Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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, '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" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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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('^' + ".*" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms"); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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, '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" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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, '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('^' + ".*" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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, '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('^' + ".*" + '
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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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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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Cloudflare Workflow teardown can deadlock on instrumented waitUntil #23005

Description

@matthew-gizmo

Environment

  • @sentry/cloudflare 10.69.0
  • Cloudflare Workflows

Problem

instrumentWorkflowWithSentry captures context.waitUntil.bind(context) inside each run() call. init() instruments that same context. When Cloudflare reuses a Workflow instance, a later run can therefore capture Sentry’s flush-lock-aware waitUntil wrapper instead of the original function.

At the end of that run, the wrapper schedules flushAndDispose(client) through the captured function. This can register the teardown promise in the same flush lock that client.flush() is waiting to drain, so teardown never settles. In production this surfaced as Worker code had hung immediately after otherwise successful workflow completion.

Application work registered through the instrumented waitUntil should remain tracked; only Sentry’s own teardown must bypass its instrumentation.

Suggested fix

Capture the original function before client initialization, matching the existing RPC wrapper:

constwaitUntil=getOriginalWaitUntil(context).bind(context);constclient=init({ ...options,ctx: context,enableDedupe: false});

The CommonJS build can use the corresponding flush.getOriginalWaitUntil(context) export.

Regression shape

A regression test can reuse one instrumented Workflow instance for two runs. During the second run, register controlled pending application work through the instrumented context, return successfully, then release that work and await both the application and teardown promises. With the current implementation the teardown promise remains pending; using getOriginalWaitUntil lets both settle while genuine workflow errors still propagate.

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Issue actions