diff --git a/lang/dev/lobby.json b/lang/dev/lobby.json
index 76b3095dc..9df141662 100644
--- a/lang/dev/lobby.json
+++ b/lang/dev/lobby.json
@@ -96,7 +96,9 @@
                 "declineInvite": "Denlice",
                 "kickMember": "Kcik Meembr",
                 "cancelInvite": "Ceancl Iivnte",
-                "noInvites": "No crerunt iiinnattvos."
+                "noInvites": "You crelnrtuy hvae no piendng iiinnattvos.",
+                "partyTooLarge": "Party Too Lgare",
+                "partyTooLargeTooltip": "Your party is too lgare to jion tihs qeuue."
             },
             "watch": {
                 "replays": {
@@ -153,9 +155,11 @@
                     "searchGame": "Sacreh gmae",
                     "joinRequested": "Jniniog qeuue",
                     "searchingForOpponent": "Searnichg for oeonnppt",
-                    "matchFound": "Mceathd - Ccilk to Raedy",
-                    "accepted": "Acpteecd",
-                    "cancel": "Ceancl"
+                    "matchFound": "Ccilk to Raedy ({seconds})",
+                    "accepted": "Acpteecd ({players} raedy)",
+                    "cancel": "Ceancl",
+                    "partyTooLarge": "Party Too Lgare",
+                    "partyTooLargeTooltip": "Your party is too lgare to jion tihs qeuue."
                 },
                 "modalTitle": "Macanihmtkg Quuee Daleits",
                 "modal": {
diff --git a/lang/en/lobby.json b/lang/en/lobby.json
index 81c231c38..e84408a8c 100644
--- a/lang/en/lobby.json
+++ b/lang/en/lobby.json
@@ -96,7 +96,9 @@
                 "declineInvite": "Decline",
                 "kickMember": "Kick Member",
                 "cancelInvite": "Cancel Invite",
-                "noInvites": "No current invitations."
+                "noInvites": "You currently have no pending invitations.",
+                "partyTooLarge": "Party Too Large",
+                "partyTooLargeTooltip": "Your party is too large to join this queue."
             },
             "watch": {
                 "replays": {
@@ -153,9 +155,11 @@
                     "searchGame": "Search game",
                     "joinRequested": "Joining queue",
                     "searchingForOpponent": "Searching for opponent",
-                    "matchFound": "Matched - Click to Ready",
-                    "accepted": "Accepted",
-                    "cancel": "Cancel"
+                    "matchFound": "Click to Ready ({seconds})",
+                    "accepted": "Accepted ({players} ready)",
+                    "cancel": "Cancel",
+                    "partyTooLarge": "Party Too Large",
+                    "partyTooLargeTooltip": "Your party is too large to join this queue."
                 },
                 "modalTitle": "Matchmaking Queue Details",
                 "modal": {
diff --git a/src/renderer/assets/languages/cs.json b/src/renderer/assets/languages/cs.json
index d847f8005..1ee4c453a 100644
--- a/src/renderer/assets/languages/cs.json
+++ b/src/renderer/assets/languages/cs.json
@@ -2079,7 +2079,9 @@
                 "declineInvite": null,
                 "kickMember": null,
                 "cancelInvite": null,
-                "noInvites": null
+                "noInvites": null,
+                "partyTooLarge": null,
+                "partyTooLargeTooltip": null
             },
             "watch": {
                 "replays": {
@@ -2138,7 +2140,9 @@
                     "searchingForOpponent": null,
                     "matchFound": null,
                     "accepted": null,
-                    "cancel": null
+                    "cancel": null,
+                    "partyTooLarge": null,
+                    "partyTooLargeTooltip": null
                 },
                 "modalTitle": null,
                 "modal": {
diff --git a/src/renderer/assets/languages/de.json b/src/renderer/assets/languages/de.json
index ef377fd8f..e2019f3ae 100644
--- a/src/renderer/assets/languages/de.json
+++ b/src/renderer/assets/languages/de.json
@@ -1950,7 +1950,9 @@
                 "declineInvite": null,
                 "kickMember": null,
                 "cancelInvite": null,
-                "noInvites": null
+                "noInvites": null,
+                "partyTooLarge": null,
+                "partyTooLargeTooltip": null
             },
             "watch": {
                 "replays": {
@@ -2009,7 +2011,9 @@
                     "searchingForOpponent": null,
                     "matchFound": null,
                     "accepted": null,
-                    "cancel": null
+                    "cancel": null,
+                    "partyTooLarge": null,
+                    "partyTooLargeTooltip": null
                 },
                 "modalTitle": null,
                 "modal": {
diff --git a/src/renderer/assets/languages/dev.json b/src/renderer/assets/languages/dev.json
index ac270d559..55ea3a297 100644
--- a/src/renderer/assets/languages/dev.json
+++ b/src/renderer/assets/languages/dev.json
@@ -96,7 +96,9 @@
                 "declineInvite": "Denlice",
                 "kickMember": "Kcik Meembr",
                 "cancelInvite": "Ceancl Iivnte",
-                "noInvites": "No crerunt iiinnattvos."
+                "noInvites": "You crelnrtuy hvae no piendng iiinnattvos.",
+                "partyTooLarge": "Party Too Lgare",
+                "partyTooLargeTooltip": "Your party is too lgare to jion tihs qeuue."
             },
             "watch": {
                 "replays": {
@@ -153,9 +155,11 @@
                     "searchGame": "Sacreh gmae",
                     "joinRequested": "Jniniog qeuue",
                     "searchingForOpponent": "Searnichg for oeonnppt",
-                    "matchFound": "Mceathd - Ccilk to Raedy",
-                    "accepted": "Acpteecd",
-                    "cancel": "Ceancl"
+                    "matchFound": "Ccilk to Raedy ({seconds})",
+                    "accepted": "Acpteecd ({players} raedy)",
+                    "cancel": "Ceancl",
+                    "partyTooLarge": "Party Too Lgare",
+                    "partyTooLargeTooltip": "Your party is too lgare to jion tihs qeuue."
                 },
                 "modalTitle": "Macanihmtkg Quuee Daleits",
                 "modal": {
diff --git a/src/renderer/assets/languages/en.json b/src/renderer/assets/languages/en.json
index f8ffd8734..2d7298e97 100644
--- a/src/renderer/assets/languages/en.json
+++ b/src/renderer/assets/languages/en.json
@@ -1927,7 +1927,9 @@
                 "declineInvite": "Decline",
                 "kickMember": "Kick Member",
