diff --git a/package.json b/package.json
index 90ee3304af4fa..97e1343213eb0 100644
--- a/package.json
+++ b/package.json
@@ -36,7 +36,6 @@
     "@babel/preset-flow": "^7.10.4",
     "@babel/preset-react": "^7.10.4",
     "@babel/traverse": "^7.11.0",
-    "abort-controller": "^3.0.0",
     "art": "0.10.1",
     "babel-plugin-syntax-trailing-function-commas": "^6.5.0",
     "chalk": "^3.0.0",
diff --git a/packages/jest-mock-scheduler/README.md b/packages/jest-mock-scheduler/README.md
deleted file mode 100644
index 387f015246617..0000000000000
--- a/packages/jest-mock-scheduler/README.md
+++ /dev/null
@@ -1,5 +0,0 @@
-# `jest-mock-scheduler`
-
-Jest matchers and utilities for testing the `scheduler` package.
-
-This package is experimental. APIs may change between releases.
\ No newline at end of file
diff --git a/packages/jest-mock-scheduler/npm/index.js b/packages/jest-mock-scheduler/npm/index.js
deleted file mode 100644
index 9a1d6ca4d1495..0000000000000
--- a/packages/jest-mock-scheduler/npm/index.js
+++ /dev/null
@@ -1,3 +0,0 @@
-'use strict';
-
-module.exports = require('scheduler/unstable_mock');
diff --git a/packages/jest-mock-scheduler/package.json b/packages/jest-mock-scheduler/package.json
deleted file mode 100644
index 16761b19d3750..0000000000000
--- a/packages/jest-mock-scheduler/package.json
+++ /dev/null
@@ -1,31 +0,0 @@
-{
-  "name": "jest-mock-scheduler",
-  "private": true,
-  "version": "0.1.0",
-  "description": "Jest matchers and utilities for testing the scheduler package.",
-  "main": "index.js",
-  "repository": {
-    "type" : "git",
-    "url" : "https://github.com/facebook/react.git",
-    "directory": "packages/jest-mock-scheduler"
-  },
-  "keywords": [
-    "jest",
-    "scheduler"
-  ],
-  "license": "MIT",
-  "bugs": {
-    "url": "https://github.com/facebook/react/issues"
-  },
-  "homepage": "https://reactjs.org/",
-  "peerDependencies": {
-    "jest": "^23.0.1 || ^24.0.0 || ^25.1.0",
-    "scheduler": "^0.20.0"
-  },
-  "files": [
-    "LICENSE",
-    "README.md",
-    "index.js",
-    "cjs/"
-  ]
-}
diff --git a/packages/react-client/src/ReactFlightClient.js b/packages/react-client/src/ReactFlightClient.js
index 86455c3dfe6ad..2dd135ad656a9 100644
--- a/packages/react-client/src/ReactFlightClient.js
+++ b/packages/react-client/src/ReactFlightClient.js
@@ -201,14 +201,6 @@ function createErrorChunk<T>(
   return new Chunk(ERRORED, null, error, response);
 }
 
-function createInitializedChunk<T>(
-  response: Response,
-  value: T,
-): InitializedChunk<T> {
-  // $FlowFixMe Flow doesn't support functions as constructors
-  return new Chunk(INITIALIZED, value, null, response);
-}
-
 function wakeChunk<T>(listeners: Array<(T) => mixed>, value: T): void {
   for (let i = 0; i < listeners.length; i++) {
     const listener = listeners[i];
@@ -483,14 +475,32 @@ export function parseModelString(
   key: string,
   value: string,
 ): any {
-  switch (value[0]) {
-    case '$': {
-      if (value === '$') {
-        return REACT_ELEMENT_TYPE;
-      } else if (value[1] === '$' || value[1] === '@') {
+  if (value[0] === '$') {
+    if (value === '$') {
+      // A very common symbol.
+      return REACT_ELEMENT_TYPE;
+    }
+    switch (value[1]) {
+      case '$': {
         // This was an escaped string value.
         return value.substring(1);
-      } else {
+      }
+      case 'L': {
+        // Lazy node
+        const id = parseInt(value.substring(2), 16);
+        const chunk = getChunk(response, id);
+        // We create a React.lazy wrapper around any lazy values.
+        // When passed into React, we'll know how to suspend on this.
+        return createLazyChunkWrapper(chunk);
+      }
+      case 'S': {
+        return Symbol.for(value.substring(2));
+      }
+      case 'P': {
+        return getOrCreateServerContext(value.substring(2)).Provider;
+      }
+      default: {
+        // We assume that anything else is a reference ID.
         const id = parseInt(value.substring(1), 16);
         const chunk = getChunk(response, id);
         switch (chunk.status) {
@@ -518,13 +528,6 @@ export function parseModelString(
         }
       }
     }
-    case '@': {
-      const id = parseInt(value.substring(1), 16);
-      const chunk = getChunk(response, id);
-      // We create a React.lazy wrapper around any lazy values.
-      // When passed into React, we'll know how to suspend on this.
-      return createLazyChunkWrapper(chunk);
-    }
   }
   return value;
 }
@@ -566,21 +569,6 @@ export function resolveModel(
   }
 }
 
