release: v0.0.14 lockstep

Bundles Phase 2 polish + the user-requested header/breadcrumb work:

- Breadcrumbs replacing the plain currentPath span. Server mode
  renders linkified ancestor segments (each <a> navigates to that
  directory; the browser fetches browse.html, the new instance
  auto-loads the listing). FS-API mode renders the rootHandle name
  as a non-link (no ancestor handles to navigate). Both prefix the
  path with a 🏠 root icon. Trailing slash + bold-current segment
  match common file-explorer conventions.

- Subdued 'Select Directory' button in server mode. Once browse is
  serving a real directory listing, the local-folder switcher is
  available but visually quiet (btn--subtle: transparent, muted
  color). FS-API mode keeps the primary styling (it's how the user
  got there). New btn--subtle CSS class added to browse's tree.css.
  A refresh button (⟳) appears next to it in both modes; clicking
  it re-fetches the current root listing.

- Header consistency: browse now matches archive's header layout
  (refresh + help buttons in addition to theme on the right). Help
  is a placeholder for future help dialog wiring.

- File preview popup. Click a file row → opens a popup window with
  the file rendered. Plain types (PDF, HTML, image) load in
  iframes; TIFF + ZIP listings via shared/preview-lib.js's
  renderTiff / renderZipListing helpers; text via <pre>; unknown
  types → 'click Download' placeholder. Modifier-click (ctrl/cmd/
  shift) and middle-click still open the file in a new tab via the
  underlying <a target=_blank>. Single popup window is reused
  across multiple file clicks (matches archive's UX).

- ZIP inline expansion. .zip files have a chevron and act like
  folders in the tree. First expand fetches the zip bytes
  (server URL or FS handle or parent-zip read), parses with JSZip
  (auto-loaded from CDN), and synthesizes the entry tree. Nested
  directories within the zip lazy-expand on demand by re-walking
  the cached entry list at the right path prefix. Click on a
  zip-entry file opens the preview popup with bytes read from
  JSZip. Recursive expand-all skips zip archives by design — they
  can be very large, and explicit click-to-expand is safer.

- Extension multi-select filter. Toolbar now has a <select
  multiple> populated with extensions present in the current
  view. Filter is OR-of-selected; combined with the name filter
  it's AND-of-both. Folders pass through (so expanding a folder
  whose name doesn't match the ext filter still shows its file
  children that do match).

browse/build.sh

@@ -30,9 +30,11 @@ concat_files \
 concat_files \
     "../shared/zddc.js" \
     "../shared/theme.js" \
+    "../shared/preview-lib.js" \
     "js/init.js" \
     "js/loader.js" \
     "js/tree.js" \
+    "js/preview.js" \
     "js/events.js" \
     "js/app.js" \
     > "$js_raw"

browse/css/tree.css

@@ -25,15 +25,55 @@
     flex-wrap: wrap;
 }
 
-.toolbar__path {
+/* Breadcrumb path. The root node is a 🏠 link to "/" (online) or
+   the FS handle name (offline). Each segment is a clickable link in
+   server mode that re-navigates the browser; in FS-API mode they
+   render as plain spans because we don't keep ancestor handles. */
+.breadcrumbs {
+    flex: 1;
+    min-width: 0;
+    overflow-x: auto;
+    overflow-y: hidden;
+    white-space: nowrap;
     font-family: Consolas, Monaco, monospace;
     font-size: 0.9rem;
     color: var(--text-muted);
-    flex: 1;
-    min-width: 0;
-    overflow: hidden;
-    text-overflow: ellipsis;
-    white-space: nowrap;
+    padding: 0.1rem 0;
+    /* Hide the scrollbar but keep horizontal scroll for very deep paths */
+    scrollbar-width: thin;
+}
+
+.breadcrumbs .bc-link {
+    color: var(--primary);
+    text-decoration: none;
+    padding: 0.1rem 0.25rem;
+    border-radius: 3px;
+}
+
+.breadcrumbs .bc-link:hover {
+    background: var(--bg-hover, rgba(0,0,0,0.05));
+    text-decoration: underline;
+}
+
+.breadcrumbs .bc-link--current {
+    color: var(--text);
+    font-weight: 500;
+    cursor: default;
+}
+
+.breadcrumbs .bc-link--current:hover {
+    background: transparent;
+    text-decoration: none;
+}
+
+.breadcrumbs .bc-sep {
+    color: var(--text-muted);
+    margin: 0 0.05rem;
+}
+
+.breadcrumbs .bc-root {
+    font-size: 1rem;       /* the 🏠 emoji renders a hair bigger */
+    line-height: 1;
 }
 
 .toolbar__filter {
@@ -47,12 +87,45 @@
     font-size: 0.9rem;
 }
 
+.toolbar__ext {
+    /* Multi-select extension filter. Native <select multiple> is
+       intentionally compact — most folders have a small set of
+       extensions, and we surface the list dynamically from the
+       loaded view. */
+    min-width: 8rem;
+    max-width: 14rem;
+    height: auto;
+    padding: 0.2rem 0.4rem;
+    border: 1px solid var(--border);
+    border-radius: 4px;
+    background: var(--bg);
+    color: var(--text);
+    font-size: 0.85rem;
+    font-family: Consolas, Monaco, monospace;
+}
+
 .toolbar__count {
     font-size: 0.8rem;
     color: var(--text-muted);
     white-space: nowrap;
 }
 
+/* Subtle button variant — used for "Select Directory" when the page
+   is server-backed (the user usually doesn't need to switch to a
+   local folder; we keep the option visible but quiet). */
+.btn.btn--subtle {
+    background: transparent;
+    color: var(--text-muted);
+    border-color: var(--border);
+    box-shadow: none;
+    font-weight: normal;
+}
+
+.btn.btn--subtle:hover {
+    color: var(--text);
+    background: var(--bg-hover, rgba(0,0,0,0.04));
+}
+
 /* Table — folders + files in a tree */
 
