diff --git a/includes/resourceloader/ResourceLoader.php b/includes/resourceloader/ResourceLoader.php
index a0acf1f30bb..637bae640af 100644
--- a/includes/resourceloader/ResourceLoader.php
+++ b/includes/resourceloader/ResourceLoader.php
@@ -1484,7 +1484,7 @@ MESSAGE;
 	}
 
 	/**
-	 * Wraps JavaScript code to run after startup and base modules.
+	 * Wraps JavaScript code to run after the startup module.
 	 *
 	 * @param string $script JavaScript code
 	 * @return string JavaScript code
diff --git a/includes/resourceloader/ResourceLoaderStartUpModule.php b/includes/resourceloader/ResourceLoaderStartUpModule.php
index a4fd71233f7..53c10df4b1a 100644
--- a/includes/resourceloader/ResourceLoaderStartUpModule.php
+++ b/includes/resourceloader/ResourceLoaderStartUpModule.php
@@ -319,17 +319,6 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		return true;
 	}
 
-	/**
-	 * @param ResourceLoaderContext $context
-	 * @return array
-	 */
-	public function getPreloadLinks( ResourceLoaderContext $context ) {
-		$url = $this->getBaseModulesUrl( $context );
-		return [
-			$url => [ 'as' => 'script' ]
-		];
-	}
-
 	/**
 	 * Internal modules used by ResourceLoader that cannot be depended on.
 	 *
@@ -353,10 +342,18 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		return [];
 	}
 
+	/**
+	 * @private For internal use by SpecialJavaScriptTest
+	 * @since 1.32
+	 * @return array
+	 */
+	public function getBaseModulesInternal() {
+		return $this->getBaseModules();
+	}
+
 	/**
 	 * Base modules implicitly available to all modules.
 	 *
-	 * @since 1.32
 	 * @return array
 	 */
 	private function getBaseModules() {
@@ -370,25 +367,6 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 		return $baseModules;
 	}
 
-	/**
-	 * Get the load URL of the startup modules.
-	 *
-	 * This is a helper for getScript().
-	 *
-	 * @param ResourceLoaderContext $context
-	 * @return string
-	 */
-	private function getBaseModulesUrl( ResourceLoaderContext $context ) {
-		$rl = $context->getResourceLoader();
-		$derivative = new DerivativeResourceLoaderContext( $context );
-		$derivative->setModules( $this->getBaseModules() );
-		$derivative->setOnly( 'scripts' );
-		// Must setModules() before makeVersionQuery()
-		$derivative->setVersion( $rl->makeVersionQuery( $derivative ) );
-
-		return $rl->createLoaderURL( 'local', $derivative );
-	}
-
 	/**
 	 * @param ResourceLoaderContext $context
 	 * @return string JavaScript code
@@ -399,35 +377,43 @@ class ResourceLoaderStartUpModule extends ResourceLoaderModule {
 			return '/* Requires only=script */';
 		}
 
-		$out = file_get_contents( "$IP/resources/src/startup/startup.js" );
+		$startupCode = file_get_contents( "$IP/resources/src/startup/startup.js" );
 
-		// Keep in sync with maintenance/jsduck/eg-iframe.html and,
-		// keep in sync with 'fileHashes' in StartUpModule::getDefinitionSummary().
+		// The files read here MUST be kept in sync with maintenance/jsduck/eg-iframe.html,
+		// and MUST be considered by 'fileHashes' in StartUpModule::getDefinitionSummary().
 		$mwLoaderCode = file_get_contents( "$IP/resources/src/startup/mediawiki.js" ) .
 			file_get_contents( "$IP/resources/src/startup/mediawiki.requestIdleCallback.js" );
 		if ( $context->getDebug() ) {
 			$mwLoaderCode .= file_get_contents( "$IP/resources/src/startup/mediawiki.log.js" );
 		}
 
