feat: three dashboard view modes — Auto, Fit, Compact

Auto: current behavior (auto-fill grid, fixed tile height, scrollable).
Fit: calculates cols × rows to fill viewport exactly, zero scroll.
Compact: 80px tiles, high density, auto-fill with 200px min-width.

Toggle button (▦) in overview header cycles modes. Fit recalculates
on window resize. View mode persisted in localStorage alongside other
display settings (viewMode: 'auto' default in DISPLAY_DEFAULTS).

- CSS: .session-grid--fit and .session-grid--compact modifiers
- JS: VIEW_MODES, cycleViewMode(), applyFitLayout() functions
- HTML: #view-mode-btn between + and ⚙ in overview header
- Tests: 8 new JS tests, 3 CSS tests, 1 HTML test all passing

muxplex/frontend/app.js

@@ -140,7 +140,10 @@ const DISPLAY_DEFAULTS = {
   gridColumns: 'auto',
   bellSound: false,
   notificationPermission: 'default',
+  viewMode: 'auto',
 };
+
+var VIEW_MODES = ['auto', 'fit', 'compact'];
 const NEW_SESSION_DEFAULT_TEMPLATE = 'tmux new-session -d -s {name}';
 const DELETE_SESSION_DEFAULT_TEMPLATE = 'tmux kill-session -t {name}';
 
@@ -644,6 +647,17 @@ function renderGrid(sessions) {
     updatePillBell();
   }
 
+  // Reapply view mode layout after grid HTML is rebuilt
+  var currentDs = loadDisplaySettings();
+  var currentMode = currentDs.viewMode || 'auto';
+  if (currentMode === 'fit' && grid) {
+    grid.classList.add('session-grid--fit');
+    applyFitLayout(grid);
+  } else if (currentMode === 'compact' && grid) {
+    grid.classList.add('session-grid--compact');
+    grid.style.gridTemplateColumns = 'repeat(auto-fill, minmax(200px, 1fr))';
+  }
+
 }
 
 // ---------------------------------------------------------------------------
@@ -1071,29 +1085,121 @@ function saveDisplaySettings(settings) {
   } catch (_) { /* blocked — ok */ }
 }
 
+/**
+ * Calculate and apply grid layout to fill the viewport exactly (Fit mode).
+ * Determines optimal cols × rows based on tile count and available space.
+ * @param {Element} grid - The session grid element
+ */
+function applyFitLayout(grid) {
+  var count = grid.querySelectorAll('.session-tile').length;
+  if (count === 0) return;
+
+  // Available space — use grid's parent container
+  var parent = grid.parentElement;
+  var availH = parent ? parent.clientHeight : window.innerHeight;
+  var availW = grid.clientWidth;
+
+  // Subtract padding and gap
+  var style = getComputedStyle(grid);
+  var padT = parseFloat(style.paddingTop) || 0;
+  var padB = parseFloat(style.paddingBottom) || 0;
+  var padL = parseFloat(style.paddingLeft) || 0;
+  var padR = parseFloat(style.paddingRight) || 0;
+  var gap = parseFloat(style.gap) || 8;
+
+  var innerW = availW - padL - padR;
+  var innerH = availH - padT - padB;
+
+  // Calculate optimal cols/rows — start with square root
+  var cols = Math.ceil(Math.sqrt(count));
+  var rows = Math.ceil(count / cols);
+
+  // Prefer wider layouts (more cols, fewer rows) since tiles are landscape
+  if (rows > 1 && cols < count) {
+    var altCols = cols + 1;
+    var altRows = Math.ceil(count / altCols);
+    if (altRows < rows) {
+      cols = altCols;
+      rows = altRows;
+    }
+  }
+
+  // Tile height from available space
+  var tileH = (innerH - gap * (rows - 1)) / rows;
+
+  grid.style.gridTemplateColumns = 'repeat(' + cols + ', 1fr)';
+  grid.style.gridTemplateRows = 'repeat(' + rows + ', 1fr)';
+
+  // Override tile height so tiles fill the grid rows
+  grid.querySelectorAll('.session-tile').forEach(function(t) {
+    t.style.height = tileH + 'px';
+  });
+}
+
+/**
+ * Cycle the dashboard view mode: auto → fit → compact → auto.
+ * Persists to localStorage and reapplies display settings.
+ */
+function cycleViewMode() {
+  var ds = loadDisplaySettings();
+  var idx = VIEW_MODES.indexOf(ds.viewMode || 'auto');
+  ds.viewMode = VIEW_MODES[(idx + 1) % VIEW_MODES.length];
+  saveDisplaySettings(ds);
+  applyDisplaySettings(ds);
+
+  // Update button label
+  var btn = document.getElementById('view-mode-btn');
+  if (btn) btn.title = 'View: ' + ds.viewMode;
+}
+
 /**
  * Apply display settings to the live DOM.
  * Sets --preview-font-size CSS custom property and updates #session-grid
- * grid-template-columns based on the gridColumns setting.
+ * grid-template-columns based on the gridColumns setting and viewMode.
  * @param {object} ds - display settings object
  */
 function applyDisplaySettings(ds) {
   // Apply font size as CSS custom property (tile previews)
-  document.documentElement.style.setProperty('--preview-font-size', ds.fontSize + 'px');
+  if (document.documentElement) {
+    document.documentElement.style.setProperty('--preview-font-size', ds.fontSize + 'px');
+  }
 
