diff --git a/packages/dts-generator/src/phases/json-fixer.ts b/packages/dts-generator/src/phases/json-fixer.ts
index 0ac8d17e..f01e05b2 100644
--- a/packages/dts-generator/src/phases/json-fixer.ts
+++ b/packages/dts-generator/src/phases/json-fixer.ts
@@ -49,7 +49,7 @@ function mergeOverlays(
     );
   }
 
-  const mapLikeProperties = new Set(["methods", "properties"]);
+  const mapLikeProperties = new Set(["methods", "properties", "events"]);
 
   function mergeProp(
     obj: { [key: string]: unknown },
diff --git a/packages/dts-generator/src/types/api-json.d.ts b/packages/dts-generator/src/types/api-json.d.ts
index c17a35a4..4a9de6ed 100644
--- a/packages/dts-generator/src/types/api-json.d.ts
+++ b/packages/dts-generator/src/types/api-json.d.ts
@@ -344,6 +344,7 @@ export interface ObjEvent {
   examples?: Examples;
   references?: References;
   allowedFor?: string[];
+  explicit?: boolean;
 }
 export interface Ui5Metadata {
   stereotype?:
@@ -453,6 +454,7 @@ export interface Ui5Event {
   allowPreventDefault?: boolean;
   enableEventBubbling?: boolean;
   allowedFor?: string[];
+  explicit?: boolean;
 }
 export interface EnumProperty {
   name: string;
diff --git a/packages/dts-generator/src/utils/json-event-parameter-interfaces.ts b/packages/dts-generator/src/utils/json-event-parameter-interfaces.ts
index a9d1c643..32f93b19 100644
--- a/packages/dts-generator/src/utils/json-event-parameter-interfaces.ts
+++ b/packages/dts-generator/src/utils/json-event-parameter-interfaces.ts
@@ -71,20 +71,22 @@ function createEventParameterInterfaces(
     };
   };
 
-  function buildProperties(srcProperties) {
+  function buildProperties(srcProperties, explicit?: boolean) {
     const transformedProperties = [];
     for (let propertyName in srcProperties) {
       const prop = srcProperties[propertyName];
-      transformedProperties.push(
-        addJsDocProps(
-          {
-            name: prop.name,
-            type: prop.type,
-            visibility: "public", // prop.visibility,
-          },
-          prop,
-        ),
+      const transformed = addJsDocProps(
+        {
+          name: prop.name,
+          type: prop.type,
+          visibility: "public", // prop.visibility,
+        },
+        prop,
       );
+      if (explicit && prop.optional === false) {
+        transformed.optional = false;
+      }
+      transformedProperties.push(transformed);
     }
     return transformedProperties;
   }
@@ -320,7 +322,10 @@ function createEventParameterInterfaces(
           }
 
           // now add the parameters to the interface
-          const parameters = buildProperties(allParameters);
+          const parameters = buildProperties(
+            allParameters,
+            event.explicit === true,
+          );
           eventParametersInterface.properties = parameters;
           eventParametersInterface.description = `Parameters of the ${symbol.basename}#${event.name} event.`;
           if (event.deprecated) {
diff --git a/test-packages/openui5-snapshot-test/test/explicit-event-params-spec.js b/test-packages/openui5-snapshot-test/test/explicit-event-params-spec.js
new file mode 100644
index 00000000..3bffd6f6
--- /dev/null
+++ b/test-packages/openui5-snapshot-test/test/explicit-event-params-spec.js
@@ -0,0 +1,1181 @@
+"use strict";
+
+const assert = require("assert");
+
+describe("explicit event parameters", function () {
+  this.timeout(10000);
+
+  let generateFromObjects;
+
+  before(async () => {
+    ({ generateFromObjects } = await import("@ui5/dts-generator"));
+  });
+
+  const directives = {
+    badSymbols: [],
+    badMethods: [],
+    badInterfaces: [],
+    typeTyposMap: {},
+    namespacesToInterfaces: {},
+    forwardDeclarations: {},
+    fqnToIgnore: {},
+    overlays: {},
+    deprecatedEnumAliases: {},
+    modulesWithNamedExports: [],
+  };
+
+  function makeEvent(name, parameterProperties, explicit) {
+    const event = {
+      name,
+      visibility: "public",
+      parameters: [
+        {
+          name: "oControlEvent",
+          type: "sap.ui.base.Event",
+          parameterProperties: {
+            getSource: {
+              name: "getSource",
+              type: "sap.ui.base.EventProvider",
+              optional: false,
+            },
+            getParameters: {
+              name: "getParameters",
+              type: "object",
+              optional: false,
+              parameterProperties,
+            },
+          },
+        },
+      ],
+    };
+    if (explicit !== undefined) {
+      event.explicit = explicit;
+    }
+    return event;
+  }
+
+  function findPropertyLine(dtsText, propName) {
+    return dtsText
+      .split("\n")
+      .find(
+        (l) =>
+          l.includes(propName) &&
+          l.includes(":") &&
