Merge pull request #4358 from yanirz/fix/fireworks-session-affinity-cache

fix(ai): add session affinity and compat fixes for Fireworks provider caching

packages/ai/scripts/generate-models.ts

@@ -764,6 +764,16 @@ async function loadModelsDevData(): Promise<Model<any>[]> {
 					},
 					contextWindow: m.limit?.context || 4096,
 					maxTokens: m.limit?.output || 4096,
+					// Fireworks prompt caching uses automatic prefix matching + session affinity.
+					// x-session-affinity routes requests to the same replica for cache hits.
+					// cache_control on tools and eager_input_streaming are not supported.
+					// See: https://docs.fireworks.ai/tools-sdks/anthropic-compatibility
+					compat: {
+						sendSessionAffinityHeaders: true,
+						supportsEagerToolInputStreaming: false,
+						supportsCacheControlOnTools: false,
+						supportsLongCacheRetention: false,
+					},
 				});
 			}
 		}

packages/ai/src/models.generated.ts

@@ -3614,6 +3614,12 @@ export const MODELS = {
 			},
 			contextWindow: 163840,
 			maxTokens: 163840,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/deepseek-v3p2": {
 			id: "accounts/fireworks/models/deepseek-v3p2",
@@ -3631,6 +3637,12 @@ export const MODELS = {
 			},
 			contextWindow: 160000,
 			maxTokens: 160000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/deepseek-v4-pro": {
 			id: "accounts/fireworks/models/deepseek-v4-pro",
@@ -3648,6 +3660,12 @@ export const MODELS = {
 			},
 			contextWindow: 1000000,
 			maxTokens: 384000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/glm-4p5": {
 			id: "accounts/fireworks/models/glm-4p5",
@@ -3665,6 +3683,12 @@ export const MODELS = {
 			},
 			contextWindow: 131072,
 			maxTokens: 131072,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/glm-4p5-air": {
 			id: "accounts/fireworks/models/glm-4p5-air",
@@ -3682,6 +3706,12 @@ export const MODELS = {
 			},
 			contextWindow: 131072,
 			maxTokens: 131072,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/glm-4p7": {
 			id: "accounts/fireworks/models/glm-4p7",
@@ -3699,6 +3729,12 @@ export const MODELS = {
 			},
 			contextWindow: 198000,
 			maxTokens: 198000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/glm-5": {
 			id: "accounts/fireworks/models/glm-5",
@@ -3716,6 +3752,12 @@ export const MODELS = {
 			},
 			contextWindow: 202752,
 			maxTokens: 131072,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/glm-5p1": {
 			id: "accounts/fireworks/models/glm-5p1",
@@ -3733,6 +3775,12 @@ export const MODELS = {
 			},
 			contextWindow: 202800,
 			maxTokens: 131072,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/gpt-oss-120b": {
 			id: "accounts/fireworks/models/gpt-oss-120b",
@@ -3750,6 +3798,12 @@ export const MODELS = {
 			},
 			contextWindow: 131072,
 			maxTokens: 32768,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/gpt-oss-20b": {
 			id: "accounts/fireworks/models/gpt-oss-20b",
@@ -3767,6 +3821,12 @@ export const MODELS = {
 			},
 			contextWindow: 131072,
 			maxTokens: 32768,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/kimi-k2-instruct": {
 			id: "accounts/fireworks/models/kimi-k2-instruct",
@@ -3784,6 +3844,12 @@ export const MODELS = {
 			},
 			contextWindow: 128000,
 			maxTokens: 16384,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/kimi-k2-thinking": {
 			id: "accounts/fireworks/models/kimi-k2-thinking",
@@ -3801,6 +3867,12 @@ export const MODELS = {
 			},
 			contextWindow: 256000,
 			maxTokens: 256000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/kimi-k2p5": {
 			id: "accounts/fireworks/models/kimi-k2p5",
@@ -3818,6 +3890,12 @@ export const MODELS = {
 			},
 			contextWindow: 256000,
 			maxTokens: 256000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/kimi-k2p6": {
 			id: "accounts/fireworks/models/kimi-k2p6",
@@ -3835,6 +3913,12 @@ export const MODELS = {
 			},
 			contextWindow: 262000,
 			maxTokens: 262000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/minimax-m2p1": {
 			id: "accounts/fireworks/models/minimax-m2p1",
@@ -3852,6 +3936,12 @@ export const MODELS = {
 			},
 			contextWindow: 200000,
 			maxTokens: 200000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/minimax-m2p5": {
 			id: "accounts/fireworks/models/minimax-m2p5",
@@ -3869,6 +3959,12 @@ export const MODELS = {
 			},
 			contextWindow: 196608,
 			maxTokens: 196608,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/minimax-m2p7": {
 			id: "accounts/fireworks/models/minimax-m2p7",
@@ -3886,6 +3982,12 @@ export const MODELS = {
 			},
 			contextWindow: 196608,
 			maxTokens: 196608,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/models/qwen3p6-plus": {
 			id: "accounts/fireworks/models/qwen3p6-plus",
@@ -3903,6 +4005,12 @@ export const MODELS = {
 			},
 			contextWindow: 128000,
 			maxTokens: 8192,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 		"accounts/fireworks/routers/kimi-k2p5-turbo": {
 			id: "accounts/fireworks/routers/kimi-k2p5-turbo",
@@ -3920,6 +4028,12 @@ export const MODELS = {
 			},
 			contextWindow: 256000,
 			maxTokens: 256000,
+			compat: {
+				sendSessionAffinityHeaders: true,
+				supportsEagerToolInputStreaming: false,
+				supportsCacheControlOnTools: false,
+				supportsLongCacheRetention: false,
+			},
 		} satisfies Model<"anthropic-messages">,
 	},
 	"github-copilot": {

