diff --git a/.github/workflows/ci-quality.yml b/.github/workflows/ci-quality.yml
index 1b7185d1b..dffb6550b 100644
--- a/.github/workflows/ci-quality.yml
+++ b/.github/workflows/ci-quality.yml
@@ -53,6 +53,9 @@ jobs:
           lifecycle-scripts: 'false'
       - run: npx tsc --noEmit
         working-directory: gitnexus
+      - name: Typecheck tests
+        run: npm run typecheck:tests
+        working-directory: gitnexus
 
   typecheck-web:
     runs-on: ubuntu-latest
diff --git a/TESTING.md b/TESTING.md
index 9febb8283..4be0f73c5 100644
--- a/TESTING.md
+++ b/TESTING.md
@@ -19,6 +19,7 @@ From `gitnexus/`:
 | Command                       | What it runs                                       | When to use                           |
 | ----------------------------- | -------------------------------------------------- | ------------------------------------- |
 | `npm test`                    | Full suite (all 3 vitest projects)                 | Before opening a PR                   |
+| `npm run typecheck:tests`     | TypeScript checks for source, tests, and helpers   | Before opening a PR                   |
 | `npm run test:unit`           | Unit tests only (`test/unit/`)                     | Tight development loop                |
 | `npm run test:integration`    | Integration tests (`test/integration/`)            | After changing pipelines, DB, workers |
 | `npm run test:coverage`       | Full suite + v8 coverage with thresholds           | Checking coverage impact              |
@@ -26,6 +27,11 @@ From `gitnexus/`:
 | `npm run test:cross-platform` | Platform-sensitive subset only                     | Debugging a Windows/macOS issue       |
 | `npm run test:watch`          | Vitest in watch mode                               | Active development                    |
 
+Vitest transpiles TypeScript without checking types. Run `npm run typecheck:tests`
+in `gitnexus/` to check test code and helpers against the production types. This
+uses `tsc --noEmit -p tsconfig.test.json`; parser input files under `test/fixtures/`
+are excluded because they are sample source code, not part of the test program.
+
 ### `gitnexus-web/` commands
 
 From `gitnexus-web/`:
@@ -41,7 +47,7 @@ From `gitnexus-web/`:
 ```bash
 # gitnexus-shared/dist must exist first. `npm install` / `npm run build` in
 # gitnexus/ compiles it via parent `lib/tsc.js` (do not npm ci gitnexus-shared).
-cd gitnexus && npx tsc --noEmit && npm test
+cd gitnexus && npx tsc --noEmit && npm run typecheck:tests && npm test
 cd ../gitnexus-web && npx tsc -b --noEmit && npm test
 ```
 
@@ -121,6 +127,9 @@ GitHub Actions (`.github/workflows/ci.yml`) orchestrate:
 
 The `CI Gate` job in `ci.yml` is the single required check for branch protection. It requires quality, tests, e2e, and scope-parity to all pass.
 
+The `typecheck` job runs both the production compiler check and
+`npm run typecheck:tests`. A type error in either check fails the job and the CI gate.
+
 ## Regression testing
 
 Re-run the full relevant suite when:
diff --git a/gitnexus/package.json b/gitnexus/package.json
index 1db831d0d..99422e958 100644
--- a/gitnexus/package.json
+++ b/gitnexus/package.json
@@ -52,6 +52,7 @@
     "serve": "tsx src/cli/index.ts serve",
     "dev": "tsx watch src/cli/index.ts",
     "test": "vitest run",
+    "typecheck:tests": "tsc --noEmit -p tsconfig.test.json",
     "test:unit": "vitest run test/unit",
     "pretest:integration": "node scripts/build.js",
     "test:integration": "vitest run test/integration",