diff --git a/extensions/open-in-workspace/README.md b/extensions/open-in-workspace/README.md
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+# Open in Workspace — Hermes WebUI Extension
+
+Adds an **"Open in workspace"** button to `read_file` tool cards. When you click it, the file opens in the workspace file-tree panel — the same behavior as clicking an artifact link.
+
+## How it works
+
+- Watches for new tool-card-row elements with `data-tool-kind="read"`
+- Extracts the file path from `row._tcData.args` (or the rendered args section)
+- Injects a Lucide folder-open button inside `.tool-card-detail`
+- Uses `MutationObserver` so it works on dynamically-rendered cards
+
+## Install
+
+From **Settings → Extensions → Gallery**, find **Open in Workspace** and click Install.
+
+Or configure manually:
+
+```bash
+# Clone or copy the extension files, then:
+export HERMES_WEBUI_EXTENSION_DIR=/path/to/open-in-workspace-ext
+export HERMES_WEBUI_EXTENSION_MANIFEST=manifest.json
+./start.sh
+```
diff --git a/extensions/open-in-workspace/manifest.json b/extensions/open-in-workspace/manifest.json
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+{
+  "id": "open-in-workspace",
+  "name": "Open in Workspace",
+  "description": "Adds an 'Open in workspace' button to read_file tool cards, letting you click to reveal the file in the workspace file-tree panel.",
+  "scripts": ["open-in-workspace.js"],
+  "stylesheets": []
+}
diff --git a/extensions/open-in-workspace/open-in-workspace.js b/extensions/open-in-workspace/open-in-workspace.js
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+(function () {
+  'use strict';
+
+  if (document.getElementById('ext-open-in-workspace--loaded')) return;
+  var MARKER = document.createElement('meta');
+  MARKER.id = 'ext-open-in-workspace--loaded';
+
+  /* ── CSS injected via plain <style> block ── */
+  var style = document.createElement('style');
+  style.textContent =
+    '.ext-ws-open-wrap{padding:4px 12px 8px}' +
+    '.ext-ws-open-btn{background:none;border:none;color:var(--blue);font-size:10px;cursor:pointer;padding:0;opacity:.7;display:inline-flex;align-items:center;gap:3px;white-space:nowrap}' +
+    '.ext-ws-open-btn:hover{opacity:1}' +
+    '.ext-ws-open-btn svg{width:12px;height:12px;flex-shrink:0}';
+  document.head.appendChild(style);
+
+  /* ── SVG icon (Lucide folder-open, small) ── */
+  var FOLDER_ICON =
+    '<svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M20 20a2 2 0 0 0 2-2V8a2 2 0 0 0-2-2h-7.9a2 2 0 0 1-1.69-.9L9.6 3.9A2 2 0 0 0 7.93 3H4a2 2 0 0 0-2 2v13a2 2 0 0 0 2 2Z"/><path d="M2 6a2 2 0 0 1 2-2h3.28a2 2 0 0 1 1.82 1.07l1.8 3.87A2 2 0 0 0 12.72 11H20a2 2 0 0 1 2 2v5"/></svg>';
+
+  /* ── Inject button into a single tool-card-row ── */
+  function injectButton(row) {
+    if (row.getAttribute('data-ext-ws-open')) return;
+    var tcData = row._tcData;
+    if (!tcData || !tcData.args) return;
+
+    var path =
+      tcData.args.path ||
+      tcData.args.file_path ||
+      tcData.args.file ||
+      tcData.args.target ||
+      tcData.args.name;
+    if (!path || typeof path !== 'string') return;
+
+    /* Make sure we don't re-process */
+    row.setAttribute('data-ext-ws-open', '1');
+
+    /* Find the tool-card detail container or create a fallback */
+    var detail = row.querySelector('.tool-card-detail');
+    if (detail) {
+      var wrap = document.createElement('div');
+      wrap.className = 'ext-ws-open-wrap';
+      var btn = document.createElement('button');
+      btn.className = 'ext-ws-open-btn';
+      btn.innerHTML = FOLDER_ICON;
+      btn.appendChild(document.createTextNode(' Open in workspace'));
+      btn.addEventListener('click', function (e) {
+        e.stopPropagation();
+        if (typeof openArtifactPath === 'function') {
+          openArtifactPath(path);
+        }
+      });
+      wrap.appendChild(btn);
+      detail.appendChild(wrap);
+    } else {
+      /* Cards without .tool-card-detail (no snippet/args) — add below the card */
+      var card = row.querySelector('.tool-card');
+      if (card) {
+        var wrap = document.createElement('div');
+        wrap.className = 'ext-ws-open-wrap';
+        wrap.style.padding = '2px 12px 8px';
+        var btn = document.createElement('button');
+        btn.className = 'ext-ws-open-btn';
+        btn.innerHTML = FOLDER_ICON;
+        btn.appendChild(document.createTextNode(' Open in workspace'));
+        btn.addEventListener('click', function (e) {
+          e.stopPropagation();
+          if (typeof openArtifactPath === 'function') {
+            openArtifactPath(path);
+          }
+        });
+        wrap.appendChild(btn);
+        card.appendChild(wrap);
+      }
+    }
+  }
+
+  /* ── Observe the entire chat for new tool-card-rows ── */
+  var observer = new MutationObserver(function (mutations) {
+    for (var i = 0; i < mutations.length; i++) {
+      var added = mutations[i].addedNodes;
+      if (!added || added.length === 0) continue;
+      for (var j = 0; j < added.length; j++) {
+        var node = added[j];
+        if (node.nodeType !== 1) continue;
+        /* Direct match */
+        if (
+          node.matches &&
+          node.matches('.tool-card-row[data-tool-kind="read"]')
+        ) {
+          injectButton(node);
+        }
+        /* Check children */
+        if (node.querySelectorAll) {
+          var cards = node.querySelectorAll(
+            '.tool-card-row[data-tool-kind="read"]'
+          );
+          for (var k = 0; k < cards.length; k++) {
+            injectButton(cards[k]);
+          }
+        }
+      }
+    }
+  });
+
+  /* ── Also process existing cards on startup ── */
+  function processExisting() {
+    var existing = document.querySelectorAll(
+      '.tool-card-row[data-tool-kind="read"]'
+    );
+    for (var i = 0; i < existing.length; i++) {
+      injectButton(existing[i]);
+    }
+  }
+
+  /* ── Start observing after DOM is ready ── */
+  function start() {
+    document.head.appendChild(MARKER);
+    var chat = document.querySelector('main') || document.body;
+    observer.observe(chat, { childList: true, subtree: true });
+    processExisting();
+  }
+
+  if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', start);
+  } else {
+    start();
+  }
+})();