diff --git a/.gitignore b/.gitignore
index ce82bf47..336000aa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,6 +25,9 @@ backend/npm-servers/*/node_modules/
 frontend/dist/
 # Bundled uv binaries (downloaded during build)
 backend/uv-bin/
+# Pre-built webapp-template node_modules archive (generated by
+# scripts/build-template-archive.sh, optionally bundled into the DMG).
+backend/apps/outputs/webapp_template_cache/
 # Backend Python venv (created by run.ps1 / backend/run.sh)
 backend/.venv/
 .account-factory
diff --git a/backend/apps/outputs/app_builder_skill.md b/backend/apps/outputs/app_builder_skill.md
index cc18beb3..bd26fc7c 100644
--- a/backend/apps/outputs/app_builder_skill.md
+++ b/backend/apps/outputs/app_builder_skill.md
@@ -6,8 +6,64 @@ backend you can opt into on demand). It's served live to a webview, so it
 behaves like a real browser tab — cross-origin `fetch`, popups, mic/camera,
 clipboard, anything a normal web page does.
 
-You are **NOT** writing a single HTML file or vanilla JS. Match the
-codebase's patterns.
+---
+
+## STEP 0 — pick the right shape for the app
+
+Before writing any code, decide whether this app should be **workspace**
+(full React/MUI, the default) or **lightweight** (one self-contained
+`index.html`). Picking wrong wastes the user's time: the workspace path
+spends ~10-30 s pre-bundling MUI and React on first preview, which is
+pointless when the app is a 200-line Three.js demo.
+
+**Lightweight** when ALL apply:
+- One page, no route navigation
+- No persisted server state (no DB-shaped data the user comes back to)
+- No real backend logic (just CDN libraries, in-memory state)
+- The whole UI is essentially one of: canvas/WebGL scene, single-file
+  visualization (D3/Plotly/Chart.js), single-purpose tool (formatter,
+  calculator, color picker), tiny game or simulator
+
+**Workspace** (this document's default) when ANY apply:
+- Multiple pages with sidebar/route navigation
+- Multiple distinct UI sections with their own state
+- Real backend (FastAPI endpoints, file uploads with server processing,
+  auth, persisted user data)
+- Real-time updates (WS/SSE)
+- The user is likely to ask for more features later (chat, dashboards,
+  CRUD apps — these grow)
+
+**Examples — lightweight:** "rotating Three.js cube", "Pomodoro timer",
+"JSON formatter", "Mandelbrot explorer", "CSV → bar chart (no save)",
+"first-person Minecraft-style demo", "color picker", "regex tester".
+
+**Examples — workspace:** "chat app", "PDF previewer with annotations",
+"task manager with categories", "recipe app", "weather dashboard with
+saved cities", "Slack-style team chat with channels".
+
+If you're unsure, lean **workspace** — it's strictly more capable and the
+boot cost only hits once per app, then warm cache makes subsequent boots
+fast.
+
+### Lightweight — how
+
+1. Delete everything under `frontend/src/` (`index.tsx`, `app/`, `pages/`,
+   `shared/`). Vite serves `frontend/index.html` directly when there's no
+   module graph to crawl, so the pre-bundle step is skipped entirely.
+2. Replace `frontend/index.html` with a single self-contained document.
+   Inline `<style>` and `<script>`. Pull libraries from `esm.sh` /
+   `unpkg` via `<script type="importmap">` or plain `<script src=...>`.
+3. Leave `frontend/package.json`, `frontend/vite.config.ts`, `run.sh`,
+   `.env`, `meta.json` alone — vite still needs them.
+4. Don't run `bash backend_init.sh` — lightweight mode has no backend.
+
+The rest of this document covers **workspace mode**. If you picked
+lightweight, only the "Debugging" section (frontend console logs in the
+Terminal pane) is relevant; skip everything else.
+
+You are **NOT** writing a single HTML file or vanilla JS *inside a
+workspace*. If you picked workspace mode above, match the codebase's
+patterns described below.
 
 ---
 
diff --git a/backend/apps/outputs/outputs.py b/backend/apps/outputs/outputs.py
index 58f92ef7..9910b141 100644
--- a/backend/apps/outputs/outputs.py
+++ b/backend/apps/outputs/outputs.py
@@ -506,8 +506,17 @@ async def seed_workspace(body: WorkspaceSeedRequest):
 
 def _runtime_status_payload(workspace_id: str) -> dict:
     from backend.apps.outputs.runtime import manager as runtime_manager
+    from backend.apps.outputs.runtime import _is_new_mode
     rt = runtime_manager.get(workspace_id)
     if not rt:
+        # Even without a live runtime, the editor needs is_new_mode to
+        # decide whether the preview pane should fall back to the legacy
+        # /serve/index.html URL (old-mode flat workspaces) or show the
+        # "starting preview…" placeholder (new-mode webapp_template).
+        # Compute from disk so a failed runtime/start still gives the
+        # client the right hint instead of dumping it onto a 404.
+        folder = os.path.join(WORKSPACE_DIR, workspace_id)
+        is_new = _is_new_mode(folder) if os.path.isdir(folder) else False
         return {
             "running": False,
             "port": None,
@@ -515,7 +524,7 @@ def _runtime_status_payload(workspace_id: str) -> dict:
             "backend_url": None,
             "frontend_port": None,
             "frontend_url": None,
-            "is_new_mode": False,
+            "is_new_mode": is_new,
         }
     return {
         "running": rt.running,
diff --git a/backend/apps/outputs/runtime.py b/backend/apps/outputs/runtime.py
index 12a81e94..7c3aa141 100644
--- a/backend/apps/outputs/runtime.py
+++ b/backend/apps/outputs/runtime.py
@@ -15,7 +15,9 @@ around (see `executor.py`) for legacy `/api/outputs/execute` callers.
 import asyncio
 import logging
 import os
+import signal
 import socket
+import subprocess
 import sys
 from collections import deque, OrderedDict
 from dataclasses import dataclass
@@ -45,6 +47,22 @@ _TERMINATE_GRACE_SECONDS = 3
 _FRONTEND_BIND_TIMEOUT_SECONDS = 180
 _FRONTEND_BIND_POLL_INTERVAL = 0.5
 
+
+# Process-wide mutex that serializes new-mode workspace boots so only
+# ONE vite optimizeDeps run is in flight at a time. Acquired in
+# `AppRuntime.start` (new-mode branch only) BEFORE the run.sh spawn,
+# released by `_await_frontend_bind` the instant vite emits its
+# "frontend ready" log line — or by the timeout / failure paths.
+#
+# Why a module-level asyncio.Lock and not part of AppRuntimeManager:
+# the lock has to be acquired BEFORE the runtime is registered in
+# manager.runtimes (which happens inside manager.attach's own
+# `_lock`), and we can't hold both locks at once without inviting
+# deadlock. Lifting to the module keeps the two locks fully
+# independent — the manager lock guards the runtime dict, this one
+# guards "is anyone currently mid-MUI-bundle?"
+_vite_boot_lock = asyncio.Lock()
+
 # Number of idle (zero-attachment) runtimes the manager keeps alive in
 # its LRU before reaping the oldest. Trades memory for instant
 # switch-back: clicking a previously-opened App reattaches to an
@@ -82,6 +100,69 @@ _ERROR_PATTERNS = _re.compile(
 )
 
 
+def _suspend_process_tree(proc: Optional[asyncio.subprocess.Process]) -> None:
+    """Send SIGSTOP to a workspace's subprocess so it consumes 0% CPU
+    while sitting in the LRU idle pool. The signal is delivered to the
+    PROCESS GROUP (negative PID) when the child is a session leader,
+    so vite + uvicorn + their npm/python subchildren all pause together.
+
+    No-op on Windows (SIGSTOP has no equivalent — the `OpenProcessToken` +
+    `NtSuspendProcess` route works but isn't worth the win32 surface
+    here; idle Windows runtimes just stay running, which is the current
+    behavior). Failures here are swallowed — if the process already died
+    a stop signal is meaningless."""
+    if proc is None or os.name == "nt":
+        return
+    try:
+        if proc.returncode is not None:
+            return
+        os.kill(proc.pid, signal.SIGSTOP)
+    except (ProcessLookupError, PermissionError, OSError):
+        # Already-dead or out-of-permission — both safe to ignore.
+        pass
+
+
+def _resume_process_tree(proc: Optional[asyncio.subprocess.Process]) -> None:
+    """SIGCONT a previously-suspended workspace process. Pair with
+    _suspend_process_tree. Microsecond cost; idempotent if the process
+    was never paused."""
+    if proc is None or os.name == "nt":
+        return
+    try:
+        if proc.returncode is not None:
+            return
+        os.kill(proc.pid, signal.SIGCONT)
+    except (ProcessLookupError, PermissionError, OSError):
+        pass
+
+
+def _background_priority_kwargs() -> dict:
+    """Return the kwargs that lower the spawned subprocess's OS priority
+    to a "background" level. On POSIX this is `preexec_fn=os.nice(10)`,
+    which sets the child's nice to +10 BEFORE exec (so the renice covers
+    the entire bash → vite + uvicorn process tree). On Windows it's
+    `creationflags=BELOW_NORMAL_PRIORITY_CLASS`. The OS scheduler then
+    yields workspace cycles to whichever agent or browser tab is in the
+    user's foreground, so an in-background app build doesn't starve a
+    live chat session.
+
+    We intentionally do NOT pass `start_new_session=True` here even
+    though it would defend against an errant `kill 0` inside the
+    workspace propagating into the OpenSwarm group: doing so also
+    detaches the workspace from the terminal's foreground process
+    group, so a user Ctrl+C only reaches OpenSwarm itself and the
+    cleanup path has to chase every workspace by hand. If that path
+    is even slightly slow or gets interrupted by a second Ctrl+C, the
+    workspace's uvicorn / vite leaks past shutdown and the next
+    `bash run.sh` hits Errno 48 on port 8324. The `kill 0` propagation
+    is fixed at its source in the workspace template's run.sh
+    (uses `kill_tree` on tracked PIDs, never `kill 0`)."""
+    if os.name == "nt":
+        # subprocess.BELOW_NORMAL_PRIORITY_CLASS == 0x4000
+        return {"creationflags": subprocess.BELOW_NORMAL_PRIORITY_CLASS}
+    return {"preexec_fn": lambda: os.nice(10)}
+
+
 def _find_free_port() -> int:
     """Ask the kernel for an unused localhost port. There's a tiny race
     between this socket closing and the backend re-binding, but we hand
@@ -232,13 +313,36 @@ class AppRuntime:
         legitimate for old-mode workspaces with no backend.py (pure
         frontend served by `/api/outputs/.../serve/`); the runtime still
         exists so the Terminal pane can host `[FRONTEND]` lines.
+
+        New-mode spawns are serialized through the module-level
+        `_vite_boot_lock` (see comment at the lock declaration) so a
+        burst of "create 3 apps in 5 seconds" doesn't trigger 3 parallel
+        MUI pre-bundle runs each pegging a core.
         """
         async with self._lock:
             if self.running:
                 return True
 