-		$pairs = array_map( function ( $value ) {
+		$mapToJson = function ( $value ) {
 			$value = FormatJson::encode( $value, ResourceLoader::inDebugMode(), FormatJson::ALL_OK );
 			// Fix indentation
 			$value = str_replace( "\n", "\n\t", $value );
 			return $value;
-		}, [
+		};
+
+		// Perform replacements for mediawiki.js
+		$mwLoaderCode = strtr( $mwLoaderCode, [
+			'$VARS.baseModules' => $mapToJson( $this->getBaseModules() ),
+		] );
+
+		// Perform replacements for startup.js
+		$pairs = array_map( $mapToJson, [
 			'$VARS.wgLegacyJavaScriptGlobals' => $this->getConfig()->get( 'LegacyJavaScriptGlobals' ),
 			'$VARS.configuration' => $this->getConfigSettings( $context ),
-			// This url may be preloaded. See getPreloadLinks().
-			'$VARS.baseModulesUri' => $this->getBaseModulesUrl( $context ),
 		] );
+		// Raw JavaScript code (not for JSON)
 		$pairs['$CODE.registrations();'] = str_replace(
 			"\n",
 			"\n\t",
 			trim( $this->getModuleRegistrations( $context ) )
 		);
 		$pairs['$CODE.defineLoader();'] = $mwLoaderCode;
+		$startupCode = strtr( $startupCode, $pairs );
 
-		return strtr( $out, $pairs );
+		return $startupCode;
 	}
 
 	/**
diff --git a/includes/specials/SpecialJavaScriptTest.php b/includes/specials/SpecialJavaScriptTest.php
index b786c869fb6..f858f5c2cd3 100644
--- a/includes/specials/SpecialJavaScriptTest.php
+++ b/includes/specials/SpecialJavaScriptTest.php
@@ -103,65 +103,56 @@ class SpecialJavaScriptTest extends SpecialPage {
 		$query['only'] = 'scripts';
 		$startupContext = new ResourceLoaderContext( $rl, new FauxRequest( $query ) );
 
-		$query['raw'] = true;
-
 		$modules = $rl->getTestModuleNames( 'qunit' );
 
 		// Disable autostart because we load modules asynchronously. By default, QUnit would start
 		// at domready when there are no tests loaded and also fire 'QUnit.done' which then instructs
-		// Karma to end the run before the tests even started.
+		// Karma to exit the browser process before the tests even finished loading.
 		$qunitConfig = 'QUnit.config.autostart = false;'
 			. 'if (window.__karma__) {'
 			// karma-qunit's use of autostart=false and QUnit.start conflicts with ours.
-			// Hack around this by replacing 'karma.loaded' with a no-op and call it ourselves later.
-			// See <https://github.com/karma-runner/karma-qunit/issues/27>.
+			// Hack around this by replacing 'karma.loaded' with a no-op and perfom its duty of calling
+			// `__karma__.start()` ourselves. See <https://github.com/karma-runner/karma-qunit/issues/27>.
 			. 'window.__karma__.loaded = function () {};'
 			. '}';
 
