diff --git a/main.js b/main.js
index cc7b0167..7ec36aa2 100644
--- a/main.js
+++ b/main.js
@@ -484,6 +484,25 @@ const remoteAttachAdapter = createTmuxAttachAdapter({
   log,
 });
 
+// Joins the sidebar's remote sessions to the indexer's live descriptors so the
+// renderer can route a click without ever naming an attach mechanism itself
+// — see .ai/contexts/session-cache.md ("Remote hosts — tmux attach").
+function annotateRemoteAttachable(projects) {
+  const descriptorsByAlias = new Map();
+  for (const project of projects) {
+    for (const session of project.sessions) {
+      if (!session.remoteAlias) continue;
+      if (!descriptorsByAlias.has(session.remoteAlias)) {
+        const descriptors = remoteIndexer.getRemoteSessions(session.remoteAlias);
+        descriptorsByAlias.set(session.remoteAlias, new Map(descriptors.map(d => [d.sessionId, d])));
+      }
+      const descriptor = descriptorsByAlias.get(session.remoteAlias).get(session.sessionId);
+      session.remoteAttachable = !!(descriptor && remoteAttachAdapter.supports(descriptor));
+    }
+  }
+  return projects;
+}
+
 /** Directory holding a folder key's transcripts, local or mirrored. */
 function projectsDirForFolder(folder) {
   return resolveFolderDir(folder);
@@ -938,7 +957,7 @@ ipcMain.handle('get-projects', async (_event, showArchived) => {
       reconcileCacheFromFilesystem();
     }
 
-    return buildProjectsFromCache(showArchived);
+    return annotateRemoteAttachable(buildProjectsFromCache(showArchived));
   } catch (err) {
     console.error('Error listing projects:', err);
     return [];
diff --git a/public/sidebar.js b/public/sidebar.js
index 0226d3e4..eb1f619e 100644
--- a/public/sidebar.js
+++ b/public/sidebar.js
@@ -1087,11 +1087,15 @@ function rebindSidebarEvents(projects) {
       return;
     }
 
+    // see .ai/contexts/session-cache.md ("Remote SSH hosts")
+    if (session.remoteAlias && !session.remoteAttachable) {
+      item.title = 'Not currently attachable — opening the transcript instead';
+    }
+
     item.onclick = () => {
       if (item.dataset.subagent && session.parentSessionId) {
         showSubagentTranscript(session);
-      } else if (session.remoteAlias) {
-        // Observation only. see .ai/contexts/session-cache.md ("Remote SSH hosts")
+      } else if (session.remoteAlias && !session.remoteAttachable) {
         showJsonlViewer(session);
       } else {
         openSession(session);
diff --git a/test/dom-sidebar-remote-session.test.js b/test/dom-sidebar-remote-session.test.js
index 8081e9f2..85073e5e 100644
--- a/test/dom-sidebar-remote-session.test.js
+++ b/test/dom-sidebar-remote-session.test.js
@@ -1,6 +1,8 @@
-// Issue #201: a session mirrored from an SSH host is observation-only. Its row
-// must say so, and clicking it must open the read-only transcript instead of
-// trying to `claude --resume` in a cwd this machine does not have.
+// Issue #201: a session mirrored from an SSH host defaults to observation
+// only. Its row says so via a badge naming the host. Issue #221: when the
+// main process reports the session as attachable, the click opens a terminal
+// instead; otherwise it still falls back to the read-only transcript rather
+// than trying to `claude --resume` in a cwd this machine does not have.
 
 const test = require('node:test');
 const assert = require('node:assert/strict');
@@ -45,7 +47,7 @@ test('a remote session row carries a badge naming its host', () => {
   } finally { ctx.destroy(); }
 });
 
-test('clicking a remote session opens the transcript, never a resume', () => {
+test('a remote session with no live attachable descriptor opens the transcript, never a resume', () => {
   const ctx = setupSidebarDom();
   try {
     register(ctx, [REMOTE_SESSION]);
@@ -56,10 +58,39 @@ test('clicking a remote session opens the transcript, never a resume', () => {
     ctx.window.openSession = (s) => opened.push(s.sessionId);
     ctx.window.showJsonlViewer = (s) => viewed.push(s.sessionId);
 
-    ctx.document.getElementById('si-remote-1').onclick();
+    const item = ctx.document.getElementById('si-remote-1');
+    item.onclick();
 
     assert.deepEqual(viewed, ['remote-1']);
     assert.deepEqual(opened, [], 'openSession would spawn a PTY in a cwd that is not on this machine');
+    assert.match(item.title, /not currently attachable/i, 'the row must say why it fell back to the transcript');
+    assert.doesNotMatch(item.title, /tmux/i, 'the renderer must never name a multiplexer');
+  } finally { ctx.destroy(); }
+});
+
+test('a remote session with a live attachable descriptor opens a terminal, not the transcript', () => {
+  const ctx = setupSidebarDom();
+  try {
+    const attachable = { ...REMOTE_SESSION, sessionId: 'remote-2', remoteAttachable: true };
+    register(ctx, [attachable]);
+    ctx.sidebar.renderProjects([makeSampleProject({
+      projectPath: '/srv/supervision',
+      folder: 'planificator::-srv-supervision',
+      remoteAlias: 'planificator',
+      sessions: [attachable],
+    })], true);
+
+    const opened = [];
+    const viewed = [];
+    ctx.window.openSession = (s) => opened.push(s.sessionId);
+    ctx.window.showJsonlViewer = (s) => viewed.push(s.sessionId);
+
+    const item = ctx.document.getElementById('si-remote-2');
+    item.onclick();
+
+    assert.deepEqual(opened, ['remote-2']);
+    assert.deepEqual(viewed, [], 'an attachable remote session must open a terminal, not the read-only transcript');
+    assert.ok(!item.title, 'an attachable session carries no fallback-reason title');
   } finally { ctx.destroy(); }
 });
 
diff --git a/test/get-projects-cold-start-reconcile.test.js b/test/get-projects-cold-start-reconcile.test.js
index 96f98239..b5131332 100644
--- a/test/get-projects-cold-start-reconcile.test.js
+++ b/test/get-projects-cold-start-reconcile.test.js
@@ -45,13 +45,17 @@ function makeHandler(mocks) {
   const fn = new Function(
     'isCachePopulated', 'isSearchIndexPopulated', 'isInitialScanComplete',
     'populateCacheViaWorker',
-    'reconcileCacheFromFilesystem', 'buildProjectsFromCache', 'showArchived',
+    'reconcileCacheFromFilesystem', 'buildProjectsFromCache', 'annotateRemoteAttachable', 'showArchived',
     body
   );
+  // annotateRemoteAttachable (remote-attach join, issue #221) is irrelevant to
+  // the populate/reconcile/build ordering this file locks down -- a passthrough
+  // stands in for it unless a test overrides it.
+  const annotateRemoteAttachable = mocks.annotateRemoteAttachable || (projects => projects);
   return () => fn(
     mocks.isCachePopulated, mocks.isSearchIndexPopulated,
     mocks.isInitialScanComplete, mocks.populateCacheViaWorker,
-    mocks.reconcileCacheFromFilesystem, mocks.buildProjectsFromCache, false
+    mocks.reconcileCacheFromFilesystem, mocks.buildProjectsFromCache, annotateRemoteAttachable, false
   );
 }