miniSCP/docs/architecture.md

miniSCP architecture

Dense reference for development and debugging. Companion files: build-and-release.md, platform-notes.md, gotchas.md.

Process model

• Bun main process (src/bun/): the native launcher runs electrobun's main.js on the Bun the 2.x devkit pins (1.4.0, shipped in the bundle — build.mainProcess: "bun"), which starts our bundle in a Worker. Imports the SDK as electrobun/main (projected into .hutch/devkit/). Owns every privileged capability: filesystem, SSH, window management, native menus/dialogs/tray, the connection/settings stores.
• Webviews (ui/ Angular): one per window, system WebKit on macOS / WebView2 on Windows / WebKitGTK on Linux. Zero privileged access — everything goes through RPC.
• RPC transport: one WebSocket server in the bun process, multiplexed by webviewId (each webview auto-connects using natively injected globals; packets AES-GCM-encrypted per webview). 2.x Electroview queues sends while its hostSocket connects and falls back to a native bridge when the socket is unavailable. Requests are typed by the AppRPC schema in src/shared/rpc.ts.

The one-schema rule

AppRPC is a single superset schema shared by all window kinds. This works because electrobun allows partial handler sets (a side only implements what it serves) and silently drops messages nobody listens to. Every response crosses the bridge as Result<T> ({ok:true,…}|{ok:false,error}) — exceptions never cross; wrap() in src/bun/rpc-handlers.ts enforces it.

Per-window RPC instances (critical)

Each BrowserWindow MUST receive its own defineRPC(...) instance: binding a BrowserView calls rpc.setTransport(...), so a shared instance would have its transport stolen by the most recent window. createAppRPC (main), createEditorRPC (per editor window, hooks close over that window's record), createManagerRPC (the single manager window), createSettingsRPC (the single Settings window). rpc.send.* on an instance targets exactly its own webview.

The events late-binding pattern

createAppRPC needs to trigger things that need rpc.send (which doesn't exist until after construction). AppDeps.events is a mutable object of no-op functions, reassigned in src/bun/index.ts after everything exists: sessionClosed, connectionsChanged, openEditor, settingsChanged, openConnectionManager, openSettings, showAbout, applyUpdate (the update restart lives in index.ts beside the before-quit guard it must get past — see build-and-release.md "Auto-updater").

Window kinds

src/bun/windows.ts — buildPreload(mode, settings, ctx?) injects __APP_PLATFORM, __APP_MODE (main|editor|manager|settings), __APP_CTX before any page script, plus the persisted theme attributes and interface scale so the first paint is already right. ui/src/main.ts picks the root component from APP_MODE; all four roots use selector app-root (index.html hosts only that tag). chromeOptions() is the ONLY place the native frame is decided, spread by the main window and openSecondaryWindow: macOS hiddenInset + trafficLightOffset {x:12,y:4} (2.x semantics — see gotchas; the UI renders an h-10 pl-24 drag-region header via IS_MAC_CHROME); other platforms keep the native titlebar and a compact h-9 non-drag header.

WindowRegistry<Rec> (same file): keyed window map with dedupe/activate, cascade placement off an anchor frame, focus tracking. electrobun's emitter has no off() — track() closures capture only (this, key) so closed records can be garbage collected. A future "window follows window" grouping belongs here (anchor.on('move') + setPosition).

Editor windows (src/bun/editor-windows.ts + ui/src/app/skins/shadlike/editor-window/)

One window per file, key sessionId+path (sessionId, not fsKey: saves route through a concrete session, and local is one shared session anyway). Re-opening focuses the existing window. The webview fetches its own content (readFile) — openEditor just creates the window with ctx in the preload.

