[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14

Open
hbrooks wants to merge 1 commit into
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demo/pr-36478
Open

[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
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@hbrookshbrooks commented May 28, 2026

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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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@hbrooks
, '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
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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, '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
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

Copy link


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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Sign up for freeto join this conversation on GitHub.
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1 participant

@hbrooks

, '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('^' + ".*" + '

Skip to content
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

Copy link


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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Sign up for freeto join this conversation on GitHub.
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@hbrooks

, '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
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

Copy link


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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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1 participant

@hbrooks

, '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
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

Copy link


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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Sign up for freeto join this conversation on GitHub.
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1 participant

@hbrooks

, '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
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
Open
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Open
[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
hbrooks wants to merge 1 commit into
mainfrom 
demo/pr-36478
Conversation
@hbrooks
@hbrookshbrooks
commented
May 28, 2026

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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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, '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); }
})();
})();

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[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375) - #14
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[DevTools] Fix double-REMOVE crash when Activity hidden children are inside a suspended Subtree (#36315, #36375)#14
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unknown@claudeunknown
[DevTools] Fix double-REMOVE crash when Activity hidden children are …
01c8a88
…inside a suspended Subtree (react#36315, react#36375)
The error "Cannot remove node X because no matching node was found in the
Store" was introduced by the Activity hidden-subtree feature (ed69815),
which made Activity's hidden children visible in the DevTools Store.
## Root cause
When a Suspense boundary suspends, `disconnectChildrenRecursively` walks the
DevTools instance tree and sends TREE_OPERATION_REMOVE for every visible node
— including children of hidden Activity components, which are now tracked in
the Store. The backend FiberInstances remain alive (React keeps the fiber tree
for the suspended content), so their IDs are still in `idToDevToolsInstanceMap`.
Later, if one of those children is removed from the React tree while the
Suspense is still suspended, `unmountRemainingChildren()` is called from
inside `updateFiberRecursively`'s `finally` block. At that point the
`isInDisconnectedSubtree` module-level flag has already been restored to
`false` by an inner try/finally, and the Activity's Offscreen fiber does not
satisfy `isSuspendedOffscreen()` (its parent is ActivityComponent, not
SuspenseComponent), so `unmountRemainingChildren` takes the unguarded else
branch and calls `recordDisconnect` again for the same instance — sending a
second TREE_OPERATION_REMOVE for a node that is no longer in `_idToElement`.
## Fix
Add a per-instance `isDisconnected` boolean to `FiberInstance` and
`VirtualInstance` (initialized to `false`). This acts as a second, stateful
guard independent of the global `isInDisconnectedSubtree` flag:
- `recordDisconnect` / `recordVirtualDisconnect`: return early if
`instance.isDisconnected` is already `true`; set it to `true` before
pushing to `pendingRealUnmountedIDs`.
- `recordReconnect` / `recordVirtualReconnect`: reset `isDisconnected` to
`false` so that the normal suspend → reveal → suspend cycle continues to
work correctly.
The per-instance flag prevents any double-REMOVE regardless of which code
path causes `recordDisconnect` to be called a second time, making the fix
robust against future interactions with complex Suspense / Activity trees.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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@hbrooks