Feature request: Add a clickable outline for long Markdown responses

What variant of Codex are you using?

App (Desktop)

What feature would you like to see?

Problem

Codex often generates long reports, technical analyses, implementation plans, and research results containing multiple H1, H2, and H3 headings.

Although the Markdown is rendered correctly, once a response spans several screens, its hierarchy becomes difficult to perceive. Users have to scroll through the entire response to find a specific section or return to something they read earlier.

Proposed solution

When an assistant response contains multiple Markdown headings and exceeds a reasonable length threshold, show an optional, collapsible outline beside the response—ideally in the unused left margin of the conversation area.

The outline could:

• Be generated directly from the response’s H1–H4 headings
• Preserve the nesting hierarchy of the Markdown headings
• Let users click a heading to jump to that section
• Highlight the current section while the user scrolls
• Remain hidden for short responses
• Collapse into a compact navigation rail or overlay on narrow windows
• Remain stable while the response is still streaming

This should not require an additional model call because the structure already exists in the rendered Markdown.

Why this matters

Long Codex responses are often closer to documents than ordinary chat messages. A clickable outline would:

• Make the hierarchy immediately visible
• Make long reports easier to scan
• Help users revisit specific findings or recommendations
• Reduce repetitive scrolling
• Make better use of the available space in the desktop layout

A response-level outline could be implemented as a focused first step, while broader thread-level navigation could remain a separate or later feature.

Suggested acceptance criteria

• H1–H4 headings appear in the correct hierarchy
• Clicking a heading scrolls to the correct section
• The active section is highlighted while scrolling
• The outline can be collapsed or hidden
• Short responses are unaffected
• Streaming does not reorder existing outline entries
• The outline is keyboard accessible

Related issue

#22627 proposes navigation across long multi-turn sessions. This request is more specific: it focuses on document-style navigation within a single long assistant response, using that response’s existing Markdown heading hierarchy.

Additional information

This feature request has also been submitted through the Codex desktop app.

Uploaded thread: 019fd5b9-faeb-7783-9839-1ba60cb30323