diff --git a/static/js/chat.js b/static/js/chat.js
index 10f7e05..6e75dab 100644
--- a/static/js/chat.js
+++ b/static/js/chat.js
@@ -4037,8 +4037,11 @@ import createResearchSynapse from './researchSynapse.js';
     const clickedIndex = allMsgs.indexOf(msgElement);
     if (clickedIndex < 0) return;
 
+    // No early-out on a missing session: an output shown before any model was
+    // selected (issue #1428) has no session/persisted rows, but its "x" must
+    // still remove it. We only need the session id for the server-side delete
+    // below; without one we fall back to removing the DOM.
     const sessionId = sessionModule.getCurrentSessionId();
-    if (!sessionId) return;
 
     const clickedIsUser = msgElement.classList.contains('msg-user');
 
@@ -4114,8 +4117,10 @@ import createResearchSynapse from './researchSynapse.js';
       }
     }
 
-    if (!msgIds.length) {
-      // Fallback: just remove DOM elements if no DB IDs available
+    if (!msgIds.length || !sessionId) {
+      // No persisted rows to delete (no DB IDs, or no session at all — e.g. an
+      // error output shown before a model was selected, #1428). Just remove the
+      // DOM so the "x" works regardless.
       domToRemove.forEach(el => el.remove());
       if (uiModule) uiModule.showToast('Message deleted');
       return;
diff --git a/tests/test_delete_message_no_session.py b/tests/test_delete_message_no_session.py
new file mode 100644
index 0000000..1ce1cf1
--- /dev/null
+++ b/tests/test_delete_message_no_session.py
@@ -0,0 +1,34 @@
+"""Regression guard for issue #1428 — the "x" on a chat output did nothing when
+no model/API was selected.
+
+deleteMessage() bailed at `if (!sessionId) return;`. An output shown before a
+model is picked has no session and no persisted rows, so the early-out meant the
+"x" never even removed the bubble from the DOM. The delete now falls through to
+DOM removal when there's no session / no DB ids.
+
+chat.js pulls in browser globals so it can't run under node; guard at the source.
+"""
+import re
+from pathlib import Path
+
+SRC = Path(__file__).resolve().parent.parent / "static/js/chat.js"
+
+
+def _delete_message_body() -> str:
+    text = SRC.read_text(encoding="utf-8")
+    start = text.index("export async function deleteMessage(")
+    rest = text[start:]
+    m = re.search(r"\n  export (async )?function ", rest[1:])
+    return rest[: m.start() + 1] if m else rest
+
+
+def test_delete_does_not_early_return_on_missing_session():
+    body = _delete_message_body()
+    # The bug was an unconditional early-out when no session existed.
+    assert not re.search(r"if\s*\(\s*!sessionId\s*\)\s*return\s*;", body), (
+        "deleteMessage must not early-return on a missing session (#1428)"
+    )
+    # The DOM-removal fallback must also fire when there's no session.
+    assert re.search(r"!msgIds\.length\s*\|\|\s*!sessionId", body), (
+        "DOM-removal fallback should cover the no-session case"
+    )