MCP server aint recording events - req/res transport issue #19233

Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js

Description

@gotenxds
gotenxds
opened on Feb 2, 2026

Is there an existing issue for this?

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/node

SDK Version

10.34.0

Framework Version

No response

Link to Sentry event

No response

Reproduction Example/SDK Setup

Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.

The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.

The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method

Here you can see images of both events for the same mcp call:

onMessage:
Image

onSend:
Image

As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)

This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.

Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.

A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.

Steps to Reproduce

As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)

Expected Result

Events to be sent to sentry

Actual Result

Events are not being sent

Additional Context

No response

Priority

React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.

Activity

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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" + '

Skip to content
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
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Issue actions

, '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
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
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BugNode.js
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Milestone
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Relationships
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Issue actions

, '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
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
Assignees
Labels
BugNode.js
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, '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
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
Assignees
Labels
BugNode.js
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, '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
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
Assignees
Labels
BugNode.js
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, '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
MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
Assignees
betegon
Labels
BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
Assignees
Labels
BugNode.js
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions

, '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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MCP server aint recording events - req/res transport issue #19233
Closed
#19172
Closed
MCP server aint recording events - req/res transport issue#19233
#19172
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betegon
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BugNode.js
Description
@gotenxds
gotenxds
opened on Feb 2, 2026
Is there an existing issue for this?
How do you use Sentry?
Sentry Saas (sentry.io)
Which SDK are you using?
@sentry/node
SDK Version
10.34.0
Framework Version
No response
Link to Sentry event
No response
Reproduction Example/SDK Setup
Hello, I've been debugging this issue for a few days I think I understand why it happens, here is what I found.
The sentryMcpWrapper is storing the sessions in a weakmap from the transport to the session data.
The issue is, that the transport received in the onMessage method can be a different level of abstraction from the one recived in the send method
Here you can see images of both events for the same mcp call:
onMessage:
Image
onSend:
Image
As you can see in the images above, this is the same request, but on response (send) the sdk exposes a different transport (a warpper that holds the original transport)
This happens because the send method is being called from a StreamableHTTPServerTransport which overrides the method, but it does not override the onMessage method so that one is being called from the super class which means the code is getting different this values in each invocation.
Because the weakmap uses the class of the transport itself as the key for the entire transaction this causes the event to not be found and not send to sentry.
A solution might be trying to use the prototype class or just forgo using classes at all there and trying to use the session id generated by the transport but I dont know all the details and I'm sure there was a good reason for this approach.
Steps to Reproduce
As far as I see this happens always if you create your own StreamableHTTPServerTransport and use mcpServer.connect(transport)
Expected Result
Events to be sent to sentry
Actual Result
Events are not being sent
Additional Context
No response
Priority
React with 👍 to help prioritize this issue. Please use comments to provide useful context, avoiding +1 or me too, to help us triage it.
Activity
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