   // Apply font size to the live xterm.js terminal without reconnecting
   if (window._setTerminalFontSize) {
     window._setTerminalFontSize(ds.fontSize);
   }
 
-  // Apply grid columns
+  // Apply view mode to grid
   var grid = document.getElementById('session-grid');
-  if (grid) {
-    if (ds.gridColumns === 'auto') {
+  if (!grid) return;
+
+  var mode = ds.viewMode || 'auto';
+
+  // Remove all mode classes
+  grid.classList.remove('session-grid--fit', 'session-grid--compact');
+
+  // Reset any inline styles from previous fit calculation
+  grid.style.removeProperty('grid-template-rows');
+  grid.querySelectorAll('.session-tile').forEach(function(t) {
+    t.style.removeProperty('height');
+  });
+
+  if (mode === 'auto') {
+    // Restore grid columns setting
+    if (ds.gridColumns === 'auto' || !ds.gridColumns) {
       grid.style.removeProperty('grid-template-columns');
     } else {
       grid.style.gridTemplateColumns = 'repeat(' + ds.gridColumns + ', 1fr)';
     }
+
+  } else if (mode === 'fit') {
+    grid.classList.add('session-grid--fit');
+    applyFitLayout(grid);
+
+  } else if (mode === 'compact') {
+    grid.classList.add('session-grid--compact');
+    // Use auto-fill but with smaller minmax for higher density
+    grid.style.gridTemplateColumns = 'repeat(auto-fill, minmax(200px, 1fr))';
   }
 }
 
@@ -1590,6 +1696,7 @@ function bindStaticEventListeners() {
   on($('sheet-backdrop'), 'click', closeBottomSheet);
 
   // Settings dialog bindings
+  on($('view-mode-btn'), 'click', cycleViewMode);
   on($('settings-btn'), 'click', openSettings);
   on($('settings-btn-expanded'), 'click', openSettings);
   on($('settings-close-btn'), 'click', closeSettings);
@@ -1754,9 +1861,24 @@ function _setViewMode(mode) {
   _viewMode = mode;
 }
 
+// Recalculate fit layout on window resize
+window.addEventListener('resize', function() {
+  var ds = loadDisplaySettings();
+  if ((ds.viewMode || 'auto') === 'fit') {
+    var grid = document.getElementById('session-grid');
+    if (grid) applyFitLayout(grid);
+  }
+});
+
 document.addEventListener('DOMContentLoaded', () => {
   initDeviceId();
-  applyDisplaySettings(loadDisplaySettings());
+  var _initDs = loadDisplaySettings();
+  applyDisplaySettings(_initDs);
+
+  // Initialize view mode button title
+  var vmBtn = document.getElementById('view-mode-btn');
+  if (vmBtn) vmBtn.title = 'View: ' + (_initDs.viewMode || 'auto');
+
   document.addEventListener('keydown', trackInteraction);
   document.addEventListener('click', trackInteraction);
   document.addEventListener('touchstart', trackInteraction);
@@ -1822,6 +1944,8 @@ if (typeof module !== 'undefined' && module.exports) {
     loadDisplaySettings,
     saveDisplaySettings,
     applyDisplaySettings,
+    applyFitLayout,
+    cycleViewMode,
     onDisplaySettingChange,
     openSettings,
     closeSettings,

