diff --git a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.test.ts b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.test.ts
index d1723799..8d026db3 100644
--- a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.test.ts
+++ b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.test.ts
@@ -12,6 +12,22 @@ const KEYS = ['p1:s1', 'p2:s1', 'p1:new', 'p2:new', 'screen:s1'];
 beforeEach(() => KEYS.forEach((k) => writeQueue(k, [])));
 
 describe('queueKey', () => {
+  // The bug the first version shipped: `ChatDetailPanel` mounts with `sessionId={undefined}`, so every
+  // conversation fell back to one shared key. Queue in one chat, open another, and the queue was restored
+  // there — and the mount-drain SENT it. Somebody's message delivered to a chat they did not write it in.
+  test('an unidentifiable mount gets NO key, so it cannot share one', () => {
+    expect(queueKey(undefined, undefined)).toBeNull();
+  });
+
+  test('a null key never persists anything', () => {
+    writeQueue(null, [prompt('must not survive')]);
+    expect(readQueue(null)).toEqual([]);
+  });
+
+  test('two resumed conversations in the same surface do not collide', () => {
+    expect(queueKey('chat:AAA', undefined)).not.toBe(queueKey('chat:BBB', undefined));
+  });
+
   test('a panel and a session together identify a queue', () => {
     expect(queueKey('p1', 's1')).toBe('p1:s1');
   });
diff --git a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.ts b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.ts
index 32ea6bee..b0abead6 100644
--- a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.ts
+++ b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/queue-store.ts
@@ -28,14 +28,31 @@ import type { QueuedPrompt } from './useEmbeddableChat';
  */
 const queues = new Map<string, QueuedPrompt[]>();
 
-/** A queue belongs to one panel's view of one conversation. */
-export const queueKey = (panelId: string | undefined, sessionId: string | undefined): string =>
-  `${panelId ?? 'screen'}:${sessionId ?? 'new'}`;
+/**
+ * A queue belongs to one panel's view of one conversation — or to nothing at all.
+ *
+ * **Null when neither identifies it, and that is the important case.** The first version fell back to
+ * `screen:new`, so every conversation opened without a session id shared one queue: `ChatDetailPanel`
+ * mounts with `sessionId={undefined}`, so queueing in one chat and opening another restored the queue
+ * there — and the mount-drain then SENT it into the wrong conversation. Somebody's message, delivered to
+ * a chat they did not write it in.
+ *
+ * A shared key is worse than no key. With null the queue simply stays local to the mount and is lost on a
+ * switch, which is where this started — bad, but not wrong.
+ *
+ * A panel alone is enough: one panel holds one new chat, so `panel-3:new` is unambiguous. A session alone
+ * is enough: that IS the conversation. Neither is not.
+ */
+export function queueKey(panelId: string | undefined, sessionId: string | undefined): string | null {
+  if (!panelId && !sessionId) return null;
+  return `${panelId ?? 'screen'}:${sessionId ?? 'new'}`;
+}
 
-export const readQueue = (key: string): QueuedPrompt[] => queues.get(key) ?? [];
+export const readQueue = (key: string | null): QueuedPrompt[] => (key ? (queues.get(key) ?? []) : []);
 
 /** Empty is the same as absent — an entry per conversation ever opened would grow without bound. */
-export function writeQueue(key: string, items: QueuedPrompt[]): void {
+export function writeQueue(key: string | null, items: QueuedPrompt[]): void {
+  if (!key) return;
   if (items.length === 0) queues.delete(key);
   else queues.set(key, items);
 }
diff --git a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/useEmbeddableChat.ts b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/useEmbeddableChat.ts
index 13a936fb..f4d68e47 100644
--- a/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/useEmbeddableChat.ts
+++ b/src/workspaces/officerdev/src/apps/Chat/EmbeddableChat/useEmbeddableChat.ts
@@ -102,7 +102,10 @@ export function useEmbeddableChat(params: UseEmbeddableChatParams, onMessageComp
   useEffect(() => {
     if (restoredRef.current) return;
     restoredRef.current = true;
-    if (!isGenerating && queuedRef.current.length > 0) void drainQueueRef.current();
+    // `storeKey` being null means this mount cannot identify its conversation, so nothing was restored and
+    // nothing may be sent — see `queue-store`. Sending here on a shared key is what delivered a message
+    // into the chat somebody had switched TO.
+    if (storeKey && !isGenerating && queuedRef.current.length > 0) void drainQueueRef.current();
   }, []);
 
   // Detect when agent finishes a message (isGenerating: true → false)
diff --git a/src/workspaces/officerdev/src/apps/ChatHistory/ChatDetailPanel.tsx b/src/workspaces/officerdev/src/apps/ChatHistory/ChatDetailPanel.tsx
index 67978aa4..dc0af42e 100644
--- a/src/workspaces/officerdev/src/apps/ChatHistory/ChatDetailPanel.tsx
+++ b/src/workspaces/officerdev/src/apps/ChatHistory/ChatDetailPanel.tsx
@@ -200,6 +200,10 @@ function NewChat(props: NewChatProps) {
       <EmbeddableChat
         chat={chat}
         sessionId={undefined}
+        // Which CONVERSATION this is, from the URL — the queue is keyed on it so switching chats cannot
+        // carry queued messages into the one you switched to. `sessionId` above is a different question
+        // (it seeds the socket handshake and must stay undefined here, since `chat` is already resumed).
+        panelId={resumeSessionId ? `chat:${resumeSessionId}` : undefined}
         // The session's own model wins. `locationState.model` is declared on ChatLocationState and
         // written by nothing, so it was the only source and always undefined on resume; it stays as a
         // fallback for a future caller that navigates with one deliberately.