diff --git a/packages/shared/common/__tests__/internal/fdv2/protocolHandler.test.ts b/packages/shared/common/__tests__/internal/fdv2/protocolHandler.test.ts
index 1b3d099e80..940404f1c3 100644
--- a/packages/shared/common/__tests__/internal/fdv2/protocolHandler.test.ts
+++ b/packages/shared/common/__tests__/internal/fdv2/protocolHandler.test.ts
@@ -202,14 +202,67 @@ it('ignores put-objects received before a server-intent', () => {
   expect(action.type).toBe('none');
 });
 
-it('silently ignores put-objects with unrecognized kinds', () => {
-  const handler = createHandler();
+it('silently ignores put-objects and delete-objects with unsupported kinds', () => {
+  const logger: LDLogger = { error: jest.fn(), warn: jest.fn(), info: jest.fn(), debug: jest.fn() };
+  const handler = createProtocolHandler(passthrough, logger);
+  handler.processEvent(intentEvent('xfer-changes'));
+
+  // Interleave objects of an unsupported kind with supported ones.
+  const actions = [
+    putEvent('flag', 'f1', 1, { on: true }),
+    putEvent('some-future-kind', 'x1', 1, { foo: 1 }),
+    deleteEvent('some-future-kind', 'x2', 2),
+    deleteEvent('segment', 's1', 3),
+    transferredEvent('s', 1),
+  ].map((event) => handler.processEvent(event));
+
+  // No event is rejected, the payload holds only the supported objects, and nothing is
+  // logged above debug.
+  const action = actions.pop()!;
+  expect(actions.every((other) => other.type === 'none')).toBe(true);
+  expect(action.type).toBe('payload');
+  if (action.type !== 'payload') return;
+  expect(action.payload.updates).toEqual([
+    { kind: 'flag', key: 'f1', version: 1, object: { on: true } },
+    { kind: 'segment', key: 's1', version: 3, deleted: true },
+  ]);
+  expect(logger.warn).not.toHaveBeenCalled();
+  expect(logger.error).not.toHaveBeenCalled();
+});
+
+it.each(['constructor', 'toString', '__proto__'])(
+  'ignores objects whose kind names an inherited object member: %s',
+  (kind) => {
+    const handler = createHandler();
+    handler.processEvent(intentEvent('xfer-changes'));
+    handler.processEvent(putEvent('flag', 'f1', 1, { on: true }));
+
+    // Send a put and a delete whose kind is not a registered processor.
+    handler.processEvent(putEvent(kind, 'x1', 1, { foo: 1 }));
+    handler.processEvent(deleteEvent(kind, 'x2', 2));
+    const action = handler.processEvent(transferredEvent('s', 1));
+
+    // Only the supported object is in the payload.
+    expect(action.type).toBe('payload');
+    if (action.type !== 'payload') return;
+    expect(action.payload.updates.map((update) => update.key)).toEqual(['f1']);
+  },
+);
+
+it('warns when the processor for a supported kind rejects the object', () => {
+  const logger: LDLogger = { error: jest.fn(), warn: jest.fn(), info: jest.fn(), debug: jest.fn() };
+  const handler = createProtocolHandler({ flag: () => undefined }, logger);
   handler.processEvent(intentEvent('xfer-full'));
-  handler.processEvent(putEvent('unknownKind', 'f1', 1, { on: true }));
 
+  // The processor for a supported kind rejects the object.
+  handler.processEvent(putEvent('flag', 'f1', 1, { on: true }));
+
+  // The object is dropped and the rejection is reported.
   const action = handler.processEvent(transferredEvent('s', 1));
+  expect(action.type).toBe('payload');
   if (action.type !== 'payload') return;
   expect(action.payload.updates).toHaveLength(0);
+  expect(logger.warn).toHaveBeenCalledTimes(1);
 });
 
 it('accumulates delete-objects during a transfer', () => {
diff --git a/packages/shared/common/src/internal/fdv2/protocolHandler.ts b/packages/shared/common/src/internal/fdv2/protocolHandler.ts
index c5e12669a0..373dbdacfb 100644
--- a/packages/shared/common/src/internal/fdv2/protocolHandler.ts
+++ b/packages/shared/common/src/internal/fdv2/protocolHandler.ts
@@ -88,6 +88,12 @@ export function createProtocolHandler(
   let tempType: PayloadType = 'partial';
   let tempUpdates: Update[] = [];
 
+  // Only kinds with a registered processor are supported. An own-property check keeps
+  // kinds such as 'constructor' from resolving to inherited members.
+  function isSupportedKind(kind: string): boolean {
+    return Object.prototype.hasOwnProperty.call(objProcessors, kind);
+  }
+
   function processObj(kind: string, jsonObj: any): any {
     return objProcessors[kind]?.(jsonObj);
   }
@@ -171,6 +177,13 @@ export function createProtocolHandler(
       return ACTION_NONE;
     }
 
