diff --git a/.meteor/packages b/.meteor/packages
index ff3104c..bb09bc7 100644
--- a/.meteor/packages
+++ b/.meteor/packages
@@ -54,3 +54,4 @@ nspangler:autoreconnect
 quave:synced-cron
 # lmachens:kadira
 nimble:restivus@0.8.12
+underscore@1.6.4
diff --git a/.meteor/versions b/.meteor/versions
index 509413d..08a35df 100644
--- a/.meteor/versions
+++ b/.meteor/versions
@@ -120,7 +120,7 @@ themeteorchef:bert@1.1.0
 tmeasday:check-npm-versions@0.3.2
 tracker@1.3.4
 typescript@5.6.3
-underscore@1.6.2
+underscore@1.6.4
 url@1.3.5
 vjrj:piwik@0.3.1
 webapp@2.0.4
diff --git a/imports/startup/server/accounts/oauth.js b/imports/startup/server/accounts/oauth.js
index 545519a..bc541b4 100644
--- a/imports/startup/server/accounts/oauth.js
+++ b/imports/startup/server/accounts/oauth.js
@@ -4,10 +4,12 @@ import { ServiceConfiguration } from 'meteor/service-configuration';
 const OAuthSettings = Meteor.settings.private.OAuth;
 
 if (OAuthSettings) {
-  Object.keys(OAuthSettings).forEach((service) => {
-    ServiceConfiguration.configurations.upsert(
+  // Meteor 3: sync Mongo write-methods are gone on the server; use *Async.
+  // Top-level await is supported in eager server modules.
+  for (const service of Object.keys(OAuthSettings)) {
+    await ServiceConfiguration.configurations.upsertAsync(
       { service },
       { $set: OAuthSettings[service] },
     );
-  });
+  }
 }
diff --git a/imports/startup/server/email.js b/imports/startup/server/email.js
index 42752cd..8caf2f3 100644
--- a/imports/startup/server/email.js
+++ b/imports/startup/server/email.js
@@ -1,6 +1,6 @@
 import { Meteor } from 'meteor/meteor';
 import nodemailer from 'nodemailer';
-import { MailTime } from 'meteor/ostrio:mailer';
+import MailTime from 'meteor/ostrio:mailer';
 import i18n from 'i18next';
 import isMaster from './isMaster';
 
@@ -48,7 +48,8 @@ if (isMailServerMaster) {
     concatDelimiter: hr + '<h2>{{{subject}}}</h2>', // Start each concatenated email with it's own subject
     /* eslint-enable */
     // concatThrottling: 30,
-    template: MailTime.Template // Use default template
+    // Mail-Time 2.x removed the static MailTime.Template; omitting `template`
+    // uses the built-in default ('{{{html}}}'). (debt: richer wrapper template)
   });
 } else {
   console.log('I\'m a mail client');
diff --git a/imports/startup/server/facts.js b/imports/startup/server/facts.js
index 0c75843..02781f7 100644
--- a/imports/startup/server/facts.js
+++ b/imports/startup/server/facts.js
@@ -2,8 +2,4 @@
 import { Roles } from 'meteor/alanning:roles';
 import { Meteor } from 'meteor/meteor';
 
-Facts.setUserIdFilter((userId) => {
-  const user = Meteor.users.findOne(userId);
-  // console.log(`User roles: ${user.roles}`);
-  return Roles.userIsInRole(userId, ['admin']);
-});
+Facts.setUserIdFilter(userId => Roles.userIsInRole(userId, ['admin']));
diff --git a/imports/startup/server/fibers.js b/imports/startup/server/fibers.js
deleted file mode 100644
index ff96265..0000000
--- a/imports/startup/server/fibers.js
+++ /dev/null
@@ -1,7 +0,0 @@
-// Workaround for: https://github.com/meteor/meteor/issues/9796
-// https://github.com/meteor/meteor/issues/9796#issuecomment-381676326
-// https://github.com/sandstorm-io/sandstorm/blob/0f1fec013fe7208ed0fd97eb88b31b77e3c61f42/shell/server/00-startup.js#L99-L129
-
-import Fiber from 'fibers';
-
-Fiber.poolSize = 1e9;
diff --git a/imports/startup/server/index.js b/imports/startup/server/index.js
index 52d2b81..0e69fa7 100644
--- a/imports/startup/server/index.js
+++ b/imports/startup/server/index.js
@@ -1,6 +1,5 @@
 import './ravenLogger';
 import './catchExceptions';
-import './fibers';
 import './i18n';
 import './accounts';
 import './api';
diff --git a/imports/startup/server/migrations.js b/imports/startup/server/migrations.js
index 746a894..92301ad 100644
--- a/imports/startup/server/migrations.js
+++ b/imports/startup/server/migrations.js
@@ -14,7 +14,7 @@ import Notifications from '/imports/api/Notifications/Notifications';
 import ActiveFiresUnion from '/imports/api/ActiveFiresUnion/ActiveFiresUnion';
 import { Mongo } from 'meteor/mongo';
 
-Meteor.startup(() => {
+Meteor.startup(async () => {
   // https://github.com/percolatestudio/meteor-migrations
 