+          !l.includes("/**") &&
+          !l.includes("*"),
+      );
+  }
+
+  async function generate(apiObject, dependencyApiObjects) {
+    return generateFromObjects({
+      apiObject,
+      dependencyApiObjects,
+      directives,
+    });
+  }
+
+  describe("EventProvider subclass", function () {
+    const baseLibApi = {
+      library: "sap.ui.core",
+      version: "1.0.0",
+      symbols: [
+        {
+          kind: "namespace",
+          name: "sap.ui.base",
+          basename: "base",
+          resource: "sap/ui/base/library.js",
+          module: "sap/ui/base/library",
+          export: "",
+          visibility: "public",
+          description: "",
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.EventProvider",
+          basename: "EventProvider",
+          resource: "sap/ui/base/EventProvider.js",
+          module: "sap/ui/base/EventProvider",
+          export: "",
+          visibility: "public",
+          abstract: true,
+          description: "Base event provider.",
+          methods: [
+            {
+              name: "attachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "oData", type: "object", optional: true },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "detachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "fireEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "mParameters", type: "object", optional: true },
+              ],
+            },
+          ],
+        },
+      ],
+    };
+
+    function makeTestLib(events) {
+      return {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.MyClass",
+            basename: "MyClass",
+            resource: "testlib/MyClass.js",
+            module: "testlib/MyClass",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.base.EventProvider",
+            description: "A test class extending EventProvider.",
+            events,
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+    }
+
+    it("without explicit flag, all event parameters are optional", async () => {
+      const event = makeEvent("change", {
+        selectedItem: {
+          name: "selectedItem",
+          type: "string",
+          optional: false,
+          description: "The selected item.",
+        },
+        value: {
+          name: "value",
+          type: "string",
+          optional: true,
+          description: "The value.",
+        },
+      });
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /selectedItem\?/);
+      assert.match(result.dtsText, /value\?/);
+    });
+
+    it("with explicit: true, non-optional parameters become required", async () => {
+      const event = makeEvent(
+        "change",
+        {
+          selectedItem: {
+            name: "selectedItem",
+            type: "string",
+            optional: false,
+            description: "The selected item.",
+          },
+          value: {
+            name: "value",
+            type: "string",
+            optional: true,
+            description: "The value.",
+          },
+        },
+        true,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      const selectedItemLine = findPropertyLine(result.dtsText, "selectedItem");
+      const valueLine = findPropertyLine(result.dtsText, "value");
+
+      assert.ok(selectedItemLine, "selectedItem should appear in output");
+      assert.ok(valueLine, "value should appear in output");
+      assert.ok(
+        !selectedItemLine.includes("?"),
+        `selectedItem should be required (no '?'), got: "${selectedItemLine.trim()}"`,
+      );
+      assert.ok(
+        valueLine.includes("?"),
+        `value should be optional (has '?'), got: "${valueLine.trim()}"`,
+      );
+    });
+
+    it("with explicit: true, parameters without optional field default to optional", async () => {
+      const event = makeEvent(
+        "press",
+        {
+          source: {
+            name: "source",
+            type: "string",
+            description: "The event source.",
+          },
+        },
+        true,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /source\?/);
+    });
+
+    it("with explicit: true and optional: true, parameter stays optional", async () => {
+      const event = makeEvent(
+        "change",
+        {
+          selectedItem: {
+            name: "selectedItem",
+            type: "string",
+            optional: true,
+            description: "The selected item.",
+          },
+        },
+        true,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /selectedItem\?/);
+    });
+
+    it("with explicit: false, behaves same as no explicit flag", async () => {
+      const event = makeEvent(
+        "change",
+        {
+          selectedItem: {
+            name: "selectedItem",
+            type: "string",
