diff --git a/.ruby-version b/.ruby-version
index fa376edcab7..a4dd9dba4fb 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-ruby-2.7
+2.7.4
diff --git a/FirebasePerformance/Sources/Instrumentation/FPRObjectInstrumentor.h b/FirebasePerformance/Sources/Instrumentation/FPRObjectInstrumentor.h
index b016c070ef8..1716a56d4aa 100644
--- a/FirebasePerformance/Sources/Instrumentation/FPRObjectInstrumentor.h
+++ b/FirebasePerformance/Sources/Instrumentation/FPRObjectInstrumentor.h
@@ -33,6 +33,12 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)registerObject:(id)object;
 
+/** Registers an instance of the delegate class to be instrumented.
+ *
+ *  @param proxy The instance to instrument.
+ */
+- (void)registerProxy:(id)proxy;
+
 @end
 
 /** This class allows the instrumentation of specific objects by isa swizzling specific instances
diff --git a/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h b/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h
index a746e8e0237..dadf4d50a09 100644
--- a/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h
+++ b/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h
@@ -31,4 +31,15 @@
               forSuperclass:(Class)superclass
             varFoundHandler:(void (^)(id ivar))varFoundHandler;
 
+/** Registers a proxy object for a given class and runs the onSuccess block whenever an ivar of the
+ *  given class is discovered on the proxy object.
+ *
+ *  @param proxy The proxy object whose ivars will be iterated.
+ *  @param protocol The protocol all ivars will be compared against. See varFoundHandler.
+ *  @param varFoundHandler The block to run when an ivar conformsToProtocol:protocol.
+ */
++ (void)registerProxyObject:(id)proxy
+                forProtocol:(Protocol *)protocol
+            varFoundHandler:(void (^)(id ivar))varFoundHandler;
+
 @end
diff --git a/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.m b/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.m
index ae46231ee5a..58a98c2a549 100644
--- a/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.m
+++ b/FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.m
@@ -29,4 +29,15 @@ + (void)registerProxyObject:(id)proxy
   }
 }
 
++ (void)registerProxyObject:(id)proxy
+                forProtocol:(Protocol *)protocol
+            varFoundHandler:(void (^)(id ivar))varFoundHandler {
+  NSArray<id> *ivars = [GULSwizzler ivarObjectsForObject:proxy];
+  for (id ivar in ivars) {
+    if ([ivar conformsToProtocol:protocol]) {
+      varFoundHandler(ivar);
+    }
+  }
+}
+
 @end
diff --git a/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLConnectionDelegateInstrument.m b/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLConnectionDelegateInstrument.m
index a01fb2180a6..8123ae56b62 100644
--- a/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLConnectionDelegateInstrument.m
+++ b/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLConnectionDelegateInstrument.m
@@ -17,6 +17,7 @@
 #import "FirebasePerformance/Sources/Instrumentation/FPRClassInstrumentor.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRInstrument_Private.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRNetworkTrace.h"
+#import "FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRSelectorInstrumentor.h"
 #import "FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLConnectionDelegate.h"
 #import "FirebasePerformance/Sources/Instrumentation/Network/FPRNetworkInstrumentHelpers.h"
@@ -304,4 +305,13 @@ - (void)registerObject:(id)object {
   });
 }
 
