diff --git a/packages/core/issues/queries.ts b/packages/core/issues/queries.ts
index beceaa5f6..221419e44 100644
--- a/packages/core/issues/queries.ts
+++ b/packages/core/issues/queries.ts
@@ -64,17 +64,29 @@ export const issueKeys = {
     [...issueKeys.childrenByParentsAll(wsId), parentIds] as const,
   childProgress: (wsId: string) =>
     [...issueKeys.all(wsId), "child-progress"] as const,
+  /** Prefix-match keys for invalidating the per-issue caches below across
+   *  all issues. These keys carry no wsId, so `issueKeys.all(wsId)` does NOT
+   *  cover them — WS reconnect recovery must invalidate these `*All`
+   *  prefixes explicitly, or missed events leave them stale forever under
+   *  the staleTime: Infinity default (#3953). */
+  timelineAll: () => ["issues", "timeline"] as const,
   /** Full-issue timeline (single TanStack Query, no cursor). */
   timeline: (issueId: string) =>
-    ["issues", "timeline", issueId] as const,
-  reactions: (issueId: string) => ["issues", "reactions", issueId] as const,
+    [...issueKeys.timelineAll(), issueId] as const,
+  reactionsAll: () => ["issues", "reactions"] as const,
+  reactions: (issueId: string) =>
+    [...issueKeys.reactionsAll(), issueId] as const,
+  subscribersAll: () => ["issues", "subscribers"] as const,
   subscribers: (issueId: string) =>
-    ["issues", "subscribers", issueId] as const,
-  usage: (issueId: string) => ["issues", "usage", issueId] as const,
+    [...issueKeys.subscribersAll(), issueId] as const,
+  usageAll: () => ["issues", "usage"] as const,
+  usage: (issueId: string) => [...issueKeys.usageAll(), issueId] as const,
+  attachmentsAll: () => ["issues", "attachments"] as const,
   /** Issue-level attachments — used by the description editor so its
    *  inline file-card / image NodeViews can re-sign download URLs at
    *  click time. */
-  attachments: (issueId: string) => ["issues", "attachments", issueId] as const,
+  attachments: (issueId: string) =>
+    [...issueKeys.attachmentsAll(), issueId] as const,
   /** Per-issue task list (issue-detail Execution log section). */
   tasks: (issueId: string) => ["issues", "tasks", issueId] as const,
   /** Prefix-match key for invalidating tasks across all issues — used by
diff --git a/packages/core/realtime/use-realtime-sync-ws-instance.test.tsx b/packages/core/realtime/use-realtime-sync-ws-instance.test.tsx
index 9a349d6b1..0e70f7c58 100644
--- a/packages/core/realtime/use-realtime-sync-ws-instance.test.tsx
+++ b/packages/core/realtime/use-realtime-sync-ws-instance.test.tsx
@@ -102,8 +102,9 @@ describe("useRealtimeSync — ws instance change", () => {
     rerender({ ws: ws2 });
 
     // Should have called invalidateQueries for all workspace-scoped keys
-    // (15 workspace-scoped + 1 workspaceKeys.list() = 16 calls)
-    expect(invalidateSpy).toHaveBeenCalledTimes(16);
+    // (15 workspace-scoped + 6 per-issue prefixes + 1 workspaceKeys.list()
+    // = 22 calls)
+    expect(invalidateSpy).toHaveBeenCalledTimes(22);
   });
 
   it("does not re-invalidate when rerendered with the same ws instance", () => {
@@ -138,4 +139,29 @@ describe("useRealtimeSync — ws instance change", () => {
     expect(calls).toContainEqual(["labels", "ws-1"]);
     expect(calls).toContainEqual(["workspaces", "ws-1", "invitations"]);
   });
+
+  it("invalidates per-issue caches (no wsId in key) on ws instance change", () => {
+    // These keys are not under the ["issues", wsId] prefix, so they need
+    // their own invalidation on recovery — otherwise events missed while
+    // disconnected leave them stale forever (staleTime: Infinity, #3953).
+    const ws1 = createMockWs();
+    const { rerender } = renderHook(
+      ({ ws }) => useRealtimeSync(ws, stores),
+      { initialProps: { ws: ws1 as WSClient | null }, wrapper: createWrapper(qc) },
+    );
+
+    invalidateSpy.mockClear();
+    rerender({ ws: null });
+
+    const ws2 = createMockWs();
+    rerender({ ws: ws2 });
+
+    const calls = invalidateSpy.mock.calls.map((call: [{ queryKey?: unknown }, ...unknown[]]) => call[0].queryKey);
+    expect(calls).toContainEqual(["issues", "timeline"]);
+    expect(calls).toContainEqual(["issues", "reactions"]);
+    expect(calls).toContainEqual(["issues", "subscribers"]);
+    expect(calls).toContainEqual(["issues", "usage"]);
+    expect(calls).toContainEqual(["issues", "attachments"]);
+    expect(calls).toContainEqual(["issues", "tasks"]);
+  });
 });
diff --git a/packages/core/realtime/use-realtime-sync.ts b/packages/core/realtime/use-realtime-sync.ts
index b619fdd3b..e63a42d9d 100644
--- a/packages/core/realtime/use-realtime-sync.ts
+++ b/packages/core/realtime/use-realtime-sync.ts
@@ -313,6 +313,19 @@ function invalidateWorkspaceScopedQueries(qc: QueryClient): void {
     qc.invalidateQueries({ queryKey: chatKeys.all(wsId) });
     qc.invalidateQueries({ queryKey: labelKeys.all(wsId) });
   }
+  // Per-issue caches are keyed without wsId, so the issueKeys.all(wsId)
+  // prefix above does not reach them. They rely entirely on WS events for
+  // freshness (staleTime: Infinity), so events missed while disconnected
+  // left them stale until a full reload — the inbox showed an agent's new
+  // comment while the issue timeline didn't (#3953). Inactive caches only
+  // get marked stale here and refetch on next mount; the one mounted issue
+  // refetches immediately, same as its own useWSReconnect already does.
+  qc.invalidateQueries({ queryKey: issueKeys.timelineAll() });
+  qc.invalidateQueries({ queryKey: issueKeys.reactionsAll() });
+  qc.invalidateQueries({ queryKey: issueKeys.subscribersAll() });
+  qc.invalidateQueries({ queryKey: issueKeys.usageAll() });
+  qc.invalidateQueries({ queryKey: issueKeys.attachmentsAll() });
+  qc.invalidateQueries({ queryKey: issueKeys.tasksAll() });
   qc.invalidateQueries({ queryKey: workspaceKeys.list() });
 }