# Maintainer resilience

> How inspect.software measures bus factor, contributor concentration, and breadth — whether a project can survive losing its top maintainer. 7.2% of the index.


**Maintainer resilience** asks the uncomfortable question: *can this project
survive losing its most important person?* The pattern it measures — a
single maintainer carrying essentially all of the work — is the most common
structural failure mode in open source, and it is invisible in commit counts
and stars.

- **Category:** [Sustainability & Governance](/wiki/sustainability-governance) (30% within category)
- **Weight in overall index:** 7.2%
- **Metric key:** `maintainer_resilience`
- **`null`** when the contributor list is unavailable, or when every
  contributor turned out to be an automation account

## How the value is computed

| Component | Weight | Criteria |
| --------- | ------ | -------- |
| Bus factor | 54 | v0.9.0 bus-factor curve, scaled to 54 points |
| Commit distribution | 22.5 | `(1 − top contributor's share of human commits) × 22.5` |
| Contributor breadth | 13.5 | `min(13.5, human contributors sampled × 1.35)` |
| OpenSSF Scorecard: Contributors | 10 | Scorecard's 0–10 result, scaled to 10 points |

The **bus factor** is the smallest number of contributors who together
account for the majority of the work — the number of people whose departure
would stall the project.

Every figure here counts **people only**. Automation accounts are removed
before the bus factor, the distribution, or the breadth is derived, because a
release robot cannot inherit a project. The removal is not cosmetic: in
several widely used repositories, dependency bots rank second and third among
all contributors by commit count, and counting them made the maintainer base
look broader and less concentrated than it is. Only automation carrying a
GitHub App identity is recognized, so a bot operating under an ordinary user
account is still counted as a person.

The Scorecard component measures contributing organizations/companies, a
useful complementary signal of institutional resilience. It also remains part
of Security and is excluded here if unavailable or `n/a`.

## Why the curve is shaped this way

The jump from a bus factor of 1 to 2 (10 → 28 points) is the largest single
step in the methodology, because it is the largest real-world risk
reduction: the difference between a project with a single point of failure
and one without. Returns diminish beyond 4–5 — once several people genuinely
share the work, adding more changes little.

Commit distribution complements the bus factor: a project can technically
have five contributors while one person authors 95% of the changes. The
distribution component makes that concentration visible.

## Reading the result

- A **low value on a high-[Vitality](/wiki/vitality) project** is the classic
  solo-maintainer profile: productive today, fragile tomorrow.
- Cross-read with [stewardship](/wiki/stewardship) — organization backing
  mitigates (but does not remove) the risk this metric measures.
- Contributor data is sampled from the repository's public history. Automation
  accounts are reported — the count removed is echoed in the report alongside
  the other inputs — but they are excluded from every figure scored here.
- For the displayed top ten contributors, authenticated scans also collect
  self-published GitHub profile name, location, company, and public organization
  memberships in one batched request. This enrichment is not used in the score
  and is withheld from public API and HTML reports; it supports internal
  identity-resolution research without changing the bus-factor calculation.

## Improving the value

- Grant review and merge rights to at least one more person — moving the bus
  factor from 1 to 2 is the single biggest gain available.
- Actively distribute work: route reviews and releases across maintainers
  rather than through one person.
- Convert recurring contributors into maintainers; breadth counts, and the
  pipeline starts with [community health](/wiki/community-health).

Related: [stewardship](/wiki/stewardship) ·
[Sustainability & Governance](/wiki/sustainability-governance)