diff --git a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClient.js b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClient.js
index 7a5e51ff63112..b42f52097f547 100644
--- a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClient.js
+++ b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClient.js
@@ -7,10 +7,27 @@
  * @flow
  */
 
-export {
+import type {RowEncoding} from './ReactFlightDOMRelayProtocol';
+
+import type {Response} from 'react-client/src/ReactFlightClient';
+
+import {
   createResponse,
   resolveModel,
   resolveModule,
   resolveError,
   close,
 } from 'react-client/src/ReactFlightClient';
+
+export {createResponse, close};
+
+export function resolveRow(response: Response, chunk: RowEncoding): void {
+  if (chunk[0] === 'J') {
+    resolveModel(response, chunk[1], chunk[2]);
+  } else if (chunk[0] === 'M') {
+    resolveModule(response, chunk[1], chunk[2]);
+  } else {
+    // $FlowFixMe: Flow doesn't support disjoint unions on tuples.
+    resolveError(response, chunk[1], chunk[2].message, chunk[2].stack);
+  }
+}
diff --git a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
index 1dde710b4af81..f816443781700 100644
--- a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
+++ b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayClientHostConfig.js
@@ -26,7 +26,7 @@ export {
 
 export type {ModuleMetaData} from 'ReactFlightDOMRelayClientIntegration';
 
-export opaque type UninitializedModel = JSONValue;
+export type UninitializedModel = JSONValue;
 
 export type Response = ResponseBase;
 
diff --git a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayProtocol.js b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayProtocol.js
new file mode 100644
index 0000000000000..263161d53852d
--- /dev/null
+++ b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayProtocol.js
@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import type {ModuleMetaData} from 'ReactFlightDOMRelayServerIntegration';
+
+export type JSONValue =
+  | string
+  | number
+  | boolean
+  | null
+  | {+[key: string]: JSONValue}
+  | Array<JSONValue>;
+
+export type RowEncoding =
+  | ['J', number, JSONValue]
+  | ['M', number, ModuleMetaData]
+  | [
+      'E',
+      number,
+      {
+        message: string,
+        stack: string,
+        ...
+      },
+    ];
diff --git a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
index 73bc60d4eb896..d3fc134176a96 100644
--- a/packages/react-transport-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
+++ b/packages/react-transport-dom-relay/src/ReactFlightDOMRelayServerHostConfig.js
@@ -7,6 +7,8 @@
  * @flow
  */
 
+import type {RowEncoding, JSONValue} from './ReactFlightDOMRelayProtocol';
+
 import type {Request, ReactModel} from 'react-server/src/ReactFlightServer';
 
 import JSResourceReference from 'JSResourceReference';
@@ -22,9 +24,7 @@ import type {
 import {resolveModelToJSON} from 'react-server/src/ReactFlightServer';
 
 import {
-  emitModel,
-  emitModule,
-  emitError,
+  emitRow,
   resolveModuleMetaData as resolveModuleMetaDataImpl,
 } from 'ReactFlightDOMRelayServerIntegration';
 
@@ -45,34 +45,7 @@ export function resolveModuleMetaData<T>(
   return resolveModuleMetaDataImpl(config, resource);
 }
 
-type JSONValue =
-  | string
-  | number
-  | boolean
-  | null
-  | {+[key: string]: JSONValue}
-  | Array<JSONValue>;
-
-export type Chunk =
-  | {
-      type: 'json',
-      id: number,
-      json: JSONValue,
-    }
-  | {
-      type: 'module',
-      id: number,
-      json: ModuleMetaData,
-    }
-  | {
-      type: 'error',
-      id: number,
-      json: {
-        message: string,
-        stack: string,
-        ...
-      },
-    };
+export type Chunk = RowEncoding;
 
 export function processErrorChunk(
   request: Request,
@@ -80,14 +53,14 @@ export function processErrorChunk(
   message: string,
   stack: string,
 ): Chunk {
-  return {
-    type: 'error',
-    id: id,
-    json: {
+  return [
+    'E',
+    id,
+    {
       message,
       stack,
     },
-  };
+  ];
 }
 
 function convertModelToJSON(
@@ -126,11 +99,7 @@ export function processModelChunk(
   model: ReactModel,
 ): Chunk {
   const json = convertModelToJSON(request, {}, '', model);
-  return {
-    type: 'json',
-    id: id,
-    json: json,
-  };
+  return ['J', id, json];
 }
 
 export function processModuleChunk(
@@ -139,11 +108,7 @@ export function processModuleChunk(
   moduleMetaData: ModuleMetaData,
 ): Chunk {
   // The moduleMetaData is already a JSON serializable value.
-  return {
-    type: 'module',
-    id: id,
-    json: moduleMetaData,
-  };
+  return ['M', id, moduleMetaData];
 }
 