 .browse-table {

browse/js/app.js

@@ -19,7 +19,6 @@
         if (detected) {
             tree.setRoot(detected.entries);
             events.showBrowseRoot();
-            document.getElementById('currentPath').textContent = detected.path;
             tree.render();
             events.statusInfo('Loaded ' + detected.entries.length + ' item'
                 + (detected.entries.length === 1 ? '' : 's')

browse/js/events.js

@@ -6,6 +6,9 @@
     var state = window.app.state;
     var tree = window.app.modules.tree;
     var loader = window.app.modules.loader;
+    // preview module is loaded later (concat order); look it up at
+    // call time, not at IIFE-eval time.
+    function previewMod() { return window.app.modules.preview; }
 
     function status(msg, kind) {
         var el = document.getElementById('statusBar');
@@ -44,7 +47,6 @@
         }
         tree.setRoot(raw);
         showBrowseRoot();
-        document.getElementById('currentPath').textContent = state.currentPath;
         tree.render();
         statusInfo('Loaded ' + raw.length + ' item' + (raw.length === 1 ? '' : 's'));
     }
@@ -54,6 +56,62 @@
         var root = document.getElementById('browseRoot');
         if (empty) empty.classList.add('hidden');
         if (root) root.classList.remove('hidden');
+        applySourceUI();
+    }
+
+    // Visual state of the "Select Directory" button + the refresh
+    // button depends on the source. In server mode the user is
+    // already viewing a server-backed listing — Select Directory
+    // becomes a quiet "switch to local" affordance (subtle styling),
+    // and the refresh button is shown. In FS mode the button is
+    // primary (it's how you got here) and refresh is hidden (the
+    // listing was already a fresh enumeration).
+    function applySourceUI() {
+        var add = document.getElementById('addDirectoryBtn');
+        var refresh = document.getElementById('refreshHeaderBtn');
+        if (add) {
+            if (state.source === 'server') {
+                add.classList.remove('btn-primary');
+                add.classList.add('btn--subtle');
+            } else {
+                add.classList.add('btn-primary');
+                add.classList.remove('btn--subtle');
+            }
+        }
+        if (refresh) {
+            if (state.source) {
+                refresh.classList.remove('hidden');
+            } else {
+                refresh.classList.add('hidden');
+            }
+        }
+    }
+
+    async function refreshListing() {
+        if (state.source === 'server') {
+            var raw;
+            try {
+                raw = await loader.fetchServerChildren(state.currentPath);
+            } catch (e) {
+                statusError('Refresh failed: ' + e.message);
+                return;
+            }
+            tree.setRoot(raw);
+            tree.render();
+            statusInfo('Refreshed (' + raw.length + ' item'
+                + (raw.length === 1 ? '' : 's') + ')');
+        } else if (state.source === 'fs' && state.rootHandle) {
+            var raw2;
+            try {
+                raw2 = await loader.fetchFsChildren(state.rootHandle);
+            } catch (e) {
+                statusError('Refresh failed: ' + e.message);
+                return;
+            }
+            tree.setRoot(raw2);
+            tree.render();
+            statusInfo('Refreshed');
+        }
     }
 
     function init() {
@@ -61,6 +119,9 @@
         var btn = document.getElementById('addDirectoryBtn');
         if (btn) btn.addEventListener('click', pickLocalDir);
 
+        var refresh = document.getElementById('refreshHeaderBtn');
+        if (refresh) refresh.addEventListener('click', refreshListing);
+
         // Filter input
         var filter = document.getElementById('filterInput');
         if (filter) {
@@ -69,6 +130,18 @@
             });
         }
 
+        // Extension multi-select
+        var extSel = document.getElementById('extFilter');
+        if (extSel) {
+            extSel.addEventListener('change', function () {
+                var picked = [];
+                for (var i = 0; i < extSel.options.length; i++) {
+                    if (extSel.options[i].selected) picked.push(extSel.options[i].value);
+                }
+                tree.setExtFilter(picked);
+            });
+        }
+
         // Sort headers
         var ths = document.querySelectorAll('#browseTable thead th.sortable');
         for (var i = 0; i < ths.length; i++) {
@@ -96,20 +169,45 @@
             tbody.addEventListener('click', function (e) {
                 var row = e.target.closest('tr.tree-row');
                 if (!row) return;
-                var isDir = row.dataset.isdir === 'true';
-                if (!isDir) return;
-                e.preventDefault();
                 var id = parseInt(row.dataset.id, 10);
-                if (e.shiftKey || e.altKey) {
                 var node = state.nodes.get(id);
-                    if (node && node.expanded) {
-                        tree.collapseSubtree(id);
-                    } else {
-                        tree.expandSubtree(id);
-                    }
+                if (!node) return;
+
+                var isExpandable = row.dataset.isdir === 'true' || row.dataset.iszip === 'true';
+                var clickedChevron = !!e.target.closest('.tree-name__chevron');
+
+                if (isExpandable) {
+                    // For folders + zips: click anywhere on the row
+                    // toggles. Modifier-click → recursive expand.
+                    e.preventDefault();
+                    if (e.shiftKey || e.altKey) {
+                        if (node.expanded) tree.collapseSubtree(id);
+                        else tree.expandSubtree(id);
                     } else {
                         tree.toggleFolder(id);
                     }
+                    return;
+                }
+
+                // Plain file row.
+                // Modifier-click (ctrl/cmd) and middle-click → fall
+                // through to the <a> tag's natural target=_blank
+                // behavior (open in new tab). For server-backed
+                // files, that opens the real URL via zddc-server.
+                if (e.ctrlKey || e.metaKey || e.shiftKey || e.button === 1) {
+                    return;
+                }
+                // Plain click → preview popup. Intercept default nav.
+                e.preventDefault();
+                var p = previewMod();
+                if (p) p.showFilePreview(node);
+            });
+
+            // Middle-click (auxclick) — same fall-through logic.
+            tbody.addEventListener('auxclick', function (e) {
+                if (e.button !== 1) return; // middle only
+                // Browser handles target=_blank natively for middle
+                // click; don't preventDefault, just don't intercept.
             });
         }
     }

browse/js/init.js

@@ -28,13 +28,28 @@
         // Current filter substring (lowercase).
         filterText: '',
 
