fix(maticjs): disable HTTP keep-alive on metadata fetches to fix Premature close

.changeset/maticjs-disable-keepalive.md

@@ -0,0 +1,7 @@
+---
+'@maticnetwork/maticjs': patch
+---
+
+Disable HTTP keep-alive on the network-config and ABI metadata fetches to fix intermittent `FetchError: Premature close` failures.
+
+Node 19+ enables HTTP keep-alive by default. node-fetch then reuses a connection the upstream CDN has already idle-closed, and the next gzip response fails mid-decompression — surfacing as the misleading `network <net> - <ver> is not supported`. It reproduces 100% from datacenter/CI egress and intermittently elsewhere. These fetches run once per client init and are cached, so opening a fresh connection per request only costs a TLS handshake at startup. This complements the transient-retry added in #481, which could not recover when every reused socket was already stale. The browser build is unaffected (`window.fetch` ignores the agent).

packages/maticjs/src/utils/http_request.ts

@@ -1,12 +1,34 @@
 import { retryTransient } from './retry';
 
-const fetch: (input: RequestInfo, init?: RequestInit) => Promise<Response> = (() => {
+// node-fetch supports an `agent` option that the DOM lib's RequestInit lacks.
+type FetchInit = RequestInit & { agent?: unknown };
+
+const fetch: (input: RequestInfo, init?: FetchInit) => Promise<Response> = (() => {
   if (process.env.BUILD_ENV === 'node') {
     return require('node-fetch').default;
   }
   return window.fetch;
 })();
 
+// Force a non-keep-alive HTTP agent in the Node build. Node 19+ defaults http(s)
+// agents to keepAlive:true; node-fetch then reuses a socket the upstream CDN
+// (Cloudflare) has already idle-closed, and the next gzip response dies
+// mid-decompression as `FetchError: Premature close` — observed 100% from CI,
+// intermittently elsewhere. These network-config and ABI fetches run once per
+// client init and are cached, so a fresh connection per request costs only a TLS
+// handshake at startup. The browser build's `window.fetch` ignores `agent`, and
+// node:http/https are required only inside the BUILD_ENV==='node' branch so they
+// are never bundled for the browser.
+const requestAgent: unknown = (() => {
+  if (process.env.BUILD_ENV === 'node') {
+    const httpAgent = new (require('http').Agent)({ keepAlive: false });
+    const httpsAgent = new (require('https').Agent)({ keepAlive: false });
+    return (parsedUrl: { protocol: string }) =>
+      parsedUrl.protocol === 'http:' ? httpAgent : httpsAgent;
+  }
+  return undefined;
+})();
+
 // Fail with the HTTP status / body on a non-2xx or non-JSON response instead of
 // letting a bare `res.json()` throw a context-free parse error.
 async function parseJsonResponse<T>(res: Response, method: string, url: string): Promise<T> {
@@ -53,7 +75,8 @@ export class HttpRequest {
         headers: {
           'Content-Type': 'application/json',
           Accept: 'application/json'
-        }
+        },
+        agent: requestAgent
       }).then((res) => parseJsonResponse<T>(res, 'GET', fullUrl))
     );
   }
@@ -68,7 +91,8 @@ export class HttpRequest {
           'Content-Type': 'application/json',
           Accept: 'application/json'
         },
-        body: body ? JSON.stringify(body) : null
+        body: body ? JSON.stringify(body) : null,
+        agent: requestAgent
       }).then((res) => parseJsonResponse(res, 'POST', fullUrl))
     );
   }

packages/maticjs/webpack.config.js

@@ -54,7 +54,12 @@ const clientConfig = {
   },
   resolve: {
     modules: [path.resolve(__dirname, 'src'), 'node_modules'],
-    extensions: ['.json', '.js', '.ts', '.tsx']
+    extensions: ['.json', '.js', '.ts', '.tsx'],
+    // `http`/`https` are referenced only in the Node build (guarded by
+    // BUILD_ENV==='node') to build a keep-alive-disabled agent. The web/UMD
+    // bundles never execute that branch, so map the modules to empty stubs
+    // rather than letting webpack fail trying to resolve Node core modules.
+    fallback: { http: false, https: false }
   },
   plugins: [
     new copyPlugin({