NextJS Pages API Route traces are not continued from incoming trace

[Lms24]

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

8.46.0

Framework Version

NextJS 15.1.1

Link to Sentry event

N/A

Reproduction Example/SDK Setup

Clone my repro: https://github.com/Lms24/nextjs-trace-envelope-header

Steps to Reproduce

To reproduce:

1. npm install
2. npm run build && npm run start
3. sh req.sh

Observe that trace_id, sample_rate and transaction fields (+others) are not continued from incoming trace (see req.sh). Meaning, it seems like the NextJS SDK starts a new trace for the server-side instead of continuing the passed trace via the headers.

Expected Result

• The SDK continues the incoming trace, freezes the DSC values passed in via baggage
• When sending its transaction event, the SDK puts the frozen DSC values into the trace envelope header and sends the continued trace data in event.context.trace

Actual Result

• The SDK doesn't continue the incoming trace but seems to start a new trace
• When sending its transaction event, SDK populates the DSC from the new trace and sends the new trace

Additional information

The logs suggest that there might be 2 ongoing root spans which possibly(?) conflict with each other?

Sentry Logger [log]: [Tracing] Inheriting remote parent's sampled decision for GET /api/test: true
Sentry Logger [log]: [Tracing] Starting sampled root span
  op: < unknown op >
  name: GET /api/test
  ID: 6d6d1a6095cd996c
  parent ID: 9a124d0d6c081115
Sentry Logger [log]: [Tracing] Inheriting parent's sampled decision for executing api route (pages) /api/test: true
Sentry Logger [log]: [Tracing] Starting sampled span
  op: < unknown op >
  name: executing api route (pages) /api/test
  ID: 134e7d6841094ac1
  parent ID: 6d6d1a6095cd996c
  root ID: 6d6d1a6095cd996c
  root description: GET /api/test
Sentry Logger [info]: Starting a new trace with id 1f225918b9444512867b7f0fed977fa5
Sentry Logger [log]: [Tracing] Starting sampled root span
  op: http.server
  name: GET /api/test
  ID: dfd3fc2e5a4b4818
Sentry Logger [log]: [Tracing] Finishing "http.server" root span "GET /api/test" with ID dfd3fc2e5a4b4818
Sentry Logger [log]: Flushing events...
Sentry Logger [log]: SpanExporter exported 1 spans, 0 spans are waiting for their parent spans to finish
Sentry Logger [log]: Flushing outcomes...
Sentry Logger [log]: No outcomes to send
Sentry Logger [log]: [Tracing] Finishing "< unknown op >" span "executing api route (pages) /api/test" with ID 134e7d6841094ac1
Sentry Logger [log]: [Tracing] Finishing "< unknown op >" root span "GET /api/test" with ID 6d6d1a6095cd996c
Sentry Logger [log]: SpanExporter exported 2 spans, 0 spans are waiting for their parent spans to finish
event trace context: {
  span_id: 'dfd3fc2e5a4b4818',
  trace_id: '2f656955b869439a0f839731c22cc4eb',
  data: {
    'sentry.source': 'route',
    'sentry.sample_rate': 0.99,
    'sentry.op': 'http.server',
    'sentry.origin': 'auto.http.nextjs',
    'http.response.status_code': 200
  },
  origin: 'auto.http.nextjs',
  op: 'http.server',
  status: 'ok'
}
{
  envelopeTraceHeader: {
    environment: 'production',
    release: '0UzErXa-sfDtF-53wmU7x',
    public_key: 'c64221a14c2b788162c7b81c2f94d65e',
    trace_id: '2f656955b869439a0f839731c22cc4eb',
    sample_rate: '0.99',
    transaction: 'GET /api/test',
    sampled: 'true'
  }
}
Sentry Logger [log]: Event processor "NextLowQualityTransactionsFilter" dropped event
Sentry Logger [log]: Recording outcome: "event_processor:transaction"
Sentry Logger [log]: An event processor returned `null`, will not send event.
Sentry Logger [log]: Done flushing events

[chargome]

was likely introduced in #14481

Downgrading the version in the repro to 8.42.0 fixes the issue.

[Lms24]

Related: #14803

Update: These issues are probably not related after all

[mydea]

Wait, I found the problem! I will open a PR to fix this 😬 We are using continueTrace from @sentry/core there, but we have to use the one from @sentry/opentelemetry. This sucks, we should probably put this on the ACS...

[lforst]

@mydea Additional thing to consider, we cannot use the opentelemetry continueTrace() there because this is runtime agnostic code. We actually kinda need it to be on the acs I think.