diff --git a/src/backend/database/routes/host.ts b/src/backend/database/routes/host.ts
index b7e7d1aa..211834a0 100644
--- a/src/backend/database/routes/host.ts
+++ b/src/backend/database/routes/host.ts
@@ -1459,6 +1459,90 @@ router.put(
  *       500:
  *         description: Failed to fetch SSH data.
  */
+/**
+ * @openapi
+ * /host/db/host/{id}/terminal-config:
+ *   patch:
+ *     summary: Update a host's terminal behaviour flags
+ *     description: Merges the given flags into the host's terminalConfig. Owner or a recipient with edit access. Currently supports autoTmux; used by the "enable Auto-Tmux" action shown when a persisted session expires.
+ *     tags:
+ *       - Hosts
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             properties:
+ *               autoTmux:
+ *                 type: boolean
+ *     responses:
+ *       200:
+ *         description: Updated.
+ *       403:
+ *         description: No edit access.
+ *       404:
+ *         description: Host not found.
+ */
+router.patch(
+  "/db/host/:id/terminal-config",
+  authenticateJWT,
+  permissionManager.requirePermission("hosts.edit"),
+  requireDataAccess,
+  async (req: Request, res: Response) => {
+    const userId = (req as AuthenticatedRequest).userId!;
+    const hostId = parseInt(String(req.params.id), 10);
+    const { autoTmux } = req.body ?? {};
+
+    if (isNaN(hostId)) {
+      return res.status(400).json({ error: "Invalid host ID" });
+    }
+    if (typeof autoTmux !== "boolean") {
+      return res.status(400).json({ error: "autoTmux must be a boolean" });
+    }
+
+    try {
+      const access = await permissionManager.canAccessHost(
+        userId,
+        hostId,
+        "edit",
+      );
+      if (!access.hasAccess) {
+        return res.status(403).json({ error: "Access denied to host" });
+      }
+      const ownerId =
+        await createCurrentHostResolutionRepository().findHostOwnerId(hostId);
+      const host = ownerId
+        ? await createCurrentHostRepository().findByIdForUser(ownerId, hostId)
+        : null;
+      if (!host || !ownerId) {
+        return res.status(404).json({ error: "Host not found" });
+      }
+
+      let terminalConfig: Record<string, unknown> = {};
+      if (host.terminalConfig) {
+        try {
+          terminalConfig = JSON.parse(host.terminalConfig);
+        } catch {
+          terminalConfig = {};
+        }
+      }
+      await createCurrentHostRepository().updateForUser(ownerId, hostId, {
+        terminalConfig: JSON.stringify({ ...terminalConfig, autoTmux }),
+      });
+
+      res.json({ success: true, autoTmux });
+    } catch (error) {
+      sshLogger.error("Failed to update host terminal config", error, {
+        operation: "host_terminal_config_update",
+        hostId,
+        userId,
+      });
+      res.status(500).json({ error: "Failed to update terminal config" });
+    }
+  },
+);
+
 router.get(
   "/db/host",
   authenticateJWT,
diff --git a/src/backend/database/routes/user-settings-routes.ts b/src/backend/database/routes/user-settings-routes.ts
index 40df928b..b840cba3 100644
--- a/src/backend/database/routes/user-settings-routes.ts
+++ b/src/backend/database/routes/user-settings-routes.ts
@@ -44,6 +44,7 @@ export type HostDefaults = {
   cursorBlink?: boolean;
   enableSessionLogging?: boolean;
   enableCommandHistory?: boolean;
+  autoTmux?: boolean;
 };
 
 async function getAdminActor(
diff --git a/src/ui/api/host-terminal-config-api.ts b/src/ui/api/host-terminal-config-api.ts
new file mode 100644
index 00000000..ac6d64a4
--- /dev/null
+++ b/src/ui/api/host-terminal-config-api.ts
@@ -0,0 +1,15 @@
+import { authApi, handleApiError } from "@/main-axios";
+
+/** Flips Auto-Tmux for one host without round-tripping the whole editor form. */
+export async function setHostAutoTmux(
+  hostId: number,
+  autoTmux: boolean,
+): Promise<void> {
+  try {
+    await authApi.patch(`/host/db/host/${hostId}/terminal-config`, {
+      autoTmux,
+    });
+  } catch (error) {
+    throw handleApiError(error, "update host auto-tmux");
+  }
+}
diff --git a/src/ui/api/settings-api.ts b/src/ui/api/settings-api.ts
index 96c05403..a11824c2 100644
--- a/src/ui/api/settings-api.ts
+++ b/src/ui/api/settings-api.ts
@@ -61,6 +61,30 @@ export async function getSessionTimeout(): Promise<{ timeoutHours: number }> {
   }
 }
 
