[knowprasad]

Description

In opentelemetry.baggage.propagation.W3CBaggagePropagator.extract, the implementation extracted only the first element from getter.get(carrier, self._BAGGAGE_HEADER_NAME). When a carrier contains multiple �aggage header entries (for example, when using frameworks that return a list of headers or when multiple integrations such as Sentry and OpenTelemetry inject separate baggage headers), all entries after the first were discarded.

Per the W3C Baggage specification:

A server receiving multiple Baggage header fields MUST combine them into a single list by appending each in field value order, separated by a comma (,).

And RFC 9110 Section 5.3:

A recipient MAY combine multiple field lines within each field section that have the same field name by appending each subsequent field line value to the combined value in order, separated by a comma and optional whitespace.

This PR updates W3CBaggagePropagator.extract to:

1. Retrieve all header entries from getter.get(carrier, self._BAGGAGE_HEADER_NAME).
2. Combine multiple header strings by joining with commas , in field value order.
3. Add regression tests in est_w3cbaggagepropagator.py verifying multi-header extraction, comma-separated combinations, duplicate key handling (where later values win), and empty/whitespace entries.

Fixes #5811

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• Followed the style guidelines of this project
• Changelog entry added to .changelog/5814.fixed
• Added unit tests covering multiple baggage headers
• Signed-off-by commit added (DCO)

[opentelemetry-pr-dashboard]

Pull request dashboard status

Waiting on maintainers · refreshed 2026-10-26 20:57 UTC

Merge when ready.

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[pmcollins]

LGTM, thanks for the fix.

BTW, might want to look into the (harmless) extraneous characters in the PR description and how they got there. Code looks good though.

[herin049]

Fyi, I've opened #5823 which bundles together a number of fixes (including this one), so we should probably hold off on this for now. The new PR also addresses a gap in this implementation which is that ",".join(...) performs a full redundant re-allocation of all of the Baggage header content.

[knowprasad]

Thanks @pmcollins! Cleaned up the formatting in the PR description.

@herin049 thanks for linking #5823; happy to either land this targeted fix first or let #5823 supersede if maintainers prefer to merge the broader spec alignment as a single unit.

/dashboard route:reviewers