diff --git a/client/src/components/Chat/Messages/Message.tsx b/client/src/components/Chat/Messages/Message.tsx
index 53aef812fc..fc2a79fca0 100644
--- a/client/src/components/Chat/Messages/Message.tsx
+++ b/client/src/components/Chat/Messages/Message.tsx
@@ -47,7 +47,6 @@ export default function Message(props: TMessageProps) {
         </div>
       </MessageContainer>
       <MultiMessage
-        key={messageId}
         messageId={messageId}
         conversation={conversation}
         messagesTree={children ?? []}
diff --git a/client/src/components/Chat/Messages/MessageIcon.tsx b/client/src/components/Chat/Messages/MessageIcon.tsx
index d63e0d2071..619d2f827d 100644
--- a/client/src/components/Chat/Messages/MessageIcon.tsx
+++ b/client/src/components/Chat/Messages/MessageIcon.tsx
@@ -1,4 +1,4 @@
-import { useMemo, memo } from 'react';
+import { useMemo, useEffect, useRef, memo } from 'react';
 import { getEndpointField } from 'librechat-data-provider';
 import type { Assistant, Agent } from 'librechat-data-provider';
 import type { TMessageIcon } from '~/common';
@@ -19,38 +19,54 @@ type MessageIconProps = {
  * this component renders display properties only, not identity-derived content.
  */
 export function arePropsEqual(prev: MessageIconProps, next: MessageIconProps): boolean {
-  if (prev.iconData?.endpoint !== next.iconData?.endpoint) {
-    return false;
-  }
-  if (prev.iconData?.model !== next.iconData?.model) {
-    return false;
-  }
-  if (prev.iconData?.iconURL !== next.iconData?.iconURL) {
-    return false;
-  }
-  if (prev.iconData?.modelLabel !== next.iconData?.modelLabel) {
-    return false;
-  }
-  if (prev.iconData?.isCreatedByUser !== next.iconData?.isCreatedByUser) {
-    return false;
-  }
-  if (prev.agent?.name !== next.agent?.name) {
-    return false;
-  }
-  if (prev.agent?.avatar?.filepath !== next.agent?.avatar?.filepath) {
-    return false;
-  }
-  if (prev.assistant?.name !== next.assistant?.name) {
-    return false;
-  }
-  if (prev.assistant?.metadata?.avatar !== next.assistant?.metadata?.avatar) {
-    return false;
+  const checks: [string, unknown, unknown][] = [
+    ['iconData.endpoint', prev.iconData?.endpoint, next.iconData?.endpoint],
+    ['iconData.model', prev.iconData?.model, next.iconData?.model],
+    ['iconData.iconURL', prev.iconData?.iconURL, next.iconData?.iconURL],
+    ['iconData.modelLabel', prev.iconData?.modelLabel, next.iconData?.modelLabel],
+    ['iconData.isCreatedByUser', prev.iconData?.isCreatedByUser, next.iconData?.isCreatedByUser],
+    ['agent.name', prev.agent?.name, next.agent?.name],
+    ['agent.avatar.filepath', prev.agent?.avatar?.filepath, next.agent?.avatar?.filepath],
+    ['assistant.name', prev.assistant?.name, next.assistant?.name],
+    [
+      'assistant.metadata.avatar',
+      prev.assistant?.metadata?.avatar,
+      next.assistant?.metadata?.avatar,
+    ],
+  ];
+
+  for (const [field, prevVal, nextVal] of checks) {
+    if (prevVal !== nextVal) {
+      logger.log('icon_memo_diff', `field "${field}" changed:`, prevVal, '→', nextVal);
+      return false;
+    }
   }
   return true;
 }
 
 const MessageIcon = memo(({ iconData, assistant, agent }: MessageIconProps) => {
-  logger.log('icon_data', iconData, assistant, agent);
+  const renderCountRef = useRef(0);
+  renderCountRef.current += 1;
+
+  useEffect(() => {
+    logger.log(
+      'icon_lifecycle',
+      'MOUNT',
+      iconData?.modelLabel,
+      `render #${renderCountRef.current}`,
+    );
+    return () => {
+      logger.log('icon_lifecycle', 'UNMOUNT', iconData?.modelLabel);
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  logger.log(
+    'icon_data',
+    `render #${renderCountRef.current}`,
+    iconData?.isCreatedByUser ? 'user' : iconData?.modelLabel,
+    iconData,
+  );
   const { data: endpointsConfig } = useGetEndpointsQuery();
 
   const agentName = agent?.name ?? '';
diff --git a/client/src/components/Chat/Messages/MessageParts.tsx b/client/src/components/Chat/Messages/MessageParts.tsx
index 3d13fa6ae0..2d0e3d512b 100644
--- a/client/src/components/Chat/Messages/MessageParts.tsx
+++ b/client/src/components/Chat/Messages/MessageParts.tsx
@@ -179,7 +179,6 @@ export default function Message(props: TMessageProps) {
         </div>
       </div>
       <MultiMessage
-        key={messageId}
         messageId={messageId}
         conversation={conversation}
         messagesTree={children ?? []}
