src-tauri/Cargo.toml

@@ -23,6 +23,8 @@ serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 tokio = { version = "1", features = ["process", "io-util", "sync", "time", "rt-multi-thread", "macros"] }
 tauri-plugin-dialog = "2.7.2"
+tauri-plugin-log = "2"
+log = "0.4"
 base64 = "0.22"
 image = { version = "0.25", default-features = false, features = ["png", "tiff"] }
 

src-tauri/src/commands.rs

@@ -121,6 +121,51 @@ pub fn get_default_working_dir(app: AppHandle) -> Result<String, String> {
     resolve_safe_cwd(&app, "")
 }
 
+#[tauri::command]
+pub fn get_log_path(app: AppHandle) -> Result<String, String> {
+    let log_dir = app
+        .path()
+        .app_log_dir()
+        .map_err(|e| format!("Failed to resolve log dir: {}", e))?;
+    Ok(log_dir.join("iccery.log").to_string_lossy().to_string())
+}
+
+#[tauri::command]
+pub fn open_log_dir(app: AppHandle) -> Result<(), String> {
+    let log_dir = app
+        .path()
+        .app_log_dir()
+        .map_err(|e| format!("Failed to resolve log dir: {}", e))?;
+    
+    std::fs::create_dir_all(&log_dir).map_err(|e| format!("Failed to create log dir: {}", e))?;
+
+    #[cfg(target_os = "windows")]
+    {
+        std::process::Command::new("explorer")
+            .arg(&log_dir)
+            .spawn()
+            .map_err(|e| format!("Failed to open log folder: {}", e))?;
+    }
+
+    #[cfg(target_os = "macos")]
+    {
+        std::process::Command::new("open")
+            .arg(&log_dir)
+            .spawn()
+            .map_err(|e| format!("Failed to open log folder: {}", e))?;
+    }
+
+    #[cfg(target_os = "linux")]
+    {
+        std::process::Command::new("xdg-open")
+            .arg(&log_dir)
+            .spawn()
+            .map_err(|e| format!("Failed to open log folder: {}", e))?;
+    }
+
+    Ok(())
+}
+
 #[tauri::command]
 pub async fn select_target_file(
     app: AppHandle,

src-tauri/src/lib.rs

@@ -8,12 +8,31 @@ mod settings;
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_dialog::init())
+        .plugin(
+            tauri_plugin_log::Builder::default()
+                .targets([
+                    tauri_plugin_log::Target::new(tauri_plugin_log::TargetKind::LogDir {
+                        file_name: Some("iccery".into()),
+                    }),
+                    tauri_plugin_log::Target::new(tauri_plugin_log::TargetKind::Stdout),
+                    tauri_plugin_log::Target::new(tauri_plugin_log::TargetKind::Webview),
+                ])
+                .level(if cfg!(debug_assertions) {
+                    log::LevelFilter::Debug
+                } else {
+                    log::LevelFilter::Info
+                })
+                .rotation_strategy(tauri_plugin_log::RotationStrategy::KeepOne)
+                .build(),
+        )
         .manage(process_manager::ProcessManager::new())
         .manage(print::PrinterDevModeStore::new())
         .invoke_handler(tauri::generate_handler![
             commands::spawn_process,
             commands::get_app_info,
             commands::get_default_working_dir,
+            commands::get_log_path,
+            commands::open_log_dir,
             commands::select_target_file,
             commands::select_directory,
             commands::send_stdin,

src-tauri/src/process_manager.rs

@@ -51,6 +51,7 @@ impl ProcessManager {
             command.creation_flags(CREATE_NO_WINDOW);
         }
 
+        log::info!(target: "subprocess", "Spawning process '{id}': {binary} {:?}", args);
         match command.spawn() {
             Ok(mut child) => {
                 let stdout = child.stdout.take().expect("Failed to open stdout");
@@ -67,6 +68,7 @@ impl ProcessManager {
                             let json_str = line[JSON_ROW_PREFIX.len()..].to_string();
                             crate::events::emit_json_row(&app_clone, &id_clone, json_str);
                         } else {
+                            log::info!(target: "subprocess", "[{id_clone}] {line}");
                             emit_stdout(&app_clone, &id_clone, line);
                         }
                     }
@@ -77,6 +79,7 @@ impl ProcessManager {
                 tokio::spawn(async move {
                     let mut reader = BufReader::new(stderr).lines();
                     while let Ok(Some(line)) = reader.next_line().await {
+                        log::warn!(target: "subprocess", "[{id_clone2}] [stderr] {line}");
                         emit_stderr(&app_clone2, &id_clone2, line);
                     }
                 });
@@ -112,6 +115,8 @@ impl ProcessManager {
                         }
                     };
 