packages/ai/src/providers/anthropic.ts

@@ -165,9 +165,16 @@ const FINE_GRAINED_TOOL_STREAMING_BETA = "fine-grained-tool-streaming-2025-05-14
 const INTERLEAVED_THINKING_BETA = "interleaved-thinking-2025-05-14";
 
 function getAnthropicCompat(model: Model<"anthropic-messages">): Required<AnthropicMessagesCompat> {
+	// Auto-detect session affinity and cache control support from provider
+	const isFireworks = model.provider === "fireworks";
+	const isCloudflareAiGatewayAnthropic =
+		model.provider === "cloudflare-ai-gateway" && model.baseUrl.includes("anthropic");
 	return {
-		supportsEagerToolInputStreaming: model.compat?.supportsEagerToolInputStreaming ?? true,
+		supportsEagerToolInputStreaming: model.compat?.supportsEagerToolInputStreaming ?? !isFireworks,
-		supportsLongCacheRetention: model.compat?.supportsLongCacheRetention ?? true,
+		supportsLongCacheRetention: model.compat?.supportsLongCacheRetention ?? !isFireworks,
+		sendSessionAffinityHeaders:
+			model.compat?.sendSessionAffinityHeaders ?? !!(isFireworks || isCloudflareAiGatewayAnthropic),
+		supportsCacheControlOnTools: model.compat?.supportsCacheControlOnTools ?? !isFireworks,
 	};
 }
 
@@ -463,6 +470,9 @@ export const streamAnthropic: StreamFunction<"anthropic-messages", AnthropicOpti
 					});
 				}
 
+				const cacheRetention = options?.cacheRetention ?? resolveCacheRetention();
+				const cacheSessionId = cacheRetention === "none" ? undefined : options?.sessionId;
+
 				const created = createClient(
 					model,
 					apiKey,
@@ -470,6 +480,7 @@ export const streamAnthropic: StreamFunction<"anthropic-messages", AnthropicOpti
 					shouldUseFineGrainedToolStreamingBeta(model, context),
 					options?.headers,
 					copilotDynamicHeaders,
+					cacheSessionId,
 				);
 				client = created.client;
 				isOAuth = created.isOAuthToken;
@@ -766,6 +777,7 @@ function createClient(
 	useFineGrainedToolStreamingBeta: boolean,
 	optionsHeaders?: Record<string, string>,
 	dynamicHeaders?: Record<string, string>,
+	sessionId?: string,
 ): { client: Anthropic; isOAuthToken: boolean } {
 	// Adaptive thinking models (Opus 4.6, Sonnet 4.6) have interleaved thinking built-in.
 	// The beta header is deprecated on Opus 4.6 and redundant on Sonnet 4.6, so skip it.
@@ -847,6 +859,8 @@ function createClient(
 	}
 
 	// API key auth
+	const sessionAffinityHeaders: Record<string, string | null> =
+		sessionId && getAnthropicCompat(model).sendSessionAffinityHeaders ? { "x-session-affinity": sessionId } : {};
 	const client = new Anthropic({
 		apiKey,
 		baseURL: model.baseUrl,
@@ -857,6 +871,7 @@ function createClient(
 				"anthropic-dangerous-direct-browser-access": "true",
 				...(betaFeatures.length > 0 ? { "anthropic-beta": betaFeatures.join(",") } : {}),
 			},
+			sessionAffinityHeaders,
 			model.headers,
 			optionsHeaders,
 		),
@@ -912,11 +927,12 @@ function buildParams(
 	}
 
