Don't apply async-await plugin and don't modify promise functions.

npm-packages/meteor-babel/options.js

@@ -185,11 +185,13 @@ function getDefaultsForNode8(features) {
 
     // Ensure that async functions run in a Fiber, while also taking
     // full advantage of native async/await support in Node 8.
-    combined.plugins.push([require("./plugins/async-await.js"), {
-      // Do not transform `await x` to `Promise.await(x)`, since Node
-      // 8 has native support for await expressions.
-      useNativeAsyncAwait: false
-    }]);
+    if (!process.env.DISABLE_FIBERS) {
+      combined.plugins.push([require("./plugins/async-await.js"), {
+        // Do not transform `await x` to `Promise.await(x)`, since Node
+        // 8 has native support for await expressions.
+        useNativeAsyncAwait: false
+      }]);
+    }
 
     // Enable async generator functions proposal.
     combined.plugins.push(require("@babel/plugin-proposal-async-generator-functions"));

npm-packages/meteor-babel/runtime.js

@@ -11,19 +11,21 @@ Module.prototype.resolve = function (id) {
 
 require("@meteorjs/reify/lib/runtime").enable(Module.prototype);
 
-require("meteor-promise").makeCompatible(
-  global.Promise = global.Promise ||
-    require("promise/lib/es6-extensions"),
-  require("fibers")
-);
+if (!process.env.DISABLE_FIBERS) {
+  require("meteor-promise").makeCompatible(
+      global.Promise = global.Promise ||
+          require("promise/lib/es6-extensions"),
+      require("fibers")
+  );
 
 // If Promise.asyncApply is defined, use it to wrap calls to
 // regeneratorRuntime.async so that the entire async function will run in
 // its own Fiber, not just the code that comes after the first await.
-if (typeof Promise.asyncApply === "function") {
-  var regeneratorRuntime = require("@babel/runtime/regenerator");
-  var realAsync = regeneratorRuntime.async;
-  regeneratorRuntime.async = function (innerFn) {
-    return Promise.asyncApply(realAsync, regeneratorRuntime, arguments);
-  };
+  if (typeof Promise.asyncApply === "function") {
+    var regeneratorRuntime = require("@babel/runtime/regenerator");
+    var realAsync = regeneratorRuntime.async;
+    regeneratorRuntime.async = function (innerFn) {
+      return Promise.asyncApply(realAsync, regeneratorRuntime, arguments);
+    };
+  }
 }

packages/promise/server.js

@@ -1,11 +1,13 @@
 require("./extensions.js");
 
-require("meteor-promise").makeCompatible(
-  Promise,
-  // Allow every Promise callback to run in a Fiber drawn from a pool of
-  // reusable Fibers.
-  require("fibers")
-);
+if (!process.env.DISABLE_FIBERS) {
+  require("meteor-promise").makeCompatible(
+      Promise,
+      // Allow every Promise callback to run in a Fiber drawn from a pool of
+      // reusable Fibers.
+      require("fibers")
+  );
+}
 
 // Reference: https://caniuse.com/#feat=promises
 require("meteor/modern-browsers").setMinimumBrowserVersions({