diff --git a/packages/ai/test/bedrock-interleaved-thinking.test.ts b/packages/ai/test/bedrock-interleaved-thinking.test.ts
new file mode 100644
index 00000000..dedb94a8
--- /dev/null
+++ b/packages/ai/test/bedrock-interleaved-thinking.test.ts
@@ -0,0 +1,138 @@
+import { Type } from "@sinclair/typebox";
+import { describe, expect, it } from "vitest";
+import { getModel } from "../src/models.js";
+import { complete } from "../src/stream.js";
+import type { Context, StopReason, Tool, ToolCall, ToolResultMessage } from "../src/types.js";
+import { StringEnum } from "../src/utils/typebox-helpers.js";
+import { hasBedrockCredentials } from "./bedrock-utils.js";
+
+const calculatorSchema = Type.Object({
+	a: Type.Number({ description: "First number" }),
+	b: Type.Number({ description: "Second number" }),
+	operation: StringEnum(["add", "subtract", "multiply", "divide"], {
+		description: "The operation to perform.",
+	}),
+});
+
+const calculatorTool: Tool<typeof calculatorSchema> = {
+	name: "calculator",
+	description: "Perform basic arithmetic operations",
+	parameters: calculatorSchema,
+};
+
+type CalculatorOperation = "add" | "subtract" | "multiply" | "divide";
+
+type CalculatorArguments = {
+	a: number;
+	b: number;
+	operation: CalculatorOperation;
+};
+
+function asCalculatorArguments(args: ToolCall["arguments"]): CalculatorArguments {
+	if (typeof args !== "object" || args === null) {
+		throw new Error("Tool arguments must be an object");
+	}
+
+	const value = args as Record<string, unknown>;
+	const operation = value.operation;
+	if (
+		typeof value.a !== "number" ||
+		typeof value.b !== "number" ||
+		(operation !== "add" && operation !== "subtract" && operation !== "multiply" && operation !== "divide")
+	) {
+		throw new Error("Invalid calculator arguments");
+	}
+
+	return { a: value.a, b: value.b, operation };
+}
+
+function evaluateCalculatorCall(toolCall: ToolCall): number {
+	const { a, b, operation } = asCalculatorArguments(toolCall.arguments);
+	switch (operation) {
+		case "add":
+			return a + b;
+		case "subtract":
+			return a - b;
+		case "multiply":
+			return a * b;
+		case "divide":
+			return a / b;
+	}
+}
+
+type BedrockInterleavedModelId =
+	| "global.anthropic.claude-opus-4-5-20251101-v1:0"
+	| "global.anthropic.claude-opus-4-6-v1";
+
+async function assertSecondToolCallWithInterleavedThinking(
+	modelId: BedrockInterleavedModelId,
+	reasoning: "high" | "xhigh",
+) {
+	const llm = getModel("amazon-bedrock", modelId);
+	const context: Context = {
+		systemPrompt: [
+			"You are a helpful assistant that must use tools for arithmetic.",
+			"Always think before every tool call, not just the first one.",
+			"Do not answer with plain text when a tool call is required.",
+		].join(" "),
+		messages: [
+			{
+				role: "user",
+				content: [
+					"Use calculator to calculate 328 * 29.",
+					"You must call the calculator tool exactly once.",
+					"Provide the final answer based on the best guess given the tool result, even if it seems unreliable.",
+				].join(" "),
+				timestamp: Date.now(),
+			},
+		],
+		tools: [calculatorTool],
+	};
+
+	const firstResponse = await complete(llm, context, {
+		reasoning,
+		interleavedThinking: true,
+	});
+
+	expect(firstResponse.stopReason, `Error: ${firstResponse.errorMessage}`).toBe("toolUse" satisfies StopReason);
+	expect(firstResponse.content.some((block) => block.type === "thinking")).toBe(true);
+	expect(firstResponse.content.some((block) => block.type === "toolCall")).toBe(true);
+
+	const firstToolCall = firstResponse.content.find((block) => block.type === "toolCall");
+	expect(firstToolCall?.type).toBe("toolCall");
+	if (!firstToolCall || firstToolCall.type !== "toolCall") {
+		throw new Error("Expected first response to include a tool call");
+	}
+
+	context.messages.push(firstResponse);
+
+	const correctAnswer = evaluateCalculatorCall(firstToolCall);
+	const firstToolResult: ToolResultMessage = {
+		role: "toolResult",
+		toolCallId: firstToolCall.id,
+		toolName: firstToolCall.name,
+		content: [{ type: "text", text: `The answer is ${correctAnswer} or ${correctAnswer * 2}.` }],
+		isError: false,
+		timestamp: Date.now(),
+	};
+	context.messages.push(firstToolResult);
+
+	const secondResponse = await complete(llm, context, {
+		reasoning,
+		interleavedThinking: true,
+	});
+
+	expect(secondResponse.stopReason, `Error: ${secondResponse.errorMessage}`).toBe("stop" satisfies StopReason);
+	expect(secondResponse.content.some((block) => block.type === "thinking")).toBe(true);
+	expect(secondResponse.content.some((block) => block.type === "text")).toBe(true);
+}
+
+describe.skipIf(!hasBedrockCredentials())("Amazon Bedrock interleaved thinking", () => {
+	it("should do interleaved thinking on Claude Opus 4.5", { retry: 3 }, async () => {
+		await assertSecondToolCallWithInterleavedThinking("global.anthropic.claude-opus-4-5-20251101-v1:0", "high");
+	});
+
+	it("should do interleaved thinking on Claude Opus 4.6", { retry: 3 }, async () => {
+		await assertSecondToolCallWithInterleavedThinking("global.anthropic.claude-opus-4-6-v1", "xhigh");
+	});
+});