feat(nodejs-langgraph-agent): LangGraph ReAct agent with Dynamic server-side MPC wallet

examples/nodejs-langgraph-agent/.example.env

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+# ─── Anthropic (the LLM driving the agent) ──────────────────────────────────
+ANTHROPIC_API_KEY=sk-ant-your-key-here
+
+# ─── Dynamic environment (server-side MPC signing) ──────────────────────────
+DYNAMIC_ENVIRONMENT_ID=your_environment_id
+DYNAMIC_API_KEY=your_dynamic_api_key

examples/nodejs-langgraph-agent/.gitignore

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+node_modules/
+dist/
+.env
+.env.*
+!.example.env
+*.log
+.DS_Store
+.wallet-state.json

examples/nodejs-langgraph-agent/README.md

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+# Bare-bones LangGraph agent + Dynamic server wallet
+
+A minimal [LangGraph](https://github.com/langchain-ai/langgraphjs) ReAct agent
+that acts through its own **Dynamic server-side MPC wallet**. The agent creates
+and owns its wallet entirely server-side — no user JWT, no delegation, no
+client-side approval flow required.
+
+It ships three tools:
+
+| Tool | What it does |
+| --- | --- |
+| `list_wallets` | Returns the agent's server wallet address. |
+| `get_token_balances` | Native-token balances across EVM chains via on-chain RPC. |
+| `send_transaction` | Native transfer, signed via Dynamic server-side MPC. **Always** gated behind a `y/N` confirm prompt. |
+
+## How it works
+
+```
+You ──▶ LangGraph ReAct agent (Claude) ──▶ tools ──▶ Dynamic MPC signing ──▶ chain
+```
+
+- **`src/wallet.ts`** — initializes the `DynamicEvmWalletClient`, creates a new
+  wallet on first run (persisted to `.wallet-state.json`), and signs + broadcasts
+  transactions.
+- **`src/tools.ts`** — the three LangChain tools above.
+- **`src/agent.ts`** — the `createReactAgent` loop (Claude Haiku 4.5) + system prompt.
+- **`src/index.ts`** — an interactive terminal REPL.
+- **`src/confirm.ts`** — the confirmation prompt for sensitive actions.
+
+## Setup
+
+1. Install dependencies (this repo uses pnpm):
+
+   ```bash
+   pnpm install
+   ```
+
+2. Create your env file from the example and fill it in:
+
+   ```bash
+   cp .example.env .env
+   ```
+
+   | Variable | Purpose |
+   | --- | --- |
+   | `ANTHROPIC_API_KEY` | Drives the agent. |
+   | `DYNAMIC_ENVIRONMENT_ID`, `DYNAMIC_API_KEY` | Dynamic env for server-side MPC signing. |
+
+3. Run it:
+
+   ```bash
+   pnpm start        # or: pnpm dev  (watch mode)
+   ```
+
+   On first run the agent creates an MPC wallet and saves it to `.wallet-state.json`.
+   Subsequent runs reuse the same wallet.
+
+   ```
+   You: show my wallet
+   Agent: Your server wallet is 0x1234…abcd.
+
+   You: send 0.001 ETH on ethereum to 0xabc…
+   ┌─ ACTION REQUIRED ────────────────────────────────────────
+   │  Send native transfer
+   │    Chain:  Ethereum (1)
+   │    To:     0xabc…
+   │    Amount: 0.001 ETH
+   └──────────────────────────────────────────────────────────
+   Proceed? [y/N]
+   ```
+
+## Notes
+
+- **Mainnet only.** Supported chains: Ethereum (1), Polygon (137), Base (8453),
+  Arbitrum (42161), Optimism (10), BSC (56). Extend `CHAIN_MAP` in `src/wallet.ts`.
+- `.wallet-state.json` contains the server key share — treat it like a private key.
+  It is gitignored; never commit it or expose it to untrusted parties.
+- `send_transaction` only does native transfers. To add ERC-20 transfers or contract
+  calls, build the calldata and extend `sendTransactionServer`.
+- Conversation memory is in-process (`MemorySaver`) and resets on restart.

examples/nodejs-langgraph-agent/package.json

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+{
+  "name": "nodejs-langgraph-agent",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Bare-bones LangGraph ReAct agent backed by a Dynamic server-side MPC wallet",
+  "type": "module",
+  "scripts": {
+    "start": "tsx src/index.ts",
+    "dev": "tsx watch src/index.ts",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@dynamic-labs-wallet/node": "1.0.25",
+    "@dynamic-labs-wallet/node-evm": "1.0.25",
+    "@langchain/anthropic": "1.4.0",
+    "@langchain/core": "1.1.47",
+    "@langchain/langgraph": "1.3.2",
+    "dotenv": "17.4.2",
+    "langchain": "1.4.1",
+    "viem": "2.50.4",
+    "zod": "4.4.3"
+  },
+  "devDependencies": {
+    "@types/node": "25.9.1",
+    "tsx": "4.22.3",
+    "typescript": "6.0.3"
+  }
+}

