Deck

A terminal workspace for parallel coding-agent sessions.

Deck manages projects and sessions and draws the frame around them. The agent itself is a separate program running in a pseudo-terminal — claude by default, or cathode, or anything else that talks to a terminal. Deck speaks no agent protocol, which is why the agent is just a choice on the new-session form.

Two views:

• Dashboard — projects on the left, the selected project's sessions on the right, with status and age per session. tab moves keyboard focus between the two columns; the focused one carries an accent-coloured top border, and the other keeps a dimmed cursor so you can still see where it is.
• Session — a sidebar of sessions grouped by project, and a main pane that is the live agent terminal.

The pane hosts whatever program the session names — the one above is codex on its first run, before it has been signed in.

Every project and session in these images is invented. make demo builds the throwaway workspace they are taken against.

Build and install

make build      # -> ./deck
make install    # -> ~/.local/bin/deck, same place as cathode
make test
make race       # required before merging changes to internal/agent
make help       # list every target

Override the install location with PREFIX, and make install warns if it is not on your PATH:

make install PREFIX=/usr/local/bin
make uninstall
make watch      # rebuild + reinstall on save (needs entr)

Running it needs claude on PATH with claude login already done. Verify with claude then /status: anything but the subscription route means you are billing the API.

Use

cd ~/Work/some-repo
deck                        # seeds this repo as the first project
deck -agent cathode         # override the remembered agent for this run
deck -agent claude -agent-args "--permission-mode plan"
deck -agent cathode -agent-args "-mode ask"

Running cathode as the agent works and is the reason Deck hosts a process rather than speaking a protocol. One caveat for parallel sessions: every cathode instance shares $XDG_STATE_HOME/cathode, and its session list is rewritten whole rather than merged, so two cathode sessions closing together can drop entries from each other's ctrl+r picker. Conversations themselves are safe — those live in claude's own per-directory transcripts.

Launching inside a git repository registers it and puts the cursor on it.

The store is global, not per-directory. Every project and session is visible from wherever you run deck, and a session's agent runs in that session's own worktree regardless of where you launched from. So you can cd into another project, run deck, and pick up a session belonging to the first one.

A project does not have to be a git repository. A directory that only collects them — several checkouts side by side, coordinated from the parent — is a project in its own right, and an agent running there sees all of them at once. Launching deck in such a directory registers it, the same as launching inside a repository does.

Sessions in a collector run in the project directory; there is no repository at its root to branch from, so that is the default and an isolated worktree is refused with a message saying why.

a opens a directory explorer for directories you are not standing in. It starts beside the selected project, so its siblings are already on screen: ↑/↓ to move, → to open a directory, ↵ to pick one, esc to cancel. Picking a directory that is already registered, or a path that is not a directory at all, says so and leaves you where you were.

Keys

One key is taken from the agent: ctrl+g, the command prefix. Everything else reaches the agent untouched, so esc, tab, shift+tab, ctrl+c, and the arrows keep working inside claude.

ctrl+g rather than ctrl+a or ctrl+b, which are readline line-motions claude uses, and rather than ctrl+], which needs AltGr on a Nordic layout.

Chrome
↑/k ↓/j	move selection
←/h →/l	switch section
tab	switch column (dashboard) — projects ⇄ sessions
↵	open / attach
n	new session
a	add project
x	close session
t	theme picker
?	help
q	quit

Command — press ctrl+g first
^g d	dashboard
^g s	sessions
^g j / ^g k	next / previous session (stays attached if it is live)
^g 1…^g 9	jump straight to that session
^g n	new session
^g x	stop the agent
^g esc	detach from the pane
^g ↵	attach to the pane
^g q	quit
^g t	theme picker
^g ?	the full key list
^g ^g	send a literal ctrl+g to the agent

Press ^g on its own and the footer becomes this list, so the prefix teaches itself and you never have to remember the second key. Holding it also numbers the first nine sidebar cards, which is what makes ^g 1…^g 9 usable without counting. The numbers count sessions, not rows, so they run straight through a project heading.

Sessions and worktrees

Opening a session asks where it should run:

• Isolated git worktree (default) — a new branch session/<name> checked out under the state directory. Parallel sessions on one repository never collide.
• Project directory — runs in the repository itself. Simple, but two sessions here fight over the working tree.

A repository with no commits yet cannot have a worktree — there is no commit to check out. Deck says so and leaves the form open with your title intact, so switching to Project directory is one tab and one → away.

The project field steps with ←/→ and opens the full list on ↵, so it stays usable whether you have three projects or ninety.

A project is listed under the Name you give it when you register it, which defaults to the directory it sits in. e on the dashboard renames one; the path is not editable there, because changing it makes a different project rather than the same one under another name. The last field picks the agent — see Choosing the agent below.

Session names are scheming-hawk-jhgk: two words you can say out loud plus a suffix that makes the branch unique.

Closing a session stops the agent and forgets the session. It leaves the worktree on disk, because it may hold uncommitted work. The footer says where.

Agents coordinating

Sessions are isolated on purpose, which also makes them blind to each other. Deck runs a small MCP server so agents on the same project can see what their siblings are doing. Each session's agent is wired to it automatically (claude and cathode; anything else you wire yourself with -agent-args).

Choosing the agent

The new-session form has an Agent field — claude, cathode, codex, gemini — and the last choice becomes the default for the next session. Each session remembers what it started, so changing the default never relabels a session that is already running. -agent overrides the default for one run and takes any program that talks to a terminal, listed or not.

