diff --git a/app_backup.py b/app_backup.py
index 68061c4..4de06cd 100644
--- a/app_backup.py
+++ b/app_backup.py
@@ -23,6 +23,7 @@ import zipfile
 
 import app_state
 import sab_app
+import sox
 from ox_widget_properties import IMAGE_EXTENSIONS, ORION_KIT, RION_KIT
 
 APP_SAB = "app.sab"
@@ -159,6 +160,19 @@ def _source_entry(media, source_path):
     return f"{media.bank_folder}/{file_name}"
 
 
+def save_app(client):
+    """Invokes App.save on the device and waits for it to finish.
+
+    Ontrol's Niagara driver does this before every app.sab get, resending the request
+    only every 5 s: a P-ION saving a large app takes seconds, and 1 s resends of the
+    request while it is busy are what knocked it over.
+    """
+    comp = client.cache_get(0) or client.load(0)
+    slots = client.slot_registry.get((comp.kit_id, comp.type_id)) or []
+    slot = next((s for s in slots if s["name"] == "save" and s.get("is_action")), None)
+    client.invoke(0, slot["id"] if slot else 0, send_retry=sox.SAVE_SEND_RETRY)
+
+
 class BackupResult:
     def __init__(self):
         self.path = None
@@ -171,8 +185,9 @@ class BackupResult:
 def get_with_file(client, path, status=None):
     """Reads the app and its media off the device and writes the backup zip to `path`.
 
-    Runs off the main thread; status(text, fraction) reports progress. Returns a
-    BackupResult; a failure to read app.sab or kits.scode raises.
+    The app is saved on the device first, so app.sab holds what is running. Runs off
+    the main thread; status(text, fraction) reports progress. Returns a BackupResult;
+    a failure to save, or to read app.sab or kits.scode, raises.
     """
     def report(text, fraction=None):
         if status:
@@ -190,6 +205,11 @@ def get_with_file(client, path, status=None):
     result = BackupResult()
     entries = []                                    # (zip name, bytes or local path)
 
+    report("Saving the app on the device ...", 0.0)
+    try:
+        save_app(client)
+    except Exception as e:
+        raise RuntimeError(f"Saving the app on the device: {e}") from e
     sab = fetch(APP_SAB, 0.0, 0.15)
     entries.append(("device/" + APP_SAB, sab))
     entries.append(("device/" + KITS_SCODE, fetch(KITS_SCODE, 0.15, 0.35)))
diff --git a/app_state.py b/app_state.py
index 5a83730..de2a7fa 100644
--- a/app_state.py
+++ b/app_state.py
@@ -8,7 +8,7 @@ so later rebinding would only ever be seen by the module that did it.
 import configparser
 import os
 
-VERSION = "0.0.0.143"
+VERSION = "0.0.0.144"
 PROPERTIES_FILE = os.path.join(os.path.dirname(os.path.abspath(__file__)), "editor.properties")
 DEFAULT_GRID_SIZE = 10
 DEFAULT_ADD_TIMESTAMP = True
diff --git a/dasp.py b/dasp.py
index c605527..7774698 100644
--- a/dasp.py
+++ b/dasp.py
@@ -456,7 +456,7 @@ def _to_ack_more(seq_more, max_bytes):
 
 class _Packet:
     __slots__ = ("seq_num", "payload", "acked", "enqueued_time",
-                 "sent_time", "send_attempts", "next")
+                 "sent_time", "send_attempts", "send_retry", "next")
 
     def __init__(self):
         self.seq_num = 0
@@ -465,6 +465,7 @@ class _Packet:
         self.enqueued_time = 0.0
         self.sent_time = 0.0
         self.send_attempts = 1
+        self.send_retry = None      # seconds; None = the window's own interval
         self.next = None
 
 
@@ -506,8 +507,9 @@ class SendWindow:
             self._tail = None
             self._cond.notify_all()
 