+        // Selected extensions (Set of lowercase strings, no leading
+        // dot). Empty set = no extension filtering.
+        extFilter: new Set(),
+
         // The tree's in-memory representation. Each node:
         //   { id, name, isDir, size, modTime, ext, url, depth,
-        //     parentId, expanded, loaded, childIds }
+        //     parentId, expanded, loaded, childIds, isZip, zipFile,
+        //     zipPath }
+        // - isZip:   set when the node IS a .zip file we know how to
+        //            expand inline (server file or FS handle).
+        // - zipFile: cached JSZip instance for this archive (set
+        //            after first expand).
+        // - zipPath: relative path WITHIN a zip (set on virtual
+        //            children of an expanded zip; null otherwise).
         // Stored flat in a Map keyed by id; render order derived
         // from a depth-first walk.
         nodes: new Map(),
         rootIds: [],
-        nextId: 1
+        nextId: 1,
+
+        // Single shared popup window for file preview (across
+        // multiple file clicks). Same pattern as archive's preview.
+        previewWindow: null
     };
 })();

browse/js/loader.js

@@ -120,11 +120,35 @@
         }
     }
 
+    // CDN library loader. Idempotent — multiple callers share the
+    // same in-flight Promise. Used by ZIP expansion + the file
+    // preview popup.
+    var libCache = new Map();
+    function loadScript(url) {
+        if (libCache.has(url)) return libCache.get(url);
+        var p = new Promise(function (resolve, reject) {
+            var s = document.createElement('script');
+            s.src = url;
+            s.onload = function () { resolve(); };
+            s.onerror = function () { reject(new Error('Failed to load: ' + url)); };
+            document.head.appendChild(s);
+        });
+        libCache.set(url, p);
+        return p;
+    }
+
+    function ensureJSZip() {
+        if (window.JSZip) return Promise.resolve();
+        return loadScript('https://cdn.jsdelivr.net/npm/jszip@3/dist/jszip.min.js');
+    }
+
     // Public API
     window.app.modules.loader = {
         fetchServerChildren: fetchServerChildren,
         fetchFsChildren: fetchFsChildren,
         autoDetectServerMode: autoDetectServerMode,
-        splitExt: splitExt
+        splitExt: splitExt,
+        ensureJSZip: ensureJSZip,
+        loadScript: loadScript
     };
 })();

