From 8feb1f8377f2524d6b9f36255887ba0def75338b Mon Sep 17 00:00:00 2001
From: Jehiah Czebotar <jehiah@gmail.com>
Date: Fri, 7 Nov 2025 15:59:48 -0500
Subject: [PATCH 1/2] fix(typescript-fetch): ResponseError prototype chain

---
 .../typescript-fetch/runtime.mustache          | 18 ++++++++++++++++++
 .../tests/default/test/PetApi.ts               |  9 ++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache b/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
index 8cfe7948e922..acd04c40d5eb 100644
--- a/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
@@ -251,6 +251,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -258,6 +264,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -265,6 +277,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/tests/default/test/PetApi.ts b/samples/client/petstore/typescript-fetch/tests/default/test/PetApi.ts
index c452573699d5..adbbed1dd340 100644
--- a/samples/client/petstore/typescript-fetch/tests/default/test/PetApi.ts
+++ b/samples/client/petstore/typescript-fetch/tests/default/test/PetApi.ts
@@ -1,5 +1,5 @@
 import { expect } from 'chai';
-import { PetApi, Pet, PetStatusEnum, Category } from '@swagger/typescript-fetch-petstore';
+import { PetApi, Pet, PetStatusEnum, Category, ResponseError } from '@swagger/typescript-fetch-petstore';
 import { config } from '../configuration';
 
 describe('PetApi', () => {
@@ -49,6 +49,13 @@ describe('PetApi', () => {
                 });
             });
 
+            it('instanceof ResponseError not Error', () => {
+                const response = new Response();
+                const err = new ResponseError(response, 'test error message');
+                expect(err instanceof ResponseError).to.be.true;
+                expect(err instanceof Error).to.be.true;
+            });
+
         });
     }
 

From 5c5ead1d6f9f5559f4c7ebd93d4d019ef8a2e741 Mon Sep 17 00:00:00 2001
From: Jehiah Czebotar <jehiah@gmail.com>
Date: Thu, 19 Feb 2026 10:17:16 -0500
Subject: [PATCH 2/2] samples/*/typescript-fetch: re-generate runtime.ts

---
 .../infinite-recursion-issue/runtime.ts        | 18 ++++++++++++++++++
 .../self-import-issue/runtime.ts               | 18 ++++++++++++++++++
 .../builds/allOf-nullable/runtime.ts           | 18 ++++++++++++++++++
 .../builds/allOf-readonly/runtime.ts           | 18 ++++++++++++++++++
 .../builds/default-v3.0/runtime.ts             | 18 ++++++++++++++++++
 .../typescript-fetch/builds/default/runtime.ts | 18 ++++++++++++++++++
 .../typescript-fetch/builds/enum/runtime.ts    | 18 ++++++++++++++++++
 .../builds/es6-target/src/runtime.ts           | 18 ++++++++++++++++++
 .../builds/multiple-parameters/runtime.ts      | 18 ++++++++++++++++++
 .../typescript-fetch/builds/oneOf/runtime.ts   | 18 ++++++++++++++++++
 .../prefix-parameter-interfaces/src/runtime.ts | 18 ++++++++++++++++++
 .../builds/sagas-and-records/src/runtime.ts    | 18 ++++++++++++++++++
 .../builds/snakecase-discriminator/runtime.ts  | 18 ++++++++++++++++++
 .../builds/validation-attributes/runtime.ts    | 18 ++++++++++++++++++
 .../builds/with-interfaces/runtime.ts          | 18 ++++++++++++++++++
 .../builds/with-npm-version/src/runtime.ts     | 18 ++++++++++++++++++
 .../builds/with-string-enums/runtime.ts        | 18 ++++++++++++++++++
 .../without-runtime-checks/src/runtime.ts      | 18 ++++++++++++++++++
 18 files changed, 324 insertions(+)

diff --git a/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts b/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts
index 492083e7c372..f59a24beaf1c 100644
--- a/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts
+++ b/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/others/typescript-fetch/self-import-issue/runtime.ts b/samples/client/others/typescript-fetch/self-import-issue/runtime.ts
index c3175f3bac29..15e78cb9c282 100644
--- a/samples/client/others/typescript-fetch/self-import-issue/runtime.ts
+++ b/samples/client/others/typescript-fetch/self-import-issue/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts b/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts
index c9b10a3dc885..d14bf5837c37 100644
--- a/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts b/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts
index c9b10a3dc885..d14bf5837c37 100644
--- a/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/default-v3.0/runtime.ts b/samples/client/petstore/typescript-fetch/builds/default-v3.0/runtime.ts
index 6d3d965df11d..0296a2863f5b 100644
--- a/samples/client/petstore/typescript-fetch/builds/default-v3.0/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default-v3.0/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/default/runtime.ts b/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts b/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
index 8095de29bc32..c4c63d2df81f 100644
--- a/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/es6-target/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/es6-target/src/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/es6-target/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/es6-target/src/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts b/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts b/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
index c807c6354f8d..859365935e74 100644
--- a/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/prefix-parameter-interfaces/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/prefix-parameter-interfaces/src/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/prefix-parameter-interfaces/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/prefix-parameter-interfaces/src/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/sagas-and-records/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/sagas-and-records/src/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/sagas-and-records/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/sagas-and-records/src/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts b/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts
index 6d3d965df11d..0296a2863f5b 100644
--- a/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts b/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts b/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/with-npm-version/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/with-npm-version/src/runtime.ts
index 3f125c3b0601..917967f1d078 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-npm-version/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/with-npm-version/src/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/with-string-enums/runtime.ts b/samples/client/petstore/typescript-fetch/builds/with-string-enums/runtime.ts
index 8095de29bc32..c4c63d2df81f 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-string-enums/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/with-string-enums/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
diff --git a/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
index 1d27e4d7e3ba..7e6bbc0079ca 100644
--- a/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
@@ -261,6 +261,12 @@ export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
     constructor(public response: Response, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -268,6 +274,12 @@ export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
     constructor(public cause: Error, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }
 
@@ -275,6 +287,12 @@ export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
     constructor(public field: string, msg?: string) {
         super(msg);
+
+        // restore prototype chain
+        const actualProto = new.target.prototype;
+        if (Object.setPrototypeOf) {
+            Object.setPrototypeOf(this, actualProto);
+        }
     }
 }