 	if (context.tools && context.tools.length > 0) {
+		const compat = getAnthropicCompat(model);
 		params.tools = convertTools(
 			context.tools,
 			isOAuthToken,
-			getAnthropicCompat(model).supportsEagerToolInputStreaming,
+			compat.supportsEagerToolInputStreaming,
-			cacheControl,
+			compat.supportsCacheControlOnTools ? cacheControl : undefined,
 		);
 	}
 

packages/ai/src/types.ts

@@ -419,6 +419,22 @@ export interface AnthropicMessagesCompat {
 	supportsEagerToolInputStreaming?: boolean;
 	/** Whether the provider supports Anthropic long cache retention (`cache_control.ttl: "1h"`). Default: true. */
 	supportsLongCacheRetention?: boolean;
+	/**
+	 * Whether to send the `x-session-affinity` header from `options.sessionId`
+	 * when caching is enabled. Required for providers like Fireworks that use
+	 * session affinity for prompt cache routing (requests to the same replica
+	 * maximize cache hits).
+	 * Default: false.
+	 */
+	sendSessionAffinityHeaders?: boolean;
+	/**
+	 * Whether the provider supports Anthropic-style `cache_control` markers on
+	 * tool definitions. When false, `cache_control` is omitted from tool params.
+	 * Some Anthropic-compatible providers (e.g., Fireworks) do not support this
+	 * field on tools and may reject or ignore it.
+	 * Default: true.
+	 */
+	supportsCacheControlOnTools?: boolean;
 }
 
 /**

packages/ai/test/fireworks-models.test.ts

@@ -1,6 +1,11 @@
+import { createServer, type IncomingMessage, type ServerResponse } from "node:http";
+import type { AddressInfo } from "node:net";
+import { Type } from "typebox";
 import { afterEach, describe, expect, it } from "vitest";
 import { findEnvKeys, getEnvApiKey } from "../src/env-api-keys.js";
 import { getModel } from "../src/models.js";
+import { streamAnthropic } from "../src/providers/anthropic.js";
+import type { Context, Model, Tool } from "../src/types.js";
 
 const originalFireworksApiKey = process.env.FIREWORKS_API_KEY;
 