+- (void)registerProxy:(id)proxy {
+  [FPRProxyObjectHelper registerProxyObject:proxy
+                                forProtocol:@protocol(NSURLSessionDelegate)
+                            varFoundHandler:^(id ivar) {
+                              [self registerClass:[ivar class]];
+                              [self registerObject:ivar];
+                            }];
+}
+
 @end
diff --git a/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLSessionDelegateInstrument.m b/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLSessionDelegateInstrument.m
index c636d3e2ba7..6541caa2e27 100644
--- a/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLSessionDelegateInstrument.m
+++ b/FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLSessionDelegateInstrument.m
@@ -18,6 +18,7 @@
 #import "FirebasePerformance/Sources/Instrumentation/FPRClassInstrumentor.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRInstrument_Private.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRNetworkTrace.h"
+#import "FirebasePerformance/Sources/Instrumentation/FPRProxyObjectHelper.h"
 #import "FirebasePerformance/Sources/Instrumentation/FPRSelectorInstrumentor.h"
 #import "FirebasePerformance/Sources/Instrumentation/Network/Delegates/FPRNSURLSessionDelegate.h"
 #import "FirebasePerformance/Sources/Instrumentation/Network/FPRNetworkInstrumentHelpers.h"
@@ -263,4 +264,13 @@ - (void)registerObject:(id)object {
   });
 }
 
+- (void)registerProxy:(id)proxy {
+  [FPRProxyObjectHelper registerProxyObject:proxy
+                                forProtocol:@protocol(NSURLSessionDelegate)
+                            varFoundHandler:^(id ivar) {
+                              [self registerClass:[ivar class]];
+                              [self registerObject:ivar];
+                            }];
+}
+
 @end
diff --git a/FirebasePerformance/Sources/Instrumentation/Network/FPRNSURLSessionInstrument.m b/FirebasePerformance/Sources/Instrumentation/Network/FPRNSURLSessionInstrument.m
index 57394071199..610ba0fcc8c 100644
--- a/FirebasePerformance/Sources/Instrumentation/Network/FPRNSURLSessionInstrument.m
+++ b/FirebasePerformance/Sources/Instrumentation/Network/FPRNSURLSessionInstrument.m
@@ -157,9 +157,12 @@ void InstrumentSessionWithConfigurationDelegateDelegateQueue(
           ThrowExceptionBecauseInstrumentHasBeenDeallocated(selector, instrumentedClass);
         }
         if (delegate) {
-          [delegateInstrument registerClass:[delegate class]];
-          [delegateInstrument registerObject:delegate];
-
+          if ([delegate isProxy]) {
+            [delegateInstrument registerProxy:delegate];
+          } else {
+            [delegateInstrument registerClass:[delegate class]];
+            [delegateInstrument registerObject:delegate];
+          }
         } else {
           delegate = [[FPRNSURLSessionDelegate alloc] init];
         }
diff --git a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTest.m b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTest.m
index ffffbe17c17..92d754e8385 100644
--- a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTest.m
+++ b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTest.m
@@ -62,6 +62,39 @@ - (void)forwardInvocation:(NSInvocation *)invocation {
 
 @end
 
+@interface FPRNSURLSessionDelegateProxy : NSProxy {
+  // The wrapped delegate object.
+  id _delegate;
+}
+
+/** @return an instance of the delegate proxy. */
+- (instancetype)initWithDelegate:(id)delegate;
+
+@end
+
+@implementation FPRNSURLSessionDelegateProxy
+
+- (instancetype)initWithDelegate:(id)delegate {
+  if (self) {
+    _delegate = delegate;
+  }
+  return self;
+}
+
+- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector {
+  return [_delegate methodSignatureForSelector:selector];
+}
+
+- (BOOL)respondsToSelector:(SEL)aSelector {
+  return [_delegate respondsToSelector:aSelector];
+}
+
+- (void)forwardInvocation:(NSInvocation *)invocation {
+  [invocation invokeWithTarget:_delegate];
+}
+
+@end
+
 @interface FPRNSURLSessionInstrumentTest : FPRTestCase
 
 /** Test server to create connections to. */
@@ -482,6 +515,33 @@ - (void)testDelegateURLSessionDownloadTaskDidFinishDownloadingToURL {
   [instrument deregisterInstrumentors];
 }
 
