From ed01f15879d3017aea9b1acf4c0d909088c0f8b1 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 18 Dec 2025 15:00:23 +0000
Subject: [PATCH] Add support for moduleResolution node16 to behave like
 nodenext

Co-authored-by: mrlubos <12529395+mrlubos@users.noreply.github.com>
---
 .../openapi-ts-tests/main/test/clients.test.ts     | 14 ++++++++++++++
 .../main/test/tsconfig/tsconfig.node16.json        |  9 +++++++++
 packages/openapi-ts/src/config/output.ts           |  6 ++++--
 packages/openapi-ts/src/types/output.d.ts          |  8 ++++----
 4 files changed, 31 insertions(+), 6 deletions(-)
 create mode 100644 packages/openapi-ts-tests/main/test/tsconfig/tsconfig.node16.json

diff --git a/packages/openapi-ts-tests/main/test/clients.test.ts b/packages/openapi-ts-tests/main/test/clients.test.ts
index 118a0f1b9..db6252080 100644
--- a/packages/openapi-ts-tests/main/test/clients.test.ts
+++ b/packages/openapi-ts-tests/main/test/clients.test.ts
@@ -159,6 +159,20 @@ for (const client of clients) {
         }),
         description: 'SDK with NodeNext tsconfig',
       },
+      {
+        config: createConfig({
+          output: {
+            path: 'tsconfig-node16-sdk',
+            tsConfigPath: path.join(
+              __dirname,
+              'tsconfig',
+              'tsconfig.node16.json',
+            ),
+          },
+          plugins: [client, '@hey-api/sdk'],
+        }),
+        description: 'SDK with Node16 tsconfig',
+      },
       {
         config: createConfig({
           output: {
diff --git a/packages/openapi-ts-tests/main/test/tsconfig/tsconfig.node16.json b/packages/openapi-ts-tests/main/test/tsconfig/tsconfig.node16.json
new file mode 100644
index 000000000..f905bad0f
--- /dev/null
+++ b/packages/openapi-ts-tests/main/test/tsconfig/tsconfig.node16.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "declaration": false,
+    "moduleResolution": "node16",
+    "resolveJsonModule": true,
+    "skipLibCheck": true
+  }
+}
diff --git a/packages/openapi-ts/src/config/output.ts b/packages/openapi-ts/src/config/output.ts
index ddac601bf..846ae2474 100644
--- a/packages/openapi-ts/src/config/output.ts
+++ b/packages/openapi-ts/src/config/output.ts
@@ -50,8 +50,10 @@ export const getOutput = (userConfig: UserConfig): Config['output'] => {
   output.tsConfig = loadTsConfig(findTsConfigPath(output.tsConfigPath));
   if (
     output.importFileExtension === undefined &&
-    output.tsConfig?.options.moduleResolution ===
-      ts.ModuleResolutionKind.NodeNext
+    (output.tsConfig?.options.moduleResolution ===
+      ts.ModuleResolutionKind.NodeNext ||
+      output.tsConfig?.options.moduleResolution ===
+        ts.ModuleResolutionKind.Node16)
   ) {
     output.importFileExtension = '.js';
   }
diff --git a/packages/openapi-ts/src/types/output.d.ts b/packages/openapi-ts/src/types/output.d.ts
index 471bda9ef..7d5dc639b 100644
--- a/packages/openapi-ts/src/types/output.d.ts
+++ b/packages/openapi-ts/src/types/output.d.ts
@@ -70,8 +70,8 @@ export type UserOutput = {
   /**
    * If specified, this will be the file extension used when importing
    * other modules. By default, we don't add a file extension and let the
-   * runtime resolve it. If you're using moduleResolution `nodenext`, we
-   * default to `.js`.
+   * runtime resolve it. If you're using moduleResolution `nodenext` or
+   * `node16`, we default to `.js`.
    *
    * @default undefined
    */
@@ -170,8 +170,8 @@ export type Output = {
   /**
    * If specified, this will be the file extension used when importing
    * other modules. By default, we don't add a file extension and let the
-   * runtime resolve it. If you're using moduleResolution `nodenext`, we
-   * default to `.js`.
+   * runtime resolve it. If you're using moduleResolution `nodenext` or
+   * `node16`, we default to `.js`.
    */
   importFileExtension: ImportFileExtensions | (string & {}) | null | undefined;
   /**
-- 
2.51.2