ADR-0032: Liveness follows the configuration's format, with named exceptions in the native file

• Status: Accepted
• Date: 2026-09-23
• Derives from: design § Why ("superset, precisely; nothing is dropped"), ADR-0007, ADR-0030 (a drop-in exits as dependency-cruiser does), the private monorepo measurement in docs/perf.md
• Constrains: crates/rb-config (allowEmpty at the top level of a native file), crates/rb-model (summary.vacuousRules[].severity), crates/rb-cli (--liveness, cruise, fmt --exit-code, adopt)
• Supersedes: the clause of ADR-0007 that keeps the check failing "in dependency-cruiser compatibility mode". Its default for native files, its allowEmpty: true on a rule, --no-liveness, and summary.vacuousRules stand.
• Implemented by: Wave 1 plan, Steps 7 and 17
• Requirements: FR-CORE-05, NFR-CONF-01

Context

ADR-0007 fails a run when a rule's selecting side matches no module, in every mode. On a real dependency-cruiser repository that makes Rulebearing exit 2 where dependency-cruiser exits 0: the private monorepo of docs/perf.md has one such rule. The way out ADR-0007 gives, allowEmpty: true on the rule, cannot be written in a .dependency-cruiser.* file. dependency-cruiser's configuration schema rejects any key it does not define on a rule, so the file would stop working with dependency-cruiser. What is left is --no-liveness, which turns the check off for every rule, the opposite of what the check is for.

A drop-in that fails where dependency-cruiser passes is not a drop-in, and ADR-0030 already settled the same question for the error count.

Decision

• Three modes. --liveness strict fails the run with exit 2 (ADR-0007's behaviour). --liveness warn reports each vacuous rule in summary.vacuousRules[], with "severity": "warn", and as a warning: on stderr, without changing the exit code. --liveness off does not check. --no-liveness stays as the spelling of off, and cannot be combined with --liveness.
• The default follows the root file. A .dependency-cruiser.* configuration runs under warn, so it exits as dependency-cruiser exits. A rulebearing.* configuration runs under strict, including one that extends a dependency-cruiser file, which is what adopt writes. A repository opts into the check by adopting.
• Named exceptions. A native file may carry allowEmpty: [names] at the top level: rule names, ratchet names, and allowed[N] for the Nth allowed entry. Each named rule is exempt, as if it carried allowEmpty: true. The list merges through extends. A name that is no rule or ratchet of the configuration is a configuration error (exit 3), so an exception cannot outlive its rule. In a dependency-cruiser file the key is a native addition: a warning, and an error under --strict-compat, like the others (ADR-0005).
• adopt lists the rules that match nothing today under allowEmpty in the rulebearing.yaml it writes, and names them in its output and in the pull request, instead of refusing to adopt.
• Saved results. fmt --exit-code counts only the vacuousRules entries without "severity": "warn", so a saved result gates as its cruise did (ADR-0031). severity is additive and absent under strict.

Consequences

• A dependency-cruiser configuration runs under Rulebearing with dependency-cruiser's exit code, and a stale rule is still named on every run.
• A repository that adopts gets the check on every rule, and the exceptions are a reviewed list in one file rather than a global switch.
• Someone who uses Rulebearing only as a faster dependency-cruiser is warned about a dead rule, not stopped by it, which is what dependency-cruiser gives them today. --liveness strict restores the failure without adopting.
• Conformance gate 1 still passes --no-liveness, because dependency-cruiser's specs cover rules that match nothing on purpose.

Alternatives considered

• Keep ADR-0007 in every mode. Rejected: it keeps dependency-cruiser users on --no-liveness, which disables the check for every rule.
• Warn in every mode. Rejected: ADR-0007's reason stands for a repository that has chosen Rulebearing. Four rules matched nothing for months while warnings went unread.
• Accept allowEmpty on rules in a dependency-cruiser file. Rejected: the file would then fail dependency-cruiser's own validation, and a repository that runs both tools could not use it.