Close safety (designed when electrobun window close was NOT cancellable — 1.18.1 had no allow response like before-quit; 2.x adds a cancellable will-close for the titlebar close, not used yet — see gotchas):

1. ⌘W (the page's own close-window key; a ⌘W it doesn't claim falls through to the app menu, which bun routes back as editorCloseRequest) / Close button → styled in-window Save/Don't Save/Cancel, which takes focus (Save; ⌘S = Save, Esc = Cancel, Tab cycles) so keys can't edit the text behind it; the confirm path calls editorClose which sets suppressPrompt before win.close().
2. Traffic-light close → the window is already gone, but the editor mirrored its draft to bun (editorState, 400 ms debounce + flush on blur/dirty-flip) → native Save/Discard box from the held draft. A failed save (dead session) parks the draft via EditManager.rescueDraft into the edits-leftovers dir, offered back at next boot. Known limit: the last ≤400 ms of keystrokes can be lost on an instant type-then-close.
3. ⌘Q → the app-level before-quit guard (cancellable) counts dirty editors plus running transfers.

editorSave is a dedicated request (not generic writeFile) so one handler atomically writes + cleans the bun record + retitles + pushes pathRefresh to the main window (panels showing that directory refresh). Editor upgrades: scroll-synced line gutter (hidden when wrap is on — wrapped line numbers would need per-edit height measurement), Alt/⌥Z wrap toggle, custom find bar (matches computed in TS, setSelectionRange + scrollTop math — deliberately not findInPage, which is a shim on WebView2). Find next / previous (⌘G / ⇧⌘G, F3 / ⇧F3) step from the caret with the bar open or closed — the query survives closing it. Focus after a state change goes through afterNextRender({ injector }): under zoneless CD a microtask runs BEFORE the render that creates the @if element.

Connection-manager window (src/bun/manager-window.ts)

Single instance, centered over main, modal to main only (editors stay usable). No native modality exists (re-checked on 2.0.2: no parent/owner/sheet option or input lock in any SDK or the core's exports; styleMask.DocModalWindow is only the cosmetic NSWindow bit), so three layers approximate it: bun bounces main's focus event back to the manager; the main webview renders a click-swallowing overlay (managerState message); main drops its keyboard shortcuts and bun drops main-targeted menu actions while open. Connect / open-stack execute in the MAIN window via the connect:<id> / open-stack:<id> menuAction channel (the manager closes right after — a failed connect surfaces in main). Store edits push connectionsChanged so main's ConnectionsService reloads; a reload-retry in App.findConnection covers the save→connect race. setAlwaysOnTop is deliberately NOT used (it would float over editor windows).

Settings window (src/bun/settings-window.ts + ui/src/app/skins/shadlike/settings-window/)

Single instance, centered over main, not modal: every control is a plain SettingsService setter, so each edit is an ordinary save that bun rebroadcasts — the other windows follow live while it stays open. Opened by the tab-bar gear and the open-settings key (⌘, / Ctrl+,, openSettings from main) and, on macOS, the app menu's "Settings…". Its RPC serves only getSettings/saveSettings/pickEditorApp/showAbout/settingsClose. Its page claims its own close-window key (settingsClose); a ⌘W it doesn't claim falls through to the app menu's Close Tab, and bun checks the Settings window's focus FIRST and closes it (see gotchas). Sidebar sections: Appearance, Transfers, Editor, File list (visible columns — the column-header right-click menu toggles the same setting), About (opens the native About box). The native title is options.title, retitled on a locale switch.