browse/js/preview.js

@@ -0,0 +1,239 @@
+// preview.js — file preview popup. Reuses shared/preview-lib.js for
+// TIFF, ZIP listing, and image-rendering helpers; native iframe for
+// PDF and HTML; <pre> for text; download button for everything else.
+//
+// Lifecycle: a single popup window is reused across multiple file
+// clicks (state.previewWindow). Subsequent clicks rewrite its
+// contents instead of spawning a new window — same UX as the archive
+// tool.
+(function () {
+    'use strict';
+
+    var state = window.app.state;
+    var loader = window.app.modules.loader;
+    var preview = window.zddc && window.zddc.preview;
+    if (!preview) {
+        // shared/preview-lib.js wasn't concatenated in. Bail loudly so
+        // the bug shows up in console rather than mysteriously failing.
+        console.error('[browse] zddc.preview not loaded — preview popup disabled.');
+    }
+
+    function escapeHtml(s) {
+        return String(s).replace(/&/g, '&amp;').replace(/</g, '&lt;')
+            .replace(/>/g, '&gt;').replace(/"/g, '&quot;');
+    }
+
+    var MIME = {
+        'pdf': 'application/pdf',
+        'html': 'text/html', 'htm': 'text/html',
+        'jpg': 'image/jpeg', 'jpeg': 'image/jpeg', 'png': 'image/png',
+        'gif': 'image/gif', 'webp': 'image/webp', 'svg': 'image/svg+xml',
+        'tif': 'image/tiff', 'tiff': 'image/tiff',
+        'zip': 'application/zip',
+        'txt': 'text/plain', 'md': 'text/markdown', 'json': 'application/json',
+        'xml': 'application/xml', 'csv': 'text/csv', 'log': 'text/plain',
+        'js': 'text/javascript', 'css': 'text/css'
+    };
+
+    // Pull bytes for a file node. Three sources:
+    //   - server URL (zddc-server-backed file, including downloads
+    //     of archived files served at real paths)
+    //   - FS-API handle (local folder)
+    //   - JSZip entry (file inside an expanded zip; reads from
+    //     parent's cached JSZip instance)
+    async function getArrayBuffer(node) {
+        if (node.zipParentId != null) {
+            var owner = state.nodes.get(node.zipParentId);
+            if (!owner || !owner.zipFile) {
+                throw new Error('parent zip not loaded');
+            }
+            return await owner.zipFile.file(node.zipPath).async('arraybuffer');
+        }
+        if (state.source === 'server' && node.url) {
+            var resp = await fetch(node.url);
+            if (!resp.ok) throw new Error('HTTP ' + resp.status);
+            return await resp.arrayBuffer();
+        }
+        if (node.handle) {
+            var f = await node.handle.getFile();
+            return await f.arrayBuffer();
+        }
+        throw new Error('no source for file');
+    }
+
+    function getMime(ext) {
+        return MIME[ext] || 'application/octet-stream';
+    }
+
+    // Build a blob URL for the file's bytes. For server-mode regular
+    // files (not in a zip), prefer the live URL — relative links and
+    // server-side interception (e.g. .archive resolution) work then.
+    async function getBlobUrl(node) {
+        if (state.source === 'server' && node.url && node.zipParentId == null) {
+            return { url: node.url, fromServer: true };
+        }
+        var buf = await getArrayBuffer(node);
+        var blob = new Blob([buf], { type: getMime(node.ext) });
+        return { url: URL.createObjectURL(blob), fromServer: false };
+    }
+
+    function popupShell(node, primaryUrl) {
+        var safeName = escapeHtml(node.name);
+        var safeHref = escapeHtml(primaryUrl);
+        var ext = (node.ext || '').toLowerCase();
+        // Inline PDF and HTML previews load in iframes. HTML uses
+        // sandbox="allow-same-origin allow-popups
+        // allow-popups-to-escape-sandbox" — same posture as archive's
+        // preview: links navigate, scripts blocked, popups allowed.
+        var contentHtml;
+        if (ext === 'pdf') {
+            contentHtml = '<iframe src="' + safeHref + '"></iframe>';
+        } else if (ext === 'html' || ext === 'htm') {
+            contentHtml = '<iframe src="' + safeHref + '" sandbox="allow-same-origin allow-popups allow-popups-to-escape-sandbox"></iframe>';
+        } else if (preview && preview.isImage(ext) && !preview.isTiff(ext)) {
+            contentHtml = '<img class="preview-image" src="' + safeHref + '" alt="' + safeName + '">';
+        } else {
+            contentHtml = '<div id="previewContent"><div class="loading">Loading preview…</div></div>';
+        }
+        return '<!DOCTYPE html><html><head><meta charset="UTF-8">'
+            + '<title>' + safeName + ' — preview</title><style>'
+            + '*{margin:0;padding:0;box-sizing:border-box;}'
+            + 'body{display:flex;flex-direction:column;height:100vh;'
+            + 'font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,sans-serif;}'
+            + '.toolbar{display:flex;align-items:center;gap:.5rem;padding:.5rem 1rem;'
+            + 'background:#f5f5f5;border-bottom:1px solid #ddd;}'
+            + '.toolbar h1{flex:1;font-size:.95rem;font-weight:500;overflow:hidden;'
+            + 'text-overflow:ellipsis;white-space:nowrap;}'
+            + '.btn{padding:.4rem .8rem;font-size:.85rem;border:1px solid #ccc;'
+            + 'border-radius:4px;background:white;cursor:pointer;}'
+            + '.btn:hover{background:#e8e8e8;}'
+            + 'iframe{flex:1;width:100%;border:none;}'
+            + '#previewContent{flex:1;overflow:auto;display:flex;flex-direction:column;}'
+            + '.loading{display:flex;align-items:center;justify-content:center;height:100%;'
+            + 'color:#666;font-size:1.1rem;}'
+            + 'img.preview-image{max-width:100%;max-height:100%;object-fit:contain;'
+            + 'margin:auto;display:block;}'
+            + 'pre.preview-text{padding:1rem;font-family:Consolas,Monaco,monospace;'
+            + 'font-size:.85rem;white-space:pre-wrap;word-wrap:break-word;}'
+            + '</style></head><body>'
+            + '<div class="toolbar"><h1>' + safeName + '</h1>'
+            + '<button class="btn" onclick="downloadFile()">Download</button></div>'
+            + contentHtml
+            + '<script>'
+            + 'var blobUrl=' + JSON.stringify(primaryUrl) + ';'
+            + 'var fileName=' + JSON.stringify(node.name) + ';'
+            + 'function downloadFile(){var a=document.createElement("a");'
+            + 'a.href=blobUrl;a.download=fileName;document.body.appendChild(a);'
+            + 'a.click();document.body.removeChild(a);}'
+            + '</' + 'script></body></html>';
+    }
+
+    async function renderTextInWindow(node, win) {
+        var c = win.document.getElementById('previewContent');
+        if (!c) return;
+        try {
+            var buf = await getArrayBuffer(node);
+            var text = new TextDecoder('utf-8', { fatal: false }).decode(buf);
+            var MAX = 200000;
+            if (text.length > MAX) {
+                text = text.substring(0, MAX) + '\n\n... (truncated, '
+                    + (text.length - MAX) + ' more chars — Download for full file)';
+            }
+            var pre = win.document.createElement('pre');
+            pre.className = 'preview-text';
+            pre.textContent = text;
+            c.innerHTML = '';
+            c.appendChild(pre);
+        } catch (e) {
+            c.innerHTML = '<div class="loading">Error: ' + escapeHtml(e.message || e) + '</div>';
+        }
+    }
+
+    async function renderTiffInWindow(node, win) {
+        var c = win.document.getElementById('previewContent');
+        if (!c || !preview) return;
+        try {
+            var buf = await getArrayBuffer(node);
+            await preview.renderTiff(win.document, c, buf, { fileName: node.name });
+        } catch (e) {
+            c.innerHTML = '<div class="loading">Error rendering TIFF: '
+                + escapeHtml(e.message || e) + '</div>';
+        }
+    }
+
+    async function renderZipInWindow(node, win) {
+        var c = win.document.getElementById('previewContent');
+        if (!c || !preview) return;
+        try {
+            var buf = await getArrayBuffer(node);
+            await preview.renderZipListing(win.document, c, buf, { fileName: node.name });
+        } catch (e) {
+            c.innerHTML = '<div class="loading">Error reading ZIP: '
+                + escapeHtml(e.message || e) + '</div>';
+        }
+    }
+
+    async function showFilePreview(node) {
+        if (node.isDir) return;
+
+        var ext = (node.ext || '').toLowerCase();
+        var info;
+        try {
+            info = await getBlobUrl(node);
+        } catch (e) {
+            window.app.modules.events.statusError('Preview failed: ' + e.message);
+            return;
+        }
+        var html = popupShell(node, info.url);
+
+        var win = state.previewWindow;
+        if (win && !win.closed) {
+            win.document.open();
+            win.document.write(html);
+            win.document.close();
+            win.focus();
+        } else {
+            var w = Math.round(screen.width * 0.6);
+            var h = Math.round(screen.height * 0.8);
+            var left = Math.round((screen.width - w) / 2);
+            var top = Math.round((screen.height - h) / 2);
+            win = window.open('', 'browseFilePreview',
+                'width=' + w + ',height=' + h + ',left=' + left + ',top=' + top
+                + ',resizable=yes,scrollbars=yes');
+            if (!win) {
+                // Popup blocked — fall back to opening the file directly.
+                window.open(info.url, '_blank', 'noopener');
+                return;
+            }
+            win.document.write(html);
+            win.document.close();
+            win.focus();
+            state.previewWindow = win;
+        }
+
+        // Async content rendering for the non-iframe types.
+        if (ext === 'pdf' || ext === 'html' || ext === 'htm') {
+            return; // iframe wired in popupShell
+        }
+        if (preview && preview.isImage(ext) && !preview.isTiff(ext)) {
+            return; // <img> wired in popupShell
+        }
+        if (preview && preview.isTiff(ext)) {
+            await renderTiffInWindow(node, win);
+        } else if (preview && preview.isZip(ext)) {
+            await renderZipInWindow(node, win);
+        } else if (preview && preview.isText(ext)) {
+            await renderTextInWindow(node, win);
+        } else {
+            // Unknown type — show a friendly "no preview, click
+            // download" placeholder.
+            var c = win.document.getElementById('previewContent');
+            if (c) {
+                c.innerHTML = '<div class="loading">No inline preview for .'
+                    + escapeHtml(ext) + ' — click Download.</div>';
+            }
+        }
+    }
+
+    window.app.modules.preview = { showFilePreview: showFilePreview };
+})();

