[#384] Add RPC fallback rotation

lib/rpc.ts

@@ -1,30 +1,157 @@
-import { createPublicClient, http, fallback, type Hex } from "viem";
+import { createPublicClient, http, fallback, type Hex, type PublicClient } from "viem";
 import { base, baseSepolia } from "viem/chains";
 
 const chainId = Number(process.env.NEXT_PUBLIC_CHAIN_ID || "84532");
 const chain = chainId === 8453 ? base : baseSepolia;
+const IS_MAINNET = chainId === 8453;
 
-const customRpc = process.env.NEXT_PUBLIC_RPC_URL;
+const CUSTOM_RPC_URL = process.env.NEXT_PUBLIC_RPC_URL;
 
-const transport = customRpc
-  ? fallback([http(customRpc), http()])
-  : http();
+// ---------------------------------------------------------------------------
+// RPC endpoint lists (Base mainnet only — Sepolia uses chain default)
+// ---------------------------------------------------------------------------
+
+/** Server-side RPC endpoints ordered by reliability. */
+const PUBLIC_RPC_ENDPOINTS = [
+  "https://base-rpc.publicnode.com",
+  "https://mainnet.base.org",
+  "https://base.drpc.org",
+  "https://base.llamarpc.com",
+  "https://base.meowrpc.com",
+  "https://developer-access-mainnet.base.org",
+  "https://base-mainnet.public.blastapi.io",
+  "https://1rpc.io/base",
+];
+
+export const RPC_ENDPOINTS = CUSTOM_RPC_URL
+  ? [CUSTOM_RPC_URL, ...PUBLIC_RPC_ENDPOINTS]
+  : PUBLIC_RPC_ENDPOINTS;
+
+/** Client-side CORS-enabled RPC endpoints for wagmi/browser. */
+const PUBLIC_CORS_ENDPOINTS = [
+  "https://mainnet.base.org",
+  "https://base-rpc.publicnode.com",
+  "https://base.drpc.org",
+  "https://base.llamarpc.com",
+  "https://base.meowrpc.com",
+];
+
+export const CORS_RPC_ENDPOINTS = CUSTOM_RPC_URL
+  ? [CUSTOM_RPC_URL, ...PUBLIC_CORS_ENDPOINTS]
+  : PUBLIC_CORS_ENDPOINTS;
+
+// ---------------------------------------------------------------------------
+// Transports
+// ---------------------------------------------------------------------------
+
+function buildServerTransport() {
+  if (!IS_MAINNET) {
+    return CUSTOM_RPC_URL ? fallback([http(CUSTOM_RPC_URL), http()]) : http();
+  }
+  return fallback(
+    RPC_ENDPOINTS.map((url) => http(url, { timeout: 10_000, retryCount: 1 })),
+    { rank: false },
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Public client
+// ---------------------------------------------------------------------------
 
 /**
  * Shared public client for reading from Base (or Base Sepolia).
- *
- * Chain is selected via NEXT_PUBLIC_CHAIN_ID (default: 84532 / Base Sepolia).
- * Uses NEXT_PUBLIC_RPC_URL with a fallback to the chain's default public RPC.
+ * On mainnet, uses fallback across multiple RPC endpoints.
  */
 export const publicClient = createPublicClient({
   chain,
-  transport,
+  transport: buildServerTransport(),
 });
 
+// ---------------------------------------------------------------------------
+// Exports for wagmi
+// ---------------------------------------------------------------------------
+
+/**
+ * Create a CORS-safe fallback transport for wagmi browser config.
+ * On testnet, returns a single http() transport.
+ */
+export function createFallbackTransport() {
+  if (!IS_MAINNET) {
+    return CUSTOM_RPC_URL ? fallback([http(CUSTOM_RPC_URL), http()]) : http();
+  }
+  return fallback(
+    CORS_RPC_ENDPOINTS.map((url) =>
+      http(url, {
+        timeout: 5_000,
+        retryCount: 0,
+        fetchOptions: { mode: "cors", credentials: "omit" },
+      }),
+    ),
+    { rank: false },
+  );
+}
+
+// ---------------------------------------------------------------------------
+// Server-side fallback helper
+// ---------------------------------------------------------------------------
+
+function getRpcDisplayName(url: string): string {
+  if (CUSTOM_RPC_URL && url === CUSTOM_RPC_URL) return "Custom RPC";
+  if (url.includes("publicnode.com")) return "PublicNode";
+  if (url.includes("mainnet.base.org")) return "Base Official";
+  if (url.includes("drpc.org")) return "DRPC";
+  if (url.includes("llamarpc.com")) return "LlamaRPC";
+  if (url.includes("meowrpc.com")) return "MeowRPC";
+  if (url.includes("1rpc.io")) return "1RPC";
+  if (url.includes("blastapi.io")) return "BlastAPI";
+  if (url.includes("developer-access")) return "Base Dev";
+  return "RPC";
+}
+
+/**
+ * Try an RPC operation against each endpoint until one succeeds.
+ * Use in server-side API routes for operations that need explicit
+ * per-endpoint fallback with logging.
+ */
+export async function withServerRpcFallback<T>(
+  operation: (client: PublicClient) => Promise<T>,
+  label?: string,
+): Promise<T> {
+  const endpoints = RPC_ENDPOINTS;
+  let lastError: Error | null = null;
+  const prefix = label ? `[RPC:${label}]` : "[RPC]";
+
+  for (let i = 0; i < endpoints.length; i++) {
+    const url = endpoints[i];
+    const name = getRpcDisplayName(url);
+    try {
+      const client = createPublicClient({
+        chain,
+        transport: http(url, { timeout: 10_000, retryCount: 0 }),
+      }) as PublicClient;
+      const result = await operation(client);
+      if (i > 0) console.log(`${prefix} Success with ${name} (attempt ${i + 1})`);
+      return result;
+    } catch (error) {
+      lastError = error as Error;
+      console.warn(`${prefix} ${name} failed: ${(lastError.message || "").slice(0, 100)}`);
+      if (i < endpoints.length - 1) {
+        await new Promise((r) => setTimeout(r, 100));
+      }
+    }
+  }
+
+  console.error(`${prefix} All ${endpoints.length} RPC endpoints failed`);
+  throw lastError || new Error("All RPC endpoints failed");
+}
+
+// ---------------------------------------------------------------------------
+// Receipt helper
+// ---------------------------------------------------------------------------
+
 /**
  * Fetch a transaction receipt with retries and backoff.
- * Load-balanced RPC nodes may not have the receipt immediately after
- * `waitForTransactionReceipt` completes on the client side.
+ * Uses the fallback-aware publicClient internally.
  */
 export async function getReceiptWithRetry(hash: Hex, maxAttempts = 5) {
   for (let attempt = 1; attempt <= maxAttempts; attempt++) {