-export function resolveProvider(
-  response: Response,
-  id: number,
-  contextName: string,
-): void {
-  const chunks = response._chunks;
-  chunks.set(
-    id,
-    createInitializedChunk(
-      response,
-      getOrCreateServerContext(contextName).Provider,
-    ),
-  );
-}
-
 export function resolveModule(
   response: Response,
   id: number,
@@ -626,17 +614,6 @@ export function resolveModule(
   }
 }
 
-export function resolveSymbol(
-  response: Response,
-  id: number,
-  name: string,
-): void {
-  const chunks = response._chunks;
-  // We assume that we'll always emit the symbol before anything references it
-  // to save a few bytes.
-  chunks.set(id, createInitializedChunk(response, Symbol.for(name)));
-}
-
 type ErrorWithDigest = Error & {digest?: string};
 export function resolveErrorProd(
   response: Response,
diff --git a/packages/react-client/src/ReactFlightClientStream.js b/packages/react-client/src/ReactFlightClientStream.js
index bcdcda4375a8f..57887e48d4550 100644
--- a/packages/react-client/src/ReactFlightClientStream.js
+++ b/packages/react-client/src/ReactFlightClientStream.js
@@ -14,8 +14,6 @@ import type {BundlerConfig} from './ReactFlightClientHostConfig';
 import {
   resolveModule,
   resolveModel,
-  resolveProvider,
-  resolveSymbol,
   resolveErrorProd,
   resolveErrorDev,
   createResponse as createResponseBase,
@@ -36,33 +34,20 @@ function processFullRow(response: Response, row: string): void {
   if (row === '') {
     return;
   }
-  const tag = row[0];
+  const colon = row.indexOf(':', 0);
+  const id = parseInt(row.substring(0, colon), 16);
+  const tag = row[colon + 1];
   // When tags that are not text are added, check them here before
   // parsing the row as text.
   // switch (tag) {
   // }
-  const colon = row.indexOf(':', 1);
-  const id = parseInt(row.substring(1, colon), 16);
-  const text = row.substring(colon + 1);
   switch (tag) {
-    case 'J': {
-      resolveModel(response, id, text);
-      return;
-    }
-    case 'M': {
-      resolveModule(response, id, text);
-      return;
-    }
-    case 'P': {
-      resolveProvider(response, id, text);
-      return;
-    }
-    case 'S': {
-      resolveSymbol(response, id, JSON.parse(text));
+    case 'I': {
+      resolveModule(response, id, row.substring(colon + 2));
       return;
     }
     case 'E': {
-      const errorInfo = JSON.parse(text);
+      const errorInfo = JSON.parse(row.substring(colon + 2));
       if (__DEV__) {
         resolveErrorDev(
           response,
@@ -77,9 +62,9 @@ function processFullRow(response: Response, row: string): void {
       return;
     }
     default: {
-      throw new Error(
-        "Error parsing the data. It's probably an error code or network corruption.",
-      );
+      // We assume anything else is JSON.
+      resolveModel(response, id, row.substring(colon + 1));
+      return;
     }
   }
 }
diff --git a/packages/react-server-dom-relay/src/ReactFlightDOMRelayClient.js b/packages/react-server-dom-relay/src/ReactFlightDOMRelayClient.js
index 5e344c1398c53..5bf775bfb5f26 100644
--- a/packages/react-server-dom-relay/src/ReactFlightDOMRelayClient.js
+++ b/packages/react-server-dom-relay/src/ReactFlightDOMRelayClient.js
@@ -15,7 +15,6 @@ import {
   createResponse,
   resolveModel,
   resolveModule,
-  resolveSymbol,
   resolveErrorDev,
   resolveErrorProd,
   close,
@@ -25,15 +24,12 @@ import {
 export {createResponse, close, getRoot};
 
