npm create cloudflare@latest claude-edge-ai -- --type worker
cd claude-edge-ai
npm install @anthropic-ai/sdk

name = "claude-edge-ai"
main = "src/index.ts"
compatibility_date = "2024-09-23"
compatibility_flags = ["nodejs_compat"]

kv_namespaces = [
  { binding = "CACHE", id = "YOUR_KV_NAMESPACE_ID" }
]

[[durable_objects.bindings]]
name = "CONVERSATIONS"
class_name = "ConversationSession"

[[migrations]]
tag = "v1"
new_classes = ["ConversationSession"]

[vars]
ANTHROPIC_MODEL = "claude-sonnet-4-6"
MAX_TOKENS = "1024"

wrangler secret put ANTHROPIC_API_KEY

// src/conversation.ts
import { DurableObject } from "cloudflare:workers";

interface Message {
  role: "user" | "assistant";
  content: string;
}

export class ConversationSession extends DurableObject {
  private messages: Message[] = [];
  private readonly MAX_HISTORY = 20;

  async fetch(request: Request): Promise<Response> {
    const { action, content } = await request.json<{
      action: "add" | "get" | "clear";
      content?: string;
      role?: "user" | "assistant";
    }>();

    if (action === "add") {
      const { role = "user" } = await request.json<any>();
      this.messages.push({ role, content: content! });
      // Keep last N messages to stay within context window
      if (this.messages.length > this.MAX_HISTORY) {
        this.messages = this.messages.slice(-this.MAX_HISTORY);
      }
      await this.ctx.storage.put("messages", this.messages);
      return new Response("ok");
    }

    if (action === "get") {
      const stored = await this.ctx.storage.get<Message[]>("messages");
      this.messages = stored ?? [];
      return Response.json(this.messages);
    }

    if (action === "clear") {
      this.messages = [];
      await this.ctx.storage.delete("messages");
      return new Response("cleared");
    }

    return new Response("unknown action", { status: 400 });
  }
}

// src/index.ts
import Anthropic from "@anthropic-ai/sdk";
import { ConversationSession } from "./conversation";

export { ConversationSession };

interface Env {
  ANTHROPIC_API_KEY: string;
  ANTHROPIC_MODEL: string;
  MAX_TOKENS: string;
  CACHE: KVNamespace;
  CONVERSATIONS: DurableObjectNamespace;
}

// Rate limiting via KV — lightweight leaky bucket
async function checkRateLimit(
  env: Env,
  userId: string,
  maxPerMinute = 20
): Promise<boolean> {
  const key = `ratelimit:${userId}:${Math.floor(Date.now() / 60000)}`;
  const current = Number((await env.CACHE.get(key)) ?? "0");
  if (current >= maxPerMinute) return false;
  await env.CACHE.put(key, String(current + 1), { expirationTtl: 120 });
  return true;
}

// KV-based prompt response cache for identical queries
async function getCachedResponse(
  env: Env,
  prompt: string
): Promise<string | null> {
  const hash = await crypto.subtle.digest(
    "SHA-256",
    new TextEncoder().encode(prompt)
  );
  const key = `cache:${btoa(String.fromCharCode(...new Uint8Array(hash))).slice(0, 32)}`;
  return env.CACHE.get(key);
}

async function setCachedResponse(
  env: Env,
  prompt: string,
  response: string
): Promise<void> {
  const hash = await crypto.subtle.digest(
    "SHA-256",
    new TextEncoder().encode(prompt)
  );
  const key = `cache:${btoa(String.fromCharCode(...new Uint8Array(hash))).slice(0, 32)}`;
  // Cache for 1 hour — adjust for your use case
  await env.CACHE.put(key, response, { expirationTtl: 3600 });
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // CORS preflight
    if (request.method === "OPTIONS") {
      return new Response(null, {
        headers: {
          "Access-Control-Allow-Origin": "*",
          "Access-Control-Allow-Methods": "POST, OPTIONS",
          "Access-Control-Allow-Headers": "Content-Type, X-Session-ID",
        },
      });
    }

    if (request.method !== "POST" || new URL(request.url).pathname !== "/chat") {
      return new Response("Not found", { status: 404 });
    }

    const sessionId = request.headers.get("X-Session-ID") ?? "anonymous";
    const userId = request.headers.get("CF-Connecting-IP") ?? sessionId;

    // Rate limit check
    const allowed = await checkRateLimit(env, userId);
    if (!allowed) {
      return new Response(
        JSON.stringify({ error: "Rate limit exceeded. Try again in a minute." }),
        { status: 429, headers: { "Content-Type": "application/json" } }
      );
    }

    let body: { message: string; stream?: boolean };
    try {
      body = await request.json();
    } catch {
      return new Response(JSON.stringify({ error: "Invalid JSON" }), {
        status: 400,
        headers: { "Content-Type": "application/json" },
      });
    }

    const { message, stream = true } = body;
    if (!message?.trim()) {
      return new Response(JSON.stringify({ error: "Message required" }), {
        status: 400,
        headers: { "Content-Type": "application/json" },
      });
    }