Bun modules

• fs/provider.ts — FileSystemProvider interface: uniform local/SFTP ops + path helpers + streams + fsKey (see self-copy below).
• fs/local.ts — node:fs, lstat-based, fsKey="local". Owner/group via cached id -nu / dscacheutil|getent spawns (win32 → undefined). listLocalDrives() for the Windows drive picker (fsutil).
• fs/sftp.ts — ssh2 under Bun (pure JS; native accelerators are build externals). POSIX paths always. fsKey = resolvedIP:port via dns.lookup at connect. Owner/group parsed from the ls-style readdir longname. Keepalive 15 s; closedByUs flag so dispose() doesn't fire the onClose callback. mtime seconds→ms; mode masked & 0o7777.
• fs/registry.ts — sessionId → provider map; "local" is built-in; add() mints sftp-<n>; drop() (session died) vs remove() (clean).
• fs/watcher.ts — LocalDirWatcher: fs.watch handles keyed by dir, debounced ~150 ms (watch fires bursts). Drives local auto-refresh: the main webview sends setWatchedDirs (the active tab's local panel cwds); a change fires onChange → rpc.send.pathRefresh({sessionId:"local", dir}). onChange is late-bound in index.ts (the events pattern). SFTP has no watch, so remote panels are polled UI-side instead (see panels.service).
• transfers/engine.ts — FIFO job queue. Semaphore with live resize (wake() reserves slots synchronously — an async waiter increment was a race). Per-job worker pool (MAX_WORKERS_PER_JOB=8) draws from the shared slot budget, so in-folder parallelism and cross-job fairness share one knob (setConcurrency from settings; single mode = 1). activeStreams set enables hard cancel. emit throttled 100 ms. failSession fails that session's jobs. Probe files: .{appname}-probe-*.
• transfers/walk.ts — recursive tree walk (segment arrays, skips symlinks)
  • removeRecursive.
• Self-copy protection (data-loss class): copying a file onto itself truncates it (createWriteStream O_TRUNCs before the read). Guards compare fsKey, never sessionId — two sessions to one server are distinct sessions on one filesystem. When fsKeys differ but paths collide, probeSameFilesystem writes a token via dst and reads it via src to unmask hidden aliases (SFTP has no dev/inode). Fails open (permissions produce their own error). Residual risk (documented in README): same filesystem mounted at different paths.
• edits.ts — readFileText/writeFileText (2 MB cap) for the built-in editor; EditManager for the external-editor flow: temp-download under appDataDir()/edits/<id>/ + meta.json, directory watch (survives atomic renames), 400 ms debounce → engine upload. Watchers die with their session; leftover dirs are offered for cleanup at boot. launchEditor is the platform seam (open / cmd /c start / xdg-open).
• store/paths.ts — per-OS appDataDir() + migrateLegacyDataDir() (renames a BRANDING.legacyNames dir into place on boot; list currently empty).
• store/connections.ts — plaintext-passwords JSON (deliberate v1 choice), atomic tmp+rename, 0600 + win32 icacls ACL. store/settings.ts — defaults spread-merge on load, so NEW SETTINGS KEYS need no backend change.
• menu.ts — macOS-only app menu, rebuilt on every connections change (the Connect submenu mirrors the store; "Settings…" carries ⌘,). ⌘W is intercepted by the menu, so bun routes close-tab to a focused Settings or editor window first. Labels go through backend i18n.t and the menu is rebuilt on a locale change too.
• i18n.ts — backend translator (native menus + thrown error messages, which no Angular service can reach). setLocale(setting) caches the resolved locale (from settings.locale, system via Intl…resolvedOptions().locale); t(key, params) shares the same src/shared/i18n dictionaries as the UI. Wired in index.ts on boot and on settingsChanged (relocalizes + rebuilds the app menu). The context menu no longer needs this — it is Angular and reads I18nService directly.
• tray.ts — static icon, click = activate main. macOS template image; Windows colored icon. No setImage calls ever (they lose the template treatment) and no menu (clicks arrive directly).
• index.ts — composition root: wiring order matters (events assigned after rpc; manager/editors constructed after win; quit guard; focus tracking for notification suppression across all windows).

UI layout

ui/src/app/
  core/            app.config.ts, icons.ts, platform.ts, format.ts, file-icons.ts,
                   metrics.ts and every *.service.ts — the non-visual layer
  skins/shadlike/  the component tree: four window roots (SHAD_ROOTS barrel,
                   picked by main.ts), dialogs, context menu

Components reach core/ through the @core/* tsconfig alias (alongside @shared/* → src/shared), which is deliberate: components sit at varying depths and an alias keeps their imports identical wherever a file moves. Do not replace it with relative paths.

