Summary

Root test/**/*.ts (all 111 Vitest lane configs, the shared harness, test/scripts/**, test/e2e/**, test/helpers/**) is not typechecked by any tsgo lane, and the changed gate runs no typecheck for test/ paths.

Findings

• test/tsconfig/tsconfig.core.test.json includes tests under src/, ui/, and packages/ but not root test/**; the only coverage is transitive (files imported from included roots). Observed cost: the envDir type error in test: fix changed-run routing, dedupe gateway package lanes, repair force-rerun triggers #104287 passed the remote check:changed gate and surfaced only in CI check-test-types — and only because that one config happens to be imported from the root vitest.config.ts.
• scripts/changed-lanes.mjs classifies test/ paths as the tooling lane, which runs lint only (no tsgo command in scripts/check-changed.mjs).
• A probe lane over test/**/* (extends root tsconfig, noUnusedLocals/noUnusedParameters, fixtures excluded) reports 1071 type errors: 518x TS7006 implicit-any params, 287x TS7016 missing declarations for scripts/**/*.mjs imports (the repo convention is sibling .d.mts files, which exist for some modules but not the ones test files import), and ~266 assorted real type issues. Top offenders: test/scripts/ci-node-test-plan.test.ts (98), test/scripts/ci-workflow-guards.test.ts (70), test/scripts/changed-lanes.test.ts (70).

Expected behavior

test/** TypeScript compiles under a dedicated tsgo lane (mirroring the tsgo:scripts lane from #104348), wired into check:test-types/scripts/check.mjs/the ci.yml test-types shard, with changed-file routing from test/**/*.ts edits.

Impact

• Affected: maintainers/agents relying on check:changed and CI for test-harness edits; deferred item from test harness follow-up: ui suite red with no CI lane, changed-gate typecheck gap, dead routing machinery, unenforced coverage thresholds #104321.
• Severity: medium; deterministic.

Additional information

Follow-up deferred from #104321 (see its closing comment) after #104361 landed. Fix PR follows, mirroring #104348.