diff --git a/client/src/components/Chat/Messages/MessagesView.tsx b/client/src/components/Chat/Messages/MessagesView.tsx
index ca4a0cce85..b4f555d189 100644
--- a/client/src/components/Chat/Messages/MessagesView.tsx
+++ b/client/src/components/Chat/Messages/MessagesView.tsx
@@ -62,7 +62,6 @@ function MessagesViewContent({
                 <>
                   <div ref={screenshotTargetRef}>
                     <MultiMessage
-                      key={conversationId}
                       messagesTree={_messagesTree}
                       messageId={conversationId ?? null}
                       setCurrentEditId={setCurrentEditId}
diff --git a/client/src/components/Chat/Messages/MultiMessage.tsx b/client/src/components/Chat/Messages/MultiMessage.tsx
index 13eb2d143f..4a561045f5 100644
--- a/client/src/components/Chat/Messages/MultiMessage.tsx
+++ b/client/src/components/Chat/Messages/MultiMessage.tsx
@@ -39,47 +39,40 @@ export default function MultiMessage({
     return null;
   }
 
-  const message = messagesTree[messagesTree.length - siblingIdx - 1] as TMessage | undefined;
+  const currentSiblingIdx = messagesTree.length - siblingIdx - 1;
+  const message = messagesTree[currentSiblingIdx] as TMessage | undefined;
 
   if (!message) {
     return null;
   }
 
+  /**
+   * No explicit key — React uses positional reconciliation since MultiMessage
+   * always renders exactly one child at this position.
+   *
+   * Both messageId and parentMessageId change during the SSE lifecycle
+   * (client UUID → createdHandler ID → server ID), so neither can serve as a
+   * stable key. Using either caused React to unmount/remount the entire subtree
+   * on each SSE event, destroying memoized state and causing visible flickering.
+   *
+   * Without a key, React reuses the component instance and updates props in place.
+   * The memo comparators on ContentRender/MessageRender handle field-level diffing,
+   * and sibling switches work correctly because the message prop changes entirely.
+   */
+  const sharedProps = {
+    message,
+    currentEditId,
+    setCurrentEditId,
+    siblingIdx: currentSiblingIdx,
+    siblingCount: messagesTree.length,
+    setSiblingIdx: setSiblingIdxRev,
+  };
+
   if (isAssistantsEndpoint(message.endpoint) && message.content) {
-    return (
-      <MessageParts
-        key={message.messageId}
-        message={message}
-        currentEditId={currentEditId}
-        setCurrentEditId={setCurrentEditId}
-        siblingIdx={messagesTree.length - siblingIdx - 1}
-        siblingCount={messagesTree.length}
-        setSiblingIdx={setSiblingIdxRev}
-      />
-    );
+    return <MessageParts {...sharedProps} />;
   } else if (message.content) {
-    return (
-      <MessageContent
-        key={message.messageId}
-        message={message}
-        currentEditId={currentEditId}
-        setCurrentEditId={setCurrentEditId}
-        siblingIdx={messagesTree.length - siblingIdx - 1}
-        siblingCount={messagesTree.length}
-        setSiblingIdx={setSiblingIdxRev}
-      />
-    );
+    return <MessageContent {...sharedProps} />;
   }
 
-  return (
-    <Message
-      key={message.messageId}
-      message={message}
-      currentEditId={currentEditId}
-      setCurrentEditId={setCurrentEditId}
-      siblingIdx={messagesTree.length - siblingIdx - 1}
-      siblingCount={messagesTree.length}
-      setSiblingIdx={setSiblingIdxRev}
-    />
-  );
+  return <Message {...sharedProps} />;
 }
diff --git a/client/src/components/Chat/Messages/__tests__/MessageIcon.render.test.tsx b/client/src/components/Chat/Messages/__tests__/MessageIcon.render.test.tsx
new file mode 100644
index 0000000000..1c7b3c1aec
--- /dev/null
+++ b/client/src/components/Chat/Messages/__tests__/MessageIcon.render.test.tsx
@@ -0,0 +1,193 @@
+import React from 'react';
+import { render } from '@testing-library/react';
+import { EModelEndpoint } from 'librechat-data-provider';
+import type { Agent } from 'librechat-data-provider';
+import type { TMessageIcon } from '~/common';
+
+jest.mock('librechat-data-provider', () => ({
+  ...jest.requireActual('librechat-data-provider'),
+  getEndpointField: jest.fn(() => ''),
+}));
+jest.mock('~/data-provider', () => ({
+  useGetEndpointsQuery: jest.fn(() => ({ data: {} })),
+}));
+
+// logger is a plain object with a real function — not a jest.fn() —
+// so restoreMocks/clearMocks won't touch it. We spy on it per-test instead.
