diff --git a/src/index.ts b/src/index.ts
index 54762c0..c6d0c96 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -171,3 +171,6 @@ export {
   type Leg,
   type MemberKey,
 } from './mpc/AereThresholdAccountClient.js';
+
+// public testnet 28001: addresses, faucet, x402 facilitator, test dollar (2026-09-02)
+export * from "./testnet";
diff --git a/src/testnet.ts b/src/testnet.ts
new file mode 100644
index 0000000..76aaa22
--- /dev/null
+++ b/src/testnet.ts
@@ -0,0 +1,46 @@
+/**
+ * AERE public testnet (chain 28001), live since 2026-09-02. Same node software as mainnet 2800 with the
+ * post-quantum consensus message enforcement switched ON, a native-coin faucet, a test dollar with EIP-3009
+ * for x402 "exact" payments, and an x402 v2 facilitator. Nothing here has value; keys and coins are free.
+ *
+ * Every constant below is a public address or URL that a client needs; none is a secret. The test dollar
+ * and facilitator were measured end to end on 2026-09-02 (real payment, on-chain settlement, replay refused);
+ * the same probe runs every six hours and its result is public at `x402ProbeUrl`.
+ */
+export const TESTNET_28001 = {
+  chainId: 28001,
+  caip2: "eip155:28001",
+  name: "AERE Testnet",
+  currency: { name: "Test AERE", symbol: "tAERE", decimals: 18 },
+  rpc: "https://testnet-rpc.aere.network",
+  ws: "wss://testnet-rpc.aere.network/ws",
+  /** POST { address } -> a drip of tAERE after a short browser proof of work (see /testnet.html) */
+  faucetApi: "https://testnet-faucet-api.aere.network",
+  /** public genesis of the testnet, byte-for-byte what the validators run */
+  genesisUrl: "https://aere.network/testnet-genesis.json",
+  /** live load-bench and x402 probe results, JSON */
+  loadBenchUrl: "https://testnet-rpc.aere.network/sarcina/ultima.json",
+  x402ProbeUrl: "https://testnet-rpc.aere.network/sarcina/x402-proba.json",
+  /** x402 v2 facilitator for this chain: GET /supported, POST /verify, POST /settle */
+  x402Facilitator: "https://testnet-rpc.aere.network/x402",
+  /** Aere Test USD: ERC-20 + EIP-3009 (transferWithAuthorization), 6 decimals, `faucet()` mints 100 tUSD per address per hour */
+  tUSD: {
+    address: "0x8215bA247a3574af8EBC36606eB437811E318FBd",
+    decimals: 6,
+    /** EIP-712 domain fields x402 clients put in `extra` */
+    eip712: { name: "AereTestUSD", version: "2" },
+  },
+} as const;
+
+/** A ready-made x402 `paymentRequirements` object for the testnet test dollar. */
+export function testnetPaymentRequirements(payTo: string, amountAtomic: string, maxTimeoutSeconds = 300) {
+  return {
+    scheme: "exact" as const,
+    network: TESTNET_28001.caip2,
+    amount: amountAtomic,
+    asset: TESTNET_28001.tUSD.address,
+    payTo,
+    maxTimeoutSeconds,
+    extra: { ...TESTNET_28001.tUSD.eip712 },
+  };
+}