                 "cancelInvite": "Cancel Invite",
-                "noInvites": "No current invitations."
+                "noInvites": "You currently have no pending invitations.",
+                "partyTooLarge": "Party Too Large",
+                "partyTooLargeTooltip": "Your party is too large to join this queue."
             },
             "watch": {
                 "replays": {
@@ -1984,9 +1986,11 @@
                     "searchGame": "Search game",
                     "joinRequested": "Joining queue",
                     "searchingForOpponent": "Searching for opponent",
-                    "matchFound": "Matched - Click to Ready",
-                    "accepted": "Accepted",
-                    "cancel": "Cancel"
+                    "matchFound": "Click to Ready ({seconds})",
+                    "accepted": "Accepted ({players} ready)",
+                    "cancel": "Cancel",
+                    "partyTooLarge": "Party Too Large",
+                    "partyTooLargeTooltip": "Your party is too large to join this queue."
                 },
                 "modalTitle": "Matchmaking Queue Details",
                 "modal": {
diff --git a/src/renderer/assets/languages/fr.json b/src/renderer/assets/languages/fr.json
index f5b150161..f448c0969 100644
--- a/src/renderer/assets/languages/fr.json
+++ b/src/renderer/assets/languages/fr.json
@@ -3932,7 +3932,9 @@
                 "declineInvite": null,
                 "kickMember": null,
                 "cancelInvite": null,
-                "noInvites": null
+                "noInvites": null,
+                "partyTooLarge": null,
+                "partyTooLargeTooltip": null
             },
             "watch": {
                 "replays": {
@@ -3991,7 +3993,9 @@
                     "searchingForOpponent": null,
                     "matchFound": null,
                     "accepted": null,
-                    "cancel": null
+                    "cancel": null,
+                    "partyTooLarge": null,
+                    "partyTooLargeTooltip": null
                 },
                 "modalTitle": null,
                 "modal": {
diff --git a/src/renderer/assets/languages/ru.json b/src/renderer/assets/languages/ru.json
index cfb57d879..50a567c18 100644
--- a/src/renderer/assets/languages/ru.json
+++ b/src/renderer/assets/languages/ru.json
@@ -3901,7 +3901,9 @@
                 "declineInvite": null,
                 "kickMember": null,
                 "cancelInvite": null,
-                "noInvites": null
+                "noInvites": null,
+                "partyTooLarge": null,
+                "partyTooLargeTooltip": null
             },
             "watch": {
                 "replays": {
@@ -3960,7 +3962,9 @@
                     "searchingForOpponent": null,
                     "matchFound": null,
                     "accepted": null,
-                    "cancel": null
+                    "cancel": null,
+                    "partyTooLarge": null,
+                    "partyTooLargeTooltip": null
                 },
                 "modalTitle": null,
                 "modal": {
diff --git a/src/renderer/assets/languages/zh.json b/src/renderer/assets/languages/zh.json
index 2210de24a..1178305bb 100644
--- a/src/renderer/assets/languages/zh.json
+++ b/src/renderer/assets/languages/zh.json
@@ -4043,7 +4043,9 @@
                 "declineInvite": null,
                 "kickMember": null,
                 "cancelInvite": null,
-                "noInvites": null
+                "noInvites": null,
+                "partyTooLarge": null,
+                "partyTooLargeTooltip": null
             },
             "watch": {
                 "replays": {
@@ -4102,7 +4104,9 @@
                     "searchingForOpponent": null,
                     "matchFound": null,
                     "accepted": null,
-                    "cancel": null
+                    "cancel": null,
+                    "partyTooLarge": null,
+                    "partyTooLargeTooltip": null
                 },
                 "modalTitle": null,
                 "modal": {
diff --git a/src/renderer/composables/usePartySizeMatchmaking.ts b/src/renderer/composables/usePartySizeMatchmaking.ts
new file mode 100644
index 000000000..7ab43ebea
--- /dev/null
+++ b/src/renderer/composables/usePartySizeMatchmaking.ts
@@ -0,0 +1,59 @@
+// SPDX-FileCopyrightText: 2025 The BAR Lobby Authors
+//
+// SPDX-License-Identifier: MIT
+
+import { matchmakingStore } from "@renderer/store/matchmaking.store";
+import { partyStore } from "@renderer/store/party.store";
+import { ref, watch } from "vue";
+
+export function usePartySizeMatchmaking() {
+    const partyTooLarge = ref(false);
+
+    watch(
+        () => ({
+            activeParty: partyStore.activeParty,
+            queueId: matchmakingStore.selectedQueue,
+            playlists: [...matchmakingStore.playlists],
+            // Spreading map entries forces Vue to evaluate the Map's contents
+            members: [...(partyStore.parties.get(partyStore.activeParty ?? "")?.members ?? [])],
+            invited: [...(partyStore.parties.get(partyStore.activeParty ?? "")?.invited ?? [])],
+        }),
+        (newData) => {
+            const { activeParty, queueId, playlists } = newData;
+
+            if (!activeParty || !queueId || !playlists.length) {
+                partyTooLarge.value = false;
+                return;
+            }
+
+            const party = partyStore.parties.get(activeParty);
+            const playlist = playlists.find((p) => p.id === queueId);
+
+            if (!party || !playlist) {
+                partyTooLarge.value = false;
+                return;
+            }
+
+            partyTooLarge.value = party.members.length > playlist.teamSize;
+        },
+        { immediate: true }
+    );
+
+    return {
+        partyTooLarge,
+    };
+}
+
+export function getPartySize() {
+    const activeParty = partyStore.activeParty;
+    if (!activeParty) {
+        return 0;
+    }
+
+    const party = partyStore.parties.get(activeParty);
+    if (!party) {
+        return 0;
+    }
+
+    return party.members.length;
+}
diff --git a/src/renderer/store/matchmaking.store.ts b/src/renderer/store/matchmaking.store.ts
index e7b8cd523..9f1cef490 100644
--- a/src/renderer/store/matchmaking.store.ts
+++ b/src/renderer/store/matchmaking.store.ts
@@ -16,6 +16,11 @@ import { notificationsApi } from "@renderer/api/notifications";
 import { isTachyonErrorForCommand, tachyonRequest } from "@renderer/api/tachyon";
 import { onWentOffline } from "@renderer/utils/offline-signal";
 
