diff --git a/Cargo.lock b/Cargo.lock
index ccac53c..c8dd245 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -30,6 +30,8 @@ version = "0.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5351dcebb14b579ccab05f288596b2ae097005be7ee50a7c3d4ca9d0d5a66f6a"
 dependencies = [
+ "enumn",
+ "serde",
  "uuid",
 ]
 
@@ -225,6 +227,7 @@ dependencies = [
  "cfg-if",
  "getrandom 0.3.4",
  "once_cell",
+ "serde",
  "version_check",
  "zerocopy",
 ]
@@ -1449,6 +1452,7 @@ checksum = "55f6cc0cb3b84a21232c468db972ebcddd34decbf1ff02cdebffd807c13bbd81"
 dependencies = [
  "bytemuck",
  "emath",
+ "serde",
 ]
 
 [[package]]
@@ -1466,6 +1470,7 @@ dependencies = [
  "egui_glow",
  "glutin",
  "glutin-winit",
+ "home",
  "image",
  "js-sys",
  "log",
@@ -1477,6 +1482,8 @@ dependencies = [
  "pollster",
  "profiling",
  "raw-window-handle",
+ "ron",
+ "serde",
  "static_assertions",
  "wasm-bindgen",
  "wasm-bindgen-futures",
@@ -1501,6 +1508,8 @@ dependencies = [
  "log",
  "nohash-hasher",
  "profiling",
+ "ron",
+ "serde",
  "smallvec",
  "unicode-segmentation",
 ]
@@ -1541,6 +1550,7 @@ dependencies = [
  "objc2-ui-kit 0.3.2",
  "profiling",
  "raw-window-handle",
+ "serde",
  "smithay-clipboard",
  "web-time",
  "webbrowser",
@@ -1597,6 +1607,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a74fbbf7501c430b89df62d102b6bfa02162faaf3e155512c677c9d20f5708d1"
 dependencies = [
  "bytemuck",
+ "serde",
 ]
 
 [[package]]
@@ -1635,6 +1646,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "enumn"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f9ed6b3789237c8a0c1c505af1c7eb2c560df6186f01b098c3a1064ea532f38"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "epaint"
 version = "0.34.2"
@@ -1652,6 +1674,7 @@ dependencies = [
  "parking_lot",
  "profiling",
  "self_cell",
+ "serde",
  "skrifa",
  "smallvec",
  "vello_cpu",
@@ -1868,6 +1891,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5b38ad915f6dadd993ced50848a8291a543bd41ca62bc10740d5e64e2ab4cfd7"
 dependencies = [
  "bytemuck",
+ "serde",
 ]
 
 [[package]]
@@ -2360,6 +2384,15 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfa686283ad6dd069f105e5ab091b04c62850d3e4cf5d67debad1933f55023df"
 
+[[package]]
+name = "home"
+version = "0.5.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc627f471c528ff0c4a49e1d5e60450c8f6461dd6d10ba9dcd3a61d3dff7728d"
+dependencies = [
+ "windows-sys 0.61.2",
+]
+
 [[package]]
 name = "htmlparser"
 version = "0.2.1"
@@ -4819,6 +4852,20 @@ dependencies = [
  "bytemuck",
 ]
 
+[[package]]
+name = "ron"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4147b952f3f819eca0e99527022f7d6a8d05f111aeb0a62960c74eb283bec8fc"
+dependencies = [
+ "bitflags 2.11.1",
+ "once_cell",
+ "serde",
+ "serde_derive",
+ "typeid",
+ "unicode-ident",
+]
+
 [[package]]
 name = "rowan"
 version = "0.16.1"
@@ -5216,6 +5263,9 @@ name = "smallvec"
 version = "1.15.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "67b1b7a3b5fe4f1376887184045fcf45c69e92af734b7aaddc05fb777b6fbd03"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "smithay-client-toolkit"
@@ -5461,6 +5511,7 @@ dependencies = [
  "egui_plot",
  "fuzzy-matcher",
  "libsvld",
+ "rfd",
 ]
 
 [[package]]
@@ -5839,6 +5890,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "typeid"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bc7d623258602320d5c55d1bc22793b57daff0ec7efc270ea7d55ce1d5f5471c"
+
 [[package]]
 name = "typenum"
 version = "1.20.0"
diff --git a/svldplotter/Cargo.toml b/svldplotter/Cargo.toml
index a3d6835..0e2cf6f 100644
--- a/svldplotter/Cargo.toml
+++ b/svldplotter/Cargo.toml
@@ -12,8 +12,12 @@ bench = false
 libsvld = { path = "../libsvld" }
 can-dbc = "9.1"
 
