Add Claude Fable 5.1 support

packages/types/src/providers/anthropic.ts

@@ -164,6 +164,23 @@ export const anthropicModels = {
 		supportsTemperature: false,
 		description: "Claude Opus 5 is Anthropic's most capable model for complex agentic coding and enterprise work.",
 	},
+	"claude-fable-5-1": {
+		maxTokens: 128_000, // Overridden to 8k if `enableReasoningEffort` is false.
+		contextWindow: 1_000_000,
+		supportsImages: true,
+		supportsPromptCache: true,
+		inputPrice: 10.0, // $10 per million input tokens
+		outputPrice: 50.0, // $50 per million output tokens
+		cacheWritesPrice: 12.5, // $12.50 per million tokens (5-minute cache)
+		cacheReadsPrice: 0.25, // $0.25 per million tokens (2.5% of base input price)
+		// Fable 5.1 only accepts adaptive thinking (or an omitted thinking field).
+		// Manual budget_tokens and non-default sampling parameters return a 400.
+		supportsReasoningBudget: true,
+		supportsReasoningBinary: true,
+		supportsTemperature: false,
+		description:
+			"Claude Fable 5.1 extends Fable 5 with stronger long-running agentic coding, multistep research, and document work.",
+	},
 	"claude-fable-5": {
 		maxTokens: 128_000, // Overridden to 8k if `enableReasoningEffort` is false.
 		contextWindow: 1_000_000,

packages/types/src/providers/bedrock.ts

@@ -252,6 +252,24 @@ export const bedrockModels = {
 		cachableFields: ["system", "messages", "tools"],
 		description: "Claude Opus 5 is Anthropic's most capable model for complex agentic coding and enterprise work.",
 	},
+	"anthropic.claude-fable-5-1": {
+		maxTokens: 128_000,
+		contextWindow: 1_000_000,
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningBudget: true,
+		supportsReasoningBinary: true,
+		supportsTemperature: false,
+		inputPrice: 10.0,
+		outputPrice: 50.0,
+		cacheWritesPrice: 12.5,
+		cacheReadsPrice: 0.25,
+		minTokensPerCachePoint: 512,
+		maxCachePoints: 4,
+		cachableFields: ["system", "messages", "tools"],
+		description:
+			"Claude Fable 5.1 extends Fable 5 with stronger long-running agentic coding, multistep research, and document work.",
+	},
 	"anthropic.claude-fable-5": {
 		maxTokens: 8192,
 		contextWindow: 1_000_000,
@@ -643,7 +661,7 @@ export const BEDROCK_1M_CONTEXT_MODEL_IDS = [
 // - Claude Opus 4.6
 // - Claude Opus 4.7
 // - Claude Opus 5
-// - Claude Fable 5 (cross-region inference only — can only be used through an inference profile)
+// - Claude Fable 5 and 5.1 (cross-region inference only — can only be used through an inference profile)
 export const BEDROCK_GLOBAL_INFERENCE_MODEL_IDS = [
 	"anthropic.claude-sonnet-4-20250514-v1:0",
 	"anthropic.claude-sonnet-4-5-20250929-v1:0",
@@ -655,6 +673,7 @@ export const BEDROCK_GLOBAL_INFERENCE_MODEL_IDS = [
 	"anthropic.claude-opus-4-7",
 	"anthropic.claude-opus-4-8",
 	"anthropic.claude-opus-5",
+	"anthropic.claude-fable-5-1",
 	"anthropic.claude-fable-5",
 ] as const
 

packages/types/src/providers/openrouter.ts

@@ -45,6 +45,7 @@ export const OPEN_ROUTER_PROMPT_CACHING_MODELS = new Set([
 	"anthropic/claude-opus-4.5",
 	"anthropic/claude-opus-4.6",
 	"anthropic/claude-opus-5",
+	"anthropic/claude-fable-5.1",
 	"anthropic/claude-fable-5",
 	"anthropic/claude-haiku-4.5",
 	"google/gemini-2.5-flash-preview",
@@ -78,6 +79,7 @@ export const OPEN_ROUTER_REASONING_BUDGET_MODELS = new Set([
 	"anthropic/claude-opus-4.5",
 	"anthropic/claude-opus-4.6",
 	"anthropic/claude-opus-5",
+	"anthropic/claude-fable-5.1",
 	"anthropic/claude-fable-5",
 	"anthropic/claude-sonnet-4",
 	"anthropic/claude-sonnet-4.5",