muxplex/frontend/index.html

@@ -22,6 +22,7 @@
       <h1 class="app-wordmark"><img src="/wordmark-on-dark.svg" alt="muxplex" height="24" /></h1>
       <div class="header-actions">
         <button id="new-session-btn" class="header-btn" aria-label="New session">+</button>
+        <button id="view-mode-btn" class="header-btn" aria-label="Toggle view mode" title="View: auto">&#9638;</button>
         <button id="settings-btn" class="header-btn" aria-label="Settings">&#9881;</button>
         <span id="connection-status"></span>
       </div>

muxplex/frontend/style.css

@@ -1371,6 +1371,24 @@ body {
   z-index: 200;
 }
 
+/* ============================================================
+   Dashboard view modes — Compact and Fit
+   ============================================================ */
+
+/* Compact view — small tiles, high density */
+.session-grid--compact .session-tile {
+  height: 80px;
+}
+
+.session-grid--compact .tile-body {
+  height: 40px;
+}
+
+/* Fit view — tiles fill viewport, no scroll */
+.session-grid--fit {
+  overflow: hidden;
+}
+
 /* ============================================================
    Responsive overlay sidebar at <960px
    ============================================================ */

muxplex/frontend/tests/test_app.mjs

@@ -2118,3 +2118,91 @@ test('bindStaticEventListeners wires delete template reset button', () => {
     'bindStaticEventListeners must wire #setting-delete-template-reset click handler'
   );
 });
+
+// --- View mode cycling (Auto / Fit / Compact) ---
+
+test('app.js has VIEW_MODES array with auto, fit, compact', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  assert.ok(source.includes("'auto'"), "must include 'auto' mode");
+  assert.ok(source.includes("'fit'"), "must include 'fit' mode");
+  assert.ok(source.includes("'compact'"), "must include 'compact' mode");
+  assert.ok(source.includes('VIEW_MODES'), 'must define VIEW_MODES');
+});
+
+test('app.js exports cycleViewMode function', () => {
+  assert.ok('cycleViewMode' in app, 'app.js must export cycleViewMode');
+  assert.strictEqual(typeof app.cycleViewMode, 'function', 'cycleViewMode must be a function');
+});
+
+test('app.js exports applyFitLayout function', () => {
+  assert.ok('applyFitLayout' in app, 'app.js must export applyFitLayout');
+  assert.strictEqual(typeof app.applyFitLayout, 'function', 'applyFitLayout must be a function');
+});
+
+test('DISPLAY_DEFAULTS includes viewMode: auto', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  // DISPLAY_DEFAULTS should define viewMode
+  const defaultsStart = source.indexOf('DISPLAY_DEFAULTS');
+  assert.ok(defaultsStart !== -1, 'DISPLAY_DEFAULTS must exist');
+  const defaultsEnd = source.indexOf('};', defaultsStart);
+  const defaultsBody = source.substring(defaultsStart, defaultsEnd + 2);
+  assert.ok(defaultsBody.includes('viewMode'), 'DISPLAY_DEFAULTS must include viewMode');
+});
+
+test('applyDisplaySettings handles fit mode by adding session-grid--fit class', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  const fnStart = source.indexOf('function applyDisplaySettings(');
+  assert.ok(fnStart !== -1, 'applyDisplaySettings must exist');
+  const fnEnd = source.indexOf('\nfunction ', fnStart + 1);
+  const fnBody = source.substring(fnStart, fnEnd > fnStart ? fnEnd : fnStart + 2000);
+  assert.ok(
+    fnBody.includes('session-grid--fit'),
+    'applyDisplaySettings must apply session-grid--fit class for fit mode'
+  );
+});
+
+test('applyDisplaySettings handles compact mode by adding session-grid--compact class', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  const fnStart = source.indexOf('function applyDisplaySettings(');
+  assert.ok(fnStart !== -1, 'applyDisplaySettings must exist');
+  const fnEnd = source.indexOf('\nfunction ', fnStart + 1);
+  const fnBody = source.substring(fnStart, fnEnd > fnStart ? fnEnd : fnStart + 2000);
+  assert.ok(
+    fnBody.includes('session-grid--compact'),
+    'applyDisplaySettings must apply session-grid--compact class for compact mode'
+  );
+});
+
+test('cycleViewMode cycles through auto -> fit -> compact -> auto', () => {
+  // Reset display settings to auto
+  const ds = app.loadDisplaySettings();
+  ds.viewMode = 'auto';
+  app.saveDisplaySettings(ds);
+
+  // First cycle: auto -> fit
+  app.cycleViewMode();
+  const ds1 = app.loadDisplaySettings();
+  assert.strictEqual(ds1.viewMode, 'fit', 'first cycle should go auto -> fit');
+
+  // Second cycle: fit -> compact
+  app.cycleViewMode();
+  const ds2 = app.loadDisplaySettings();
+  assert.strictEqual(ds2.viewMode, 'compact', 'second cycle should go fit -> compact');
+
+  // Third cycle: compact -> auto
+  app.cycleViewMode();
+  const ds3 = app.loadDisplaySettings();
+  assert.strictEqual(ds3.viewMode, 'auto', 'third cycle should wrap compact -> auto');
+});
+
+test('bindStaticEventListeners wires view-mode-btn click to cycleViewMode', () => {
+  const source = fs.readFileSync(new URL('../app.js', import.meta.url), 'utf8');
+  const fnStart = source.indexOf('function bindStaticEventListeners(');
+  assert.ok(fnStart !== -1, 'bindStaticEventListeners must exist');
+  const fnEnd = source.indexOf('\nfunction ', fnStart + 1);
+  const fnBody = source.substring(fnStart, fnEnd > fnStart ? fnEnd : fnStart + 6000);
+  assert.ok(
+    fnBody.includes('view-mode-btn'),
+    'bindStaticEventListeners must wire #view-mode-btn click handler'
+  );
+});