-eframe = "0.34"
+eframe = {
+       version = "0.34",
+       features = ["persistence"]
+}
 egui = "0.34"
 egui_plot = "0.35"
 egui_ltreeview = "0.7"
 fuzzy-matcher = "0.3"
+rfd = "0.17"
diff --git a/svldplotter/src/main.rs b/svldplotter/src/main.rs
index 4498e30..1d2686f 100644
--- a/svldplotter/src/main.rs
+++ b/svldplotter/src/main.rs
@@ -3,7 +3,13 @@ mod plot_list;
 mod signal;
 mod tree;
 
-use std::{fs, path::Path};
+use std::{
+    collections::HashMap,
+    fs,
+    path::PathBuf,
+    sync::{mpsc::{channel, Receiver}, Arc},
+    thread,
+};
 
 use can_dbc::Dbc;
 use eframe::egui;
@@ -20,50 +26,171 @@ use crate::tree::{build_tree, decode_signal_node_id, show_dbc_tree, MsgNode};
 fn main() {
     let native_options = eframe::NativeOptions::default();
     eframe::run_native(
-        "My egui App",
+        "svldplotter",
         native_options,
-        Box::new(|cc| Ok(Box::new(MyEguiApp::new(cc)))),
+        Box::new(|cc| {
+            let mut app = MyEguiApp::default();
+            // Optional CLI quick-load: `svldplotter [DBC [ASC]]`. Both args
+            // are optional and intended for dev iteration.
+            let args: Vec<String> = std::env::args().collect();
+            if let Some(dbc) = args.get(1) {
+                app.load_dbc(PathBuf::from(dbc));
+            }
+            if let Some(asc) = args.get(2) {
+                app.asc_paths.push(PathBuf::from(asc));
+                app.set_active_asc(app.asc_paths.len() - 1, Some(&cc.egui_ctx));
+            }
+            Ok(Box::new(app))
+        }),
     )
     .unwrap();
 }
 
+#[derive(Default, PartialEq, Eq)]
+enum LeftTab {
+    #[default]
+    Signals,
+    Files,
+}
+
+struct DecodeJob {
+    asc_index: usize,
+    asc_path: PathBuf,
+    receiver: Receiver<Arc<DecodeResult>>,
+}
+
+#[derive(Default)]
 struct MyEguiApp {
-    data: DecodeResult,
+    dbc: Option<Arc<Dbc>>,
+    dbc_path: Option<PathBuf>,
+    asc_paths: Vec<PathBuf>,
+    active_asc: Option<usize>,
+    data: Option<Arc<DecodeResult>>,
+    decode_cache: HashMap<PathBuf, Arc<DecodeResult>>,
+    pending: Option<DecodeJob>,
     tree: Vec<MsgNode>,
     filter: String,
     plots: Vec<PlotGroup>,
     next_plot_id: u64,
     cursor_x: Option<f64>,
+    left_tab: LeftTab,
 }
 
 impl MyEguiApp {
-    fn new(_cc: &eframe::CreationContext<'_>) -> Self {
-        let args: Vec<_> = std::env::args().collect();
-
-        let dbc_text =
-            fs::read_to_string(Path::new(&args[1])).expect("Unable to read input file");
-        let dbc = Dbc::try_from(dbc_text.as_str()).expect("Failed to parse dbc file");
-
-        let asc_path = Path::new(&args[2]);
-        let data = libsvld::decode(&dbc, asc_path);
-        let tree = build_tree(&dbc, &data);
-
-        Self {
-            data,
-            tree,
-            filter: String::new(),
-            plots: Vec::new(),
-            next_plot_id: 1,
-            cursor_x: None,
+    fn load_dbc(&mut self, path: PathBuf) {
+        let Ok(text) = fs::read_to_string(&path) else {
+            return;
+        };
+        let Ok(dbc) = Dbc::try_from(text.as_str()) else {
+            return;
+        };
+        self.dbc = Some(Arc::new(dbc));
+        self.dbc_path = Some(path);
+        // DBC change invalidates the decode cache.
+        self.decode_cache.clear();
+        self.pending = None;
+        self.data = None;
+        self.tree.clear();
+        if let Some(idx) = self.active_asc {
+            self.start_or_use_cached(idx, None);
         }
     }
 
