fix(client): replace body.cancel() with text() to prevent hanging - #1320

Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged

fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom
grimmerk:fix/replace-body-cancel-with-text-consume

Conversation

@grimmerk

@grimmerkgrimmerk commented Dec 19, 2025•
edited
Loading

Copy link
Copy Markdown
Contributor

Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.

Motivation and Context

PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).

The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.

Using text().catch(() => {}) instead:

  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()

In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.

This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.

How Has This Been Tested?

  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly

Breaking Changes

None. Drop-in replacement that maintains the same behavior.

Types of changes

  • Bug fix (non-breaking change which fixes an issue)

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling

Additional context

Fixes regression introduced in #1173 and #1214.

References:

@grimmerk
grimmerk requested a review from a team as a code ownerDecember 19, 2025 18:06
@changeset-bot

changeset-botBot commented Dec 19, 2025•
edited
Loading

Copy link
Copy Markdown

⚠️ No Changeset found

Latest commit: c7aa35e

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

mattzcarey
mattzcarey previously approved these changes Dec 19, 2025
View reviewed changes

@mattzcareymattzcarey left a comment

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

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

LGTM

@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed the fix/replace-body-cancel-with-text-consume branch from c131704 to 358910dCompareDecember 19, 2025 18:13
@mattzcarey

mattzcarey commented Dec 19, 2025

Copy link
Copy Markdown
Contributor

Tests are failing here, reckon you could have a look

@pkg-pr-new

pkg-pr-newBot commented Dec 19, 2025•
edited
Loading

Copy link
Copy Markdown

Open in StackBlitz

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e

@grimmerk

grimmerk commented Dec 19, 2025

Copy link
Copy Markdown
ContributorAuthor

@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.

@grimmerk

grimmerk commented Jan 9, 2026

Copy link
Copy Markdown
ContributorAuthor

Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.

@mattzcarey
mattzcarey merged commit 09a658b into modelcontextprotocol:mainJan 9, 2026
7 checks passed
@mattzcareymattzcarey mentioned this pull request Jan 9, 2026
Merged
9 tasks
mozmo15 pushed a commit to mozmo15/typescript-sdk that referenced this pull request Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18 mentioned this pull request Apr 14, 2026
Open
Sign up for freeto join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees

No one assigned

Labels

None yet

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov
, '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" + '

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

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

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

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

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

, '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" + '

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

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

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

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

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov

, '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); }
})();
})();

Skip to content
fix(client): replace body.cancel() with text() to prevent hanging - #1320
Merged
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Jan 9, 2026
Merged
fix(client): replace body.cancel() with text() to prevent hanging#1320
mattzcarey merged 4 commits into
modelcontextprotocol:mainfrom 
grimmerk:fix/replace-body-cancel-with-text-consume
Conversation
@grimmerk
@grimmerkgrimmerk
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Contributor
Replace response.body.cancel() with response.text().catch(() => {}) in client package to prevent indefinite hanging with certain server responses.
Motivation and Context
PRs #1173 and #1214 added body.cancel() calls to fix connection leaks in Cloudflare Workers. However, body.cancel() can hang indefinitely with certain MCP servers (e.g., Sentry MCP during OAuth metadata discovery).
The hang occurs because cancel() attempts to abort the stream, which requires coordination with the server that doesn't always complete.
Using text().catch(() => {}) instead:
  • Always completes - just reads all data
  • Releases the connection - body is fully consumed
  • No stream coordination needed - more reliable than cancel()
In all affected code paths (OAuth metadata discovery, error responses, 202 Accepted, session termination), the response bodies are small, making text() a safe and efficient choice.
This preserves the original fix for Cloudflare Workers connection leaks while eliminating the hanging issue.
How Has This Been Tested?
  • Tested with Sentry MCP (https://mcp.sentry.dev/mcp) which previously hung indefinitely
  • After the fix, OAuth flow proceeds correctly
  • Verified Notion MCP still works correctly
Breaking Changes
None. Drop-in replacement that maintains the same behavior.
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
Additional context
Fixes regression introduced in #1173 and #1214.
References:
@grimmerk
grimmerk
requested a review
from a team
as a code ownerDecember 19, 2025 18:06
@changeset-bot
changeset-botBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

⚠️ No Changeset found
Latest commit: c7aa35e
Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.
This PR includes no changesets
When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types
Click here to learn what changesets are, and how to add one.
Click here if you're a maintainer who wants to add a changeset to this PR
mattzcarey
mattzcarey
previously approved these changes
Dec 19, 2025
View reviewed changes
@mattzcareymattzcarey
left a comment


Copy link


Copy Markdown

Contributor
Choose a reason for hiding this comment

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

LGTM
@grimmerk
fix(client): replace body.cancel() with text() to prevent hanging
358910d
body.cancel() can hang indefinitely with certain server responses
(e.g., Sentry MCP's OAuth flow). Using text?.().catch(() => {}) is safer:
- Always completes (reads all data)
- Releases connection (body consumed)
- No stream coordination needed
- Uses optional chaining for compatibility with mock responses
Fixes regression from modelcontextprotocol#1173 and modelcontextprotocol#1214.
@grimmerk
grimmerkforce-pushed
the
fix/replace-body-cancel-with-text-consume
branch
from
c131704 to
358910dCompareDecember 19, 2025 18:13
@mattzcarey
mattzcarey
commented
Dec 19, 2025

Copy link


Copy Markdown

Contributor
Tests are failing here, reckon you could have a look
@pkg-pr-new
pkg-pr-newBot
commented
Dec 19, 2025•

edited

Loading

Copy link


Copy Markdown

Open in StackBlitz
npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/client@1320

npm i https://pkg.pr.new/modelcontextprotocol/typescript-sdk/@modelcontextprotocol/server@1320

commit: c7aa35e
@grimmerk
grimmerk
commented
Dec 19, 2025

Copy link


Copy Markdown

ContributorAuthor
@mattzcarey thanks for the reminder. I've force-pushed it to fix the broken tests.
@grimmerk
grimmerk
commented
Jan 9, 2026

Copy link


Copy Markdown

ContributorAuthor
Hi! Happy new year 🎉 Just checking in — is there anything else needed from my side to get this merged? Happy to help if so.
@mattzcarey
mattzcarey
merged commit 09a658b
into
modelcontextprotocol:mainJan 9, 2026

7 checks passed

@mattzcareymattzcarey
mentioned this pull request
Jan 9, 2026
 Merged

9 tasks
mozmo15 pushed a commit
to mozmo15/typescript-sdk
that referenced
this pull request
Mar 30, 2026
@grimmerk@KKonstantinovmozmo15
fix(client): replace body.cancel() with text() to prevent hanging (mo…
915057f
…delcontextprotocol#1320)
Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>
@mddanishh18mddanishh18
mentioned this pull request
Apr 14, 2026
 Open

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

Reviewers

@mattzcareymattzcareymattzcarey approved these changes

Assignees


No one assigned


Labels


None yet


Projects


None yet


Milestone


No milestone


Development

Successfully merging this pull request may close these issues.

3 participants

@grimmerk@mattzcarey@KKonstantinov