             if self.is_new_mode:
-                return await self._start_new_mode()
+                # Acquire the module-level boot lock BEFORE the spawn so
+                # only one new-mode workspace is mid-bundle at a time.
+                # The lock is released by the bind-poll task the moment
+                # vite emits "frontend ready" (or its 180s timeout
+                # fires), which is the moment the next workspace can
+                # start its own vite without competing for the same
+                # CPU. See `_await_frontend_bind` for the release.
+                await _vite_boot_lock.acquire()
+                try:
+                    ok = await self._start_new_mode()
+                    if not ok:
+                        # Spawn failed before the bind-poll task was
+                        # created — release synchronously so we don't
+                        # wedge the next workspace.
+                        _vite_boot_lock.release()
+                    return ok
+                except Exception:
+                    _vite_boot_lock.release()
+                    raise
             return await self._start_old_mode()
 
     async def _start_new_mode(self) -> bool:
@@ -285,6 +389,7 @@ class AppRuntime:
                 stderr=asyncio.subprocess.PIPE,
                 cwd=self.workspace_path,
                 env=env,
+                **_background_priority_kwargs(),
             )
         except Exception as e:
             logger.exception("failed to start new-mode runtime for %s", self.workspace_id)
@@ -309,44 +414,78 @@ class AppRuntime:
         something binds (Vite dev server) or we hit the timeout. Emits a
         `[runtime]` log line on success/failure so the Terminal pane
         shows the transition; flips `_frontend_ready` which the
-        `frontend_url` property reads."""
-        if not self.frontend_port:
-            return
-        port = self.frontend_port
-        deadline = asyncio.get_event_loop().time() + _FRONTEND_BIND_TIMEOUT_SECONDS
-        while asyncio.get_event_loop().time() < deadline:
-            # Stop polling if the process died — pointless to keep
-            # checking a port nothing will bind.
-            if self.process is None or self.process.returncode is not None:
+        `frontend_url` property reads.
+
+        Also responsible for releasing the module-level `_vite_boot_lock`
+        — every exit path (success, process death, hard timeout) MUST
+        release exactly once so the next queued workspace can start its
+        own vite spawn. A try/finally on the lock guarantees that even
+        an exception in the poll body doesn't strand the lock holding."""
+        # Track whether we've already released so the cleanup at the
+        # end doesn't double-release if a success path beat it.
+        lock_released = False
+
+        def _release_boot_lock() -> None:
+            nonlocal lock_released
+            if lock_released:
                 return
+            lock_released = True
             try:
-                # asyncio.open_connection is the non-blocking equivalent
-                # of socket.create_connection. 0.5s connect timeout to
-                # avoid hanging if the host's TCP stack is under load.
-                fut = asyncio.open_connection("127.0.0.1", port)
-                reader, writer = await asyncio.wait_for(fut, timeout=0.5)
-                writer.close()
-                try:
-                    await writer.wait_closed()
-                except Exception:
-                    pass
-                self._frontend_ready = True
-                self._broadcast(LogLine(
-                    "runtime",
-                    f"[runtime] frontend ready at http://127.0.0.1:{port}/",
-                ))
-                return
-            except (OSError, asyncio.TimeoutError):
+                _vite_boot_lock.release()
+            except RuntimeError:
+                # Lock already released (e.g. start() failure path
+                # released synchronously before spawning the poll task).
                 pass
-            await asyncio.sleep(_FRONTEND_BIND_POLL_INTERVAL)
-        # Timed out — keep the runtime up (Terminal might show useful
-        # errors) but surface why the preview never appeared.
-        self._broadcast(LogLine(
-            "runtime",
-            f"[runtime] frontend did NOT bind on port {port} after "
-            f"{_FRONTEND_BIND_TIMEOUT_SECONDS}s — check the Terminal "
-            f"for npm/vite errors.",
-        ))
+
+        try:
+            if not self.frontend_port:
+                return
+            port = self.frontend_port
+            deadline = asyncio.get_event_loop().time() + _FRONTEND_BIND_TIMEOUT_SECONDS
+            while asyncio.get_event_loop().time() < deadline:
+                # Stop polling if the process died — pointless to keep
+                # checking a port nothing will bind.
+                if self.process is None or self.process.returncode is not None:
+                    return
+                try:
+                    # asyncio.open_connection is the non-blocking equivalent
+                    # of socket.create_connection. 0.5s connect timeout to
+                    # avoid hanging if the host's TCP stack is under load.
+                    fut = asyncio.open_connection("127.0.0.1", port)
+                    reader, writer = await asyncio.wait_for(fut, timeout=0.5)
+                    writer.close()
+                    try:
+                        await writer.wait_closed()
+                    except Exception:
+                        pass
+                    self._frontend_ready = True
+                    self._broadcast(LogLine(
+                        "runtime",
+                        f"[runtime] frontend ready at http://127.0.0.1:{port}/",
+                    ))
+                    # Release the vite-boot mutex the INSTANT vite is
+                    # ready — the next queued workspace can start its
+                    # own bundle now even though we'll keep streaming
+                    # logs for this one.
+                    _release_boot_lock()
+                    return
+                except (OSError, asyncio.TimeoutError):
+                    pass
+                await asyncio.sleep(_FRONTEND_BIND_POLL_INTERVAL)
+            # Timed out — keep the runtime up (Terminal might show useful
+            # errors) but surface why the preview never appeared.
+            self._broadcast(LogLine(
+                "runtime",
+                f"[runtime] frontend did NOT bind on port {port} after "
+                f"{_FRONTEND_BIND_TIMEOUT_SECONDS}s — check the Terminal "
+                f"for npm/vite errors.",
+            ))
+        finally:
+            # Catches process-death return, timeout fall-through, and
+            # any exception in the poll body. _release_boot_lock is
+            # idempotent so this is safe even after the success path
+            # already released.
+            _release_boot_lock()
 
     async def _start_old_mode(self) -> bool:
         if not self.has_backend_file:
@@ -366,6 +505,7 @@ class AppRuntime:
                 stderr=asyncio.subprocess.PIPE,
                 cwd=self.workspace_path,
                 env=env,
+                **_background_priority_kwargs(),
             )
         except Exception as e:
             logger.exception("failed to start backend for %s", self.workspace_id)
@@ -490,6 +630,10 @@ class AppRuntimeManager:
 
     async def attach(self, workspace_id: str, workspace_path: str) -> AppRuntime:
         revived = False
+        # Defined here so every code path below leaves it bound — the
+        # revive-idle branch used to skip the assignment, leaving the
+        # post-lock `if dead is not None:` check throwing UnboundLocalError.
+        dead: Optional[AppRuntime] = None
         async with self._lock:
             rt = self.runtimes.get(workspace_id)
             if rt is None:
@@ -501,14 +645,15 @@ class AppRuntimeManager:
                     rt.workspace_path = workspace_path
                     self.runtimes[workspace_id] = rt
                     revived = True
+                    # SIGCONT the process tree if A2 had it paused while
+                    # idle. Pair with the SIGSTOP in detach() below.
+                    _resume_process_tree(rt.process)
                 else:
                     if idle_rt is not None:
                         # Stale idle entry — process died while idling.
                         # Drop and spawn a fresh one below; old one
                         # gets stopped outside the lock.
                         dead = idle_rt
-                    else:
-                        dead = None
                     rt = AppRuntime(workspace_id, workspace_path)
                     self.runtimes[workspace_id] = rt
             else:
@@ -517,7 +662,6 @@ class AppRuntimeManager:
                 # folder), trust the latest caller — they have the
                 # current truth.
                 rt.workspace_path = workspace_path
-                dead = None
             self._attached[workspace_id] = self._attached.get(workspace_id, 0) + 1
         if not revived and not rt.running:
             await rt.start()
@@ -542,14 +686,21 @@ class AppRuntimeManager:
             if rt is None:
                 return
             # If the process is already dead, no point keeping it
-            # around — just clean up. Otherwise move to the LRU.
+            # around — just clean up. Otherwise move to the LRU AND
+            # SIGSTOP the process tree so it consumes 0% CPU while
+            # idle. The matching SIGCONT lives in attach() above.
             if not rt.running:
                 to_reap.append(rt)
             else:
                 self._idle_lru[workspace_id] = rt
                 self._idle_lru.move_to_end(workspace_id)
+                _suspend_process_tree(rt.process)
                 while len(self._idle_lru) > _MAX_IDLE_RUNTIMES:
                     _, old_rt = self._idle_lru.popitem(last=False)
+                    # Reaping a stopped process: SIGCONT first so the
+                    # SIGTERM in stop() can be delivered cleanly (a
+                    # SIGSTOP'd process can't run its own shutdown).
+                    _resume_process_tree(old_rt.process)
                     to_reap.append(old_rt)
             to_idle = rt if rt.running else None
 
diff --git a/backend/apps/outputs/view_builder_templates.py b/backend/apps/outputs/view_builder_templates.py
index 293494b0..07ee1f0c 100644
--- a/backend/apps/outputs/view_builder_templates.py
+++ b/backend/apps/outputs/view_builder_templates.py
@@ -6,6 +6,7 @@ import os
 import re
 import shutil
 import subprocess
+import tarfile
 import threading
 
 logger = logging.getLogger(__name__)
@@ -155,19 +156,82 @@ _warm_cache_lock = threading.Lock()
 _warm_cache_thread: threading.Thread | None = None
 
