test(infra): isolate DATA_DIR per test process; raise Stryker concurrency 1→4 (#4078)

* test(infra): isolate DATA_DIR per test process; raise Stryker concurrency 1→4 Every test process resolved DATA_DIR to the same default (~/.omniroute) when the env var was unset (src/lib/dataPaths.ts::resolveDataDir), so concurrent test files opened the SAME on-disk storage.sqlite. node:test spawns a process per file and Stryker spawns one per sandbox, so this shared file caused cross-file state races: - SQLite lock contention that hung `npm run test:unit` under high --test-concurrency (the ~95-min local hang), and - the non-deterministic baseline that forced stryker.conf.json to concurrency: 1, which in turn could not finish the ~15k-mutant run inside the nightly timeout (the cancelled 2026-06-16/17 nightly-mutation runs) — blocking Quality Gate v2 / Fase 9 Onda 2. open-sse/utils/setupPolyfill.ts could NOT host the fix: it is imported by production (bin/omniroute.mjs, proxyFetch.ts, proxyDispatcher.ts), where redirecting DATA_DIR would point the live SQLite DB at a throwaway temp dir. So this adds a TEST-ONLY tests/_setup/isolateDataDir.ts that gives each process its own temp DATA_DIR when none is set (tests that set DATA_DIR explicitly still win), wired via --import into the test, mutation and CI invocations. Verified: - Stryker dry-run A/B at concurrency=4: FAILS without the isolation import (account-fallback-service tap exit 9, a cross-file race) and PASSES with it. - Full `npm run test:unit` green with isolation (0 fail; a one-off chatcore-translation-paths timeout flake did not reproduce and passes 3/3 isolated) and noticeably faster — the DB lock contention is gone. - New tests/unit/isolate-datadir.test.ts guards the contract (unique temp DATA_DIR when unset; explicit DATA_DIR respected). Wired the --import into: package.json (13 test scripts), stryker.conf.json (tap.nodeArgs + concurrency 1→4), .github/workflows/quality.yml (TIA step), ci.yml (the 5 unit/coverage/integration commands), and bumped nightly-mutation.yml timeout 120→180 for the first cold run before the incremental cache is seeded. * ci(quality): run the TIA gate at CI concurrency (4) to stop oversubscription flakes The TIA "Impacted unit tests" step (made blocking in #4069) ran its fail-safe via `npm run test:unit` — concurrency=20, tuned for multi-core dev machines. On a 4-vCPU CI runner that is 5x oversubscribed, so timing-sensitive tests flake under the load (e.g. `db-backup-extended` "The database connection is not open", `chatcore-translation-paths` upstream-timeout). That intermittently fails a blocking gate on legitimate PRs — exactly what surfaced on the DATA_DIR-isolation PR, whose package.json/workflow changes trip the __RUN_ALL__ fail-safe. Run both the impacted set and the fail-safe at --test-concurrency=4, matching the stable ci.yml unit job. Adds a `test:unit:ci` script (test:unit at concurrency=4). The DATA_DIR isolation in this PR keeps the parallel run race-free, so the only change here is matching the runner's core count. Verified locally: db-backup-extended passes 8/8 in isolation (5 with isolation, 3 without).
2026-07-26 09:52:11 +03:00 · 2026-06-17 13:46:28 -03:00
parent 081bf30bbd
commit 240f466f54
7 changed files with 118 additions and 24 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -513,7 +513,7 @@ jobs:
          cache: npm
      - run: npm ci
      - run: npm run check:node-runtime
-      - run: node --max-old-space-size=4096 --import tsx --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/8 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"
+      - run: node --max-old-space-size=4096 --import tsx --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/8 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"

  test-vitest:
    name: Vitest (MCP / autoCombo / UI components)
@@ -566,7 +566,7 @@ jobs:
      - run: npm ci
      - run: npm run check:node-runtime
      - run: npm run build
-      - run: node --import tsx --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/2 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"
+      - run: node --import tsx --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/2 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"

  node-26-compat:
    name: Node 26 Compatibility (${{ matrix.shard }}/2)
@@ -592,7 +592,7 @@ jobs:
      - run: npm ci
      - run: npm run check:node-runtime
      - run: npm run build
-      - run: node --import tsx --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/2 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"
+      - run: node --import tsx --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 --test-shard=${{ matrix.shard }}/2 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"

  test-coverage-shard:
    name: Coverage Shard (${{ matrix.shard }}/8)
@@ -632,7 +632,7 @@ jobs:
            --reporter=json \
            --exclude=tests/** \
            --exclude=**/*.test.* \
-            node --max-old-space-size=4096 --import tsx --test --test-force-exit --test-concurrency=4 \
+            node --max-old-space-size=4096 --import tsx --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 \
              --test-shard=${{ matrix.shard }}/8 tests/unit/*.test.ts "tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts"
      - name: Upload raw shard coverage
        if: always()
@@ -902,7 +902,7 @@ jobs:
          cache: npm
      - run: npm ci
      - run: npm run check:node-runtime
-      - run: node --import tsx --test --test-force-exit --test-concurrency=1 --test-shard=${{ matrix.shard }}/2 tests/integration/*.test.ts
+      - run: node --import tsx --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=1 --test-shard=${{ matrix.shard }}/2 tests/integration/*.test.ts

  test-security:
    name: Security Tests
--- a/.github/workflows/nightly-mutation.yml
+++ b/.github/workflows/nightly-mutation.yml
@@ -11,11 +11,16 @@ jobs:
  stryker:
    name: Stryker mutation testing (8 critical modules — advisory)
    runs-on: ubuntu-latest
-    # Mutation testing is expensive (~200-500 mutants, 30-90 min). It runs only
+    # Mutation testing is expensive (~15k mutants across 8 modules). It runs only
