diff --git a/diagnostic/index.html b/diagnostic/index.html
index b161fbb..124ed4a 100644
--- a/diagnostic/index.html
+++ b/diagnostic/index.html
@@ -165,7 +165,13 @@
     <div class="card">
       <div style="display:flex;justify-content:space-between;align-items:center;margin-bottom:8px;">
         <h2>Sessions</h2>
-        <button class="btn secondary" onclick="loadSessions()" style="padding:4px 10px;font-size:11px;">Laden</button>
+        <div style="display:flex;gap:4px;">
+          <button class="btn secondary" onclick="createSession()" style="padding:4px 10px;font-size:11px;">+ Neu</button>
+          <button class="btn secondary" onclick="loadSessions()" style="padding:4px 10px;font-size:11px;">Laden</button>
+        </div>
+      </div>
+      <div id="active-session-bar" style="font-size:10px;color:#34C759;margin-bottom:6px;padding:4px 6px;background:#0D0D1A;border-radius:4px;display:none;">
+        Aktiv: <span id="active-session-name" style="font-weight:bold;"></span>
       </div>
       <div id="sessions-list" style="max-height:300px;overflow-y:auto;font-size:12px;"></div>
       <div id="session-detail" style="display:none;margin-top:8px;background:#080810;border:1px solid #1E1E2E;border-radius:4px;padding:8px;max-height:300px;overflow-y:auto;">
@@ -361,7 +367,10 @@
       const proto = location.protocol === 'https:' ? 'wss' : 'ws';
       ws = new WebSocket(`${proto}://${location.host}`);
 
-      ws.onopen = () => addLog('info', 'browser', 'Verbunden mit Diagnostic Server');
+      ws.onopen = () => {
+        addLog('info', 'browser', 'Verbunden mit Diagnostic Server');
+        send({ action: 'get_active_session' });
+      };
       ws.onclose = () => {
         addLog('warn', 'browser', 'Verbindung zum Diagnostic Server verloren — Reconnect in 2s');
         setTimeout(connectWS, 2000);
@@ -461,10 +470,23 @@
         if (msg.type === 'sessions_list') { renderSessions(msg); return; }
         if (msg.type === 'session_detail') { renderSessionDetail(msg); return; }
         if (msg.type === 'session_deleted') {
-          if (msg.ok) loadSessions(); // Liste neu laden
+          if (msg.ok) loadSessions();
           else alert('Loeschen fehlgeschlagen: ' + (msg.error || '?'));
           return;
         }
+        if (msg.type === 'active_session') {
+          updateActiveSessionBar(msg.sessionKey);
+          loadSessions(); // Tabelle neu rendern
+          return;
+        }
+        if (msg.type === 'session_created') {
+          if (msg.ok) {
+            loadSessions();
+          } else {
+            alert('Session erstellen fehlgeschlagen: ' + (msg.error || '?'));
+          }
+          return;
+        }
         if (msg.type === 'brain_list') { renderBrainList(msg); return; }
         if (msg.type === 'brain_content') { renderBrainContent(msg); return; }
         if (msg.type === 'response') { return; }
@@ -848,6 +870,8 @@
       send({ action: 'list_sessions' });
     }
 
