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fix(server): fire onsessionclosed once when DELETEs overlap #2583

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5 changes: 5 additions & 0 deletions .changeset/delete-race-onsessionclosed.md
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Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.
14 changes: 13 additions & 1 deletion packages/server/src/server/streamableHttp.ts
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Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
private sessionIdGenerator: (() => string) | undefined;
private _started: boolean = false;
private _closed: boolean = false;
/**
* Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
* callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
* by `close()`, which only runs once the callback has already settled.
*/
private _sessionClosedNotified: boolean = false;
private _streamMapping: Map<string, StreamMapping> = new Map();
private _requestToStreamMapping: Map<RequestId, string> = new Map();
private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
}

try {
await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
// Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
// idempotent: a concurrent or repeat request still terminates the session and answers 200,
// it just does not re-run the callback.
if (!this._sessionClosedNotified) {
this._sessionClosedNotified = true;
await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
}
return new Response(null, { status: 200 });
} finally {
await this.close();
Expand Down
30 changes: 30 additions & 0 deletions packages/server/test/server/streamableHttp.test.ts
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Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

expect(onClosed).toHaveBeenCalledWith('test-session-456');
});

it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
// The first DELETE parks on the callback await; `_closed` is only set by close() in the
// finally, so a second DELETE passes the same guards and fires the callback again for a
// session that is already being torn down.
let releaseCallback!: () => void;
const callbackGate = new Promise<void>(resolve => {
releaseCallback = resolve;
});
const onClosed = vi.fn().mockReturnValue(callbackGate);

const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
const transport = new WebStandardStreamableHTTPServerTransport({
sessionIdGenerator: () => 'test-session-789',
onsessionclosed: onClosed
});

await mcpServer.connect(transport);
await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

const sendDelete = (): Promise<Response> =>
transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

const first = sendDelete();
const second = sendDelete();
releaseCallback();
await Promise.all([first, second]);

expect(onClosed).toHaveBeenCalledTimes(1);
});
});

describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading
, '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" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
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fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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('^' + ".*" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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('^' + ".*" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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('^' + ".*" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
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fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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('^' + ".*" + '
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix(server): fire onsessionclosed once when DELETEs overlap#2583

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading

, '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); }
})();
})();
fix(server): fire onsessionclosed once when DELETEs overlap by axits-lab · Pull Request #2583 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
fix(server): fire onsessionclosed once when DELETEs overlap#2583

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fix(server): fire onsessionclosed once when DELETEs overlap
#2583
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5 changes: 5 additions & 0 deletions
.changeset/delete-race-onsessionclosed.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/server': patch
---

Fire `onsessionclosed` at most once when DELETE requests for the same session overlap. The first DELETE awaited the callback before `close()` ran, so `_closed` was still `false` and a second DELETE passed the same guards and invoked the callback again for a session already being torn down. The notification is now claimed synchronously before the await. DELETE remains idempotent — a concurrent or repeat request still terminates the session and answers 200.

14 changes: 13 additions & 1 deletion
packages/server/src/server/streamableHttp.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -241,6 +241,12 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 private sessionIdGenerator: (() => string) | undefined;
 private _started: boolean = false;
 private _closed: boolean = false;
 /**
 * Set synchronously before `onsessionclosed` is awaited, so a DELETE that arrives while the
 * callback is in flight does not fire it again. `_closed` cannot serve this purpose: it is set
 * by `close()`, which only runs once the callback has already settled.
 */
 private _sessionClosedNotified: boolean = false;
 private _streamMapping: Map<string, StreamMapping> = new Map();
 private _requestToStreamMapping: Map<RequestId, string> = new Map();
 private _requestResponseMap: Map<RequestId, JSONRPCMessage> = new Map();
Expand DownExpand Up@@ -984,7 +990,13 @@ export class WebStandardStreamableHTTPServerTransport implements Transport {
 }

 try {
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 // Claim the notification before awaiting it — see `_sessionClosedNotified`. DELETE stays
 // idempotent: a concurrent or repeat request still terminates the session and answers 200,
 // it just does not re-run the callback.
 if (!this._sessionClosedNotified) {
 this._sessionClosedNotified = true;
 await Promise.resolve(this._onsessionclosed?.(this.sessionId!));
 }
 return new Response(null, { status: 200 });
 } finally {
 await this.close();
Expand Down

30 changes: 30 additions & 0 deletions
packages/server/test/server/streamableHttp.test.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -602,6 +602,36 @@ describe('Zod v4', () => {

 expect(onClosed).toHaveBeenCalledWith('test-session-456');
 });

 it('fires onsessionclosed once when two DELETEs arrive concurrently', async () => {
 // The first DELETE parks on the callback await; `_closed` is only set by close() in the
 // finally, so a second DELETE passes the same guards and fires the callback again for a
 // session that is already being torn down.
 let releaseCallback!: () => void;
 const callbackGate = new Promise<void>(resolve => {
 releaseCallback = resolve;
 });
 const onClosed = vi.fn().mockReturnValue(callbackGate);

 const mcpServer = new McpServer({ name: 'test-server', version: '1.0.0' }, { capabilities: {} });
 const transport = new WebStandardStreamableHTTPServerTransport({
 sessionIdGenerator: () => 'test-session-789',
 onsessionclosed: onClosed
 });

 await mcpServer.connect(transport);
 await transport.handleRequest(createRequest('POST', TEST_MESSAGES.initialize));

 const sendDelete = (): Promise<Response> =>
 transport.handleRequest(createRequest('DELETE', undefined, { sessionId: 'test-session-789' }));

 const first = sendDelete();
 const second = sendDelete();
 releaseCallback();
 await Promise.all([first, second]);

 expect(onClosed).toHaveBeenCalledTimes(1);
 });
 });

 describe('HTTPServerTransport - Event Store (Resumability)', () => {
Expand Down
Loading