[Feature Request] Add in-conversation message previews and quick navigation to ChatGPT chats

No implementation files, tests, or entry points are named. Start by comparing the existing Codex preview and navigation patterns with related issue #22627, then determine how the ChatGPT Chat surface represents messages; done means an open conversation can show previews, jump to a selected message, preserve reading position, and remain responsive for long threads.

What variant of Codex are you using?

Unified ChatGPT / Codex desktop app on macOS.

What feature would you like to see?

Please add a Codex-style in-conversation preview and navigation experience to the ChatGPT Chat surface in the unified desktop app.

Problem

Long ChatGPT conversations often contain many rounds of research, explanations, generated artifacts, and follow-up decisions. At present, revisiting an earlier part of the same conversation mainly requires repeatedly scrolling upward and visually scanning the full message history.

This is especially inefficient when trying to return to:

• an earlier user prompt or constraint;
• a previous answer, figure, file, or code block;
• a specific decision or correction;
• the point where the topic changed;
• a message referenced later in the conversation.

Conversation search helps locate an entire chat, but it does not provide a fast way to preview and navigate messages inside the currently open conversation.

Proposed experience

Add an optional message preview / navigator for ChatGPT conversations, reusing the compact preview and navigation patterns already available elsewhere in Codex where possible.

The navigator could provide:

• a compact chronological list of messages in the current conversation;
• short previews of each user message and assistant response;
• clear visual distinction between user and assistant messages;
• click-to-jump navigation to the selected message;
• an indicator showing the current position in the conversation;
• search or filtering limited to the active conversation;
• keyboard shortcuts to move between user prompts, assistant replies, or search matches;
• lazy loading or virtualization so very long conversations remain responsive.

A lightweight first version could show only user-message previews, since user prompts usually provide the clearest outline of a long conversation.

Expected behavior

From an open ChatGPT conversation, users should be able to open a compact message overview, preview earlier parts of the same thread, and jump directly to any selected message without manually scrolling through the entire chat.

The feature should preserve the current reading position so users can easily return to where they were.

Why this matters

The unified desktop app is increasingly used for long-running research, planning, document creation, and technical discussions. These workflows benefit from the same strong in-thread navigation expected in long Codex sessions.

Providing feature parity between Codex conversations and ChatGPT Chat would make the unified app substantially easier to use for long, information-dense threads.

Related issue

• #22627 requests in-thread navigation and a table of contents for long Codex sessions. This request specifically asks that comparable preview and quick-navigation capabilities also be implemented for the ChatGPT Chat surface in the unified app.