browse/js/tree.js

@@ -14,6 +14,10 @@
 
     function newNode(raw, parentId, depth) {
         var id = state.nextId++;
+        // ZIP files are treated as folders for tree purposes — the
+        // chevron lets the user expand them inline. The actual
+        // contents are loaded on first expand via JSZip.
+        var isZip = !raw.isDir && raw.ext === 'zip';
         var node = {
             id: id,
             name: raw.name,
@@ -27,7 +31,11 @@
             parentId: parentId,
             expanded: false,
             loaded: false,
-            childIds: []
+            childIds: [],
+            isZip: isZip,
+            zipFile: null,           // cached JSZip instance
+            zipPath: raw.zipPath || null,  // path within zip (for virtual children)
+            zipParentId: raw.zipParentId || null  // ancestor zip's node id (for nested entries)
         };
         state.nodes.set(id, node);
         return node;
@@ -101,14 +109,14 @@
             for (var i = 0; i < ids.length; i++) {
                 out.push(ids[i]);
                 var n = state.nodes.get(ids[i]);
-                if (n.isDir && n.expanded) walk(n.childIds);
+                if ((n.isDir || n.isZip) && n.expanded) walk(n.childIds);
             }
         }
         // Re-sort everything at all levels so a sort change reorders
         // already-loaded children consistently.
         sortNodes(state.rootIds);
         state.nodes.forEach(function (n) {
-            if (n.isDir && n.loaded) sortNodes(n.childIds);
+            if ((n.isDir || n.isZip) && n.loaded) sortNodes(n.childIds);
         });
         walk(state.rootIds);
         return out;
@@ -138,17 +146,20 @@
 
     function rowHtml(node) {
         var indent = node.depth * 1.2;
-        var iconChar = node.isDir ? '📁' : '📄';
-        var labelClass = node.isDir ? 'is-folder' : 'is-file';
-        var chevronClass = 'tree-name__chevron' + (node.isDir ? '' : ' tree-name__chevron--leaf');
+        var expandable = node.isDir || node.isZip;
+        var iconChar = node.isDir ? '📁' : (node.isZip ? '🗜️' : '📄');
+        var chevronClass = 'tree-name__chevron'
+            + (expandable ? '' : ' tree-name__chevron--leaf');
         var nameInner;
         if (node.isDir) {
             nameInner = '<span class="tree-name__label is-folder">'
                 + escapeHtml(node.name) + '</span>';
         } else {
-            // File: clickable link. In server mode, href is a real URL
-            // that opens the file. In FS mode, click handler reads the
-            // file via the handle and triggers a download (Phase 2).
+            // File / zip: clickable. Plain click → preview popup.
+            // Modifier-click (ctrl/cmd) and middle-click → open in
+            // new tab (browser default for the href). Server mode
+            // gets the real URL (so right-click → save-link-as also
+            // works); FS mode and zip-virtual children get '#'.
             var href = node.url || '#';
             nameInner = '<a class="tree-name__label is-file"'
                 + ' href="' + escapeHtml(href) + '"'
@@ -156,7 +167,9 @@
         }
         return ''
             + '<tr class="tree-row ' + (node.expanded ? 'expanded' : '')
-                + '" data-id="' + node.id + '" data-isdir="' + node.isDir + '">'
+                + '" data-id="' + node.id
+                + '" data-isdir="' + node.isDir
+                + '" data-iszip="' + node.isZip + '">'
             + '<td class="col-name">'
                 + '<span class="tree-name">'
                     + '<span class="tree-name__indent" style="width:' + indent + 'rem;"></span>'
@@ -183,19 +196,24 @@
         applyFilter();
         updateCount();
         updateSortHeaders();
+        renderBreadcrumbs();
+        renderExtFilter();
     }
 
-    // Filter is purely DOM-level: hide rows whose name doesn't match.
+    // Filter is purely DOM-level: hide rows whose name doesn't match
+    // and (if any extensions are selected) whose ext isn't in the set.
     // Cheap, immediate, no model rebuild.
     function applyFilter() {
         var f = state.filterText;
+        var ef = state.extFilter;
         var rows = document.querySelectorAll('#browseTbody tr.tree-row');
         for (var i = 0; i < rows.length; i++) {
             var row = rows[i];
             var n = state.nodes.get(parseInt(row.dataset.id, 10));
             if (!n) continue;
-            var match = !f || n.name.toLowerCase().indexOf(f) !== -1;
-            row.classList.toggle('tree-row--filtered', !match);
+            var nameMatch = !f || n.name.toLowerCase().indexOf(f) !== -1;
+            var extMatch = !ef.size || n.isDir || ef.has(n.ext);
+            row.classList.toggle('tree-row--filtered', !(nameMatch && extMatch));
         }
     }
 
@@ -204,11 +222,81 @@
         if (!el) return;
         var rows = document.querySelectorAll('#browseTbody tr.tree-row:not(.tree-row--filtered)');
         var total = document.querySelectorAll('#browseTbody tr.tree-row').length;
-        el.textContent = state.filterText
+        var anyFilter = state.filterText || state.extFilter.size;
+        el.textContent = anyFilter
             ? rows.length + ' of ' + total + ' shown'
             : total + ' item' + (total === 1 ? '' : 's');
     }
 