+    // Objects of unsupported kinds are dropped silently so the protocol can add new kinds
+    // without disrupting older SDKs.
+    if (!isSupportedKind(data.kind)) {
+      logger?.debug(`Ignoring put-object with unsupported kind: '${data.kind}'`);
+      return ACTION_NONE;
+    }
+
     const obj = processObj(data.kind, data.object);
     if (!obj) {
       logger?.warn(`Unable to process object for kind: '${data.kind}'`);
@@ -199,6 +212,11 @@ export function createProtocolHandler(
       return ACTION_NONE;
     }
 
+    if (!isSupportedKind(data.kind)) {
+      logger?.debug(`Ignoring delete-object with unsupported kind: '${data.kind}'`);
+      return ACTION_NONE;
+    }
+
     tempUpdates.push({
       kind: data.kind,
       key: data.key,
diff --git a/packages/shared/sdk-client/__tests__/datasource/fdv2/StreamingFDv2Base.test.ts b/packages/shared/sdk-client/__tests__/datasource/fdv2/StreamingFDv2Base.test.ts
index 723b9364d3..5a56b8f7dd 100644
--- a/packages/shared/sdk-client/__tests__/datasource/fdv2/StreamingFDv2Base.test.ts
+++ b/packages/shared/sdk-client/__tests__/datasource/fdv2/StreamingFDv2Base.test.ts
@@ -204,6 +204,11 @@ it('silently ignores unrecognized object kinds', async () => {
     version: 1,
     object: { data: 'ignored' },
   });
+  simulateEvent(mockEventSource, 'delete-object', {
+    kind: 'unknown_kind',
+    key: 'mystery-deleted',
+    version: 2,
+  });
   simulateEvent(mockEventSource, 'payload-transferred', { state: '(p:p1:1)', version: 1 });
 
   const result = await base.takeResult();
@@ -212,6 +217,8 @@ it('silently ignores unrecognized object kinds', async () => {
 
   expect(result.payload.updates).toHaveLength(1);
   expect(result.payload.updates[0].key).toBe('known');
+  expect(logger.warn).not.toHaveBeenCalled();
+  expect(logger.error).not.toHaveBeenCalled();
 
   base.close();
 });
diff --git a/packages/shared/sdk-server/__tests__/data_sources/PollingProcessorFDv2.test.ts b/packages/shared/sdk-server/__tests__/data_sources/PollingProcessorFDv2.test.ts
index 688a11f89d..f5cd65d46e 100644
--- a/packages/shared/sdk-server/__tests__/data_sources/PollingProcessorFDv2.test.ts
+++ b/packages/shared/sdk-server/__tests__/data_sources/PollingProcessorFDv2.test.ts
@@ -101,6 +101,58 @@ describe('given a polling processor', () => {
     });
   });
 
+  it('applies supported objects and ignores objects of unsupported kinds', () => {
+    const logger = new TestLogger();
+    processor = new PollingProcessorFDv2(requestor as unknown as Requestor, longInterval, logger);
+    const body = JSON.stringify({
+      events: [
+        {
+          event: 'server-intent',
+          data: { payloads: [{ intentCode: 'xfer-full', id: 'mockId' }] },
+        },
+        {
+          event: 'put-object',
+          data: { kind: 'flag', key: 'flagA', version: 1, object: { key: 'flagA', version: 1 } },
+        },
+        {
+          event: 'put-object',
+          data: { kind: 'some-future-kind', key: 'futureA', version: 1, object: { foo: 1 } },
+        },
+        {
+          event: 'delete-object',
+          data: { kind: 'some-future-kind', key: 'futureB', version: 2 },
+        },
+        {
+          event: 'put-object',
+          data: { kind: 'segment', key: 'segA', version: 1, object: { key: 'segA', version: 1 } },
+        },
+        {
+          event: 'payload-transferred',
+          data: { state: 'mockState', version: 1 },
+        },
+      ],
+    });
+    requestor.requestAllData = jest.fn((cb) => cb(undefined, body, headers));
+    const dataCallback = jest.fn();
+    const statusCallback = jest.fn();
+
+    // Poll a response that mixes supported and unsupported kinds.
+    processor.start(dataCallback, statusCallback);
+
+    // Only the supported objects are delivered, and the source reports valid without warnings.
+    expect(dataCallback).toHaveBeenCalledTimes(1);
+    expect(dataCallback.mock.calls[0][1].payload.updates).toEqual([
+      { kind: 'flag', key: 'flagA', version: 1, object: { key: 'flagA', version: 1 } },
+      { kind: 'segment', key: 'segA', version: 1, object: { key: 'segA', version: 1 } },
+    ]);
+    expect(statusCallback.mock.calls).toEqual([
+      [subsystem.DataSourceState.Initializing],
+      [subsystem.DataSourceState.Valid],
+    ]);
+    expect(logger.getCount(LogLevel.Warn)).toBe(0);
+    expect(logger.getCount(LogLevel.Error)).toBe(0);
+  });
+
   it('can process FDv1 data when configured to do so', async () => {
     processor = new PollingProcessorFDv2(
       requestor as unknown as Requestor,