MARS

Mission control for your terminal — a non-modal, Emacs-compatible terminal editor with a Claude-Code-style command bar, a built-in LLM agent, real terminal panes, and tmux/zellij-style persistent sessions. One tool, one set of keys.

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Build & install

source ~/.cargo/env            # if cargo isn't on your PATH
cargo build --release
# put it on your PATH:
ln -s "$PWD/target/release/mars" ~/.local/bin/mars   # or copy it anywhere
mars --selfcheck               # optional: run the built-in test suite

Quick start

mars                    # start a session: the MARS banner, then a shell in your cwd
mars notes.md           # edit a file (also inside a session)
mars -s notes.md        # standalone mode: no session daemon, just edit
mars help               # full CLI reference

Sessions are the default, tmux-style: a bare mars gets an auto-numbered session that survives closing the window. Press any key to dismiss the startup banner.

Inside the editor, four keys carry you everywhere:

C-g cancels anything. Every menu row shows its real keybinding, so the fast path teaches itself as you go.

Moving around fast

Fast motion is bound to both ⌘ and ⌥ (Option). ⌘ reaches Mars only on kitty-protocol terminals (kitty, WezTerm, Ghostty, recent iTerm2); on Terminal.app / Warp the OS eats ⌘ — use ⌥ there (enable "Use Option as Meta" if offered). The C-x jumps work on every terminal.

Search doubles as teleport. C-s, type a word you can see — it jumps as you type, with a 3/12 counter. Press Tab and every visible match gets a one-letter label; press a label to teleport straight there. And you don't have to press Enter: just start editing or hit a motion key — the search commits at the current match and your key applies. C-s/C-r cycle matches, C-g cancels (restoring where you started).

Sessions — replace tmux/zellij

Sessions keep your buffers, panes, and running shells alive when the window closes, the SSH connection drops, or you just walk away.

mars new work           # start (or re-attach) a session named "work"
mars ls                 # what's running, and whether anything is attached
mars attach             # reattach the most recent session
mars attach work        # reattach a specific one
mars rename work api    # rename a running session (live — nothing restarts)
mars kill work          # end a session from outside (autosaves first)

The daily rhythm:

1. Start: mars or mars new work — everything from here on lives in the daemon.
2. Detach when you want the terminal back: press C-t then D — or just close the window. Both leave shells running and buffers intact.
3. Come back: mars attach (or mars attach work). Your layout, buffers, and that build you left running in a terminal pane are exactly where you left them. If anything happened while you were gone — a shell exited, a watched task finished, files changed — one while away — … line greets you, failures first. Nothing changed → no briefing.
4. Finish for real: C-x C-c inside the session quits it (with an are-you-sure prompt if anything is unsaved), or mars kill work from outside.

mars ls tells you the state at a glance:

SESSION              STATUS
work                 detached — reattach: mars attach work
review               attached

Safety nets, on by default: modified files autosave every 30s and on every detach/disconnect (scratch buffers are never touched), and each daemon logs to ~/.local/state/mars/<name>.log — if a session ever dies, the postmortem is there.

Notes: one client per session — attaching from a second window takes over from the first (it gets a clean "another client attached" message). Attaching from a different-sized terminal just reflows.

The agent

Works out of the box with a free-tier key from any of:

export GROQ_API_KEY=...        # Groq (free tier) — defaults to qwen/qwen3-32b
export GEMINI_API_KEY=...      # Google AI Studio (free tier) — gemini-3.1-flash-lite
# or any OpenAI-compatible endpoint (e.g. local Ollama):
export MARS_LLM_KEY=... MARS_LLM_URL=http://localhost:11434/v1 MARS_LLM_MODEL=llama3
# override the model for any provider:
export MARS_LLM_MODEL=qwen/qwen3-32b

Reasoning models (Qwen3, DeepSeek-R1) work — their <think> blocks are stripped from answers automatically.

Then ? in the command bar, or from the shell:

mars ask "how do I move a pane to the other side?"

The agent sees your screen — editor buffers, terminal output, your layout — so "why did this build fail?" needs no copy-paste. It holds a conversation (C-l starts a fresh one), and it can act: RUN: fires an editor action, TYPE: types a shell command into your terminal pane, OPEN: jumps to a path:line from a stack trace — always shown first, always one explicit Enter away, never automatic.

