Bug Description

Hermes TUI appears to have a layout/scroll anchoring issue around the bottom composer/input area.

After upgrading to Hermes Agent v0.13.0, I can reproduce visible jumping not only in Zed's embedded terminal during streaming output, but also in Ghostty when resizing the terminal window. The transcript scrollbar and/or bottom composer area jumps while the layout is recalculated.

This suggests the issue is not Zed-specific; it may be a Hermes TUI resize/layout problem.

Reproduction

Case 1: Streaming output

1. Open Zed embedded terminal.
2. Run hermes.
3. Ask a question that produces a long streamed response.
4. During streaming, the viewport jumps up/down, seemingly around the bottom composer/input area.

Case 2: Terminal resize

1. Open Ghostty.
2. Run hermes.
3. Resize the terminal window horizontally or vertically.
4. Observe the Hermes scrollbar / transcript area jumping.

Expected Behavior

• Bottom composer/input area should remain anchored and stable.
• Transcript scroll position should remain stable during resize.
• Streaming output should not cause the viewport to bounce.

Actual Behavior

• The transcript scrollbar jumps during resize.
• During streaming, the visible terminal content jumps up/down.
• It looks like the input/composer area positioning or ScrollBox height calculation is unstable.

Environment

• Hermes Agent: v0.13.0 (2026.5.7)
• Launch command: hermes
• OS: macOS 15.5
• Hardware: Apple Silicon / M4 Max
• Terminals reproduced:
  • Zed embedded terminal
  • Ghostty

Related Existing Issue

This may be related to the previously closed issue:

• TUI: terminal resize causes infinite scroll/render loop (screen flicker + status bar duplicates) #19216 TUI: terminal resize causes infinite scroll/render loop (screen flicker + status bar duplicates)
• fix(tui): avoid main-screen scrollback reset loops #19225 fix(tui): avoid main-screen scrollback reset loops

The current behavior seems like a remaining/reintroduced edge case, especially around composer anchoring and ScrollBox/stickyScroll recalculation on resize.