+    // ── Breadcrumbs ──────────────────────────────────────────────────────
+
+    function renderBreadcrumbs() {
+        var el = document.getElementById('breadcrumbs');
+        if (!el) return;
+        var html = '';
+        if (state.source === 'server') {
+            // Server mode: every segment links to its directory URL.
+            // The browser navigates → server returns embedded browse →
+            // the new instance auto-loads that directory's listing.
+            var path = state.currentPath || '/';
+            var parts = path.split('/').filter(Boolean);
+            html += '<a class="bc-link bc-root" href="/" title="Site root">🏠</a>';
+            var sofar = '';
+            for (var i = 0; i < parts.length; i++) {
+                sofar += '/' + parts[i];
+                var isLast = i === parts.length - 1;
+                html += '<span class="bc-sep">/</span>';
+                if (isLast) {
+                    html += '<span class="bc-link bc-link--current">'
+                        + escapeHtml(parts[i]) + '</span>';
+                } else {
+                    html += '<a class="bc-link" href="' + escapeHtml(sofar + '/') + '">'
+                        + escapeHtml(parts[i]) + '</a>';
+                }
+            }
+            html += '<span class="bc-sep">/</span>';
+        } else if (state.source === 'fs') {
+            // FS-API mode: ancestor handles weren't retained when the
+            // user picked the root, so we can't navigate up. Show the
+            // root as 🏠 + handle name without links.
+            var name = state.rootHandle ? state.rootHandle.name : '';
+            html += '<span class="bc-link bc-root" title="Local directory">🏠</span>';
+            if (name) {
+                html += '<span class="bc-sep">/</span>';
+                html += '<span class="bc-link bc-link--current">' + escapeHtml(name) + '</span>';
+            }
+            html += '<span class="bc-sep">/</span>';
+        }
+        el.innerHTML = html;
+    }
+
+    // ── Extension filter ─────────────────────────────────────────────────
+
+    function renderExtFilter() {
+        var sel = document.getElementById('extFilter');
+        if (!sel) return;
+        // Collect unique extensions from currently-loaded nodes (any
+        // depth). Folders excluded. Empty-string ext omitted (no-ext
+        // files would be filtered out by selecting any other ext).
+        var exts = new Set();
+        state.nodes.forEach(function (n) {
+            if (!n.isDir && n.ext) exts.add(n.ext);
+        });
+        var sorted = Array.from(exts).sort();
+        // Preserve current selection when re-rendering after expand.
+        var selected = state.extFilter;
+        var html = '';
+        for (var i = 0; i < sorted.length; i++) {
+            var e = sorted[i];
+            var isSel = selected.has(e) ? ' selected' : '';
+            html += '<option value="' + escapeHtml(e) + '"' + isSel + '>'
+                + escapeHtml(e) + '</option>';
+        }
+        sel.innerHTML = html;
+        // Size to fit content — multi-selects can be cramped otherwise.
+        sel.size = Math.min(Math.max(sorted.length, 2), 6);
+    }
+
     function updateSortHeaders() {
         var ths = document.querySelectorAll('#browseTable thead th.sortable');
         for (var i = 0; i < ths.length; i++) {
@@ -219,10 +307,29 @@
         }
     }
 
-    // Load a folder's children (lazy; idempotent re-loads).
+    // Load a folder's children (lazy; idempotent re-loads). Dispatches
+    // by node kind:
+    //   - regular folder → server JSON listing OR FS-API enumeration
+    //   - zip file       → fetch+JSZip; entries become virtual children
+    //   - zip child dir  → already-listed entries from the parent zip
+    //                       (zips are enumerated whole, so child dirs
+    //                       are pre-populated when the zip expands)
     async function loadChildren(node) {
         if (node.loaded) return;
         try {
+            if (node.isZip) {
+                await loadZipChildren(node);
+            } else if (node._zipSyntheticDir) {
+                // Synthetic dir node materialized when a zip's entry
+                // list referenced "a/b/file" but had no "a/" entry.
+                // Re-walk the owning zip's flat entry list with the
+                // dir's full prefix.
+                var owner = state.nodes.get(node.zipParentId);
+                if (!owner || !owner.zipEntries) {
+                    throw new Error('zip parent not loaded');
+                }
+                setZipDirChildren(node, owner, node.zipPath + '/');
+            } else if (node.isDir) {
                 var raw;
                 if (state.source === 'server') {
                     raw = await loader.fetchServerChildren(pathFor(node) + '/');
@@ -232,16 +339,131 @@
                     return;
                 }
                 setChildren(node.id, raw);
+            }
         } catch (e) {
             window.app.modules.events.statusError(
                 'Failed to load ' + node.name + ': ' + e.message);
         }
     }
 