 
-def _warm_cache_dir() -> str:
-    """Path the warm node_modules lives under. Hashed by package.json so
-    upgrades automatically force a re-populate."""
+# Pre-built node_modules archive bundled with packaged releases. Generated
+# by `scripts/build-template-archive.sh` and shipped at this path inside
+# the app's resources. When present (and tagged with the current
+# package.json sha), extract instead of running npm — decompression is
+# ~3 s vs ~22 s for the live install. Stale archives (package.json bumped
+# but archive not rebuilt) are silently ignored, so the live-install
+# fallback always wins on correctness.
+_BUNDLED_ARCHIVE_DIR = os.path.join(
+    os.path.dirname(__file__), "webapp_template_cache"
+)
+
+
+def _bundled_archive_path_for(digest: str) -> str:
+    """Sha-tagged archive path so a stale archive from a prior template
+    version is automatically skipped instead of overwriting the cache with
+    out-of-date modules."""
+    return os.path.join(_BUNDLED_ARCHIVE_DIR, f"node_modules.{digest}.tar.gz")
+
+
+def _try_extract_bundled_archive(cache_dir: str, digest: str) -> bool:
+    """Unpack the sha-tagged bundled archive into `cache_dir` if one
+    exists for the current template digest. Returns True on success,
+    False to signal the caller should fall back to a live `npm install`.
+    The archive is built from the same package.json + package-lock.json
+    sha so the extracted tree is byte-equivalent to `npm ci`."""
+    archive_path = _bundled_archive_path_for(digest)
+    if not os.path.exists(archive_path):
+        return False
+    try:
+        logger.info(
+            "webapp-template: unpacking bundled warm-cache archive %s",
+            archive_path,
+        )
+        os.makedirs(cache_dir, exist_ok=True)
+        # Archive root is `node_modules/`; extracting into cache_dir places
+        # it at the expected path. tarfile uses zlib internally for .gz —
+        # no extra dep needed.
+        with tarfile.open(archive_path, "r:gz") as tar:
+            tar.extractall(cache_dir)
+        cache_modules = os.path.join(cache_dir, "node_modules")
+        if os.path.isdir(cache_modules):
+            return True
+        logger.warning(
+            "webapp-template: bundled archive extracted but no node_modules/ "
+            "directory at %s; falling back to npm install",
+            cache_modules,
+        )
+        return False
+    except Exception as exc:
+        logger.warning(
+            "webapp-template: bundled-archive extract failed (%s); "
+            "falling back to npm install",
+            exc,
+        )
+        return False
+
+
+def _warm_cache_digest() -> str:
+    """Sha of the template's frontend/package.json — used as the cache
+    key + the bundled-archive filename suffix so a package.json bump
+    invalidates both at once."""
     pkg_path = os.path.join(WEBAPP_TEMPLATE_DIR, "frontend", "package.json")
     try:
         with open(pkg_path, "rb") as fh:
-            digest = hashlib.sha256(fh.read()).hexdigest()[:12]
+            return hashlib.sha256(fh.read()).hexdigest()[:12]
     except OSError:
-        digest = "fallback"
+        return "fallback"
+
+
+def _warm_cache_dir() -> str:
+    """Path the warm node_modules lives under. Hashed by package.json so
+    upgrades automatically force a re-populate."""
     base = os.environ.get("OPENSWARM_WEBAPP_CACHE_DIR") or os.path.expanduser(
         "~/.openswarm/cache/webapp_template_node_modules"
     )
-    return os.path.join(base, digest)
+    return os.path.join(base, _warm_cache_digest())
 
 
 def _ensure_warm_cache() -> str | None:
@@ -184,6 +248,13 @@ def _ensure_warm_cache() -> str | None:
     with _warm_cache_lock:
         if os.path.isdir(cache_modules):
             return cache_modules
+        # Fast path: pre-built archive shipped inside the release. The
+        # build script generates this so users hitting OpenSwarm for the
+        # first time skip the ~22 s live `npm install`. Falls through on
+        # any failure so dev installs (no archive) keep working.
+        if _try_extract_bundled_archive(cache_dir, _warm_cache_digest()):
+            logger.info("webapp-template: warm cache ready from bundled archive")
+            return cache_modules
         try:
             os.makedirs(cache_dir, exist_ok=True)
             # Copy package.json + lockfile (if it exists) into the cache
diff --git a/backend/apps/outputs/webapp_template/run.sh b/backend/apps/outputs/webapp_template/run.sh
index 0895346e..cd182530 100755
--- a/backend/apps/outputs/webapp_template/run.sh
+++ b/backend/apps/outputs/webapp_template/run.sh
@@ -8,10 +8,33 @@ if [[ -f "$ROOT_DIR/.env" ]]; then
     set +a
 fi
 
+# Recursively SIGTERM a pid + all of its descendants. We track FRONTEND_PID
+# and BACKEND_PID below, but each of those is a `bash` wrapper that has its
+# own grandchildren (vite, uvicorn, npm). A flat `kill $FRONTEND_PID` leaves
+# the grandchildren alive holding their ports until the OS reaps them
+# minutes later — visible to the user as port-already-in-use the next time
+# they hit the App Builder.
+kill_tree() {
+    local pid=$1 sig=${2:-TERM}
+    local children
+    children=$(pgrep -P "$pid" 2>/dev/null)
+    for child in $children; do
+        kill_tree "$child" "$sig"
+    done
+    kill -"$sig" "$pid" 2>/dev/null
+}
+
+# Previously this was `kill 0`, which SIGTERMs the entire process group.
+# That's fast but propagates UP into OpenSwarm — when this workspace's
+# cleanup fired on ViewEditor unmount or runtime/stop, it tore down the
+# OpenSwarm dev stack (Terminated: 15) and left port 8324 stuck. Now we
+# only kill our own tracked subtree, which keeps containment without
+# requiring an OS-level session wall.
 cleanup() {
     echo ""
     echo "Shutting down all processes..."
-    kill 0 2>/dev/null
+    [[ -n "${FRONTEND_PID:-}" ]] && kill_tree "$FRONTEND_PID" TERM
+    [[ -n "${BACKEND_PID:-}" ]] && kill_tree "$BACKEND_PID" TERM
     wait 2>/dev/null
 }
 trap cleanup EXIT
diff --git a/backend/main.py b/backend/main.py
index 471c902a..1e9e643b 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -85,6 +85,14 @@ app.add_middleware(
     allow_credentials=True,
     allow_methods=["*"],
     allow_headers=["*"],
+    # Every cross-origin POST from the Electron renderer (file:// → http://localhost:8324)
+    # carries Authorization: Bearer, which CORS classifies as non-simple and
+    # forces a preflight OPTIONS before EACH POST. With no max_age the browser
+    # re-preflights on a tight schedule (~5 s in Chromium); under heavy
+    # interaction we observed a 1:1 OPTIONS-to-POST ratio in the dev log,
+    # doubling roundtrip count for no reason. Caching the preflight result
+    # for 10 minutes drops that to one OPTIONS per ~600 POSTs.
+    max_age=600,
 )
 
 
@@ -266,8 +274,19 @@ async def websocket_runtime_logs(websocket: WebSocket, workspace_id: str):
     rt = runtime_manager.get(workspace_id)
     if rt is None:
         # No active runtime — surface that to the client and close. The
-        # frontend will call /runtime/start and reconnect.
+        # frontend will call /runtime/start and reconnect. Also emit a
+        # status frame with is_new_mode (computed from disk) so the
+        # preview pane shows the "starting preview…" placeholder for
+        # webapp_template workspaces instead of falling back to the
+        # legacy /serve/index.html URL (which 404s in new-mode).
         try:
+            from backend.apps.outputs.outputs import _runtime_status_payload
+            status = _runtime_status_payload(workspace_id)
+            await websocket.send_text(json.dumps({
+                "event": "runtime:status",
+                "workspace_id": workspace_id,
+                "data": status,
+            }))
             await websocket.send_text(json.dumps({
                 "event": "runtime:not_attached",
                 "workspace_id": workspace_id,
diff --git a/frontend/public/index.html b/frontend/public/index.html
index b75ab883..dc996177 100644
--- a/frontend/public/index.html
+++ b/frontend/public/index.html
@@ -3,6 +3,33 @@
 <head>
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <!--
+    Renderer CSP. Defense-in-depth: the only attacker model we care about
+    here is a compromised third-party page rendered inside a webview/iframe
+    breaking out into the host renderer. Real production isolation comes
+    from contextIsolation + sandbox in main.js, not this meta — but a CSP
+    silences Electron's "no CSP" dev warning AND blocks <object>/<embed>,
+    base-tag injection, and arbitrary cross-origin script tags as a cheap
+    extra layer. 'unsafe-eval' stays in script-src so webpack-dev-server's
+    HMR keeps working; the packaged build doesn't need it but it's harmless
+    given the bundle origins are 'self' + file:.
+  -->
+  <meta
+    http-equiv="Content-Security-Policy"
+    content="
+      default-src 'self' file: data: blob: http://localhost:* http://127.0.0.1:* https://*.openswarm.com https://api.openswarm.com;
+      script-src 'self' 'unsafe-inline' 'unsafe-eval' file: http://localhost:* http://127.0.0.1:*;
+      style-src 'self' 'unsafe-inline' file: http://localhost:* http://127.0.0.1:* https://fonts.googleapis.com;
+      font-src 'self' data: file: https://fonts.gstatic.com;
+      img-src 'self' data: blob: file: http: https:;
+      media-src 'self' data: blob: http: https:;
+      connect-src 'self' file: http://localhost:* http://127.0.0.1:* ws://localhost:* ws://127.0.0.1:* https://api.openswarm.com https://*.openswarm.com https://openswarm.com https://api.github.com;
+      frame-src 'self' file: http://localhost:* http://127.0.0.1:*;
+      worker-src 'self' blob:;
+      object-src 'none';
+      base-uri 'self';
+    "
+  />
   <title>Open Swarm</title>
   <link rel="icon" href="./favicon.ico?v=2" sizes="16x16 32x32 48x48" />
   <link rel="apple-touch-icon" href="./apple-touch-icon.png" />
diff --git a/frontend/src/app/components/Onboarding/OnboardingPanel.tsx b/frontend/src/app/components/Onboarding/OnboardingPanel.tsx
index 4362f8f4..4d55d32c 100644
--- a/frontend/src/app/components/Onboarding/OnboardingPanel.tsx
+++ b/frontend/src/app/components/Onboarding/OnboardingPanel.tsx
@@ -520,7 +520,7 @@ const StepCardBody: React.FC<StepCardProps> = ({
               // (recorded at a wider canvas than the OpenSwarm window
               // actually filled). Scaling up + overflow:hidden on the
               // parent crops them off the visible thumbnail area.
-              transform: 'scale(1.55)',
+              transform: 'scale(1.0)',
               transformOrigin: 'center',
               pointerEvents: 'none',
             }}
@@ -645,7 +645,7 @@ const StepCardBody: React.FC<StepCardProps> = ({
                   width: '100%',
                   height: '100%',
                   objectFit: 'cover',
-                  transform: 'scale(1.55)',
+                  transform: 'scale(1.0)',
                   transformOrigin: 'center',
                   display: 'block',
                 }}
diff --git a/frontend/src/app/components/Onboarding/ac/ACPopup.tsx b/frontend/src/app/components/Onboarding/ac/ACPopup.tsx
index 848b98f3..f26a6471 100644
--- a/frontend/src/app/components/Onboarding/ac/ACPopup.tsx
+++ b/frontend/src/app/components/Onboarding/ac/ACPopup.tsx
@@ -68,11 +68,22 @@ const ACPopup: React.FC<Props> = ({ text, offset = { x: 0, y: 14 } }) => {
   // Use chained setTimeout (not setInterval) so we can vary the delay
   // per character — punctuation gets an extra beat, mimicking the
   // pacing of Pokémon-style dialog boxes where sentences "land."
+  //
+  // Diagnostic popups (anything containing the literal `[debug]`
+  // marker) skip streaming entirely. The recovery popup that fires on
+  // step failure carries a `[debug] <error message>` suffix so the
+  // user can see WHY a step bailed without opening DevTools — but at
+  // 30 ms/char + 210 ms per punctuation, the suffix takes the full
+  // 14 s popup duration to even start rendering, so by the time the
+  // user reads it the popup is already gone. Instant-render for these
+  // means the diagnostic appears immediately.
+  const isDebugPopup = text.includes('[debug]');
+  const skipStream = isDebugPopup || text.length < STREAM_MIN_CHARS;
   const [streamCount, setStreamCount] = useState<number>(
-    text.length < STREAM_MIN_CHARS ? text.length : 0,
+    skipStream ? text.length : 0,
   );
   useEffect(() => {
-    if (text.length < STREAM_MIN_CHARS) {
+    if (skipStream) {
       setStreamCount(text.length);
       return;
     }
@@ -98,7 +109,7 @@ const ACPopup: React.FC<Props> = ({ text, offset = { x: 0, y: 14 } }) => {
     return () => {
       if (timer !== null) window.clearTimeout(timer);
     };
-  }, [text]);
+  }, [text, skipStream]);
 
