backend/routers/roster_edit.py

@@ -237,7 +237,7 @@ async def add_roster_unit(
         slm_measurement_range=slm_measurement_range if slm_measurement_range else None,
     )
 
-    # Auto-fill location data from modem if pairing and fields are empty
+    # Auto-fill data from modem if pairing and fields are empty
     if deployed_with_modem_id:
         modem = db.query(RosterUnit).filter(
             RosterUnit.id == deployed_with_modem_id,
@@ -252,6 +252,24 @@ async def add_roster_unit(
                 unit.coordinates = modem.coordinates
             if not unit.project_id and modem.project_id:
                 unit.project_id = modem.project_id
+            if not unit.note and modem.note:
+                unit.note = modem.note
+
+    # Bidirectional pairing sync for new units
+    if device_type in ("seismograph", "slm") and deployed_with_modem_id:
+        modem_to_update = db.query(RosterUnit).filter(
+            RosterUnit.id == deployed_with_modem_id,
+            RosterUnit.device_type == "modem"
+        ).first()
+        if modem_to_update:
+            # Clear old device's reference if modem was paired elsewhere
+            if modem_to_update.deployed_with_unit_id and modem_to_update.deployed_with_unit_id != id:
+                old_device = db.query(RosterUnit).filter(
+                    RosterUnit.id == modem_to_update.deployed_with_unit_id
+                ).first()
+                if old_device and old_device.deployed_with_modem_id == deployed_with_modem_id:
+                    old_device.deployed_with_modem_id = None
+            modem_to_update.deployed_with_unit_id = id
 
     db.add(unit)
     db.commit()
@@ -564,7 +582,7 @@ async def edit_roster_unit(
     unit.next_calibration_due = next_cal_date
     unit.deployed_with_modem_id = deployed_with_modem_id if deployed_with_modem_id else None
 
-    # Auto-fill location data from modem if pairing and fields are empty
+    # Auto-fill data from modem if pairing and fields are empty
     if deployed_with_modem_id:
         modem = db.query(RosterUnit).filter(
             RosterUnit.id == deployed_with_modem_id,
@@ -580,6 +598,8 @@ async def edit_roster_unit(
                 unit.coordinates = modem.coordinates
             if not unit.project_id and modem.project_id:
                 unit.project_id = modem.project_id
+            if not unit.note and modem.note:
+                unit.note = modem.note
 
     # Modem-specific fields
     unit.ip_address = ip_address if ip_address else None
@@ -598,6 +618,51 @@ async def edit_roster_unit(
     unit.slm_time_weighting = slm_time_weighting if slm_time_weighting else None
     unit.slm_measurement_range = slm_measurement_range if slm_measurement_range else None
 
+    # Bidirectional pairing sync
+    new_modem_id = deployed_with_modem_id if deployed_with_modem_id else None
+    new_unit_pair_id = deployed_with_unit_id if deployed_with_unit_id else None
+
+    # When a device (seismograph/SLM) sets deployed_with_modem_id, update modem's deployed_with_unit_id
+    if device_type in ("seismograph", "slm"):
+        # Clear old modem's reference if modem changed
+        old_modem_id = db.query(RosterUnit.deployed_with_modem_id).filter(
+            RosterUnit.id == unit_id
+        ).scalar()
+        # old_modem_id is already the new value at this point since we set it above,
+        # but we need to check the *previous* modem. We already set it, so check if
+        # there's a modem pointing to us that we're no longer paired with.
+        if new_modem_id:
+            modem_to_update = db.query(RosterUnit).filter(
+                RosterUnit.id == new_modem_id,
+                RosterUnit.device_type == "modem"
+            ).first()
+            if modem_to_update and modem_to_update.deployed_with_unit_id != unit_id:
+                # Clear old device's reference to this modem if modem was paired elsewhere
+                if modem_to_update.deployed_with_unit_id:
+                    old_device = db.query(RosterUnit).filter(
+                        RosterUnit.id == modem_to_update.deployed_with_unit_id
+                    ).first()
+                    if old_device and old_device.deployed_with_modem_id == new_modem_id:
+                        old_device.deployed_with_modem_id = None
+                modem_to_update.deployed_with_unit_id = unit_id
+
+    # When a modem sets deployed_with_unit_id, update device's deployed_with_modem_id
+    if device_type == "modem":
+        if new_unit_pair_id:
+            device_to_update = db.query(RosterUnit).filter(
+                RosterUnit.id == new_unit_pair_id,
+                RosterUnit.device_type.in_(["seismograph", "slm"])
+            ).first()
+            if device_to_update and device_to_update.deployed_with_modem_id != unit_id:
+                # Clear old modem's reference to this device if device was paired elsewhere
+                if device_to_update.deployed_with_modem_id:
+                    old_modem = db.query(RosterUnit).filter(
+                        RosterUnit.id == device_to_update.deployed_with_modem_id
+                    ).first()
+                    if old_modem and old_modem.deployed_with_unit_id == new_unit_pair_id:
+                        old_modem.deployed_with_unit_id = None
+                device_to_update.deployed_with_modem_id = unit_id
+
     # Record history entries for changed fields
     if old_note != note:
         record_history(db, unit_id, "note_change", "note", old_note, note, "manual")

backend/services/slmm_client.py

@@ -112,6 +112,69 @@ class SLMMClient:
             error_msg = str(e) if str(e) else type(e).__name__
             raise SLMMClientError(f"Unexpected error: {error_msg}")
 
