Claude
a8d1fcce3f
Human ruling on the needs-human-review allocator swap (+4.6%, CI [+3.3%,+5.8%]): accepted as a real win for the measured comrak CLI single-stream markdown-render workload, explicitly not a blanket mimalloc mandate. Ledger row stays needs-human-review (append-only); the ruling is documented in results/rulings/phase0-comrak-002.md and reflected in the case study. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2
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Human ruling — phase0-comrak-002 (mimalloc allocator swap)
Ruling: ACCEPTED, scoped to the measured workload.
Ruled by: project owner (repo maintainer), recorded 2026-07-12.
Ledger row: phase0-comrak-002 remains needs-human-review (the
append-only ledger records what the pipeline decided; this document is
the human decision layered on top).
What was measured
Swapping comrak's global allocator to mimalloc:
- Speedup: 1.046 median, 95% CI [1.033, 1.058] (+4.6%) on the comrak CLI rendering the pinned Pro Git corpus (11.0 MB markdown, single stream), interleaved A/B vs a pristine-rebuilt baseline.
- Byte-identical golden replay. The pipeline routed it to
needs-human-reviewper SPEC §8 because a global allocator swap is a behavioral change no single benchmark can fully clear.
The ruling and its scope
Accepted as a real, CI-significant win for the comrak CLI's
single-stream markdown-render workload — the workload measured, on the
calibrated hardware in results/calibration/.
This is explicitly not a blanket "always link mimalloc" mandate:
- The upside (+4.6%) is genuine but modest; it does not justify making mimalloc a default across unrelated targets or workloads without their own measurement.
- The comrak CLI on this workload is single-threaded, which is what makes the ruling low-risk here — the concurrency/fragmentation concerns SPEC §8 flags are minimal for a short-lived, single-stream CLI process. A long-running or heavily-multithreaded comrak library embedding would need its own review before inheriting this.
Why this is the honest resolution
The needs-human-review tier exists precisely to force this judgment
instead of letting a green benchmark auto-ship a global behavioral
change. The judgment: yes for the measured CLI workload, with the scope
written down so the number can't be over-generalized later. The tier did
its job; the win is real; the ruling is bounded.