   useLayoutEffect(() => {
     const el = ref.current;
diff --git a/frontend/src/app/components/Onboarding/ac/ACTypewriter.ts b/frontend/src/app/components/Onboarding/ac/ACTypewriter.ts
index 49a3cec9..e8a3e8e5 100644
--- a/frontend/src/app/components/Onboarding/ac/ACTypewriter.ts
+++ b/frontend/src/app/components/Onboarding/ac/ACTypewriter.ts
@@ -9,6 +9,14 @@
 // dispatch a real 'input' event. Setting `el.value = ...` directly is
 // silently ignored by React's onChange.
 
+// Version marker so we can verify the dev bundle actually reloaded after
+// editing this file. Check `window.__OPENSWARM_TYPEINTO__` in DevTools
+// — if it's missing or shows an older tag, Electron's renderer is
+// running a cached bundle and needs a Cmd+R hard-reload.
+if (typeof window !== 'undefined') {
+  (window as any).__OPENSWARM_TYPEINTO__ = 'v2-dom-direct-2026-05-12';
+}
+
 const INPUT_PROTO_VALUE_DESC =
   typeof window !== 'undefined'
     ? Object.getOwnPropertyDescriptor(
@@ -43,36 +51,62 @@ function dispatchInput(el: HTMLElement): void {
 }
 
 // contentEditable fields (the agent chat input is one) need a different
-// path. Setting textContent doesn't fire any of the events React's
-// onInput handler listens for, AND it nukes any rich-content children
-// (skill pills, etc). document.execCommand('insertText') is the
-// idiomatic way to programmatically type into a contentEditable — it
-// fires the same `input` events a real keystroke would.
+// path than <input>/<textarea>. Setting textContent nukes rich-content
+// children (skill pills, etc), so we append a Text node at the end and
+// dispatch a real InputEvent that React's reconciler treats as a
+// keystroke. We used to call document.execCommand('insertText') here
+// instead — that's the "idiomatic" way to programmatically type into a
+// contentEditable — but in Electron with a webview loaded in the
+// preview pane (App Builder step 8 / step 5 / step 6 all hit this),
+// the webview steals document focus during its load. execCommand
+// requires the host document to be focused AND the active element to
+// be editable; without focus it silently no-ops while still returning
+// true, so the wizard's `typeInto` "succeeded" but no characters ever
+// landed, hasContent stayed false on the chat input, the send button
+// never rendered, and step 8's `move_to chatSendButton` then burned
+// its 15 s waitForSelector and threw into the recovery popup. The
+// AC's "cursor" is purely visual — it never fires real focus events
+// — so there's no way to get document focus back without the user
+// clicking. DOM-level insertion + dispatched InputEvent works
+// regardless of focus state.
 function insertContentEditableText(el: HTMLElement, ch: string): void {
   el.focus();
-  // Place caret at end so insertion appends rather than overwrites.
+  // Append at the very end of the editable. Walk to the deepest
+  // last-text-node so we don't insert into the middle of a skill pill
+  // wrapper (those are inline-block element children with their own
+  // text). If the last child is an element (e.g., a <span> skill
+  // pill), we append a sibling text node after it.
   const range = document.createRange();
-  range.selectNodeContents(el);
-  range.collapse(false);
+  const last = el.lastChild;
+  if (last && last.nodeType === Node.TEXT_NODE) {
+    range.setStart(last, (last.nodeValue ?? '').length);
+    range.collapse(true);
+    (last as Text).appendData(ch);
+    range.setStart(last, (last.nodeValue ?? '').length);
+    range.collapse(true);
+  } else {
+    const textNode = document.createTextNode(ch);
+    el.appendChild(textNode);
+    range.setStart(textNode, ch.length);
+    range.collapse(true);
+  }
   const sel = window.getSelection();
   if (sel) {
     sel.removeAllRanges();
     sel.addRange(range);
   }
-  // execCommand is deprecated but still the only cross-browser way to
-  // get React-friendly synthetic input events into a contentEditable.
-  // Falls back to direct text-node append if execCommand is rejected
-  // (some embedded webviews disable it).
-  let ok = false;
-  try {
-    ok = document.execCommand('insertText', false, ch);
-  } catch {
-    ok = false;
-  }
-  if (!ok) {
-    el.appendChild(document.createTextNode(ch));
-    el.dispatchEvent(new InputEvent('input', { bubbles: true, data: ch, inputType: 'insertText' }));
-  }
+  // React's controlled-input bridge listens for `input` events. The
+  // `inputType: insertText` + `data: ch` mirrors what a real keystroke
+  // produces, so handleInput → updateHasContent fires and hasContent
+  // flips true → the send button finally renders.
+  el.dispatchEvent(
+    new InputEvent('input', {
+      bubbles: true,
+      cancelable: true,
+      data: ch,
+      inputType: 'insertText',
+    }),
+  );
 }
 
 export interface TypeIntoOptions {
@@ -101,6 +135,18 @@ export async function typeInto(
   const speed = opts.speedMs ?? 18;
   el.focus();
 
+  // Per-character cadence is constant (no jitter — variable timing reads
+  // as glitchy, not natural). The one exception: insert a natural-reading
+  // pause after a comma / sentence-terminator / colon / semicolon so the
+  // streamed text breathes the way a human would. Anything else types at
+  // the constant `speed` value, beat by beat.
+  const punctPause = (ch: string): number => {
+    if (ch === ',') return 220;
+    if (ch === '.' || ch === '!' || ch === '?') return 320;
+    if (ch === ':' || ch === ';') return 180;
+    return 0;
+  };
+
   // Branch on element kind. contentEditable (the agent ChatInput uses
   // a contentEditable div for skill-pill support) requires execCommand;
   // <input>/<textarea> require the React-prototype-setter dance.
@@ -108,7 +154,7 @@ export async function typeInto(
     for (const ch of text) {
       insertContentEditableText(el, ch);
       opts.onTick?.();
-      await new Promise((r) => window.setTimeout(r, speed));
+      await new Promise((r) => window.setTimeout(r, speed + punctPause(ch)));
     }
   } else {
     let acc = '';
@@ -120,7 +166,7 @@ export async function typeInto(
       nativeSetValue(el, acc);
       dispatchInput(el);
       opts.onTick?.();
-      await new Promise((r) => window.setTimeout(r, speed));
+      await new Promise((r) => window.setTimeout(r, speed + punctPause(ch)));
     }
   }
 
diff --git a/frontend/src/app/components/Onboarding/ac/acRuntime.ts b/frontend/src/app/components/Onboarding/ac/acRuntime.ts
index a58055d9..1726e6a1 100644
--- a/frontend/src/app/components/Onboarding/ac/acRuntime.ts
+++ b/frontend/src/app/components/Onboarding/ac/acRuntime.ts
@@ -19,7 +19,7 @@ import {
 import { report, markStepStarted, clearStepTiming } from '../telemetry';
 import { onboardingBus, type OnboardingEvent } from '../eventBus';
 // (gate bump done via onboardingBus.resetReplayGate at runStep entry)
-import { waitForSelector } from '../selectors';
+import { waitForSelector, resolveSelector } from '../selectors';
 import {
   spawnGlowRect,
   clickRipple,
@@ -57,9 +57,10 @@ interface RunContext {
 // (move_to, click, type_into, drag_select, outro) or a popup replacement
 // is allowed to clear it. user-driven transitions (wait_user resolving)
 // also flow through here, but typically the user has already been
-// reading for longer than this anyway. Set to 3s — covers the streaming
-// typewriter cadence plus enough post-stream read time for most popups.
-const MIN_POPUP_DWELL_MS = 3000;
+// reading for longer than this anyway. 6 s = streaming typewriter
+// cadence + ~3 s post-stream read time, which was the user-asked floor
+// for popups that don't require an explicit user action to advance.
+const MIN_POPUP_DWELL_MS = 6000;
 