+// The server is the authority on the real ready-up deadline and will send its own
+// matchmaking/cancelled event if we miss it; this margin just narrows the window
+// where our local countdown and the server's deadline can disagree.
+const READY_TIMEOUT_SAFETY_MARGIN_MS = 100;
+
 export enum MatchmakingStatus {
     Idle = "Idle",
     JoinRequested = "JoinRequested",
@@ -43,6 +48,9 @@ export const matchmakingStore: {
             maps: string[];
         };
     };
+    queueTimeout?: number;
+    readyCountdownInterval?: number;
+    readySecondsRemaining?: number;
 } = reactive({
     isInitialized: false,
     isDrawerOpen: false,
@@ -55,8 +63,23 @@ export const matchmakingStore: {
     playersReady: 0,
     playersQueued: 0,
     downloadsRequired: {},
+    queueTimeout: undefined,
+    readyCountdownInterval: undefined,
+    readySecondsRemaining: undefined,
 });
 
+function clearReadyTimers() {
+    if (matchmakingStore.queueTimeout !== undefined) {
+        window.clearTimeout(matchmakingStore.queueTimeout);
+        matchmakingStore.queueTimeout = undefined;
+    }
+    if (matchmakingStore.readyCountdownInterval !== undefined) {
+        window.clearInterval(matchmakingStore.readyCountdownInterval);
+        matchmakingStore.readyCountdownInterval = undefined;
+    }
+    matchmakingStore.readySecondsRemaining = undefined;
+}
+
 function onQueueUpdateEvent(data: MatchmakingQueueUpdateEventData) {
     console.log("Tachyon event: matchmaking/queueUpdate:", data);
     matchmakingStore.playersQueued = data.playersQueued;
@@ -64,6 +87,7 @@ function onQueueUpdateEvent(data: MatchmakingQueueUpdateEventData) {
 