 export function scheduleWork(callback: () => void) {
@@ -155,13 +120,7 @@ export function flushBuffered(destination: Destination) {}
 export function beginWriting(destination: Destination) {}
 
 export function writeChunk(destination: Destination, chunk: Chunk): boolean {
-  if (chunk.type === 'json') {
-    emitModel(destination, chunk.id, chunk.json);
-  } else if (chunk.type === 'module') {
-    emitModule(destination, chunk.id, chunk.json);
-  } else {
-    emitError(destination, chunk.id, chunk.json.message, chunk.json.stack);
-  }
+  emitRow(destination, chunk);
   return true;
 }
 
diff --git a/packages/react-transport-dom-relay/src/__mocks__/ReactFlightDOMRelayServerIntegration.js b/packages/react-transport-dom-relay/src/__mocks__/ReactFlightDOMRelayServerIntegration.js
index 3a873ffcad392..cc755f8eaee71 100644
--- a/packages/react-transport-dom-relay/src/__mocks__/ReactFlightDOMRelayServerIntegration.js
+++ b/packages/react-transport-dom-relay/src/__mocks__/ReactFlightDOMRelayServerIntegration.js
@@ -8,26 +8,8 @@
 'use strict';
 
 const ReactFlightDOMRelayServerIntegration = {
-  emitModel(destination, id, json) {
-    destination.push({
-      type: 'json',
-      id: id,
-      json: json,
-    });
-  },
-  emitModule(destination, id, json) {
-    destination.push({
-      type: 'module',
-      id: id,
-      json: json,
-    });
-  },
-  emitError(destination, id, message, stack) {
-    destination.push({
-      type: 'error',
-      id: id,
-      json: {message, stack},
-    });
+  emitRow(destination, json) {
+    destination.push(json);
   },
   close(destination) {},
   resolveModuleMetaData(config, resource) {
diff --git a/packages/react-transport-dom-relay/src/__tests__/ReactFlightDOMRelay-test.internal.js b/packages/react-transport-dom-relay/src/__tests__/ReactFlightDOMRelay-test.internal.js
index 035f5c1abd0b8..092e12abac9d0 100644
--- a/packages/react-transport-dom-relay/src/__tests__/ReactFlightDOMRelay-test.internal.js
+++ b/packages/react-transport-dom-relay/src/__tests__/ReactFlightDOMRelay-test.internal.js
@@ -30,18 +30,7 @@ describe('ReactFlightDOMRelay', () => {
     const response = ReactDOMFlightRelayClient.createResponse();
     for (let i = 0; i < data.length; i++) {
       const chunk = data[i];
-      if (chunk.type === 'json') {
-        ReactDOMFlightRelayClient.resolveModel(response, chunk.id, chunk.json);
-      } else if (chunk.type === 'module') {
-        ReactDOMFlightRelayClient.resolveModule(response, chunk.id, chunk.json);
-      } else {
-        ReactDOMFlightRelayClient.resolveError(
-          response,
-          chunk.id,
-          chunk.json.message,
-          chunk.json.stack,
-        );
-      }
+      ReactDOMFlightRelayClient.resolveRow(response, chunk);
     }
     ReactDOMFlightRelayClient.close(response);
     const model = response.readRoot();
diff --git a/packages/react-transport-native-relay/src/ReactFlightNativeRelayClient.js b/packages/react-transport-native-relay/src/ReactFlightNativeRelayClient.js
index 7a5e51ff63112..94222c0ca7136 100644
--- a/packages/react-transport-native-relay/src/ReactFlightNativeRelayClient.js
+++ b/packages/react-transport-native-relay/src/ReactFlightNativeRelayClient.js
@@ -7,10 +7,27 @@
  * @flow
  */
 
-export {
+import type {RowEncoding} from './ReactFlightNativeRelayProtocol';
+
+import type {Response} from 'react-client/src/ReactFlightClient';
+
+import {
   createResponse,
   resolveModel,
   resolveModule,
   resolveError,
   close,
 } from 'react-client/src/ReactFlightClient';
+
+export {createResponse, close};
+
+export function resolveRow(response: Response, chunk: RowEncoding): void {
+  if (chunk[0] === 'J') {
+    resolveModel(response, chunk[1], chunk[2]);
+  } else if (chunk[0] === 'M') {
+    resolveModule(response, chunk[1], chunk[2]);
+  } else {
+    // $FlowFixMe: Flow doesn't support disjoint unions on tuples.
+    resolveError(response, chunk[1], chunk[2].message, chunk[2].stack);
+  }
+}
diff --git a/packages/react-transport-native-relay/src/ReactFlightNativeRelayClientHostConfig.js b/packages/react-transport-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
index 035dcaf9f4c19..b13d18b3c4098 100644
--- a/packages/react-transport-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
+++ b/packages/react-transport-native-relay/src/ReactFlightNativeRelayClientHostConfig.js
@@ -26,7 +26,7 @@ export {
 
 export type {ModuleMetaData} from 'ReactFlightNativeRelayClientIntegration';
 
