diff --git a/packages/api/src/app.ts b/packages/api/src/app.ts
index dfedc702..23e08e16 100644
--- a/packages/api/src/app.ts
+++ b/packages/api/src/app.ts
@@ -1,4 +1,4 @@
-import { NETWORK_NAME_TO_CHAIN_ID, NetworkName } from "types/lib";
+import { NetworkName } from "types/lib";
 import { IDbController } from "types/lib";
 import { Executor } from "executor/lib/executor";
 import { Config } from "executor/lib/config";
@@ -58,24 +58,21 @@ export class ApiApp {
 
   private setupRoutes(): void {
     if (this.testingMode) {
-      this.server.post("/rpc/", this.setupRouteFor("dev"));
+      this.server.post("/rpc/", this.setupRouteFor("dev", 1337));
       logger.info("Setup route for dev: /rpc/");
       return;
     }
 
-    const networkNames: NetworkName[] = this.config.supportedNetworks;
-    for (const network of networkNames) {
-      const chainId: number | undefined = NETWORK_NAME_TO_CHAIN_ID[network];
-      if (chainId == undefined) {
-        continue;
-      }
-      this.server.post(`/${chainId}`, this.setupRouteFor(network));
+    const networkNames = this.config.supportedNetworks;
+    for (const [network, chainId] of Object.entries(networkNames)) {
+      this.server.post(`/${chainId}`, this.setupRouteFor(network, chainId));
       logger.info(`Setup route for ${network}: /${chainId}/`);
     }
   }
 
-  private setupRouteFor(network: NetworkName): RouteHandler {
+  private setupRouteFor(network: NetworkName, chainId: number): RouteHandler {
     const relayer = new Executor({
+      chainId,
       network,
       db: this.db,
       config: this.config,
diff --git a/packages/cli/src/cmds/start/handler.ts b/packages/cli/src/cmds/start/handler.ts
index dc263e37..04666e43 100644
--- a/packages/cli/src/cmds/start/handler.ts
+++ b/packages/cli/src/cmds/start/handler.ts
@@ -41,6 +41,8 @@ export async function bundlerHandler(
     });
   }
 
+  await config.fetchChainIds();
+
   if (unsafeMode) {
     logger.warn(
       "WARNING: Running in unsafe mode, skips opcode check and stake check"
diff --git a/packages/executor/src/config.ts b/packages/executor/src/config.ts
index ff038359..d783f742 100644
--- a/packages/executor/src/config.ts
+++ b/packages/executor/src/config.ts
@@ -1,5 +1,6 @@
 // TODO: create a new package "config" instead of this file and refactor
 import { Wallet, providers, utils } from "ethers";
+import { NetworkName } from "types/lib";
 import {
   BundlerConfig,
   ConfigOptions,
@@ -8,7 +9,9 @@ import {
 } from "./interfaces";
 
 export class Config {
-  supportedNetworks: string[];
+  supportedNetworks: {
+    [networkName in NetworkName]: number;
+  };
   networks: Networks;
   testingMode: boolean;
   unsafeMode: boolean;
@@ -64,20 +67,35 @@ export class Config {
     return config;
   }
 
-  private parseSupportedNetworks(): string[] {
+  async fetchChainIds(): Promise<void> {
+    for (const networkName of Object.keys(this.supportedNetworks)) {
+      const provider = this.getNetworkProvider(networkName);
+      if (!provider) {
+        throw new Error(`No provider for ${networkName}`);
+      }
+      const network = await provider.getNetwork();
+      this.supportedNetworks[networkName] = network.chainId;
+    }
+  }
+
+  private parseSupportedNetworks(): { [name: string]: number } {
     if (this.testingMode) {
-      return ["dev"];
+      return { dev: 1337 };
     }
     const envNetworks = NETWORKS_ENV();
-    if (envNetworks) {
-      return envNetworks;
+    let networkNames = envNetworks;
+    if (!networkNames) {
+      networkNames = Object.keys(this.config.networks);
     }
-    return Object.keys(this.config.networks);
+    return networkNames.reduce((networks, networkName) => {
+      networks[networkName] = 0;
+      return networks;
+    }, {} as { [name: string]: number });
   }
 
   private parseNetworkConfigs(): Networks {
     const networks: Networks = {};
-    for (const network of this.supportedNetworks) {
+    for (const network of Object.keys(this.supportedNetworks)) {
       const config = this.getDefaultNetworkConfig(network);
       networks[network] = {
         ...config,
diff --git a/packages/executor/src/executor.ts b/packages/executor/src/executor.ts
index a6ca2d63..361e815b 100644
--- a/packages/executor/src/executor.ts
+++ b/packages/executor/src/executor.ts
@@ -57,10 +57,9 @@ export class Executor {
       this.networkName
     ) as providers.JsonRpcProvider;
 
-    const chainId = this.provider.network.chainId;
     this.reputationService = new ReputationService(
       this.db,
-      chainId,
+      this.chainId,
       this.networkConfig.minInclusionDenominator,
       this.networkConfig.throttlingSlack,
       this.networkConfig.banSlack,
@@ -77,7 +76,7 @@ export class Executor {
     );
     this.mempoolService = new MempoolService(
       this.db,
-      chainId,
+      this.chainId,
       this.reputationService
     );
     this.bundlingService = new BundlingService(