Where a new rule goes: behaviour → core/; markup and appearance → the component; tokens → ui/src/styles.css.

UI services (ui/src/app/core/)

• rpc.service.ts — wraps Electroview.defineRPC. Push messages fan out through plain callback registries, never signals: a signal consumed from an effect that also writes signals re-triggers itself (this froze the whole app once), and signal coalescing drops progress snapshots. All requests are gated on the socket-open promise (electroview.hostSocket) — on 1.18.1 calls fired during boot were silently lost; 2.x Electroview queues them itself, so the gate is belt-and-braces now. request and send are ready-gated Proxies.
• panels.service.ts — PanelState (per panel): sessionId, fsKey, cwd, entries, sort, cursor, selection, type-to-filter. sorted computed: filter → dirs-first sort (name/size/mtime numeric, kind/rights/owner/group via display-string compare) → synthetic '..' row unshifted unless isRootPath(cwd). touched marks user navigation (connect flows only auto-load localDir into an untouched local panel). connectToken supersedes stale connects. Workspace = tab = left/right pair + activeSide. Remote goes RIGHT on connect/open-stack (commander convention); per-panel dropdown connects target their own panel. Auto-refresh (always on): refresh({silent}) re-lists without the loading/busy flags and touches no DOM (scroll/cursor/selection/filter preserved), snapshotting sessionId+cwd to discard results if the user navigated mid-flight. Only the active tab is live: its local panels are fs.watched (backend setWatchedDirs effect + pathRefresh push → silent refresh), its remote panels polled every 3s (REMOTE_POLL_MS); switching tabs silently refreshes the newly-active pair. A future on/off setting is stubbed in commented breadcrumbs (types.ts, settings.service, tab-bar).
• transfers.service.ts — jobMap from transferUpdate callbacks; EMA speed (SPEED_SMOOTHING=0.7); copyToOtherPanel guards same-fs+same-dir before enqueue and runs the collision flow (same-path auto-skip, type-mismatch skip, overwrite dialog with all/none batch modes).
• settings.service.ts — one signal per setting; imperative apply pattern (applyTheme/DarkTone set data-* attributes on <html>; applyUiScale sets its inline font-size); applyAll also serves the settingsChanged broadcast, so every window follows a save made in any other. Every window RPC serves saveSettings (editor and manager windows save too — the scale shortcuts — and the Settings window is nothing but saves); bun's settingsSaved() in index.ts runs the side effects once and rebroadcasts to every window except the sender, so there is no echo to fight a held Cmd+. applyAll never persists. Saves are whole-object, so nothing persists until the first getSettings landed (loaded): a ⌘+ pressed while a window opens would otherwise write the defaults over every remap. New setting = five touches here + types.ts (backend merges automatically; sanitize hand-editable shapes in SettingsStore.load).
• focus.service.ts — dependency-free tick/bump(); dialogs bump it, the main window's panels listen — but a panel only takes focus while NO dialog or menu is up (a run of overwrite questions reuses one dialog instance; focusing the list behind it handed Enter/Delete to the panel). Exists so dialogs don't inject PanelsService (whose constructor spawns a workspace — fatal in secondary windows).
• shortcuts.service.ts — the keyboard layer over src/shared/keymap.ts; see "Keyboard" below.
• focus-cycle.ts — cycleFocus(root, event): Tab / ⇧Tab by hand (see "Keyboard").
• connections.service.ts — store mirror + ssh-config hosts; reloads on the connectionsChanged push.
• i18n.service.ts — runtime translator. locale signal + t('ns.key', params) (dotted lookup, {param} interpolation, {one,other} plural maps via Intl.PluralRules); missing keys fall back to English then the raw key. Reactive by design: t() reads the locale signal, so every template binding that calls it re-renders live on a language switch (call-stack tracking, see gotchas.md) — no pipe. Also exposes locale-aware date()/size() /speed() so the file list reformats on switch. SettingsService.applyLocale resolves the locale setting (system → navigator.language) into it, on boot and on the settingsChanged broadcast (so editor/manager windows follow).
