kits: launch carries the kit's current prompt, and Open goes through launch

gateway/app.py

@@ -15098,6 +15098,15 @@ async def launch_kit(kit_id: str, request: Request, body_in: KitLaunchBody | Non
             # current package on the next press of Launch. Same version: nothing is rewritten.
             existing = await _kit_plugin_ensure(org, hid0, existing, kit_plugin, tuple(
                 str(d["name"]) for d in (decl, media_decl) if d and d.get("name"))) or existing
+        # The prompt too: it is the kit's, like the package, and a kit whose prompt changed
+        # (the sheet one gained its output contract on 2026-09-22) must reach the Harness
+        # people already run, or the fix ships to new launches only.
+        want_prompt = str((kit.get("harness") or {}).get("system_prompt") or "")
+        if want_prompt and str(existing.get("system_prompt") or "") != want_prompt:
+            await _vg_upsert("Harness", hid0, {"system_prompt": want_prompt,
+                                               "updated_at": str(int(time.time() * 1000))})
+            existing = await _vertex_get(hid0) or {**existing, "system_prompt": want_prompt}
+            print(f"[kits] {kit_id}: prompt refreshed on {hid0}", flush=True)
         return {"kit": kit_id, "harnessId": hid0,
                 "route": (kit.get("app") or {}).get("route") or "", "created": False,
                 "harness": _harness_out(existing)}

gateway/tests/test_kits_workspace.py

@@ -116,3 +116,21 @@ async def _mcp_write(hid, servers):
     assert len(conns) == 1 and conns[0]["harness"] == hid and conns[0]["secret_key"] == key
     assert conns[0]["workspace"] == "org.a__ws1" and conns[0]["database"] == "shop" and "u:p@" not in json.dumps(conns[0])
     assert asyncio.run(gw._connections_of("org.a", hid))[0]["database"] == "shop"
+
+
+def test_a_relaunch_carries_the_kits_current_prompt(world, monkeypatch):
+    """The prompt is the kit's, like its package: a kit whose prompt changed reaches the Harness a
+    workspace already runs on the next launch, and an unchanged prompt rewrites nothing."""
+    store, who = world
+    kit = json.loads(json.dumps(KIT)); kit["harness"]["system_prompt"] = "Build decks."
+    monkeypatch.setattr(gw, "_kits", lambda: {"slides": kit})
+    hid = asyncio.run(gw.launch_kit("slides", _Req(), None))["harnessId"]
+    assert store[hid]["system_prompt"] == "Build decks."
+    stamp = store[hid]["updated_at"]
+    again = asyncio.run(gw.launch_kit("slides", _Req(), None))
+    assert not again["created"] and store[hid]["updated_at"] == stamp       # same prompt: untouched
+    kit["harness"]["system_prompt"] = "Build decks. The person sees only ./deck.json."
+    third = asyncio.run(gw.launch_kit("slides", _Req(), None))
+    assert not third["created"] and third["harnessId"] == hid
+    assert store[hid]["system_prompt"] == "Build decks. The person sees only ./deck.json."
+    assert third["harness"]["systemPrompt"] == "Build decks. The person sees only ./deck.json."

ui/src/app/(app)/kits/page.tsx

@@ -83,17 +83,17 @@ export default function KitsPage() {
       .catch(() => {});
   }, []);
 
-  /** A kit app runs outside this Next app, so it gets its own tab. */
-  /** The kit app is this origin's own page, so the tab keeps its handle: `noopener` makes
-   *  window.open return null, which is what left the tab launch opened blank forever. */
-  function openApp(route: string) {
-    window.open(route, '_blank');
-  }
-
+  /** Launch, and open the kit app in its own tab (it runs outside this Next app). Opening a
+   *  kit that is already running goes through the same call: launch is idempotent, and it is
+   *  where a running kit picks up what its kit definition has changed since (its package, its
+   *  prompt, the tools it needs), so a kit fixed after someone launched it is fixed for them the
+   *  next time they open it, not only for whoever launches it fresh.
+   *
+   *  The tab is opened NOW, on the click, and navigated when the launch returns. Opening it after
+   *  the await is a popup the browser is entitled to block, because by then it is no longer a
+   *  user gesture. The kit app is this origin's own page, so the tab keeps its handle: `noopener`
+   *  makes window.open return null, which is what left the tab launch opened blank forever. */
   async function launch(kit: Kit, base?: string, model?: string, database?: DbDraft) {
-    // Open the tab NOW, on the click, and navigate it when the launch returns. Opening it after
-    // the await is a popup the browser is entitled to block, because by then it is no longer a
-    // user gesture.
     const tab = window.open('', '_blank');
     setBusy(kit.id); setErr('');
     try {
@@ -115,7 +115,7 @@ export default function KitsPage() {
       if (!r.ok) throw new Error((await r.json().catch(() => null))?.detail || `${r.status}`);
       const { route } = await r.json();
       const url = route || `/kits/${kit.id}`;
-      if (tab) tab.location.href = url; else openApp(url);
+      if (tab) tab.location.href = url; else window.location.assign(url);
       setPicking(null); setBusy('');
       reload();
     } catch (e) {
@@ -233,8 +233,8 @@ export default function KitsPage() {
                 )}
                 <span className="kit-actions-spacer" />
                   <button className="button primary" type="button" disabled={busy === k.id}
-                    onClick={() => (k.launched ? openApp(k.route || `/kits/${k.id}`) : setPicking(k))}>
-                    {busy === k.id ? 'Launching…' : k.launched ? 'Open' : 'Launch'}
+                    onClick={() => (k.launched ? void launch(k) : setPicking(k))}>
+                    {busy === k.id ? (k.launched ? 'Opening…' : 'Launching…') : k.launched ? 'Open' : 'Launch'}
                     <iconify-icon icon={k.launched ? 'tabler:external-link' : 'tabler:arrow-right'}></iconify-icon>
                   </button>
                 </footer>