fix(tracing)!: require the gen_ai. prefix in the default span filter

[hassiebp]

What does this PR do?

is_genai_span (used by the default should_export_span filter) matched any attribute key starting with gen_ai. Lookalikes such as gen_ai_custom, gen_ai-request.model or gen_airflow.model therefore exported unrelated third-party spans. It now matches only the gen_ai.* namespace.

This is the change from #1924 (by @fallintoplace), landed on the v5 branch because it narrows what the default filter exports.

Stack: independent. Base: prepare-v5-release. It touches only langfuse/_client/span_filter.py and tests/unit/test_span_filter.py, so it can merge at any point.

Type of change

• Bug fix
• New feature
• Breaking change
• Refactor
• Documentation update
• Tooling, CI, or repo maintenance

Verification

uv run --frozen ruff check .                       # All checks passed!
uv run --frozen mypy langfuse --no-error-summary   # clean
uv run --frozen pytest -q tests/unit/test_span_filter.py  # 62 passed
uv run --frozen pytest -n auto tests/unit          # 736 passed, 2 skipped

Checklist

• I self-reviewed the diff using code_review.md.
• I added or updated tests for behavior changes.
• I updated docs, examples, or .env.template if needed.
• I did not hand-edit generated files; if generated files changed, I used the upstream regeneration path.
• I did not commit secrets or credentials.

  

Confidence Score: 5/5

The PR appears safe to merge; no actionable regression was identified.

Summary

The PR narrows default GenAI span selection to attributes in the gen_ai.* namespace and adds cases for lookalike keys and valid namespace keys.

_{Reviews (1) · Last reviewed commit: "fix(tracing)!: require the gen_ai. prefi..."}

[github-actions]

@claude review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-06T14:31:33.502560Z	8ef341c	PR opened

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[claude]

Claude Code Review

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[claude]

Looks good, a correct one-line namespace-boundary fix with solid test coverage.

Extended reasoning...

The change is a single-character fix in is_genai_span (langfuse/_client/span_filter.py), changing the prefix check from "gen_ai" to "gen_ai." so lookalike attribute keys like gen_ai_custom or gen_airflow.model no longer falsely match; it mirrors the existing _matches_scope_prefix boundary pattern already used in the same file. No security-sensitive surface (auth, crypto, injection) is touched—this only affects which spans are exported by default. The accompanying test additions in tests/unit/test_span_filter.py are thorough, covering matching and lookalike keys, non-string/bytes keys, and empty attributes, for both is_genai_span and is_default_export_span. The change is small, self-contained, and mechanically verified against the code.