examples/nodejs-langgraph-agent/src/agent.ts

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+import { ChatAnthropic } from "@langchain/anthropic";
+import { createAgent } from "langchain";
+import { HumanMessage } from "@langchain/core/messages";
+import { MemorySaver } from "@langchain/langgraph";
+import { allTools } from "./tools.js";
+
+const SYSTEM_PROMPT =
+  "You are a Web3 assistant with access to an agent-owned EVM wallet via Dynamic server-side MPC.\n\n" +
+  "## The agent wallet\n" +
+  "There is one wallet: the agent's own server wallet, created and held server-side by this agent. " +
+  "Use list_wallets to get the address. When the user says 'my wallet' or 'the wallet', this is it. " +
+  "The same address works on every EVM chain.\n\n" +
+  "## Capabilities\n" +
+  "- get_token_balances: check native token balances across EVM chains (on-chain RPC). " +
+  "Pass networkId to filter to a specific chain.\n" +
+  "- send_transaction: send a native transfer. The user is always prompted to confirm " +
+  "before anything is broadcast.\n\n" +
+  "## Rules\n" +
+  "- Mainnet only — no testnets.\n" +
+  "- Always resolve the wallet address with list_wallets before acting on 'my wallet'.\n" +
+  "- Never invent balances or transaction hashes — only report tool results.";
+
+// Built lazily on first use so startup credential checks run (and report) first.
+let _agent: ReturnType<typeof createAgent> | null = null;
+
+function getAgent() {
+  if (!_agent) {
+    _agent = createAgent({
+      model: new ChatAnthropic({ model: "claude-haiku-4-5-20251001", temperature: 0 }),
+      tools: allTools,
+      checkpointer: new MemorySaver(),
+      systemPrompt: SYSTEM_PROMPT,
+    });
+  }
+  return _agent;
+}
+
+export async function runAgent(
+  userMessage: string,
+  threadId: string = "default"
+): Promise<string> {
+  const result = await getAgent().invoke(
+    { messages: [new HumanMessage(userMessage)] },
+    { configurable: { thread_id: threadId } }
+  );
+  const last = result.messages[result.messages.length - 1];
+  return typeof last.content === "string" ? last.content : JSON.stringify(last.content);
+}

examples/nodejs-langgraph-agent/src/confirm.ts

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+import type readline from "node:readline";
+
+// ─── Shared readline instance ─────────────────────────────────────────────────
+
+let _rl: readline.Interface | null = null;
+
+export function setReadlineForConfirm(rl: readline.Interface): void {
+  _rl = rl;
+}
+
+// ─── Confirmation prompt ──────────────────────────────────────────────────────
+
+const WIDTH = 58;
+
+/** Prompts the user to confirm a sensitive action. Defaults to deny. */
+export async function confirm(summary: string): Promise<boolean> {
+  const bar = "─".repeat(WIDTH);
+
+  process.stdout.write(`\n┌─ ACTION REQUIRED ${bar.slice(18)}\n`);
+  for (const line of summary.split("\n")) {
+    process.stdout.write(`│  ${line}\n`);
+  }
+  process.stdout.write(`└${bar}\n`);
+
+  return new Promise((resolve) => {
+    if (!_rl) {
+      process.stdout.write("No readline available — action denied.\n");
+      resolve(false);
+      return;
+    }
+    _rl.question("Proceed? [y/N] ", (answer) => {
+      const confirmed = answer.trim().toLowerCase() === "y";
+      if (!confirmed) process.stdout.write("Cancelled.\n");
+      resolve(confirmed);
+    });
+  });
+}

examples/nodejs-langgraph-agent/src/index.ts

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+import "dotenv/config";
+import readline from "node:readline";
+import { initServerWallet } from "./wallet.js";
+import { setAgentWallet } from "./tools.js";
+import { runAgent } from "./agent.js";
+import { setReadlineForConfirm } from "./confirm.js";
+
+// ─── Initialize the agent's server wallet ────────────────────────────────────
+
+const wallet = await initServerWallet();
+setAgentWallet(wallet);
+
+// ─── Interactive REPL ─────────────────────────────────────────────────────────
+
+console.log("=".repeat(60));
+console.log("  Dynamic + LangGraph bare-bones agent");
+console.log("=".repeat(60));
+console.log("Example commands:");
+console.log('  "show my wallet"');
+console.log('  "what are my token balances"');
+console.log('  "send 0.001 ETH on ethereum to 0x..."');
+console.log("  Type 'exit' to quit\n");
+
+const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
+setReadlineForConfirm(rl);
+
+const threadId = "interactive-session";
+
+function prompt(question: string): Promise<string> {
+  return new Promise((resolve) => rl.question(question, resolve));
+}
+
+rl.on("close", () => {
+  console.log("\nGoodbye!");
+  process.exit(0);
+});
+
+while (true) {
+  const input = (await prompt("You: ")).trim();
+  if (!input) continue;
+  if (input.toLowerCase() === "exit" || input.toLowerCase() === "quit") {
+    rl.close();
+    break;
+  }
+  try {
+    const response = await runAgent(input, threadId);
+    console.log(`\nAgent: ${response}\n`);
+  } catch (err: any) {
+    console.error(`\nError: ${err?.message ?? String(err)}\n`);
+  }
+}