 export function resolveRow(response: Response, chunk: RowEncoding): void {
-  if (chunk[0] === 'J') {
+  if (chunk[0] === 'O') {
     // $FlowFixMe unable to refine on array indices
     resolveModel(response, chunk[1], chunk[2]);
-  } else if (chunk[0] === 'M') {
+  } else if (chunk[0] === 'I') {
     // $FlowFixMe unable to refine on array indices
     resolveModule(response, chunk[1], chunk[2]);
-  } else if (chunk[0] === 'S') {
-    // $FlowFixMe: Flow doesn't support disjoint unions on tuples.
-    resolveSymbol(response, chunk[1], chunk[2]);
   } else {
     if (__DEV__) {
       resolveErrorDev(
diff --git a/packages/react-server-dom-relay/src/ReactFlightDOMRelayProtocol.js b/packages/react-server-dom-relay/src/ReactFlightDOMRelayProtocol.js
index 3b3425abeca06..f770432dce1e2 100644
--- a/packages/react-server-dom-relay/src/ReactFlightDOMRelayProtocol.js
+++ b/packages/react-server-dom-relay/src/ReactFlightDOMRelayProtocol.js
@@ -18,8 +18,8 @@ export type JSONValue =
   | $ReadOnlyArray<JSONValue>;
 
 export type RowEncoding =
-  | ['J', number, JSONValue]
-  | ['M', number, ModuleMetaData]
+  | ['O', number, JSONValue]
+  | ['I', number, ModuleMetaData]
   | ['P', number, string]
   | ['S', number, string]
   | [
diff --git a/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js b/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
index 7efc6c911e44c..bf6572110d4d1 100644
--- a/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
+++ b/packages/react-server-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
@@ -151,7 +151,7 @@ export function processModelChunk(
 ): Chunk {
   // $FlowFixMe no good way to define an empty exact object
   const json = convertModelToJSON(request, {}, '', model);
-  return ['J', id, json];
+  return ['O', id, json];
 }
 
 export function processReferenceChunk(
@@ -159,7 +159,7 @@ export function processReferenceChunk(
   id: number,
   reference: string,
 ): Chunk {
-  return ['J', id, reference];
+  return ['O', id, reference];
 }
 
 export function processModuleChunk(
@@ -168,23 +168,7 @@ export function processModuleChunk(
   moduleMetaData: ModuleMetaData,
 ): Chunk {
   // The moduleMetaData is already a JSON serializable value.
-  return ['M', id, moduleMetaData];
-}
-
-export function processProviderChunk(
-  request: Request,
-  id: number,
-  contextName: string,
-): Chunk {
-  return ['P', id, contextName];
-}
-
-export function processSymbolChunk(
-  request: Request,
-  id: number,
-  name: string,
-): Chunk {
-  return ['S', id, name];
+  return ['I', id, moduleMetaData];
 }
 
 export function scheduleWork(callback: () => void) {
diff --git a/packages/react-server-native-relay/src/ReactFlightNativeRelayClient.js b/packages/react-server-native-relay/src/ReactFlightNativeRelayClient.js
index 94f287971441f..b9a398cc9328b 100644
--- a/packages/react-server-native-relay/src/ReactFlightNativeRelayClient.js
+++ b/packages/react-server-native-relay/src/ReactFlightNativeRelayClient.js
@@ -15,7 +15,6 @@ import {
   createResponse,
   resolveModel,
   resolveModule,
-  resolveSymbol,
   resolveErrorDev,
   resolveErrorProd,
   close,
@@ -25,15 +24,12 @@ import {
 export {createResponse, close, getRoot};
 
 export function resolveRow(response: Response, chunk: RowEncoding): void {
-  if (chunk[0] === 'J') {
+  if (chunk[0] === 'O') {
     // $FlowFixMe `Chunk` doesn't flow into `JSONValue` because of the `E` row type.
     resolveModel(response, chunk[1], chunk[2]);
-  } else if (chunk[0] === 'M') {
+  } else if (chunk[0] === 'I') {
     // $FlowFixMe `Chunk` doesn't flow into `JSONValue` because of the `E` row type.
     resolveModule(response, chunk[1], chunk[2]);
-  } else if (chunk[0] === 'S') {
-    // $FlowFixMe: Flow doesn't support disjoint unions on tuples.
-    resolveSymbol(response, chunk[1], chunk[2]);
   } else {
     if (__DEV__) {
       resolveErrorDev(
diff --git a/packages/react-server-native-relay/src/ReactFlightNativeRelayProtocol.js b/packages/react-server-native-relay/src/ReactFlightNativeRelayProtocol.js
index a69b14407aec1..788fd14293ca3 100644
--- a/packages/react-server-native-relay/src/ReactFlightNativeRelayProtocol.js
+++ b/packages/react-server-native-relay/src/ReactFlightNativeRelayProtocol.js
@@ -18,8 +18,8 @@ export type JSONValue =
   | Array<JSONValue>;
 