+            optional: false,
+            description: "The selected item.",
+          },
+        },
+        false,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /selectedItem\?/);
+    });
+  });
+
+  describe("Control subclass (extends sap.ui.core.Control)", function () {
+    const baseLibApi = {
+      library: "sap.ui.core",
+      version: "2.0.0",
+      symbols: [
+        {
+          kind: "namespace",
+          name: "sap.ui.base",
+          basename: "base",
+          resource: "sap/ui/base/library.js",
+          module: "sap/ui/base/library",
+          export: "",
+          visibility: "public",
+          description: "",
+        },
+        {
+          kind: "namespace",
+          name: "sap.ui.core",
+          basename: "core",
+          resource: "sap/ui/core/library.js",
+          module: "sap/ui/core/library",
+          export: "",
+          visibility: "public",
+          description: "",
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.EventProvider",
+          basename: "EventProvider",
+          resource: "sap/ui/base/EventProvider.js",
+          module: "sap/ui/base/EventProvider",
+          export: "",
+          visibility: "public",
+          abstract: true,
+          description: "Base event provider.",
+          methods: [
+            {
+              name: "attachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "oData", type: "object", optional: true },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "detachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "fireEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "mParameters", type: "object", optional: true },
+              ],
+            },
+          ],
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.ManagedObject",
+          basename: "ManagedObject",
+          resource: "sap/ui/base/ManagedObject.js",
+          module: "sap/ui/base/ManagedObject",
+          export: "",
+          visibility: "public",
+          extends: "sap.ui.base.EventProvider",
+          description: "Base class for managed objects.",
+          "ui5-metadata": {
+            stereotype: "object",
+          },
+        },
+        {
+          kind: "class",
+          name: "sap.ui.core.Element",
+          basename: "Element",
+          resource: "sap/ui/core/Element.js",
+          module: "sap/ui/core/Element",
+          export: "",
+          visibility: "public",
+          extends: "sap.ui.base.ManagedObject",
+          description: "Base class for UI elements.",
+          "ui5-metadata": {
+            stereotype: "element",
+          },
+        },
+        {
+          kind: "class",
+          name: "sap.ui.core.Control",
+          basename: "Control",
+          resource: "sap/ui/core/Control.js",
+          module: "sap/ui/core/Control",
+          export: "",
+          visibility: "public",
+          extends: "sap.ui.core.Element",
+          description: "Base class for controls.",
+          "ui5-metadata": {
+            stereotype: "control",
+          },
+        },
+      ],
+    };
+
+    function makeTestLib(events) {
+      return {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.MyControl",
+            basename: "MyControl",
+            resource: "testlib/MyControl.js",
+            module: "testlib/MyControl",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.core.Control",
+            description: "A test control extending sap.ui.core.Control.",
+            "ui5-metadata": {
+              stereotype: "control",
+              events: [
+                {
+                  name: "change",
+                  visibility: "public",
+                  description: "Fired when value changes.",
+                  parameters: {
+                    selectedItem: {
+                      name: "selectedItem",
+                      type: "string",
+                      description: "The selected item.",
+                    },
+                  },
+                },
+              ],
+            },
+            events,
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+    }
+
+    it("without explicit flag, all event parameters are optional", async () => {
+      const event = makeEvent("change", {
+        selectedItem: {
+          name: "selectedItem",
+          type: "string",
+          optional: false,
+          description: "The selected item.",
+        },
+      });
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /selectedItem\?/);
+    });
+
+    it("with explicit: true, non-optional parameters become required", async () => {
+      const event = makeEvent(
+        "change",
+        {
+          selectedItem: {
+            name: "selectedItem",
+            type: "string",
+            optional: false,
