Support adaptive thinking for Anthropic-compatible aliases

closes #4790

packages/ai/test/anthropic-adaptive-thinking-models.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+import { getModels, getProviders } from "../src/models.ts";
+import type { Api, Model } from "../src/types.ts";
+
+const EXPECTED_ADAPTIVE_THINKING_MODELS = [
+	"anthropic/claude-opus-4-6",
+	"anthropic/claude-opus-4-7",
+	"anthropic/claude-sonnet-4-6",
+	"cloudflare-ai-gateway/claude-opus-4-6",
+	"cloudflare-ai-gateway/claude-opus-4-7",
+	"cloudflare-ai-gateway/claude-sonnet-4-6",
+	"github-copilot/claude-opus-4.6",
+	"github-copilot/claude-opus-4.7",
+	"github-copilot/claude-sonnet-4.6",
+	"opencode/claude-opus-4-6",
+	"opencode/claude-opus-4-7",
+	"opencode/claude-sonnet-4-6",
+	"vercel-ai-gateway/anthropic/claude-opus-4.6",
+	"vercel-ai-gateway/anthropic/claude-opus-4.7",
+	"vercel-ai-gateway/anthropic/claude-sonnet-4.6",
+];
+
+function getAllModels(): Model<Api>[] {
+	return getProviders().flatMap((provider) => getModels(provider) as Model<Api>[]);
+}
+
+describe("Anthropic adaptive thinking model metadata", () => {
+	it("marks exactly the built-in Anthropic Messages models that use adaptive thinking", () => {
+		const flaggedModels = getAllModels()
+			.filter((model): model is Model<"anthropic-messages"> => model.api === "anthropic-messages")
+			.filter((model) => model.compat?.forceAdaptiveThinking === true)
+			.map((model) => `${model.provider}/${model.id}`)
+			.sort();
+
+		expect(flaggedModels).toEqual([...EXPECTED_ADAPTIVE_THINKING_MODELS].sort());
+	});
+});

packages/ai/test/anthropic-force-adaptive-thinking.test.ts

@@ -0,0 +1,103 @@
+import { describe, expect, it } from "vitest";
+import { getModel } from "../src/models.ts";
+import { streamSimple } from "../src/stream.ts";
+import type { Context, Model, SimpleStreamOptions } from "../src/types.ts";
+
+interface AnthropicThinkingPayload {
+	thinking?: { type: string; budget_tokens?: number; display?: string };
+	output_config?: { effort?: string };
+}
+
+class PayloadCaptured extends Error {
+	constructor() {
+		super("payload captured");
+		this.name = "PayloadCaptured";
+	}
+}
+
+function makeContext(): Context {
+	return {
+		messages: [{ role: "user", content: "Hello", timestamp: Date.now() }],
+	};
+}
+
+function makeCustomModel(compat?: Model<"anthropic-messages">["compat"]): Model<"anthropic-messages"> {
+	return {
+		// Id intentionally does not match any built-in adaptive substring. This
+		// mirrors corporate proxy schemes such as `anthropic--claude-opus-latest`.
+		id: "vendor--claude-opus-latest",
+		name: "Vendor Proxy Opus Latest",
+		api: "anthropic-messages",
+		provider: "vendor-proxy",
+		baseUrl: "http://127.0.0.1:9",
+		reasoning: true,
+		input: ["text"],
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+		contextWindow: 200000,
+		maxTokens: 32000,
+		compat,
+	};
+}
+
+async function capturePayload(
+	model: Model<"anthropic-messages">,
+	options?: SimpleStreamOptions,
+): Promise<AnthropicThinkingPayload> {
+	let capturedPayload: AnthropicThinkingPayload | undefined;
+
+	const payloadCaptureModel: Model<"anthropic-messages"> = {
+		...model,
+		baseUrl: "http://127.0.0.1:9",
+	};
+
+	const s = streamSimple(payloadCaptureModel, makeContext(), {
+		...options,
+		apiKey: "fake-key",
+		onPayload: (payload) => {
+			capturedPayload = payload as AnthropicThinkingPayload;
+			throw new PayloadCaptured();
+		},
+	});
+
+	await s.result();
+
+	if (!capturedPayload) {
+		throw new Error("Expected payload to be captured before request failure");
+	}
+
+	return capturedPayload;
+}
+
+describe("Anthropic forceAdaptiveThinking compat override", () => {
+	it("sends legacy thinking payload for custom model ids by default", async () => {
+		const payload = await capturePayload(makeCustomModel(), { reasoning: "medium" });
+
+		expect(payload.thinking?.type).toBe("enabled");
+		expect(payload.output_config).toBeUndefined();
+	});
+
+	it("sends adaptive thinking payload when compat.forceAdaptiveThinking is true", async () => {
+		const payload = await capturePayload(makeCustomModel({ forceAdaptiveThinking: true }), { reasoning: "medium" });
+
+		expect(payload.thinking).toEqual({ type: "adaptive", display: "summarized" });
+		expect(payload.output_config).toEqual({ effort: "medium" });
+	});
+
+	it("allows built-in adaptive models to opt out with compat.forceAdaptiveThinking false", async () => {
+		const model: Model<"anthropic-messages"> = {
+			...getModel("anthropic", "claude-opus-4-7"),
+			compat: { forceAdaptiveThinking: false },
+		};
+		const payload = await capturePayload(model, { reasoning: "medium" });
+
+		expect(payload.thinking?.type).toBe("enabled");
+		expect(payload.output_config).toBeUndefined();
+	});
+
+	it("preserves thinking.type=disabled when reasoning is off regardless of override", async () => {
+		const payload = await capturePayload(makeCustomModel({ forceAdaptiveThinking: true }));
+
+		expect(payload.thinking).toEqual({ type: "disabled" });
+		expect(payload.output_config).toBeUndefined();
+	});
+});