Allow scrolling back to view full conversation history in CLI TUI

[SunkyYang]

Problem

In the Claude Code CLI (TUI mode), older messages in a conversation become invisible and cannot be scrolled back to, even before context compression kicks in. The terminal's own scrollback buffer (e.g., Ghostty scrollback-limit = 100000) has no effect because Claude Code uses the alternate screen buffer, which bypasses terminal scrollback entirely.

This means critical information is lost from view during a session:

• Tool call results (file contents, command output, search results)
• Code diffs and changes made earlier in the conversation
• Architectural decisions and reasoning from earlier messages
• Error messages and debugging context

There is no user-configurable setting (settings.json, environment variable, or CLI flag) to control how many messages are rendered in the TUI.

Proposed Solution

1. Virtual scrolling in TUI - Render only visible messages in the viewport, but allow scrolling back through the full conversation history (similar to how terminal multiplexers handle scrollback)
2. Configurable render limit - At minimum, expose a setting (e.g., maxRenderedMessages or tui.scrollbackLines) so users can control how much history is kept renderable
3. Lazy rendering on scroll - Load and render older messages on demand when the user scrolls up, rather than discarding them

Environment

• Claude Code v2.1.51
• Terminal: Ghostty (also reproducible in iTerm2, Terminal.app)
• OS: macOS

Related

• Virtual scrolling / lazy-load for long conversations in Web UI #24146 - Virtual scrolling for Web UI (same problem, different platform)

[github-actions]

Found 3 possible duplicate issues:

1. [BUG] After compaction the terminal resets and i cannot scroll up and see what all were discussed, changed and done. #13446
2. Compaction clears screen - can't scroll up to see previous context #18204
3. Scroll regression in 2.0.8 - cannot scroll conversation history #9001

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[SunkyYang]

This is not a duplicate of the three referenced issues. Those are all related to compaction/compression clearing the screen:

• [BUG] After compaction the terminal resets and i cannot scroll up and see what all were discussed, changed and done. #13446 - After compaction the terminal resets
• Compaction clears screen - can't scroll up to see previous context #18204 - Compaction clears screen
• Scroll regression in 2.0.8 - cannot scroll conversation history #9001 - Scroll regression (also tied to context window resets)

My issue is fundamentally different: older messages become unviewable even before any compaction occurs. In a single session with no compression triggered, earlier messages (tool results, code diffs, reasoning) simply disappear from the TUI viewport and cannot be scrolled back to.

The root cause is that Claude Code's TUI uses the terminal's alternate screen buffer, which bypasses the terminal's own scrollback entirely. The terminal's scrollback-limit setting (e.g., Ghostty's 100,000 lines) has zero effect. And there is no internal setting to control how many messages the TUI keeps renderable.

This needs to be addressed separately from the compaction-related scroll issues.

[arkevo]

I'm having the same issue

[casepot]

Also having this. Losing the majority of conversation history visible to me. How does a regression like this get through? It makes it impossible to understand what was going on if you step away for a second. Ctrl+o and ctrl+e seem to lose the history too?

[cstelmach]

Opus summary:

Working version: v2.1.72 (March 10)
Broken version: v2.1.76 (March 14) - TUI scroll history noticeably shorter

Setup:

• Terminal: Ghostty (scrollback-limit = 52428800 / 50MB)
• Also tested inside tmux (history-limit 100000)
• Neither helps — the limit is inside Claude Code's TUI, not the terminal

What I see: During a normal session (no compaction, no /clear, no resize), scrolling up hits a hard wall well before the full conversation history. Earlier tool outputs, code diffs, and reasoning are simply gone from the viewport. This started after updating from v2.1.72.

Likely cause (according to Opus 4.6): The fix for #21806 (55K-row scrollback causing 100% CPU / 5.7GB RAM) probably introduced a hard cap on the TUI's internal render buffer. Understandable — but the current cap is too aggressive for power users running multi-hour agentic sessions.

Proposal: Expose a configurable setting (e.g., tui.maxScrollbackLines) with a conservative default (e.g., 5,000 lines) that prevents the #21806 scenario while letting users opt into larger buffers at their own risk:

// ~/.claude/settings.json

{
	"tui": {
	  "maxScrollbackLines": 20000
	}
}

This is a one-line constant change on the Anthropic side — the renderer already has the cap, it just needs to read it from config instead of hardcoding it.