diff --git a/samples/client/others/typescript-angular/builds/composed-schemas-tagged-unions/api.base.service.ts b/samples/client/others/typescript-angular/builds/composed-schemas-tagged-unions/api.base.service.ts
index f93aee53b880..5800e940ea64 100644
--- a/samples/client/others/typescript-angular/builds/composed-schemas-tagged-unions/api.base.service.ts
+++ b/samples/client/others/typescript-angular/builds/composed-schemas-tagged-unions/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/others/typescript-angular/builds/composed-schemas/api.base.service.ts b/samples/client/others/typescript-angular/builds/composed-schemas/api.base.service.ts
index f93aee53b880..5800e940ea64 100644
--- a/samples/client/others/typescript-angular/builds/composed-schemas/api.base.service.ts
+++ b/samples/client/others/typescript-angular/builds/composed-schemas/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v12-oneOf/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v12-oneOf/builds/default/api.base.service.ts
index 47200d0aebd7..9ed72856f876 100644
--- a/samples/client/petstore/typescript-angular-v12-oneOf/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v12-oneOf/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v12-provided-in-any/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/api.base.service.ts b/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v12-provided-in-root/builds/with-npm/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v13-oneOf/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v13-oneOf/builds/default/api.base.service.ts
index 47200d0aebd7..9ed72856f876 100644
--- a/samples/client/petstore/typescript-angular-v13-oneOf/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v13-oneOf/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v13-provided-in-any/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v13-provided-in-any/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v13-provided-in-any/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v13-provided-in-any/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/with-npm/api.base.service.ts b/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/with-npm/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/with-npm/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v13-provided-in-root/builds/with-npm/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v14-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v14-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v14-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v14-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v14-query-param-object-format/api.base.service.ts b/samples/client/petstore/typescript-angular-v14-query-param-object-format/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v14-query-param-object-format/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v14-query-param-object-format/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v15-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v15-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v15-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v15-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/deep-object/api.base.service.ts b/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/deep-object/api.base.service.ts
new file mode 100644
index 000000000000..c78251fdde1d
--- /dev/null
+++ b/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/deep-object/api.base.service.ts
@@ -0,0 +1,83 @@
+/**
+ * deepobject-query
+ *
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+import { HttpHeaders, HttpParams, HttpParameterCodec } from '@angular/common/http';
+import { CustomHttpParameterCodec } from './encoder';
+import { Configuration } from './configuration';
+
+export class BaseService {
+    protected basePath = 'http://localhost';
+    public defaultHeaders = new HttpHeaders();
+    public configuration: Configuration;
+    public encoder: HttpParameterCodec;
+
+    constructor(basePath?: string|string[], configuration?: Configuration) {
+        this.configuration = configuration || new Configuration();
+        if (typeof this.configuration.basePath !== 'string') {
+            const firstBasePath = Array.isArray(basePath) ? basePath[0] : undefined;
+            if (firstBasePath != undefined) {
+                basePath = firstBasePath;
+            }
+
+            if (typeof basePath !== 'string') {
+                basePath = this.basePath;
+            }
+            this.configuration.basePath = basePath;
+        }
+        this.encoder = this.configuration.encoder || new CustomHttpParameterCodec();
+    }
+
+    protected canConsumeForm(consumes: string[]): boolean {
+        return consumes.indexOf('multipart/form-data') !== -1;
+    }
+
+    protected addToHttpParams(httpParams: HttpParams, value: any, key?: string, isDeep: boolean = false): HttpParams {
+        // If the value is an object (but not a Date), recursively add its keys.
+        if (typeof value === 'object' && !(value instanceof Date)) {
+            return this.addToHttpParamsRecursive(httpParams, value, isDeep ? key : undefined, isDeep);
+        }
+        return this.addToHttpParamsRecursive(httpParams, value, key);
+    }
+
+    protected addToHttpParamsRecursive(httpParams: HttpParams, value?: any, key?: string, isDeep: boolean = false): HttpParams {
+        if (value === null || value === undefined) {
+            return httpParams;
+        }
+        if (typeof value === 'object') {
+            // If JSON format is preferred, key must be provided.
+            if (key != null) {
+                return isDeep
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
+                        httpParams,
+                    )
+                    : httpParams.append(key, JSON.stringify(value));
+            }
+            // Otherwise, if it's an array, add each element.
+            if (Array.isArray(value)) {
+                value.forEach(elem => httpParams = this.addToHttpParamsRecursive(httpParams, elem, key));
+            } else if (value instanceof Date) {
+                if (key != null) {
+                    httpParams = httpParams.append(key, value.toISOString());
+                } else {
+                    throw Error("key may not be null if value is Date");
+                }
+            } else {
+                Object.keys(value).forEach(k => {
+                    const paramKey = key ? `${key}.${k}` : k;
+                    httpParams = this.addToHttpParamsRecursive(httpParams, value[k], paramKey);
+                });
+            }
+            return httpParams;
+        } else if (key != null) {
+            return httpParams.append(key, value);
+        }
+        throw Error("key may not be null if value is not object or array");
+    }
+}
diff --git a/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v16-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v17-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v17-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v17-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v17-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v18-provided-in-root/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v18-provided-in-root/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v18-provided-in-root/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v18-provided-in-root/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v19-with-angular-dependency-params/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v19-with-angular-dependency-params/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v19-with-angular-dependency-params/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v19-with-angular-dependency-params/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));
diff --git a/samples/client/petstore/typescript-angular-v19/builds/default/api.base.service.ts b/samples/client/petstore/typescript-angular-v19/builds/default/api.base.service.ts
index f8664864f0ba..e2e57d08322d 100644
--- a/samples/client/petstore/typescript-angular-v19/builds/default/api.base.service.ts
+++ b/samples/client/petstore/typescript-angular-v19/builds/default/api.base.service.ts
@@ -53,8 +53,8 @@ export class BaseService {
             // If JSON format is preferred, key must be provided.
             if (key != null) {
                 return isDeep
-                    ? Object.entries(value as Record<string, any>).reduce(
-                        (hp, [k, v]) => hp.append(`${key}[${k}]`, v),
+                    ? Object.keys(value as Record<string, any>).reduce(
+                        (hp, k) => hp.append(`${key}[${k}]`, value[k]),
                         httpParams,
                     )
                     : httpParams.append(key, JSON.stringify(value));