Pin PYTHONHASHSEED in the benchmark workflow

[benedikt-bartscher]

Python randomizes string hashing per process, so dict probe sequences differ between two runs of the same code. The instrumented benchmarks are sensitive enough to pick that up as a few percent of drift on a commit that never touched the measured code path, which makes real regressions harder to spot.

Pinning PYTHONHASHSEED: 0 for the workflow removes that source of run-to-run variation.

CodSpeed doesn't call out PYTHONHASHSEED specifically, but this is the same idea as their Keep Benchmarks Deterministic guidance, applied to the interpreter rather than to the benchmark body. Their write-up on unrelated benchmark regressions covers the wider class of environment-driven drift this belongs to.

Only the workflow env changes; no package source is touched.

[greptile-apps]

Greptile Summary

Pins PYTHONHASHSEED to make performance results deterministic across workflow runs.

• Adds a workflow-level fixed Python hash seed.
• Documents how randomized dictionary probe sequences can introduce benchmark drift.

Confidence Score: 5/5

The PR appears safe to merge with no actionable defects identified.

The fixed hash seed consistently applies to benchmark runs as intended, while no workflow consumer was found that requires randomized Python hashing.

Important Files Changed

Filename	Overview
.github/workflows/performance.yml	Adds a documented deterministic Python hash seed without introducing a concrete workflow failure or violating repository rules.

_{Reviews (1): Last reviewed commit: "Pin PYTHONHASHSEED in the benchmark work..." | Re-trigger Greptile}

[cubic-dev-ai]

No issues found across 1 file

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[codspeed-hq]

Merging this PR will not alter performance

✅ 32 untouched benchmarks
⏩ 8 skipped benchmarks¹

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Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