 		// The below is essentially a pure-javascript version of OutputPage::headElement().
-		$startup = $rl->makeModuleResponse( $startupContext, [
+		$code = $rl->makeModuleResponse( $startupContext, [
 			'startup' => $rl->getModule( 'startup' ),
 		] );
-		// Embed page-specific mw.config variables.
-		// The current Special page shouldn't be relevant to tests, but various modules (which
-		// are loaded before the test suites), reference mw.config while initialising.
-		$code = ResourceLoader::makeConfigSetScript( $out->getJSVars() );
-		// Embed private modules as they're not allowed to be loaded dynamically
-		$code .= $rl->makeModuleResponse( $embedContext, [
-			'user.options' => $rl->getModule( 'user.options' ),
-			'user.tokens' => $rl->getModule( 'user.tokens' ),
-		] );
-		// Catch exceptions (such as "dependency missing" or "unknown module") so that we
-		// always start QUnit. Re-throw so that they are caught and reported as global exceptions
-		// by QUnit and Karma.
-		$modules = Xml::encodeJsVar( $modules );
-		$code .= <<<CODE
-(function () {
+		// The following has to be deferred via RLQ because the startup module is asynchronous.
+		$code .= ResourceLoader::makeLoaderConditionalScript(
+			// Embed page-specific mw.config variables.
+			// The current Special page shouldn't be relevant to tests, but various modules (which
+			// are loaded before the test suites), reference mw.config while initialising.
+			ResourceLoader::makeConfigSetScript( $out->getJSVars() )
+			// Embed private modules as they're not allowed to be loaded dynamically
+			. $rl->makeModuleResponse( $embedContext, [
+				'user.options' => $rl->getModule( 'user.options' ),
+				'user.tokens' => $rl->getModule( 'user.tokens' ),
+			] )
+			// Load all the test suites
+			. Xml::encodeJsCall( 'mw.loader.load', [ $modules ] )
+		);
+		$encModules = Xml::encodeJsVar( $modules );
+		$code .= ResourceLoader::makeInlineCodeWithModule( 'mediawiki.base', <<<JAVASCRIPT
 	var start = window.__karma__ ? window.__karma__.start : QUnit.start;
-	try {
-		mw.loader.using( $modules )
-			.always( function () {
-				start();
-			} )
-			.fail( function ( e ) {
-				setTimeout( function () {
-					throw e;
-				} );
-			} );
-	} catch ( e ) {
-		start();
-		throw e;
-	}
-}());
-CODE;
+	mw.loader.using( $encModules ).always( start );
+	mw.trackSubscribe( 'resourceloader.exception', function ( topic, err ) {
+		// Things like "dependency missing" or "unknown module".
+		// Re-throw so that they are reported as global exceptions by QUnit and Karma.
+		setTimeout( function () {
+			throw e;
+		} );
+	} );
+JAVASCRIPT
+	);
 
 		header( 'Content-Type: text/javascript; charset=utf-8' );
 		header( 'Cache-Control: private, no-cache, must-revalidate' );
 		header( 'Pragma: no-cache' );
 		echo $qunitConfig;
-		echo $startup;
-		// The following has to be deferred via RLQ because the startup module is asynchronous.
-		echo ResourceLoader::makeLoaderConditionalScript( $code );
+		echo $code;
 	}
 
 	private function plainQUnit() {
diff --git a/maintenance/jsduck/eg-iframe.html b/maintenance/jsduck/eg-iframe.html
index 2c7cd68823a..7913aab83b6 100644
--- a/maintenance/jsduck/eg-iframe.html
+++ b/maintenance/jsduck/eg-iframe.html
@@ -35,7 +35,9 @@
 	</script>
 	<script>
 		// Mock startup.js
-		var mwNow = Date.now;
+		window.$VARS = {
+			baseModules: []
+		};
 
 		function startUp() {
 			mw.config = new mw.Map();
diff --git a/resources/Resources.php b/resources/Resources.php
index c63eb96cf28..a06a25f2667 100644
--- a/resources/Resources.php
+++ b/resources/Resources.php
@@ -143,7 +143,6 @@ return [
 			'resources/lib/jquery/jquery.js',
 			'resources/lib/jquery/jquery.migrate.js',
 		],
-		'raw' => true,
 		'targets' => [ 'desktop', 'mobile' ],
 	],
 
