ryanRfox · ryanRfox · May 16, 2026
diff --git a/examples/typescript/facilitator/basic/README.md b/examples/typescript/facilitator/basic/README.md
@@ -23,6 +23,18 @@ and fill required environment variables:
 - `SVM_PRIVATE_KEY` - Solana facilitator private key
 - `PORT` - Server port (optional, defaults to 4022)
 
+Optional environment variables:
+
+- `EVM_NETWORK` _(recommended for testnet exploration)_ - CAIP-2 EVM network the
+  facilitator settles on. Default is `eip155:84532` (Base Sepolia). Chains shipped
+  in viem's chain database (and present in
+  [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts))
+  just work — e.g. `eip155:8453` for Base Mainnet. For chains viem doesn't ship a
+  default RPC for (or to use a custom RPC), set `EVM_RPC_URL`. The Solana accept
+  stays on Solana Devnet by default.
+- `EVM_RPC_URL` - Custom RPC URL override. Required for chains where viem ships no
+  default RPC (e.g. Mezo Testnet `eip155:31611`).
+
 **⚠️ Security Note:** The facilitator key is the signer used to settle payments on-chain. Keep it separate from your seller `payTo` wallet and buyer test wallets, and make sure it is funded only for facilitator gas/fees.
 
 2. Install and build all packages from the typescript examples root:

diff --git a/examples/typescript/facilitator/basic/index.ts b/examples/typescript/facilitator/basic/index.ts
@@ -14,15 +14,60 @@ import { toFacilitatorSvmSigner } from "@x402/svm";
 import { ExactSvmScheme } from "@x402/svm/exact/facilitator";
 import dotenv from "dotenv";
 import express from "express";
-import { createWalletClient, http, publicActions } from "viem";
+import {
+  type Chain,
+  createWalletClient,
+  defineChain,
+  http,
+  publicActions,
+} from "viem";
+import * as allChains from "viem/chains";
 import { privateKeyToAccount } from "viem/accounts";
-import { baseSepolia } from "viem/chains";
 
 dotenv.config();
 
 // Configuration
 const PORT = process.env.PORT || "4022";
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain. EVM_RPC_URL overrides viem's chain
+// default RPC (required for chains viem doesn't ship with a public RPC).
+const EVM_NETWORK = (process.env.EVM_NETWORK ??
+  "eip155:84532") as `${string}:${string}`;
+
+/**
+ * Map a CAIP-2 EVM identifier to a viem `Chain`. Falls back to a minimal
+ * `defineChain` so chains viem hasn't packaged still work for callers
+ * supplying their own EVM_RPC_URL.
+ *
+ * @param caip2 - CAIP-2 EVM identifier (e.g. "eip155:84532")
+ * @returns viem Chain object suitable for createWalletClient/createPublicClient
+ */
+function resolveViemChain(caip2: string): Chain {
+  const [namespace, ref] = caip2.split(":");
+  if (namespace !== "eip155") {
+    throw new Error(`resolveViemChain: not an EVM network: ${caip2}`);
+  }
+  const chainId = Number(ref);
+  if (!Number.isInteger(chainId) || chainId <= 0) {
+    throw new Error(`resolveViemChain: invalid EVM chain id in ${caip2}`);
+  }
+  const known = (Object.values(allChains) as Chain[]).find(
+    (c) => c.id === chainId,
+  );
+  if (known) return known;
+  return defineChain({
+    id: chainId,
+    name: `EVM ${chainId}`,
+    nativeCurrency: { name: "Ether", symbol: "ETH", decimals: 18 },
+    rpcUrls: { default: { http: [] } },
+  });
+}
+
+const evmChain = resolveViemChain(EVM_NETWORK);
+const evmRpcUrl =
+  process.env.EVM_RPC_URL?.trim() || evmChain.rpcUrls.default?.http?.[0] || "";
+
 // Validate required environment variables
 if (!process.env.EVM_PRIVATE_KEY) {
   console.error("❌ EVM_PRIVATE_KEY environment variable is required");
@@ -39,6 +84,7 @@ const evmAccount = privateKeyToAccount(
   process.env.EVM_PRIVATE_KEY as `0x${string}`,
 );
 console.info(`EVM Facilitator account: ${evmAccount.address}`);
+console.info(`EVM Network: ${EVM_NETWORK} (${evmChain.name})`);
 
