[bitbiter-dev]

Summary

When nothing is restored yet, Stryker's analysis runs several NuGet restores in parallel. If one of them fails, Stryker leaves that project unmutated, logs only a warning, and still scores the rest. Both workflows now run Stryker through a script that restores first and fails the run when Stryker logs that warning.

 Mutation (ci.yml) / Mutation divergence sweeps
-  working-directory: src
-  dotnet stryker --output ../mutation
+  scripts/stryker-sweep.sh --output ../mutation
+    dotnet restore Anichron.slnx
+    dotnet stryker "$@" | tee log
+    log contains "Analysis of project … failed"  → exit 1
+    otherwise                                    → Stryker's exit status

mutation-guard.sh now refuses any workflow that calls dotnet stryker directly. The new script is described in docs/mutation-testing.md and listed among the guard rules in CLAUDE.md.

Evidence

• Before: Mutation divergence run #6 logged Analysis of project Anichron.Worker/Anichron.Worker.csproj failed for frameworks net10.0. in the CI-concurrency sweep. That sweep tested 961 mutants and the single-threaded sweep tested 1595, so compare failed. The master gate at e014c80 (run) lost Worker the same way and passed at 100% with 846 mutants, where the runs around it tested about 1,400.
  After: scripts/stryker-sweep.test.sh (stubbed dotnet):

  clean log, stryker exit 0          → 0, restore runs before stryker, args passed through
  clean log, stryker exit 2          → 2
  "Analysis of project X failed"     → 1, names X
  test project "succeeded but
    simulated build failed"          → 0 (not a dropped project)
  restore fails                      → 1, stryker never runs
  

  A new mutation-guard.test.sh case checks that a workflow running dotnet stryker directly fails the guard. scripts/mutation-guard.sh passes on this branch.
• Pending: Mutation divergence run #7 on this branch should show Found project …/Anichron.Worker.csproj to mutate in both sweeps and the same number of mutants tested in each. It may still fail compare by one: chore(test): Single-threaded Stryker sweep reported a covered BurstRepository mutant as survived #305 is a separate case where the single-threaded sweep missed a kill.

Merge Danger

Door: two-way

Revert the commit and the workflows call dotnet stryker directly again.

Blast Radius: CI-only

The Mutation job gains a restore step of a few seconds. A run where Stryker drops a project now fails the gate instead of passing on a partial score, so a red Mutation job may come from this check rather than from a surviving mutant. The ::error:: annotation names the project.

🤖 Generated with Claude Code

[bitbiter-dev]

Divergence run #7 on this branch: both sweeps found Anichron.Worker and each tested 1595 mutants (run #6: 961 vs 1595). The comparison still fails by one, 1595 vs 1594, and the cause is the BurstRepository mutant tracked in #305, not this PR. This PR's own Mutation job also tested 1595 mutants and scored 100%.