+    async def _download_request(
+        self,
+        endpoint: str,
+        data: Dict[str, Any],
+        unit_id: str,
+    ) -> Dict[str, Any]:
+        """
+        Make a download request to SLMM that returns binary file content (not JSON).
+
+        Saves the file locally and returns metadata about the download.
+        """
+        url = f"{self.api_base}{endpoint}"
+
+        try:
+            async with httpx.AsyncClient(timeout=httpx.Timeout(300.0)) as client:
+                response = await client.post(url, json=data)
+                response.raise_for_status()
+
+                # Determine filename from Content-Disposition header or generate one
+                content_disp = response.headers.get("content-disposition", "")
+                filename = None
+                if "filename=" in content_disp:
+                    filename = content_disp.split("filename=")[-1].strip('" ')
+
+                if not filename:
+                    remote_path = data.get("remote_path", "download")
+                    base = os.path.basename(remote_path.rstrip("/"))
+                    filename = f"{base}.zip" if not base.endswith(".zip") else base
+
+                # Save to local downloads directory
+                download_dir = os.path.join("data", "downloads", unit_id)
+                os.makedirs(download_dir, exist_ok=True)
+                local_path = os.path.join(download_dir, filename)
+
+                with open(local_path, "wb") as f:
+                    f.write(response.content)
+
+                return {
+                    "success": True,
+                    "local_path": local_path,
+                    "filename": filename,
+                    "size_bytes": len(response.content),
+                }
+
+        except httpx.ConnectError as e:
+            raise SLMMConnectionError(
+                f"Cannot connect to SLMM backend at {self.base_url}. "
+                f"Is SLMM running? Error: {str(e)}"
+            )
+        except httpx.HTTPStatusError as e:
+            error_detail = "Unknown error"
+            try:
+                error_data = e.response.json()
+                error_detail = error_data.get("detail", str(error_data))
+            except Exception:
+                error_detail = e.response.text or str(e)
+            raise SLMMDeviceError(f"SLMM download failed: {error_detail}")
+        except (SLMMConnectionError, SLMMDeviceError):
+            raise
+        except Exception as e:
+            error_msg = str(e) if str(e) else type(e).__name__
+            raise SLMMClientError(f"Download error: {error_msg}")
+
     # ========================================================================
     # Unit Management
     # ========================================================================
@@ -537,10 +600,13 @@ class SLMMClient:
             remote_path: Path on device to download (e.g., "/NL43_DATA/measurement.wav")
 
         Returns:
-            Binary file content (as response)
+            Dict with local_path, filename, size_bytes
         """
-        data = {"remote_path": remote_path}
-        return await self._request("POST", f"/{unit_id}/ftp/download", data=data)
+        return await self._download_request(
+            f"/{unit_id}/ftp/download",
+            {"remote_path": remote_path},
+            unit_id,
+        )
 
     async def download_folder(
         self,
@@ -557,10 +623,13 @@ class SLMMClient:
             remote_path: Folder path on device to download (e.g., "/NL43_DATA/Auto_0000")
 
         Returns:
-            Dict with local_path, folder_name, file_count, zip_size_bytes
+            Dict with local_path, folder_name, size_bytes
         """
-        data = {"remote_path": remote_path}
-        return await self._request("POST", f"/{unit_id}/ftp/download-folder", data=data)
+        return await self._download_request(
+            f"/{unit_id}/ftp/download-folder",
+            {"remote_path": remote_path},
+            unit_id,
+        )
 
     async def download_current_measurement(
         self,

templates/partials/projects/schedule_oneoff.html

@@ -36,8 +36,7 @@
         <input type="datetime-local"
                name="start_datetime"
                id="oneoff_start_datetime"
-               class="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-seismo-orange focus:border-seismo-orange"
-               required>
+               class="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-seismo-orange focus:border-seismo-orange">
         <p class="text-xs text-gray-400 dark:text-gray-500 mt-2">
             Must be in the future
         </p>
@@ -51,8 +50,7 @@
         <input type="datetime-local"
                name="end_datetime"
                id="oneoff_end_datetime"
-               class="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-seismo-orange focus:border-seismo-orange"
-               required>
+               class="w-full px-3 py-2 border border-gray-300 dark:border-gray-600 rounded-lg bg-white dark:bg-gray-700 text-gray-900 dark:text-white focus:ring-seismo-orange focus:border-seismo-orange">
     </div>
 
     <!-- Duration preview -->