 function onLostEvent() {
     console.log("Tachyon event: matchmaking/lost: no data");
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.Searching;
 }
 
@@ -74,6 +98,7 @@ function onFoundUpdateEvent(data: MatchmakingFoundUpdateEventData) {
 
 function onCancelledEvent(data: MatchmakingCancelledEventData) {
     console.log("Tachyon event: matchmaking/cancelled:", data);
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.Idle;
     if (data.reason === "version_changed") {
         sendListRequest();
@@ -82,16 +107,24 @@ function onCancelledEvent(data: MatchmakingCancelledEventData) {
 
 function onFoundEvent(data: MatchmakingFoundEventData) {
     console.log("Tachyon event: matchmaking/found:", data);
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.MatchFound;
-    // Per spec, we have 10 seconds to send the ``matchmaking/ready`` request or we get cancelled from queue.
-    // Probably better to track this timer on the UI side because the user will either need to 'ready' or 'cancel'
-    // and they need to know this. Plus the UI has to "pop up" because they need to respond to it.
-    // But we don't want to be "triggering" the UI from the store. Instead, we should add a watcher,
-    // and when this value updates to MatchFound we can start our timer. Probably want a progress bar "counting down" too.
+    // Deadline is our local prediction of the server's timeout, not the source of truth for it.
+    const deadline = Date.now() + data.timeoutMs - READY_TIMEOUT_SAFETY_MARGIN_MS;
+    matchmakingStore.readySecondsRemaining = Math.max(0, Math.ceil((deadline - Date.now()) / 1000));
+    matchmakingStore.readyCountdownInterval = window.setInterval(() => {
+        matchmakingStore.readySecondsRemaining = Math.max(0, Math.ceil((deadline - Date.now()) / 1000));
+    }, 1000);
+    matchmakingStore.queueTimeout = window.setTimeout(() => {
+        clearReadyTimers();
+        matchmakingStore.status = MatchmakingStatus.Idle;
+    }, deadline - Date.now());
 }
 
