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slug: coordination-scale
created: 2026-05-12
updated: 2026-05-12
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# Coordination at Scale

Chromium is a multi-organization, globally distributed open-source project. Roughly 94% of commits come from Google employees; the remainder from Microsoft Edge, Igalia, Intel, and the broader community. The architecture is shaped, in Melvin Conway's sense, by the communication structure of the organizations contributing to it. The coordination patterns are the human systems that keep that arrangement working: OWNERS files give each directory a recursive list of engineers who must LGTM changes to it; Tree Sheriffs keep the continuous-integration tree green by reverting failing changes without waiting for the author; Perf Sheriffs triage performance regressions detected by the chromeperf dashboard to causative commits; cross-timezone review etiquette covers the eight-to-ten-hour gap between US and European contributors with attention-set discipline and 48-hour ping conventions.

The patterns and concepts in this section name those mechanisms. OWNERS File Governance describes the recursive scoping rules, the `per-file` directive, the `file://` inheritance directive, and the Gerrit integration that gates the commit queue. Tree Sheriff describes the rotating on-call role with authority to revert without author permission. Perf Sheriff describes the regression-alert thresholds (typically a 2% benchmark change triggers triage), the Bisect tool workflow, and the escalation path. Conway's Law in Multi-Org Chromium explains why certain architectural decisions cannot be understood in purely technical terms — they reflect negotiation between organizations with different interests. Cross-Timezone Review Etiquette covers the conventions that prevent code review from stalling across the US-Europe gap.

A new Chromium contributor, an Igalia or Microsoft Edge engineer evaluating a structural change, or an executive deciding whether to contribute or fork uses this section to navigate the human systems that govern the project as much as any technical decision does.

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