---
key: process.build-concurrency-limits
title: 2026-07-21 — Bound parallel builds by FREE RAM, never regenerate goldens (#542)
status: active
since: '2026-07-21'
supersedes: none
superseded-by: none
rule: Run at most 3–4 concurrent dotnet/npm builds on this Mac, gate launches on FREE RAM rather than CPU load, and never set `ETV_UPDATE_GOLDENS` / `ETV_UPDATE_PLAYOUT_GOLDENS`.
signals: 'build concurrency · memory_pressure · RAM starvation · fan-out cap · golden regeneration · paths: n/a · issues: #542'
mechanics: '`memory_pressure -Q` — under 20% free, do not launch more build agents; under 10%, pause or stagger. Host is an M4, 10 cores, 16 GB.'
---

Parallelize by default when slices are genuinely disjoint: use up to the client's concurrency limit,
normally 2–3 delegated agents plus the orchestrator. Fan out bounded recon early, but do not invent
artificial slices or exceed a runtime-imposed agent cap. CPU load spikes during builds are benign and
are not a stop signal; the resource that actually runs out is memory — the historic crash was RAM
starvation from an 8–9-way fan-out, which is why 5+ concurrent builds is never acceptable.

Separately: never set the golden-regeneration env vars. Regenerating goldens to make a diff disappear
hides exactly the change the golden net exists to surface.
