diff --git a/desktop/src-tauri/src/commands.rs b/desktop/src-tauri/src/commands.rs
new file mode 100644
index 0000000..d020dad
--- /dev/null
+++ b/desktop/src-tauri/src/commands.rs
@@ -0,0 +1,374 @@
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use libnspire::dir::EntryType;
+use libnspire::PID_CX2;
+use serde::Serialize;
+use tauri::{Emitter, Runtime, WebviewWindow};
+
+use crate::device::{
+  add_device, get_open_dev, AddDevice, DevId, DeviceState, FileInfo, ProgressUpdate, DEVICES,
+};
+use crate::error::SerializedError;
+
+/// If the device vanished mid-operation, drop it from the registry and tell
+/// the frontend, then pass the original result through unchanged.
+fn err_wrap<T, R: Runtime>(
+  res: Result<T, libnspire::Error>,
+  dev: DevId,
+  window: &WebviewWindow<R>,
+) -> Result<T, libnspire::Error> {
+  if let Err(libnspire::Error::NoDevice) = res {
+    DEVICES
+      .write()
+      .unwrap()
+      .remove(&(dev.bus_number, dev.address));
+    if let Err(msg) = window.emit("removeDevice", dev) {
+      eprintln!("{}", msg);
+    };
+  }
+  res
+}
+
+/// Emits a `progress` event on every 6th callback, and always on completion,
+/// to avoid flooding the IPC channel during large transfers.
+fn progress_sender<R: Runtime>(
+  window: &WebviewWindow<R>,
+  dev: DevId,
+  total: usize,
+) -> impl FnMut(usize) + '_ {
+  let mut i = 0;
+  move |remaining| {
+    if i > 5 {
+      i = 0;
+    }
+    if i == 0 || remaining == 0 {
+      if let Err(msg) = window.emit(
+        "progress",
+        ProgressUpdate {
+          dev,
+          remaining,
+          total,
+        },
+      ) {
+        eprintln!("{}", msg);
+      };
+    }
+    i += 1;
+  }
+}
+
+#[tauri::command]
+pub fn enumerate<R: Runtime>(window: WebviewWindow<R>) -> Result<Vec<AddDevice>, SerializedError> {
+  let devices: Vec<_> = rusb::devices()?.iter().collect();
+  let mut map = DEVICES.write().unwrap();
+
+  // Replaces hashbrown's `drain_filter`: collect the keys of devices that are
+  // no longer present on the bus, then remove them. std HashMap has no stable
+  // drain-with-predicate, and this is clearer than the original anyway.
+  let stale: Vec<(u8, u8)> = map
+    .keys()
+    .filter(|k| {
+      devices
+        .iter()
+        .all(|d| d.bus_number() != k.0 || d.address() != k.1)
+    })
+    .copied()
+    .collect();
+
+  for key in stale {
+    map.remove(&key);
+    if let Err(msg) = window.emit(
+      "removeDevice",
+      DevId {
+        bus_number: key.0,
+        address: key.1,
+      },
+    ) {
+      eprintln!("{}", msg);
+    }
+  }
+
+  let filtered: Vec<_> = devices
+    .into_iter()
+    .filter(|d| !map.contains_key(&(d.bus_number(), d.address())))
+    .collect();
+
+  Ok(
+    filtered
+      .into_iter()
+      .filter_map(|dev| add_device(Arc::new(dev)).ok())
+      .map(|dev| {
+        let msg = AddDevice {
+          dev: DevId {
+            bus_number: (dev.0).0,
+            address: (dev.0).1,
+          },
+          name: (dev.1).name.clone(),
+          is_cx_ii: (dev.1)
+            .device
+            .device_descriptor()
+            .map(|d| d.product_id() == PID_CX2)
+            .unwrap_or(false),
+          needs_drivers: (dev.1).needs_drivers,
+        };
+        map.insert(dev.0, dev.1);
+        msg
+      })
+      .collect(),
+  )
+}
+
+#[tauri::command]
+pub fn open_device(bus_number: u8, address: u8) -> Result<impl Serialize, SerializedError> {
+  let device = if let Some(dev) = DEVICES.read().unwrap().get(&(bus_number, address)) {
+    if !matches!(dev.state, DeviceState::Closed) {
+      return Err("Already open".into());
+    };
+    dev.device.clone()
+  } else {
+    return Err("Failed to find device".into());
+  };
+  let handle = libnspire::Handle::new(device.open()?)?;
+  let info = handle.info()?;
+  {
+    let mut guard = DEVICES.write().unwrap();
+    let device = guard
+      .get_mut(&(bus_number, address))
+      .ok_or_else(|| anyhow::anyhow!("Device lost"))?;
+    device.state = DeviceState::Open(Arc::new(std::sync::Mutex::new(handle)), info.clone());
+  }
+  Ok(info)
+}
+
+#[tauri::command]
+pub fn close_device(bus_number: u8, address: u8) -> Result<impl Serialize, SerializedError> {
+  let mut guard = DEVICES.write().unwrap();
+  let device = guard