-    def send(self, payload):
+    def send(self, payload, send_retry=None):
         p = _Packet()
+        p.send_retry = send_retry
         p.enqueued_time = _ticks()
         with self._cond:
             p.seq_num = self._seq_num & 0xFFFF
@@ -618,9 +620,15 @@ class SendWindow:
             p = self._head
             while p is not None:
                 if not p.acked:
-                    backoff_shift = min(p.send_attempts - 1, 32)
-                    interval = min(self.send_retry * (1 << backoff_shift),
-                                   self.max_retry_backoff)
+                    if p.send_retry is not None:
+                        # A request the device is slow to take -- a P-ION saving its
+                        # app, opening a file -- is resent at its own steady interval:
+                        # the 1 s default resends it while the device is still busy.
+                        interval = p.send_retry
+                    else:
+                        backoff_shift = min(p.send_attempts - 1, 32)
+                        interval = min(self.send_retry * (1 << backoff_shift),
+                                       self.max_retry_backoff)
                     if now - p.sent_time >= interval:
                         self._resend(p)
                     oldest = max(oldest, now - p.enqueued_time)
@@ -776,10 +784,11 @@ class DaspSession:
 
     # ── Send / Receive ──────────────────────────────────────────
 
-    def send(self, payload):
+    def send(self, payload, send_retry=None):
+        """Queues a datagram. send_retry (seconds) overrides the resend interval."""
         if self.is_closed:
             raise DaspException(f"Session closed: {self.close_cause}")
-        self.send_window.send(payload)
+        self.send_window.send(payload, send_retry)
 
     def receive(self, timeout=1.0):
         if self.is_closed:
diff --git a/device_session.py b/device_session.py
index 6995481..d6d00f9 100644
--- a/device_session.py
+++ b/device_session.py
@@ -10,6 +10,7 @@ import xml.etree.ElementTree as ET
 
 import app_state
 import schema
+import sox
 from sox import SoxClient, SoxComponent, TREE, CONFIG, RUNTIME, LINKS, ALL
 
 
@@ -43,7 +44,8 @@ class DeviceSession:
 
     def connect(self, host, port, user, password):
         """DASP connect → read schema → load root. Called from background thread."""
-        self.sox_client = SoxClient(host, int(port), user, password)
+        self.sox_client = SoxClient(host, int(port), user, password,
+                                    ideal_max=sox.IDEAL_MAX, abs_max=sox.ABS_MAX)
         self.sox_client.on_event = self._on_sox_event
         self.sox_client.checksum_resolver = schema.resolve_truncated_checksum
         self.sox_client.connect()
diff --git a/main.py b/main.py
index 1e3f5d1..a19f019 100644
--- a/main.py
+++ b/main.py
@@ -619,9 +619,9 @@ _APP_ACTIONS = ["save", "hibernate", "quit", "restart", "reboot"]
 def do_get_with_file():
     """App > Get with File: backs the device's app up to a zip in <Sedona home>/store/apps.
 
-    The zip carries the device's app.sab, so changes not yet saved on the device are
-    offered a save first. The transfer runs off the main thread behind a small progress
-    window.
+    The app is saved on the device before its app.sab is read, as Ontrol's Niagara
+    driver does, so unsaved changes are announced first and the backup can be called
+    off. The transfer runs off the main thread behind a small progress window.
     """
     ds = app_state.device_session
     if not app_state.live_mode or ds is None or not ds.is_connected:
@@ -631,21 +631,11 @@ def do_get_with_file():
         messagebox.showerror("Get with File", "The Sedona home folder is not set (Preferences).")
         return
 
-    if app_state.is_dirty:
-        answer = messagebox.askyesnocancel(
+    if app_state.is_dirty and not messagebox.askokcancel(
             "Unsaved Changes",
             "The app has changes that are not saved on the device yet." + NL + NL +
-            "Save the app on the device before getting it?" + NL +
-            "(No gets the app as it was last saved.)",
-        )
-        if answer is None:
-            return
-        if answer and not _invoke_app_action("save"):
-            messagebox.showerror(
-                "Get with File",
-                "The device did not save the app, so nothing was fetched. "
-                "The status bar says why.")
-            return
+            "Get with File saves the app on the device first, so they will be saved."):
+        return
 
     path = _ask_backup_path(ds)
     if not path:
@@ -683,6 +673,7 @@ def do_get_with_file():
             app_state.set_status(f"Get with File failed: {error}", warn=True)
             messagebox.showerror("Get with File", f"The backup failed:{NL}{NL}{error}")
             return
+        app_state.mark_clean()          # the app was saved on the device first
         _report_backup(result)
 
     def work():
diff --git a/sox.py b/sox.py
index 428a085..e7970a4 100644
--- a/sox.py
+++ b/sox.py
@@ -35,6 +35,18 @@ BUF_ID    = 7
 STR_ID    = 8
 