+            description: "The selected item.",
+          },
+          value: {
+            name: "value",
+            type: "string",
+            optional: true,
+            description: "The value.",
+          },
+        },
+        true,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      const selectedItemLine = findPropertyLine(result.dtsText, "selectedItem");
+      const valueLine = findPropertyLine(result.dtsText, "value");
+
+      assert.ok(selectedItemLine, "selectedItem should appear in output");
+      assert.ok(valueLine, "value should appear in output");
+      assert.ok(
+        !selectedItemLine.includes("?"),
+        `selectedItem should be required (no '?'), got: "${selectedItemLine.trim()}"`,
+      );
+      assert.ok(
+        valueLine.includes("?"),
+        `value should be optional (has '?'), got: "${valueLine.trim()}"`,
+      );
+    });
+
+    it("with explicit: true and optional: true, parameter stays optional", async () => {
+      const event = makeEvent(
+        "change",
+        {
+          selectedItem: {
+            name: "selectedItem",
+            type: "string",
+            optional: true,
+            description: "The selected item.",
+          },
+        },
+        true,
+      );
+
+      const result = await generate(makeTestLib([event]), [baseLibApi]);
+
+      assert.match(result.dtsText, /selectedItem\?/);
+    });
+  });
+
+  describe("overlay merge for events", function () {
+    const baseLibApi = {
+      library: "sap.ui.core",
+      version: "3.0.0",
+      symbols: [
+        {
+          kind: "namespace",
+          name: "sap.ui.base",
+          basename: "base",
+          resource: "sap/ui/base/library.js",
+          module: "sap/ui/base/library",
+          export: "",
+          visibility: "public",
+          description: "",
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.EventProvider",
+          basename: "EventProvider",
+          resource: "sap/ui/base/EventProvider.js",
+          module: "sap/ui/base/EventProvider",
+          export: "",
+          visibility: "public",
+          abstract: true,
+          description: "Base event provider.",
+          methods: [
+            {
+              name: "attachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "oData", type: "object", optional: true },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "detachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "fireEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "mParameters", type: "object", optional: true },
+              ],
+            },
+          ],
+        },
+      ],
+    };
+
+    it("overlay can set explicit: true on an existing event by name", async () => {
+      const apiObject = {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.MyClass",
+            basename: "MyClass",
+            resource: "testlib/MyClass.js",
+            module: "testlib/MyClass",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.base.EventProvider",
+            description: "A test class.",
+            events: [
+              makeEvent("change", {
+                selectedItem: {
+                  name: "selectedItem",
+                  type: "string",
+                  optional: false,
+                  description: "The selected item.",
+                },
+              }),
+            ],
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+
+      const directivesWithOverlay = {
+        ...directives,
+        overlays: {
+          testlib: [
+            {
+              name: "testlib.MyClass",
+              events: [{ name: "change", explicit: true }],
+            },
+          ],
+        },
+      };
+
+      const result = await generateFromObjects({
+        apiObject: structuredClone(apiObject),
+        dependencyApiObjects: [structuredClone(baseLibApi)],
+        directives: directivesWithOverlay,
+      });
+
+      const selectedItemLine = findPropertyLine(result.dtsText, "selectedItem");
+      assert.ok(selectedItemLine, "selectedItem should appear in output");
+      assert.ok(
+        !selectedItemLine.includes("?"),
+        `overlay should make selectedItem required, got: "${selectedItemLine.trim()}"`,
+      );
+    });
+
+    it("overlay does not affect events with different names", async () => {
+      const apiObject = {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.MyClass",
+            basename: "MyClass",
+            resource: "testlib/MyClass.js",
+            module: "testlib/MyClass",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.base.EventProvider",
+            description: "A test class.",
+            events: [
+              makeEvent("change", {
+                selectedItem: {
+                  name: "selectedItem",