   Migrations.config({
@@ -255,7 +255,12 @@ Meteor.startup(() => {
   });
 
   // Set createdAt in users & subs
-  Migrations.migrateTo('latest');
+  // Meteor 3: migrateTo is async now.
+  // NOTE: the individual up() bodies below still use SYNC Mongo — they only run
+  // on a DB whose migration version is behind. Production data is restored from
+  // rsmain already at the latest version, so they never execute. If migrations
+  // must ever run on a truly-fresh DB, their up() bodies need async conversion.
+  await Migrations.migrateTo('latest');
 
   // Migrations.migrateTo('14,rerun');
 });
diff --git a/imports/startup/server/subsUnion.js b/imports/startup/server/subsUnion.js
index 2643359..0c78331 100644
--- a/imports/startup/server/subsUnion.js
+++ b/imports/startup/server/subsUnion.js
@@ -11,7 +11,7 @@ import { isMailServerMaster } from '/imports/startup/server/email';
 
 // sudo apt-get install libcairo2-dev libjpeg-dev libgif-dev
 
-Meteor.startup(() => {
+Meteor.startup(async () => {
   if (!isMailServerMaster) {
     console.log('We only process subsUnion in master');
     return;
@@ -35,8 +35,8 @@ Meteor.startup(() => {
 
   const noNoisy = sub => sub;
 
-  const process = (isPublic) => {
-    const subscribers = Subscriptions.find().fetch();
+  const process = async (isPublic) => {
+    const subscribers = await Subscriptions.find().fetchAsync();
     const result = calcUnion(L, subscribers, isPublic ? addNoisy : noNoisy, true);
     const union = result[0];
     const bounds = result[1];
@@ -74,9 +74,9 @@ Meteor.startup(() => {
       };
       // FIXME, take care of object size:
       // https://stackoverflow.com/questions/10827812/what-is-the-length-maximum-for-a-string-data-type-in-mongodb-used-with-ruby
-      SiteSettings.upsert({ name: `subs-${publicl}-union` }, unionSet, { multi: false });
-      SiteSettings.upsert({ name: `subs-${publicl}-union-bounds` }, boundsSet, { multi: false });
-      SiteSettings.upsert({ name: 'subs-union-count' }, sizeSet, { multi: false });
+      await SiteSettings.upsertAsync({ name: `subs-${publicl}-union` }, unionSet, { multi: false });
+      await SiteSettings.upsertAsync({ name: `subs-${publicl}-union-bounds` }, boundsSet, { multi: false });
+      await SiteSettings.upsertAsync({ name: 'subs-union-count' }, sizeSet, { multi: false });
       if (debug) console.log(`${Publicl} subscription union calculated`);
     } else {
       console.log('Subscription union failed!');
@@ -84,40 +84,39 @@ Meteor.startup(() => {
   };
 
   // At startup, we check if it's necessary to calc subscriptions union again
-  const currentUnion = SiteSettings.findOne({ name: 'subs-public-union' });
-  const lastSubs = Subscriptions.findOne({}, { sort: { updatedAt: -1 } });
-  const countUnionSubs = SiteSettings.findOne({ name: 'subs-union-count' });
-  const countSubs = Subscriptions.find({}).count();
+  const currentUnion = await SiteSettings.findOneAsync({ name: 'subs-public-union' });
+  const lastSubs = await Subscriptions.findOneAsync({}, { sort: { updatedAt: -1 } });
+  const countUnionSubs = await SiteSettings.findOneAsync({ name: 'subs-union-count' });
+  const countSubs = await Subscriptions.find({}).countAsync();
   if (currentUnion && lastSubs) {
     const lastUnionUpdated = currentUnion.updatedAt;
     const lastSubsUpdated = lastSubs.updatedAt;
     if (lastUnionUpdated > lastSubsUpdated || !countUnionSubs || countSubs !== countUnionSubs.value) {
       console.log('Subs union outdated');
-      process(true);
-      process(false);
+      await process(true);
+      await process(false);
     } else {
       console.log('Subs union up-to-date');
     }
   }
 
-  Subscriptions.find({ createdAt: { $gt: new Date() } }).observe({
-    added: function newSubAdded() { // doc) {
+  const recreate = async () => { await process(true); await process(false); };
+
+  await Subscriptions.find({ createdAt: { $gt: new Date() } }).observeAsync({
+    added: async function newSubAdded() { // doc) {
       if (debug) console.log('Subs added so recreate union');
-      process(true);
-      process(false);
+      await recreate();
     }
   });
 
-  Subscriptions.find().observe({
-    changed: function subsChanged() { // updatedDoc, oldDoc) {
+  await Subscriptions.find().observeAsync({
+    changed: async function subsChanged() { // updatedDoc, oldDoc) {
       if (debug) console.log('Subs changed so recreate union');
-      process(true);
-      process(false);
+      await recreate();
     },
-    removed: function subsRemoved() { // oldDoc) {
+    removed: async function subsRemoved() { // oldDoc) {
       if (debug) console.log('Subs removed so recreate union');
-      process(true);
-      process(false);
+      await recreate();
     }
   });
 });