Only claude reports exact turn status, and only claude and cathode are handed a coordination config. Anything else runs perfectly well in a pane, with status inferred from output and no sibling awareness.

Tool	What the agent gets
sessions	Who else is working on this project, and the files they hold
claim	Announce paths you are about to touch; returns anyone already there
release	Give the paths back
note	Append to the project's shared log
notes	Read what other agents recorded
work	Read what another session has changed — summary and patch
analyse	Have a separate agent review a session's work; returns an id
analysis	Collect that review, with what it cost
message	Send to one sibling by name, or to all of them
inbox	Collect messages sent to you

Claims are advisory — nothing stops another process writing the file. The value is answering "is anyone else in here", which no amount of written discipline can. They are compared repo-relative, so the same file collides across worktrees, and they are released when the session stops.

Messages are a mailbox the recipient collects, not a write into its terminal. Typing into a live pane would corrupt the input of an agent mid-turn, and submitting on its behalf would let one agent put instructions into another's prompt with nobody watching. The cost of pulling is that the recipient has to ask, so every other tool result carries an unread count.

An agent can also read a sibling's work directly, and have it reviewed. work returns the summary and patch of another session's worktree, which needs nothing from that session — it is read while that agent is mid-turn and interrupts nothing. analyse goes further and starts a separate agent to review it.

That review is asynchronous, because a real one outlasts the tool timeout of whatever asked for it, and because a blocking call is invisible exactly while you would want to watch it. The reviewer is handed the diff, given no tools, and run in a mode that answers but cannot act. analysis collects the answer along with what it cost.

The sidebar shows ⊙ n for claims held, ✉ n for messages waiting, and ⚗ n · $x.xx for reviews running and what they have cost. That last one is the only thing in Deck that spends money with nobody watching it: the review has no pane, and the session that asked for it has moved on. The figure stays after the last review finishes, so a total is not lost the moment it stops moving.

Status

A claude session reports what it is doing rather than having it guessed. Deck writes a per-session hooks config and passes it with --settings. UserPromptSubmit and PostToolBatch open a turn, Stop and StopFailure close one, and the Notification subtypes that block on a person — permission_prompt, idle_prompt, agent_needs_input, elicitation_dialog, elicitation_url_dialog — mean a human is wanted.

Registering fewer of them costs a wrong dot. A turn boundary is not always one event, and some transitions are visible only through a later event rather than one of their own, so too small a set leaves a session reporting a state that never clears.

Needs you clears when the approved tool finishes rather than when you approve it, so a long tool call still reads Needs you while it runs. Narrowing that is in docs/backlog.md.

Not every way of ending a turn is observable. A pane that has gone quiet for ten seconds therefore overrides a Working report, which covers any turn-end that arrives without an event rather than one particular case.

Dot	Meaning
◉ Working	a turn is running
◆ Needs you	a permission prompt, a question, or a turn that hit an API error
◉ Idle	the turn finished
◍ Exited	the process is gone
○ Closed	never opened, or stopped

Needs you is the one the old heuristic could never show: an agent blocked on a prompt prints nothing, so it looked idle.

The hooks post to the same localhost server the coordination tools use, with the session id in the URL. Their timeout is 5 seconds rather than the 600s default — if Deck is gone, a turn boundary should not stall the agent for ten minutes.

Sessions run with -agent cathode keep the heuristic: cathode spawns its own claude with its own arguments, so a --settings given to cathode would never reach the process the hooks describe.

Notes live in $XDG_STATE_HOME/deck/notes/<project>.jsonl. They are append-only because several agents write at once, capped at 50 on read, and the file itself is trimmed to its newest 100 entries once it passes 400 — an append-only log with no trimming grows for the life of the project.

Themes

t opens the picker (^g t from an attached pane). The frame restyles as the cursor moves, so you judge a theme by the app rather than by its name; ↵ keeps it, esc puts back what you had.

Twelve themes, using the same ids and source colours as cathode: Cinder (default), BBS, Dracula, Nord, Solarized Dark, Tokyo Night, Gruvbox Dark, One Dark, Monokai, Catppuccin Mocha, GitHub Dark, Rosé Pine. A name means the same thing in both tools.

They are deliberately not shared through a common file. The two apps have different role vocabularies — cathode needs diff-gutter and "you"-label colours Deck has no use for, and Deck's selected-row tint is dark where cathode's equivalent is a bright fill — so a shared schema would have to satisfy both forever to save an edit made twice a year.

The choice persists in $XDG_STATE_HOME/deck/settings.json.

State

Everything lives under $XDG_STATE_HOME/deck (default ~/.local/state/deck), which is where cathode keeps its state too:

state.json                  projects and sessions
settings.json               preferences: the chosen theme
worktrees/<project>/<name>  session worktrees
notes/<project>.jsonl       the shared agent log
sessions/<id>.mcp.json      generated coordination config per session

Known friction

• Claude Code asks you to trust each new worktree. A fresh worktree is a new folder, so the trust prompt appears once per isolated session. Press 1 then ↵. Deck does not pre-approve folders on your behalf.
• Mouse is wheel-only. Wheel events scroll the attached pane. Clickable nav items, tabs, and session cards need bubblezone, which is not wired in yet.
• Status is a heuristic for agents that do not report. claude sessions report real turn boundaries through hooks (see Status below). Anything else — cathode, or a custom agent — falls back to "printed something in the last 900ms", which is wrong exactly when an agent thinks quietly.

Licence

Apache License 2.0. See LICENSE.