    // Get conversation history from Durable Object
    const doId = env.CONVERSATIONS.idFromName(sessionId);
    const doStub = env.CONVERSATIONS.get(doId);
    const historyResp = await doStub.fetch(
      new Request("http://do/history", {
        method: "POST",
        body: JSON.stringify({ action: "get" }),
      })
    );
    const history = await historyResp.json<Array<{ role: string; content: string }>>();

    const client = new Anthropic({ apiKey: env.ANTHROPIC_API_KEY });

    // For non-streaming: check cache first
    if (!stream) {
      const cached = await getCachedResponse(env, message);
      if (cached) {
        return Response.json({ response: cached, cached: true });
      }
    }

    const messages = [
      ...history,
      { role: "user" as const, content: message },
    ];

    if (stream) {
      // Server-Sent Events streaming response
      const { readable, writable } = new TransformStream();
      const writer = writable.getWriter();
      const encoder = new TextEncoder();

      // Kick off streaming in background (Workers support this pattern)
      (async () => {
        let fullResponse = "";
        try {
          const stream = client.messages.stream({
            model: env.ANTHROPIC_MODEL ?? "claude-sonnet-4-6",
            max_tokens: Number(env.MAX_TOKENS ?? 1024),
            system:
              "You are a helpful AI assistant. Be concise and accurate.",
            messages,
          });

          for await (const chunk of stream) {
            if (
              chunk.type === "content_block_delta" &&
              chunk.delta.type === "text_delta"
            ) {
              const text = chunk.delta.text;
              fullResponse += text;
              await writer.write(
                encoder.encode(`data: ${JSON.stringify({ text })}\n\n`)
              );
            }
          }

          await writer.write(
            encoder.encode(`data: ${JSON.stringify({ done: true })}\n\n`)
          );

          // Persist to conversation history
          await doStub.fetch(
            new Request("http://do/add", {
              method: "POST",
              body: JSON.stringify({ action: "add", role: "user", content: message }),
            })
          );
          await doStub.fetch(
            new Request("http://do/add", {
              method: "POST",
              body: JSON.stringify({
                action: "add",
                role: "assistant",
                content: fullResponse,
              }),
            })
          );
        } catch (err) {
          await writer.write(
            encoder.encode(
              `data: ${JSON.stringify({ error: "Stream error" })}\n\n`
            )
          );
        } finally {
          await writer.close();
        }
      })();

      return new Response(readable, {
        headers: {
          "Content-Type": "text/event-stream",
          "Cache-Control": "no-cache",
          "Access-Control-Allow-Origin": "*",
        },
      });
    } else {
      // Non-streaming: await full response, cache it
      const response = await client.messages.create({
        model: env.ANTHROPIC_MODEL ?? "claude-sonnet-4-6",
        max_tokens: Number(env.MAX_TOKENS ?? 1024),
        system: "You are a helpful AI assistant. Be concise and accurate.",
        messages,
      });

      const text =
        response.content[0].type === "text" ? response.content[0].text : "";

      await setCachedResponse(env, message, text);

      // Persist exchange
      await doStub.fetch(
        new Request("http://do/add", {
          method: "POST",
          body: JSON.stringify({ action: "add", role: "user", content: message }),
        })
      );
      await doStub.fetch(
        new Request("http://do/add", {
          method: "POST",
          body: JSON.stringify({ action: "add", role: "assistant", content: text }),
        })
      );

      return Response.json({ response: text, cached: false });
    }
  },
};

// Example: consume the SSE stream from a React component
async function chat(message: string, sessionId: string) {
  const response = await fetch("https://claude-edge-ai.YOUR_SUBDOMAIN.workers.dev/chat", {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Session-ID": sessionId,
    },
    body: JSON.stringify({ message, stream: true }),
  });

  const reader = response.body!.getReader();
  const decoder = new TextDecoder();

  while (true) {
    const { value, done } = await reader.read();
    if (done) break;

    const lines = decoder.decode(value).split("\n");
    for (const line of lines) {
      if (!line.startsWith("data: ")) continue;
      const data = JSON.parse(line.slice(6));
      if (data.text) process.stdout.write(data.text); // or update React state
      if (data.done) break;
    }
  }
}

# Create KV namespace
wrangler kv:namespace create CACHE

# Update wrangler.toml with the returned namespace ID, then:
wrangler deploy

const response = await client.messages.create({
  model: "claude-sonnet-4-6",
  max_tokens: 1024,
  system: [
    {
      type: "text",
      text: "You are a helpful AI assistant for AcmeCorp. Here is our full product catalog and FAQ: [... large static content ...]",
      cache_control: { type: "ephemeral" },
    },
  ],
  messages,
});