+    fn add_asc(&mut self, path: PathBuf) {
+        self.asc_paths.push(path);
+        if self.active_asc.is_none() {
+            self.set_active_asc(self.asc_paths.len() - 1, None);
+        }
+    }
+
+    /// Switch to a given ASC. Use the cached DecodeResult if present;
+    /// otherwise spawn a background decode and show progress via the
+    /// `pending` job.
+    fn set_active_asc(&mut self, idx: usize, ctx: Option<&egui::Context>) {
+        if idx >= self.asc_paths.len() {
+            return;
+        }
+        self.active_asc = Some(idx);
+        self.start_or_use_cached(idx, ctx);
+    }
+
+    fn start_or_use_cached(&mut self, idx: usize, ctx: Option<&egui::Context>) {
+        let Some(dbc) = self.dbc.clone() else {
+            return;
+        };
+        let path = self.asc_paths[idx].clone();
+        if self.decode_cache.contains_key(&path) {
+            self.activate_decoded(idx);
+            return;
+        }
+        let (tx, rx) = channel();
+        let dbc_for_thread = dbc;
+        let path_for_thread = path.clone();
+        let ctx_for_thread = ctx.cloned();
+        thread::spawn(move || {
+            let result = libsvld::decode(&dbc_for_thread, &path_for_thread);
+            let _ = tx.send(Arc::new(result));
+            if let Some(ctx) = ctx_for_thread {
+                ctx.request_repaint();
+            }
+        });
+        self.pending = Some(DecodeJob {
+            asc_index: idx,
+            asc_path: path,
+            receiver: rx,
+        });
+    }
+
+    /// Pull a finished decode out of `pending` and install it.
+    fn poll_pending(&mut self) {
+        let Some(job) = self.pending.as_ref() else {
+            return;
+        };
+        let Ok(result) = job.receiver.try_recv() else {
+            return;
+        };
+        let asc_index = job.asc_index;
+        let asc_path = job.asc_path.clone();
+        self.pending = None;
+        self.decode_cache.insert(asc_path, result);
+        if self.active_asc == Some(asc_index) {
+            self.activate_decoded(asc_index);
+        }
+    }
+
+    /// Point `self.data`/`self.tree` at the cached result for `idx` and
+    /// re-resolve every plotted signal against the new data.
+    fn activate_decoded(&mut self, idx: usize) {
+        let Some(dbc) = self.dbc.as_ref() else {
+            return;
+        };
+        let path = &self.asc_paths[idx];
+        let Some(data) = self.decode_cache.get(path).cloned() else {
+            return;
+        };
+        self.tree = build_tree(dbc, &data);
+        // Re-resolve plotted signals so existing plots survive an ASC switch.
+        for plot in &mut self.plots {
+            for sig in &mut plot.signals {
+                if let Some((msg_id, sig_idx)) = decode_signal_node_id(sig.id) {
+                    if let Some(new_sig) = compute_signal(&data, msg_id, sig_idx, sig.id) {
+                        *sig = new_sig;
+                    }
+                }
+            }
+        }
+        self.data = Some(data);
+    }
+
     fn handle_dbc_toggles(&mut self, toggles: Vec<u64>) {
+        let Some(data) = self.data.clone() else {
+            return;
+        };
         for id in toggles {
             if contains_signal(&self.plots, id) {
                 remove_signal(&mut self.plots, id);
             } else if let Some((msg_id, sig_idx)) = decode_signal_node_id(id) {
-                if let Some(sig) = compute_signal(&self.data, msg_id, sig_idx, id) {
+                if let Some(sig) = compute_signal(&data, msg_id, sig_idx, id) {
                     add_signal_auto(&mut self.plots, &mut self.next_plot_id, sig);
                 }
             }
@@ -82,8 +209,64 @@ impl MyEguiApp {
     }
 }
 