packages/types/src/providers/vercel-ai-gateway.ts

@@ -14,6 +14,7 @@ export const VERCEL_AI_GATEWAY_PROMPT_CACHING_MODELS = new Set([
 	"anthropic/claude-opus-4.5",
 	"anthropic/claude-opus-4.6",
 	"anthropic/claude-opus-5",
+	"anthropic/claude-fable-5.1",
 	"anthropic/claude-fable-5",
 	"anthropic/claude-sonnet-4",
 	"anthropic/claude-sonnet-4.6",
@@ -60,6 +61,7 @@ export const VERCEL_AI_GATEWAY_VISION_AND_TOOLS_MODELS = new Set([
 	"anthropic/claude-opus-4.5",
 	"anthropic/claude-opus-4.6",
 	"anthropic/claude-opus-5",
+	"anthropic/claude-fable-5.1",
 	"anthropic/claude-fable-5",
 	"anthropic/claude-sonnet-4",
 	"anthropic/claude-sonnet-4.5",

packages/types/src/providers/vertex.ts

@@ -489,6 +489,21 @@ export const vertexModels = {
 		supportsTemperature: false,
 		description: "Claude Opus 5 is Anthropic's most capable model for complex agentic coding and enterprise work.",
 	},
+	"claude-fable-5-1": {
+		maxTokens: 128_000,
+		contextWindow: 1_000_000,
+		supportsImages: true,
+		supportsPromptCache: true,
+		inputPrice: 10.0,
+		outputPrice: 50.0,
+		cacheWritesPrice: 12.5,
+		cacheReadsPrice: 0.25,
+		supportsReasoningBudget: true,
+		supportsReasoningBinary: true,
+		supportsTemperature: false,
+		description:
+			"Claude Fable 5.1 extends Fable 5 with stronger long-running agentic coding, multistep research, and document work.",
+	},
 	"claude-fable-5": {
 		maxTokens: 8192,
 		contextWindow: 1_000_000,

src/api/providers/__tests__/anthropic-vertex.spec.ts

@@ -992,6 +992,24 @@ describe("VertexHandler", () => {
 			expect(model.info.supportsTemperature).toBe(false)
 		})
 
+		it("should return Claude Fable 5.1 model info", () => {
+			const handler = new AnthropicVertexHandler({
+				apiModelId: "claude-fable-5-1",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+			})
+
+			const model = handler.getModel()
+			expect(model.id).toBe("claude-fable-5-1")
+			expect(model.info.maxTokens).toBe(128_000)
+			expect(model.info.contextWindow).toBe(1_000_000)
+			expect(model.info.cacheReadsPrice).toBe(0.25)
+			expect(model.info.supportsReasoningBinary).toBe(true)
+			expect(model.info.supportsReasoningBudget).toBe(true)
+			expect(model.info.supportsPromptCache).toBe(true)
+			expect(model.info.supportsTemperature).toBe(false)
+		})
+
 		it("should return Claude Sonnet 5 model info", () => {
 			const handler = new AnthropicVertexHandler({
 				apiModelId: "claude-sonnet-5",
@@ -1266,6 +1284,37 @@ describe("VertexHandler", () => {
 				enableReasoningEffort: true,
 			})
 
+			const mockCreate = vitest
+				.fn()
+				.mockImplementation(async () =>
+					asyncStreamFrom([
+						{ type: "message_start", message: { usage: { input_tokens: 10, output_tokens: 5 } } },
+					]),
+				)
+			fableHandler["client"].messages.create = mockCreate
+
+			await fableHandler.createMessage("You are a helpful assistant", [{ role: "user", content: "Hello" }]).next()
+
+			expect(mockCreate).toHaveBeenCalledWith(
+				expect.objectContaining({
+					thinking: { type: "adaptive" },
+				}),
+				undefined,
+			)
+
+			const request = mockCreate.mock.calls[0][0]
+			expect(request.thinking).not.toHaveProperty("budget_tokens")
+			expect(request.temperature).toBeUndefined()
+		})
+
+		it("should use adaptive thinking for Claude Fable 5.1", async () => {
+			const fableHandler = new AnthropicVertexHandler({
+				apiModelId: "claude-fable-5-1",
+				vertexProjectId: "test-project",
+				vertexRegion: "us-central1",
+				enableReasoningEffort: true,
+			})
+
 			const mockCreate = vitest
 				.fn()
 				.mockImplementation(async () =>