 // Resolves once `ms` has elapsed or the signal aborts (whichever
 // comes first). Used inside ensurePopupDwell so a step cancel doesn't
@@ -214,13 +215,52 @@ export async function runStep(args: RunStepArgs): Promise<void> {
       }
       const showMessage = !signal.reason || signal.reason !== 'user-cancel';
       if (showMessage) {
+        // Diagnostic: surface a short version of the actual error in
+        // the recovery popup so we can see WHY the step bailed without
+        // needing DevTools open. 180-char cap keeps it readable.
+        const isAbortErr =
+          (err as DOMException)?.name === 'AbortError' || signal.aborted;
+        const errSnippet = isAbortErr
+          ? ''
+          : ((err as Error)?.message ?? String(err)).slice(0, 180);
+        const debugSuffix = errSnippet
+          ? `\n\n[debug] ${errSnippet}`
+          : '';
+        // Stash the full error on window so a dev can grab it from
+        // DevTools (`window.__OPENSWARM_LAST_ONBOARDING_ERR__`) even
+        // if the streaming popup hides the suffix. Full untruncated
+        // message + stack lives here, the 180-char snippet is just
+        // for the popup.
+        try {
+          (window as any).__OPENSWARM_LAST_ONBOARDING_ERR__ = {
+            step_id: step.id,
+            message: (err as Error)?.message ?? String(err),
+            stack: (err as Error)?.stack,
+            at: new Date().toISOString(),
+          };
+          // eslint-disable-next-line no-console
+          console.error(
+            '[onboarding] step bailed:',
+            step.id,
+            (err as Error)?.message ?? err,
+            err,
+          );
+        } catch {
+          /* defensive — never let diagnostics throw */
+        }
         ac.showPopup(
-          "No worries — feel free to explore. Tap Show me whenever you're ready.",
+          "No worries, feel free to explore. Tap Show me whenever you're ready." +
+            debugSuffix,
         );
-        // 3.5s gives most readers enough time to actually parse the
-        // recovery hint. Earlier 1.4s value was tuned for "snappy" but
-        // the popup was vanishing before users could read it.
-        await new Promise<void>((r) => window.setTimeout(r, 3500));
+        // ACPopup streams text at ~30 ms/char + ~210 ms per punctuation
+        // mark, so a 240-char popup (base copy + 180-char debug
+        // suffix) takes ~10 s just to finish streaming. With a 5 s
+        // dwell the [debug] line never even appears on screen before
+        // the popup closes — which is why the user saw only the base
+        // recovery copy in every failure run. 14 s gives the streamer
+        // time to finish AND leaves a few seconds for the user to
+        // actually read the diagnostic line.
+        await new Promise<void>((r) => window.setTimeout(r, 14000));
       }
     } catch {
       /* defensive — never let cleanup throw */
@@ -284,6 +324,16 @@ async function runOps(ops: ACOp[], ctx: RunContext): Promise<void> {
           duration_ms: Date.now() - opStart,
           error: String(err),
         });
+        // Console-visible breadcrumb so a dev with DevTools open can
+        // see WHICH op of WHICH step blew up without parsing telemetry.
+        // The catch in runStep above selectively logs based on error
+        // kind — this is more reliable and pinpoints the failing op.
+        // eslint-disable-next-line no-console
+        console.error(
+          `[onboarding] op failed: step=${ctx.stepId} op#${i}=${op.kind} ` +
+            `duration=${Date.now() - opStart}ms`,
+          { op, error: err },
+        );
       }
       throw err;
     }
@@ -503,40 +553,82 @@ async function runOp(op: ACOp, ctx: RunContext): Promise<void> {
       return;
     }
     case 'type_into': {
-      const el = await waitForSelector(op.target);
-      if (scrollIntoViewIfNeeded(el)) {
-        await sleep(180);
-      }
-      const r = el.getBoundingClientRect();
-      await ac.moveTo(Math.min(r.right - 14, r.left + r.width / 2), r.top + r.height / 2);
-      ac.startTracking(op.target, { x: 0, y: 0 });
-      // Resolve text — string-or-function. Function form lets a step
-      // pick its prompt at run-time based on current Redux state (e.g.
-      // step 3's YouTube vs. web-research fallback).
+      // Resolve text up-front — string-or-function. Function form lets a
+      // step pick its prompt at run-time based on current Redux state
+      // (e.g. step 3's YouTube vs. web-research fallback).
       const resolvedText =
         typeof op.text === 'function' ? op.text(ctx.store.getState()) : op.text;
-      await typeInto(el, resolvedText, { speedMs: op.speedMs });
-      // Anti-revert guard: some controlled contentEditable libraries
-      // re-render on their own schedule and wipe AC's typed text in
-      // the next React commit. Re-check the input value after a brief
-      // beat and re-insert if it got wiped. Without this, the next
-      // op (typically click send) hits a disabled send button because
-      // the input "thinks" it's empty.
-      await sleep(80);
+      const targetTrimmed = resolvedText.trim();
+
       const readText = (e: HTMLElement): string => {
         if (e.isContentEditable) return (e.textContent ?? '').trim();
         if (e instanceof HTMLInputElement || e instanceof HTMLTextAreaElement)
           return (e.value ?? '').trim();
         return (e.textContent ?? '').trim();
       };
-      const target = resolvedText.trim();
-      if (target && readText(el).length < Math.floor(target.length * 0.8)) {
-        // Single-shot re-insert. Same path the typewriter's own
-        // fallback uses for under-load typing drops.
-        if (el.isContentEditable) {
-          el.focus();
+
+      // Type-and-verify is wrapped in a retry loop because the App
+      // Builder's chat input can be detached out from under us mid-
+      // stream: the workspace's `runtime/start → stop → start` cycle +
+      // ViewEditor's seed-then-navigate causes React to swap the
+      // AgentChat instance the user can see, leaving the element our
+      // `el` ref points at detached from the DOM. execCommand fires
+      // silently into the dead node, no text lands, hasContent stays
+      // false, and the send button never renders — which is what was
+      // pushing the wizard into the recovery popup. On a verify-miss
+      // we re-fetch the selector (which now resolves to the FRESH
+      // AgentChat's input) and type again. Two attempts is the max —
+      // a real "the input is genuinely broken" case shouldn't loop.
+      const MAX_ATTEMPTS = 3;
+      for (let attempt = 1; attempt <= MAX_ATTEMPTS; attempt++) {
+        const el = await waitForSelector(op.target);
+        if (scrollIntoViewIfNeeded(el)) {
+          await sleep(180);
+        }
+        const r = el.getBoundingClientRect();
+        await ac.moveTo(
+          Math.min(r.right - 14, r.left + r.width / 2),
+          r.top + r.height / 2,
+        );
+        ac.startTracking(op.target, { x: 0, y: 0 });
+        await typeInto(el, resolvedText, { speedMs: op.speedMs });
+
+        // Let React's onInput commit land before verifying. 80 ms is
+        // enough in the warm-path; we sleep longer between retries
+        // because a remount window is what we're racing.
+        await sleep(80);
+
+        if (!targetTrimmed) return;
+        // Re-fetch in case the original `el` was detached by a remount.
+        // resolveSelector will return whatever the CURRENT canonical
+        // chat-input is in the scope priority order.
+        const currentEl = resolveSelector(op.target);
+        const verifyEl = currentEl ?? el;
+        const landed = readText(verifyEl);
+        if (landed.length >= Math.floor(targetTrimmed.length * 0.8)) {
+          // Success — text is in the live input.
+          return;
+        }
+
+        if (attempt < MAX_ATTEMPTS) {
+          // eslint-disable-next-line no-console
+          console.warn(
+            `[onboarding] type_into verify-miss for "${op.target}" attempt ${attempt}/${MAX_ATTEMPTS} — typed=${landed.length}/${targetTrimmed.length}, retrying`,
+          );
+          // Wait long enough for any in-flight remount + reconcile to
+          // settle. 600 ms is longer than the ~500 ms stability window
+          // wait_for_dom uses, so by the time we retry the DOM is in
+          // its steady state.
+          await sleep(600);
+          continue;
+        }
+
+        // Final attempt — same single-shot re-insert the old anti-
+        // revert guard used, against whatever element is current.
+        if (verifyEl.isContentEditable) {
+          verifyEl.focus();
           const range = document.createRange();
-          range.selectNodeContents(el);
+          range.selectNodeContents(verifyEl);
           const sel = window.getSelection();
           if (sel) {
             sel.removeAllRanges();
@@ -546,14 +638,31 @@ async function runOp(op: ACOp, ctx: RunContext): Promise<void> {
             document.execCommand('delete', false);
             const ok = document.execCommand('insertText', false, resolvedText);
             if (!ok) {
-              el.textContent = resolvedText;
-              el.dispatchEvent(new Event('input', { bubbles: true }));
+              verifyEl.textContent = resolvedText;
+              verifyEl.dispatchEvent(new Event('input', { bubbles: true }));
             }
           } catch {
-            el.textContent = resolvedText;
-            el.dispatchEvent(new Event('input', { bubbles: true }));
+            verifyEl.textContent = resolvedText;
+            verifyEl.dispatchEvent(new Event('input', { bubbles: true }));
           }
         }
+        // One last verify after the fallback — if text STILL didn't land,
+        // throw with a descriptive error so the wizard's catch block
+        // shows a useful diagnostic instead of letting the next op
+        // (move_to chatSendButton) burn 15 s on a button that will
+        // never render because hasContent is false. The thrown message
+        // appears in DevTools console via the op-failed breadcrumb.
+        await sleep(120);
+        const finalLanded = readText(resolveSelector(op.target) ?? verifyEl);
+        if (finalLanded.length < Math.floor(targetTrimmed.length * 0.5)) {
+          throw new Error(
+            `type_into: text never landed in "${op.target}" after ` +
+              `${MAX_ATTEMPTS} attempts (final length=${finalLanded.length}/${targetTrimmed.length}). ` +
+              `The chat input was probably detached by an in-flight remount — ` +
+              `check whether ViewEditor's seed-then-navigate is firing twice ` +
+              `or whether AgentChat's session key is swapping mid-stream.`,
+          );
+        }
       }
       return;
     }
@@ -690,7 +799,7 @@ async function runOp(op: ACOp, ctx: RunContext): Promise<void> {
           step_id: ctx.stepId,
           event: op.condition.event,
         });
-        ac.showPopup("Didn't seem to go through — try again?");
+        ac.showPopup("Didn't seem to go through. Try again?");
         ctx.popupShownAt.current = performance.now();
         await waitForCondition(
           op.condition,
@@ -733,19 +842,68 @@ async function runOp(op: ACOp, ctx: RunContext): Promise<void> {
     case 'wait_for_dom': {
       const timeoutMs = op.timeoutMs ?? 8000;
       const POLL_MS = 100;
+      // Stability gate: the matched element has to be the SAME node for
+      // STABILITY_POLLS consecutive polls (≈ 500 ms continuous presence)
+      // before we return success. Without this, step 8 was finding the
+      // App Builder's chat-input on poll N, returning, then the next
+      // op's typing ran straight into AgentChat's remount (the
+      // `runtime/start → stop → start` cycle from a draftLaunchMap swap
+      // + React Strict Mode double-effect) — the input became detached
+      // mid-stream, execCommand('insertText') silently no-op'd into the
+      // dead node, no text landed, hasContent stayed false, the send
+      // button was never rendered, and the wizard's next move_to
+      // chatSendButton burned its 15 s waitForSelector and threw into
+      // the recovery popup. Requiring stable identity walls off the
+      // remount window so we only proceed once the runtime has settled.
+      const STABILITY_POLLS = 5;
       const startedAt = performance.now();
+      let stableEl: Element | null = null;
+      let stableCount = 0;
       while (performance.now() - startedAt < timeoutMs) {
         if (signal.aborted) {
           throw new DOMException('aborted', 'AbortError');
         }
-        if (document.querySelector(op.css)) return;
+        const hit = document.querySelector(op.css);
+        if (hit) {
+          if (hit === stableEl) {
+            stableCount += 1;
+            if (stableCount >= STABILITY_POLLS) return;
+          } else {
+            stableEl = hit;
+            stableCount = 1;
+          }
+        } else {
+          stableEl = null;
+          stableCount = 0;
+        }
         await sleep(POLL_MS);
       }
-      // Soft-success on timeout — same policy as wait_user's event_bus
-      // path. The next op (usually move_to / type_into) will hit its own
-      // waitForSelector and surface a clearer error if the target is
-      // genuinely missing.
-      return;
+      // Hard error on timeout, with DOM-state diagnostics so the dev
+      // console tells us WHY the selector didn't match — bare selector
+      // mismatch vs. the marker being on the right element but the
+      // wrong scope vs. nothing in DOM at all are three different bugs
+      // and we couldn't tell which from "step failed".
+      const scopeEls = Array.from(
+        document.querySelectorAll('[data-onboarding-scope]'),
+      ).map((e) => (e as HTMLElement).getAttribute('data-onboarding-scope'));
+      const chatInputEls = Array.from(
+        document.querySelectorAll('[data-onboarding="chat-input"]'),
+      );
+      const chatInputScopes = chatInputEls.map((el) => {
+        let p: HTMLElement | null = el.parentElement;
+        while (p) {
+          const s = p.getAttribute('data-onboarding-scope');
+          if (s) return s;
+          p = p.parentElement;
+        }
+        return '<no-scope>';
+      });
+      const msg =
+        `wait_for_dom: "${op.css}" did not appear within ${timeoutMs}ms ` +
+        `[scopes=${JSON.stringify(scopeEls)}; chatInputs=${chatInputEls.length}; ` +
+        `chatInputScopes=${JSON.stringify(chatInputScopes)}]`;
+      console.error('[onboarding]', msg);
+      throw new Error(msg);
     }
     case 'outro': {
       await ac.fadeOut(ctx.spawnPoint);
diff --git a/frontend/src/app/components/Onboarding/steps/step08_makeApp.ts b/frontend/src/app/components/Onboarding/steps/step08_makeApp.ts
index b273f5ea..ff40ebff 100644
--- a/frontend/src/app/components/Onboarding/steps/step08_makeApp.ts
+++ b/frontend/src/app/components/Onboarding/steps/step08_makeApp.ts
@@ -23,14 +23,28 @@ export const step08: OnboardingStep = {
       condition: { kind: 'click_target', target: S.appsNewButton },
     },
     // After clicking +, the /apps/new route mounts ViewEditor which
-    // asynchronously renders AgentChat in the left pane (model probe +
-    // initial fetch). The chat-input data-onboarding marker can land
-    // on a DIFFERENT agent's chat (one of the dashboard cards) before
-    // the App Builder's own scope mounts, so we wait for the scoped
-    // marker specifically. wait_for_dom polls every 100ms up to 8s —
-    // instant on warm starts, patient on cold ones. Replaces the prior
-    // fixed 1500ms delay that under-fit slow boots and added latency
-    // on fast ones.
+    // asynchronously renders AgentChat in the left pane. Three failure
+    // modes we have to defend against:
+    //   1. Cold start can take well over 8 s before AgentChat mounts
+    //      inside the app-builder scope wrapper — vite warm-up + session
+    //      creation + three parallel onboarding sessions racing the
+    //      backend's probe-model queue stack up under load.
+    //   2. The /apps/new route briefly mounts → unmounts → remounts
+    //      ViewEditor (runtime/start → runtime/stop → runtime/start
+    //      visible in the dev log when the React Strict-Mode double-
+    //      effect collides with the route transition). The scope
+    //      wrapper disappears during the unmount, and wait_for_dom
+    //      polling can land in that gap.
+    //   3. AgentChat's hardcoded `disabled={false}` means the
+    //      contenteditable attribute is always "true" when the input
+    //      mounts — so we don't need to gate on it (and gating on a
+    //      stringly-serialized React attribute introduces a brittle
+    //      dependency on React's attribute reflection).
+    //
+    // Fix: wait for the SCOPED chat-input. 30 s timeout swallows any
+    // reasonable cold start including the mount-unmount-remount cycle.
+    // An extra 350 ms `delay` lets the post-mount React commit settle
+    // (refs, event handlers, focus shims) before we move the cursor.
     {
       kind: 'popup',
       text: 'Loading the App Builder...',
@@ -38,8 +52,9 @@ export const step08: OnboardingStep = {
     {
       kind: 'wait_for_dom',
       css: '[data-onboarding-scope="app-builder"] [data-onboarding="chat-input"]',
-      timeoutMs: 8000,
+      timeoutMs: 60000,
     },
+    { kind: 'delay', ms: 350 },
     // The App Builder chat lives in the left pane on /apps/new — the
     // chat-input selector resolves to it via the App Builder scope
     // priority in resolveSelector.
@@ -51,6 +66,10 @@ export const step08: OnboardingStep = {
       speedMs: 12,
     },
     // AC auto-clicks send per spec ("the AC should auto send this").
+    // Tiny pause first to let onInput's draft-state commit land — the
+    // send button is disabled-while-empty, so clicking before React's
+    // next commit sometimes lands on the stale-disabled button.
+    { kind: 'delay', ms: 120 },
     { kind: 'move_to', target: S.chatSendButton },
     { kind: 'click', target: S.chatSendButton, simulate: true },
     // Wait only for chat:message_sent (the prompt actually going out).
diff --git a/frontend/src/app/pages/Views/ViewEditor.tsx b/frontend/src/app/pages/Views/ViewEditor.tsx
index 894bdee6..907495b5 100644
--- a/frontend/src/app/pages/Views/ViewEditor.tsx
+++ b/frontend/src/app/pages/Views/ViewEditor.tsx
@@ -465,9 +465,37 @@ const ViewEditor: React.FC<Props> = ({ output }) => {
           // Replace /apps/new in the URL with /apps/{output_id} so a
           // reload (or back-button return) lands back on the same
           // workspace instead of spinning up yet another fresh seed.
-          // Use replace so /apps/new doesn't pile up in history.
+          //
+          // CRITICAL: bypass React Router (`navigate()`) and use the
+          // raw `window.history.replaceState` instead. Views.tsx
+          // renders <ViewEditor key={editingOutput?.id ?? 'new'} />
+          // — a React-Router-driven path change from /apps/new to
+          // /apps/<id> would flip that key, React would UNMOUNT this
+          // ViewEditor and MOUNT a new one, AgentChat's chat-input DOM
+          // node would get a new identity, and the onboarding wizard's
+          // type_into would silently fire into the now-detached old
+          // input (no text lands, hasContent stays false, send button
+          // never renders, wizard burns 15 s on waitForSelector and
+          // throws into the recovery popup). window.history.replaceState
+          // changes the URL without triggering Views' re-render, so
+          // ViewEditor stays mounted and the chat-input the wizard
+          // already found is the same one it types into. On hard
+          // reload React Router reads the live URL fresh, so the
+          // back-button / reload behavior is preserved.
           if (window.location.hash.includes('/apps/new')) {
-            navigate(`/apps/${data.output_id}`, { replace: true });
+            const newHash = window.location.hash.replace(
+              '/apps/new',
+              `/apps/${data.output_id}`,
+            );
+            try {
+              window.history.replaceState(null, '', newHash);
+            } catch {
+              // Fallback to React Router nav if the history API rejects
+              // (extremely unusual; mostly defensive). Accepts the
+              // remount cost in that edge case rather than dropping
+              // the URL update entirely.
+              navigate(`/apps/${data.output_id}`, { replace: true });
+            }
           }
         }
         const action = dispatch(createDraftSession({
@@ -576,11 +604,38 @@ const ViewEditor: React.FC<Props> = ({ output }) => {
 