+                    log::info!(target: "subprocess", "Process '{id_clone_exit}' exited with code {exit_code}");
+
                     // Reap child from process manager maps upon exit
                     {
                         let mut stdins = stdins_clone.lock().await;
@@ -126,6 +131,7 @@ impl ProcessManager {
                 Ok(())
             }
             Err(e) => {
+                log::error!(target: "subprocess", "Failed to spawn '{id}': {e}");
                 emit_error(&app, &id, e.to_string());
                 Err(e.to_string())
             }

src-tauri/src/settings.rs

@@ -24,6 +24,7 @@ pub struct ProfilingPreset {
 pub struct AppSettings {
     pub argyll_binary_dir: Option<String>,
     pub default_instrument: Option<String>,
+    pub log_level: Option<String>,
     #[serde(default)]
     pub custom_presets: Vec<ProfilingPreset>,
 }

src/index.html

@@ -489,6 +489,26 @@
           <label for="default_instrument">Default Instrument Override</label>
           <input type="text" id="default_instrument" placeholder="e.g. i1">
         </div>
+        <div class="form-group" style="margin-top: 16px; padding-top: 14px; border-top: 1px solid var(--border-color, #333);">
+          <label style="font-weight: 600;">Diagnostics &amp; Logging</label>
+          <div class="input-row" style="margin-top: 8px;">
+            <div>
+              <label for="logLevelSelect" class="sub-label">Log Level</label>
+              <select id="logLevelSelect">
+                <option value="error">Error (Minimal)</option>
+                <option value="warn">Warn</option>
+                <option value="info" selected>Info (Standard)</option>
+                <option value="debug">Debug (Detailed)</option>
+                <option value="trace">Trace (Verbose)</option>
+              </select>
+            </div>
+            <div style="display: flex; align-items: flex-end; gap: 8px;">
+              <button type="button" id="btnOpenLogFolder" class="secondary" title="Open log folder in file explorer">📂 Open Log Folder</button>
+              <button type="button" id="btnCopyLogPath" class="secondary" title="Copy log path to clipboard">📋 Copy Path</button>
+            </div>
+          </div>
+          <small id="logPathDisplay" class="path-display" style="margin-top: 6px; display: block;"></small>
+        </div>
         <div class="modal-actions">
           <button id="saveSettingsBtn" class="primary">Save Settings</button>
           <button id="closeSettingsBtn" class="secondary">Cancel</button>

src/js/settings.js

@@ -5,31 +5,80 @@ export async function initSettings() {
     const openBtn = document.getElementById('openSettingsBtn');
     const saveBtn = document.getElementById('saveSettingsBtn');
     const closeBtn = document.getElementById('closeSettingsBtn');
+    const logLevelSelect = document.getElementById('logLevelSelect');
+    const btnOpenLogFolder = document.getElementById('btnOpenLogFolder');
+    const btnCopyLogPath = document.getElementById('btnCopyLogPath');
+    const logPathDisplay = document.getElementById('logPathDisplay');
 
     if (!dialog || !openBtn) return;
 
+    async function refreshLogPath() {
+        if (!logPathDisplay) return;
+        try {
+            const path = await invoke('get_log_path');
+            logPathDisplay.textContent = path ? `Log file: ${path}` : '';
+        } catch (err) {
+            console.warn("Could not retrieve log path:", err);
+        }
+    }
+
     openBtn.addEventListener('click', async () => {
         try {
             const settings = await invoke('load_settings');
             document.getElementById('argyll_binary_dir').value = settings.argyll_binary_dir || '';
             document.getElementById('default_instrument').value = settings.default_instrument || '';
+            if (logLevelSelect && settings.log_level) {
+                logLevelSelect.value = settings.log_level;
+            }
+            await refreshLogPath();
             dialog.showModal();
         } catch (e) {
             console.error("Failed to load settings:", e);
         }
     });
 
+    if (btnOpenLogFolder) {
+        btnOpenLogFolder.addEventListener('click', async () => {
+            try {
+                await invoke('open_log_dir');
+            } catch (err) {
+                alert(`Failed to open log folder: ${err}`);
+            }
+        });
+    }
+
+    if (btnCopyLogPath) {
+        btnCopyLogPath.addEventListener('click', async () => {
+            try {
+                const path = await invoke('get_log_path');
+                if (path) {
+                    await navigator.clipboard.writeText(path);
+                    const originalText = btnCopyLogPath.textContent;
+                    btnCopyLogPath.textContent = '✓ Copied!';
+                    setTimeout(() => {
+                        btnCopyLogPath.textContent = originalText;
+                    }, 2000);
+                }
+            } catch (err) {
+                alert(`Failed to copy log path: ${err}`);
+            }
+        });
+    }
+
     if (closeBtn) {
         closeBtn.addEventListener('click', () => dialog.close());
     }
 
     if (saveBtn) {
         saveBtn.addEventListener('click', async () => {
-            const settings = {
-                argyll_binary_dir: document.getElementById('argyll_binary_dir').value.trim() || null,
-                default_instrument: document.getElementById('default_instrument').value.trim() || null
-            };
             try {
+                const currentSettings = await invoke('load_settings').catch(() => ({}));
+                const settings = {
+                    ...currentSettings,
+                    argyll_binary_dir: document.getElementById('argyll_binary_dir').value.trim() || null,
+                    default_instrument: document.getElementById('default_instrument').value.trim() || null,
+                    log_level: logLevelSelect ? logLevelSelect.value : (currentSettings.log_level || 'info'),
+                };
                 await invoke('save_settings', { settings });
                 dialog.close();
             } catch (e) {