fix: run both mutation tools in place so their baselines see the real tree (fixes #1409)

.github/workflows/mutation.yml

@@ -64,6 +64,31 @@ name: Mutation Testing
 #     tracking issue" quietly became a pair. A single downstream job that
 #     aggregates `needs.*.result` cannot race itself.
 #
+# BOTH TOOLS RUN IN PLACE (#1409). Run 34812562007 (2026-09-14) failed both
+# baselines before a single mutant ran, and the two failures were one class:
+# each tool runs the suite in a COPY of the project, and both suites read the
+# real tree.
+#   - cargo-mutants copies only `src-tauri/`. `progress.test.rs` reads
+#     `../src/export/PdfExportDialog.tsx` → NotFound → "FAILED Unmutated
+#     baseline". #1210 hit the same wall with `command_error.test.rs` and was
+#     patched with a per-test sandbox skip; on macOS the copy does not even
+#     BUILD, because six `include_str!`s reach `../../../src/lib/browser/agent/`.
+#   - Stryker copies into `.stryker-tmp/sandbox-*` and symlinks `node_modules`
+#     in from outside it. Vite's `server.fs.allow` is rooted at the sandbox, so
+#     `katex.min.css?raw` resolved to a real path outside the allow list:
+#     `Denied ID …`. Three test files failed that way (`printDocument`,
+#     `copyAsHtml`, `pickPrintHtmlSource`, measured by running the related set
+#     inside a sandbox); this log named one, because the dry run bails at the
+#     first failure. Vitest wraps the error as "There was an error when mocking
+#     a module", and the Stryker runner keeps only an error's top-level message,
+#     so the cause never reached this log either.
+# No copy, no class: `--in-place` below (a CLI-only flag in cargo-mutants 27.1.0,
+# which refuses it alongside `--jobs` or `CARGO_MUTANTS_JOBS`) and `inPlace` in
+# stryker.config.json, which both Stryker entry points name explicitly.
+# `scripts/check-mutation-in-place.test.mjs` (gate tier) fails if either tool is
+# invoked any other way. The checkout is disposable, so mutating it in place
+# costs nothing.
+#
 # See dev-docs/testing-hardening.md.
 
 # liveness-gate: true
@@ -125,9 +150,10 @@ jobs:
         # the findings. Only real errors fail the job: usage/internal (1) and
         # a red unmutated baseline (4), which is how this workflow's original
         # silent death began. See cargo-mutants' documented exit codes.
+        # `--in-place`: see "BOTH TOOLS RUN IN PLACE" above.
         run: |
           set +e
-          cargo mutants --manifest-path src-tauri/Cargo.toml
+          cargo mutants --in-place --manifest-path src-tauri/Cargo.toml
           rc=$?
           set -e
           case "$rc" in
@@ -159,6 +185,19 @@ jobs:
 
       - run: pnpm install --frozen-lockfile
 
+      - name: Dry run, listing EVERY failing test (Stryker)
+        # The mutation run below bails its dry run at the FIRST failing test
+        # (the vitest runner passes `bail: 1` unless `disableBail`), so a red
+        # baseline is discovered one test per weekly run: run 34812562007
+        # named one of the three failing files. This dry run does not bail, so
+        # it names them all in one pass. Its price is one extra green dry run a
+        # week (8m04s in run 34089856980). `disableBail` stays out of
+        # stryker.config.json on purpose: it applies to every mutant run too,
+        # where stopping at the first kill is the speed. The config is named
+        # explicitly here and in `mutation:ts`: with no argument Stryker
+        # discovers one, and tries `stryker.conf.*` before `stryker.config.*`.
+        run: pnpm exec stryker run stryker.config.json --dryRunOnly --disableBail
+
       - name: Run scoped mutation testing (Stryker)
         # Scope is defined in stryker.config.json (mutate globs).
         run: pnpm mutation:ts

.gitignore

@@ -157,9 +157,12 @@ temp/
 # E2E smoke harness screenshot artifacts (regenerate with `pnpm e2e:smoke`)
 e2e/artifacts/
 
-# Stryker mutation testing (run with `pnpm mutation:ts`)
+# Stryker mutation testing (run with `pnpm mutation:ts`). It runs IN PLACE
+# (#1409), so the vitest runner writes its stryker-setup-<worker>.js files into
+# the project root. It deletes them when a run ends; a killed run may not.
 .stryker-tmp/
 reports/mutation/
+stryker-setup-*.js
 
 # Vitest browser-tier (WebKit) artifacts (run with `pnpm test:browser`)
 src/**/__screenshots__/

package.json

@@ -62,7 +62,7 @@
     "knip": "knip",
     "knip:files": "knip --include files,dependencies",
     "dup": "jscpd",
-    "mutation:ts": "stryker run",
+    "mutation:ts": "stryker run stryker.config.json",
     "test:sidecar": "pnpm --dir server/mcp lint && pnpm --dir server/mcp build && pnpm --dir server/mcp test:coverage",
     "test:content-server": "pnpm --dir server/content build && pnpm --dir server/content smoke && pnpm --dir server/content test:coverage",
     "check:static": "pnpm lint && pnpm lint:console && pnpm lint:ui-consistency && pnpm lint:design-tokens && pnpm lint:emdash && pnpm lint:cjk-demo-parity && pnpm lint:no-nul-bytes && pnpm lint:deps && pnpm lint:hooks-purity && pnpm lint:extension-budget && pnpm lint:store-coupling && pnpm lint:mock-boundaries && pnpm lint:command-errors && pnpm lint:ipc-contract && pnpm lint:trusted-html && pnpm lint:type-aware && pnpm lint:test-types && pnpm lint:mutants-config && pnpm lint:deleted-names && pnpm lint:mcp-contracts && pnpm lint:mcp-docs && pnpm lint:tauri-versions && pnpm lint:webview-floor && pnpm lint:window-thread && pnpm lint:i18n && pnpm lint:themes && pnpm lint:theme-contrast && pnpm lint:keybinding-manifest && pnpm lint:merge-drops && pnpm lint:file-size && pnpm lint:timer-isolation && pnpm lint:barrels && pnpm lint:shell-slots && pnpm lint:bespoke-buttons && pnpm knip && pnpm lint:knip-baseline && pnpm lint:test-only-modules && pnpm lint:header-refs && pnpm lint:doc-joins && pnpm lint:review-schedule && pnpm test:gates",