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testDelegateURLSessionDownloadDidReceiveResponseCompletionHandler {
+  FPRNSURLSessionInstrument *instrument;
+  NSURLSessionDataTask *dataTask;
+  @autoreleasepool {
+    instrument = [[FPRNSURLSessionInstrument alloc] init];
+    [instrument registerInstrumentors];
+    FPRNSURLSessionCompleteTestDelegate *delegate =
+        [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+    NSURLSessionConfiguration *configuration =
+        [NSURLSessionConfiguration defaultSessionConfiguration];
+    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                          delegate:delegate
+                                                     delegateQueue:nil];
+    NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testBigDownload"];
+    dataTask = [session dataTaskWithURL:URL];
+    [dataTask resume];
+    XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                         GCDWebServerResponse *_Nonnull response) {
+      XCTAssertTrue(delegate.URLSessionDataTaskDidReceiveResponseCompletionHandlerCalled);
+      XCTAssertNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    }];
+  }
+  [instrument deregisterInstrumentors];
+}
+
 /** Tests that the called delegate selector is wrapped and calls through. */
 - (void)testDelegateURLSessionDownloadTaskDidResumeAtOffsetExpectedTotalBytes {
   FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
@@ -548,6 +608,277 @@ - (void)testDelegateUnimplementedURLSessionTaskDidCompleteWithError {
   [instrument deregisterInstrumentors];
 }
 