+const logCalls: unknown[][] = [];
+jest.mock('~/utils', () => ({
+  getIconEndpoint: jest.fn(() => 'agents'),
+  logger: {
+    log: (...args: unknown[]) => {
+      logCalls.push(args);
+    },
+  },
+}));
+jest.mock('~/components/Endpoints/ConvoIconURL', () => {
+  const ConvoIconURL = (props: Record<string, unknown>) => (
+    <div data-testid="convo-icon-url" data-icon-url={props.iconURL as string} />
+  );
+  ConvoIconURL.displayName = 'ConvoIconURL';
+  return { __esModule: true, default: ConvoIconURL };
+});
+jest.mock('~/components/Endpoints/Icon', () => {
+  const Icon = (props: Record<string, unknown>) => (
+    <div data-testid="icon" data-icon-url={props.iconURL as string} />
+  );
+  Icon.displayName = 'Icon';
+  return { __esModule: true, default: Icon };
+});
+
+import MessageIcon from '../MessageIcon';
+
+const makeAgent = (overrides?: Partial<Agent>): Agent =>
+  ({
+    id: 'agent_123',
+    name: 'GitHub Agent',
+    avatar: { filepath: '/images/agent-avatar.png' },
+    ...overrides,
+  }) as Agent;
+
+const baseIconData: TMessageIcon = {
+  endpoint: EModelEndpoint.agents,
+  model: 'agent_123',
+  iconURL: undefined,
+  modelLabel: 'GitHub Agent',
+  isCreatedByUser: false,
+};
+
+describe('MessageIcon render cycles', () => {
+  beforeEach(() => {
+    logCalls.length = 0;
+  });
+
+  it('renders once on initial mount', () => {
+    render(<MessageIcon iconData={baseIconData} agent={makeAgent()} />);
+    const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+    expect(iconDataCalls).toHaveLength(1);
+  });
+
+  it('does not re-render when parent re-renders with same field values but new object references', () => {
+    const agent = makeAgent();
+    const { rerender } = render(<MessageIcon iconData={baseIconData} agent={agent} />);
+    logCalls.length = 0;
+
+    // Simulate parent re-render: new iconData object (same field values), new agent object (same data)
+    rerender(<MessageIcon iconData={{ ...baseIconData }} agent={makeAgent()} />);
+
+    const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+    expect(iconDataCalls).toHaveLength(0);
+  });
+
+  it('does not re-render when agent object reference changes but name and avatar are the same', () => {
+    const agent1 = makeAgent();
+    const { rerender } = render(<MessageIcon iconData={baseIconData} agent={agent1} />);
+    logCalls.length = 0;
+
+    // New agent object with different id but same display fields
+    const agent2 = makeAgent({ id: 'agent_456' });
+    rerender(<MessageIcon iconData={baseIconData} agent={agent2} />);
+
+    const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+    expect(iconDataCalls).toHaveLength(0);
+  });
+
+  it('re-renders when agent avatar filepath changes', () => {
+    const agent1 = makeAgent();
+    const { rerender } = render(<MessageIcon iconData={baseIconData} agent={agent1} />);
+    logCalls.length = 0;
+
+    const agent2 = makeAgent({ avatar: { filepath: '/images/new-avatar.png' } });
+    rerender(<MessageIcon iconData={baseIconData} agent={agent2} />);
+
+    const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+    expect(iconDataCalls).toHaveLength(1);
+  });
+
+  it('re-renders when agent goes from undefined to defined (name changes from undefined to string)', () => {
+    const { rerender } = render(<MessageIcon iconData={baseIconData} agent={undefined} />);
+    logCalls.length = 0;
+
+    rerender(<MessageIcon iconData={baseIconData} agent={makeAgent()} />);
+
+    const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+    expect(iconDataCalls).toHaveLength(1);
+  });
+