@@ -834,11 +833,14 @@ return [
 	/* MediaWiki */
 
 	'mediawiki.base' => [
-		// Keep in sync with maintenance/jsduck/eg-iframe.html
 		'scripts' => [
+			// This MUST be kept in sync with maintenance/jsduck/eg-iframe.html
 			'resources/src/mediawiki.base/mediawiki.errorLogger.js',
 			'resources/src/mediawiki.base/mediawiki.base.js',
 		],
+		// - These dependencies MUST NOT also have dependencies (would cause recursion).
+		// - These dependencies MUST also be returned from StartUpModule::getBaseModules().
+		'dependencies' => 'jquery',
 		'targets' => [ 'desktop', 'mobile' ],
 	],
 	'mediawiki.apihelp' => [
diff --git a/resources/lib/jquery/jquery.migrate.js b/resources/lib/jquery/jquery.migrate.js
index 992a734b293..711e424a397 100644
--- a/resources/lib/jquery/jquery.migrate.js
+++ b/resources/lib/jquery/jquery.migrate.js
@@ -3,6 +3,9 @@
  * Copyright jQuery Foundation and other contributors
  *
  * Patched for MediaWiki:
+ * - Qualify the global lookup for 'jQuery' as 'window.jQuery',
+ *   because within mw.loader.implement() for 'jquery', the closure
+ *   specifies '$' and 'jQuery', which are undefined.
  * - Add mw.track instrumentation for statistics.
  * - Disable jQuery.migrateTrace by default. They are slow and
  *   redundant given console.warn() already provides a trace.
@@ -20,7 +23,8 @@
 	} else {
 
 		// Browser globals
-		factory( jQuery, window );
+		// PATCH: Qualify jQuery lookup as window.jQuery. --Krinkle
+		factory( window.jQuery, window );
 	}
 } )( function( jQuery, window ) {
 "use strict";
diff --git a/resources/src/mediawiki.base/mediawiki.base.js b/resources/src/mediawiki.base/mediawiki.base.js
index 1c3dde6df04..9536b678d9d 100644
--- a/resources/src/mediawiki.base/mediawiki.base.js
+++ b/resources/src/mediawiki.base/mediawiki.base.js
@@ -22,7 +22,8 @@
 		mwLoaderTrack = mw.track,
 		trackCallbacks = $.Callbacks( 'memory' ),
 		trackHandlers = [],
-		hasOwn = Object.prototype.hasOwnProperty;
+		hasOwn = Object.prototype.hasOwnProperty,
+		queue;
 
 	/**
 	 * Object constructor for messages.
@@ -642,4 +643,17 @@
 	// Alias $j to jQuery for backwards compatibility
 	// @deprecated since 1.23 Use $ or jQuery instead
 	mw.log.deprecate( window, '$j', $, 'Use $ or jQuery instead.' );
+
+	// Process callbacks for Grade A that require modules.
+	// Plain ones were already processed by startup.js.
+	queue = window.RLQ;
+	// Redefine publicly to capture any late arrivals
+	window.RLQ = {
+		push: function ( entry ) {
+			mw.loader.using( entry[ 0 ], entry[ 1 ] );
+		}
+	};
+	while ( queue[ 0 ] ) {
+		window.RLQ.push( queue.shift() );
+	}
 }() );
diff --git a/resources/src/startup/mediawiki.js b/resources/src/startup/mediawiki.js
index e2db9ea30c7..351acc321a3 100644
--- a/resources/src/startup/mediawiki.js
+++ b/resources/src/startup/mediawiki.js
@@ -7,6 +7,7 @@
  * @alternateClassName mediaWiki
  * @singleton
  */
+/* global $VARS */
 
 ( function () {
 	'use strict';
@@ -618,6 +619,12 @@
 				 */
 				jobs = [],
 
+				/**
+				 * @private
+				 * @property {Array} baseModules
+				 */
+				baseModules = $VARS.baseModules,
+
 				/**
 				 * For #addEmbeddedCSS() and #addLink()
 				 *
@@ -744,6 +751,18 @@
 				return true;
 			}
 