 // Initialize the SVM account from private key
 const svmAccount = await createKeyPairSignerFromBytes(
@@ -49,8 +95,8 @@ console.info(`SVM Facilitator account: ${svmAccount.address}`);
 // Create a Viem client with both wallet and public capabilities
 const viemClient = createWalletClient({
   account: evmAccount,
-  chain: baseSepolia,
-  transport: http(),
+  chain: evmChain,
+  transport: http(evmRpcUrl || undefined),
 }).extend(publicActions);
 
 // Initialize the x402 Facilitator with EVM and SVM support
@@ -118,10 +164,10 @@ const facilitator = new x402Facilitator()
 
 // Register EVM and SVM schemes
 facilitator.register(
-  "eip155:84532",
+  EVM_NETWORK,
   new ExactEvmScheme(evmSigner, { deployERC4337WithEIP6492: true }),
-); // Base Sepolia
-facilitator.register("eip155:84532", new UptoEvmScheme(evmSigner));
+);
+facilitator.register(EVM_NETWORK, new UptoEvmScheme(evmSigner));
 facilitator.register(
   "solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1",
   new ExactSvmScheme(svmSigner),

diff --git a/examples/typescript/servers/advanced/README.md b/examples/typescript/servers/advanced/README.md
@@ -64,6 +64,10 @@ and fill required environment variables:
 
 > **Hedera Testnet:** Get testnet HBAR from the [Hedera Faucet](https://portal.hedera.com/faucet).
 
+Optional environment variables (apply to the `dynamic-price`, `dynamic-pay-to`, `hooks`, and `custom-money-definition` demos):
+
+- `EVM_NETWORK` _(recommended for testnet exploration)_ - CAIP-2 EVM network the route accepts. Default is `eip155:84532` (Base Sepolia). Set to any chain in [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts) to retarget the demo. The `custom-money-definition` demo also keeps a separate `eip155:100` (Gnosis Chain) literal as part of the registerMoneyParser teaching surface — that literal is intentional and not driven by `EVM_NETWORK`.
+
 2. Install and build all packages from the typescript examples root:
 
 ```bash

diff --git a/examples/typescript/servers/advanced/custom-money-definition.ts b/examples/typescript/servers/advanced/custom-money-definition.ts
@@ -19,6 +19,13 @@ if (!facilitatorUrl) {
 }
 const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
 
+// CAIP-2 EVM network selection for the route. Default is Base Sepolia (eip155:84532);
+// set EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+// NOTE: the eip155:100 (Gnosis Chain) literal below is intentional — it teaches
+// the registerMoneyParser pattern for a custom-chain asset, independent of the
+// route's chain selection.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const app = express();
 
 app.use(
@@ -28,15 +35,15 @@ app.use(
         accepts: {
           scheme: "exact",
           price: "$0.001",
-          network: "eip155:84532",
+          network: EVM_NETWORK,
           payTo: evmAddress,
         },
         description: "Weather data",
         mimeType: "application/json",
       },
     },
     new x402ResourceServer(facilitatorClient).register(
-      "eip155:84532",
+      EVM_NETWORK,
       new ExactEvmScheme().registerMoneyParser(async (amount, network) => {
         // Custom money parser such that on the Gnosis Chain (xDai) network, we use Wrapped XDAI (WXDAI) when describing money
         // NOTE: Wrapped XDAI is not an EIP-3009 complaint token, and would fail the current ExactEvm implementation. This example is for demonstration purposes

diff --git a/examples/typescript/servers/advanced/dynamic-pay-to.ts b/examples/typescript/servers/advanced/dynamic-pay-to.ts
@@ -29,6 +29,10 @@ if (!facilitatorUrl) {
 }
 const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const app = express();
 
 app.use(
@@ -38,7 +42,7 @@ app.use(
         accepts: {
           scheme: "exact",
           price: "$0.001",
-          network: "eip155:84532",
+          network: EVM_NETWORK,
           payTo: context => {
             // Dynamic payTo based on HTTP request context
             const country = context.adapter.getQueryParam?.("country") ?? "US";
@@ -49,7 +53,7 @@ app.use(
         mimeType: "application/json",
       },
     },
-    new x402ResourceServer(facilitatorClient).register("eip155:84532", new ExactEvmScheme()),
+    new x402ResourceServer(facilitatorClient).register(EVM_NETWORK, new ExactEvmScheme()),
   ),
 );
 

diff --git a/examples/typescript/servers/advanced/dynamic-price.ts b/examples/typescript/servers/advanced/dynamic-price.ts
@@ -18,6 +18,10 @@ if (!facilitatorUrl) {
 }
 const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const app = express();
 
 app.use(
@@ -31,14 +35,14 @@ app.use(
             const tier = context.adapter.getQueryParam?.("tier") ?? "standard";
             return tier === "premium" ? "$0.005" : "$0.001";
           },
-          network: "eip155:84532",
+          network: EVM_NETWORK,
           payTo: evmAddress,
         },
         description: "Weather data",
         mimeType: "application/json",
       },
     },
-    new x402ResourceServer(facilitatorClient).register("eip155:84532", new ExactEvmScheme()),
+    new x402ResourceServer(facilitatorClient).register(EVM_NETWORK, new ExactEvmScheme()),
   ),
 );
 

diff --git a/examples/typescript/servers/advanced/hooks.ts b/examples/typescript/servers/advanced/hooks.ts
@@ -18,8 +18,12 @@ if (!facilitatorUrl) {
 }
 const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const resourceServer = new x402ResourceServer(facilitatorClient)
-  .register("eip155:84532", new ExactEvmScheme())
+  .register(EVM_NETWORK, new ExactEvmScheme())
   .onBeforeVerify(async context => {
     console.log("Before verify hook", context);
     // Abort verification by returning { abort: true, reason: string }
@@ -54,7 +58,7 @@ app.use(
         accepts: {
           scheme: "exact",
           price: "$0.001",
-          network: "eip155:84532",
+          network: EVM_NETWORK,
           payTo: evmAddress,
         },
         description: "Weather data",

diff --git a/examples/typescript/servers/custom/README.md b/examples/typescript/servers/custom/README.md
@@ -46,6 +46,10 @@ and fill required environment variables:
 - `FACILITATOR_URL` - Facilitator endpoint URL
 - `EVM_ADDRESS` - Ethereum address to receive payments
 
+Optional environment variables:
+
+- `EVM_NETWORK` _(recommended for testnet exploration)_ - CAIP-2 EVM network the route accepts. Default is `eip155:84532` (Base Sepolia). Set to any chain in [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts) to retarget the demo.
+
 2. Install and build all packages from the typescript examples root:
 
