fix(core): Avoid propagating baggage: "undefined" when DSC is missing#22424
Merged
Conversation
![cursor[bot]](https://avatars.githubusercontent.com/in/1210556?s=60&v=4){kind=small}
There was a problem hiding this comment.
Cursor Bugbot has reviewed your changes and found 1 potential issue.
❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.
Reviewed by Cursor Bugbot for commit 48f895c. Configure here.
Contributor
size-limit report 📦
|
msonnb
approved these changes
Jul 21, 2026
msonnb
left a comment
msonnb
left a comment
Member
There was a problem hiding this comment.
'undefined' for undefined is indeed very interesting
Lms24
enabled auto-merge (squash)
July 21, 2026 14:53
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
So, TIL, when you make a
fetchrequest and pass in a headers object where a key could beundefined,this results in browsers (and possibly node) actually sending
baggage: "undefined"over the wire instead of dropping the header. Which is in accordance with the spec (whatwg/fetch#1260) but came as a surprise to me.I'm fairly sure this isn't a large problem but theoretically, downstream SDKs could interpret this as an incoming invalid baggage header, instead of an incoming request without a baggage header. Not sure if we make this differentiation in practise but I'd rather avoid propagating
"undefined"it in the first place.Background: This came up while testing that our SDK correctly handles the edge case where it receives an incoming
sentry-tracebut nobaggageheader (meta tag). In this case, the SDK should assume the upstream SDK is not compatible with dynamic sampling and continue the trace with a frozen, empty DSC (hence not propagate it further).This is specified in our DSC trace continuation algorithm: https://develop.sentry.dev/sdk/foundations/trace-propagation/dynamic-sampling-context/#unified-propagation-mechanism