One player, many boards. A native macOS app for running several coding
agents side by side — Claude Code, Codex, OpenCode or a plain shell — each in
a real terminal, one keystroke apart (⌘1…⌘9).
Named after a chess simul, where one player walks between many boards and plays wherever a move is waiting. simul.sh
- Real terminals. Every session is a Ghostty terminal running the agent's own CLI, with your login, config and MCPs — Simul never talks to provider APIs or touches credentials.
- Picks up where you left off. Each session reopens its own conversation.
- Knows what needs you. Sessions show when an agent is working and when it's done; plan limits for Claude and Codex sit at the bottom.
Early and personal: macOS 14+, Apple Silicon. FEATURES.md lists everything it does; CHANGELOG.md what changed when.
Needs the Command Line Tools (no Xcode) and Zig 0.16.0, the exact version the pinned Ghostty expects:
git submodule update --init Vendor/Ghostty
curl -fsSL https://ziglang.org/download/0.16.0/zig-aarch64-macos-0.16.0.tar.xz | tar xJ -C Vendor
mv Vendor/zig-aarch64-macos-0.16.0 Vendor/zig
scripts/build-ghostty.sh # builds libghostty.a (a few minutes, once)
scripts/build-app.sh # builds Build/Simul.app, then runs scripts/smoke.sh
scripts/install.sh # optional: copies it to /Applications and opens it
swift run SimulTests # tests (tmux tests need `brew install tmux`)MIT © Bernat Torres.
Simul builds on Ghostty (MIT, © Mitchell Hashimoto and Ghostty contributors), included as a submodule and linked into the app; its license ships with it and must accompany any distributed build.
Claude, Codex/OpenAI and OpenCode names and logos are trademarks of their respective owners, used only to show which agent a session runs. Simul is not affiliated with or endorsed by them.