    # on the nightly schedule / manual dispatch, never on PRs. The score is NOT
    # yet enforced as a ratchet (wired in a later INT phase) — for now the job
    # just produces the HTML/JSON report and uploads it as an artifact.
-    timeout-minutes: 120
+    #
+    # Runs at stryker concurrency=4 (was 1) now that ./tests/_setup/isolateDataDir.ts
+    # gives each test process its own DATA_DIR — at concurrency=1 the full phase did
+    # not finish inside the timeout (the cancelled 2026-06-16/17 runs). 180 min leaves
+    # headroom for the first cold run before the incremental cache is seeded.
+    timeout-minutes: 180
    steps:
      - uses: actions/checkout@v6
        with:
--- a/.github/workflows/quality.yml
+++ b/.github/workflows/quality.yml
@@ -71,9 +71,14 @@ jobs:
          node scripts/quality/build-test-impact-map.mjs
          SEL="$(node scripts/quality/select-impacted-tests.mjs)"
          if [ -z "$SEL" ]; then echo "No source/test changes — skipping unit tests"; exit 0; fi
+          # CI runners are 4-vCPU; run at --test-concurrency=4 (matching the ci.yml unit
+          # job) rather than test:unit's local-tuned concurrency=20. Oversubscribing the
+          # runner makes timing-sensitive tests (db-backup, upstream-timeout, ...) flake,
+          # which must not happen on a blocking gate. DATA_DIR isolation keeps the parallel
+          # run race-free regardless of concurrency.
          if echo "$SEL" | grep -q "__RUN_ALL__"; then
-            echo "Fail-safe: running FULL unit suite"; npm run test:unit; exit $?
+            echo "Fail-safe: running FULL unit suite (CI concurrency)"; npm run test:unit:ci; exit $?
          fi
          echo "Running impacted tests:"; echo "$SEL"
          mapfile -t FILES <<< "$SEL"
-          node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=8 "${FILES[@]}"
+          node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 "${FILES[@]}"
--- a/package.json
+++ b/package.json
@@ -86,15 +86,16 @@
    "electron:build:mac": "npm run build && cd electron && npm run build:mac",
    "electron:build:linux": "npm run build && cd electron && npm run build:linux",
    "electron:smoke:packaged": "node scripts/dev/smoke-electron-packaged.mjs",
-    "test": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-concurrency=20 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
-    "test:unit": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=20 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
-    "test:unit:fast": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-isolation=none tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-concurrency=20 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:unit": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=20 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:unit:ci": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=4 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:unit:fast": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-isolation=none tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
    "test:unit:shard": "concurrently --kill-others-on-fail -n s1,s2 \"npm:test:unit:shard:1\" \"npm:test:unit:shard:2\"",
-    "test:unit:shard:1": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=10 --test-shard=1/2 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
-    "test:unit:shard:2": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=10 --test-shard=2/2 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
-    "test:plan3": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test tests/unit/plan3-p0.test.ts",
-    "test:fixes": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test tests/unit/fixes-p1.test.ts",
-    "test:security": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test tests/unit/security-fase01.test.ts",
+    "test:unit:shard:1": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=10 --test-shard=1/2 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:unit:shard:2": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=10 --test-shard=2/2 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:plan3": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test tests/unit/plan3-p0.test.ts",
+    "test:fixes": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test tests/unit/fixes-p1.test.ts",
+    "test:security": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test tests/unit/security-fase01.test.ts",
    "test:property": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --test --test-force-exit tests/unit/correctness/*.property.test.ts",
