diff --git a/cli/tsc/dts/node/globals.d.cts b/cli/tsc/dts/node/globals.d.cts
index 8f31a4c6b0aab7..be0f387d741478 100644
--- a/cli/tsc/dts/node/globals.d.cts
+++ b/cli/tsc/dts/node/globals.d.cts
@@ -2,19 +2,21 @@ export {}; // Make this a module
 
 // #region Fetch and friends
 // Conditional type aliases, used at the end of this file.
-// Will either be empty if lib.dom (or lib.webworker) is included, or the undici version otherwise.
-type _Request = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").Request;
-type _Response = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").Response;
-type _FormData = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").FormData;
-type _Headers = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").Headers;
-type _MessageEvent = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").MessageEvent;
-type _RequestInit = typeof globalThis extends { onmessage: any } ? {}
+// Deno's web globals don't expose `onmessage` on `globalThis` outside of
+// worker contexts, so detect Deno's web fetch surface via `Blob` instead.
+type _HasWebFetchGlobals = typeof globalThis extends { Blob: any } ? true : false;
+type _Request = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").Request;
+type _Response = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").Response;
+type _FormData = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").FormData;
+type _Headers = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").Headers;
+type _MessageEvent = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").MessageEvent;
+type _RequestInit = _HasWebFetchGlobals extends true ? {}
     : import("./undici/index.d.ts").RequestInit;
-type _ResponseInit = typeof globalThis extends { onmessage: any } ? {}
+type _ResponseInit = _HasWebFetchGlobals extends true ? {}
     : import("./undici/index.d.ts").ResponseInit;
-type _WebSocket = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").WebSocket;
-type _EventSource = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").EventSource;
-type _CloseEvent = typeof globalThis extends { onmessage: any } ? {} : import("./undici/index.d.ts").CloseEvent;
+type _WebSocket = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").WebSocket;
+type _EventSource = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").EventSource;
+type _CloseEvent = _HasWebFetchGlobals extends true ? {} : import("./undici/index.d.ts").CloseEvent;
 // #endregion Fetch and friends
 
 // Conditional type definitions for webstorage interface, which conflicts with lib.dom otherwise.
diff --git a/tests/integration/lsp_tests.rs b/tests/integration/lsp_tests.rs
index 62ce133339976f..849eddc032a34a 100644
--- a/tests/integration/lsp_tests.rs
+++ b/tests/integration/lsp_tests.rs
@@ -17545,6 +17545,30 @@ fn lsp_tsconfig_node_modules_dts_diagnostics() {
   client.shutdown();
 }
 
+// Regression test for #33012: the @types/node `globals.d.cts` heuristic for
+// detecting the web fetch surface used `onmessage`, which isn't on Deno's
+// `globalThis` outside of workers, so LSP would fall back to undici types
+// for `RequestInit` and reject otherwise-valid `new Request(url, init)`.
+#[test(timeout = 300)]
+fn lsp_request_init_global_matches_check() {
+  let context = TestContextBuilder::new().use_temp_cwd().build();
+  let temp_dir = context.temp_dir();
+  temp_dir.write("deno.json", json!({}).to_string());
+  let file = temp_dir.source_file(
+    "main.ts",
+    concat!(
+      "const init: Parameters<typeof fetch>[1] = {};\n",
+      "const _request = new Request(\"https://deno.com\", init);\n",
+      "console.log(_request);\n",
+    ),
+  );
+  let mut client = context.new_lsp_command().build();
+  client.initialize_default();
+  let diagnostics = client.did_open_file(&file);
+  assert_eq!(diagnostics.all(), vec![]);
+  client.shutdown();
+}
+
 #[test(timeout = 300)]
 fn lsp_tsconfig_root_dirs() {
   let context = TestContextBuilder::new()
diff --git a/tools/update_types_node.ts b/tools/update_types_node.ts
index f988614f86089b..d761105ad754f7 100755
--- a/tools/update_types_node.ts
+++ b/tools/update_types_node.ts
@@ -14,6 +14,7 @@ import {
   Node,
   Project,
   ScriptTarget,
+  SourceFile,
   SyntaxKind,
   VariableDeclaration,
 } from "jsr:@ts-morph/ts-morph@27.0.2";
@@ -260,11 +261,53 @@ function modifySourceFiles() {
         ),
       );
     }
+
+    // Detect Deno's web fetch surface via `Blob` instead of `onmessage`.
+    // `onmessage` only exists on `globalThis` in worker contexts, so the
+    // upstream heuristic falls back to undici's types in regular Deno code
+    // and breaks LSP type checks against `RequestInit` etc. (denoland/deno#33012).
+    if (sourceFile.getBaseName() === "globals.d.cts") {
+      rewriteFetchGlobalsDiscriminator(sourceFile);
+    }
   }
 
   project.saveSync();
 }
 
+function rewriteFetchGlobalsDiscriminator(sourceFile: SourceFile) {
+  const startMarker = "// #region Fetch and friends\n";
+  const endMarker = "// #endregion Fetch and friends\n";
+  const text = sourceFile.getFullText();
+  const start = text.indexOf(startMarker);
+  const end = text.indexOf(endMarker);
+  if (start === -1 || end === -1) {
+    return;
+  }
+  const blockStart = start + startMarker.length;
+  const blockBody = text.slice(blockStart, end);
+  if (!blockBody.includes("{ onmessage: any }")) {
+    return;
+  }
+  const rewritten = blockBody
+    .replace(
+      "// Conditional type aliases, used at the end of this file.\n" +
+        "// Will either be empty if lib.dom (or lib.webworker) is included, " +
+        "or the undici version otherwise.\n",
+      "// Conditional type aliases, used at the end of this file.\n" +
+        "// Deno's web globals don't expose `onmessage` on `globalThis` " +
+        "outside of\n" +
+        "// worker contexts, so detect Deno's web fetch surface via `Blob` " +
+        "instead.\n" +
+        "type _HasWebFetchGlobals = typeof globalThis extends { Blob: any } " +
+        "? true : false;\n",
+    )
+    .replaceAll(
+      "typeof globalThis extends { onmessage: any }",
+      "_HasWebFetchGlobals extends true",
+    );
+  sourceFile.replaceText([blockStart, end], rewritten);
+}
+
 function handleInterface(decl: InterfaceDeclaration) {
   switch (decl.getName()) {
     case "ImportMeta": {