+    // Fetch a zip's bytes, parse with JSZip, and materialize its
+    // entries as a tree of virtual nodes. JSZip's entry list is flat
+    // (full paths); we reconstruct the directory hierarchy on top.
+    async function loadZipChildren(zipNode) {
+        await loader.ensureJSZip();
+        var arrayBuffer;
+        if (state.source === 'server' && zipNode.url) {
+            var resp = await fetch(zipNode.url);
+            if (!resp.ok) throw new Error('HTTP ' + resp.status + ' fetching ' + zipNode.url);
+            arrayBuffer = await resp.arrayBuffer();
+        } else if (zipNode.handle) {
+            // FS-API: top-level zip in a local folder.
+            var f = await zipNode.handle.getFile();
+            arrayBuffer = await f.arrayBuffer();
+        } else if (zipNode.zipParentId != null) {
+            // Nested zip inside another zip — read from parent JSZip.
+            var parent = state.nodes.get(zipNode.zipParentId);
+            if (!parent || !parent.zipFile) {
+                throw new Error('parent zip not loaded');
+            }
+            arrayBuffer = await parent.zipFile.file(zipNode.zipPath).async('arraybuffer');
+        } else {
+            throw new Error('cannot fetch zip bytes (no source)');
+        }
+        var zip = await window.JSZip.loadAsync(arrayBuffer);
+        zipNode.zipFile = zip;
+
+        // Build a path → raw-entry map. Entry paths are
+        // "dir/sub/file.ext" or "dir/" for directories. We slice
+        // to immediate children of zipNode (i.e. zero slashes after
+        // a leading prefix). For nested directories, we synthesize
+        // folder nodes that lazy-expand to the next level via the
+        // same raw-entry list — keep it on the zipNode for replay.
+        zipNode.zipEntries = []; // for re-walk on expand of subdirs
+        zip.forEach(function (relPath, entry) {
+            zipNode.zipEntries.push({
+                path: relPath.replace(/\/$/, ''),
+                isDir: entry.dir,
+                size: (entry._data && entry._data.uncompressedSize) || 0,
+                modTime: entry.date instanceof Date ? entry.date : null,
+                rawPath: relPath
+            });
+        });
+
+        // Now seed top-level children of the zip itself.
+        setZipDirChildren(zipNode, zipNode, '');
+    }
+
+    // Populate node's childIds with the entries directly under
+    // pathPrefix (relative to the owning zip). Directory entries
+    // become folder nodes whose own children are seeded on first
+    // expand by this same function (recursively descending zipPath).
+    function setZipDirChildren(node, zipOwner, pathPrefix) {
+        var seen = new Map(); // immediate child name → raw entry
+        zipOwner.zipEntries.forEach(function (e) {
+            if (!e.path.startsWith(pathPrefix)) return;
+            var rest = e.path.substring(pathPrefix.length);
+            if (rest === '') return;
+            // Take the FIRST segment of the remaining path
+            var slash = rest.indexOf('/');
+            var firstSeg = slash === -1 ? rest : rest.substring(0, slash);
+            var isImmediateFile = !e.isDir && slash === -1;
+            var isImmediateDir = e.isDir && slash === -1;
+            // For deeply-nested entries (rest contains a slash), we
+            // surface only the first segment as a synthetic folder
+            // entry. For immediate entries, we emit the entry as-is.
+            if (isImmediateFile || isImmediateDir) {
+                // Immediate entry — use the real metadata.
+                seen.set(firstSeg, {
+                    name: firstSeg,
+                    isDir: e.isDir,
+                    size: e.size,
+                    modTime: e.modTime,
+                    ext: e.isDir ? '' : loader.splitExt(firstSeg),
+                    url: null,
+                    handle: null,
+                    zipPath: e.path,
+                    zipParentId: zipOwner.id
+                });
+            } else if (slash !== -1 && !seen.has(firstSeg)) {
+                // Deeper entry, no explicit dir entry yet — synthesize.
+                seen.set(firstSeg, {
+                    name: firstSeg,
+                    isDir: true,
+                    size: 0,
+                    modTime: null,
+                    ext: '',
+                    url: null,
+                    handle: null,
+                    zipPath: pathPrefix + firstSeg,
+                    zipParentId: zipOwner.id
+                });
+            }
+        });
+        // Drop existing children (re-load case)
+        node.childIds.forEach(function (id) { state.nodes.delete(id); });
+        node.childIds = [];
+        seen.forEach(function (raw) {
+            var n = newNode(raw, node.id, node.depth + 1);
+            // Synthetic dir nodes inside zip don't have a dedicated
+            // load path — they re-walk zipEntries on expand. Mark
+            // them so the dispatcher knows.
+            if (raw.isDir && !n.isZip) {
+                n._zipSyntheticDir = true;
+            }
+            node.childIds.push(n.id);
+        });
+        sortNodes(node.childIds);
+        node.loaded = true;
+    }
+
     // Toggle a folder's expanded state. Loads children on first expand.
+    // Treats "expandable" as either a real directory OR a zip file
+    // (zip files act like folders for tree purposes — the chevron
+    // expands them and the contents come from JSZip).
     async function toggleFolder(nodeId) {
         var n = state.nodes.get(nodeId);
-        if (!n || !n.isDir) return;
+        if (!n || !(n.isDir || n.isZip)) return;
         if (!n.expanded && !n.loaded) {
             await loadChildren(n);
             if (!n.loaded) return; // load failed
@@ -253,16 +475,12 @@
     // Recursive expand: load + expand all descendants of nodeId. Used
     // for Shift-click on a folder. Walks breadth-first, fanning out
     // through children, grand-children, etc. until every reachable
-    // folder is loaded and marked expanded. Status bar shows progress
-    // because deeply-nested trees can take a while.
-    //
-    // Parallelism: kept conservative (per-level fan-out) to avoid
-    // hammering zddc-server with hundreds of concurrent listing
-    // fetches. Browsers also throttle per-origin concurrency, but
-    // queuing politely is friendlier than fighting that.
+    // expandable node (folder OR zip) is loaded and marked expanded.
+    // Skips zip-EXPANSION recursion to avoid auto-loading every
+    // archive in the tree (those can be huge); plain folders only.
     async function expandSubtree(nodeId) {
         var root = state.nodes.get(nodeId);
-        if (!root || !root.isDir) return;
+        if (!root || !(root.isDir || root.isZip)) return;
         var status = window.app.modules.events.statusInfo;
         status('Expanding subtree…');
         var processed = 0;
@@ -270,7 +488,6 @@
         while (queue.length) {
             var batch = queue;
             queue = [];
-            // Load this level's children in parallel (Promise.all).
             await Promise.all(batch.map(function (n) { return loadChildren(n); }));
             for (var i = 0; i < batch.length; i++) {
                 var n = batch[i];
@@ -278,28 +495,26 @@
                 processed++;
                 for (var j = 0; j < n.childIds.length; j++) {
                     var c = state.nodes.get(n.childIds[j]);
-                    if (c && c.isDir) queue.push(c);
+                    // Recurse into plain folders only — don't auto-
+                    // expand zip archives during a subtree expand
+                    // (they can be very large).
+                    if (c && c.isDir && !c.isZip) queue.push(c);
                 }
             }
-            // Re-render after each level so the user sees progress
-            // rather than a long pause then a sudden full-tree dump.
             render();
             status('Expanding subtree… (' + processed + ' folders loaded)');
         }
         status('Expanded ' + processed + ' folder' + (processed === 1 ? '' : 's'));
     }
 