@@ -47,4 +52,197 @@ describe("Fireworks models", () => {
 		expect(findEnvKeys("fireworks")).toEqual(["FIREWORKS_API_KEY"]);
 		expect(getEnvApiKey("fireworks")).toBe("test-fireworks-key");
 	});
+
+	it("sets Fireworks-specific compat for session affinity and unsupported tool fields", () => {
+		const model = getModel("fireworks", "accounts/fireworks/models/kimi-k2p6");
+
+		expect(model.compat).toBeDefined();
+		expect(model.compat?.sendSessionAffinityHeaders).toBe(true);
+		expect(model.compat?.supportsEagerToolInputStreaming).toBe(false);
+		expect(model.compat?.supportsCacheControlOnTools).toBe(false);
+		expect(model.compat?.supportsLongCacheRetention).toBe(false);
+	});
+});
+
+// --- Integration tests for Fireworks Anthropic session affinity and tool compat ---
+
+interface CapturedRequest {
+	headers: IncomingMessage["headers"];
+	body: Record<string, unknown>;
+}
+
+const tool: Tool = {
+	name: "lookup",
+	description: "Look up a value",
+	parameters: Type.Object({ value: Type.String() }),
+};
+
+function createFireworksModel(compat?: Model<"anthropic-messages">["compat"]): Model<"anthropic-messages"> {
+	return {
+		id: "accounts/fireworks/models/kimi-k2p6",
+		name: "Kimi K2.6",
+		api: "anthropic-messages",
+		provider: "fireworks",
+		baseUrl: "http://127.0.0.1:0", // overridden by captureAnthropicRequest
+		reasoning: true,
+		input: ["text", "image"],
+		cost: { input: 0.95, output: 4, cacheRead: 0.16, cacheWrite: 0 },
+		contextWindow: 262000,
+		maxTokens: 262000,
+		compat,
+	};
+}
+
+function createAnthropicModel(): Model<"anthropic-messages"> {
+	return {
+		id: "claude-opus-4-7",
+		name: "Claude Opus 4.7",
+		api: "anthropic-messages",
+		provider: "anthropic",
+		baseUrl: "http://127.0.0.1:0", // overridden by captureAnthropicRequest
+		reasoning: true,
+		input: ["text"],
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+		contextWindow: 200000,
+		maxTokens: 32000,
+	};
+}
+
+function createContext(tools: Tool[] = [tool]): Context {
+	return {
+		messages: [{ role: "user", content: "Use the tool", timestamp: Date.now() }],
+		...(tools.length > 0 ? { tools } : {}),
+	};
+}
+
+async function readRequestBody(request: IncomingMessage): Promise<Record<string, unknown>> {
+	const chunks: Buffer[] = [];
+	for await (const chunk of request) {
+		chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk));
+	}
+	return JSON.parse(Buffer.concat(chunks).toString("utf8")) as Record<string, unknown>;
+}
+
+function writeEmptySseResponse(response: ServerResponse): void {
+	response.writeHead(200, { "content-type": "text/event-stream" });
+	response.end();
+}
+
+async function captureAnthropicRequest(
+	model: Model<"anthropic-messages">,
+	context: Context,
+	options?: { sessionId?: string; cacheRetention?: string },
+): Promise<CapturedRequest> {
+	let capturedRequest: CapturedRequest | undefined;
+
+	const server = createServer(async (request, response) => {
+		capturedRequest = {
+			headers: request.headers,
+			body: await readRequestBody(request),
+		};
+		writeEmptySseResponse(response);
+	});
+
+	await new Promise<void>((resolve) => server.listen(0, "127.0.0.1", resolve));
+	const address = server.address() as AddressInfo;
+
+	try {
+		// Override the model's baseUrl to point to the local test server
+		const localModel = { ...model, baseUrl: `http://127.0.0.1:${address.port}` };
+
+		const stream = streamAnthropic(localModel, context, {
+			apiKey: "test-key",
+			cacheRetention: (options?.cacheRetention as "none" | "short" | "long") ?? "short",
+			sessionId: options?.sessionId,
+		});
+
+		for await (const event of stream) {
+			if (event.type === "done" || event.type === "error") break;
+		}
+	} finally {
+		await new Promise<void>((resolve, reject) => {
+			server.close((error) => (error ? reject(error) : resolve()));
+		});
+	}
+
+	if (!capturedRequest) {
+		throw new Error("Anthropic request was not captured");
+	}
+	return capturedRequest;
+}
+
+function getTools(body: Record<string, unknown>): Record<string, unknown>[] {
+	const tools = body.tools;
+	if (!Array.isArray(tools)) {
+		throw new Error("Expected tools in request body");
+	}
+	return tools as Record<string, unknown>[];
+}
+
+describe("Fireworks Anthropic session affinity and tool compat", () => {
+	it("sends x-session-affinity header for Fireworks models", async () => {
+		const model = createFireworksModel();
+		// Need a real port, capture will assign one
+		const request = await captureAnthropicRequest(model, createContext(), {
+			sessionId: "fireworks-session-1",
+		});
+
+		expect(request.headers["x-session-affinity"]).toBe("fireworks-session-1");
+	});
+
+	it("omits x-session-affinity header for native Anthropic models", async () => {
+		const model = createAnthropicModel();
+		const request = await captureAnthropicRequest(model, createContext(), {
+			sessionId: "anthropic-session-1",
+		});
+
+		expect(request.headers["x-session-affinity"]).toBeUndefined();
+	});
+
+	it("omits x-session-affinity header when cacheRetention is none", async () => {
+		const model = createFireworksModel();
+		const request = await captureAnthropicRequest(model, createContext(), {
+			sessionId: "fireworks-session-2",
+			cacheRetention: "none",
+		});
+
+		expect(request.headers["x-session-affinity"]).toBeUndefined();
+	});
+
+	it("omits cache_control on tools for Fireworks models", async () => {
+		const model = createFireworksModel();
+		const request = await captureAnthropicRequest(model, createContext());
+
+		const tools = getTools(request.body);
+		const lastTool = tools[tools.length - 1];
+		expect(lastTool.cache_control).toBeUndefined();
+	});
+
+	it("omits eager_input_streaming on tools for Fireworks models", async () => {
+		const model = createFireworksModel();
+		const request = await captureAnthropicRequest(model, createContext());
+
+		const tools = getTools(request.body);
+		for (const t of tools) {
+			expect(t.eager_input_streaming).toBeUndefined();
+		}
+	});
+
+	it("sends cache_control on tools for native Anthropic models", async () => {
+		const model = createAnthropicModel();
+		const request = await captureAnthropicRequest(model, createContext());
+
+		const tools = getTools(request.body);
+		const lastTool = tools[tools.length - 1];
+		expect(lastTool.cache_control).toBeDefined();
+		expect((lastTool.cache_control as { type: string }).type).toBe("ephemeral");
+	});
+
+	it("sends eager_input_streaming on tools for native Anthropic models", async () => {
+		const model = createAnthropicModel();
+		const request = await captureAnthropicRequest(model, createContext());
+
+		const tools = getTools(request.body);
+		expect(tools[0].eager_input_streaming).toBe(true);
+	});
 });