Publish cargo-mutants CI template; adopt in kiln, loom, gale, meld

[avrabe]

Part of the V&V coverage initiative.

Problem

rivet runs cargo-mutants as a pre-commit hook today — the only project in the estate doing mutation testing. Mutation testing is the strongest test-suite-adequacy metric recognized under IEC 61508 Annex C.5.12 and ISO 26262-6 Table 13, and is arguably the Rust-world answer to the open MC/DC-for-Rust problem.

We should generalize the pattern: publish the template here and drive adoption in kiln, loom, gale, meld — the four highest-safety-stake Rust codebases in pulseengine.

Acceptance

• Extract rivet's cargo-mutants configuration into a reusable template (workflow YAML + mutants.toml config)
• Document the pattern in rivet/docs/mutation-testing.md:
  • When to run (pre-commit optional, CI required, nightly deep-scan)
  • How to set mutation-score targets per ASIL/DAL level (e.g. ≥90% for ASIL-D)
  • How to mark unreachable mutants (`# skip = `) with rationale
• Open follow-up issues on each adopter repo linking back here:
  • kiln: adopt mutation testing
  • loom: adopt mutation testing
  • gale: adopt mutation testing
  • meld: adopt mutation testing
• Ensure rivet.yaml schema records mutation_score on TEST-* artifacts across repos
• Dashboard view (in the coverage-matrix issue) surfaces mutation score per repo

Notes

• cargo-mutants is slow — batch on CI-matrix by crate, not full workspace
• Mutation score is the best answer to "is our test suite good enough?" and directly addresses the MC/DC gap for Rust
• This is pulseengine's single most differentiated V&V asset; generalizing it is high leverage

[avrabe]

Triage: acceptance criteria are present. The in-scope deliverables for pulseengine/rivet itself:

• (in scope) Extract cargo-mutants config into a reusable template (workflow YAML + mutants.toml)
• (in scope) docs/mutation-testing.md documenting when to run, score targets per ASIL/DAL, how to mark unreachable mutants
• (in scope) Schema field mutation_score on TEST-* artifacts

Out of scope for an autonomous run scoped to pulseengine/rivet:

• Open follow-up issues on kiln/loom/gale/meld — must be filed from a session with broader org scope.
• Dashboard view across repos — depends on V&V coverage matrix dashboard via rivet coverage (per-commit, per-repo, per-technique) #188.

I'll pair this with #186 (template-extraction story is the same shape) and open a single PR per issue. Heads-up that the cross-repo adoption issues will need to be filed manually.

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Generated by Claude Code

[avrabe]

Picked this up — opened #229 against main from feat/issue-185-cargo-mutants-template.

In-scope acceptance bullets satisfied:

• ✅ Reusable template at templates/cargo-mutants/{mutants.toml, mutants.yml, README.md} — mutants.toml mirrors rivet's pre-push profile (60 s timeout, --lib, sensible exclude_globs / skip_calls); mutants.yml is a nightly + manual-dispatch GitHub Actions workflow with a per-crate matrix.
• ✅ docs/mutation-testing.md — when-to-run table, ASIL/DAL score-target ladder (≥ 0.70 ASIL A → ≥ 0.90 ASIL D), mutants.toml skip patterns, per-function #[cfg_attr(test, mutants::skip)] recipe, and how to record results in rivet artifacts.
• ✅ Schema fields land in schemas/score.yaml: mutation-score-target on test-spec, mutation-score + mutants-tested / killed / missed / timeout / unviable counts on test-exec.

Acknowledged out of scope (cannot be filed from a session scoped to pulseengine/rivet):

• Cross-repo adoption issues on kiln, loom, gale, meld — needs broader org access.
• Cross-repo dashboard view — depends on V&V coverage matrix dashboard via rivet coverage (per-commit, per-repo, per-technique) #188.

PR is opened with Closes #185. If you'd prefer to keep this issue open until the cross-repo adoption issues are filed, just downgrade the trailer to Refs: #185 on merge.

Verification on the branch: cargo test -p rivet-core --lib (857), --test integration + --test schema_agent_pipelines + --test yaml_roundtrip (14), cargo fmt --check clean, rivet validate diagnostics unchanged from origin/main.

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Generated by Claude Code — issue-triage agent run 2026-04-27.

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Generated by Claude Code