Telemetry is delayed or lost when Vercel suspends a Node.js function after the response

Is there an existing issue for this?

I have checked for existing issues https://github.com/getsentry/sentry-javascript/issues
I have reviewed the documentation https://docs.sentry.io/
I am using the latest SDK release https://github.com/getsentry/sentry-javascript/releases

How do you use Sentry?

Sentry Saas (sentry.io)

Which SDK are you using?

@sentry/nextjs

SDK Version

11.1.0

Framework Version

Seen with Next.js 16 on the Vercel Node.js runtime. The cause is not specific to Next.js.

Link to Sentry event

No response

Reproduction Example/SDK Setup

Default server setup:

Sentry.init({
  dsn: '...',
  tracesSampleRate: 1,
});

Steps to Reproduce

Deploy an app that uses the Node.js SDK to Vercel, on the Node.js runtime.
Send one request.
Send no more requests, so the function goes idle.
Look for the request's telemetry in Sentry.

Expected Result

All telemetry of the request (spans, logs, metrics, errors) arrives shortly after the response.

Actual Result

Telemetry that was still buffered when the response was sent arrives late or never. It is sent only when a later request wakes the same instance. With span streaming, the root span of the last request is often missing and its child spans show up without a parent.

Additional Context

Vercel can suspend a function as soon as it sends the response. The SDK sends buffered telemetry on timers or on SIGTERM, and neither runs while the function is suspended.

Vercel provides waitUntil through Symbol.for('@vercel/request-context') on the Node.js runtime, but the SDK uses it only on the Edge runtime.

Fix: #24910. Related: #23087.

JS-3859

Wondering if this just concerns span streaming or also logs, metrics or anything else that doesn't send immediately. Or IOW where we should actually make that flush call.

fix(node): Flush telemetry before Vercel functions are suspended

@Lms24

@Lms24 thank you for encouraging to look at it holistically, updated the context, let me know if anything is unclear

thx, left a quick review but need more eyes on the fix. Nice idea with the diagnostic channel!

fix(node): Flush telemetry before Vercel functions are suspended (get…

A PR closing this issue has just been released 🚀

This issue was referenced by PR #24910, which was included in the 11.5.0 release.

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Telemetry is delayed or lost when Vercel suspends a Node.js function after the response #24909

Is there an existing issue for this?

How do you use Sentry?

Which SDK are you using?

SDK Version

Framework Version

Link to Sentry event

Reproduction Example/SDK Setup

Steps to Reproduce

Expected Result

Actual Result

Additional Context

A PR closing this issue has just been released 🚀

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Telemetry is delayed or lost when Vercel suspends a Node.js function after the response #24909

Description

Is there an existing issue for this?

How do you use Sentry?

Which SDK are you using?

SDK Version

Framework Version

Link to Sentry event

Reproduction Example/SDK Setup

Steps to Reproduce

Expected Result

Actual Result

Additional Context

Activity

linear-code commented on Sep 30, 2026

Lms24 commented on Oct 1, 2026

sergical commented on Oct 1, 2026

Lms24 commented on Oct 2, 2026

github-actions commented on Oct 7, 2026

A PR closing this issue has just been released 🚀

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