Fix: uDV skipped initial value if earlier transition suspended (#34376)

Fixes a bug in useDeferredValue's optional `initialValue` argument. In
the regression case, if a new useDeferredValue hook is mounted while an
earlier transition is suspended, the `initialValue` argument of the new
hook was ignored. After the fix, the `initialValue` argument is
correctly rendered during the initial mount, regardless of whether other
transitions were suspended.

The culprit was related to the mechanism we use to track whether a
render is the result of a `useDeferredValue` hook: we assign the
deferred lane a TransitionLane, then entangle that lane with the
DeferredLane bit. During the subsequent render, we check for the
presence of the DeferredLane bit to determine whether to switch to the
final, canonical value.

But because transition lanes can themselves become entangled with other
transitions, the effect is that every entangled transition was being
treated as if it were the result of a `useDeferredValue` hook, causing
us to skip the initial value and go straight to the final one.

The fix I've chosen is to reserve some subset of TransitionLanes to be
used only for deferred work, instead of using entanglement. This is
similar to how retries are already implemented. Originally I tried not
to implement it this way because it means there are now slightly fewer
lanes allocated for regular transitions, but I underestimated how
similar deferred work is to retries; they end up having a lot of the
same requirements. Eventually it may be possible to merge the two
concepts.

DiffTrain build for [3302d1f](3302d1f)

Author: acdlite

compiled-rn/VERSION_NATIVE_FB

@@ -1 +1 @@
-19.2.0-native-fb-3168e08f-20250903
+19.2.0-native-fb-3302d1f7-20250903

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/react-dom/cjs/ReactDOM-dev.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<e16d4d0e56b0093108153a8e5c2fa6ec>>
+ * @generated SignedSource<<56ac6a5f9e0a15495324372ea00e8858>>
  */
 
 "use strict";
@@ -404,5 +404,5 @@ __DEV__ &&
     exports.useFormStatus = function () {
       return resolveDispatcher().useHostTransitionStatus();
     };
-    exports.version = "19.2.0-native-fb-3168e08f-20250903";
+    exports.version = "19.2.0-native-fb-3302d1f7-20250903";
   })();

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/react-dom/cjs/ReactDOM-prod.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<5c28310e31f7b026d9838c06862fa435>>
+ * @generated SignedSource<<73920b47ab48258a511372994a8afedd>>
  */
 
 "use strict";
@@ -203,4 +203,4 @@ exports.useFormState = function (action, initialState, permalink) {
 exports.useFormStatus = function () {
   return ReactSharedInternals.H.useHostTransitionStatus();
 };
-exports.version = "19.2.0-native-fb-3168e08f-20250903";
+exports.version = "19.2.0-native-fb-3302d1f7-20250903";

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/react-dom/cjs/ReactDOM-profiling.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<5c28310e31f7b026d9838c06862fa435>>
+ * @generated SignedSource<<73920b47ab48258a511372994a8afedd>>
  */
 
 "use strict";
@@ -203,4 +203,4 @@ exports.useFormState = function (action, initialState, permalink) {
 exports.useFormStatus = function () {
   return ReactSharedInternals.H.useHostTransitionStatus();
 };
-exports.version = "19.2.0-native-fb-3168e08f-20250903";
+exports.version = "19.2.0-native-fb-3302d1f7-20250903";

compiled-rn/facebook-fbsource/xplat/js/RKJSModules/vendor/react/react-dom/cjs/ReactDOMClient-dev.js

@@ -7,7 +7,7 @@
  * @noflow
  * @nolint
  * @preventMunge
- * @generated SignedSource<<3281970e07dea5fb521ac7664dbecc34>>
+ * @generated SignedSource<<145774a31461bc1e01f4c25468795fd9>>
  */
 