 export type RowEncoding =
-  | ['J', number, JSONValue]
-  | ['M', number, ModuleMetaData]
+  | ['O', number, JSONValue]
+  | ['I', number, ModuleMetaData]
   | ['P', number, string]
   | ['S', number, string]
   | [
diff --git a/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js b/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
index 9684fbd3a17f8..a58bf22f0c2a9 100644
--- a/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
+++ b/packages/react-server-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
@@ -146,7 +146,7 @@ export function processModelChunk(
 ): Chunk {
   // $FlowFixMe no good way to define an empty exact object
   const json = convertModelToJSON(request, {}, '', model);
-  return ['J', id, json];
+  return ['O', id, json];
 }
 
 export function processReferenceChunk(
@@ -154,7 +154,7 @@ export function processReferenceChunk(
   id: number,
   reference: string,
 ): Chunk {
-  return ['J', id, reference];
+  return ['O', id, reference];
 }
 
 export function processModuleChunk(
@@ -163,23 +163,7 @@ export function processModuleChunk(
   moduleMetaData: ModuleMetaData,
 ): Chunk {
   // The moduleMetaData is already a JSON serializable value.
-  return ['M', id, moduleMetaData];
-}
-
-export function processProviderChunk(
-  request: Request,
-  id: number,
-  contextName: string,
-): Chunk {
-  return ['P', id, contextName];
-}
-
-export function processSymbolChunk(
-  request: Request,
-  id: number,
-  name: string,
-): Chunk {
-  return ['S', id, name];
+  return ['I', id, moduleMetaData];
 }
 
 export function scheduleWork(callback: () => void) {
diff --git a/packages/react-server/src/ReactFlightServer.js b/packages/react-server/src/ReactFlightServer.js
index 660dc8d5a894f..3d4bd59756cd9 100644
--- a/packages/react-server/src/ReactFlightServer.js
+++ b/packages/react-server/src/ReactFlightServer.js
@@ -38,8 +38,6 @@ import {
   closeWithError,
   processModelChunk,
   processModuleChunk,
-  processProviderChunk,
-  processSymbolChunk,
   processErrorChunkProd,
   processErrorChunkDev,
   processReferenceChunk,
@@ -417,7 +415,15 @@ function serializeByValueID(id: number): string {
 }
 
 function serializeByRefID(id: number): string {
-  return '@' + id.toString(16);
+  return '$L' + id.toString(16);
+}
+
+function serializeSymbolReference(name: string): string {
+  return '$S' + name;
+}
+
+function serializeProviderReference(name: string): string {
+  return '$P' + name;
 }
 
 function serializeClientReference(
@@ -473,7 +479,7 @@ function serializeClientReference(
 }
 
 function escapeStringValue(value: string): string {
-  if (value[0] === '$' || value[0] === '@') {
+  if (value[0] === '$') {
     // We need to escape $ or @ prefixed strings since we use those to encode
     // references to IDs and as special symbol values.
     return '$' + value;
@@ -1110,7 +1116,8 @@ function emitModuleChunk(
 }
 
 function emitSymbolChunk(request: Request, id: number, name: string): void {
-  const processedChunk = processSymbolChunk(request, id, name);
+  const symbolReference = serializeSymbolReference(name);
+  const processedChunk = processReferenceChunk(request, id, symbolReference);
   request.completedModuleChunks.push(processedChunk);
 }
 
