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Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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Merged
felixweinberger merged 7 commits into from
Jul 27, 2026
Merged

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) #2547

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14b0b5f
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport
felixweinberger Jul 24, 2026
8a88ab7
Handle response delivery races in Streamable HTTP send()
felixweinberger Jul 24, 2026
0f4fb37
Align keep-alive implementation with the main branch
felixweinberger Jul 27, 2026
3158d15
Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle
felixweinberger Jul 27, 2026
56cf4c1
Gate the replay hand-off in send() on a delivered cursor
felixweinberger Jul 27, 2026
0bd3cab
Release re-created correlations when a response completes after close
felixweinberger Jul 27, 2026
0f983d0
Make close() idempotent
felixweinberger Jul 27, 2026
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8 changes: 8 additions & 0 deletions .changeset/sse-keepalive-timer-lifecycle.md
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@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.
15 changes: 15 additions & 0 deletions src/server/sseKeepAlive.ts
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
if (!Number.isFinite(intervalMs) || intervalMs < 1) {
return undefined;
}

const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
(timer as { unref?: () => void }).unref?.();
return timer;
}
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if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
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observer.observe(document.body, { childList: true, subtree: true });
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try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
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Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

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Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
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.markdown-body img { background: #0d1117; }
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.markdown-body hr { border-color: #30363d; }
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Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

from

Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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observer.observe(document.body, { childList: true, subtree: true });
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} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

from

Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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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);
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var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
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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 SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

from

Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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, '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 SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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felixweinberger
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Jul 27, 2026
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Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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// Remove or un-stick sticky/fixed headers that block content
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function unstick() {
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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';
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observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
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var __re = new RegExp('^' + ".*" + '
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

from

Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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.changeset/sse-keepalive-timer-lifecycle.md

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
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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 SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x) by felixweinberger · Pull Request #2547 · modelcontextprotocol/typescript-sdk · GitHub
Skip to content
Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)#2547

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 Merged

felixweinberger
merged 7 commits into

from

Jul 27, 2026
 Merged


Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport (v1.x)
#2547
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7 commits


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14b0b5f

Fix SSE keep-alive timer lifecycle in Streamable HTTP server transport


felixweinberger Jul 24, 2026
8a88ab7

Handle response delivery races in Streamable HTTP send()


felixweinberger Jul 24, 2026
0f4fb37

Align keep-alive implementation with the main branch


felixweinberger Jul 27, 2026
3158d15

Merge branch 'v1.x' into fweinberger/sse-keepalive-lifecycle


felixweinberger Jul 27, 2026
56cf4c1

Gate the replay hand-off in send() on a delivered cursor


felixweinberger Jul 27, 2026
0bd3cab

Release re-created correlations when a response completes after close


felixweinberger Jul 27, 2026
0f983d0

Make close() idempotent


felixweinberger Jul 27, 2026

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8 changes: 8 additions & 0 deletions
.changeset/sse-keepalive-timer-lifecycle.md

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,8 @@
---
'@modelcontextprotocol/sdk': patch
---

Fix SSE keep-alive timer lifecycle in the Streamable HTTP server transport. Keep-alive timers are now owned by the stream they were armed for, so a stale disconnect arriving after a reconnect no longer stops the live stream's keep-alive, a resume closes the superseded stream
cleanly, and a failed priming-event write no longer leaves a timer running or a stale request correlation behind. A resume that completes after the transport closed now gets a 404 instead of a silent stream nothing will ever write to. Non-finite `keepAliveMs` values now disable
keep-alive, and values above 2^31-1 are clamped instead of firing every millisecond. With an event store configured, a response completing while its request stream is disconnected is now stored for `Last-Event-ID` replay and its request correlations released when the client can
resume the stream, instead of `send()` rejecting; for clients that cannot resume (no priming event), `send()` still rejects so the failure surfaces. Replays no longer double-deliver events written concurrently with a resume, and requests racing transport close now receive a 404.

15 changes: 15 additions & 0 deletions
src/server/sseKeepAlive.ts

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
/** Default interval between SSE keep-alive comment frames. */
export const DEFAULT_SSE_KEEP_ALIVE_MS = 15_000;

const MAX_TIMER_DELAY_MS = 2 ** 31 - 1;

/** Arms an unref'd timer, or disables keep-alive for invalid delays. */
export function armSseKeepAlive(intervalMs: number, onTick: () => void): ReturnType<typeof setInterval> | undefined {
 if (!Number.isFinite(intervalMs) || intervalMs < 1) {
 return undefined;
 }

 const timer = setInterval(onTick, Math.min(intervalMs, MAX_TIMER_DELAY_MS));
 (timer as { unref?: () => void }).unref?.();
 return timer;
}
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