 function onQueuesJoinedEvent(data: MatchmakingQueuesJoinedEventData) {
     console.log("Tachyon event: matchmaking/queuesJoined:", data);
+    // Current design is a single queue joined at a time. If the user has a *different* queue selected when their party joins, we switch so they match their party's selection.
+    matchmakingStore.selectedQueue = data.queues[0];
     notificationsApi.alert({ text: "Successfully joined matchmaking queue(s)", severity: "info" });
     matchmakingStore.status = MatchmakingStatus.Searching;
 }
@@ -211,6 +244,7 @@ async function sendQueueRequest() {
  * Sends a Tachyon 'matchmaking/cancel' request.
  */
 async function sendCancelRequest() {
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.Idle;
     try {
         const response = await window.tachyon.request("matchmaking/cancel");
@@ -226,6 +260,7 @@ async function sendCancelRequest() {
  * Sends a Tachyon 'matchmaking/ready' request.
  */
 async function sendReadyRequest() {
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.MatchAccepted;
     try {
         const response = await window.tachyon.request("matchmaking/ready");
@@ -264,6 +299,7 @@ export async function initializeMatchmakingStore() {
 // selectedQueue is the user's pick, not server state, and downloadsRequired is derived from
 // installed content rather than the session - the next list response recomputes it.
 export function clearOnlineState() {
+    clearReadyTimers();
     matchmakingStore.status = MatchmakingStatus.Idle;
     matchmakingStore.playlists = [];
     matchmakingStore.isLoadingQueues = false;
diff --git a/src/renderer/views/play/matchmaking.vue b/src/renderer/views/play/matchmaking.vue
index a5480c78e..138ea2f33 100644
--- a/src/renderer/views/play/matchmaking.vue
+++ b/src/renderer/views/play/matchmaking.vue
@@ -39,6 +39,13 @@ SPDX-License-Identifier: MIT
                     <div class="info bl" v-if="matchmakingStore.selectedQueue === queue" @click.stop="onInfoClick">
                         <Icon :icon="informationIcon"></Icon>
                     </div>
+                    <div
+                        class="info br"
+                        v-if="getTeamSize(queue) < getPartySize()"
+                        v-tooltip.bottom="{ value: t('lobby.multiplayer.ranked.buttons.partyTooLargeTooltip') }"
+                    >
+                        <Icon :icon="stopAlertOutlineIcon"></Icon>
+                    </div>
                 </Button>
             </div>
             <div class="button-container">
@@ -53,6 +60,9 @@ SPDX-License-Identifier: MIT
                         >This string should never be visible.</DownloadContentButton
                     >
                 </div>
+                <button v-else-if="partyTooLarge" class="quick-play-button invalid" disabled>
+                    {{ t("lobby.multiplayer.ranked.buttons.partyTooLarge") }}
+                </button>
                 <button
                     v-else-if="matchmakingStore.status === MatchmakingStatus.Idle"
                     class="quick-play-button"
@@ -78,10 +88,10 @@ SPDX-License-Identifier: MIT
                     class="quick-play-button"
                     @click="matchmaking.sendReadyRequest"
                 >
-                    {{ t("lobby.multiplayer.ranked.buttons.matchFound") }}
+                    {{ t("lobby.multiplayer.ranked.buttons.matchFound", { seconds: matchmakingStore.readySecondsRemaining }) }}
                 </button>
                 <button v-else-if="matchmakingStore.status === MatchmakingStatus.MatchAccepted" class="quick-play-button" disabled>
-                    {{ t("lobby.multiplayer.ranked.buttons.accepted") }}
+                    {{ t("lobby.multiplayer.ranked.buttons.accepted", { players: matchmakingStore.playersReady ?? 0 }) }}
                 </button>
                 <button
                     class="cancel-button"
@@ -106,6 +116,7 @@ SPDX-License-Identifier: MIT
 </template>
 