-    // Recursive collapse: mark this node and every descendant as
-    // collapsed. Doesn't unload — if the user re-expands later, the
-    // children are still in memory and re-render is instant.
     function collapseSubtree(nodeId) {
         var root = state.nodes.get(nodeId);
-        if (!root || !root.isDir) return;
+        if (!root || !(root.isDir || root.isZip)) return;
         function walk(n) {
             n.expanded = false;
             for (var i = 0; i < n.childIds.length; i++) {
                 var c = state.nodes.get(n.childIds[i]);
-                if (c && c.isDir) walk(c);
+                if (c && (c.isDir || c.isZip)) walk(c);
             }
         }
         walk(root);
@@ -344,6 +559,13 @@
             applyFilter();
             updateCount();
         },
+        setExtFilter: function (extArr) {
+            state.extFilter = new Set((extArr || []).map(function (e) {
+                return String(e).toLowerCase().replace(/^\./, '');
+            }));
+            applyFilter();
+            updateCount();
+        },
         pathFor: pathFor
     };
 })();

browse/template.html

@@ -25,9 +25,11 @@
                 <span class="build-timestamp">{{BUILD_LABEL}}</span>
             </div>
             <button id="addDirectoryBtn" class="btn btn-primary">Select Directory</button>
+            <button id="refreshHeaderBtn" class="btn btn-secondary hidden" title="Refresh listing" aria-label="Refresh listing">⟳</button>
         </div>
         <div class="header-right">
             <button id="theme-btn" class="btn btn-secondary" title="Theme: auto (follows OS)" aria-label="Theme: auto (follows OS)">◐</button>
+            <button id="help-btn" class="btn btn-secondary" title="Help" aria-label="Help">?</button>
         </div>
     </header>
 
@@ -52,9 +54,10 @@
 
         <div id="browseRoot" class="browse-root hidden">
             <div class="toolbar">
-                <span class="toolbar__path" id="currentPath"></span>
+                <nav class="breadcrumbs" id="breadcrumbs" aria-label="Path"></nav>
                 <input type="search" id="filterInput" class="toolbar__filter"
                        placeholder="Filter by name (substring)..." />
+                <select id="extFilter" class="toolbar__ext" multiple aria-label="Filter by extension"></select>
                 <span class="toolbar__count" id="entryCount"></span>
             </div>
             <div class="browse-table-wrap">

mdedit/dist/mdedit.html

@@ -1774,7 +1774,7 @@ body.help-open .app-header {
                 </svg>
                 <div class="header-title-group">
                     <span class="app-header__title">ZDDC Markdown</span>
-                    <span class="build-timestamp">v0.0.13</span>
+                    <span class="build-timestamp">v0.0.14</span>
                 </div>
                 <button id="select-directory" class="btn btn-primary" title="Select a Directory">Select Directory</button>
             </div>

zddc/internal/apps/embedded/archive.html

@@ -2113,7 +2113,7 @@ td[data-field="trackingNumber"] {
                 </svg>
                 <div class="header-title-group">
                     <span class="app-header__title">ZDDC Archive</span>
-                    <span class="build-timestamp">v0.0.13</span>
+                    <span class="build-timestamp">v0.0.14</span>
                 </div>
                 <button id="addDirectoryBtn" class="btn btn-primary">Add Local Directory</button>
                 <button id="refreshHeaderBtn" class="btn btn-secondary hidden" title="Refresh Data" style="font-size:1.1rem;">⟳</button>

zddc/internal/apps/embedded/classifier.html

@@ -1376,7 +1376,7 @@ body.help-open .app-header {
                     </svg>
                     <div class="header-title-group">
                         <span class="app-header__title">ZDDC Classifier</span>
-                        <span class="build-timestamp">v0.0.13</span>
+                        <span class="build-timestamp">v0.0.14</span>
                     </div>
                     <button id="selectDirectoryBtn" class="btn btn-primary">Select Directory</button>
                     <button id="refreshBtn" class="btn btn-secondary hidden" title="Refresh and rescan directory">Refresh</button>

zddc/internal/apps/embedded/index.html

@@ -866,7 +866,7 @@ body {
                 </g>
             </svg>
             <span class="app-header__title">ZDDC Archive</span>
-            <span class="build-timestamp">v0.0.13</span>
+            <span class="build-timestamp">v0.0.14</span>
         </div>
         <div class="header-right">
             <button id="theme-btn" class="btn btn-secondary" title="Theme: auto (follows OS)" aria-label="Theme: auto (follows OS)">◐</button>

zddc/internal/apps/embedded/mdedit.html

@@ -1774,7 +1774,7 @@ body.help-open .app-header {
                 </svg>
                 <div class="header-title-group">
                     <span class="app-header__title">ZDDC Markdown</span>
-                    <span class="build-timestamp">v0.0.13</span>
+                    <span class="build-timestamp">v0.0.14</span>
                 </div>
                 <button id="select-directory" class="btn btn-primary" title="Select a Directory">Select Directory</button>
             </div>

zddc/internal/apps/embedded/transmittal.html

@@ -2210,7 +2210,7 @@ dialog.modal--narrow {
         </svg>
         <div class="header-title-group">
             <span class="app-header__title">ZDDC Transmittal</span>
-            <span class="build-timestamp">v0.0.13</span>
+            <span class="build-timestamp">v0.0.14</span>
         </div>
         <div class="app-header__spacer"></div>
         <div class="app-header__icons">

zddc/internal/apps/embedded/versions.txt

@@ -1,8 +1,8 @@
 # Generated by build.sh — do not edit. One <app>=<build label> per line.
-archive=v0.0.13
-transmittal=v0.0.13
-classifier=v0.0.13
-mdedit=v0.0.13
-landing=v0.0.13
-form=v0.0.13
-browse=v0.0.13
+archive=v0.0.14
+transmittal=v0.0.14
+classifier=v0.0.14
+mdedit=v0.0.14
+landing=v0.0.14
+form=v0.0.14
+browse=v0.0.14

zddc/internal/handler/form.html

@@ -722,7 +722,7 @@ body.help-open .app-header {
                 </g>
             </svg>
             <span class="app-header__title" id="form-title">ZDDC Form</span>
-            <span class="build-timestamp">v0.0.13</span>
+            <span class="build-timestamp">v0.0.14</span>
         </div>
         <div class="header-right">
             <button id="theme-btn" class="btn btn-secondary" title="Theme: auto (follows OS)" aria-label="Theme: auto (follows OS)">◐</button>