 /*
@@ -714,7 +714,8 @@ function clz32Fallback(x) {
   x >>>= 0;
   return 0 === x ? 32 : (31 - ((log(x) / LN2) | 0)) | 0;
 }
-var nextTransitionLane = 256,
+var nextTransitionUpdateLane = 256,
+  nextTransitionDeferredLane = 262144,
   nextRetryLane = 4194304;
 function getHighestPriorityLanes(lanes) {
   var pendingSyncLanes = lanes & 42;
@@ -746,11 +747,12 @@ function getHighestPriorityLanes(lanes) {
     case 32768:
     case 65536:
     case 131072:
+      return lanes & 261888;
     case 262144:
     case 524288:
     case 1048576:
     case 2097152:
-      return lanes & 4194048;
+      return lanes & 3932160;
     case 4194304:
     case 8388608:
     case 16777216:
@@ -859,12 +861,6 @@ function computeExpirationTime(lane, currentTime) {
       return -1;
   }
 }
-function claimNextTransitionLane() {
-  var lane = nextTransitionLane;
-  nextTransitionLane <<= 1;
-  0 === (nextTransitionLane & 4194048) && (nextTransitionLane = 256);
-  return lane;
-}
 function claimNextRetryLane() {
   var lane = nextRetryLane;
   nextRetryLane <<= 1;
@@ -937,7 +933,7 @@ function markSpawnedDeferredLane(root, spawnedLane, entangledLanes) {
   root.entanglements[spawnedLaneIndex] =
     root.entanglements[spawnedLaneIndex] |
     1073741824 |
-    (entangledLanes & 4194090);
+    (entangledLanes & 261930);
 }
 function markRootEntangled(root, entangledLanes) {
   var rootEntangledLanes = (root.entangledLanes |= entangledLanes);
@@ -5434,7 +5430,11 @@ function updateMemo(nextCreate, deps) {
   return prevState;
 }
 function mountDeferredValueImpl(hook, value, initialValue) {
-  if (void 0 === initialValue || 0 !== (renderLanes & 1073741824))
+  if (
+    void 0 === initialValue ||
+    (0 !== (renderLanes & 1073741824) &&
+      0 === (workInProgressRootRenderLanes & 261930))
+  )
     return (hook.memoizedState = value);
   hook.memoizedState = initialValue;
   hook = requestDeferredLane();
@@ -5450,7 +5450,11 @@ function updateDeferredValueImpl(hook, prevValue, value, initialValue) {
       objectIs(hook, prevValue) || (didReceiveUpdate = !0),
       hook
     );
-  if (0 === (renderLanes & 42) || 0 !== (renderLanes & 1073741824))
+  if (
+    0 === (renderLanes & 42) ||
+    (0 !== (renderLanes & 1073741824) &&
+      0 === (workInProgressRootRenderLanes & 261930))
+  )
     return (didReceiveUpdate = !0), (hook.memoizedState = value);
   hook = requestDeferredLane();
   currentlyRenderingFiber.lanes |= hook;
@@ -11447,13 +11451,16 @@ function requestUpdateLane(fiber) {
         : resolveUpdatePriority();
 }
 function requestDeferredLane() {
-  0 === workInProgressDeferredLane &&
-    (workInProgressDeferredLane =
-      0 === (workInProgressRootRenderLanes & 536870912) || isHydrating
-        ? claimNextTransitionLane()
-        : 536870912);
-  var suspenseHandler = suspenseHandlerStackCursor.current;
-  null !== suspenseHandler && (suspenseHandler.flags |= 32);
+  if (0 === workInProgressDeferredLane)
+    if (0 === (workInProgressRootRenderLanes & 536870912) || isHydrating) {
+      var lane = nextTransitionDeferredLane;
+      nextTransitionDeferredLane <<= 1;
+      0 === (nextTransitionDeferredLane & 3932160) &&
+        (nextTransitionDeferredLane = 262144);
+      workInProgressDeferredLane = lane;
+    } else workInProgressDeferredLane = 536870912;
+  lane = suspenseHandlerStackCursor.current;
+  null !== lane && (lane.flags |= 32);
   return workInProgressDeferredLane;
 }
 function scheduleUpdateOnFiber(root, fiber, lane) {
@@ -12530,7 +12537,7 @@ function flushSpawnedWork() {
     0 !== (pendingEffectsLanes & 3) && 0 !== root.tag && flushPendingEffects();
     ensureRootIsScheduled(root);
     remainingLanes = root.pendingLanes;
-    0 !== (lanes & 4194090) && 0 !== (remainingLanes & 42)
+    0 !== (lanes & 261930) && 0 !== (remainingLanes & 42)
       ? root === rootWithNestedUpdates
         ? nestedUpdateCount++
         : ((nestedUpdateCount = 0), (rootWithNestedUpdates = root))
@@ -12981,8 +12988,12 @@ function scheduleImmediateRootScheduleTask() {
 function requestTransitionLane() {
   if (0 === currentEventTransitionLane) {
     var actionScopeLane = currentEntangledLane;
-    currentEventTransitionLane =
