diff --git a/server/match/player/economy.js b/server/match/player/economy.js
index bd0686bd..67a7a58f 100644
--- a/server/match/player/economy.js
+++ b/server/match/player/economy.js
@@ -209,7 +209,9 @@ export class PlayerEconomy {
     if (loc.piece.kind !== 'chess') return fail(ERR.BAD_TARGET, loc.piece.kind === 'item' ? 'items cannot be sold' : 'tokens cannot be sold');
     const piece = loc.piece;
     // its equipment returns to the hand (overflow temp): refuse rather than destroy it when there is no room
-    const room = this.hand.filter((x) => x == null).length + this.temp.filter((x) => x == null).length + (loc.area === 'hand' || loc.area === 'temp' ? 1 : 0);
+    // Removing the owner's summon stacks frees one slot per stack, regardless of its summon count.
+    const freed = (x) => x == null || (x.kind === 'token' && x.ownerUid === piece.uid);
+    const room = this.hand.filter(freed).length + this.temp.filter(freed).length + (loc.area === 'hand' || loc.area === 'temp' ? 1 : 0);
     if ((piece.items || []).length > room) return fail(ERR.HAND_FULL, 'no room for the equipment');
     this._detach(loc);
     this.removeTokensOf(piece.uid);
diff --git a/test/match/sell-capacity.test.js b/test/match/sell-capacity.test.js
new file mode 100644
index 00000000..961bdd10
--- /dev/null
+++ b/test/match/sell-capacity.test.js
@@ -0,0 +1,153 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { ERR } from '../../shared/constants.js';
+import { makeMatch, legalTileFor, checkInvariants } from './harness.js';
+
+const SILENCE = 'chess_char_2_02_a';
+const CATHY = 'chess_char_4_11_a';
+const EQUIPMENT = 'chess_item_1_02_e_b'; // Elite equipment does not merge.
+
+function setup(t) {
+  const h = makeMatch({ mode: 'solo', difficulty: 'FUNNY', seed: 1, fake: true }).start();
+  t.after(() => h.m.dispose());
+  h.toPrep(1);
+  return { h, m: h.m, ps: h.ps('p_0') };
+}
+
+function deploy(m, ps, piece, chessId = piece.id) {
+  const tile = legalTileFor(m, ps, chessId);
+  assert.ok(tile);
+  assert.deepEqual(m.handle(ps.playerId, { t: 'g.move', uid: piece.uid, to: { area: 'board', row: tile[0], col: tile[1] } }), { ok: true });
+}
+
+function equip(m, ps, owner, count) {
+  return Array.from({ length: count }, () => {
+    const item = ps.acquireItem(EQUIPMENT, { silent: true });
+    assert.ok(item);
+    assert.deepEqual(m.handle(ps.playerId, { t: 'g.equip', itemUid: item.uid, targetUid: owner.uid }), { ok: true });
+    return item;
+  });
+}
+
+function fillStorage(ps) {
+  while ([...ps.hand, ...ps.temp].some((p) => p === null)) assert.ok(ps.acquireItem(EQUIPMENT, { silent: true }));
+}
+
+function swapIntoTemp(m, ps, piece) {
+  const idx = ps.hand.indexOf(piece);
+  const filler = ps.temp.find((p) => p?.kind === 'item');
+  assert.ok(idx >= 0 && filler);
+  assert.deepEqual(m.handle(ps.playerId, { t: 'g.move', uid: filler.uid, to: { area: 'hand', idx } }), { ok: true });
+  assert.equal(ps.find(piece.uid).area, 'temp');
+}
+
+function snapshot(ps) {
+  return structuredClone({
+    hand: ps.hand, temp: ps.temp, board: ps.board, funds: ps.funds, pendingFunds: ps.pendingFunds,
+    stats: ps.stats, round: ps.round, tempDue: ps._tempDue,
+  });
+}
+
+const inventory = (ps) => [...ps.hand, ...ps.temp, ...ps.board.values()].filter(Boolean);
+const tokensOf = (ps, owner) => inventory(ps).filter((p) => p.kind === 'token' && p.ownerUid === owner.uid);
+
+for (const area of ['hand', 'temp']) {
+  for (const itemCount of [1, 2]) {
+    test(`sale uses the freed ${area} summon slot to return ${itemCount} equipment item(s)`, (t) => {
+      const { h, m, ps } = setup(t);
+      const owner = ps.acquireChess(SILENCE, { silent: true });
+      deploy(m, ps, owner);
+      const items = equip(m, ps, owner, itemCount);
+      const other = ps.acquireChess(SILENCE, { silent: true });
+      deploy(m, ps, other);
+      const [stack] = tokensOf(ps, owner);
+      fillStorage(ps);
+      if (area === 'temp') swapIntoTemp(m, ps, stack);
+      assert.equal(ps.find(stack.uid).area, area);
+      // Two items need one existing free slot as well as the slot released by the stack.