    "check:cycles": "node scripts/check/check-cycles.mjs",
    "check:route-validation:t06": "node scripts/check/check-route-validation.mjs",
@@ -159,17 +160,17 @@
    "typecheck:noimplicit:core": "tsc --pretty false -p tsconfig.typecheck-noimplicit-core.json",
    "backfill-aggregation": "node --import tsx src/scripts/backfillAggregation.ts",
    "env:sync": "node scripts/dev/sync-env.mjs",
-    "test:integration": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=1 tests/integration/*.test.ts",
-    "test:heap": "node --expose-gc --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit tests/integration/heap-growth.test.ts",
-    "test:chaos": "cross-env RUN_CHAOS_INT=1 node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=1 tests/integration/resilience-chaos.test.ts",
+    "test:integration": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=1 tests/integration/*.test.ts",
+    "test:heap": "node --expose-gc --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit tests/integration/heap-growth.test.ts",
+    "test:chaos": "cross-env RUN_CHAOS_INT=1 node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=1 tests/integration/resilience-chaos.test.ts",
    "test:e2e": "node scripts/dev/run-playwright-tests.mjs test tests/e2e/*.spec.ts",
    "test:protocols:e2e": "node scripts/dev/run-protocol-clients-tests.mjs",
    "test:vitest": "vitest run --config vitest.mcp.config.ts",
    "test:vitest:ui": "vitest run --config vitest.config.ts tests/unit/ui",
    "test:mutation": "stryker run",
    "test:ecosystem": "node scripts/dev/run-ecosystem-tests.mjs",
-    "test:system": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=1 tests/e2e/system-failover.test.ts",
-    "test:coverage": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true c8 --output-dir coverage --exclude=tests/** --exclude=**/*.test.* --reporter=text-summary --reporter=html --reporter=json-summary --reporter=lcov --check-coverage --statements 60 --lines 60 --functions 60 --branches 60 node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --test --test-force-exit --test-concurrency=8 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
+    "test:system": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true node --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=1 tests/e2e/system-failover.test.ts",
+    "test:coverage": "cross-env DISABLE_SQLITE_AUTO_BACKUP=true c8 --output-dir coverage --exclude=tests/** --exclude=**/*.test.* --reporter=text-summary --reporter=html --reporter=json-summary --reporter=lcov --check-coverage --statements 60 --lines 60 --functions 60 --branches 60 node --max-old-space-size=8192 --import tsx --import ./open-sse/utils/setupPolyfill.ts --import ./tests/_setup/isolateDataDir.ts --test --test-force-exit --test-concurrency=8 tests/unit/*.test.ts \"tests/unit/{api,auth,authz,build,cli,cli-helper,compression,correctness,cors,dashboard,db,db-adapters,docs,gamification,guardrails,lib,mcp,runtime,security,services,settings,shared,ui}/**/*.test.ts\"",
    "test:coverage:legacy": "c8 --output-dir coverage --exclude=open-sse --check-coverage --lines 50 --functions 50 --branches 50 node --import tsx --test tests/unit/*.test.ts",
    "coverage:report": "c8 report --output-dir coverage --exclude=tests/** --exclude=**/*.test.* --reporter=text --reporter=text-summary --reporter=html --reporter=json-summary --reporter=lcov",
    "coverage:summary": "node scripts/check/test-report-summary.mjs --input coverage/coverage-summary.json --output coverage/coverage-report.md",
--- a/stryker.conf.json
+++ b/stryker.conf.json
@@ -177,6 +177,8 @@
      "tsx",
      "--import",
      "./open-sse/utils/setupPolyfill.ts",
+      "--import",
+      "./tests/_setup/isolateDataDir.ts",
      "--test-reporter=tap",
      "-r",
      "{{hookFile}}",
@@ -223,7 +225,7 @@
  "coverageAnalysis": "perTest",
  "timeoutMS": 60000,
  "timeoutFactor": 2.5,
-  "concurrency": 1,
+  "concurrency": 4,
  "disableTypeChecks": true,
  "checkers": [],
  "thresholds": {
@@ -246,5 +248,5 @@
    "  grep -rlE \"circuitBreaker|publicCreds|accountFallback|routeGuard|services/auth|chatCore|services/combo|utils/error|public-client|account-fallback|route-guard|circuit-breaker\" tests/unit --include=\"*.test.ts\" | sort -u"
  ],
  "dryRunTimeoutMinutes": 30,
-  "_concurrency_comment": "concurrency=1: the covering node:test files share SQLite/module state; running multiple files concurrently in the Stryker sandbox causes cross-file state races that fail the all-green baseline dry-run. Single-runner trades speed for a deterministic baseline (acceptable for a nightly)."
