diff --git a/packages/ai/src/api/bedrock-converse-stream.ts b/packages/ai/src/api/bedrock-converse-stream.ts
index 76aaef65e..aecd2f2ea 100644
--- a/packages/ai/src/api/bedrock-converse-stream.ts
+++ b/packages/ai/src/api/bedrock-converse-stream.ts
@@ -1308,9 +1308,45 @@ function buildAdditionalModelRequestFields(
 		return result;
 	}
 
+	const candidates = getModelMatchCandidates(model.id, model.name);
+
+	if (candidates.some((s) => s.includes("gpt-oss"))) {
+		return { reasoning_effort: OPENAI_GPT_OSS_EFFORT[options.reasoning] };
+	}
+
+	if (candidates.some((s) => s.includes("gpt-"))) {
+		const mapped = model.thinkingLevelMap?.[options.reasoning];
+		return {
+			reasoning: { effort: typeof mapped === "string" ? mapped : OPENAI_GPT_EFFORT[options.reasoning] },
+		};
+	}
+
 	return undefined;
 }
 
+type OpenAIGptEffort = "low" | "medium" | "high" | "xhigh" | "max";
+type OpenAIGptOssEffort = "low" | "medium" | "high";
+
+/** OpenAI GPT models (GPT-5.x, GPT-6) take a nested `reasoning.effort` and reject `minimal`. */
+const OPENAI_GPT_EFFORT: Record<ThinkingLevel, OpenAIGptEffort> = {
+	minimal: "low",
+	low: "low",
+	medium: "medium",
+	high: "high",
+	xhigh: "xhigh",
+	max: "max",
+};
+
+/** gpt-oss takes a flat `reasoning_effort` and only accepts low, medium and high. */
+const OPENAI_GPT_OSS_EFFORT: Record<ThinkingLevel, OpenAIGptOssEffort> = {
+	minimal: "low",
+	low: "low",
+	medium: "medium",
+	high: "high",
+	xhigh: "high",
+	max: "high",
+};
+
 function createImageBlock(mimeType: string, data: string) {
 	let format: ImageFormat;
 	switch (mimeType) {
diff --git a/packages/ai/test/bedrock-thinking-payload.test.ts b/packages/ai/test/bedrock-thinking-payload.test.ts
index 122fafc84..c2711b2d0 100644
--- a/packages/ai/test/bedrock-thinking-payload.test.ts
+++ b/packages/ai/test/bedrock-thinking-payload.test.ts
@@ -14,6 +14,8 @@ interface BedrockThinkingPayload {
 		};
 		output_config?: { effort?: string };
 		anthropic_beta?: string[];
+		reasoning?: { effort?: string };
+		reasoning_effort?: string;
 	};
 }
 
@@ -197,6 +199,66 @@ describe("Bedrock thinking payload", () => {
 	});
 });
 
+describe("Bedrock OpenAI reasoning payload", () => {
+	// Regression for #9331: the configured thinking level never reached OpenAI models on Bedrock.
+	it.each([
+		["minimal", "low"],
+		["low", "low"],
+		["medium", "medium"],
+		["high", "high"],
+		["xhigh", "xhigh"],
+		["max", "max"],
+	] as const)("sends reasoning=%s as reasoning.effort=%s for GPT-6 and GPT-5.6", async (reasoning, effort) => {
+		for (const id of ["global.openai.gpt-6-sol", "us.openai.gpt-6-luna", "global.openai.gpt-5.6-sol"] as const) {
+			const payload = await capturePayload(getModel("amazon-bedrock", id), { reasoning });
+
+			expect(payload.additionalModelRequestFields, id).toEqual({ reasoning: { effort } });
+		}
+	});
+
+	it("sends reasoning.effort when only model.name identifies a GPT model", async () => {
+		const model: Model<"bedrock-converse-stream"> = {
+			...getModel("amazon-bedrock", "global.openai.gpt-6-sol"),
+			id: "arn:aws:bedrock:us-east-1:123456789012:application-inference-profile/my-profile",
+			name: "GPT-6 Sol",
+		};
+
+		const payload = await capturePayload(model, { reasoning: "medium" });
+
+		expect(payload.additionalModelRequestFields).toEqual({ reasoning: { effort: "medium" } });
+	});
+
+	it("sends flat reasoning_effort for gpt-oss, clamped to high", async () => {
+		const model = getModel("amazon-bedrock", "openai.gpt-oss-120b-1:0");
+
+		expect((await capturePayload(model, { reasoning: "minimal" })).additionalModelRequestFields).toEqual({
+			reasoning_effort: "low",
+		});
+		expect((await capturePayload(model, { reasoning: "medium" })).additionalModelRequestFields).toEqual({
+			reasoning_effort: "medium",
+		});
+		expect((await capturePayload(model, { reasoning: "xhigh" })).additionalModelRequestFields).toEqual({
+			reasoning_effort: "high",
+		});
+	});
+
+	it("sends no reasoning fields when reasoning is off", async () => {
+		let captured: BedrockThinkingPayload | undefined;
+		const s = streamBedrock(getModel("amazon-bedrock", "global.openai.gpt-6-sol"), normalizeContext(makeContext()), {
+			onPayload: (payload) => {
+				captured = payload as BedrockThinkingPayload;
+				throw new PayloadCaptured();
+			},
+		});
+		for await (const event of s) {
+			if (event.type === "error") break;
+		}
+
+		expect(captured).toBeDefined();
+		expect(captured?.additionalModelRequestFields).toBeUndefined();
+	});
+});
+
 describe.skipIf(!hasBedrockCredentials())("Bedrock Claude max tokens E2E", () => {
 	it(
 		"uses the model maxTokens cap instead of Bedrock's 4096-token default for adaptive Claude models",