diff --git a/React/Base/RCTJavaScriptLoader.m b/React/Base/RCTJavaScriptLoader.m
index e632505a4..dd8fab461 100755
--- a/React/Base/RCTJavaScriptLoader.m
+++ b/React/Base/RCTJavaScriptLoader.m
@@ -10,15 +10,47 @@
 #import "RCTJavaScriptLoader.h"
 
 #import "RCTBridge.h"
-#import "RCTConvert.h"
+#import "RCTInvalidating.h"
+#import "RCTLog.h"
+#import "RCTRedBox.h"
 #import "RCTSourceCode.h"
 #import "RCTUtils.h"
 
+#define NO_REMOTE_MODULE @"Could not fetch module bundle %@. Ensure node server is running.\n\nIf it timed out, try reloading."
+#define NO_LOCAL_BUNDLE @"Could not load local bundle %@. Ensure file exists."
+
+#define CACHE_DIR @"RCTJSBundleCache"
+
+#pragma mark - Application Engine
+
+/**
+ * TODO:
+ * - Add window resize rotation events matching the DOM API.
+ * - Device pixel ration hooks.
+ * - Source maps.
+ */
 @implementation RCTJavaScriptLoader
 {
   __weak RCTBridge *_bridge;
 }
 
+/**
+ * `CADisplayLink` code copied from Ejecta but we've placed the JavaScriptCore
+ * engine in its own dedicated thread.
+ *
+ * TODO: Try adding to the `RCTJavaScriptExecutor`'s thread runloop. Removes one
+ * additional GCD dispatch per frame and likely makes it so that other UIThread
+ * operations don't delay the dispatch (so we can begin working in JS much
+ * faster.) Event handling must still be sent via a GCD dispatch, of course.
+ *
+ * We must add the display link to two runloops in order to get setTimeouts to
+ * fire during scrolling. (`NSDefaultRunLoopMode` and `UITrackingRunLoopMode`)
+ * TODO: We can invent a `requestAnimationFrame` and
+ * `requestAvailableAnimationFrame` to control if callbacks can be fired during
+ * an animation.
+ * http://stackoverflow.com/questions/12622800/why-does-uiscrollview-pause-my-cadisplaylink
+ *
+ */
 - (instancetype)initWithBridge:(RCTBridge *)bridge
 {
   if ((self = [super init])) {
@@ -29,87 +61,92 @@
 
 - (void)loadBundleAtURL:(NSURL *)scriptURL onComplete:(void (^)(NSError *))onComplete
 {
-  NSURL *originalURL = scriptURL;
-  if (!scriptURL.scheme || [scriptURL isFileURL]) {
-    scriptURL = [RCTConvert NSURL:scriptURL.path];
-  }
-
   if (scriptURL == nil) {
     NSError *error = [NSError errorWithDomain:@"JavaScriptLoader" code:1 userInfo:@{
-      NSLocalizedDescriptionKey: originalURL ? [NSString stringWithFormat:@"Script URL '%@' could not be found.", originalURL] : @"No script URL provided."
+      NSLocalizedDescriptionKey: @"No script URL provided"
     }];
     onComplete(error);
     return;
   }
 
+  if ([scriptURL isFileURL]) {
+    NSString *bundlePath = [[NSBundle bundleForClass:[self class]] resourcePath];
+    NSString *localPath = [scriptURL.absoluteString substringFromIndex:@"file://".length];
+
+    if (![localPath hasPrefix:bundlePath]) {
+      NSString *absolutePath = [NSString stringWithFormat:@"%@/%@", bundlePath, localPath];
+      scriptURL = [NSURL fileURLWithPath:absolutePath];
+    }
+  }
+
   NSURLSessionDataTask *task = [[NSURLSession sharedSession] dataTaskWithURL:scriptURL completionHandler:
                                 ^(NSData *data, NSURLResponse *response, NSError *error) {
 
-    // Handle general request errors
-    if (error) {
-      if ([[error domain] isEqualToString:NSURLErrorDomain]) {
-        NSString *desc = [@"Could not connect to development server. Ensure node server is running and available on the same network - run 'npm start' from react-native root\n\nURL: " stringByAppendingString:[scriptURL absoluteString]];
-        NSDictionary *userInfo = @{
-          NSLocalizedDescriptionKey: desc,
-          NSLocalizedFailureReasonErrorKey: [error localizedDescription],
-          NSUnderlyingErrorKey: error,
-        };
-        error = [NSError errorWithDomain:@"JSServer"
-                                    code:error.code
-                                userInfo:userInfo];
-      }
-      onComplete(error);
-      return;
-    }
+                                  // Handle general request errors
+                                  if (error) {
+                                    if ([[error domain] isEqualToString:NSURLErrorDomain]) {
+                                      NSString *desc = [@"Could not connect to development server. Ensure node server is running and available on the same network - run 'npm start' from react-native root\n\nURL: " stringByAppendingString:[scriptURL absoluteString]];
+                                      NSDictionary *userInfo = @{
+                                                                 NSLocalizedDescriptionKey: desc,
+                                                                 NSLocalizedFailureReasonErrorKey: [error localizedDescription],
+                                                                 NSUnderlyingErrorKey: error,
+                                                                 };
+                                      error = [NSError errorWithDomain:@"JSServer"
+                                                                  code:error.code
+                                                              userInfo:userInfo];
+                                    }
+                                    onComplete(error);
+                                    return;
+                                  }
 