 <script lang="ts" setup>
+import { getPartySize, usePartySizeMatchmaking } from "@renderer/composables/usePartySizeMatchmaking";
 import { matchmaking, MatchmakingStatus, matchmakingStore, getPlaylistName } from "@renderer/store/matchmaking.store";
 import Button from "primevue/button";
 import { useTypedI18n } from "@renderer/i18n";
@@ -113,6 +124,7 @@ import { computed, onActivated, ref } from "vue";
 import DownloadContentButton from "@renderer/components/controls/DownloadContentButton.vue";
 import QueueDownloadsModal from "@renderer/components/misc/QueueDownloadsModal.vue";
 import informationIcon from "@iconify-icons/mdi/information";
+import stopAlertOutlineIcon from "@iconify-icons/mdi/stop-alert-outline";
 import { Icon } from "@iconify/vue";
 
 const { t } = useTypedI18n();
@@ -137,8 +149,8 @@ const downloadsAreRequiredForSelected = computed(() => {
 
 const downloading = ref(false);
 
-// Switching the active queue during a download cannot be allowed because it messes with state.
 function queueSelected(queue: string) {
+    // Switching the active queue during a download cannot be allowed because it messes with state.
     if (downloading.value) {
         return;
     } else matchmakingStore.selectedQueue = queue;
@@ -160,6 +172,12 @@ onActivated(() => {
 function onInfoClick() {
     if (!downloading.value) isQueueDownloadsModalOpen.value = true;
 }
+const { partyTooLarge } = usePartySizeMatchmaking();
+
+function getTeamSize(queue: string) {
+    const playlist = matchmakingStore.playlists.find((p) => p.id === queue);
+    return playlist ? playlist.teamSize : 0;
+}
 </script>
 
 <style lang="scss" scoped>
@@ -287,6 +305,10 @@ function onInfoClick() {
         box-shadow 0.3s ease;
 }
 
+.quick-play-button.invalid {
+    background: linear-gradient(0deg, #1e2c23, #304135);
+}
+
 .searching {
     animation: pulse 3s infinite ease-in-out;
 }
diff --git a/src/renderer/views/profile/party.vue b/src/renderer/views/profile/party.vue
index 3109b95bb..6b1e1c07d 100644
--- a/src/renderer/views/profile/party.vue
+++ b/src/renderer/views/profile/party.vue
@@ -65,6 +65,13 @@ SPDX-License-Identifier: MIT
                                                 >
                                                     <Icon :icon="informationIcon"></Icon>
                                                 </div>
+                                                <div
+                                                    class="info br"
+                                                    v-if="getTeamSize(queue) < getPartySize()"
+                                                    v-tooltip.bottom="{ value: t('lobby.views.party.partyTooLargeTooltip') }"
+                                                >
+                                                    <Icon :icon="stopAlertOutlineIcon"></Icon>
+                                                </div>
                                             </Button>
                                         </div>
                                     </div>
@@ -86,6 +93,9 @@ SPDX-License-Identifier: MIT
                                                 >This string should never be visible.</DownloadContentButton
                                             >
                                         </div>
+                                        <button v-else-if="partyTooLarge" class="quick-play-button invalid" disabled>
+                                            {{ t("lobby.views.party.partyTooLarge") }}
+                                        </button>
                                         <button
                                             v-else-if="matchmakingStore.status === MatchmakingStatus.Idle"
                                             class="quick-play-button"
@@ -115,14 +125,22 @@ SPDX-License-Identifier: MIT
                                             class="quick-play-button"
                                             @click="matchmaking.sendReadyRequest"
                                         >
-                                            {{ t("lobby.multiplayer.ranked.buttons.matchFound") }}
+                                            {{
+                                                t("lobby.multiplayer.ranked.buttons.matchFound", {
+                                                    seconds: matchmakingStore.readySecondsRemaining,
+                                                })
+                                            }}
                                         </button>
                                         <button
                                             v-else-if="matchmakingStore.status === MatchmakingStatus.MatchAccepted"
                                             class="quick-play-button"
                                             disabled
                                         >
-                                            {{ t("lobby.multiplayer.ranked.buttons.accepted") }}
+                                            {{
+                                                t("lobby.multiplayer.ranked.buttons.accepted", {
+                                                    players: matchmakingStore.playersReady ?? 0,
+                                                })
+                                            }}
                                         </button>
                                         <button
                                             class="cancel-button"
@@ -207,8 +225,10 @@ import { matchmakingStore, matchmaking, MatchmakingStatus, getPlaylistName } fro
 import DownloadContentButton from "@renderer/components/controls/DownloadContentButton.vue";
 import QueueDownloadsModal from "@renderer/components/misc/QueueDownloadsModal.vue";
 import informationIcon from "@iconify-icons/mdi/information";
+import stopAlertOutlineIcon from "@iconify-icons/mdi/stop-alert-outline";
 import { Icon } from "@iconify/vue";
 import { chatStore } from "@renderer/store/chat.store";
+import { getPartySize, usePartySizeMatchmaking } from "@renderer/composables/usePartySizeMatchmaking";
 