+  describe('simulates message lifecycle', () => {
+    it('renders exactly twice during new message + streaming start: initial render + modelLabel update', () => {
+      // Phase 1: Initial response message created by useChatFunctions
+      // model is set to agent_id, iconURL is undefined, modelLabel is '' or sender
+      const initialIconData: TMessageIcon = {
+        endpoint: EModelEndpoint.agents,
+        model: 'agent_123',
+        iconURL: undefined,
+        modelLabel: '', // Not yet resolved
+        isCreatedByUser: false,
+      };
+      const agent = makeAgent();
+
+      const { rerender } = render(<MessageIcon iconData={initialIconData} agent={agent} />);
+
+      // Phase 2: First streaming chunk arrives, messageLabel resolves to agent name
+      // This is a legitimate re-render — modelLabel changed from '' to 'GitHub Agent'
+      const streamingIconData: TMessageIcon = {
+        ...initialIconData,
+        modelLabel: 'GitHub Agent',
+      };
+
+      rerender(<MessageIcon iconData={streamingIconData} agent={agent} />);
+
+      const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+      // Exactly 2: initial mount + modelLabel change
+      expect(iconDataCalls).toHaveLength(2);
+    });
+
+    it('does NOT re-render on subsequent streaming chunks (content changes, isSubmitting stays true)', () => {
+      const iconData: TMessageIcon = {
+        endpoint: EModelEndpoint.agents,
+        model: 'agent_123',
+        iconURL: undefined,
+        modelLabel: 'GitHub Agent',
+        isCreatedByUser: false,
+      };
+      const agent = makeAgent();
+
+      const { rerender } = render(<MessageIcon iconData={iconData} agent={agent} />);
+      logCalls.length = 0;
+
+      // Simulate multiple parent re-renders from streaming chunks
+      // Parent (ContentRender) re-renders because chatContext changed,
+      // but MessageIcon props are identical field-by-field
+      for (let i = 0; i < 5; i++) {
+        rerender(<MessageIcon iconData={{ ...iconData }} agent={makeAgent()} />);
+      }
+
+      const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+      expect(iconDataCalls).toHaveLength(0);
+    });
+
+    it('does NOT re-render when agentsMap context updates with same agent data', () => {
+      const iconData: TMessageIcon = {
+        endpoint: EModelEndpoint.agents,
+        model: 'agent_123',
+        iconURL: undefined,
+        modelLabel: 'GitHub Agent',
+        isCreatedByUser: false,
+      };
+
+      // First render with agent from original agentsMap
+      const agent1 = makeAgent();
+      const { rerender } = render(<MessageIcon iconData={iconData} agent={agent1} />);
+      logCalls.length = 0;
+
+      // agentsMap refetched → new agent object, same display data
+      const agent2 = makeAgent();
+      expect(agent1).not.toBe(agent2); // different reference
+      rerender(<MessageIcon iconData={iconData} agent={agent2} />);
+
+      const iconDataCalls = logCalls.filter((c) => c[0] === 'icon_data');
+      expect(iconDataCalls).toHaveLength(0);
+    });
+  });
+});
diff --git a/client/src/components/Messages/MessageContent.tsx b/client/src/components/Messages/MessageContent.tsx
index 977e397022..67865ed397 100644
--- a/client/src/components/Messages/MessageContent.tsx
+++ b/client/src/components/Messages/MessageContent.tsx
@@ -48,7 +48,6 @@ export default function MessageContent(props: TMessageProps) {
         </div>
       </MessageContainer>
       <MultiMessage
-        key={messageId}
         messageId={messageId}
         conversation={conversation}
         messagesTree={children ?? []}