• file-actions.service.ts — one file-command dispatcher, run(id, { side, panel, entry }), for every entry point: list keys (the cursor row), row-menu picks (the right-clicked row, captured in the menu's onPick closure), the macOS menu bar's File/View items and the panel toolbar. Ids are keymap FileCommands (open, open-default, send, edit, rename, new-folder, new-file, chmod, delete, trash, copy-path, reveal, refresh, sort-*). Selection if any, else the target row; .. stands for the folder. open enters folders and opens a LOCAL file in its default app only when openFilesOnEnter is set (Settings → File list); open-default (the menu's Open on a local file) always does. trash walks the selection one moveToTrash at a time. Main-window only (it injects TransfersService).
• context-menu.service.ts + skins/shadlike/context-menu.ts — the panel and tab right-click menus, in HTML. Electrobun's native showContextMenu is a no-op on Linux, so it was retired on ALL platforms rather than kept as a second code path (see platform-notes.md). The service builds the item list (row / empty-space menu, the header column picker, and the panel source picker — Local, drives, connections under per-stack header items, ~/.ssh/config hosts — which replaced a bespoke popover so it gets the same keys and look) and holds the open request as a signal; the component renders it at a point (MenuPoint: a MouseEvent, or a row rect for a keyboard-opened menu) with edge-flip clamping, a scrolling clamped box, and close-on-blur/resize/scroll. Items carry shortcut (a keymap id: its first key is the soft hint at 60% of the row colour, and pressing it while the menu is open picks the item) and icon (drawn in the check column; only the everyday verbs get one — Send, Edit, Rename, Delete, New Folder, New/Close Tab, the toolbar's own glyphs). Keys: ↑↓ Home End move the one highlight (mouse hover shares it), Enter/Space pick, Esc closes, items are not Tab stops; every handled key stops propagation so the window handler never runs it twice. A keyboard-opened menu starts with its first item highlighted (initialIndex). A request's onPick takes the pick (row menu → FileActionsService.run, source picker → FilePanel); otherwise col:* / tab:* strings go through RpcService.emitMenuAction to the SAME App.handleMenuAction dispatcher the macOS app menubar uses. The three shell actions the webview cannot perform (reveal, open-with-default, copy path) go back to bun via the shellItemAction RPC, which is all that remains of the old native menu. tabItems() builds the workspace-tab menu (tab:new, and tab:close|close-others|close-right|disconnect:<id>), served by PanelsService.closeOtherWorkspaces / closeWorkspacesToRight / disconnectWorkspace. The target id travels inside the action string: the right-clicked tab is not necessarily the active one, so nothing on that path may fall back to activeWorkspaceId. Illegal entries are disabled, not omitted — a menu whose items move between right-clicks is worse than one with a dead row. The disabled styling (pointer-events: none) only stops the pointer; the keyboard path never consults it — so pick() and the arrow-key walker check the flag themselves.
• file-icons.ts — extension → category map driving glyphs, colors (fixed --icon-* tokens from Oxide's hue scales) and the Kind column.
• icons.ts — the one icon registry (TDesign, @ng-icons/tdesign-icons), passed to provideIcons in app.config.ts. Icon names are plain strings in templates and the build never checks them: an unregistered name renders nothing (console error only), so every name used anywhere must be listed here.
• platform.ts — preload-global readers (PLATFORM, APP_MODE, EDITOR_CONTEXT, IS_MAC/IS_MAC_CHROME, IS_WINDOWS, IS_LINUX) + blockNativeContextMenu (kills WebKit's Reload/Inspect menu outside text fields — the app draws its own menu instead) + blockReloadKeys (swallows unclaimed F5 / Ctrl+R / Ctrl+F5 / Ctrl+Shift+R on Windows, where WebView2 would reload the page and drop every session; each window root calls it last).
• updater.service.ts — auto-updater state for the tab-bar pill. Signals state (idle→available→downloading→ready|error), version, progress. Subscribes the updateStatus push (backend Updater.checkForUpdate on launch+6h, onStatusChange progress); ready is derived when the downloadUpdate request resolves ok (not a pushed phase). download() / apply() (relaunch) / check() (menu). Backend wiring lives in src/bun/index.ts; feed is release.baseUrl (https://miniscp.com/dl, the /dl host in site/). See build-and-release.md "Auto-updater".