+    let currentActiveSession = '';
+
     function renderSessions(data) {
       const container = document.getElementById('sessions-list');
       if (data.error) {
@@ -871,14 +895,19 @@
         const key = escapeHtml(s.sessionKey || s.path.split('/').pop());
         const orphanBadge = s.orphan ? ' <span style="background:#FF3B30;color:#fff;font-size:9px;padding:1px 4px;border-radius:3px;">verwaist</span>' : '';
         const modelBadge = s.model ? `<div style="font-size:9px;color:#555570;">${escapeHtml(s.model)}</div>` : '';
-        const keyColor = s.orphan ? '#555570' : '#E0E0F0';
-        html += `<tr style="border-bottom:1px solid #0D0D1A;cursor:pointer;" onmouseover="this.style.background='#1E1E2E'" onmouseout="this.style.background=''">`
+        const isActive = (s.sessionKey === currentActiveSession);
+        const keyColor = isActive ? '#34C759' : (s.orphan ? '#555570' : '#E0E0F0');
+        const activeBadge = isActive ? ' <span style="background:#34C759;color:#000;font-size:9px;padding:1px 4px;border-radius:3px;">aktiv</span>' : '';
+        const rowBg = isActive ? 'background:rgba(52,199,89,0.08);' : '';
+        html += `<tr style="border-bottom:1px solid #0D0D1A;cursor:pointer;${rowBg}" onmouseover="this.style.background='#1E1E2E'" onmouseout="this.style.background='${isActive ? 'rgba(52,199,89,0.08)' : ''}'">`
               + `<td style="padding:4px 6px;" onclick="viewSession('${escapeHtml(s.path)}')">`
-              + `<div style="color:${keyColor};">${key}${orphanBadge}</div>${modelBadge}</td>`
+              + `<div style="color:${keyColor};">${key}${activeBadge}${orphanBadge}</div>${modelBadge}</td>`
               + `<td style="padding:4px 6px;color:#8888AA;">${s.lines}</td>`
               + `<td style="padding:4px 6px;color:#8888AA;font-size:10px;">${date}</td>`
-              + `<td style="padding:4px 6px;"><button class="btn secondary" onclick="event.stopPropagation();deleteSession('${escapeHtml(s.path)}')" style="padding:2px 6px;font-size:10px;color:#FF6B6B;">X</button></td>`
-              + '</tr>';
+              + `<td style="padding:4px 6px;white-space:nowrap;">`
+              + (isActive ? '' : `<button class="btn secondary" onclick="event.stopPropagation();activateSession('${escapeHtml(s.sessionKey)}')" style="padding:2px 6px;font-size:10px;color:#34C759;margin-right:2px;" title="Aktivieren">&#9654;</button>`)
+              + `<button class="btn secondary" onclick="event.stopPropagation();deleteSession('${escapeHtml(s.path)}')" style="padding:2px 6px;font-size:10px;color:#FF6B6B;" title="Loeschen">X</button>`
+              + `</td></tr>`;
       }
       html += '</table>';
       container.innerHTML = html;
@@ -941,6 +970,28 @@
       send({ action: 'delete_session', sessionPath: path });
     }
 
+    function activateSession(sessionKey) {
+      send({ action: 'set_active_session', sessionKey });
+    }
+
+    function createSession() {
+      const name = prompt('Name fuer neue Session (a-z, 0-9, -, _):');
+      if (!name) return;
+      send({ action: 'create_session', sessionName: name.trim() });
+    }
+
+    function updateActiveSessionBar(sessionKey) {
+      currentActiveSession = sessionKey || '';
+      const bar = document.getElementById('active-session-bar');
+      const nameEl = document.getElementById('active-session-name');
+      if (currentActiveSession) {
+        bar.style.display = 'block';
+        nameEl.textContent = currentActiveSession;
+      } else {
+        bar.style.display = 'none';
+      }
+    }
+
     // ── Brain Viewer ────────────────────────────────────────
 
