feat(repo)!: time every PR's mutation phases against its base

.changeset/check-phase-duration.md

@@ -0,0 +1,12 @@
+---
+"@systemfsoftware/stryker-js-cli-contract": minor
+"@systemfsoftware/stryker-js": major
+---
+
+The verdict line's `phaseDurations` gains `check` and `reporting`. `check` is checker-busy wall-clock (the union of the intervals in which any checker was starting or checking); it overlaps the other phases, and a run with no checker configured reports `{ "_tag": "not-run" }` rather than zero. `reporting` runs from the end of mutant execution to the verdict, so `mutation-test` now stops where `reporting` starts, and the five sequential phases add up to the elapsed time.
+
+Breaking:
+
+- The stream emits a `phase` event for `reporting`, so `RunPhase` gains that value; exhaustive matches over `RunPhase` must handle it.
+- `mutation-test` no longer includes reporting time.
+- Verdict lines written before this release decode both new members as `{ "_tag": "not-recorded" }`.

.changeset/tce-emit-stays-in-temp.md

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+---
+"@systemfsoftware/stryker-js-typescript-checker": patch
+---
+
+The checker's equivalent-mutant detection no longer writes `.js` files next to your TypeScript sources. When your tsconfig reaches other sources through `paths` aliases or package imports, earlier versions left a compiled `.js` beside each of those files after a run. On the next run those files could change which tests ran.
+
+If an earlier version left stray `.js` files beside your `.ts` sources, delete them.

.github/workflows/bench.yml

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+name: Bench
+
+on:
+  pull_request:
+    paths-ignore:
+      - "**/*.md"
+      - "docs/**"
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  plan:
+    name: bench · one job per corpus entry
+    runs-on: ubuntu-latest
+    timeout-minutes: 1
+    outputs:
+      targets: ${{ steps.targets.outputs.targets }}
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          sparse-checkout: test/bench/corpus.json
+          sparse-checkout-cone-mode: false
+      - id: targets
+        name: Corpus entries
+        run: |
+          targets=$(jq -c '[.repo[].project, .enterprise.fixture] | map({ entry: ., slug: gsub("[^A-Za-z0-9._-]+"; "-") })' test/bench/corpus.json)
+          echo "targets=$targets" >> "$GITHUB_OUTPUT"
+
+  bench:
+    name: bench · ${{ matrix.target.entry }}
+    needs: plan
+    runs-on: ubuntu-latest
+    timeout-minutes: 9
+    strategy:
+      fail-fast: false
+      matrix:
+        target: ${{ fromJSON(needs.plan.outputs.targets) }}
+    env:
+      CI: "true"
+    steps:
+      - name: Bench deadline, 7.5 minutes after the job starts
+        run: echo "BENCH_DEADLINE_MS=$(($(date +%s%3N) + 450000))" >> "$GITHUB_ENV"
+
+      - uses: actions/checkout@v7
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+      - uses: pnpm/action-setup@v6
+      - uses: actions/setup-node@v7
+        with:
+          node-version: 24
+          cache: pnpm
+
+      - id: sides
+        name: Side A at the merge-base with the base branch
+        env:
+          BASE_REF: ${{ github.base_ref }}
+        run: |
+          git fetch --no-tags origin "+refs/heads/$BASE_REF:refs/remotes/origin/$BASE_REF"
+          base=$(git merge-base HEAD "origin/$BASE_REF")
+          side_a="$RUNNER_TEMP/bench-a"
+          git worktree add --detach "$side_a" "$base"
+          pin() { jq -c '.nodes["stryker-published"].locked' "$1/flake.lock"; }
+          {
+            echo "base=$base"
+            echo "a=$side_a"
+            echo "same-pin=$([ "$(pin "$side_a")" = "$(pin .)" ] && echo true || echo false)"
+          } >> "$GITHUB_OUTPUT"
+
+      - name: Released tarballs, side B
+        uses: ./.github/actions/released-tarballs
+      - if: steps.sides.outputs.same-pin != 'true'
+        uses: cachix/install-nix-action@v31
+
+      - name: Tarballs and install, both sides by one mechanism
+        env:
+          SIDE_A: ${{ steps.sides.outputs.a }}
+          SAME_PIN: ${{ steps.sides.outputs.same-pin }}
+          TIMINGS: ${{ runner.temp }}/bench-setup.tsv
+        run: |
+          started=$(date +%s%3N)
+          rm -rf "$SIDE_A/.sfs-deps"
+          if [ "$SAME_PIN" = true ]; then
+            cp -r .sfs-deps "$SIDE_A/.sfs-deps"
+          else
+            published=$(cd "$SIDE_A" && nix build --no-link --print-out-paths .#stryker-published)
+            mkdir "$SIDE_A/.sfs-deps"
+            cp "$published"/*.tgz "$SIDE_A/.sfs-deps/"
+            chmod u+w "$SIDE_A"/.sfs-deps/*.tgz
+          fi
+          printf 'side A: released tarballs\t%s\n' "$(($(date +%s%3N) - started))" >> "$TIMINGS"
+          install() {
+            local name=$1 root=$2 started
+            started=$(date +%s%3N)
+            (cd "$root" && pnpm install --frozen-lockfile)
+            printf 'side %s: pnpm install\t%s\n' "$name" "$(($(date +%s%3N) - started))" >> "$TIMINGS"
+          }
+          install A "$SIDE_A"
+          install B "$GITHUB_WORKSPACE"
+
+      - name: Turbo cache
+        uses: actions/cache@v6
+        with:
+          path: .turbo/cache
+          key: turbo-${{ runner.os }}-bench-${{ matrix.target.slug }}-${{ github.event.pull_request.head.sha }}
+          restore-keys: |
+            turbo-${{ runner.os }}-bench-${{ matrix.target.slug }}-
+            turbo-${{ runner.os }}-dist-
+
+      - name: Bench
+        env:
+          BENCH_ENTRY: ${{ matrix.target.entry }}
+          BENCH_SIDE_A: ${{ steps.sides.outputs.a }}
+          BENCH_SIDE_B: ${{ github.workspace }}
+          BENCH_BASE_SHA: ${{ steps.sides.outputs.base }}
+          BENCH_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+          BENCH_SETUP_TIMINGS: ${{ runner.temp }}/bench-setup.tsv
+        run: pnpm --filter @systemfsoftware/stryker-bench bench
+
+      - name: Bench report artifact
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@v7
+        with:
+          name: bench-report-${{ matrix.target.slug }}
+          path: ${{ runner.temp }}/bench-report/bench-report.json
+          if-no-files-found: warn
+          retention-days: 30
+
+      - name: Bench run streams artifact
+        if: ${{ !cancelled() }}
+        uses: actions/upload-artifact@v7
+        with:
+          name: bench-runs-${{ matrix.target.slug }}
+          path: ${{ runner.temp }}/bench-runs/
+          if-no-files-found: warn
+          retention-days: 7