+#pragma mark - Testing proxy delegate method wrapping
+
+/** Tests that the delegate class is instrumented once when its wrapped with NSProxy. */
+- (void)testProxyDelegateSwizzlesDelegateOnce {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  [NSURLSession sessionWithConfiguration:configuration delegate:proxyDelegate delegateQueue:nil];
+  [NSURLSession sessionWithConfiguration:configuration delegate:proxyDelegate delegateQueue:nil];
+  XCTAssertEqual(instrument.delegateInstrument.classInstrumentors.count, 1);
+  XCTAssertEqual(instrument.delegateInstrument.instrumentedClasses.count, 1);
+  XCTAssertTrue(
+      [instrument.delegateInstrument.instrumentedClasses containsObject:[delegate class]]);
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionTaskDidCompleteWithError {
+  [self.testServer stop];
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  // This request needs to fail.
+  NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://nonurl"]];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURLSessionTask *task;
+  @autoreleasepool {
+    task = [session dataTaskWithRequest:request];
+    [task resume];
+    XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:task]);
+    [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:5.0]];
+  }
+  XCTAssertNil([FPRNetworkTrace networkTraceFromObject:task]);
+  XCTAssertTrue(delegate.URLSessionTaskDidCompleteWithErrorCalled);
+  [instrument deregisterInstrumentors];
+  [self.testServer start];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionTaskDidSendBodyDataTotalBytesSentTotalBytesExpectedToSend {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testUpload"];
+  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:URL];
+  request.HTTPMethod = @"POST";
+
+  NSBundle *bundle = [FPRTestUtils getBundle];
+  NSURL *fileURL = [bundle URLForResource:@"smallDownloadFile" withExtension:@""];
+  NSURLSessionUploadTask *uploadTask = [session uploadTaskWithRequest:request fromFile:fileURL];
+  [uploadTask resume];
+
+  XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:uploadTask]);
+  FPRNetworkTrace *networkTrace = [FPRNetworkTrace networkTraceFromObject:uploadTask];
+
+  [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                       GCDWebServerResponse *_Nonnull response) {
+    XCTAssertTrue(delegate.URLSessionTaskDidSendBodyDataTotalBytesSentTotalBytesExpectedCalled);
+    XCTAssert(networkTrace.requestSize > 0);
+    XCTAssert(
+        [networkTrace
+            timeIntervalBetweenCheckpointState:FPRNetworkTraceCheckpointStateInitiated
+                                      andState:FPRNetworkTraceCheckpointStateRequestCompleted] > 0);
+    XCTAssertNil([FPRNetworkTrace networkTraceFromObject:uploadTask]);
+  }];
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionTaskWillPerformHTTPRedirectionNewRequestCompletionHandler {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testRedirect"];
+  NSURLRequest *request = [NSURLRequest requestWithURL:URL];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURLSessionTask *task = [session dataTaskWithRequest:request];
+  [task resume];
+  XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:task]);
+  [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                       GCDWebServerResponse *_Nonnull response) {
+    XCTAssertTrue(
+        delegate.URLSessionTaskWillPerformHTTPRedirectionNewRequestCompletionHandlerCalled);
+  }];
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionDataTaskDidReceiveData {
+  FPRNSURLSessionInstrument *instrument;
+  NSURLSessionDataTask *dataTask;
+  @autoreleasepool {
+    instrument = [[FPRNSURLSessionInstrument alloc] init];
+    [instrument registerInstrumentors];
+    FPRNSURLSessionCompleteTestDelegate *delegate =
+        [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+    FPRNSURLSessionDelegateProxy *proxyDelegate =
+        [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+    NSURLSessionConfiguration *configuration =
+        [NSURLSessionConfiguration defaultSessionConfiguration];
+    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                          delegate:proxyDelegate
+                                                     delegateQueue:nil];
+    NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testBigDownload"];
+    dataTask = [session dataTaskWithURL:URL];
+    [dataTask resume];
+    XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                         GCDWebServerResponse *_Nonnull response) {
+      XCTAssertTrue(delegate.URLSessionDataTaskDidReceiveDataCalled);
+      XCTAssertNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    }];
+  }
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionDownloadTaskDidFinishDownloadingToURL {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testDownload"];
+  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:URL];
+  [downloadTask resume];
+  XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                       GCDWebServerResponse *_Nonnull response) {
+    XCTAssertTrue(delegate.URLSessionDownloadTaskDidFinishDownloadingToURLCalled);
+    XCTAssertNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  }];
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionDownloadDidReceiveResponseCompletionHandler {
+  FPRNSURLSessionInstrument *instrument;
+  NSURLSessionDataTask *dataTask;
+  @autoreleasepool {
+    instrument = [[FPRNSURLSessionInstrument alloc] init];
+    [instrument registerInstrumentors];
+    FPRNSURLSessionCompleteTestDelegate *delegate =
+        [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+    FPRNSURLSessionDelegateProxy *proxyDelegate =
+        [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+    NSURLSessionConfiguration *configuration =
+        [NSURLSessionConfiguration defaultSessionConfiguration];
+    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                          delegate:proxyDelegate
+                                                     delegateQueue:nil];
+    NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testBigDownload"];
+    dataTask = [session dataTaskWithURL:URL];
+    [dataTask resume];
+    XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                         GCDWebServerResponse *_Nonnull response) {
+      XCTAssertTrue(delegate.URLSessionDataTaskDidReceiveResponseCompletionHandlerCalled);
+      XCTAssertTrue(delegate.URLSessionTaskDidCompleteWithErrorCalled);
+      XCTAssertNil([FPRNetworkTrace networkTraceFromObject:dataTask]);
+    }];
+  }
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)testProxyDelegateURLSessionDownloadTaskDidResumeAtOffsetExpectedTotalBytes {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionTestDownloadDelegate *delegate =
+      [[FPRNSURLSessionTestDownloadDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testBigDownload"];
+  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:URL];
+  [downloadTask resume];
+  [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:5.0]];
+  XCTAssertNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  XCTAssertTrue(delegate.URLSessionDownloadTaskDidResumeAtOffsetExpectedTotalBytesCalled);
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that the called delegate selector is wrapped and calls through. */
+- (void)
+    testProxyDelegateURLSessionDownloadTaskDidWriteDataTotalBytesWrittenTotalBytesExpectedToWrite {
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  FPRNSURLSessionCompleteTestDelegate *delegate =
+      [[FPRNSURLSessionCompleteTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  NSURL *URL = [self.testServer.serverURL URLByAppendingPathComponent:@"testBigDownload"];
+  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:URL];
+  [downloadTask resume];
+  XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                       GCDWebServerResponse *_Nonnull response) {
+    XCTAssertTrue(delegate.URLSessionDownloadTaskDidWriteDataTotalBytesWrittenTotalBytesCalled);
+    [[NSRunLoop currentRunLoop] runUntilDate:[NSDate dateWithTimeIntervalSinceNow:1.0]];
+    XCTAssertNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  }];
+  [instrument deregisterInstrumentors];
+}
+
+/** Tests that even if a delegate doesn't implement a method, we add it to the delegate class. */
+- (void)testProxyDelegateUnimplementedURLSessionTaskDidCompleteWithError {
+  FPRNSURLSessionTestDelegate *delegate = [[FPRNSURLSessionTestDelegate alloc] init];
+  FPRNSURLSessionDelegateProxy *proxyDelegate =
+      [[FPRNSURLSessionDelegateProxy alloc] initWithDelegate:delegate];
+  FPRNSURLSessionInstrument *instrument = [[FPRNSURLSessionInstrument alloc] init];
+  [instrument registerInstrumentors];
+  NSURLSessionConfiguration *configuration =
+      [NSURLSessionConfiguration defaultSessionConfiguration];
+  XCTAssertFalse([delegate respondsToSelector:@selector(URLSession:task:didCompleteWithError:)]);
+  NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration
+                                                        delegate:proxyDelegate
+                                                   delegateQueue:nil];
+  XCTAssertTrue([delegate respondsToSelector:@selector(URLSession:task:didCompleteWithError:)]);
+  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithURL:self.testServer.serverURL];
+  [downloadTask resume];
+  XCTAssertNotNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  [self waitAndRunBlockAfterResponse:^(id self, GCDWebServerRequest *_Nonnull request,
+                                       GCDWebServerResponse *_Nonnull response) {
+    XCTAssertNil([FPRNetworkTrace networkTraceFromObject:downloadTask]);
+  }];
+  [instrument deregisterInstrumentors];
+}
+
 #pragma mark - Testing instance method wrapping
 
