diff --git a/examples/basic-app/app/types/wrnexus.generated.api-checks.ts b/examples/basic-app/app/types/wrnexus.generated.api-checks.ts
new file mode 100644
index 00000000..372018ab
--- /dev/null
+++ b/examples/basic-app/app/types/wrnexus.generated.api-checks.ts
@@ -0,0 +1,7 @@
+// AUTO-GENERATED by `wrnexus generate types` - do not edit.
+//
+// Type-only assertions for sectioned `api` blocks. Kept as a real .ts file (not
+// wrnexus.generated.d.ts) because `skipLibCheck` exempts .d.ts contents from being
+// checked; this file is compiled and checked normally by the project's own tsc.
+
+export {};
diff --git a/examples/basic-app/app/types/wrnexus.generated.d.ts b/examples/basic-app/app/types/wrnexus.generated.d.ts
index 537a1c99..d897d761 100644
--- a/examples/basic-app/app/types/wrnexus.generated.d.ts
+++ b/examples/basic-app/app/types/wrnexus.generated.d.ts
@@ -57,4 +57,8 @@ declare namespace WRNexusGenerated {
     "welcome-email": QueuePayload<(typeof import("../queues/welcome-email.ts"))["default"]>;
   }
   type ApplicationConfig = (typeof import("../../wrnexus.config.ts"))["default"];
+  type AssertAssignable<Actual, Expected> = [Actual] extends [Expected] ? true : false;
+  type __wrn_expect_true<T extends true> = T;
+  type ApiInput<P extends ApiRoute, M> = ApiContracts[P][M]["input"];
+  type ApiOutput<P extends ApiRoute, M> = ApiContracts[P][M]["output"];
 }
diff --git a/packages/cli/src/types.ts b/packages/cli/src/types.ts
index 2456f924..dbd653f2 100644
--- a/packages/cli/src/types.ts
+++ b/packages/cli/src/types.ts
@@ -125,7 +125,7 @@ function apiBlockAssertions(pages: { path: string; ast: PageAst }[], apiContract
         : "Record<string, never>";
 
       lines.push(
-        `  type __wrn_api_check_${block.name} = __wrn_expect_true<AssertAssignable<${shape}, ApiInput<${JSON.stringify(
+        `type __wrn_api_check_${block.name} = WRNexusGenerated.__wrn_expect_true<WRNexusGenerated.AssertAssignable<${shape}, WRNexusGenerated.ApiInput<${JSON.stringify(
           block.path,
         )}, ${JSON.stringify(block.method)}>>>;`,
       );
@@ -262,12 +262,23 @@ declare namespace WRNexusGenerated {
   type __wrn_expect_true<T extends true> = T;
   type ApiInput<P extends ApiRoute, M> = ApiContracts[P][M]["input"];
   type ApiOutput<P extends ApiRoute, M> = ApiContracts[P][M]["output"];
-${apiBlockAssertions(pageAsts, apiContracts)}
 }
 `;
   mkdirSync(typeDir, { recursive: true });
   const output = join(typeDir, "wrnexus.generated.d.ts");
   writeFileSync(output, code, "utf8");
+  // `.d.ts` contents are exempt from checking under `skipLibCheck: true` (set in the
+  // repo/app tsconfig), so the per-block assertions are written into a real `.ts` file
+  // instead — only genuine `.ts`/`.tsx` sources are compiled and checked.
+  const apiChecksCode = `// AUTO-GENERATED by \`wrnexus generate types\` - do not edit.
+//
+// Type-only assertions for sectioned \`api\` blocks. Kept as a real .ts file (not
+// wrnexus.generated.d.ts) because \`skipLibCheck\` exempts .d.ts contents from being
+// checked; this file is compiled and checked normally by the project's own tsc.
+${apiBlockAssertions(pageAsts, apiContracts)}
+export {};
+`;
+  writeFileSync(join(typeDir, "wrnexus.generated.api-checks.ts"), apiChecksCode, "utf8");
   writePluginArtifacts(root, pluginContributions);
   return {
     file: relative(root, output).replace(/\\/g, "/"),
diff --git a/packages/cli/test/api-block-types.test.ts b/packages/cli/test/api-block-types.test.ts
index 5bb2d712..1cb2708e 100644
--- a/packages/cli/test/api-block-types.test.ts
+++ b/packages/cli/test/api-block-types.test.ts
@@ -51,15 +51,19 @@ test("emits the ApiInput, ApiOutput and AssertAssignable helpers", () => {
   );
 });
 
+// The per-block assertions live in a plain .ts file, not the .d.ts: `skipLibCheck: true`
+// (set repo-wide) exempts .d.ts *contents* from being checked at all, so a `.d.ts` can
+// never actually enforce anything here. A real .ts file under app/ is compiled and
+// checked normally.
 test("emits one assertion per sectioned block, naming its route and method", () => {
   const root = fixture(BLOCK);
   generateApplicationTypes(root);
-  const generated = readFileSync(join(root, "app/types/wrnexus.generated.d.ts"), "utf8");
+  const checks = readFileSync(join(root, "app/types/wrnexus.generated.api-checks.ts"), "utf8");
 
-  expect(generated).toContain("__wrn_api_check_searchUsers");
-  expect(generated).toContain('ApiInput<"/api/users", "POST">');
-  expect(generated).toContain("name?: string");
-  expect(generated).toContain("age?: number");
+  expect(checks).toContain("__wrn_api_check_searchUsers");
+  expect(checks).toContain('WRNexusGenerated.ApiInput<"/api/users", "POST">');
+  expect(checks).toContain("name?: string");
+  expect(checks).toContain("age?: number");
 });
 
 test("a legacy bare-body block produces no assertion", () => {
@@ -67,7 +71,16 @@ test("a legacy bare-body block produces no assertion", () => {
       return users.length
     }`);
   generateApplicationTypes(root);
-  const generated = readFileSync(join(root, "app/types/wrnexus.generated.d.ts"), "utf8");
+  const checks = readFileSync(join(root, "app/types/wrnexus.generated.api-checks.ts"), "utf8");
 
-  expect(generated).not.toContain("__wrn_api_check_legacyUsers");
+  expect(checks).not.toContain("__wrn_api_check_legacyUsers");
+});
+
+test("the api-checks file has no runtime code and is a module", () => {
+  const root = fixture(BLOCK);
+  generateApplicationTypes(root);
+  const checks = readFileSync(join(root, "app/types/wrnexus.generated.api-checks.ts"), "utf8");
+
+  expect(checks).toContain("AUTO-GENERATED");
+  expect(checks.trim().endsWith("export {};")).toBe(true);
 });
diff --git a/scripts/check-generated-types.ts b/scripts/check-generated-types.ts
index eed217c6..e02e5320 100644
--- a/scripts/check-generated-types.ts
+++ b/scripts/check-generated-types.ts
@@ -8,6 +8,7 @@ const scratchParent = join(root, ".wrnexus-type-check");
 const scratch = mkdtempSync(`${scratchParent}-`);
 const generated = [
   join("app", "types", "wrnexus.generated.d.ts"),
+  join("app", "types", "wrnexus.generated.api-checks.ts"),
   join("app", "types", "wrnexus.plugins.generated.d.ts"),
 ];