   useEffect(() => {
     if (!workspaceId) return;
-    pollWorkspace();
     const interval = isAgentActive ? POLL_INTERVAL_ACTIVE_MS : POLL_INTERVAL_IDLE_MS;
-    pollRef.current = setInterval(pollWorkspace, interval);
+
+    // Visibility-gate the poll loop. When the App Builder tab is
+    // hidden (user navigated to Dashboard / Skills / Actions / a
+    // different Electron window), there's no UI to update — but the
+    // interval would otherwise keep hitting `/api/outputs/workspace`
+    // every 2s, blocking the foreground backend's other endpoints.
+    // On `hidden` we clear the timer entirely; on `visible` we fire
+    // one immediate poll (to catch up on whatever the agent wrote
+    // while we were away) then restart the interval. Reuses the
+    // existing isAgentActive-driven cadence.
+    const startPoll = () => {
+      if (pollRef.current) return;
+      pollWorkspace();
+      pollRef.current = setInterval(pollWorkspace, interval);
+    };
+    const stopPoll = () => {
+      if (pollRef.current) {
+        clearInterval(pollRef.current);
+        pollRef.current = null;
+      }
+    };
+    const onVisibilityChange = () => {
+      if (document.visibilityState === 'visible') startPoll();
+      else stopPoll();
+    };
+
+    if (document.visibilityState === 'visible') startPoll();
+    document.addEventListener('visibilitychange', onVisibilityChange);
     return () => {
-      if (pollRef.current) clearInterval(pollRef.current);
+      document.removeEventListener('visibilitychange', onVisibilityChange);
+      stopPoll();
     };
   }, [workspaceId, pollWorkspace, isAgentActive]);
 
