Skip to content

[Flight] Clear chunk reason after successful module initialization - #36024

Merged
unstubbable merged 2 commits into
react:mainfrom
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged

[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom
unstubbable:clear-initialized-module-reason

Conversation

@unstubbable

@unstubbableunstubbable commented Mar 12, 2026

Copy link
Copy Markdown
Collaborator

When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.

When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.

The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.

This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().

@github-actionsgithub-actionsBot added the React Core Team Opened by a member of the React Core Team label Mar 12, 2026
@react-sizebot

react-sizebot commented Mar 12, 2026•
edited
Loading

Copy link
Copy Markdown

Comparing: 7b5b561...b43ee2a

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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against b43ee2a

@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed the clear-initialized-module-reason branch from 523741a to bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable marked this pull request as ready for review March 12, 2026 13:28
eps1lon
eps1lon reviewed Mar 12, 2026
View reviewed changes

@eps1loneps1lon left a comment

Copy link
Copy Markdown
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079

What's the reason we're not doing it there? Worth adding a comment since it's unique now.

On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.

@unstubbable
unstubbable merged commit 5e9eedb into react:mainMar 12, 2026
236 checks passed
@unstubbable
unstubbable deleted the clear-initialized-module-reason branch March 12, 2026 18:17
@nextjs-botnextjs-bot mentioned this pull request Mar 12, 2026
Merged
github-actionsBot pushed a commit to code/lib-react that referenced this pull request Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte mentioned this pull request Jun 5, 2026
Closed
Sign up for freeto join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees

No one assigned

Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
[Flight] Clear chunk reason after successful module initialization by unstubbable · Pull Request #36024 · react/react · GitHub
Skip to content
[Flight] Clear chunk reason after successful module initialization - #36024
Merged
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Mar 12, 2026
Merged
[Flight] Clear chunk reason after successful module initialization#36024
unstubbable merged 2 commits into
react:mainfrom 
unstubbable:clear-initialized-module-reason
Conversation
@unstubbable
@unstubbableunstubbable
commented
Mar 12, 2026

Copy link


Copy Markdown

Collaborator
When requireModule triggers a reentrant readChunk on the same module chunk, the reentrant call can fail and set chunk.reason to an error. After the outer requireModule succeeds, the chunk transitions to initialized but retains the stale error as reason.
When the Flight response stream later closes, it iterates all chunks and expects reason on initialized chunks to be a FlightStreamController. Since the stale reason is an Error object instead, calling chunk.reason.error() crashes with TypeError: chunk.reason.error is not a function.
The reentrancy can occur when module evaluation synchronously triggers readChunk on the same chunk — for example, when code called during evaluation tries to resolve the client reference for the module that is currently being initialized. In Fizz SSR, captureOwnerStack() can trigger this because it constructs component stacks that resolve lazy client references via readChunk. The reentrant requireModule call returns the module's namespace object, but since the module is still being evaluated, accessing the export binding throws a TDZ (Temporal Dead Zone) ReferenceError. This sets the chunk to the errored state, and the ReferenceError becomes the stale chunk.reason after the outer call succeeds.
This scenario is triggered in Next.js when a client module calls an instrumented API like Math.random() in module scope, which synchronously invokes captureOwnerStack().
@github-actionsgithub-actionsBot
added
the 
React Core Team
Opened by a member of the React Core Team
label
Mar 12, 2026
@react-sizebot
react-sizebot
commented
Mar 12, 2026•

edited

Loading

Copy link


Copy Markdown

Comparing: 7b5b561...b43ee2a
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=611.79 kB611.79 kB=108.12 kB108.12 kB
oss-experimental/react-dom/cjs/react-dom.production.js=6.84 kB6.84 kB=1.88 kB1.88 kB
oss-experimental/react-dom/cjs/react-dom-client.production.js=677.72 kB677.72 kB=119.08 kB119.08 kB
facebook-www/ReactDOM-prod.classic.js=697.67 kB697.67 kB=122.58 kB122.58 kB
facebook-www/ReactDOM-prod.modern.js=687.98 kB687.98 kB=120.96 kB120.96 kB
Significant size changes
Includes any change greater than 0.2%:
(No significant changes)

Generated by 🚫 dangerJS against b43ee2a
@unstubbable
[Flight] Clear chunk reason after successful module initialization
bc64684
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with
`TypeError: chunk.reason.error is not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal Dead
Zone) `ReferenceError`. This sets the chunk to the errored state, and the
`ReferenceError` becomes the stale `chunk.reason` after the outer call
succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
@unstubbable
unstubbableforce-pushed
the
clear-initialized-module-reason
branch
from
523741a to
bc64684CompareMarch 12, 2026 13:22
@unstubbable
unstubbable
marked this pull request as ready for review
March 12, 2026 13:28
eps1lon
eps1lon
reviewed
Mar 12, 2026
View reviewed changes
@eps1loneps1lon
left a comment


Copy link


Copy Markdown

Collaborator
Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There's only one place left where we don't set the reason field after changing status: https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-client/src/ReactFlightClient.js#L1075-L1079
What's the reason we're not doing it there? Worth adding a comment since it's unique now.
On the Reply side, https://github.com/facebook/react/blob/3bc2d414287e62a7b74731c6c7b837270353a339/packages/react-server/src/ReactFlightReplyServer.js#L476-L481 is left.
@unstubbable
unstubbable
merged commit 5e9eedb
into
react:mainMar 12, 2026

236 checks passed

@unstubbable
unstubbable
deleted the

clear-initialized-module-reason

branch
March 12, 2026 18:17
@nextjs-botnextjs-bot
mentioned this pull request
Mar 12, 2026
 Merged

github-actionsBot
pushed a commit
to code/lib-react
that referenced
this pull request
Mar 15, 2026
@pull
[Flight] Clear chunk reason after successful module initialization (r…
b4569e1
…eact#36024)
When `requireModule` triggers a reentrant `readChunk` on the same module
chunk, the reentrant call can fail and set `chunk.reason` to an error.
After the outer `requireModule` succeeds, the chunk transitions to
initialized but retains the stale error as `reason`.
When the Flight response stream later closes, it iterates all chunks and
expects `reason` on initialized chunks to be a `FlightStreamController`.
Since the stale `reason` is an `Error` object instead, calling
`chunk.reason.error()` crashes with `TypeError: chunk.reason.error is
not a function`.
The reentrancy can occur when module evaluation synchronously triggers
`readChunk` on the same chunk — for example, when code called during
evaluation tries to resolve the client reference for the module that is
currently being initialized. In Fizz SSR, `captureOwnerStack()` can
trigger this because it constructs component stacks that resolve lazy
client references via `readChunk`. The reentrant `requireModule` call
returns the module's namespace object, but since the module is still
being evaluated, accessing the export binding throws a TDZ (Temporal
Dead Zone) `ReferenceError`. This sets the chunk to the errored state,
and the `ReferenceError` becomes the stale `chunk.reason` after the
outer call succeeds.
This scenario is triggered in Next.js when a client module calls an
instrumented API like `Math.random()` in module scope, which
synchronously invokes `captureOwnerStack()`.
DiffTrain build for [5e9eedb](react@5e9eedb)
@rubennorterubennorte
mentioned this pull request
Jun 5, 2026
 Closed

Sign up for freeto join this conversation on GitHub.
Already have an account?
Sign in to comment

Reviewers

@eps1loneps1loneps1lon approved these changes

Assignees


No one assigned


Labels

CLA SignedReact Core TeamOpened by a member of the React Core Team

Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@unstubbable@react-sizebot@eps1lon