+			/**
+			 * Determine whether all direct and base dependencies are in state 'ready'
+			 *
+			 * @private
+			 * @param {string} module Name of the module to be checked
+			 * @return {boolean} True if all direct/base dependencies are in state 'ready'; false otherwise
+			 */
+			function allWithImplicitReady( module ) {
+				return allReady( registry[ module ].dependencies ) &&
+					( baseModules.indexOf( module ) !== -1 || allReady( baseModules ) );
+			}
+
 			/**
 			 * Determine whether all dependencies are in state 'ready', which means we may
 			 * execute the module or job now.
@@ -775,9 +794,10 @@
 			 * @param {string} module Name of module that entered one of the states 'ready', 'error', or 'missing'.
 			 */
 			function handlePending( module ) {
-				var j, job, hasErrors, m, stateChange;
+				var j, job, hasErrors, m, stateChange, fromBaseModule;
 
 				if ( registry[ module ].state === 'error' || registry[ module ].state === 'missing' ) {
+					fromBaseModule = baseModules.indexOf( module ) !== -1;
 					// If the current module failed, mark all dependent modules also as failed.
 					// Iterate until steady-state to propagate the error state upwards in the
 					// dependency tree.
@@ -785,7 +805,12 @@
 						stateChange = false;
 						for ( m in registry ) {
 							if ( registry[ m ].state !== 'error' && registry[ m ].state !== 'missing' ) {
-								if ( anyFailed( registry[ m ].dependencies ) ) {
+								// Always propagate errors from base modules to regular modules (implicit dependency).
+								// Between base modules or regular modules, consider direct dependencies only.
+								if (
+									( fromBaseModule && baseModules.indexOf( m ) === -1 ) ||
+									anyFailed( registry[ m ].dependencies )
+								) {
 									registry[ m ].state = 'error';
 									stateChange = true;
 								}
@@ -824,12 +849,16 @@
 					}
 				}
 
+				// The current module became 'ready'.
 				if ( registry[ module ].state === 'ready' ) {
-					// The current module became 'ready'. Set it in the module store, and recursively execute all
-					// dependent modules that are loaded and now have all dependencies satisfied.
+					// Save it to the module store.
 					mw.loader.store.set( module, registry[ module ] );
+					// Recursively execute all dependent modules that were already loaded
+					// (waiting for execution) and no longer have unsatisfied dependencies.
 					for ( m in registry ) {
-						if ( registry[ m ].state === 'loaded' && allReady( registry[ m ].dependencies ) ) {
+						// Base modules may have dependencies amongst eachother to ensure correct
+						// execution order. Regular modules wait for all base modules.
+						if ( registry[ m ].state === 'loaded' && allWithImplicitReady( m ) ) {
 							// eslint-disable-next-line no-use-before-define
 							execute( m );
 						}
@@ -879,6 +908,16 @@
 				if ( !unresolved ) {
 					unresolved = new StringSet();
 				}
+
+				// Add base modules
+				if ( baseModules.indexOf( module ) === -1 ) {
+					baseModules.forEach( function ( baseModule ) {
+						if ( resolved.indexOf( baseModule ) === -1 ) {
+							resolved.push( baseModule );
+						}
+					} );
+				}
+
 				// Tracks down dependencies
 				deps = registry[ module ].dependencies;
 				for ( i = 0; i < deps.length; i++ ) {
@@ -1152,9 +1191,19 @@
 						if ( Array.isArray( script ) ) {
 							nestedAddScript( script, markModuleReady, 0 );
 						} else if ( typeof script === 'function' ) {
-							// Pass jQuery twice so that the signature of the closure which wraps
-							// the script can bind both '$' and 'jQuery'.
-							script( window.$, window.$, mw.loader.require, registry[ module ].module );
+							if ( window.$ ) {
+								// Pass jQuery twice so that the signature of the closure which wraps
+								// the script can bind both '$' and 'jQuery'.
+								script( window.$, window.$, mw.loader.require, registry[ module ].module );
+							} else {
+								// This is a special case for when 'jquery' itself is being loaded.
+								// - The standard jquery.js distribution does not set `window.jQuery`
+								//   in CommonJS-compatible environments (Node.js, AMD, RequireJS, etc.).
+								// - MediaWiki's 'jquery' module also bundles jquery.migrate.js, which
+								//   in a CommonJS-compatible environment, will use require('jquery'),
+								//   but that can't work when we're still inside that module.
+								script();
+							}
 							markModuleReady();
 
