feat(anthropic): add Claude Opus 5

AGENTS.md

@@ -42,6 +42,7 @@ Future built-in tool candidates (`apply_patch`, `request_user_input`, `webfetch`
 Native Z.ai GLM-5.2 provider behavior is specified in `dev-docs/specs/zai-provider.md` and implemented through core `ChatZai` plus runtime `model.provider=zai`.
 Native Moonshot Kimi K3 provider behavior is specified in `dev-docs/specs/moonshot-provider.md` and implemented through core `ChatMoonshot` plus runtime `model.provider=moonshot`.
 Native xAI Grok 4.5 provider behavior is specified in `dev-docs/specs/xai-provider.md` and implemented through core `ChatXai` plus runtime `model.provider=xai`.
+Anthropic Claude Opus 5 uses the existing native `ChatAnthropic` path with model ID `claude-opus-5`, adaptive thinking across `low|medium|high|xhigh|max`, and Claude API fast mode; its static model contract lives in `packages/core/src/models/anthropic.ts`.
 
 ## Implementation plan
 

packages/core/src/models/anthropic.ts

@@ -15,6 +15,14 @@ export const ANTHROPIC_MODELS: ModelSpec[] = [
 		maxInputTokens: 1_000_000,
 		maxOutputTokens: 128_000,
 	},
+	{
+		id: "claude-opus-5",
+		provider: "anthropic",
+		contextWindow: 1_000_000,
+		maxInputTokens: 1_000_000,
+		maxOutputTokens: 128_000,
+		supportsFast: true,
+	},
 	{
 		id: "claude-opus-4-8",
 		provider: "anthropic",

packages/core/tests/model-registry.test.ts

@@ -55,6 +55,20 @@ describe("resolveProviderModelId", () => {
 		});
 	});
 
+	test("registers Claude Opus 5 with published limits and fast mode", () => {
+		const registry = createModelRegistry(ANTHROPIC_MODELS);
+
+		expect(resolveModel(registry, "claude-opus-5", "anthropic")).toEqual({
+			id: "claude-opus-5",
+			provider: "anthropic",
+			contextWindow: 1_000_000,
+			maxInputTokens: 1_000_000,
+			maxOutputTokens: 128_000,
+			supportsFast: true,
+		});
+		expect(supportsFastMode(registry, "claude-opus-5", "anthropic")).toBe(true);
+	});
+
 	test("uses GPT-5.6 as the OpenAI default without a registry alias", () => {
 		const registry = createModelRegistry(OPENAI_MODELS);
 

packages/runtime/src/model-reasoning.ts

@@ -140,6 +140,17 @@ const ANTHROPIC_REASONING_MODEL_TABLE: Readonly<
 		},
 		outputEffortByLevel: ANTHROPIC_OUTPUT_EFFORT_ALL,
 	},
+	"claude-opus-5": {
+		supportedLevels: ["low", "medium", "high", "xhigh", "max"],
+		budgetPresetByLevel: {
+			low: "reasoning_low",
+			medium: "reasoning_medium",
+			high: "reasoning_high",
+			xhigh: "reasoning_xhigh",
+			max: "reasoning_xhigh",
+		},
+		outputEffortByLevel: ANTHROPIC_OUTPUT_EFFORT_ALL,
+	},
 	"claude-opus-4-8": {
 		supportedLevels: ["low", "medium", "high", "xhigh", "max"],
 		budgetPresetByLevel: {
@@ -238,6 +249,7 @@ const ANTHROPIC_REASONING_MODEL_TABLE: Readonly<
 
 const ANTHROPIC_ADAPTIVE_THINKING_MODELS = new Set<string>([
 	"claude-fable-5",
+	"claude-opus-5",
 	"claude-opus-4-8",
 	"claude-opus-4-7",
 	"claude-opus-4-6",

packages/runtime/tests/model-fast.test.ts

@@ -41,6 +41,13 @@ describe("model fast mode resolution", () => {
 	});
 
 	test("enables Anthropic fast mode for supported models only", () => {
+		expect(
+			resolveFastMode({
+				provider: "anthropic",
+				model: "claude-opus-5",
+				requested: true,
+			}),
+		).toEqual({ enabled: true, provider: "anthropic", fastMode: true });
 		expect(
 			resolveFastMode({
 				provider: "anthropic",

packages/runtime/tests/model-list-static.test.ts

@@ -19,6 +19,22 @@ describe("model.list static providers", () => {
 		});
 	});
 
+	test("lists Claude Opus 5 from static metadata", async () => {
+		const result = await buildProviderModelList({
+			provider: "anthropic",
+			includeDetails: true,
+			log: () => {},
+			providerEntriesOverride: {},
+		});
+
+		expect(result.models).toContain("claude-opus-5");
+		expect(result.details?.["claude-opus-5"]).toEqual({
+			context_window: 1_000_000,
+			max_input_tokens: 1_000_000,
+			max_output_tokens: 128_000,
+		});
+	});
+
 	test("details follow merged runtime registry for static providers", async () => {
 		const providerEntries: Record<string, ModelEntry> = {
 			"gpt-5.6": {

packages/runtime/tests/model-reasoning.test.ts

@@ -248,6 +248,21 @@ describe("model reasoning mapping", () => {
 		expect(mapped.usedFallbackModelProfile).toBe(false);
 	});
 
+	test.each(["low", "medium", "high", "xhigh", "max"] as const)(
+		"maps Claude Opus 5 %s to native adaptive effort",
+		(requested) => {
+			const mapped = resolveAnthropicReasoning({
+				model: "claude-opus-5",
+				requested,
+			});
+			expect(mapped.applied).toBe(requested);
+			expect(mapped.thinking).toEqual({ type: "adaptive" });
+			expect(mapped.outputConfig).toEqual({ effort: requested });
+			expect(mapped.fallbackApplied).toBe(false);
+			expect(mapped.usedFallbackModelProfile).toBe(false);
+		},
+	);
+
 	test("uses conservative fallback profile for unknown anthropic model", () => {
 		const missing: string[] = [];
 		const mapped = resolveAnthropicReasoning({