Developer sooftware has released Lmux, a lightweight, native macOS terminal designed specifically for managing multiple Claude Code and Codex sessions. Built on libghostty and written in Swift, the app weighs in at just 25 MB and claims near-zero idle CPU usage, a stark contrast to heavier terminal emulators that ship with integrated browsers and SSH workspaces. The project addresses a growing pain point for developers who have migrated from single-terminal workflows to juggling numerous concurrent AI agents, where resource overhead becomes a critical bottleneck.

Performance and Resource Efficiency

The core value proposition of Lmux is its minimal footprint. In benchmark tests conducted on an M4 Pro running macOS 26.6.2, Lmux consumed between 182 MB and 235 MB of memory for 1 to 20 workspaces, compared to 398 MB to 661 MB for the popular cmux terminal. Idle CPU usage remained between 0.07% and 0.12%, even with twenty active workspaces, whereas cmux hovered around 7-8%. The developers emphasize that Lmux releases GPU memory when not in focus, ensuring that battery drain is minimized while agents sit idle waiting for user input.

Agent-Aware Session Management

Lmux integrates deeply with the AI agents it manages, offering features that standard terminals lack. It utilizes hooks from Claude Code and Codex to display real-time status indicators, such as whether an agent is running, failed, or waiting for user input. A standout feature is the ability to "take back" a prompt; users can hover over a previous turn and press a key combination to rewind Claude Code to the state before that prompt was sent, allowing for error correction without restarting the session. The app also supports seamless resumption of sessions after a reboot or update, preserving workspace splits and folder structures.

Compatibility and Limitations

While Lmux is optimized for macOS 14+ on Apple Silicon, it does not support Linux or Windows, as it relies on native AppKit and libghostty. It is not a fork of cmux but rather a ground-up rewrite with a narrower scope, intentionally excluding features like in-app browsers, PR badges, and extensive scripting capabilities. The developer notes that users who require these "knobs"β€”cmux has approximately 200 settings compared to Lmux's tenβ€”should stick with existing solutions. Lmux also includes robust support for international input methods, ensuring that Korean, Japanese, and Chinese IMEs function correctly without dropping characters or misaligning carets.

Key Takeaways

  • Lmux is a 25 MB native macOS terminal built on libghostty, targeting Claude Code and Codex users.
  • It demonstrates significantly lower resource usage than cmux, with idle CPU under 0.12% and memory under 235 MB for heavy workloads.
  • Unique features include session resumption, real-time agent status tracking via hooks, and the ability to rewind prompts in Claude Code.
  • The app is macOS-only (Apple Silicon) and deliberately avoids bloat like integrated browsers and SSH workspaces.
  • It is MIT licensed and does not phone home, with no telemetry or background network calls.

The Bottom Line

Lmux represents a necessary correction in the dev tool space, proving that AI agents don't need a bloated IDE wrapper to be manageable. For developers drowning in resource-heavy terminals, this is the lean, native solution they’ve been waiting for.