+enum FilesAction {
+    LoadDbc(PathBuf),
+    AddAsc(PathBuf),
+    SetActive(usize),
+}
+
+fn show_files_tab(
+    ui: &mut egui::Ui,
+    dbc_path: Option<&PathBuf>,
+    asc_paths: &[PathBuf],
+    active: Option<usize>,
+) -> Vec<FilesAction> {
+    let mut actions = Vec::new();
+    ui.horizontal(|ui| {
+        if ui.button("Load DBC").clicked() {
+            if let Some(p) = rfd::FileDialog::new()
+                .add_filter("DBC files", &["dbc"])
+                .pick_file()
+            {
+                actions.push(FilesAction::LoadDbc(p));
+            }
+        }
+        let label = dbc_path
+            .map(|p| p.file_name().map(|s| s.to_string_lossy().into_owned()).unwrap_or_default())
+            .unwrap_or_else(|| "(none)".to_string());
+        ui.label(label);
+    });
+    ui.separator();
+    ui.horizontal(|ui| {
+        if ui.button("Add ASC").clicked() {
+            if let Some(p) = rfd::FileDialog::new()
+                .add_filter("ASC files", &["asc"])
+                .pick_file()
+            {
+                actions.push(FilesAction::AddAsc(p));
+            }
+        }
+        ui.label(format!("{} file(s)", asc_paths.len()));
+    });
+    egui::ScrollArea::vertical().show(ui, |ui| {
+        for (i, path) in asc_paths.iter().enumerate() {
+            let name = path
+                .file_name()
+                .map(|s| s.to_string_lossy().into_owned())
+                .unwrap_or_else(|| path.display().to_string());
+            if ui.selectable_label(active == Some(i), name).clicked() {
+                actions.push(FilesAction::SetActive(i));
+            }
+        }
+    });
+    actions
+}
+
 impl eframe::App for MyEguiApp {
     fn ui(&mut self, ui: &mut egui::Ui, _frame: &mut eframe::Frame) {
+        self.poll_pending();
+
+        let ctx = ui.ctx().clone();
         egui::Panel::left(egui::Id::new("LeftPanel"))
             .resizable(true)
             .show_inside(ui, |ui| {
@@ -92,13 +275,66 @@ impl eframe::App for MyEguiApp {
                     .default_size(220.0)
                     .show_inside(ui, |ui| show_plot_list(ui, &self.plots))
                     .inner;
-                let toggles = egui::CentralPanel::default()
-                    .show_inside(ui, |ui| show_dbc_tree(ui, &mut self.filter, &self.tree))
+                let (toggles, files_actions) = egui::CentralPanel::default()
+                    .show_inside(ui, |ui| {
+                        ui.horizontal(|ui| {
+                            ui.selectable_value(
+                                &mut self.left_tab,
+                                LeftTab::Signals,
+                                "Signals",
+                            );
+                            ui.selectable_value(
+                                &mut self.left_tab,
+                                LeftTab::Files,
+                                "Files",
+                            );
+                        });
+                        ui.separator();
+                        match self.left_tab {
+                            LeftTab::Signals => (
+                                show_dbc_tree(ui, &mut self.filter, &self.tree),
+                                Vec::new(),
+                            ),
+                            LeftTab::Files => (
+                                Vec::new(),
+                                show_files_tab(
+                                    ui,
+                                    self.dbc_path.as_ref(),
+                                    &self.asc_paths,
+                                    self.active_asc,
+                                ),
+                            ),
+                        }
+                    })
                     .inner;
                 self.handle_dbc_toggles(toggles);
                 self.handle_plot_actions(plot_actions);
+                for action in files_actions {
+                    match action {
+                        FilesAction::LoadDbc(p) => self.load_dbc(p),
+                        FilesAction::AddAsc(p) => self.add_asc(p),
+                        FilesAction::SetActive(i) => self.set_active_asc(i, Some(&ctx)),
+                    }
+                }
             });
         show_plot_panel(ui, &self.plots, &mut self.cursor_x);
+
+        if let Some(job) = self.pending.as_ref() {
+            let name = job
+                .asc_path
+                .file_name()
+                .map(|s| s.to_string_lossy().into_owned())
+                .unwrap_or_else(|| job.asc_path.display().to_string());
+            egui::Modal::new(egui::Id::new("DecodingModal")).show(&ctx, |ui| {
+                ui.set_min_width(280.0);
+                ui.vertical_centered(|ui| {
+                    ui.heading("Decoding...");
+                    ui.add_space(6.0);
+                    ui.label(name);
+                    ui.add_space(6.0);
+                    ui.spinner();
+                });
+            });
+        }
     }
 }
-