-export opaque type UninitializedModel = JSONValue;
+export type UninitializedModel = JSONValue;
 
 export type Response = ResponseBase;
 
diff --git a/packages/react-transport-native-relay/src/ReactFlightNativeRelayProtocol.js b/packages/react-transport-native-relay/src/ReactFlightNativeRelayProtocol.js
new file mode 100644
index 0000000000000..5689f8c0f974c
--- /dev/null
+++ b/packages/react-transport-native-relay/src/ReactFlightNativeRelayProtocol.js
@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import type {ModuleMetaData} from 'ReactFlightNativeRelayServerIntegration';
+
+export type JSONValue =
+  | string
+  | number
+  | boolean
+  | null
+  | {+[key: string]: JSONValue}
+  | Array<JSONValue>;
+
+export type RowEncoding =
+  | ['J', number, JSONValue]
+  | ['M', number, ModuleMetaData]
+  | [
+      'E',
+      number,
+      {
+        message: string,
+        stack: string,
+        ...
+      },
+    ];
diff --git a/packages/react-transport-native-relay/src/ReactFlightNativeRelayServerHostConfig.js b/packages/react-transport-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
index 3992b670e1fa0..bd28ee0337521 100644
--- a/packages/react-transport-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
+++ b/packages/react-transport-native-relay/src/ReactFlightNativeRelayServerHostConfig.js
@@ -7,6 +7,8 @@
  * @flow
  */
 
+import type {RowEncoding, JSONValue} from './ReactFlightNativeRelayProtocol';
+
 import type {Request, ReactModel} from 'react-server/src/ReactFlightServer';
 
 import JSResourceReferenceImpl from 'JSResourceReferenceImpl';
@@ -22,9 +24,7 @@ import type {
 import {resolveModelToJSON} from 'react-server/src/ReactFlightServer';
 
 import {
-  emitModel,
-  emitModule,
-  emitError,
+  emitRow,
   resolveModuleMetaData as resolveModuleMetaDataImpl,
 } from 'ReactFlightNativeRelayServerIntegration';
 
@@ -45,34 +45,7 @@ export function resolveModuleMetaData<T>(
   return resolveModuleMetaDataImpl(config, resource);
 }
 
-type JSONValue =
-  | string
-  | number
-  | boolean
-  | null
-  | {+[key: string]: JSONValue}
-  | Array<JSONValue>;
-
-export type Chunk =
-  | {
-      type: 'json',
-      id: number,
-      json: JSONValue,
-    }
-  | {
-      type: 'module',
-      id: number,
-      json: ModuleMetaData,
-    }
-  | {
-      type: 'error',
-      id: number,
-      json: {
-        message: string,
-        stack: string,
-        ...
-      },
-    };
+export type Chunk = RowEncoding;
 
 export function processErrorChunk(
   request: Request,
@@ -80,14 +53,14 @@ export function processErrorChunk(
   message: string,
   stack: string,
 ): Chunk {
-  return {
-    type: 'error',
-    id: id,
-    json: {
+  return [
+    'E',
+    id,
+    {
       message,
       stack,
     },
-  };
+  ];
 }
 
 function convertModelToJSON(
@@ -126,11 +99,7 @@ export function processModelChunk(
   model: ReactModel,
 ): Chunk {
   const json = convertModelToJSON(request, {}, '', model);
-  return {
-    type: 'json',
-    id: id,
-    json: json,
-  };
+  return ['J', id, json];
 }
 
 export function processModuleChunk(
@@ -139,11 +108,7 @@ export function processModuleChunk(
   moduleMetaData: ModuleMetaData,
 ): Chunk {
   // The moduleMetaData is already a JSON serializable value.
-  return {
-    type: 'module',
-    id: id,
-    json: moduleMetaData,
-  };
+  return ['M', id, moduleMetaData];
 }
 
 export function scheduleWork(callback: () => void) {
@@ -155,13 +120,7 @@ export function flushBuffered(destination: Destination) {}
 export function beginWriting(destination: Destination) {}
 