 ```bash

diff --git a/examples/typescript/servers/custom/index.ts b/examples/typescript/servers/custom/index.ts
@@ -39,15 +39,20 @@ if (!facilitatorUrl) {
   process.exit(1);
 }
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 console.log("\n🔧 Custom x402 Server Implementation");
 console.log("This example demonstrates manual payment handling without middleware.\n");
 console.log(`✅ Payment address: ${evmAddress}`);
-console.log(`✅ Facilitator: ${facilitatorUrl}\n`);
+console.log(`✅ Facilitator: ${facilitatorUrl}`);
+console.log(`✅ Network: ${EVM_NETWORK}\n`);
 
 // Create facilitator client and resource server
 const facilitatorClient = new HTTPFacilitatorClient({ url: facilitatorUrl });
 const resourceServer = new x402ResourceServer(facilitatorClient).register(
-  "eip155:84532",
+  EVM_NETWORK,
   new ExactEvmScheme(),
 );
 
@@ -61,7 +66,7 @@ const routeConfigs: Record<string, RoutePaymentConfig> = {
   "GET /weather": {
     scheme: "exact",
     price: "$0.001",
-    network: "eip155:84532",
+    network: EVM_NETWORK,
     payTo: evmAddress,
     description: "Weather data",
     mimeType: "application/json",

diff --git a/examples/typescript/servers/express/README.md b/examples/typescript/servers/express/README.md
@@ -48,6 +48,14 @@ and fill required environment variables:
 - `EVM_ADDRESS` - Ethereum address to receive payments
 - `SVM_ADDRESS` - Solana address to receive payments
 