 const { t } = useTypedI18n();
 
@@ -290,8 +310,8 @@ const downloadsAreRequiredForSelected = computed(() => {
 
 const downloading = ref(false);
 
-// Switching the active queue during a download cannot be allowed because it messes with state.
 function queueSelected(queue: string) {
+    // Switching the active queue during a download cannot be allowed because it messes with state.
     if (downloading.value) {
         return;
     } else matchmakingStore.selectedQueue = queue;
@@ -348,6 +368,13 @@ function getActivePartyInvites() {
     if (!partyStore.activeParty || !partyStore.parties.get(partyStore.activeParty)) return [];
     return partyStore.parties.get(partyStore.activeParty)!.invited;
 }
+
+const { partyTooLarge } = usePartySizeMatchmaking();
+
+function getTeamSize(queue: string) {
+    const playlist = matchmakingStore.playlists.find((p) => p.id === queue);
+    return playlist ? playlist.teamSize : 0;
+}
 </script>
 
 <style lang="scss" scoped>
@@ -429,6 +456,13 @@ function getActivePartyInvites() {
         bottom: 0px;
         left: 0px;
     }
+    &.br {
+        bottom: 0px;
+        right: 0px;
+        flex-wrap: wrap-reverse;
+        justify-content: flex-end;
+        max-width: 55%;
+    }
 }
 .info:hover {
     opacity: 1;
@@ -465,6 +499,10 @@ function getActivePartyInvites() {
         box-shadow 0.3s ease;
 }
 
