Scroll jumps to top in Cursor terminal + PowerShell during streaming/resize

Scroll jumps to top in Cursor terminal + PowerShell during streaming/resize

Description

When using Claude Code in Cursor IDE terminal with PowerShell, the terminal scroll position jumps to the top during:

1. Response streaming
2. Terminal resize

Environment

• IDE: Cursor (VSCode fork)
• Shell: PowerShell
• OS: Windows 11
• Claude Code version: 2.1.31

Environment variables in Cursor terminal:

TERM_PROGRAM=vscode
TERM_PROGRAM_VERSION=2.3.41
WT_SESSION=(empty)
MSYSTEM=(empty)

Root Cause Analysis

After analyzing the bundled cli.js, I found the issue:

1. Terminal detection correctly identifies Cursor as VSCode-compatible

function hd5() {
  if (Cd5()) return true;  // WT_SESSION check
  if (process.platform === "win32" &&
      process.env.TERM_PROGRAM === "vscode" &&
      process.env.TERM_PROGRAM_VERSION) return true;  // ← Cursor matches here
  if (Sd5()) return true;  // mintty, MSYSTEM
  return false;
}

2. This causes \x1B[3J to be used for clearTerminal

function sy1() {
  if (process.platform === "win32")
    if (hd5())
      return Wq6 + G4A + P4A;  // \x1B[2J\x1B[3J\x1B[H
    else
      return Wq6 + yd5;
  return Wq6 + G4A + P4A;
}

3. Full reset (clearTerminal) is triggered frequently

render(A, q) {
  // Triggered on resize
  if (q.viewport.height < A.viewport.height ||
      A.viewport.width !== 0 && q.viewport.width !== A.viewport.width)
    return E_1(q, "resize", ...);  // calls clearTerminal

  // Triggered during streaming when height changes
  if (w && O && H)
    return E_1(q, "offscreen", ...);

  // Triggered on scrollback changes
  if (firstChangeY >= 0)
    return E_1(q, "scrollback changes", ...);
}

4. The \x1B[3J sequence causes scroll jump in Cursor terminal

The \x1B[3J sequence (clear scrollback buffer) appears to cause the viewport to jump to the top in Cursor's terminal emulator.

Suggested Fixes

1. Option A: Detect Cursor terminal specifically and avoid \x1B[3J

• Cursor sets TERM_PROGRAM=vscode but may handle \x1B[3J differently than actual VSCode

1. Option B: Reduce full reset frequency during streaming

• Expand incremental update coverage to avoid clearTerminal calls

1. Option C: Use cursor save/restore sequences

• Add \x1B[s (save) and \x1B[u (restore) around render operations
• Currently 0 occurrences of cursor save/restore in the codebase

Related Issues

• #3648 - Terminal Scrolling Uncontrollably
• #14208 - Cursor position drift / scrollback corruption on Windows
• #16774 - Jumping and scrolling issues
• #16939 - Terminal flickering/rapid scrolling on Windows 11