+  "_concurrency_comment": "concurrency=4 (was 1): the covering node:test files used to share SQLite/module state via the default DATA_DIR (~/.omniroute), so running them concurrently in the Stryker sandbox caused cross-file races that failed the all-green baseline. tap.nodeArgs now imports ./tests/_setup/isolateDataDir.ts, which gives each spawned test process its own temp DATA_DIR — eliminating the shared on-disk DB, so concurrency>1 is deterministic. A/B verified 2026-06-17: dry-run at concurrency=4 fails WITHOUT the isolation import (account-fallback-service tap exit 9) and passes WITH it. Raise further only if the runner has spare cores."
 }
--- a/tests/_setup/isolateDataDir.ts
+++ b/tests/_setup/isolateDataDir.ts
@@ -0,0 +1,36 @@
+// Test-only DATA_DIR isolation.
+//
+// Loaded via `node --import ./tests/_setup/isolateDataDir.ts` from the test/mutation
+// invocations (package.json test scripts, stryker.conf.json tap.nodeArgs, the
+// quality.yml TIA step, and the CI test jobs) — NEVER from production. It MUST stay
+// out of open-sse/utils/setupPolyfill.ts, which is also imported by production
+// (bin/omniroute.mjs, proxyFetch.ts, proxyDispatcher.ts) where redirecting DATA_DIR
+// would point the live SQLite DB at a throwaway temp dir.
+//
+// Why: node:test spawns a process per test file and Stryker spawns one per sandbox,
+// but every process resolves DATA_DIR to the SAME default (~/.omniroute) when the env
+// var is unset (see src/lib/dataPaths.ts::resolveDataDir). Concurrent processes then
+// open the SAME on-disk storage.sqlite, causing cross-file state races: SQLite lock
+// contention that hangs `test:unit` under high `--test-concurrency`, and the
+// non-deterministic baseline that forced Stryker to `concurrency: 1`.
+//
+// Giving each process its own DATA_DIR under the OS temp dir removes the shared file,
+// so concurrent test processes never collide. Tests that set DATA_DIR explicitly keep
+// winning — this only fills in an isolated default when none was chosen.
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+if (!process.env.DATA_DIR) {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-test-"));
+  process.env.DATA_DIR = dir;
+
+  // Best-effort cleanup so a long suite run does not leak hundreds of temp DBs.
+  process.on("exit", () => {
+    try {
+      fs.rmSync(dir, { recursive: true, force: true });
+    } catch {
+      // ignore — the OS reaps its temp dir eventually.
+    }
+  });
+}
--- a/tests/unit/isolate-datadir.test.ts
+++ b/tests/unit/isolate-datadir.test.ts
@@ -0,0 +1,45 @@
+// Regression guard for tests/_setup/isolateDataDir.ts — the test-only module that
+// gives each test process its own DATA_DIR so concurrent test files never share the
+// on-disk SQLite DB. Removing or breaking it brings back the cross-file state races
+// (the `test:unit` hang under high concurrency and the non-deterministic Stryker
+// baseline that forced concurrency: 1).
+import test from "node:test";
+import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
+import os from "node:os";
+
+function dataDirFromChild(envDataDir: string | undefined): string {
+  const result = spawnSync(
+    process.execPath,
+    [
+      "--import",
+      "tsx",
+      "--import",
+      "./tests/_setup/isolateDataDir.ts",
+      "-e",
+      "console.log(process.env.DATA_DIR ?? '')",
+    ],
+    {
+      encoding: "utf8",
+      cwd: process.cwd(),
+      // Pass DATA_DIR through verbatim; an empty string means "unset" for the module's
+      // `if (!process.env.DATA_DIR)` guard.
+      env: { ...process.env, DATA_DIR: envDataDir ?? "" },
+    }
+  );
+  return result.stdout.trim().split("\n").pop() ?? "";
+}
+
+test("isolateDataDir assigns a unique temp DATA_DIR when none is set", () => {
+  const a = dataDirFromChild(undefined);
+  const b = dataDirFromChild(undefined);
+
+  assert.ok(a.startsWith(os.tmpdir()), `expected a temp dir under ${os.tmpdir()}, got ${a}`);
+  assert.match(a, /omniroute-test-/, `expected the omniroute-test- prefix, got ${a}`);
+  assert.notEqual(a, b, "two processes must each get their own DATA_DIR");
+});
+
+test("isolateDataDir respects an explicitly set DATA_DIR", () => {
+  const explicit = "/tmp/omniroute-explicit-fixture";
+  assert.equal(dataDirFromChild(explicit), explicit);
+});