 export function writeChunk(destination: Destination, chunk: Chunk): boolean {
-  if (chunk.type === 'json') {
-    emitModel(destination, chunk.id, chunk.json);
-  } else if (chunk.type === 'module') {
-    emitModule(destination, chunk.id, chunk.json);
-  } else {
-    emitError(destination, chunk.id, chunk.json.message, chunk.json.stack);
-  }
+  emitRow(destination, chunk);
   return true;
 }
 
diff --git a/packages/react-transport-native-relay/src/__mocks__/ReactFlightNativeRelayServerIntegration.js b/packages/react-transport-native-relay/src/__mocks__/ReactFlightNativeRelayServerIntegration.js
index 197048cc50c89..eec41c718881a 100644
--- a/packages/react-transport-native-relay/src/__mocks__/ReactFlightNativeRelayServerIntegration.js
+++ b/packages/react-transport-native-relay/src/__mocks__/ReactFlightNativeRelayServerIntegration.js
@@ -8,26 +8,8 @@
 'use strict';
 
 const ReactFlightNativeRelayServerIntegration = {
-  emitModel(destination, id, json) {
-    destination.push({
-      type: 'json',
-      id: id,
-      json: json,
-    });
-  },
-  emitModule(destination, id, json) {
-    destination.push({
-      type: 'module',
-      id: id,
-      json: json,
-    });
-  },
-  emitError(destination, id, message, stack) {
-    destination.push({
-      type: 'error',
-      id: id,
-      json: {message, stack},
-    });
+  emitRow(destination, json) {
+    destination.push(json);
   },
   close(destination) {},
   resolveModuleMetaData(config, resource) {
diff --git a/packages/react-transport-native-relay/src/__tests__/ReactFlightNativeRelay-test.internal.js b/packages/react-transport-native-relay/src/__tests__/ReactFlightNativeRelay-test.internal.js
index 48742e6bc1cbf..cf893bca760e6 100644
--- a/packages/react-transport-native-relay/src/__tests__/ReactFlightNativeRelay-test.internal.js
+++ b/packages/react-transport-native-relay/src/__tests__/ReactFlightNativeRelay-test.internal.js
@@ -45,26 +45,7 @@ describe('ReactFlightNativeRelay', () => {
     const response = ReactNativeFlightRelayClient.createResponse();
     for (let i = 0; i < data.length; i++) {
       const chunk = data[i];
-      if (chunk.type === 'json') {
-        ReactNativeFlightRelayClient.resolveModel(
-          response,
-          chunk.id,
-          chunk.json,
-        );
-      } else if (chunk.type === 'module') {
-        ReactNativeFlightRelayClient.resolveModule(
-          response,
-          chunk.id,
-          chunk.json,
-        );
-      } else {
-        ReactNativeFlightRelayClient.resolveError(
-          response,
-          chunk.id,
-          chunk.json.message,
-          chunk.json.stack,
-        );
-      }
+      ReactNativeFlightRelayClient.resolveRow(response, chunk);
     }
     ReactNativeFlightRelayClient.close(response);
     const model = response.readRoot();
diff --git a/scripts/flow/react-relay-hooks.js b/scripts/flow/react-relay-hooks.js
index 00fdbc839741a..73eb20ef41272 100644
--- a/scripts/flow/react-relay-hooks.js
+++ b/scripts/flow/react-relay-hooks.js
@@ -35,22 +35,10 @@ declare module 'JSResourceReferenceImpl' {
 declare module 'ReactFlightDOMRelayServerIntegration' {
   declare export opaque type Destination;
   declare export opaque type BundlerConfig;
-  declare export function emitModel(
+  declare export function emitRow(
     destination: Destination,
-    id: number,
     json: JSONValue,
   ): void;
-  declare export function emitModule(
-    destination: Destination,
-    id: number,
-    json: ModuleMetaData,
-  ): void;
-  declare export function emitError(
-    destination: Destination,
-    id: number,
-    message: string,
-    stack: string,
-  ): void;
   declare export function close(destination: Destination): void;
 
   declare export type ModuleMetaData = JSONValue;
@@ -76,22 +64,10 @@ declare module 'ReactFlightDOMRelayClientIntegration' {
 declare module 'ReactFlightNativeRelayServerIntegration' {
   declare export opaque type Destination;
   declare export opaque type BundlerConfig;
-  declare export function emitModel(
+  declare export function emitRow(
     destination: Destination,
-    id: number,
     json: JSONValue,
   ): void;
-  declare export function emitModule(
-    destination: Destination,
-    id: number,
-    json: ModuleMetaData,
-  ): void;
-  declare export function emitError(
-    destination: Destination,
-    id: number,
-    message: string,
-    stack: string,
-  ): void;
   declare export function close(destination: Destination): void;
 
   declare export type ModuleMetaData = JSONValue;