 						} else if ( typeof script === 'string' ) {
@@ -1806,7 +1855,7 @@
 					// The module may already have been marked as erroneous
 					if ( registry[ name ].state !== 'error' && registry[ name ].state !== 'missing' ) {
 						registry[ name ].state = 'loaded';
-						if ( allReady( registry[ name ].dependencies ) ) {
+						if ( allWithImplicitReady( name ) ) {
 							execute( name );
 						}
 					}
diff --git a/resources/src/startup/startup.js b/resources/src/startup/startup.js
index c609852a241..b2d86e21cee 100644
--- a/resources/src/startup/startup.js
+++ b/resources/src/startup/startup.js
@@ -80,7 +80,7 @@ window.isCompatible = function ( str ) {
 };
 
 ( function () {
-	var NORLQ, script;
+	var NORLQ;
 	// Handle Grade C
 	if ( !isCompatible() ) {
 		// Undo speculative Grade A <html> class. See ResourceLoaderClientHtml::getDocumentAttributes().
@@ -119,19 +119,20 @@ window.isCompatible = function ( str ) {
 		// Process callbacks for Grade A
 		// Must be after registrations and mw.config.set, which mw.loader depends on.
 		var queue = window.RLQ;
-		window.RLQ = {
-			push: function ( fn ) {
-				if ( typeof fn === 'function' ) {
-					fn();
-				} else {
-					// This callback has a requirement.
-					mw.loader.using( fn[ 0 ], fn[ 1 ] );
-				}
+		// Redefine push(), but keep type as array for storing callbacks that require modules.
+		window.RLQ = [];
+		/* global RLQ */
+		RLQ.push = function ( fn ) {
+			if ( typeof fn === 'function' ) {
+				fn();
+			} else {
+				// This callback requires a module, handled in mediawiki.base.
+				RLQ[ RLQ.length ] = fn;
 			}
 		};
 		while ( queue && queue[ 0 ] ) {
 			// Re-use our push()
-			window.RLQ.push( queue.shift() );
+			RLQ.push( queue.shift() );
 		}
 
 		// Clear and disable the Grade C queue
@@ -147,14 +148,5 @@ window.isCompatible = function ( str ) {
 	// This embeds mediawiki.js, which defines 'mw' and 'mw.loader'.
 	$CODE.defineLoader();
 
-	script = document.createElement( 'script' );
-	script.src = $VARS.baseModulesUri;
-	script.onload = function () {
-		// Clean up
-		script.onload = null;
-		script = null;
-		// Callback
-		startUp();
-	};
-	document.head.appendChild( script );
+	mw.requestIdleCallback( startUp );
 }() );
diff --git a/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js b/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
index de593d50392..6b2738b2e79 100644
--- a/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
+++ b/tests/qunit/suites/resources/mediawiki/mediawiki.loader.test.js
@@ -656,7 +656,11 @@
 			},
 			function ( e, dependencies ) {
 				assert.strictEqual( Array.isArray( dependencies ), true, 'Expected array of dependencies' );
-				assert.deepEqual( dependencies, [ 'test.module7' ], 'Error callback called with module test.module7' );
+				assert.deepEqual(
+					dependencies,
+					[ 'jquery', 'mediawiki.base', 'test.module7' ],
+					'Error callback called with module test.module7'
+				);
 			}
 		);
 		mw.loader.using(
@@ -670,7 +674,7 @@
 				dependencies.sort();
 				assert.deepEqual(
 					dependencies,
-					[ 'test.module7', 'test.module8', 'test.module9' ],
+					[ 'jquery', 'mediawiki.base', 'test.module7', 'test.module8', 'test.module9' ],
 					'Error callback called with all three modules as dependencies'
 				);
 			}