lib/wagmi.ts

@@ -2,21 +2,16 @@ import { http, createConfig } from "wagmi";
 import { base, baseSepolia } from "wagmi/chains";
 import { injected } from "wagmi/connectors";
 import { farcasterMiniApp } from "@farcaster/miniapp-wagmi-connector";
+import { createFallbackTransport } from "./rpc";
+
+const IS_MAINNET = process.env.NEXT_PUBLIC_CHAIN_ID === "8453";
 
 export const config = createConfig({
   chains: [base, baseSepolia],
   connectors: [farcasterMiniApp(), injected()],
   transports: {
-    [base.id]: http(
-      process.env.NEXT_PUBLIC_CHAIN_ID === "8453"
-        ? process.env.NEXT_PUBLIC_RPC_URL
-        : undefined,
-    ),
-    [baseSepolia.id]: http(
-      process.env.NEXT_PUBLIC_CHAIN_ID !== "8453"
-        ? process.env.NEXT_PUBLIC_RPC_URL
-        : undefined,
-    ),
+    [base.id]: IS_MAINNET ? createFallbackTransport() : http(),
+    [baseSepolia.id]: IS_MAINNET ? http() : createFallbackTransport(),
   },
   ssr: true,
 });

packages/sdk/src/client.ts

@@ -2,6 +2,7 @@ import {
   createPublicClient,
   createWalletClient,
   http,
+  fallback,
   keccak256,
   toHex,
   decodeEventLog,
@@ -50,6 +51,8 @@ export interface PlotLinkConfig {
   privateKey: string;
   /** JSON-RPC URL for the Base chain. */
   rpcUrl: string;
+  /** Optional additional RPC URLs for fallback rotation (tried in order after rpcUrl). */
+  rpcUrls?: string[];
   /** Chain ID — defaults to 84532 (Base Sepolia). */
   chainId?: number;
   /** Override StoryFactory contract address. */
@@ -169,15 +172,21 @@ export class PlotLink {
       : `0x${config.privateKey}`;
     const account = privateKeyToAccount(normalizedKey as Hex);
 
+    const allUrls = [config.rpcUrl, ...(config.rpcUrls ?? [])];
+    const transport =
+      allUrls.length > 1
+        ? fallback(allUrls.map((url) => http(url, { timeout: 10_000, retryCount: 1 })), { rank: false })
+        : http(config.rpcUrl);
+
     this.publicClient = createPublicClient({
       chain: this.chain,
-      transport: http(config.rpcUrl),
+      transport,
     });
 
     this.walletClient = createWalletClient({
       account,
       chain: this.chain,
-      transport: http(config.rpcUrl),
+      transport,
     });
 
     this.address = account.address;

scripts/e2e-verify.ts

@@ -19,8 +19,8 @@ import { readFileSync } from "node:fs";
 import { resolve, dirname } from "node:path";
 import { createClient } from "@supabase/supabase-js";
 import { keccak256, toHex, formatUnits, decodeEventLog, type Address } from "viem";
-import { createPublicClient, http, fallback } from "viem";
 import { base, baseSepolia } from "viem/chains";
+import { publicClient } from "../lib/rpc";
 
 // ---------------------------------------------------------------------------
 // CLI args
@@ -154,14 +154,9 @@ interface BroadcastArtifact {
 const results: E2EResults = JSON.parse(readFileSync(resultsPath, "utf-8"));
 const artifactPath = resolve(dirname(resultsPath), results.broadcastArtifact);
 
-// Initialize chain from e2e-results.json (not env — ensures correct chain)
+// Chain from e2e-results.json (for display only — publicClient uses env config)
 const chainId = results.chainId;
 const resolvedChain = chainId === 8453 ? base : baseSepolia;
-const customRpc = process.env.NEXT_PUBLIC_RPC_URL;
-const publicClient = createPublicClient({
-  chain: resolvedChain,
-  transport: customRpc ? fallback([http(customRpc), http()]) : http(),
-});
 
 let broadcast: BroadcastArtifact;
 try {