What that unlocks:

• Ask about a selection. Select code (Shift+arrows or C-x h), then ? — the exact selection goes along as context, not just the visible screen.
• Reversible refactors. Ask "simplify this" / "add error handling" on a selection: the panel shows ▶ Enter to replace the selection (N lines). Enter applies it as one undo step, so a single C-/ reverts the whole AI edit.
• Triage. C-x ? (or "why did this fail?" in the bar) grounds the agent in the focused terminal's output; C-x e explains what's at the cursor.
• Watch a pane. Kick off a long command, then C-t w. When it exits or goes quiet (~20s), Mars leaves a one-line verdict at the bottom, failures first (✗ failed: linker error · build). Esc dismisses. This fires even while detached — the daemon keeps watching, so mars attach later lands on the verdict.
• Ask beyond the visible screen. Questions like "when did this first start failing?" or "does the error in the api tab match this code?" let the model request more context (the pane's full scrollback, or another tab); Mars supplies it and re-asks once, silently. You do nothing special.
• Shell translation. In a terminal pane, Ctrl+Space then plain English ("find big files here") → the agent translates it to a shell command and shows it for you to confirm. Typed a real Mars command instead? It's recognized and run directly. (! still forces shell, ? asks, @ opens the file tree.)

With an agent connected, tabs you haven't named get a quiet auto-generated label from their content (rename one yourself and it's yours forever; auto_name_secs = 0 turns it off).

Keys you already know

Mars speaks three dialects at once — whichever your fingers know:

• Browse files: Ctrl+Space then @ (or C-x d) opens a file tree on the left. Folders are bold + colored and collapsed — arrow to one and Enter/→ expands it in place (← collapses); on a file, → previews it (reversible) and Enter opens it; ../ at the top steps up a directory. Start typing to fuzzy-filter the whole project to a shortlist; Esc closes.
• Emacs: C-x C-s save · C-x C-f open · C-s isearch · C-k/C-y kill/yank · C-x 2/C-x 3/C-x o windows · M-x command bar
• Modern/Mac: C-c/C-v copy/paste (system clipboard) · Shift+arrows select · typing replaces selection · mouse click/scroll/wheel · ⌘C/⌘V on kitty-class terminals
• tmux/zellij: C-t travel hub · M-{/M-} or C-PgUp/PgDn switch tabs · M-1..9 jump to tab · C-o/Ctrl+arrows move between panes · C-|/C-- splits · scrollback with the wheel or Shift+PgUp/PgDn

Everything is remappable in ~/.config/mars/keys.json; behavior knobs (autosave interval, scrollback depth, colors, timings, watch quiet threshold) live in ~/.config/mars/tuning.json, each with a plain-English description of what it does.

Troubleshooting

• Staircase output (lines drifting right, like mars help printing diagonally): your shell's terminal was left in raw mode — usually by a force-killed program. Run any mars command (it repairs the terminal automatically on startup) or stty sane.
• M-… keys do nothing (macOS): enable "Use Option as Meta" in Terminal/iTerm — or use the Ctrl-based twins (C-o, Ctrl+arrows), which always work.
• ⌘ chords do nothing: ⌘ only reaches Mars on kitty-protocol terminals (kitty, WezTerm, Ghostty, iTerm2 3.5+); elsewhere the OS keeps it. The ⌥ and M-… twins work everywhere.
• A session shows dead (cleaned up) in mars ls: the daemon crashed or the machine rebooted. Check ~/.local/state/mars/<name>.log for the reason; autosaved file changes are already on disk.
• Fancy chords (C-{, C--, ⌘C) don't fire: they need a kitty-protocol terminal. The Alt-based twins work everywhere.

More

• architecture_overview.md — a file-by-file tour of the code: what lives where and how the pieces connect.
• DESIGN.md — architecture rationale, tradeoffs, and how the pieces fit.
• key_design.md — the design doctrine and product vision (why the keys are what they are, and where Mars is going).
• AGENTS.md — instructions for AI coding agents working on Mars.