+                  type: "string",
+                  optional: false,
+                  description: "The selected item.",
+                },
+              }),
+              makeEvent("press", {
+                source: {
+                  name: "source",
+                  type: "string",
+                  optional: false,
+                  description: "The source.",
+                },
+              }),
+            ],
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "attachPress",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachPress",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "firePress",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+
+      const directivesWithOverlay = {
+        ...directives,
+        overlays: {
+          testlib: [
+            {
+              name: "testlib.MyClass",
+              events: [{ name: "change", explicit: true }],
+            },
+          ],
+        },
+      };
+
+      const result = await generateFromObjects({
+        apiObject: structuredClone(apiObject),
+        dependencyApiObjects: [structuredClone(baseLibApi)],
+        directives: directivesWithOverlay,
+      });
+
+      const selectedItemLine = findPropertyLine(result.dtsText, "selectedItem");
+      assert.ok(
+        !selectedItemLine.includes("?"),
+        `change event should have required selectedItem, got: "${selectedItemLine.trim()}"`,
+      );
+      // press event was NOT targeted by overlay, so source stays optional
+      assert.match(result.dtsText, /source\?/);
+    });
+  });
+
+  describe("inheritance with explicit flag", function () {
+    const baseLibApi = {
+      library: "sap.ui.core",
+      version: "4.0.0",
+      symbols: [
+        {
+          kind: "namespace",
+          name: "sap.ui.base",
+          basename: "base",
+          resource: "sap/ui/base/library.js",
+          module: "sap/ui/base/library",
+          export: "",
+          visibility: "public",
+          description: "",
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.EventProvider",
+          basename: "EventProvider",
+          resource: "sap/ui/base/EventProvider.js",
+          module: "sap/ui/base/EventProvider",
+          export: "",
+          visibility: "public",
+          abstract: true,
+          description: "Base event provider.",
+          methods: [
+            {
+              name: "attachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "oData", type: "object", optional: true },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "detachEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "fireEvent",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "sEventId", type: "string", optional: false },
+                { name: "mParameters", type: "object", optional: true },
+              ],
+            },
+          ],
+        },
+        {
+          kind: "class",
+          name: "sap.ui.base.Parent",
+          basename: "Parent",
+          resource: "sap/ui/base/Parent.js",
+          module: "sap/ui/base/Parent",
+          export: "",
+          visibility: "public",
+          extends: "sap.ui.base.EventProvider",
+          description: "A parent class with a change event.",
+          events: [
+            makeEvent("change", {
+              value: {
+                name: "value",
+                type: "string",
+                optional: false,
+                description: "The value.",
+              },
+            }),
+          ],
+          methods: [
+            {
+              name: "attachChange",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "oData", type: "object", optional: true },
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "detachChange",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "fnFunction", type: "function", optional: false },
+                { name: "oListener", type: "object", optional: true },
+              ],
+            },
+            {
+              name: "fireChange",
+              visibility: "public",
+              returnValue: { type: "this" },
+              parameters: [
+                { name: "mParameters", type: "object", optional: true },
+              ],
+            },
+          ],
+        },
+      ],
+    };
+
+    it("inherited parameters remain optional when only subclass is explicit", async () => {
+      // Parent has "change" event with "value" (optional: false) but is NOT explicit
+      // Child has "change" event with "value" (inherited) + "extra" (new, optional: false) and IS explicit
+      // Expected: "extra" becomes required, but "value" stays optional (inherited from parent interface)
+      const childEvent = makeEvent(
+        "change",
+        {
+          value: {
+            name: "value",
+            type: "string",