 /** Tests that dataTaskWithRequest: returns a non-nil object. */
diff --git a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.h b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.h
index 722f508fa84..1fe8a746943 100644
--- a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.h
+++ b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.h
@@ -52,6 +52,12 @@ NS_ASSUME_NONNULL_BEGIN
 /** Set to YES when URLSession:dataTask:didReceiveData: is called, used for testing. */
 @property(nonatomic) BOOL URLSessionDataTaskDidReceiveDataCalled;
 
+/** Set to YES when
+ * URLSession:dataTask:didReceiveResponse:completionHandler: is called, used
+ * for testing.
+ */
+@property(nonatomic) BOOL URLSessionDataTaskDidReceiveResponseCompletionHandlerCalled;
+
 /** Set to YES when URLSession:downloadTask:didFinishDownloadingToURL: is called, used for testing.
  */
 @property(nonatomic) BOOL URLSessionDownloadTaskDidFinishDownloadingToURLCalled;
diff --git a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.m b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.m
index 28525bd4967..9d84a70aa43 100644
--- a/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.m
+++ b/FirebasePerformance/Tests/Unit/Instruments/FPRNSURLSessionInstrumentTestDelegates.m
@@ -72,6 +72,14 @@ - (void)URLSession:(NSURLSession *)session
   self.URLSessionDataTaskDidReceiveDataCalled = YES;
 }
 
+- (void)URLSession:(NSURLSession *)session
+              dataTask:(NSURLSessionDataTask *)dataTask
+    didReceiveResponse:(NSURLResponse *)response
+     completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {
+  self.URLSessionDataTaskDidReceiveResponseCompletionHandlerCalled = YES;
+  completionHandler(NSURLSessionResponseAllow);
+}
+
 #pragma mark - NSURLSessionDownloadDelegate methods
 
 - (void)URLSession:(NSURLSession *)session