCliToken! },
+			maxOutputTokens: 100,
+		});
+	});
+});
+
+describe("Google Antigravity thinking disable E2E", () => {
+	it.skipIf(!antigravityToken)("disables thinking for Gemini 3.x", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("google-antigravity", "gemini-3-flash"), {
+			requestOptions: { apiKey: antigravityToken! },
+			maxOutputTokens: 100,
+		});
+	});
+});
+
+describe.skipIf(!process.env.OPENAI_API_KEY)("OpenAI thinking disable E2E", () => {
+	it("disables thinking for Responses reasoning models", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("openai", "gpt-5.4-mini"), {
+			requestOptions: { temperature: undefined },
+		});
+	});
+});
+
+describe.skipIf(!process.env.OPENROUTER_API_KEY)("OpenRouter thinking disable E2E", () => {
+	it("disables thinking for Qwen 3.5 reasoning models", { retry: 2, timeout: 30000 }, async () => {
+		await expectThinkingDisabledE2E(getModel("openrouter", "qwen/qwen3.5-plus-02-15"), {
+			maxOutputTokens: 100,
+		});
+	});
+});