@@ -783,8 +838,29 @@ const ViewEditor: React.FC<Props> = ({ output }) => {
   // 404s — new-mode workspaces have no `index.html` at root, only
   // `frontend/index.html` reachable via Vite).
   const [isNewModeRuntime, setIsNewModeRuntime] = useState(false);
+  // Has runtime/start been fired for this workspace yet? Used by the
+  // tab-gated lifecycle below so we only POST start the FIRST time the
+  // user lands on (or switches to) Preview/Terminal. Switching between
+  // tabs after that is a no-op — the runtime is already up and the
+  // WS is already streaming. Reset when workspaceId changes so a new
+  // workspace gets its own one-shot.
+  const runtimeStartedRef = useRef(false);
+  useEffect(() => {
+    runtimeStartedRef.current = false;
+  }, [workspaceId]);
+
   useEffect(() => {
     if (!workspaceId) return;
+    // Defer the workspace runtime spawn until the user actually wants
+    // to see/hear from it. Code tab is pure editor — no need to pay
+    // the ~1-2s vite + uvicorn cold-start until they click Preview or
+    // Terminal. After the first entry, the runtime stays up (LRU pools
+    // it on unmount), so subsequent tab flips are free.
+    const wantsRuntime = activeTab === TAB_PREVIEW || activeTab === TAB_TERMINAL;
+    if (!wantsRuntime && !runtimeStartedRef.current) return;
+    if (runtimeStartedRef.current) return;
+    runtimeStartedRef.current = true;
+
     let cancelled = false;
     let ws: WebSocket | null = null;
     setFrontendUrl(null); // reset when workspace changes
@@ -846,7 +922,7 @@ const ViewEditor: React.FC<Props> = ({ output }) => {
         headers,
       }).catch(() => {});
     };
-  }, [workspaceId, appendTerminalLine]);
+  }, [workspaceId, appendTerminalLine, activeTab]);
 
   // Preview URL: prefer the new-mode Vite dev server when the runtime
   // reports one; otherwise fall back to the legacy serve endpoint.
diff --git a/frontend/src/app/pages/Views/ViewPreview.tsx b/frontend/src/app/pages/Views/ViewPreview.tsx
index d7a4fd5f..078496ea 100644
--- a/frontend/src/app/pages/Views/ViewPreview.tsx
+++ b/frontend/src/app/pages/Views/ViewPreview.tsx
@@ -1,5 +1,7 @@
-import React, { useRef, useEffect, useMemo, forwardRef, useImperativeHandle, useState } from 'react';
+import React, { useRef, useEffect, useMemo, useCallback, forwardRef, useImperativeHandle, useState } from 'react';
 import Box from '@mui/material/Box';
+import Typography from '@mui/material/Typography';
+import { Skeleton } from '@/app/components/Loading';
 import { useElementSelection } from '@/app/components/ElementSelectionContext';
 import { useIframeElementSelector } from './useIframeElementSelector';
 import { getAuthToken, ensureAuthToken } from '@/shared/config';
@@ -92,6 +94,50 @@ const ViewPreview = forwardRef<ViewPreviewHandle, Props>(({
     return `${serveUrl}${sep}_d=${encodeURIComponent(dataParam)}&_v=${reloadKey}&token=${encodeURIComponent(authToken)}`;
   }, [serveUrl, inputData, backendResult, reloadKey, authToken]);
 
+  // Pause the iframe when the Electron window is hidden (minimized, occluded,
+  // user switched to a different desktop space). Vite's HMR client keeps a
+  // WS heartbeat open + the app's rAF loops keep running otherwise — pure
+  // wasted CPU since nobody can see the result. Swap to about:blank, which
+  // destroys the previous document and closes its HMR connection cleanly.
+  // Only applies to URL-mode (vite dev server). Srcdoc apps stay put — they
+  // don't run HMR and pausing them would silently wipe arbitrary in-memory
+  // user state.
+  const [windowHidden, setWindowHidden] = useState(
+    () => typeof document !== 'undefined' && document.visibilityState === 'hidden',
+  );
+  useEffect(() => {
+    const onVis = () => setWindowHidden(document.visibilityState === 'hidden');
+    document.addEventListener('visibilitychange', onVis);
+    return () => document.removeEventListener('visibilitychange', onVis);
+  }, []);
+
+  const effectiveSrc = useMemo(() => {
+    if (!iframeSrc) return iframeSrc;
+    return windowHidden ? 'about:blank' : iframeSrc;
+  }, [iframeSrc, windowHidden]);
+
+  // "Restoring preview…" overlay covers the gap between window-restore and
+  // the iframe finishing its second navigation back to the dev server. Set
+  // on hidden→visible transition; cleared by iframe load (or 5 s safety).
+  const [restoring, setRestoring] = useState(false);
+  const wasHiddenRef = useRef(windowHidden);
+  useEffect(() => {
+    if (wasHiddenRef.current && !windowHidden && iframeSrc) {
+      setRestoring(true);
+      const t = window.setTimeout(() => setRestoring(false), 5000);
+      wasHiddenRef.current = windowHidden;
+      return () => window.clearTimeout(t);
+    }
+    wasHiddenRef.current = windowHidden;
+    return undefined;
+  }, [windowHidden, iframeSrc]);
+
+  const handleNavigationLoad = useCallback(() => {
+    // load fires for both the about:blank pause-step AND the restored URL —
+    // only the latter should clear the overlay.
+    if (!windowHidden) setRestoring(false);
+  }, [windowHidden]);
+
   const srcdoc = useMemo(() => {
     if (serveUrl || !frontendCode) return undefined;
     return buildSrcdoc(frontendCode, inputData, backendResult);
@@ -169,6 +215,19 @@ const ViewPreview = forwardRef<ViewPreviewHandle, Props>(({
     };
   }, [useWebview, onConsoleMessage, iframeSrc]);
 
+  // Webviews don't surface a React-style `onLoad` prop; subscribe to the
+  // Electron-specific `did-finish-load` event to clear the restoring
+  // overlay after the about:blank→iframeSrc transition completes.
+  useEffect(() => {
+    if (!useWebview) return;
+    const wv = webviewRef.current;
+    if (!wv) return;
+    wv.addEventListener?.('did-finish-load', handleNavigationLoad);
+    return () => {
+      try { wv.removeEventListener?.('did-finish-load', handleNavigationLoad); } catch (_e) {}
+    };
+  }, [useWebview, handleNavigationLoad]);
+
   const hasContent = !!(serveUrl || frontendCode?.trim());
 
   if (!hasContent) {
@@ -224,7 +283,7 @@ const ViewPreview = forwardRef<ViewPreviewHandle, Props>(({
           // — preserves the prior frame's pixels through reload, same
           // pattern as the iframe path.
           key="url-mode-webview"
-          src={iframeSrc}
+          src={effectiveSrc}
           // Autoplay is the most common cross-app expectation; matches
           // the BrowserCard default. Plugins / nodeintegration stay off.
           webpreferences="autoplayPolicy=no-user-gesture-required"
@@ -248,7 +307,8 @@ const ViewPreview = forwardRef<ViewPreviewHandle, Props>(({
           // keeping the prior frame's pixels visible until the new doc
           // paints. No flash.
           key={iframeSrc ? 'url-mode' : 'srcdoc'}
-          src={iframeSrc}
+          src={effectiveSrc}
+          onLoad={handleNavigationLoad}
           sandbox="allow-scripts allow-same-origin"
           style={{
             width: '100%',
@@ -260,6 +320,27 @@ const ViewPreview = forwardRef<ViewPreviewHandle, Props>(({
           title="App Preview"
         />
       )}
+      {restoring && (
+        <Box
+          sx={{
+            position: 'absolute',
+            inset: 0,
+            display: 'flex',
+            flexDirection: 'column',
+            alignItems: 'center',
+            justifyContent: 'center',
+            gap: 1.5,
+            bgcolor: '#fff',
+            zIndex: 2,
+            pointerEvents: 'none',
+          }}
+        >
+          <Skeleton variant="card" width={140} height={14} delayMs={0} />
+          <Typography sx={{ fontSize: '0.78rem', color: '#888', letterSpacing: '0.01em' }}>
+            Restoring preview…
+          </Typography>
+        </Box>
+      )}
     </Box>
   );
 });
diff --git a/frontend/src/shared/config.ts b/frontend/src/shared/config.ts
index ea95b677..bbabd46b 100644
--- a/frontend/src/shared/config.ts
+++ b/frontend/src/shared/config.ts
@@ -49,6 +49,23 @@ export function ensureAuthToken(): Promise<string> {
 // Covers the analytics, settings, agents, dashboards, etc. fetches.
 // Only applies to requests that target our own API_BASE — pass-through
 // for every other URL (3rd-party APIs, asset CDNs, etc.).
+//
+// Layered on top of the auth-injection: a tiny in-flight dedupe + 1s
+// success cache for GETs. The onboarding flow + dashboard load fire the
+// same `GET /api/agents/sessions/<id>` / `GET /api/skills/list` /
+// `GET /api/skills/workspace/<id>` two-to-five times in quick
+// succession when components mount near-simultaneously — without
+// dedupe we paid a full roundtrip every time. With this in place the
+// second-through-Nth call inside a 1 s window either piggybacks on
+// the in-flight promise OR reads a freshly-cached Response. Cache is
+// keyed by `METHOD URL`, scoped to GET only (mutations always fall
+// through), and a Response.clone() per consumer keeps each caller's
+// body stream independent. Non-2xx responses are NOT cached so a
+// transient 5xx can't poison the next click.
+const _inflightFetches = new Map<string, Promise<Response>>();
+const _cachedFetches = new Map<string, { resp: Response; expiresAt: number }>();
+const _GET_CACHE_TTL_MS = 1000;
+
 function _installAuthFetchInterceptor() {
   if ((window as any).__OPENSWARM_FETCH_PATCHED__) return;
   (window as any).__OPENSWARM_FETCH_PATCHED__ = true;
@@ -63,16 +80,60 @@ function _installAuthFetchInterceptor() {
 
       // Don't override an explicit Authorization the caller already set.
       const existingHeaders = new Headers(init?.headers ?? (input instanceof Request ? input.headers : undefined));
-      if (existingHeaders.has('Authorization') || existingHeaders.has('authorization')) {
-        return originalFetch(input, init);
+      const callerSetAuth = existingHeaders.has('Authorization') || existingHeaders.has('authorization');
+
+      let finalInit: RequestInit | undefined = init;
+      if (!callerSetAuth) {
+        const token = _authTokenCache || (await ensureAuthToken());
+        if (token) {
+          existingHeaders.set('Authorization', `Bearer ${token}`);
+          finalInit = { ...(init ?? {}), headers: existingHeaders };
+        }
       }
 
-      const token = _authTokenCache || (await ensureAuthToken());
-      if (!token) return originalFetch(input, init);
+      const method = (
+        finalInit?.method
+        ?? (input instanceof Request ? input.method : 'GET')
+      ).toUpperCase();
 
