[Fiber] Instrument the lazy initializer thenable in all cases - #35521

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gnoff merged 1 commit into
react:mainfrom
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged

[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom
gnoff:jstory/instrument-lazy-thenable-always

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now

@github-actionsgithub-actionsBot added the React Core Team Opened by a member of the React Core Team label Jan 16, 2026
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Comparing: 4cf9063...a17b694

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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB

Significant size changes

Includes any change greater than 0.2%:

Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694

@gnoff
gnoffforce-pushed the jstory/instrument-lazy-thenable-always branch 2 times, most recently from 3e36142 to ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed the jstory/instrument-lazy-thenable-always branch from ea92656 to a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff merged commit db71391 into react:mainJan 16, 2026
234 checks passed
@gnoff
gnoff deleted the jstory/instrument-lazy-thenable-always branch January 16, 2026 03:05
github-actionsBot pushed a commit that referenced this pull request Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot pushed a commit that referenced this pull request Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot mentioned this pull request Jan 16, 2026
Merged
github-actionsBot pushed a commit to code/lib-react that referenced this pull request Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot pushed a commit to code/lib-react that referenced this pull request Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte mentioned this pull request Jun 5, 2026
Closed
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@gnoff@react-sizebot@sebmarkbage
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n 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;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
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@gnoff
@gnoffgnoff
commented
Jan 16, 2026•

edited

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Jan 16, 2026
@react-sizebot
react-sizebot
commented
Jan 16, 2026•

edited

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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
2 times, most recently
from
3e36142 to
ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
from
ea92656 to
a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff
merged commit db71391
into
react:mainJan 16, 2026

234 checks passed

@gnoff
gnoff
deleted the

jstory/instrument-lazy-thenable-always

branch
January 16, 2026 03:05
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

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@sebmarkbagesebmarkbagesebmarkbage approved these changes
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3 participants

@gnoff@react-sizebot@sebmarkbage

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Conversation
@gnoff
@gnoffgnoff
commented
Jan 16, 2026•

edited

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
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[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
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github-actionsBot
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@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
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@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
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@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
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mentioned this pull request
Jun 5, 2026
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@gnoff@react-sizebot@sebmarkbage

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[Fiber] Instrument the lazy initializer thenable in all cases - #35521
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[Fiber] Instrument the lazy initializer thenable in all cases#35521
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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
@github-actionsgithub-actionsBot
added
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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
2 times, most recently
from
3e36142 to
ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
from
ea92656 to
a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff
merged commit db71391
into
react:mainJan 16, 2026

234 checks passed

@gnoff
gnoff
deleted the

jstory/instrument-lazy-thenable-always

branch
January 16, 2026 03:05
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

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@gnoff@react-sizebot@sebmarkbage

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
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Jan 16, 2026•

edited

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
@github-actionsgithub-actionsBot
added
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Opened by a member of the React Core Team
label
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@react-sizebot
react-sizebot
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Jan 16, 2026•

edited

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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
2 times, most recently
from
3e36142 to
ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
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from
ea92656 to
a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff
merged commit db71391
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react:mainJan 16, 2026

234 checks passed

@gnoff
gnoff
deleted the

jstory/instrument-lazy-thenable-always

branch
January 16, 2026 03:05
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

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@gnoff@react-sizebot@sebmarkbage

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Conversation
@gnoff
@gnoffgnoff
commented
Jan 16, 2026•

edited

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Collaborator
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Jan 16, 2026
@react-sizebot
react-sizebot
commented
Jan 16, 2026•

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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
2 times, most recently
from
3e36142 to
ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
from
ea92656 to
a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff
merged commit db71391
into
react:mainJan 16, 2026

234 checks passed

@gnoff
gnoff
deleted the

jstory/instrument-lazy-thenable-always

branch
January 16, 2026 03:05
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

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@sebmarkbagesebmarkbagesebmarkbage approved these changes
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3 participants

@gnoff@react-sizebot@sebmarkbage

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
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Jan 16, 2026•

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
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from
3e36142 to
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@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
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gnoff
merged commit db71391
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234 checks passed

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deleted the

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github-actionsBot
pushed a commit
that referenced
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Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
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@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
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@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
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mentioned this pull request
Jun 5, 2026
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3 participants

@gnoff@react-sizebot@sebmarkbage

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

Skip to content
[Fiber] Instrument the lazy initializer thenable in all cases - #35521
Merged
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
Jan 16, 2026
Merged
[Fiber] Instrument the lazy initializer thenable in all cases#35521
gnoff merged 1 commit into
react:mainfrom 
gnoff:jstory/instrument-lazy-thenable-always
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Jan 16, 2026•

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When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. To land the prior PR I changed the thenables to a custom type so I could instrument manually in the test. WIth this change we can just use a regular Promise since ReactLazy will instrument in all environments/flags now
@github-actionsgithub-actionsBot
added
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React Core Team
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Jan 16, 2026
@react-sizebot
react-sizebot
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Jan 16, 2026•

