diff --git a/npm/ng-packs/packages/schematics/src/tests/get-param-value-name.spec.ts b/npm/ng-packs/packages/schematics/src/tests/get-param-value-name.spec.ts
new file mode 100644
index 0000000000..6defc9ddfa
--- /dev/null
+++ b/npm/ng-packs/packages/schematics/src/tests/get-param-value-name.spec.ts
@@ -0,0 +1,26 @@
+import { describe, expect, it } from 'vitest';
+import { getParamValueName } from '../utils/methods';
+
+describe('getParamValueName', () => {
+  it('should navigate nested params with optional chaining', () => {
+    expect(getParamValueName('NestedFilter.SomeField', 'input')).toBe(
+      'input?.nestedFilter?.someField',
+    );
+  });
+
+  it('should optional-chain every level of a deeper nested param', () => {
+    expect(getParamValueName('Filter.Inner.Value', 'input')).toBe('input?.filter?.inner?.value');
+  });
+
+  it('should not add optional chaining for a non-nested param', () => {
+    expect(getParamValueName('someField', 'input')).toBe('input.someField');
+  });
+
+  it('should keep bracket access for a non-nested param that needs quoting', () => {
+    expect(getParamValueName('some-field', 'input')).toBe("input['some-field']");
+  });
+
+  it('should quote a nested segment that needs quoting and still optional-chain', () => {
+    expect(getParamValueName('Filter.some-field', 'input')).toBe("input?.filter?.['some-field']");
+  });
+});
diff --git a/npm/ng-packs/packages/schematics/src/tests/proxy-nested-optional-chaining.spec.ts b/npm/ng-packs/packages/schematics/src/tests/proxy-nested-optional-chaining.spec.ts
new file mode 100644
index 0000000000..5c4bee4540
--- /dev/null
+++ b/npm/ng-packs/packages/schematics/src/tests/proxy-nested-optional-chaining.spec.ts
@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest';
+import { createActionToBodyMapper } from '../utils/service';
+import { eBindingSourceId } from '../enums';
+import { Action } from '../models/api-definition';
+
+// Exercises the real proxy-generation pipeline (registerActionParameter -> getParamValueName ->
+// Body.params) for a flattened nullable nested query param, the case reported in #25176.
+describe('proxy generation - nested nullable query param', () => {
+  const action = {
+    uniqueName: 'GetListAsync',
+    name: 'GetListAsync',
+    httpMethod: 'GET',
+    url: 'api/app/my',
+    supportedVersions: [],
+    parametersOnMethod: [],
+    parameters: [
+      {
+        nameOnMethod: 'input',
+        name: 'NestedFilter.SomeField',
+        jsonName: null,
+        type: 'System.String',
+        typeSimple: 'string',
+        isOptional: true,
+        defaultValue: null,
+        constraintTypes: null,
+        bindingSourceId: eBindingSourceId.Query,
+        descriptorName: 'input',
+      },
+    ],
+    returnValue: { type: 'System.Void', typeSimple: 'void' },
+  } as unknown as Action;
+
+  it('emits optional chaining in the generated params object', () => {
+    const body = createActionToBodyMapper()(action);
+
+    expect(body.params).toContain(
+      '["NestedFilter.SomeField"]: input?.nestedFilter?.someField',
+    );
+  });
+});
diff --git a/npm/ng-packs/packages/schematics/src/utils/methods.ts b/npm/ng-packs/packages/schematics/src/utils/methods.ts
index 6d31903a78..246c86541f 100644
--- a/npm/ng-packs/packages/schematics/src/utils/methods.ts
+++ b/npm/ng-packs/packages/schematics/src/utils/methods.ts
@@ -7,7 +7,9 @@ export const getParamName = (paramName: string) =>
 export const getParamValueName = (paramName: string, descriptorName: string) => {
   if (paramName.includes('.')) {
     const splitted = paramName.split('.');
-    const param = splitted.map(x => (shouldQuote(x) ? `[${x}]` : `.${camel(x)}`)).join('');
+    // Flattened nested query params: any intermediate object may be absent at runtime, and
+    // nested members are typed as `T | null`, so navigate them with optional chaining (`?.`).
+    const param = splitted.map(x => (shouldQuote(x) ? `?.['${x}']` : `?.${camel(x)}`)).join('');
     return `${descriptorName}${param}`;
   }
   if (shouldQuote(paramName)) {