-    // Parse response as text
-    NSStringEncoding encoding = NSUTF8StringEncoding;
-    if (response.textEncodingName != nil) {
-      CFStringEncoding cfEncoding = CFStringConvertIANACharSetNameToEncoding((CFStringRef)response.textEncodingName);
-      if (cfEncoding != kCFStringEncodingInvalidId) {
-        encoding = CFStringConvertEncodingToNSStringEncoding(cfEncoding);
-      }
-    }
-    NSString *rawText = [[NSString alloc] initWithData:data encoding:encoding];
+                                  // Parse response as text
+                                  NSStringEncoding encoding = NSUTF8StringEncoding;
+                                  if (response.textEncodingName != nil) {
+                                    CFStringEncoding cfEncoding = CFStringConvertIANACharSetNameToEncoding((CFStringRef)response.textEncodingName);
+                                    if (cfEncoding != kCFStringEncodingInvalidId) {
+                                      encoding = CFStringConvertEncodingToNSStringEncoding(cfEncoding);
+                                    }
+                                  }
+                                  NSString *rawText = [[NSString alloc] initWithData:data encoding:encoding];
 
-    // Handle HTTP errors
-    if ([response isKindOfClass:[NSHTTPURLResponse class]] && [(NSHTTPURLResponse *)response statusCode] != 200) {
-      NSDictionary *userInfo;
-      NSDictionary *errorDetails = RCTJSONParse(rawText, nil);
-      if ([errorDetails isKindOfClass:[NSDictionary class]] &&
-          [errorDetails[@"errors"] isKindOfClass:[NSArray class]]) {
-        NSMutableArray *fakeStack = [[NSMutableArray alloc] init];
-        for (NSDictionary *err in errorDetails[@"errors"]) {
-          [fakeStack addObject: @{
-            @"methodName": err[@"description"] ?: @"",
-            @"file": err[@"filename"] ?: @"",
-            @"lineNumber": err[@"lineNumber"] ?: @0
-          }];
-        }
-        userInfo = @{
-          NSLocalizedDescriptionKey: errorDetails[@"message"] ?: @"No message provided",
-          @"stack": fakeStack,
-        };
-      } else {
-        userInfo = @{NSLocalizedDescriptionKey: rawText};
-      }
-      error = [NSError errorWithDomain:@"JSServer"
-                                  code:[(NSHTTPURLResponse *)response statusCode]
-                              userInfo:userInfo];
+                                  // Handle HTTP errors
+                                  if ([response isKindOfClass:[NSHTTPURLResponse class]] && [(NSHTTPURLResponse *)response statusCode] != 200) {
+                                    NSDictionary *userInfo;
+                                    NSDictionary *errorDetails = RCTJSONParse(rawText, nil);
+                                    if ([errorDetails isKindOfClass:[NSDictionary class]] &&
+                                        [errorDetails[@"errors"] isKindOfClass:[NSArray class]]) {
+                                      NSMutableArray *fakeStack = [[NSMutableArray alloc] init];
+                                      for (NSDictionary *err in errorDetails[@"errors"]) {
+                                        [fakeStack addObject: @{
+                                          @"methodName": err[@"description"] ?: @"",
+                                          @"file": err[@"filename"] ?: @"",
+                                          @"lineNumber": err[@"lineNumber"] ?: @0
+                                        }];
+                                      }
+                                      userInfo = @{
+                                        NSLocalizedDescriptionKey: errorDetails[@"message"] ?: @"No message provided",
+                                        @"stack": fakeStack,
+                                      };
+                                    } else {
+                                      userInfo = @{NSLocalizedDescriptionKey: rawText};
+                                    }
+                                    error = [NSError errorWithDomain:@"JSServer"
+                                                                code:[(NSHTTPURLResponse *)response statusCode]
+                                                            userInfo:userInfo];
 
-      onComplete(error);
-      return;
-    }
-    RCTSourceCode *sourceCodeModule = _bridge.modules[RCTBridgeModuleNameForClass([RCTSourceCode class])];
-    sourceCodeModule.scriptURL = scriptURL;
-    sourceCodeModule.scriptText = rawText;
+                                    onComplete(error);
+                                    return;
+                                  }
+                                  RCTSourceCode *sourceCodeModule = _bridge.modules[RCTBridgeModuleNameForClass([RCTSourceCode class])];
+                                  sourceCodeModule.scriptURL = scriptURL;
+                                  sourceCodeModule.scriptText = rawText;
 
-    [_bridge enqueueApplicationScript:rawText url:scriptURL onComplete:^(NSError *scriptError) {
-      dispatch_async(dispatch_get_main_queue(), ^{
-        onComplete(scriptError);
-      });
-    }];
-  }];
+                                  [_bridge enqueueApplicationScript:rawText url:scriptURL onComplete:^(NSError *scriptError) {
+                                    dispatch_async(dispatch_get_main_queue(), ^{
+                                      onComplete(scriptError);
+                                    });
+                                  }];
+                                }];
 
   [task resume];
 }