+            optional: false,
+            description: "The value.",
+          },
+          extra: {
+            name: "extra",
+            type: "string",
+            optional: false,
+            description: "Extra param added by child.",
+          },
+        },
+        true,
+      );
+
+      const apiObject = {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.Child",
+            basename: "Child",
+            resource: "testlib/Child.js",
+            module: "testlib/Child",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.base.Parent",
+            description: "A child class.",
+            events: [childEvent],
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+
+      const result = await generate(apiObject, [baseLibApi]);
+
+      // "extra" is new in the child and explicit: true → required
+      const extraLine = findPropertyLine(result.dtsText, "extra");
+      assert.ok(extraLine, "extra should appear in output");
+      assert.ok(
+        !extraLine.includes("?"),
+        `extra should be required (no '?'), got: "${extraLine.trim()}"`,
+      );
+
+      // "value" is inherited from parent (not explicit) → stays optional in parent interface
+      // The child interface extends the parent interface and does NOT redeclare "value"
+      assert.ok(
+        !findPropertyLine(result.dtsText, "value"),
+        "value should NOT appear in child interface (it is inherited from parent)",
+      );
+
+      // The child interface should extend the parent interface
+      assert.match(
+        result.dtsText,
+        /Child\$ChangeEventParameters extends Parent\$ChangeEventParameters/,
+      );
+    });
+
+    it("inherited parameters become required when parent is also explicit", async () => {
+      // Both parent and child have explicit: true
+      const baseLibApiWithExplicitParent = structuredClone(baseLibApi);
+      const parentEvent = baseLibApiWithExplicitParent.symbols.find(
+        (s) => s.name === "sap.ui.base.Parent",
+      ).events[0];
+      parentEvent.explicit = true;
+
+      const childEvent = makeEvent(
+        "change",
+        {
+          value: {
+            name: "value",
+            type: "string",
+            optional: false,
+            description: "The value.",
+          },
+          extra: {
+            name: "extra",
+            type: "string",
+            optional: false,
+            description: "Extra param.",
+          },
+        },
+        true,
+      );
+
+      const apiObject = {
+        library: "testlib",
+        version: "1.0.0",
+        symbols: [
+          {
+            kind: "namespace",
+            name: "testlib",
+            basename: "testlib",
+            resource: "testlib/library.js",
+            module: "testlib/library",
+            export: "",
+            visibility: "public",
+            description: "",
+          },
+          {
+            kind: "class",
+            name: "testlib.Child",
+            basename: "Child",
+            resource: "testlib/Child.js",
+            module: "testlib/Child",
+            export: "",
+            visibility: "public",
+            extends: "sap.ui.base.Parent",
+            description: "A child class.",
+            events: [childEvent],
+            methods: [
+              {
+                name: "attachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "oData", type: "object", optional: true },
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "detachChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "fnFunction", type: "function", optional: false },
+                  { name: "oListener", type: "object", optional: true },
+                ],
+              },
+              {
+                name: "fireChange",
+                visibility: "public",
+                returnValue: { type: "this" },
+                parameters: [
+                  { name: "mParameters", type: "object", optional: true },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+
+      const result = await generate(apiObject, [baseLibApiWithExplicitParent]);
+
+      // "extra" is new in the child and explicit → required
+      const extraLine = findPropertyLine(result.dtsText, "extra");
+      assert.ok(extraLine, "extra should appear in output");
+      assert.ok(
+        !extraLine.includes("?"),
+        `extra should be required, got: "${extraLine.trim()}"`,
+      );
+
+      // "value" is inherited from parent which is also explicit → required in parent interface
+      // It should NOT appear in the child interface (still inherited)
+      assert.ok(
+        !findPropertyLine(result.dtsText, "value"),
+        "value should NOT appear in child interface (inherited from explicit parent)",
+      );
+    });
+  });
+});