From eb8feb71096eec5c885b2a4c7d8d030d3622f265 Mon Sep 17 00:00:00 2001
From: Andrew Clark <git@andrewclark.io>
Date: Fri, 14 Aug 2026 13:26:45 -0400
Subject: [PATCH] [flags] Enable enableParallelTransitions (#37290)

Reverse #35709. Turn the flag on in the OSS/canary default and in every
hardcoded fork, including the native (RN) forks, and keep the test
renderers in sync. www stays GK-driven, so `www.js` and `www-dynamic.js`
are unchanged.

Leaving the flag in the repo for now; this just flips the default on.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 packages/shared/ReactFeatureFlags.js                            | 2 +-
 packages/shared/forks/ReactFeatureFlags.native-fb.js            | 2 +-
 packages/shared/forks/ReactFeatureFlags.native-oss.js           | 2 +-
 packages/shared/forks/ReactFeatureFlags.test-renderer.js        | 2 +-
 .../shared/forks/ReactFeatureFlags.test-renderer.native-fb.js   | 2 +-
 packages/shared/forks/ReactFeatureFlags.test-renderer.www.js    | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index 1ff32fda3166..94c7287f5260 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -232,7 +232,7 @@ export const disableInputAttributeSyncing: boolean = false;
 export const disableTextareaChildren: boolean = false;
 
 // Disables children for <textarea> elements
-export const enableParallelTransitions: boolean = false;
+export const enableParallelTransitions: boolean = true;
 
 // -----------------------------------------------------------------------------
 // Debugging and DevTools
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index 575c1faac9a1..88bf7b9c1457 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -87,7 +87,7 @@ export const enablePerformanceIssueReporting: boolean =
   enableComponentPerformanceTrack;
 export const enableInternalInstanceMap: boolean = false;
 export const enableOptimisticKey: boolean = false;
-export const enableParallelTransitions: boolean = false;
+export const enableParallelTransitions: boolean = true;
 
 export const eprh_enableUseKeyedStateCompilerLint: boolean = false;
 export const eprh_enableVerboseNoSetStateInEffectCompilerLint: boolean = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-oss.js b/packages/shared/forks/ReactFeatureFlags.native-oss.js
index 7dd8c4add2dd..01dee4006991 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-oss.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-oss.js
@@ -87,7 +87,7 @@ export const enableProfilerTimer: boolean = __PROFILE__;
 export const enableProfilerCommitHooks: boolean = __PROFILE__;
 export const enableProfilerNestedUpdatePhase: boolean = __PROFILE__;
 export const enableUpdaterTracking: boolean = __PROFILE__;
-export const enableParallelTransitions: boolean = false;
+export const enableParallelTransitions: boolean = true;
 
 export const eprh_enableUseKeyedStateCompilerLint: boolean = false;
 export const eprh_enableVerboseNoSetStateInEffectCompilerLint: boolean = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
index 537becd97525..feac1b0e531e 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
@@ -96,7 +96,7 @@ export const enableReactTestRendererWarning: boolean = true;
 export const enableObjectFiber: boolean = false;
 
 export const enableOptimisticKey: boolean = false;
-export const enableParallelTransitions: boolean = false;
+export const enableParallelTransitions: boolean = true;
 
 export const eprh_enableUseKeyedStateCompilerLint: boolean = false;
 export const eprh_enableVerboseNoSetStateInEffectCompilerLint: boolean = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js
index ec5b5263179b..7874a004bd90 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.native-fb.js
@@ -73,7 +73,7 @@ export const enableFragmentRefsInstanceHandles = false;
 export const enableFragmentRefsTextNodes = false;
 export const ownerStackLimit = 1e4;
 export const enableOptimisticKey = false;
-export const enableParallelTransitions = false;
+export const enableParallelTransitions = true;
 
 export const eprh_enableUseKeyedStateCompilerLint: boolean = false;
 export const eprh_enableVerboseNoSetStateInEffectCompilerLint: boolean = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
index d35cf325f337..9615490eb6d9 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
@@ -88,7 +88,7 @@ export const ownerStackLimit = 1e4;
 export const enableInternalInstanceMap: boolean = false;
 
 export const enableOptimisticKey: boolean = false;
-export const enableParallelTransitions: boolean = false;
+export const enableParallelTransitions: boolean = true;
 
 export const eprh_enableUseKeyedStateCompilerLint: boolean = false;
 export const eprh_enableVerboseNoSetStateInEffectCompilerLint: boolean = false;