+.quick-play-button.invalid {
+    background: linear-gradient(0deg, #1e2c23, #304135);
+}
+
 .searching {
     animation: pulse 3s infinite ease-in-out;
 }
diff --git a/tests/unit/renderer/use-party-size-matchmaking.spec.ts b/tests/unit/renderer/use-party-size-matchmaking.spec.ts
new file mode 100644
index 000000000..d5ab44150
--- /dev/null
+++ b/tests/unit/renderer/use-party-size-matchmaking.spec.ts
@@ -0,0 +1,191 @@
+// SPDX-FileCopyrightText: 2026 The BAR Lobby Authors
+//
+// SPDX-License-Identifier: MIT
+
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { effectScope, nextTick, type EffectScope, type Ref } from "vue";
+import { partyStore } from "@renderer/store/party.store";
+import { matchmakingStore } from "@renderer/store/matchmaking.store";
+import { usePartySizeMatchmaking, getPartySize } from "@renderer/composables/usePartySizeMatchmaking";
+
+function makePlaylist(id: string, teamSize: number) {
+    return {
+        id,
+        name: id,
+        version: "1",
+        numOfTeams: 2,
+        teamSize,
+        ranked: false,
+        engines: [],
+        games: [],
+        maps: [],
+    } as (typeof matchmakingStore.playlists)[number];
+}
+
+function makeMembers(count: number) {
+    return Array.from({ length: count }, (_, i) => ({ userId: `${i}`, joinedAt: 0 }));
+}
+
+function makeInvited(count: number) {
+    return Array.from({ length: count }, (_, i) => ({ userId: `invitee-${i}`, invitedAt: 0 }));
+}
+
+function setupParty(memberCount: number, teamSize: number) {
+    partyStore.activeParty = "party-1";
+    partyStore.parties.set("party-1", { id: "party-1", members: makeMembers(memberCount), invited: [], maxMembers: 10, seen: true });
+    matchmakingStore.selectedQueue = "1v1";
+    matchmakingStore.playlists = [makePlaylist("1v1", teamSize)];
+}
+
+let scope: EffectScope;
+let partyTooLarge: Ref<boolean>;
+
+beforeEach(() => {
+    partyStore.activeParty = undefined;
+    partyStore.parties.clear();
+    matchmakingStore.playlists = [];
+    matchmakingStore.selectedQueue = "1v1";
+
+    scope = effectScope();
+    scope.run(() => {
+        partyTooLarge = usePartySizeMatchmaking().partyTooLarge;
+    });
+});
+
+afterEach(() => {
+    scope.stop();
+});
+
+describe("usePartySizeMatchmaking", () => {
+    describe("reactivity", () => {
+        it("re-evaluates when activeParty changes", async () => {
+            setupParty(2, 3);
+            partyStore.parties.set("party-2", { id: "party-2", members: makeMembers(4), invited: [], maxMembers: 10, seen: true });
+            await nextTick();
+            expect(partyTooLarge.value).toBe(false);
+
+            partyStore.activeParty = "party-2";
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(true);
+        });
+
+        it("re-evaluates when the selected queue changes", async () => {
+            setupParty(2, 3);
+            matchmakingStore.playlists.push(makePlaylist("2v2", 1));
+            await nextTick();
+            expect(partyTooLarge.value).toBe(false);
+
+            matchmakingStore.selectedQueue = "2v2";
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(true);
+        });
+
+        it("re-evaluates when playlists changes", async () => {
+            setupParty(2, 3);
+            await nextTick();
+            expect(partyTooLarge.value).toBe(false);
+
+            matchmakingStore.playlists = [makePlaylist("1v1", 1)];
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(true);
+        });
+
+        it("re-evaluates when the party's members change", async () => {
+            setupParty(2, 3);
+            await nextTick();
+            expect(partyTooLarge.value).toBe(false);
+
+            partyStore.parties.get("party-1")!.members = makeMembers(4);
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(true);
+        });
+
+        it("re-evaluates when the party's invited list changes", async () => {
+            setupParty(2, 3);
+            await nextTick();
+            expect(partyTooLarge.value).toBe(false);
+
+            partyStore.parties.get("party-1")!.invited = makeInvited(1);
+            await nextTick();
+
+            // Invites don't factor into the size comparison, so the result is expected to stay the same.
+            expect(partyTooLarge.value).toBe(false);
+        });
+    });
+
+    describe("false-guard cases", () => {
+        it("is false when there is no active party", async () => {
+            matchmakingStore.playlists = [makePlaylist("1v1", 1)];
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(false);
+        });
+
+        it("is false when playlists is empty", async () => {
+            partyStore.activeParty = "party-1";
+            partyStore.parties.set("party-1", { id: "party-1", members: makeMembers(2), invited: [], maxMembers: 10, seen: true });
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(false);
+        });
+
+        it("is false when the active party isn't found in any party's members", async () => {
+            matchmakingStore.playlists = [makePlaylist("1v1", 1)];
+            partyStore.activeParty = "missing-party";
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(false);
+        });
+    });
+
+    describe("size comparison", () => {
+        it("is false when members are fewer than the team size", async () => {
+            setupParty(1, 2);
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(false);
+        });
+
+        it("is false when members equal the team size", async () => {
+            setupParty(2, 2);
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(false);
+        });
+
+        it("is true when members exceed the team size", async () => {
+            setupParty(3, 2);
+            await nextTick();
+
+            expect(partyTooLarge.value).toBe(true);
+        });
+    });
+});
+
+describe("getPartySize", () => {
+    beforeEach(() => {
+        partyStore.activeParty = undefined;
+        partyStore.parties.clear();
+    });
+
+    it("returns 0 when there is no active party", () => {
+        expect(getPartySize()).toBe(0);
+    });
+
+    it("returns 0 when the active party isn't in the parties map", () => {
+        partyStore.activeParty = "missing-party";
+
+        expect(getPartySize()).toBe(0);
+    });
+
+    it("returns the member count of the active party", () => {
+        partyStore.activeParty = "party-1";
+        partyStore.parties.set("party-1", { id: "party-1", members: makeMembers(3), invited: [], maxMembers: 10, seen: true });
+
+        expect(getPartySize()).toBe(3);
+    });
+});