-      existingHeaders.set('Authorization', `Bearer ${token}`);
-      const newInit: RequestInit = { ...(init ?? {}), headers: existingHeaders };
-      return originalFetch(input, newInit);
+      // Only GET is safe to dedupe + cache. POST/PUT/PATCH/DELETE have
+      // side effects — collapsing two intentional calls (e.g. user
+      // double-clicked Send) would be wrong, so we always pass through.
+      if (method !== 'GET') {
+        return originalFetch(input, finalInit);
+      }
+
+      const cacheKey = `GET ${url}`;
+
+      const cached = _cachedFetches.get(cacheKey);
+      if (cached && cached.expiresAt > Date.now()) {
+        return cached.resp.clone();
+      } else if (cached) {
+        _cachedFetches.delete(cacheKey);
+      }
+
+      const inflight = _inflightFetches.get(cacheKey);
+      if (inflight) {
+        const resp = await inflight;
+        return resp.clone();
+      }
+
+      const promise = originalFetch(input, finalInit).then((resp) => {
+        if (resp.ok) {
+          _cachedFetches.set(cacheKey, {
+            resp: resp.clone(),
+            expiresAt: Date.now() + _GET_CACHE_TTL_MS,
+          });
+        }
+        return resp;
+      });
+      _inflightFetches.set(cacheKey, promise);
+      try {
+        const resp = await promise;
+        return resp.clone();
+      } finally {
+        _inflightFetches.delete(cacheKey);
+      }
     } catch {
       return originalFetch(input, init);
     }
diff --git a/frontend/src/shared/state/agentsSlice.ts b/frontend/src/shared/state/agentsSlice.ts
index 4e50ff9f..cb7f03a1 100644
--- a/frontend/src/shared/state/agentsSlice.ts
+++ b/frontend/src/shared/state/agentsSlice.ts
@@ -305,8 +305,17 @@ export interface LaunchAndSendPayload {
 
 export const fetchSession = createAsyncThunk(
   'agents/fetchSession',
-  async (sessionId: string) => {
+  async (sessionId: string, { rejectWithValue }) => {
     const res = await fetch(`${AGENTS_API}/sessions/${sessionId}`);
+    if (!res.ok) {
+      // 404 is the common case: AgentChat is rehydrating from a URL hash
+      // that points at a session the user deleted (or that never made it
+      // to disk after a crash). Surface a structured rejection so the
+      // .rejected reducer can purge the stale id from `state.sessions`
+      // instead of leaving it as a phantom entry that the next mount
+      // will re-fetch right back into a 404.
+      return rejectWithValue({ sessionId, status: res.status });
+    }
     const session = await res.json();
     return session as AgentSession;
   }
@@ -1277,6 +1286,25 @@ const agentsSlice = createSlice({
           tool_group_meta: session.tool_group_meta ?? existing?.tool_group_meta ?? {},
         };
       })
+      .addCase(fetchSession.rejected, (state, action) => {
+        // Stale-id cleanup: if the backend returned 404, the session no
+        // longer exists — strip it from state so AgentChat can short-
+        // circuit to a "session not found" view instead of looping the
+        // same dead fetch on every remount. Also clears activeSessionId
+        // if it was pointing at the dead id, so the dashboard doesn't
+        // keep highlighting a ghost.
+        const payload = action.payload as { sessionId?: string; status?: number } | undefined;
+        const sessionId = payload?.sessionId;
+        if (!sessionId) return;
+        if (payload?.status === 404 || payload?.status === 410) {
+          delete state.sessions[sessionId];
+          if (state.activeSessionId === sessionId) {
+            state.activeSessionId = null;
+          }
+          state.expandedSessionIds = state.expandedSessionIds.filter((id) => id !== sessionId);
+          state.trackedNotificationIds = state.trackedNotificationIds.filter((id) => id !== sessionId);
+        }
+      })
       .addCase(fetchBrowserAgentChildren.fulfilled, (state, action) => {
         for (const session of action.payload) {
           if (!state.sessions[session.id]) {
diff --git a/run.sh b/run.sh
index 341939de..1059bc8e 100755
--- a/run.sh
+++ b/run.sh
@@ -84,6 +84,19 @@ if [ ! -f "$UV_BIN_DIR/uvx" ]; then
     rm -rf /tmp/uv-*-apple-darwin
 fi
 
+# --- Reap any backend leftover from a prior unclean exit ---
+# If the user double-Ctrl+C'd a previous run, or a workspace's signal
+# propagation killed the parent before cleanup() ran SIGKILL, uvicorn
+# can still be bound to :8324 even though the shell prompt returned.
+# That makes the next `bash run.sh` fail with Errno 48 "Address already
+# in use" and leaves the user thinking the dev loop is broken. Free the
+# port up front instead of asking the user to debug.
+if lsof -ti :8324 >/dev/null 2>&1; then
+    echo -e "${YELLOW}${BOLD}[preflight]${RESET} Port 8324 still bound from a prior run — killing stale process..."
+    lsof -ti :8324 | xargs kill -9 2>/dev/null || true
+    sleep 0.3
+fi
+
 # --- Start backend ---
 # Mark this as a dev launch so backend/run.sh enables --reload. Packaged
 # builds never run this top-level script (Electron spawns backend
diff --git a/scripts/build-app.sh b/scripts/build-app.sh
index 348f9e2f..9f36ce2d 100755
--- a/scripts/build-app.sh
+++ b/scripts/build-app.sh
@@ -346,6 +346,19 @@ else
 fi
 echo ""
 
+# Step 3c: Pre-build the webapp-template node_modules archive so first-app
+# create on a fresh user install decompresses (~3 s) instead of running a
+# live `npm install` (~22 s). The backend's _try_extract_bundled_archive
+# is sha-tagged + falls through cleanly if the archive is missing or
+# stale, so this step is purely an optimization — skip silently if the
+# template snapshot or npm aren't available.
+if [[ -f "$PROJECT_ROOT/backend/apps/outputs/webapp_template/frontend/package.json" ]] \
+   && command -v npm >/dev/null 2>&1; then
+    echo "[3c/5] Pre-building webapp-template node_modules archive..."
+    bash "$PROJECT_ROOT/scripts/build-template-archive.sh"
+    echo ""
+fi
+
 # Step 4: Snapshot source directories for packaging
 # (Router was already staged in step 3; do not touch STAGING_DIR/router/ here.)
 echo "[4/5] Snapshotting source directories..."
diff --git a/scripts/build-template-archive.sh b/scripts/build-template-archive.sh
new file mode 100755
index 00000000..4b8455dc
--- /dev/null
+++ b/scripts/build-template-archive.sh
@@ -0,0 +1,80 @@
+#!/bin/bash
+# Build the pre-compressed webapp-template node_modules archive that gets
+# bundled into signed releases. Backend code (_try_extract_bundled_archive
+# in view_builder_templates.py) unpacks this on first-app create instead
+# of running a live `npm install`, dropping cold-start ~22 s → ~3 s.
+#
+# Run this once before packaging (CI / publish.sh / publish-win.ps1).
+# Local dev installs that skip this step transparently fall through to
+# live `npm install` — the archive is purely an optimization.
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
+TEMPLATE_DIR="$PROJECT_ROOT/backend/apps/outputs/webapp_template"
+OUT_DIR="$PROJECT_ROOT/backend/apps/outputs/webapp_template_cache"
+
+if [[ ! -f "$TEMPLATE_DIR/frontend/package.json" ]]; then
+    echo "ERROR: $TEMPLATE_DIR/frontend/package.json not found"
+    echo "Run scripts/fetch-webapp-template.sh first to populate the template."
+    exit 1
+fi
+
+# Tag the archive with a sha of package.json so a stale archive from a
+# previous template version is automatically skipped at runtime (the
+# backend's _bundled_archive_path_for() computes the same digest). The
+# 12-char prefix mirrors view_builder_templates._warm_cache_digest().
+if command -v shasum >/dev/null 2>&1; then
+    PKG_DIGEST=$(shasum -a 256 "$TEMPLATE_DIR/frontend/package.json" | awk '{print substr($1,1,12)}')
+elif command -v sha256sum >/dev/null 2>&1; then
+    PKG_DIGEST=$(sha256sum "$TEMPLATE_DIR/frontend/package.json" | awk '{print substr($1,1,12)}')
+else
+    echo "ERROR: neither shasum nor sha256sum found on PATH"
+    exit 1
+fi
+OUT_ARCHIVE="$OUT_DIR/node_modules.${PKG_DIGEST}.tar.gz"
+
+# Work in a temp dir so a failed install can't corrupt the template tree.
+WORK_DIR=$(mktemp -d -t openswarm-template-archive-XXXXXX)
+trap "rm -rf '$WORK_DIR'" EXIT
+
+echo "Building template node_modules archive..."
+echo "  source : $TEMPLATE_DIR/frontend/"
+echo "  digest : $PKG_DIGEST"
+echo "  staging: $WORK_DIR"
+echo "  output : $OUT_ARCHIVE"
+echo ""
+
+cp "$TEMPLATE_DIR/frontend/package.json" "$WORK_DIR/package.json"
+if [[ -f "$TEMPLATE_DIR/frontend/package-lock.json" ]]; then
+    cp "$TEMPLATE_DIR/frontend/package-lock.json" "$WORK_DIR/package-lock.json"
+    cd "$WORK_DIR"
+    echo "[npm] running npm ci..."
+    npm ci --prefer-offline --no-audit --no-fund --loglevel=error
+else
+    cd "$WORK_DIR"
+    echo "[npm] running npm install (no lockfile)..."
+    npm install --prefer-offline --no-audit --no-fund --loglevel=error
+fi
+
+if [[ ! -d "$WORK_DIR/node_modules" ]]; then
+    echo "ERROR: npm did not produce node_modules in $WORK_DIR"
+    exit 1
+fi
+
+mkdir -p "$OUT_DIR"
+echo ""
+echo "[tar] compressing node_modules..."
+# `tar -C "$WORK_DIR" node_modules` so the archive root is `node_modules/`,
+# matching what _try_extract_bundled_archive expects when extracting into
+# cache_dir.
+tar -czf "$OUT_ARCHIVE" -C "$WORK_DIR" node_modules
+
+ARCHIVE_SIZE=$(du -h "$OUT_ARCHIVE" | awk '{print $1}')
+NM_FILES=$(find "$WORK_DIR/node_modules" -type f | wc -l | tr -d ' ')
+echo ""
+echo "Done."
+echo "  archive   : $OUT_ARCHIVE"
+echo "  size      : $ARCHIVE_SIZE"
+echo "  files in  : $NM_FILES"