+    .get_mut(&(bus_number, address))
+    .ok_or_else(|| anyhow::anyhow!("Device lost"))?;
+  device.state = DeviceState::Closed;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn update_device<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  let info = err_wrap(handle.info(), dev, &window)?;
+  Ok(info)
+}
+
+#[tauri::command]
+pub fn list_dir<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  let dir = err_wrap(handle.list_dir(&path), dev, &window)?;
+
+  Ok(
+    dir
+      .iter()
+      .map(|file| FileInfo {
+        path: file.name().to_string_lossy().to_string(),
+        is_dir: file.entry_type() == EntryType::Directory,
+        date: file.date(),
+        size: file.size(),
+      })
+      .collect::<Vec<_>>(),
+  )
+}
+
+#[tauri::command]
+pub fn download_file<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: (String, u64),
+  dest: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let (file, size) = path;
+  let dest = PathBuf::from(dest);
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  let mut buf = vec![0; size as usize];
+  err_wrap(
+    handle.read_file(
+      &file,
+      &mut buf,
+      &mut progress_sender(&window, dev, size as usize),
+    ),
+    dev,
+    &window,
+  )?;
+  if let Some(name) = file.split('/').last() {
+    File::create(dest.join(name))?.write_all(&buf)?;
+  }
+  Ok(())
+}
+
+#[tauri::command]
+pub fn upload_file<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: String,
+  src: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let file = PathBuf::from(src);
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  let mut buf = vec![];
+  File::open(&file)?.read_to_end(&mut buf)?;
+  let name = file
+    .file_name()
+    .ok_or_else(|| anyhow::anyhow!("Failed to get file name"))?
+    .to_string_lossy()
+    .to_string();
+  err_wrap(
+    handle.write_file(
+      &format!("{}/{}", path, name),
+      &buf,
+      &mut progress_sender(&window, dev, buf.len()),
+    ),
+    dev,
+    &window,
+  )?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn upload_os<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  src: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  let mut buf = vec![];
+  File::open(&src)?.read_to_end(&mut buf)?;
+  err_wrap(
+    handle.send_os(&buf, &mut progress_sender(&window, dev, buf.len())),
+    dev,
+    &window,
+  )?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn delete_file<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  err_wrap(handle.delete_file(&path), dev, &window)?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn delete_dir<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  err_wrap(handle.delete_dir(&path), dev, &window)?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn create_nspire_dir<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  path: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  err_wrap(handle.create_dir(&path), dev, &window)?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn move_file<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  src: String,
+  dest: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  err_wrap(handle.move_file(&src, &dest), dev, &window)?;
+  Ok(())
+}
+
+#[tauri::command]
+pub fn copy<R: Runtime>(
+  bus_number: u8,
+  address: u8,
+  src: String,
+  dest: String,
+  window: WebviewWindow<R>,
+) -> Result<impl Serialize, SerializedError> {
+  let dev = DevId {
+    bus_number,
+    address,
+  };
+  let handle = get_open_dev(&dev)?;
+  let handle = handle.lock().unwrap();
+  err_wrap(handle.copy_file(&src, &dest), dev, &window)?;
+  Ok(())
+}
diff --git a/desktop/src-tauri/src/device.rs b/desktop/src-tauri/src/device.rs
index d3008c7..8e51560 100644
--- a/desktop/src-tauri/src/device.rs
+++ b/desktop/src-tauri/src/device.rs
@@ -43,7 +43,7 @@ pub struct AddDevice {
   pub needs_drivers: bool,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug, Clone, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct ProgressUpdate {
   #[serde(flatten)]
diff --git a/desktop/src-tauri/src/main.rs b/desktop/src-tauri/src/main.rs
index 7319f97..38c0477 100644
--- a/desktop/src-tauri/src/main.rs
+++ b/desktop/src-tauri/src/main.rs
@@ -1,5 +1,6 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
+mod commands;
 mod device;
 mod error;