diff --git a/.github/workflows/x-tests.yml b/.github/workflows/x-tests.yml
index 9e8b1c7d..c08c4095 100644
--- a/.github/workflows/x-tests.yml
+++ b/.github/workflows/x-tests.yml
@@ -34,6 +34,12 @@ jobs:
       - name: Run apps/x Vitest suites
         run: npm test
 
+      # Typechecks with the dev tsconfigs, which include test files —
+      # the build tsconfigs exclude them and vitest strips types without
+      # checking, so this is the only gate that sees type errors in tests.
+      - name: Typecheck apps/x packages
+        run: npm run typecheck
+
   apps-x-electron-package:
     name: apps/x Electron package smoke test
     runs-on: ubuntu-latest
diff --git a/CLAUDE.md b/CLAUDE.md
index e0989688..a5fe24c8 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -139,6 +139,7 @@ Long-form docs for specific features. Read the relevant file before making chang
 ### Verify compilation
 ```bash
 cd apps/x && npm run deps && npm run lint
+cd apps/x && npm run typecheck   # dev tsconfigs — the only gate that typechecks *.test.ts
 ```
 
 ## Tech Stack
diff --git a/apps/x/apps/renderer/package.json b/apps/x/apps/renderer/package.json
index 0a8c9f9f..c0ad3480 100644
--- a/apps/x/apps/renderer/package.json
+++ b/apps/x/apps/renderer/package.json
@@ -5,6 +5,7 @@
   "scripts": {
     "dev": "vite",
     "build": "tsc -b && vite build",
+    "typecheck": "tsc -b",
     "lint": "eslint .",
     "preview": "vite preview",
     "test": "vitest run",
diff --git a/apps/x/package.json b/apps/x/package.json
index d0931dc7..fbead12c 100644
--- a/apps/x/package.json
+++ b/apps/x/package.json
@@ -16,7 +16,11 @@
     "test": "npm run shared && npm run test:shared && npm run test:core && npm run test:renderer",
     "test:shared": "cd packages/shared && npm test",
     "test:core": "cd packages/core && npm test",
-    "test:renderer": "cd apps/renderer && npm test"
+    "test:renderer": "cd apps/renderer && npm test",
+    "typecheck": "npm run shared && npm run typecheck:shared && npm run typecheck:core && npm run typecheck:renderer",
+    "typecheck:shared": "cd packages/shared && npm run typecheck",
+    "typecheck:core": "cd packages/core && npm run typecheck",
+    "typecheck:renderer": "cd apps/renderer && npm run typecheck"
   },
   "devDependencies": {
     "@eslint/js": "^9.39.2",
diff --git a/apps/x/packages/core/package.json b/apps/x/packages/core/package.json
index 5bd6d9b5..80b5b54d 100644
--- a/apps/x/packages/core/package.json
+++ b/apps/x/packages/core/package.json
@@ -7,6 +7,7 @@
   "scripts": {
     "build": "rm -rf dist && tsc -p tsconfig.build.json",
     "dev": "tsc -w -p tsconfig.build.json",
+    "typecheck": "tsc --noEmit -p tsconfig.json",
     "test": "vitest run",
     "test:watch": "vitest",
     "inspect-turn": "node dist/runtime/turns/inspect-cli.js",
diff --git a/apps/x/packages/shared/package.json b/apps/x/packages/shared/package.json
index 31f99cdd..982f99dc 100644
--- a/apps/x/packages/shared/package.json
+++ b/apps/x/packages/shared/package.json
@@ -7,6 +7,7 @@
   "scripts": {
     "build": "rm -rf dist && tsc -p tsconfig.build.json",
     "dev": "tsc -w",
+    "typecheck": "tsc --noEmit -p tsconfig.json",
     "test": "vitest run",
     "test:watch": "vitest"
   },