diff --git a/web/resources/static/js/connection-event.js b/web/resources/static/js/connection-event.js
new file mode 100644
index 0000000..d622cae
--- /dev/null
+++ b/web/resources/static/js/connection-event.js
@@ -0,0 +1,48 @@
+// atmo.quest — toggle whether a connection is tagged with the event you're
+// currently checked into. POSTs {associate: bool} to
+// /connections/{did}/event. The server re-derives which event; we only send
+// the boolean. On failure we revert the checkbox so the UI matches the PDS.
+(function () {
+  "use strict";
+
+  var toggle = document.querySelector(".pv-event-toggle");
+  if (!toggle) return;
+
+  var targetDID = toggle.getAttribute("data-target-did");
+  var checkbox = document.getElementById("pv-event-associate");
+  var status = document.getElementById("pv-event-status");
+  if (!targetDID || !checkbox) return;
+
+  function showStatus(msg) {
+    if (!status) return;
+    status.textContent = msg;
+    clearTimeout(status._timer);
+    status._timer = setTimeout(function () { status.textContent = ""; }, 2000);
+  }
+
+  checkbox.addEventListener("change", function () {
+    var desired = checkbox.checked;
+    checkbox.disabled = true;
+    fetch("/connections/" + encodeURI(targetDID) + "/event", {
+      method: "POST",
+      credentials: "same-origin",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({ associate: desired })
+    })
+      .then(function (resp) {
+        if (resp.ok) {
+          showStatus("✓ saved");
+        } else {
+          checkbox.checked = !desired; // revert
+          showStatus("save failed");
+        }
+      })
+      .catch(function () {
+        checkbox.checked = !desired; // revert
+        showStatus("save failed");
+      })
+      .finally(function () {
+        checkbox.disabled = false;
+      });
+  });
+})();