feat(llmobs): add source:otel tag to evaluations when DD_TRACE_OTEL_ENABLED is set

[ZStriker19]

Description

Auto-add source:otel tag to LLMObs evaluations when OTel tracing is enabled.

When DD_TRACE_OTEL_ENABLED=true, automatically adds source:otel tag to all submitted evaluations. This allows the backend to wait ~3 minutes for OTel span conversion before discarding unmatched evaluations.

Related: DataDog/dd-trace-py#15538

Changes

• Add source:otel tag in submitEvaluation() when DD_TRACE_OTEL_ENABLED environment variable is set

Testing

Added unit tests:

• adds source:otel tag when DD_TRACE_OTEL_ENABLED is set
• does not add source:otel tag when DD_TRACE_OTEL_ENABLED is not set

Plugin Checklist

• Unit tests.
• Integration tests.
• Benchmarks.
• TypeScript definitions.
• TypeScript tests.
• API documentation.
• CI jobs/workflows.

Additional Notes

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 84.76%. Comparing base (a8ed0d8) to head (a72d4c8).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
packages/dd-trace/src/llmobs/sdk.js	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7113      +/-   ##
==========================================
- Coverage   84.78%   84.76%   -0.02%     
==========================================
  Files         521      521              
  Lines       22149    22151       +2     
==========================================
- Hits        18778    18776       -2     
- Misses       3371     3375       +4     

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[github-actions]

Overall package size

Self size: 4.34 MB
Deduped: 5.22 MB
No deduping: 5.22 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | import-in-the-middle | 1.15.0 | 127.66 kB | 856.24 kB | | dc-polyfill | 0.1.10 | 26.73 kB | 26.73 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[sabrenner]

just a couple nits!

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-12-16 20:34:43

Comparing candidate commit a72d4c8 in PR branch zachg/llmobs_evals_tag_for_ote with baseline commit a8ed0d8 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 291 metrics, 29 unstable metrics.