Keep the big blind moving one player at a time when somebody leaves out of the blinds

Passing the button to the next player is right until a chair between the button and
the blinds empties. Then it pulls the whole blind order forward a place. Measured,
four-handed, button on Ben, blinds Cal and Dee, with Cal cashing out:

    tool:    button Dee, small blind Ann, big blind Ben
    correct: dead button on Cal's chair, small blind Dee, big blind Ann

Ann is never asked for the big blind she owes, and Ben pays one a full orbit early.
That is a real big blind out of a real stack, and it happens every time somebody
stands up out of the blinds — which in a cash game is constantly. It is also the
kind of thing the dealer gets blamed for, because the tool is the thing everyone at
the table is reading position off.

The dead button rule holds the rotation to the seats for one hand instead of to the
players. The button follows the small blind round, which at a table with nobody
missing is the same next-player-along it always was; when that player has gone the
button rests on their empty chair for a hand, and when the big blind has gone no
small blind is posted. Either way the big blind advances exactly one player, which
is the whole point of it.

Worked out from who actually posted last hand rather than from the seating as it
stands, because by the time the question is asked the people it turns on are the
ones who have left. Heads-up is exempt — the button is the small blind there and
there is no position to leave dead — as is a table too sparse to have a rotation to
hold to, and a dealer who moves the button or names a blind by hand overrules it.

Both dead positions are said out loud rather than left to look like a fault: the
deal prompt explains them in a sentence, and the dead button goes hollow and dashed
so the felt agrees with the words.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015bnp7xKUPFFSpwkYNFaPgb

JoshHeaps.Net/wwwroot/js/casino/holdem/main.js

@@ -121,6 +121,11 @@ document.addEventListener("DOMContentLoaded", () => {
                 ? `Button on ${nameOf(index)} — blinds taken back and re-posted.`
                 : `Button on ${nameOf(index)}.`, () => {
                 state.dealerSeatIndex = index;
+                // Putting the button somewhere by hand is the dealer overruling the
+                // rotation, dead positions included. Leaving them set would hold a
+                // small blind dead at a table whose button has moved out from under it.
+                state.deadButton = false;
+                state.deadSmallBlind = false;
                 if (willRepost) Betting.repostBlinds(state);
             });
         },
@@ -376,12 +381,19 @@ document.addEventListener("DOMContentLoaded", () => {
             if (!ok) return;
         }
 
-        // startNextHand moves the button on by one; say where it landed so the
-        // dealer can confirm the rotation without hunting for the badge.
-        const nextDealer = HoldemState.nextSeatIndex(state, state.dealerSeatIndex, 1);
-        const where = state.dedicatedDealer
-            ? `small blind on seat ${HoldemState.nextSeatIndex(state, nextDealer, 1) + 1}`
-            : `button on seat ${nextDealer + 1}`;
+        // Say where the button landed so the dealer can confirm the rotation without
+        // hunting for the badge. Asked of the rotation itself rather than guessed at as
+        // "the next chair along" — which was only ever right at a table with nobody
+        // missing, and is the exact thing the dead button makes untrue.
+        const rotation = HoldemState.nextButtonRotation(state);
+        const nextDealer = rotation.buttonIndex !== null
+            ? rotation.buttonIndex
+            : HoldemState.buttonSeatForDeal({ ...state, dealerSeatIndex: HoldemState.nextSeatIndex(state, state.dealerSeatIndex, 1) });
+        const where = rotation.deadButton
+            ? `dead button on seat ${nextDealer + 1}`
+            : state.dedicatedDealer
+                ? `small blind on seat ${HoldemState.nextSeatIndex(state, nextDealer, 1) + 1}`
+                : `button on seat ${nextDealer + 1}`;
         const discarded = unresolved > Betting.EPSILON_CHIPS
             ? ` ${Money.format(unresolved)} taken off the table.`
             : "";