Keyboard

One keymap — src/shared/keymap.ts, shared so the webviews and bun (the macOS menu bar) read the same table. BINDINGS lists every command: id, group (Settings sections), scopes, and default combos per platform (mac / other, best first: the first is the hint menus and tooltips show). Combos are platform-neutral strings (Mod+Shift+N: Mod = ⌘ on macOS, Ctrl elsewhere; Ctrl a literal ⌃ only macOS tells apart). Letters match the layout's character (AZERTY's A is A) and fall back to the physical key under Alt (⌥Z types Ω) and on non-Latin layouts; digits match physically (AZERTY types "&" on 1); punctuation by character first (AZERTY's comma is on the M key), physical second (⇧] makes "}"). Matching is exact: ⌃F is not ⌘F, Ctrl+Tab is not Tab, and neither the Windows key nor AltGr is ever part of a binding. effectiveKeymap(overrides) applies AppSettings.keybindings (rows that differ from the defaults; [] unbinds) and drops anything malformed. conflicts() / ownerOf() work over overlapping scopes; the spec (keymap.spec.ts) proves the defaults conflict-free, round-trippable and unshadowed on both platforms.

Scopes. panel = the focused file list (navigation, file commands, sorting); main = anywhere in the main window (tabs, window commands); editor / manager / settings per window; any = every window (interface scale). panel sits inside main, so they conflict-check together.

ShortcutsService resolves keydowns against the effective keymap (reactive: a remap applies live in every window via the settings broadcast) and formats hints — label(id) / labels(id) / tip(text, id) / tipFixed(text, 'Shift+Enter'), with localized key names off macOS (keys.names.*: German says Strg+Entf). claim() = resolve + preventDefault (so the macOS menu never runs it twice) + auto-repeat only for movement-like commands (holding ⌘W closes one tab). IME composition is never a shortcut. From a text field only firesInTextField() combos count: ⌘/Ctrl and Alt chords and F-keys, but not plain keys, not text-editing chords (⌘⌫, ⌥←, ⌘A) and not Ctrl+Alt off macOS (AltGr).

Dispatch (one place per window): an open context menu owns its keys; an open dialog owns Enter / Esc / Tab while the main window swallows window commands and the panel commands the macOS menu bar carries (an unclaimed ⌘T would otherwise reach the menu and open a tab behind the dialog); the focused list (FilePanel.onKeydown) runs, in order, the fixed filter-editing keys while a query is typed, the panel keymap (Shift + a movement key extends the selection over the rows passed — a fixed rule that follows remaps), lets main matches bubble, then type-to-filter, then Esc's fixed chain (clear the filter → cancel a connect → clear the selection); App runs main. Every root ends with blockReloadKeys. Keys that land on <body> (a click dropped focus) are forwarded to the active list (PanelsService.forwardListKey), and App's (mousedown) keeps focus on the list after chrome-button clicks.

macOS key equivalents are page-first. WKWebView hands ⌘-keys to the page before the app menu (WebKit WebViewImpl::performKeyEquivalent); only keys the page doesn't preventDefault reach the menu bar. So the page owns every app shortcut, and a window that doesn't claim a key lets it fall through to the menu (⌘W in a window whose close-window was remapped away still hits Close Tab, which bun routes to the focused Settings / editor window first).

