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 235458a2df2f..63546417014e 100644
--- a/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
@@ -18,7 +18,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -82,8 +86,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -248,8 +254,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -259,10 +267,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -274,8 +289,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -414,7 +431,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -422,7 +445,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -430,7 +457,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -438,7 +469,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/others/typescript-fetch/additional-properties-in-multipart-issue/runtime.ts b/samples/client/others/typescript-fetch/additional-properties-in-multipart-issue/runtime.ts
index cc66cbfbb3af..4222faa85838 100644
--- a/samples/client/others/typescript-fetch/additional-properties-in-multipart-issue/runtime.ts
+++ b/samples/client/others/typescript-fetch/additional-properties-in-multipart-issue/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 cc66cbfbb3af..4222faa85838 100644
--- a/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts
+++ b/samples/client/others/typescript-fetch/infinite-recursion-issue/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/others/typescript-fetch/multipart-file-array/runtime.ts b/samples/client/others/typescript-fetch/multipart-file-array/runtime.ts
index a49c6563b888..255e5d8c577a 100644
--- a/samples/client/others/typescript-fetch/multipart-file-array/runtime.ts
+++ b/samples/client/others/typescript-fetch/multipart-file-array/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 8aa237368f4f..cbde4458d1f1 100644
--- a/samples/client/others/typescript-fetch/self-import-issue/runtime.ts
+++ b/samples/client/others/typescript-fetch/self-import-issue/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 a9a8ee84339c..3a983be816e3 100644
--- a/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/allOf-nullable/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 a9a8ee84339c..3a983be816e3 100644
--- a/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/allOf-readonly/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 e52a36947b03..24431db21777 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/petstore/typescript-fetch/builds/default/runtime.ts b/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
index 3389e4beb1cc..cb8aec2230cb 100644
--- a/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts b/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
index 2d2f267ce4a8..21a0212700f8 100644
--- a/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/enum/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/petstore/typescript-fetch/builds/kebab-case/runtime.ts b/samples/client/petstore/typescript-fetch/builds/kebab-case/runtime.ts
index e52a36947b03..24431db21777 100644
--- a/samples/client/petstore/typescript-fetch/builds/kebab-case/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/kebab-case/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 100644
--- a/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/multiple-parameters/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
diff --git a/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts b/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
index 8c8a505df958..fbdf395d2acc 100644
--- a/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/oneOf/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 e52a36947b03..24431db21777 100644
--- a/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 100644
--- a/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/validation-attributes/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/with-interfaces/runtime.ts
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 3389e4beb1cc..cb8aec2230cb 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 2d2f267ce4a8..21a0212700f8 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -422,7 +439,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -430,7 +453,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -438,7 +465,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -446,7 +477,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();
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 45dfc650f077..d1fd8a87f44f 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
@@ -28,7 +28,11 @@ export interface ConfigurationParameters {
 }
 
 export class Configuration {
-    constructor(private configuration: ConfigurationParameters = {}) {}
+    private configuration: ConfigurationParameters;
+
+    constructor(configuration: ConfigurationParameters = {}) {
+        this.configuration = configuration;
+    }
 
     set config(configuration: Configuration) {
         this.configuration = configuration;
@@ -92,8 +96,10 @@ export class BaseAPI {
 
     private static readonly jsonRegex = /^(:?application\/json|[^;/ \t]+\/[^;/ \t]+[+]json)[ \t]*(:?;.*)?$/i;
     private middleware: Middleware[];
+    protected configuration: Configuration;
 
-    constructor(protected configuration = DefaultConfig) {
+    constructor(configuration: Configuration = DefaultConfig) {
+        this.configuration = configuration;
         this.middleware = configuration.middleware;
     }
 
@@ -258,8 +264,10 @@ function isFormData(value: any): value is FormData {
 
 export class ResponseError extends Error {
     override name: "ResponseError" = "ResponseError";
-    constructor(public response: Response, msg?: string) {
+    response: Response;
+    constructor(response: Response, msg?: string) {
         super(msg);
+        this.response = response;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -269,10 +277,17 @@ export class ResponseError extends Error {
     }
 }
 
+// `cause` is declared through an interface so that it stays compatible with lib targets
+// that already declare `Error.cause` (ES2022+) as well as the ones that do not
+export interface FetchError {
+    cause: Error;
+}
+
 export class FetchError extends Error {
     override name: "FetchError" = "FetchError";
-    constructor(public cause: Error, msg?: string) {
+    constructor(cause: Error, msg?: string) {
         super(msg);
+        this.cause = cause;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -284,8 +299,10 @@ export class FetchError extends Error {
 
 export class RequiredError extends Error {
     override name: "RequiredError" = "RequiredError";
-    constructor(public field: string, msg?: string) {
+    field: string;
+    constructor(field: string, msg?: string) {
         super(msg);
+        this.field = field;
 
         // restore prototype chain
         const actualProto = new.target.prototype;
@@ -410,7 +427,13 @@ export interface ResponseTransformer<T> {
 }
 
 export class JSONApiResponse<T> {
-    constructor(public raw: Response, private transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {}
+    raw: Response;
+    private transformer: ResponseTransformer<T>;
+
+    constructor(raw: Response, transformer: ResponseTransformer<T> = (jsonValue: any) => jsonValue) {
+        this.raw = raw;
+        this.transformer = transformer;
+    }
 
     async value(): Promise<T> {
         return this.transformer(await this.raw.json());
@@ -418,7 +441,11 @@ export class JSONApiResponse<T> {
 }
 
 export class VoidApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<void> {
         return undefined;
@@ -426,7 +453,11 @@ export class VoidApiResponse {
 }
 
 export class BlobApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<Blob> {
         return await this.raw.blob();
@@ -434,7 +465,11 @@ export class BlobApiResponse {
 }
 
 export class TextApiResponse {
-    constructor(public raw: Response) {}
+    raw: Response;
+
+    constructor(raw: Response) {
+        this.raw = raw;
+    }
 
     async value(): Promise<string> {
         return await this.raw.text();