diff --git a/quic/api/QuicSocket.h b/quic/api/QuicSocket.h
index 71aed841b..ff3d933d4 100644
--- a/quic/api/QuicSocket.h
+++ b/quic/api/QuicSocket.h
@@ -101,6 +101,11 @@ class QuicSocket {
      */
     virtual void onUnidirectionalStreamsAvailable(
         uint64_t /*numStreamsAvailable*/) noexcept {}
+
+    /**
+     * Invoked when transport is detected to be app rate limited.
+     */
+    virtual void onAppRateLimited() noexcept {}
   };
 
   /**
diff --git a/quic/api/QuicTransportBase.cpp b/quic/api/QuicTransportBase.cpp
index 9772eda3d..eefd54aed 100644
--- a/quic/api/QuicTransportBase.cpp
+++ b/quic/api/QuicTransportBase.cpp
@@ -2433,6 +2433,7 @@ void QuicTransportBase::writeSocketData() {
           currentSendBufLen < conn_->udpSendPacketLen && lossBufferEmpty &&
           conn_->congestionController->getWritableBytes()) {
         conn_->congestionController->setAppLimited();
+        connCallback_->onAppRateLimited();
       }
     }
   }
diff --git a/quic/api/test/Mocks.h b/quic/api/test/Mocks.h
index 9e266a27a..aeb455423 100644
--- a/quic/api/test/Mocks.h
+++ b/quic/api/test/Mocks.h
@@ -117,6 +117,7 @@ class MockConnectionCallback : public QuicSocket::ConnectionCallback {
       ,
       onUnidirectionalStreamsAvailable,
       void(uint64_t));
+  GMOCK_METHOD0_(, noexcept, , onAppRateLimited, void());
 };
 
 class MockDeliveryCallback : public QuicSocket::DeliveryCallback {
diff --git a/quic/api/test/QuicTransportTest.cpp b/quic/api/test/QuicTransportTest.cpp
index 05ddc5b7d..383f2b909 100644
--- a/quic/api/test/QuicTransportTest.cpp
+++ b/quic/api/test/QuicTransportTest.cpp
@@ -280,6 +280,7 @@ TEST_F(QuicTransportTest, NotAppLimitedWithLoss) {
       false,
       nullptr);
   EXPECT_CALL(*rawCongestionController, setAppLimited()).Times(0);
+  EXPECT_CALL(connCallback_, onAppRateLimited()).Times(0);
   loopForWrites();
   transport_->close(folly::none);
 }
@@ -307,6 +308,7 @@ TEST_F(QuicTransportTest, NotAppLimitedWithNoWritableBytes) {
       false,
       nullptr);
   EXPECT_CALL(*rawCongestionController, setAppLimited()).Times(0);
+  EXPECT_CALL(connCallback_, onAppRateLimited()).Times(0);
   loopForWrites();
   transport_->close(folly::none);
 }
@@ -325,6 +327,7 @@ TEST_F(QuicTransportTest, NotAppLimitedWithLargeBuffer) {
   auto buf = buildRandomInputData(100 * 2000);
   transport_->writeChain(stream, buf->clone(), false, false, nullptr);
   EXPECT_CALL(*rawCongestionController, setAppLimited()).Times(0);
+  EXPECT_CALL(connCallback_, onAppRateLimited()).Times(0);
   loopForWrites();
   transport_->close(folly::none);
 }
@@ -347,6 +350,7 @@ TEST_F(QuicTransportTest, AppLimited) {
       false,
       nullptr);
   EXPECT_CALL(*rawCongestionController, setAppLimited()).Times(1);
+  EXPECT_CALL(connCallback_, onAppRateLimited()).Times(1);
   loopForWrites();
   transport_->close(folly::none);
 }