[Kielek]

Follow up to open-telemetry/opentelemetry-dotnet#8042

If we have agreement on open-telemetry/opentelemetry-dotnet#8042, this PR can land even now without releases in the upstream.

Changes was tested locally with local build and also with 1.20.1. All works as expected.

Changes

TelemetryHttpModule now saves the current Baggage value after each request
step, including when the step throws, and restores it when ASP.NET loses the
execution context. This preserves additions, updates, and clearing with the
isolated baggage writes proposed in
open-telemetry/opentelemetry-dotnet#8042.
Previously the module retained the request-start holder, which becomes stale
when writes replace that holder.

Restoration detaches any inherited holder before assigning Baggage.Current,
so older API versions also preserve the other execution context's baggage.
Trace-only propagation and completed requests retain their existing behavior.
The change uses existing APIs and works with the published API without a
dependency version bump.

Validation

• Added ten regressions covering updates, clearing, exceptional and repeated
  steps, other inherited contexts, trace-only propagation, and request completion.
• Before correction, the module suite with the proposed safe API had eight
  expected failures, including an existing regression.
• Both affected suites pass against published API 1.20.1 and the local core PR
  build with safe and legacy flow: 132 passed and 2 skipped per configuration.
• Release ASP.NET component build, formatting, Markdown lint, whitespace and
  source sanity checks pass. Formatting reports workspace-loading warnings.
• Tests exercise the managed callback with simulated context loss; no
  end-to-end IIS/native-thread-switch run is claimed.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, successful build/tests, etc.)
• Tests added/updated
• CHANGELOG.md file(s) updated for non-trivial changes
• Changes in public API reviewed (if applicable)
• AI usage disclosure:
  • No AI used
  • AI-assisted
  • Bulk AI-generated
• I have the experience and knowledge necessary to understand, review, and validate all content in this PR¹

Note

This PR description was assisted with OpenAI Codex.

Footnotes

1. Yes, I can answer maintainer questions about the content of this PR without using AI. ↩

[opentelemetry-pr-dashboard]

Pull request dashboard status

Waiting on maintainers · refreshed 2026-11-10 08:06 UTC

Merge when ready.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.76%. Comparing base (594d017) to head (e4a47fe).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5948   +/-   ##
=======================================
  Coverage   79.75%   79.76%           
=======================================
  Files         520      520           
  Lines       22786    22793    +7     
  Branches     3677     3678    +1     
=======================================
+ Hits        18174    18181    +7     
  Misses       3915     3915           
  Partials      697      697           

Flag	Coverage Δ
unittests-Instrumentation.AspNet	85.02% <100.00%> (+0.21%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ation.AspNet.TelemetryHttpModule/ActivityHelper.cs	91.66% <100.00%> (+0.49%)	⬆️
....AspNet.TelemetryHttpModule/TelemetryHttpModule.cs	60.00% <100.00%> (+2.85%)	⬆️

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