+Optional environment variables:
+
+- `EVM_NETWORK` *(recommended for testnet exploration)* - CAIP-2 EVM network the route accepts.
+  Default is `eip155:84532` (Base Sepolia). Set to any chain in
+  [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts)
+  to retarget the demo — e.g. `eip155:8453` for Base Mainnet, `eip155:31611` for
+  Mezo Testnet. The SVM accept stays on Solana Devnet by default.
+
 2. Install and build all packages from the typescript examples root:
 ```bash
 cd ../../

diff --git a/examples/typescript/servers/express/index.ts b/examples/typescript/servers/express/index.ts
@@ -13,6 +13,10 @@ if (!evmAddress || !svmAddress) {
   process.exit(1);
 }
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const facilitatorUrl = process.env.FACILITATOR_URL;
 if (!facilitatorUrl) {
   console.error("❌ FACILITATOR_URL environment variable is required");
@@ -30,7 +34,7 @@ app.use(
           {
             scheme: "exact",
             price: "$0.001",
-            network: "eip155:84532",
+            network: EVM_NETWORK,
             payTo: evmAddress,
           },
           {
@@ -45,7 +49,7 @@ app.use(
       },
     },
     new x402ResourceServer(facilitatorClient)
-      .register("eip155:84532", new ExactEvmScheme())
+      .register(EVM_NETWORK, new ExactEvmScheme())
       .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme()),
   ),
 );

diff --git a/examples/typescript/servers/fastify/README.md b/examples/typescript/servers/fastify/README.md
@@ -47,6 +47,14 @@ and fill required environment variables:
 - `EVM_ADDRESS` - Ethereum address to receive payments
 - `SVM_ADDRESS` - Solana address to receive payments
 
+Optional environment variables:
+
+- `EVM_NETWORK` *(recommended for testnet exploration)* - CAIP-2 EVM network the route accepts.
+  Default is `eip155:84532` (Base Sepolia). Set to any chain in
+  [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts)
+  to retarget the demo — e.g. `eip155:8453` for Base Mainnet, `eip155:31611` for
+  Mezo Testnet. The SVM accept stays on Solana Devnet by default.
+
 2. Install and build all packages from the typescript examples root:
 
 ```bash

diff --git a/examples/typescript/servers/fastify/index.ts b/examples/typescript/servers/fastify/index.ts
@@ -13,6 +13,10 @@ if (!evmAddress || !svmAddress) {
   process.exit(1);
 }
 
+// CAIP-2 EVM network selection. Default is Base Sepolia (eip155:84532); set
+// EVM_NETWORK to point at any EVM chain in @x402/evm's DEFAULT_STABLECOINS.
+const EVM_NETWORK = (process.env.EVM_NETWORK ?? "eip155:84532") as `${string}:${string}`;
+
 const facilitatorUrl = process.env.FACILITATOR_URL;
 if (!facilitatorUrl) {
   console.error("❌ FACILITATOR_URL environment variable is required");
@@ -30,7 +34,7 @@ paymentMiddleware(
         {
           scheme: "exact",
           price: "$0.001",
-          network: "eip155:84532",
+          network: EVM_NETWORK,
           payTo: evmAddress,
         },
         {
@@ -45,7 +49,7 @@ paymentMiddleware(
     },
   },
   new x402ResourceServer(facilitatorClient)
-    .register("eip155:84532", new ExactEvmScheme())
+    .register(EVM_NETWORK, new ExactEvmScheme())
     .register("solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1", new ExactSvmScheme()),
 );
 

diff --git a/examples/typescript/servers/hono/README.md b/examples/typescript/servers/hono/README.md
@@ -48,6 +48,14 @@ and fill required environment variables:
 - `EVM_ADDRESS` - Ethereum address to receive payments
 - `SVM_ADDRESS` - Solana address to receive payments
 
+Optional environment variables:
+
+- `EVM_NETWORK` *(recommended for testnet exploration)* - CAIP-2 EVM network the route accepts.
+  Default is `eip155:84532` (Base Sepolia). Set to any chain in
+  [`DEFAULT_STABLECOINS`](../../../../typescript/packages/mechanisms/evm/src/shared/defaultAssets.ts)
+  to retarget the demo — e.g. `eip155:8453` for Base Mainnet, `eip155:31611` for
+  Mezo Testnet. The SVM accept stays on Solana Devnet by default.
+
 2. Install and build all packages from the typescript examples root:
 
 ```bash