[BUG] Returning from the agents view renders an empty conversation — only the last message shows (transcript on disk is intact)

Bug

Navigating to the agents view with the left arrow and coming back to the conversation renders an empty transcript — only the last message is shown. Everything above it is gone from the UI.

The data is not lost: the session JSONL on disk is intact (verified — 387-message / 2.8 MB transcript still complete after the UI emptied). This is a render/restore bug on returning from the agents view, not data loss. But it reads as total work loss to the user, which is alarming enough that I lost a lot of time before checking the disk.

Steps to reproduce

1. Work in a session long enough to build up a substantial transcript (hundreds of messages).
2. Press the left arrow to switch to the agents view.
3. Navigate back into the conversation.
4. The conversation area shows only the most recent message; all prior history is missing from the view.

Expected

Returning from the agents view restores the full rendered transcript, matching what is on disk.

Actual

Only the last message renders. Full scrollback is gone until the session is reopened with claude --resume.

Workaround

claude --resume <session-id> re-renders the complete conversation, confirming the on-disk transcript was never damaged.

Environment

• Claude Code 2.1.220
• macOS (Darwin 25.5.0), arm64
• Terminal session, long-running, with background agents in use