Claude Code plugin

A backgammon position appears in a pane while Claude is working. When Claude needs you, your place is kept.

 13  14  15  16  17  18     19  20  21  22  23  24
 ○   ·   ·   ·   ·   ·   │  ●   ●   ·   ●   ●   ●
 ○   ·   ·   ·   ·   ·   │  ●   ●   ·   ●   ●   ·
 ·   ·   ·   ·   ·   ·   │  ●   ·   ·   ·   ●   ·
 ·   ·   ·   ·   ·   ·   │  ·   ·   ·   ·   ·   ·
 ·   ·   ·   ·   ·   ·   │  ·   ·   ·   ·   ·   ·
────────────────────── [4 1] ──────────────────────
 ·   ·   ·   ·   ·   ·   │  ○   ·   ·   ·   ·   ·
 ·   ·   ·   ·   ·   ·   │  ○   ·   ·   ·   ·   ·
 ·   ·   ·   ○   ○   ·   │  ○   ·   ·   ·   ·   ·
 ●   ·   ·   ○   ○   ○   │  ○   ·   ·   ·   ·   ●
 ●   ·   ·   ○   ○   ○   │  ○   ·   ·   ·   ·   ●
 12  11  10  9   8   7      6   5   4   3   2   1

you roll 4-1 — what is the play?

Install

claude plugin marketplace add BowTiedBlox/gammonchain
claude plugin install gammonchain@gammonchain

What it is for

The gap between submitting a prompt and reading the answer is a minute of nothing. It is not long enough to do anything with and it is exactly long enough to break concentration. The plugin fills it with a real decision: one position from a match this server recorded, chosen because a reference engine says one play is clearly best, graded to a hundredth of a point of equity.

It is the same position pipeline as the daily puzzle, served from a pool instead of one a day.

The handover is the point

A break that gets snatched away is not a break. The rules the plugin follows, in the order they matter:

1. Claude finishing does not take the puzzle away. The pane says Claude is done and waits for your answer. You will not lose a position you were thinking about because the model happened to finish.
2. When Claude needs you, that wins immediately. The clock stops, a notice appears, and one key hands you back to the prompt. The same position is still there when you come back, with the clock where you left it — being asked a question should not cost you the position you were thinking about.
3. A short turn is not a break. Nothing opens until Claude has been working for two seconds, because a turn that finished before you looked away was not a wait.

Pressing Esc gives the keyboard back to the prompt without closing the pane.

Playing

Type the play the way you would write it down, and press Enter.

You type	It means
13/7 8/7	two checkers to your 7 point
24/18/13	one checker, two hops
bar/20	entering from the bar
13/11(2)	the same hop twice
6/off	bearing off

Hits are inferred, so 13/7* and 13/7 are the same play. The numbers down both edges are always your numbers, whichever seat the position puts you in, so what you see is what you type.

A play the rules refuse is refused in the pane, with the reason — the plugin carries the server's own rules engine, copied verbatim rather than reimplemented, so it agrees with the server about what is legal and can still check a move with the network down.

Three words work in the same field, because a text field takes every keystroke while it has the keyboard:

You type	It does
?	lists the legal plays — your options, never which one is best
n	next position
q	close the pane

Commands

Command	What it does
/gammonchain	open a position now, mid-turn if you like
/gammonchain-pause	stop opening positions for this session
/gammonchain-stats	this machine's key, today's score, what is left of the allowance

Your account is a key

There is no sign-up, no password and no email. The first run generates an Ed25519 key pair and keeps the private half in ~/.gammonchain/plugin-key.json, mode 0600. The public half is the identity gammonchain knows you by, and it is what your score is attached to — the same kind of key, and the same security model, as a player in the browser.

Every request is signed rather than carrying a token. See the HTTP API for the scheme.

Keep that file. Losing it means a new identity; copying it to another machine means both machines are you.

On macOS, GAMMONCHAIN_KEY_STORE=keychain puts the key in the login keychain instead. It is not the default, because security will only accept a secret as a command-line argument, where it is briefly visible to ps — and the file it would replace is readable at rest by anyone who could run that ps anyway.

Answers are graded on the server

A position arrives without its answers. Nothing in the plugin knows which play is best until you have committed to one, which is also why a hint can only list your options.

Grading needs the network. With no connection your answer goes on a queue and is replayed later, and until then the pane says answer saved, not correct. The first answer to a position stands — on the server and in the queue — so a replay can never change a verdict you have already seen.

Settings

Variable	Default	What it does
GAMMONCHAIN_URL	https://gammonchain.com	the server to play against
GAMMONCHAIN_DIR	~/.gammonchain	where the key lives
GAMMONCHAIN_KEY_STORE	file	keychain to use the macOS login keychain
GAMMONCHAIN_TIMEOUT_MS	8000	how long to wait before deciding the network is gone

Thirty answers a day are free. The pane shows what is left and when the allowance comes back, which is midnight UTC. Skipping a position you do not fancy costs nothing, because the allowance counts answers rather than positions served.

If the pane does not appear

A pane a plugin opens by itself needs a terminal at least 144 columns wide, or 110 once you have opened this one yourself. That is Claude Code's rule, not the plugin's, and it exists so a plugin cannot take over a small screen. /gammonchain opens the pane at any width, and when a pane is waiting for room the plugin says so above the prompt instead of showing you nothing.

Running it against your own server

Point GAMMONCHAIN_URL at your instance. The pool routes exist on any gammonchain server; an instance with no recorded matches has nothing to build positions from, so fill it first.