+      if (itemCount === 2) {
+        const filler = ps.temp.find((p) => p?.kind === 'item');
+        assert.deepEqual(m.handle(ps.playerId, { t: 'g.destroy', uid: filler.uid }), { ok: true });
+      }
+      const untouched = structuredClone(inventory(ps).filter((p) => p !== owner && p !== stack));
+      const funds = ps.funds;
+      const poolBefore = m.pool.left(SILENCE);
+      const copies = owner.poolCopies;
+      assert.deepEqual(m.handle(ps.playerId, { t: 'g.sell', uid: owner.uid }), { ok: true });
+      assert.equal(ps.find(owner.uid), null);
+      assert.deepEqual(tokensOf(ps, owner), []);
+      assert.equal(ps.funds, funds + 1);
+      assert.equal(m.pool.left(SILENCE), poolBefore + copies);
+      assert.deepEqual(owner.items, []);
+      for (const item of items) {
+        assert.equal(ps.find(item.uid).piece, item, 'the original equipment object and UID return');
+        assert.ok(['hand', 'temp'].includes(ps.find(item.uid).area));
+      }
+      assert.equal(ps.find(items[0].uid).area, area, 'hand is preferred, with overflow into temp');
+      for (const piece of untouched) assert.deepEqual(ps.find(piece.uid).piece, piece);
+      assert.equal(inventory(ps).length, untouched.length + items.length);
+      assert.deepEqual(h.logs.warn, []);
+      checkInvariants(m);
+    });
+  }
+}
+
+for (const { name, ownerId, area, itemCount, stackCount } of [
+  { name: 'one hand stack cannot hold two equipment items', ownerId: SILENCE, area: 'hand', itemCount: 2, stackCount: 1 },
+  { name: 'one temp stack cannot hold two equipment items', ownerId: SILENCE, area: 'temp', itemCount: 2, stackCount: 1 },
+  { name: 'a two-summon stack frees only one slot', ownerId: CATHY, area: 'hand', itemCount: 2, stackCount: 2 },
+  { name: 'board summons and foreign stacks free no usable slot', ownerId: SILENCE, area: 'board', itemCount: 1, stackCount: 1 },
+]) {
+  test(`sale rejects atomically when ${name}`, (t) => {
+    const { m, ps } = setup(t);
+    const owner = ps.acquireChess(ownerId, { silent: true });
+    deploy(m, ps, owner);
+    const items = equip(m, ps, owner, itemCount);
+    const other = ps.acquireChess(SILENCE, { silent: true });
+    deploy(m, ps, other);
+    const [stack] = tokensOf(ps, owner);
+    assert.equal(stack.count, stackCount);
+    if (area === 'board') deploy(m, ps, stack, owner.id);
+    fillStorage(ps);
+    if (area === 'temp') swapIntoTemp(m, ps, stack);
+    assert.equal(ps.find(stack.uid).area, area);
+    const before = snapshot(ps);
+    const poolBefore = m.pool.left(ownerId);
+    assert.equal(m.handle(ps.playerId, { t: 'g.sell', uid: owner.uid }).error, ERR.HAND_FULL);
+    assert.deepEqual(snapshot(ps), before, 'pieces, equipment, funds, and bookkeeping remain unchanged');
+    assert.equal(m.pool.left(ownerId), poolBefore);
+    for (const item of items) assert.equal(ps.find(item.uid).area, 'equipped');
+    checkInvariants(m);
+    // Free exactly one additional slot and retry the same public intent.
+    const filler = ps.temp.find((p) => p?.kind === 'item');
+    assert.deepEqual(m.handle(ps.playerId, { t: 'g.destroy', uid: filler.uid }), { ok: true });
+    assert.deepEqual(m.handle(ps.playerId, { t: 'g.sell', uid: owner.uid }), { ok: true });
+    assert.equal(ps.find(owner.uid), null);
+    assert.deepEqual(tokensOf(ps, owner), []);
+    assert.equal(ps.funds, before.funds + 1);
+    for (const item of items) {
+      assert.equal(ps.find(item.uid).piece, item);
+      assert.ok(['hand', 'temp'].includes(ps.find(item.uid).area));
+    }
+    assert.equal(tokensOf(ps, other).length, 1);
+    checkInvariants(m);
+  });
+}
+
+for (const area of ['hand', 'temp']) {
+  test(`sale still counts the operator's own ${area} slot`, (t) => {
+    const { m, ps } = setup(t);
+    const owner = ps.acquireChess(SILENCE, { silent: true });
+    const [item] = equip(m, ps, owner, 1);
+    fillStorage(ps);
+    if (area === 'temp') swapIntoTemp(m, ps, owner);
+    assert.equal(ps.find(owner.uid).area, area);
+    const funds = ps.funds;
+    assert.deepEqual(m.handle(ps.playerId, { t: 'g.sell', uid: owner.uid }), { ok: true });
+    assert.equal(ps.find(owner.uid), null);
+    assert.equal(ps.find(item.uid).piece, item);
+    assert.equal(ps.find(item.uid).area, area);
+    assert.equal(ps.funds, funds + 1);
+    checkInvariants(m);
+  });
+}