@@ -1119,7 +1126,8 @@ function emitProviderChunk(
   id: number,
   contextName: string,
 ): void {
-  const processedChunk = processProviderChunk(request, id, contextName);
+  const contextReference = serializeProviderReference(contextName);
+  const processedChunk = processReferenceChunk(request, id, contextReference);
   request.completedJSONChunks.push(processedChunk);
 }
 
diff --git a/packages/react-server/src/ReactFlightServerConfigStream.js b/packages/react-server/src/ReactFlightServerConfigStream.js
index d5e4ec6f6371a..7364ab86dbfb7 100644
--- a/packages/react-server/src/ReactFlightServerConfigStream.js
+++ b/packages/react-server/src/ReactFlightServerConfigStream.js
@@ -80,7 +80,7 @@ export {
 const stringify = JSON.stringify;
 
 function serializeRowHeader(tag: string, id: number) {
-  return tag + id.toString(16) + ':';
+  return id.toString(16) + ':' + tag;
 }
 
 export function processErrorChunkProd(
@@ -127,7 +127,7 @@ export function processModelChunk(
   model: ReactModel,
 ): Chunk {
   const json: string = stringify(model, request.toJSON);
-  const row = serializeRowHeader('J', id) + json + '\n';
+  const row = id.toString(16) + ':' + json + '\n';
   return stringToChunk(row);
 }
 
@@ -137,7 +137,7 @@ export function processReferenceChunk(
   reference: string,
 ): Chunk {
   const json = stringify(reference);
-  const row = serializeRowHeader('J', id) + json + '\n';
+  const row = id.toString(16) + ':' + json + '\n';
   return stringToChunk(row);
 }
 
@@ -147,26 +147,7 @@ export function processModuleChunk(
   moduleMetaData: ReactModel,
 ): Chunk {
   const json: string = stringify(moduleMetaData);
-  const row = serializeRowHeader('M', id) + json + '\n';
-  return stringToChunk(row);
-}
-
-export function processProviderChunk(
-  request: Request,
-  id: number,
-  contextName: string,
-): Chunk {
-  const row = serializeRowHeader('P', id) + contextName + '\n';
-  return stringToChunk(row);
-}
-
-export function processSymbolChunk(
-  request: Request,
-  id: number,
-  name: string,
-): Chunk {
-  const json = stringify(name);
-  const row = serializeRowHeader('S', id) + json + '\n';
+  const row = serializeRowHeader('I', id) + json + '\n';
   return stringToChunk(row);
 }
 
diff --git a/yarn.lock b/yarn.lock
index bea16f8fbe308..820fa8a937c3e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3274,13 +3274,6 @@ abab@^2.0.5:
   resolved "https://registry.yarnpkg.com/abab/-/abab-2.0.5.tgz#c0b678fb32d60fc1219c784d6a826fe385aeb79a"
   integrity sha512-9IK9EadsbHo6jLWIpxpR6pL0sazTXV6+SQv25ZB+F7Bj9mJNaOc4nCRabwd5M/JwmUa8idz6Eci6eKfJryPs6Q==
 
-abort-controller@^3.0.0:
-  version "3.0.0"
-  resolved "https://registry.yarnpkg.com/abort-controller/-/abort-controller-3.0.0.tgz#eaf54d53b62bae4138e809ca225c8439a6efb392"
-  integrity sha512-h8lQ8tacZYnR3vNQTgibj+tODHI5/+l06Au2Pcriv/Gmet0eaj4TwWH41sO9wnHDiQsEj19q0drzdWdeAHtweg==
-  dependencies:
-    event-target-shim "^5.0.0"
-
 accepts@~1.3.4, accepts@~1.3.5, accepts@~1.3.7:
   version "1.3.7"
   resolved "https://registry.yarnpkg.com/accepts/-/accepts-1.3.7.tgz#531bc726517a3b2b41f850021c6cc15eaab507cd"
@@ -7268,11 +7261,6 @@ etag@~1.8.1:
   resolved "https://registry.yarnpkg.com/etag/-/etag-1.8.1.tgz#41ae2eeb65efa62268aebfea83ac7d79299b0887"
   integrity sha1-Qa4u62XvpiJorr/qg6x9eSmbCIc=
 
-event-target-shim@^5.0.0:
-  version "5.0.1"
-  resolved "https://registry.yarnpkg.com/event-target-shim/-/event-target-shim-5.0.1.tgz#5d4d3ebdf9583d63a5333ce2deb7480ab2b05789"
-  integrity sha512-i/2XbnSz/uxRCU6+NdVJgKWDTM427+MqYbkQzD321DuCQJUqOuJKIA0IM2+W2xtYHdKOmZ4dR6fExsd4SXL+WQ==
-
 event-to-promise@0.8.0:
   version "0.8.0"
   resolved "https://registry.yarnpkg.com/event-to-promise/-/event-to-promise-0.8.0.tgz#4b84f11772b6f25f7752fc74d971531ac6f5b626"