muxplex/tests/test_frontend_css.py

@@ -1681,3 +1681,23 @@ def test_css_sidebar_footer() -> None:
     css = read_css()
     for cls in (".sidebar-footer", ".sidebar-new-btn"):
         assert cls in css, f"Missing CSS selector '{cls}'"
+
+
+def test_css_compact_view_exists() -> None:
+    """.session-grid--compact CSS modifier must exist for compact view mode."""
+    css = read_css()
+    assert ".session-grid--compact" in css, "Missing .session-grid--compact CSS selector for compact view mode"
+
+
+def test_css_fit_view_exists() -> None:
+    """.session-grid--fit CSS modifier must exist for fit view mode."""
+    css = read_css()
+    assert ".session-grid--fit" in css, "Missing .session-grid--fit CSS selector for fit view mode"
+
+
+def test_css_compact_tile_height() -> None:
+    """.session-grid--compact .session-tile must set a compact height."""
+    css = read_css()
+    assert ".session-grid--compact .session-tile" in css, (
+        "Missing .session-grid--compact .session-tile height override"
+    )

muxplex/tests/test_frontend_html.py

@@ -1153,3 +1153,16 @@ def test_html_new_session_tab_controls_with_delete() -> None:
         "setting-delete-template-reset",
     ):
         assert soup.find(id=id_), f"Missing element with id='{id_}'"
+
+
+def test_html_view_mode_button_exists() -> None:
+    """#view-mode-btn must exist in the overview header for cycling view modes."""
+    soup = _SOUP
+    btn = soup.find(id="view-mode-btn")
+    assert btn is not None, "Missing element with id='view-mode-btn' (view mode toggle button)"
+    # Must be inside the overview header area
+    overview = soup.find(id="view-overview")
+    assert overview is not None, "Missing #view-overview"
+    assert overview.find(id="view-mode-btn") is not None, (
+        "#view-mode-btn must be inside #view-overview header"
+    )