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[flags] add enableEffectEventMutationPhase - #35548

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[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.

As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.

@github-actionsgithub-actionsBot added the React Core Team Opened by a member of the React Core Team label Jan 17, 2026
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Comparing: 087a346...bc2bbc7

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7

rickhanlonii
rickhanlonii commented Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii mentioned this pull request Jan 18, 2026
Merged
rickhanlonii
rickhanlonii commented Jan 18, 2026
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Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js Outdated
});

// @gate enableActivity
it('effect events are fresh in deeply nested hidden Activities', async () => {

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@sebmarkbage this is a simplified test.

jackpope
jackpope approved these changes Jan 22, 2026
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Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js Outdated
rickhanlonii added a commit that referenced this pull request Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot pushed a commit that referenced this pull request Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii merged commit 3aaab92 into react:mainFeb 4, 2026
234 checks passed
github-actionsBot pushed a commit that referenced this pull request Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot pushed a commit that referenced this pull request Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
This was referenced Feb 5, 2026
Closed
Merged
github-actionsBot pushed a commit to code/lib-react that referenced this pull request Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot pushed a commit to code/lib-react that referenced this pull request Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot mentioned this pull request Feb 10, 2026
Closed
@rubennorterubennorte mentioned this pull request Jun 5, 2026
Closed
This was referenced Jul 14, 2026
Open
Merged
hoxyq added a commit that referenced this pull request Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot pushed a commit that referenced this pull request Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot pushed a commit that referenced this pull request Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini mentioned this pull request Aug 26, 2026
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@rickhanlonii@react-sizebot@jackpope
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
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(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
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rickhanlonii:rh/uee-mutation-2
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@rickhanloniirickhanlonii
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Jan 17, 2026•

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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
added
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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
jackpope
approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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@rickhanlonii@react-sizebot@jackpope

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Conversation
@rickhanlonii
@rickhanloniirickhanlonii
commented
Jan 17, 2026•

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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
added
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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
jackpope
approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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@rickhanlonii@react-sizebot@jackpope

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
jackpope
approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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@rickhanlonii@react-sizebot@jackpope

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Conversation
@rickhanlonii
@rickhanloniirickhanlonii
commented
Jan 17, 2026•

edited

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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
added
the 
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Opened by a member of the React Core Team
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Jan 17, 2026
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Jan 17, 2026•

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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
jackpope
approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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@rickhanlonii@react-sizebot@jackpope

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Conversation
@rickhanlonii
@rickhanloniirickhanlonii
commented
Jan 17, 2026•

edited

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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Jan 17, 2026
@react-sizebot
react-sizebot
commented
Jan 17, 2026•

edited

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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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ContributorAuthor
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@sebmarkbage this is a simplified test.
jackpope
jackpope
approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

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pushed a commit
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@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
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@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
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@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
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@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
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, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
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rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
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[flags] add enableEffectEventMutationPhase#35548
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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
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View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
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Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
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Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
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rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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@rickhanlonii@react-sizebot@jackpope

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
[flags] add enableEffectEventMutationPhase by rickhanlonii · Pull Request #35548 · react/react · GitHub
Skip to content
[flags] add enableEffectEventMutationPhase - #35548
Merged
rickhanlonii merged 5 commits into
react:mainfrom 
rickhanlonii:rh/uee-mutation-2
Feb 4, 2026
Merged
[flags] add enableEffectEventMutationPhase#35548
rickhanlonii merged 5 commits into
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rickhanlonii:rh/uee-mutation-2
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@rickhanlonii
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Jan 17, 2026•

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Small optimization for useEffectEvent. Not sure we even need a flag for it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when enableViewTransition is on, where we were not updating the useEffectEvent callback when a tree went from hidden to visible.
@github-actionsgithub-actionsBot
added
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Comparing: 087a346...bc2bbc7
Critical size changes
Includes critical production bundles, as well as any change greater than 2%:
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-stable/react-dom/cjs/react-dom-client.production.js=610.53 kB610.53 kB=107.91 kB107.91 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=676.46 kB676.46 kB=118.87 kB118.87 kB
facebook-www/ReactDOM-prod.classic.js+0.07%696.25 kB696.77 kB+0.12%122.34 kB122.49 kB
facebook-www/ReactDOM-prod.modern.js+0.08%686.63 kB687.15 kB+0.12%120.74 kB120.89 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against bc2bbc7
rickhanlonii
rickhanlonii
commented
Jan 17, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
@rickhanloniirickhanlonii
mentioned this pull request
Jan 18, 2026
 Merged

rickhanlonii
rickhanlonii
commented
Jan 18, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

 });

 // @gate enableActivity
 it('effect events are fresh in deeply nested hidden Activities', async () => {
@rickhanloniirickhanloniiJan 18, 2026

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@sebmarkbage this is a simplified test.
jackpope
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approved these changes
Jan 22, 2026
View reviewed changes
Comment threadpackages/react-reconciler/src/__tests__/useEffectEvent-test.js
Outdated

rickhanlonii added a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
087a346
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[test] add activity test with gSBU and enableViewTransition bugfix (#…
f44a4f7
…35555)
Related to #35548,
`enableViewTransition` fixes a bug where `getSnapshotBeforeUpdate` was
running in hidden trees when it shouldn't (`componentWillUpdate` won't
run for hidden updates, and when it becomes visible it will be called
with `componentWillMount`).
DiffTrain build for [087a346](087a346)
@rickhanlonii
rickhanlonii
merged commit 3aaab92
into
react:mainFeb 4, 2026

234 checks passed

github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
9c2b30b
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)
github-actionsBot
pushed a commit
that referenced
this pull request
Feb 4, 2026
@rickhanlonii
[flags] add enableEffectEventMutationPhase (#35548)
5c2f13a
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](3aaab92)

This was referenced Feb 5, 2026
 Closed

 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
3801d70
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Feb 8, 2026
@pull
[flags] add enableEffectEventMutationPhase (react#35548)
f6130b3
Small optimization for useEffectEvent. Not sure we even need a flag for
it, but it will be a nice killswitch.
As an added benefit, it fixes a bug when `enableViewTransition` is on,
where we were not updating the useEffectEvent callback when a tree went
from hidden to visible.
DiffTrain build for [3aaab92](react@3aaab92)
@github-actionsgithub-actionsBot
mentioned this pull request
Feb 10, 2026

Closed

@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed


This was referenced Jul 14, 2026
 Open

 Merged

hoxyq added a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
cec5a9b
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
bfbe77d
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
github-actionsBot
pushed a commit
that referenced
this pull request
Jul 16, 2026
@hoxyq
Enable enableEffectEventMutationPhase everywhere (#37039)
8e12584
Enable it first, will be removed later in
#37013, once it gets to stable.
See #35548 for context on the gated
changes.
DiffTrain build for [cec5a9b](cec5a9b)
@jfolcinijfolcini
mentioned this pull request
Aug 26, 2026

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