-      0 !== actionScopeLane ? actionScopeLane : claimNextTransitionLane();
+    0 === actionScopeLane &&
+      ((actionScopeLane = nextTransitionUpdateLane),
+      (nextTransitionUpdateLane <<= 1),
+      0 === (nextTransitionUpdateLane & 261888) &&
+        (nextTransitionUpdateLane = 256));
+    currentEventTransitionLane = actionScopeLane;
   }
   return currentEventTransitionLane;
 }
@@ -13116,20 +13127,20 @@ function debounceScrollEnd(targetInst, nativeEvent, nativeEventTarget) {
     (nativeEventTarget[internalScrollTimer] = targetInst));
 }
 for (
-  var i$jscomp$inline_1646 = 0;
-  i$jscomp$inline_1646 < simpleEventPluginEvents.length;
-  i$jscomp$inline_1646++
+  var i$jscomp$inline_1651 = 0;
+  i$jscomp$inline_1651 < simpleEventPluginEvents.length;
+  i$jscomp$inline_1651++
 ) {
-  var eventName$jscomp$inline_1647 =
-      simpleEventPluginEvents[i$jscomp$inline_1646],
-    domEventName$jscomp$inline_1648 =
-      eventName$jscomp$inline_1647.toLowerCase(),
-    capitalizedEvent$jscomp$inline_1649 =
-      eventName$jscomp$inline_1647[0].toUpperCase() +
-      eventName$jscomp$inline_1647.slice(1);
+  var eventName$jscomp$inline_1652 =
+      simpleEventPluginEvents[i$jscomp$inline_1651],
+    domEventName$jscomp$inline_1653 =
+      eventName$jscomp$inline_1652.toLowerCase(),
+    capitalizedEvent$jscomp$inline_1654 =
+      eventName$jscomp$inline_1652[0].toUpperCase() +
+      eventName$jscomp$inline_1652.slice(1);
   registerSimpleEvent(
-    domEventName$jscomp$inline_1648,
-    "on" + capitalizedEvent$jscomp$inline_1649
+    domEventName$jscomp$inline_1653,
+    "on" + capitalizedEvent$jscomp$inline_1654
   );
 }
 registerSimpleEvent(ANIMATION_END, "onAnimationEnd");
@@ -17375,16 +17386,16 @@ ReactDOMHydrationRoot.prototype.unstable_scheduleHydration = function (target) {
     0 === i && attemptExplicitHydrationTarget(target);
   }
 };
-var isomorphicReactPackageVersion$jscomp$inline_2052 = React.version;
+var isomorphicReactPackageVersion$jscomp$inline_2057 = React.version;
 if (
-  "19.2.0-native-fb-3168e08f-20250903" !==
-  isomorphicReactPackageVersion$jscomp$inline_2052
+  "19.2.0-native-fb-3302d1f7-20250903" !==
+  isomorphicReactPackageVersion$jscomp$inline_2057
 )
   throw Error(
     formatProdErrorMessage(
       527,
-      isomorphicReactPackageVersion$jscomp$inline_2052,
-      "19.2.0-native-fb-3168e08f-20250903"
+      isomorphicReactPackageVersion$jscomp$inline_2057,
+      "19.2.0-native-fb-3302d1f7-20250903"
     )
   );
 ReactDOMSharedInternals.findDOMNode = function (componentOrElement) {
@@ -17404,24 +17415,24 @@ ReactDOMSharedInternals.findDOMNode = function (componentOrElement) {
     null === componentOrElement ? null : componentOrElement.stateNode;
   return componentOrElement;
 };
-var internals$jscomp$inline_2625 = {
+var internals$jscomp$inline_2630 = {
   bundleType: 0,
-  version: "19.2.0-native-fb-3168e08f-20250903",
+  version: "19.2.0-native-fb-3302d1f7-20250903",
   rendererPackageName: "react-dom",
   currentDispatcherRef: ReactSharedInternals,
-  reconcilerVersion: "19.2.0-native-fb-3168e08f-20250903"
+  reconcilerVersion: "19.2.0-native-fb-3302d1f7-20250903"
 };
 if ("undefined" !== typeof __REACT_DEVTOOLS_GLOBAL_HOOK__) {
-  var hook$jscomp$inline_2626 = __REACT_DEVTOOLS_GLOBAL_HOOK__;
+  var hook$jscomp$inline_2631 = __REACT_DEVTOOLS_GLOBAL_HOOK__;
   if (
-    !hook$jscomp$inline_2626.isDisabled &&
-    hook$jscomp$inline_2626.supportsFiber
+    !hook$jscomp$inline_2631.isDisabled &&
+    hook$jscomp$inline_2631.supportsFiber
   )
     try {
-      (rendererID = hook$jscomp$inline_2626.inject(
-        internals$jscomp$inline_2625
+      (rendererID = hook$jscomp$inline_2631.inject(
+        internals$jscomp$inline_2630
       )),
-        (injectedHook = hook$jscomp$inline_2626);
+        (injectedHook = hook$jscomp$inline_2631);
     } catch (err) {}
 }
 exports.createRoot = function (container, options) {
@@ -17516,4 +17527,4 @@ exports.hydrateRoot = function (container, initialChildren, options) {
   listenToAllSupportedEvents(container);
   return new ReactDOMHydrationRoot(initialChildren);
 };
-exports.version = "19.2.0-native-fb-3168e08f-20250903";
+exports.version = "19.2.0-native-fb-3302d1f7-20250903";