fix(ai): enable xhigh for anthropic opus 4.6

packages/ai/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed `supportsXhigh()` to treat Anthropic Messages Opus 4.6 models as xhigh-capable so `streamSimple` can map `xhigh` to adaptive effort `max`
+
 ## [0.52.4] - 2026-02-05
 
 ## [0.52.3] - 2026-02-05

packages/ai/src/models.ts

@@ -47,10 +47,21 @@ export function calculateCost<TApi extends Api>(model: Model<TApi>, usage: Usage
 
 /**
  * Check if a model supports xhigh thinking level.
- * Currently only certain OpenAI Codex models support this.
+ *
+ * Supported today:
+ * - GPT-5.2 / GPT-5.3 model families
+ * - Anthropic Messages API Opus 4.6 models (xhigh maps to adaptive effort "max")
  */
 export function supportsXhigh<TApi extends Api>(model: Model<TApi>): boolean {
-	return model.id.includes("gpt-5.2") || model.id.includes("gpt-5.3");
+	if (model.id.includes("gpt-5.2") || model.id.includes("gpt-5.3")) {
+		return true;
+	}
+
+	if (model.api === "anthropic-messages") {
+		return model.id.includes("opus-4-6") || model.id.includes("opus-4.6");
+	}
+
+	return false;
 }
 
 /**

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);
+	});
+});

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed thinking level capability detection so Anthropic Opus 4.6 models expose `xhigh` in selectors and cycling
+
 ## [0.52.4] - 2026-02-05
 
 ### Fixed