 
+# DASP resend intervals (seconds) for requests a device can be slow to take, as Ontrol's
+# Niagara driver sets them: a P-ION saving a large app takes 2-3+ s, and a file open can
+# take 10+ s on some devices. Resent every second instead, the device is sent copies
+# while it is still busy with the first.
+SAVE_SEND_RETRY = 5.0
+FILE_OPEN_SEND_RETRY = 15.0
+
+# The DASP packet sizes Ontrol's Niagara driver asks for in its hello.
+IDEAL_MAX = 256
+ABS_MAX = 256
+
+
 class SoxException(Exception):
     pass
 
@@ -464,6 +476,10 @@ class SoxClient:
         # Same 512-byte limit as read_schema: whatever is cut off is left
         # blank rather than failing the connect.
         platform_id = res.try_str() or ""
+        # Ontrol's message-length header is for Orion only; the Niagara driver never
+        # sends it to a P-ION or R-ION.
+        if self._session is not None:
+            self._session.include_message_len = platform_id.startswith("ontrol-orion")
         scode_flags = res.u1() if res.remaining > 0 else 0
         kit_versions = []
         for p in parts:
@@ -662,13 +678,13 @@ class SoxClient:
 
     # ── Invoke Action ───────────────────────────────────────────
 
-    def invoke(self, comp_id, slot_id, type_id=None, arg=None):
+    def invoke(self, comp_id, slot_id, type_id=None, arg=None, send_retry=None):
         req = _prepare_request(ord('i'))
         req.write_u2(comp_id)
         req.write_u1(slot_id)
         if arg is not None and type_id is not None:
             encode_value(req, type_id, arg)
-        res = self.request(req)
+        res = self.request(req, send_retry)
         res.check_response('I')
 
     # ── Add Component ───────────────────────────────────────────
@@ -934,7 +950,7 @@ class SoxClient:
             opened = closed = False
             try:
                 try:
-                    res = self.request(req)
+                    res = self.request(req, FILE_OPEN_SEND_RETRY)
                 except SoxException as e:
                     # A P-ION on firmware 1.32 never answers a file get -- it drops off
                     # the network for ~20 s, as a restart would -- even for a file it
@@ -986,16 +1002,21 @@ class SoxClient:
 
     # ── Networking ──────────────────────────────────────────────
 
-    def request(self, req):
-        results = self.requests([req])
+    def request(self, req, send_retry=None):
+        results = self.requests([req], send_retry)
         return results[0]
 
-    def requests(self, reqs):
+    def requests(self, reqs, send_retry=None):
+        """Sends the batch and waits for every reply.
+
+        send_retry (seconds) sets the DASP resend interval of these datagrams, for a
+        request the device is known to be slow to take.
+        """
         if self.is_closed:
             raise SoxException("SoxClient closed")
 
         if len(reqs) > 255:
-            return self._chunk_requests(reqs)
+            return self._chunk_requests(reqs, send_retry)
 
         with self._lock:
             for i, req in enumerate(reqs):
@@ -1006,7 +1027,7 @@ class SoxClient:
             self._req_event.clear()
 
             for req in reqs:
-                self._session.send(req.to_bytes())
+                self._session.send(req.to_bytes(), send_retry)
 
             deadline = time.monotonic() + 30.0
             while True:
@@ -1030,11 +1051,11 @@ class SoxClient:
             self._responses = None
             raise SoxException("Request timeout")
 
-    def _chunk_requests(self, reqs):
+    def _chunk_requests(self, reqs, send_retry=None):
         results = []
         for i in range(0, len(reqs), 255):
             chunk = reqs[i:i + 255]
-            results.extend(self.requests(chunk))
+            results.extend(self.requests(chunk, send_retry))
         return results
 
     # called by receiver thread