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Comparing: 4cf9063...a17b694
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=608.20 kB608.03 kB=107.66 kB107.62 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB+0.05%1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
facebook-www/ReactDOM-prod.classic.js=693.57 kB693.38 kB=122.05 kB122.01 kB
facebook-www/ReactDOM-prod.modern.js=683.95 kB683.76 kB=120.44 kB120.40 kB
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
Significant size changes
Includes any change greater than 0.2%:
Expand to show
Name+/-BaseCurrent+/- gzipBase gzipCurrent gzip
oss-stable-semver/react/cjs/react.react-server.production.js+2.21%13.51 kB13.81 kB+0.67%3.71 kB3.74 kB
oss-stable/react/cjs/react.react-server.production.js+2.21%13.54 kB13.83 kB+0.67%3.74 kB3.77 kB
oss-stable-semver/react/cjs/react.production.js+1.69%17.74 kB18.04 kB+0.63%4.57 kB4.60 kB
oss-stable/react/cjs/react.production.js+1.68%17.77 kB18.07 kB+0.63%4.60 kB4.63 kB
oss-experimental/react/cjs/react.react-server.production.js+1.56%19.11 kB19.41 kB+0.52%5.00 kB5.03 kB
facebook-react-native/react/cjs/React-prod.js+1.56%19.23 kB19.53 kB+0.59%4.95 kB4.98 kB
oss-experimental/react/cjs/react.production.js+1.54%19.46 kB19.76 kB+0.59%4.92 kB4.95 kB
facebook-react-native/react/cjs/React-profiling.js+1.52%19.66 kB19.96 kB+0.58%5.03 kB5.06 kB
facebook-www/React-prod.modern.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-prod.classic.js+1.48%20.14 kB20.44 kB+0.54%5.17 kB5.20 kB
facebook-www/React-profiling.modern.js+1.45%20.57 kB20.87 kB+0.53%5.25 kB5.28 kB
facebook-www/React-profiling.classic.js+1.45%20.57 kB20.87 kB+0.55%5.25 kB5.28 kB
facebook-react-native/react/cjs/React-dev.js+0.61%52.61 kB52.93 kB+0.31%11.61 kB11.64 kB
oss-experimental/react-art/cjs/react-art.production.js=358.53 kB357.47 kB=60.45 kB60.23 kB
oss-experimental/react-dom/cjs/react-dom-profiling.development.js=1,262.67 kB1,257.62 kB=209.85 kB208.90 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.development.js=1,262.67 kB1,257.62 kB=210.64 kB209.73 kB
oss-experimental/react-dom/cjs/react-dom-client.development.js=1,246.12 kB1,241.07 kB=206.98 kB206.04 kB
oss-experimental/react-dom/cjs/react-dom-unstable_testing.production.js=685.08 kB681.67 kB=121.62 kB121.07 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=670.67 kB667.26 kB=118.08 kB117.51 kB
oss-experimental/react-reconciler/cjs/react-reconciler.development.js=862.37 kB857.88 kB=134.30 kB133.50 kB
oss-experimental/react-dom/cjs/react-dom-profiling.profiling.js=749.95 kB745.88 kB=129.64 kB128.84 kB
oss-experimental/react-art/cjs/react-art.development.js=733.87 kB729.74 kB=115.46 kB114.68 kB
oss-experimental/react-reconciler/cjs/react-reconciler.production.js=491.61 kB488.70 kB=78.19 kB77.71 kB
oss-experimental/react-reconciler/cjs/react-reconciler.profiling.js=567.78 kB564.15 kB=88.42 kB87.75 kB

Generated by 🚫 dangerJS against a17b694
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
2 times, most recently
from
3e36142 to
ea92656CompareJanuary 16, 2026 01:28
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases
a17b694
When a lazy element or component is initialized a thenable is returned which was only be conditionally instrumented in dev when asyncDebugInfo was enabled. When instrumented these thenables can be used in conjunction with the SuspendOnImmediate optimization where if a thenable resolves before the stack unwinds we can continue rendering from the last suspended fiber. Without this change a recent fix to the useId implementation cannot be easily tested in production because this optimization pathway isn't available to regular React.lazy thenables. I could update the test to use a custom thenable but since this optimization is probably worthwhile anyway I am adding the instrumentation to all React.lazy.
@gnoff
gnoffforce-pushed
the
jstory/instrument-lazy-thenable-always
branch
from
ea92656 to
a17b694CompareJanuary 16, 2026 02:57
@gnoff
gnoff
merged commit db71391
into
react:mainJan 16, 2026

234 checks passed

@gnoff
gnoff
deleted the

jstory/instrument-lazy-thenable-always

branch
January 16, 2026 03:05
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
1eb3b47
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
github-actionsBot
pushed a commit
that referenced
this pull request
Jan 16, 2026
@gnoff
[Fiber] Instrument the lazy initializer thenable in all cases (#35521)
f185b57
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](db71391)
@nextjs-botnextjs-bot
mentioned this pull request
Jan 16, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
8276ad7
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Jan 18, 2026
@pull
[Fiber] Instrument the lazy initializer thenable in all cases (react#…
6e94fc8
…35521)
When a lazy element or component is initialized a thenable is returned
which was only be conditionally instrumented in dev when asyncDebugInfo
was enabled. When instrumented these thenables can be used in
conjunction with the SuspendOnImmediate optimization where if a thenable
resolves before the stack unwinds we can continue rendering from the
last suspended fiber. Without this change a recent fix to the useId
implementation cannot be easily tested in production because this
optimization pathway isn't available to regular React.lazy thenables. To
land the prior PR I changed the thenables to a custom type so I could
instrument manually in the test. WIth this change we can just use a
regular Promise since ReactLazy will instrument in all
environments/flags now
DiffTrain build for [db71391](react@db71391)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

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@gnoff@react-sizebot@sebmarkbage