Focus without Keyboard navigation. WKWebView's Tab skips buttons, checkboxes and radios unless the user turned on System Settings → Keyboard → Keyboard navigation, so cycleFocus(root, event) walks Tab / ⇧Tab by hand (DOM order, wrap, a radio group is one stop): every dialog (it is also their focus trap), the transfer list (⌘J opens it focused), the editor's save prompt. Dialogs carry role="dialog" aria-modal, take initial focus (the chmod dialog on its octal field, Enter applies) and stop Esc from propagating — a window-level Esc (the connection manager closes on it) must not see it too. A base-layer :focus-visible ring in --ring marks the focused control.

Opening a row's menu from the keyboard: ⇧F10 / the Menu key / ⌃↩ (macOS) open the cursor row's menu under the row, first item highlighted; the selection is kept, its commands act on it like the F-keys do.

Theming

ui/src/styles.css: OKLCH tokens adapted from Oxide's design system (docs.oxide.computer: a cool neutral scale at hue 260 with almost no chroma, one green accent, opaque strokes; the comments carry Oxide's step names n0…n1300 / green-800). Dark values are duplicated in :root[data-theme='dark'] AND a prefers-color-scheme media block (system mode) — every dark token change goes in BOTH; retone neutrals along the one scale, or warm and cool surfaces clash. There is no accent setting: --primary is Oxide green per theme (green-800 dark, green-500 light), so selection (bg-primary/15), the cursor row (--cursor-tint, a color-mix of --primary), focus rings (green-600) and --success all read green. Surface layers, each its own shade: --chrome (frame — tab/transfer/status bars, the editor/manager/settings header+footer strips and sidebars), the file panel's header strip stepping toward the list — session strip --toolbar, path bar --toolbar-2, column headers --toolbar-3 (color-mix steps declared once in :root, so every theme follows) — then --background (file lists, editor text, forms; --row-alt stripes odd file rows, skipped on the cursor/selected row so two bg-* utilities never fight) and --card (popovers, dialogs, toasts). The right-click menu is the exception: the darkest surface (bg-chrome) behind a faint border-border/60, and its highlighted item takes Oxide's selected style — --primary-surface fill (Oxide surface-accent: green-200 dark, green-1200 light) with text-primary; mouse and keyboard share that one highlight (activeIndex). The ACTIVE panel is marked by a 0.125rem --primary line along its top edge (an inset box-shadow on the session strip, so switching panels never shifts layout). Dark: frame 0.162 < list 0.195 < header 0.275 → 0.248 → 0.221 < card 0.29; light steps greys out from near-white content: frame 0.925 < header 0.95 → 0.965 → 0.98 < list = card 0.995. --accent is translucent (n0 at 5% light, white 7% dark): hover/selected states sit on every layer, and an opaque hover vanishes on a surface of its own lightness. Strokes are opaque (--border n300 dark / n900 light, --input one step stronger). The "darker" tone is true-black AMOLED: chrome, background, toolbar (+ its steps) and row-alt are all #000 (the layers collapse on purpose); elevation survives only via --card/--muted/--accent (opaque there). Square design: no rounded-* utilities and no radius tokens; an @layer base block restyles native controls to match — checkboxes/radios (appearance: none, a drawn check / square dot), selects (a currentColor caret; use pl-*, never px-*, on a select), hidden number spinners, and square ::-webkit-scrollbars (which make macOS scrollbars always visible). @theme inline maps tokens to Tailwind utilities (bg-primary, text-icon-folder, bg-toolbar-2, bg-cursor-tint). File-type icon colors come from Oxide's hue scales (800 steps dark, 600 light). Interface scale (settings.uiScale, 0.5–4 in 0.1 steps): one root font-size lever — applyUiScale sets html { font-size: 16px * scale }, and since EVERY size in the app is rem (panel tokens like --row-h, all Tailwind utilities, ng-icon sizes), the whole UI scales, chrome included. Driven by the Settings window's stepper, Ctrl/Cmd +/−/0, and preload-baked for a flash-free first paint. It replaced the 3-tier data-text axis; the store migrates old textSize values. TS that measures rem-sized CSS converts through @core/metrics remPx() — never an assumed 16.