fix(ai): enable xhigh for anthropic opus 4.6

packages/ai/test/supports-xhigh.test.ts

@@ -0,0 +1,22 @@
+import { describe, expect, it } from "vitest";
+import { getModel, supportsXhigh } from "../src/models.js";
+
+describe("supportsXhigh", () => {
+	it("returns true for Anthropic Opus 4.6 on anthropic-messages API", () => {
+		const model = getModel("anthropic", "claude-opus-4-6");
+		expect(model).toBeDefined();
+		expect(supportsXhigh(model!)).toBe(true);
+	});
+
+	it("returns false for non-Opus Anthropic models", () => {
+		const model = getModel("anthropic", "claude-sonnet-4-5");
+		expect(model).toBeDefined();
+		expect(supportsXhigh(model!)).toBe(false);
+	});
+
+	it("returns false for OpenRouter Opus 4.6 (openai-completions API)", () => {
+		const model = getModel("openrouter", "anthropic/claude-opus-4.6");
+		expect(model).toBeDefined();
+		expect(supportsXhigh(model!)).toBe(false);
+	});
+});