     function loadBrain() {
diff --git a/diagnostic/server.js b/diagnostic/server.js
index 1eadca4..2d55ba7 100644
--- a/diagnostic/server.js
+++ b/diagnostic/server.js
@@ -35,6 +35,7 @@ const state = {
   rvs: { status: "disconnected", lastError: null },
   proxy: { status: "unknown", lastError: null },
 };
+let activeSessionKey = "aria-diag-v3";
 const logs = [];
 let gatewayWs = null;
 let rvsWs = null;
@@ -385,7 +386,7 @@ function sendToGateway(text, isPipeline) {
     id: reqId,
     method: "chat.send",
     params: {
-      sessionKey: "aria-diag-v3",
+      sessionKey: activeSessionKey,
       message: text,
       idempotencyKey: crypto.randomUUID(),
     },
@@ -976,6 +977,12 @@ wss.on("connection", (ws) => {
         handleReadSession(ws, msg.sessionPath);
       } else if (msg.action === "delete_session") {
         handleDeleteSession(ws, msg.sessionPath);
+      } else if (msg.action === "set_active_session") {
+        handleSetActiveSession(ws, msg.sessionKey);
+      } else if (msg.action === "get_active_session") {
+        ws.send(JSON.stringify({ type: "active_session", sessionKey: activeSessionKey }));
+      } else if (msg.action === "create_session") {
+        handleCreateSession(ws, msg.sessionName);
       } else if (msg.action === "list_brain") {
         handleListBrain(ws);
       } else if (msg.action === "read_brain_file") {
@@ -1230,7 +1237,31 @@ async function handleDeleteSession(clientWs, sessionPath) {
   }
   try {
     log("warn", "server", `Loesche Session: ${sessionPath}`);
-    await dockerExec("aria-core", `rm '${sessionPath.replace(/'/g, "")}'`);
+    const safePath = sessionPath.replace(/'/g, "");
+    // Session-ID aus Pfad extrahieren (UUID.jsonl)
+    const filename = safePath.split("/").pop();
+    const sessionId = filename.replace(".jsonl", "");
+
+    // 1. JSONL-Datei loeschen
+    await dockerExec("aria-core", `rm -f '${safePath}'`);
+
+    // 2. Eintrag aus sessions.json entfernen
+    try {
+      const sFile = `${SESSIONS_DIR}/sessions.json`;
+      const script = [
+        'const fs=require("fs");',
+        `const f="${sFile}",sid="${sessionId}";`,
+        'try{const d=JSON.parse(fs.readFileSync(f,"utf8"));',
+        'for(const k of Object.keys(d)){const v=d[k];',
+        'if(v&&(v.sessionId===sid||v.id===sid))delete d[k];}',
+        'fs.writeFileSync(f,JSON.stringify(d,null,2));}catch(e){}',
+      ].join("");
+      const b64 = Buffer.from(script).toString("base64");
+      await dockerExec("aria-core", `echo ${b64} | base64 -d | node`);
+    } catch (e) {
+      log("warn", "server", `sessions.json Update fehlgeschlagen: ${e.message}`);
+    }
+
     clientWs.send(JSON.stringify({ type: "session_deleted", ok: true, path: sessionPath }));
     log("info", "server", "Session geloescht");
   } catch (err) {
@@ -1238,6 +1269,40 @@ async function handleDeleteSession(clientWs, sessionPath) {
   }
 }
 
+// ── Session aktivieren ─────────────────────────────────
+function handleSetActiveSession(clientWs, sessionKey) {
+  if (!sessionKey || typeof sessionKey !== "string") {
+    clientWs.send(JSON.stringify({ type: "active_session", ok: false, error: "Kein sessionKey" }));
+    return;
+  }
+  activeSessionKey = sessionKey;
+  log("info", "server", `Aktive Session: ${activeSessionKey}`);
+  // Allen Clients mitteilen
+  for (const c of browserClients) {
+    c.send(JSON.stringify({ type: "active_session", sessionKey: activeSessionKey }));
+  }
+}
+
+// ── Session erstellen ──────────────────────────────────
+async function handleCreateSession(clientWs, sessionName) {
+  if (!sessionName || typeof sessionName !== "string" || !/^[a-zA-Z0-9_-]+$/.test(sessionName)) {
+    clientWs.send(JSON.stringify({ type: "session_created", ok: false, error: "Ungueltiger Name (nur a-z, 0-9, -, _)" }));
+    return;
+  }
+  try {
+    // Session wird automatisch erstellt wenn man die erste Nachricht sendet
+    activeSessionKey = sessionName;
+    log("info", "server", `Neue Session erstellt und aktiviert: ${sessionName}`);
+    // Allen Clients mitteilen
+    for (const c of browserClients) {
+      c.send(JSON.stringify({ type: "active_session", sessionKey: activeSessionKey }));
+    }
+    clientWs.send(JSON.stringify({ type: "session_created", ok: true, sessionKey: sessionName }));
+  } catch (err) {
+    clientWs.send(JSON.stringify({ type: "session_created", ok: false, error: err.message }));
+  }
+}
+
 // ── Brain Viewer ────────────────────────────────────────
 
 async function handleListBrain(clientWs) {