quell

Windows-native terminal proxy that eliminates scroll-jumping for AI CLI tools.

When Claude Code, Copilot CLI, or Gemini CLI stream long responses, your terminal's scroll position jumps to the top of the visible output on every update — making it impossible to read anything while new content arrives. quell sits between your terminal and the AI tool, keeping your scroll position stable.

The Problem

Every AI CLI tool streams output through VT escape sequences. Terminals reset the scroll position to the top of the output on each update, causing constant scroll-jumping during long responses. This is the #1 complaint across AI CLI tools, with hundreds of upvotes across multiple issue trackers.

How It Works

Your Terminal  <-->  quell (proxy)  <-->  ConPTY  <-->  AI CLI tool

quell intercepts the child process output via Windows ConPTY, processes VT escape sequences, filters dangerous sequences, and forwards clean output to your terminal. Your scroll position stays exactly where you left it.

Features

• Scroll stability — eliminates scroll-jumping and scrollback accumulation; read earlier output while new content streams in
• Shift+Enter support — inserts newline in Claude Code via Kitty keyboard protocol (Windows Terminal 1.25+)
• Security filtering — blocks clipboard access (OSC 52), dangerous URL schemes (ssh://, javascript://), terminal query attacks, and C1 control characters
• Full Unicode — emoji, CJK, box-drawing, mathematical symbols all render correctly
• Tool-agnostic — works with Claude Code, Copilot CLI, Gemini CLI, or any terminal program
• Zero config — just prefix your command with quell
• No network, no telemetry — the binary makes zero network connections

Quick Start

Install

1. Download quell.exe from Releases
2. Place it in a folder on your PATH (e.g. C:\Users\YOU\.local\bin)
3. Open a new terminal and run:

quell claude

That's it. quell shows a banner when it starts, launches Claude Code behind it, and keeps your scroll position stable.

Usage

# Run Claude Code through quell
quell claude -- --dangerously-skip-permissions

# Run any AI CLI tool
quell gemini
quell copilot

# Explicit tool override (affects Shift+Enter behavior)
quell --tool claude my-custom-claude-wrapper

# Verbose output for troubleshooting
quell --verbose claude

Build from Source

Requires Rust (stable toolchain).

git clone https://github.com/FurbySoup/quell.git
cd quell
cargo build --release
# Binary at target/release/quell.exe

Troubleshooting

quell claude does nothing / not recognized Your PATH points to the exe file itself instead of the folder containing it. PATH entries must be directories, not files. Move quell.exe into a directory that's already on your PATH, or add the directory (not the file) to PATH.

failed to spawn process (0x80070002) The child command (claude, gemini, etc.) isn't on your PATH. Run where claude to check. If nothing is found, install the tool first.

Scroll still jumps Make sure you're on the latest release. Run quell --verbose claude and check the debug output for clues. If the issue persists, open an issue with the verbose log.

Configuration

quell works out of the box with no configuration. Optional settings can be placed in %APPDATA%\quell\config.toml:

render_delay_ms = 5        # Normal output coalescing (ms)
sync_delay_ms = 50         # Sync block coalescing (ms)
history_lines = 100000     # Scrollback buffer size
log_level = "info"         # trace, debug, info, warn, error
log_file = "C:\\logs\\quell.log"  # Optional — logs to stderr if omitted

CLI flags override config file values. See quell --help for all options.

Security

AI-generated output is untrusted. quell classifies every VT escape sequence and blocks known attack vectors:

| Category | Action | Examples | |----------|--------|----------| | Blocked | Stripped entirely | Clipboard access (OSC 52), font queries (OSC 50), terminal device queries | | Filtered | Sanitized before forwarding | Window titles (control chars stripped), hyperlinks (URL scheme whitelist) | | Allowed | Passed through | Cursor movement, colors, screen management, sync markers |

The URL scheme whitelist allows http, https, and file only — blocking schemes used in real CVEs (CVE-2023-46321, CVE-2023-46322).

See SECURITY.md for the full threat model.

Requirements

• Windows 10 1809+ (ConPTY support required)
• Windows Terminal 1.25+ for Shift+Enter support (older terminals still work, Alt+Enter remains available)

Known Limitations

• Cursor-home viewport shift. In some terminals, cursor-home sequences (ESC[H) during screen repaints can cause a minor viewport shift. This is caused by an upstream Windows Terminal bug where SetConsoleCursorPosition always snaps the viewport to the cursor. Phase 2 (standalone terminal) will eliminate this entirely by controlling the rendering surface directly.
• Emoji picker (WIN+.) and IME input may not work through quell. This is a ConPTY limitation. Workaround: copy-paste emoji via Ctrl+V.

Roadmap

• Phase 1: CLI proxy — scroll stability, security filtering, Shift+Enter, startup banner, friendly errors, --verbose diagnostics
• Phase 2: Standalone terminal (Tauri + xterm.js) with structured output, collapsible sections, tabs, accessibility
• Phase 3: Session persistence, split panes, search, community release

License

MIT