+// How long a detached terminal session is kept alive server-side.
+export async function getTerminalSessionSettings(): Promise<{
+  timeoutMinutes: number;
+  enabled: boolean;
+}> {
+  try {
+    const response = await authApi.get("/terminal/session_settings");
+    return response.data;
+  } catch (error) {
+    handleApiError(error, "fetch terminal session settings");
+  }
+}
+
+export async function updateTerminalSessionSettings(input: {
+  timeoutMinutes?: number;
+  enabled?: boolean;
+}): Promise<void> {
+  try {
+    await authApi.patch("/terminal/session_settings", input);
+  } catch (error) {
+    handleApiError(error, "update terminal session settings");
+  }
+}
+
 export async function updateSessionTimeout(
   timeoutHours: number,
 ): Promise<void> {
@@ -288,6 +312,7 @@ export type HostDefaults = {
   cursorBlink?: boolean;
   enableSessionLogging?: boolean;
   enableCommandHistory?: boolean;
+  autoTmux?: boolean;
 };
 
 export async function getHostDefaults(): Promise<HostDefaults> {
diff --git a/src/ui/features/terminal/Terminal.tsx b/src/ui/features/terminal/Terminal.tsx
index 9ae60483..6a62f2e7 100644
--- a/src/ui/features/terminal/Terminal.tsx
+++ b/src/ui/features/terminal/Terminal.tsx
@@ -1182,6 +1182,56 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
       }, delay);
     }
 
+    // A persisted session that timed out reconnects to a fresh shell below.
+    // Say so, and offer the setting that would have kept it alive.
+    async function explainSessionExpiry() {
+      const hostLabel = hostConfig.name || hostConfig.ip;
+      let minutes: number | null = null;
+      try {
+        const { getTerminalSessionSettings } =
+          await import("@/api/settings-api");
+        minutes = (await getTerminalSessionSettings()).timeoutMinutes;
+      } catch {
+        /* the notice still makes sense without the number */
+      }
+      const notice = minutes
+        ? t("terminal.sessionExpiredNotice", { host: hostLabel, minutes })
+        : t("terminal.sessionExpiredNoticeNoMinutes", { host: hostLabel });
+      addLog({ type: "warning", stage: "connection", message: notice });
+
+      const canEnable =
+        typeof hostConfig.id === "number" &&
+        !hostConfig.terminalConfig?.autoTmux &&
+        !hostConfig.joinShareId;
+      toast.warning(notice, {
+        duration: 15000,
+        ...(canEnable
+          ? {
+              action: {
+                label: t("terminal.enableAutoTmuxAction"),
+                onClick: () => {
+                  void import("@/api/host-terminal-config-api")
+                    .then(({ setHostAutoTmux }) =>
+                      setHostAutoTmux(hostConfig.id as number, true),
+                    )
+                    .then(() => {
+                      window.dispatchEvent(
+                        new CustomEvent("termix:hosts-changed"),
+                      );
+                      toast.success(
+                        t("terminal.autoTmuxEnabled", { host: hostLabel }),
+                      );
+                    })
+                    .catch(() =>
+                      toast.error(t("terminal.autoTmuxEnableFailed")),
+                    );
+                },
+              },
+            }
+          : {}),
+      });
+    }
+
     async function connectToHost(cols: number, rows: number) {
       if (isConnectingRef.current) {
         return;
@@ -1979,6 +2029,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
             isAttachingSessionRef.current = false;
             sessionIdRef.current = null;
             wasSessionExpiredRef.current = true;
+            void explainSessionExpiry();
             if (hostConfig.instanceId) {
               import("@/main-axios").then(({ patchOpenTab }) => {
                 patchOpenTab(hostConfig.instanceId!, {
diff --git a/src/ui/locales/en.json b/src/ui/locales/en.json
index 64d3017c..0ccea2ce 100644
--- a/src/ui/locales/en.json
+++ b/src/ui/locales/en.json
@@ -1027,7 +1027,7 @@
     "enableAutoMosh": "Enable Auto-Mosh",
     "enableAutoMoshDesc": "Prefer Mosh over SSH if available",
     "enableAutoTmux": "Enable Auto-Tmux",
-    "enableAutoTmuxDesc": "Automatically launch or attach to tmux session",
+    "enableAutoTmuxDesc": "Keep your shell and anything running in it alive across disconnects and browser restarts by running inside tmux (tmux must be installed on the host)",
     "enableSessionLogging": "Session Logging",
     "enableSessionLoggingDesc": "Record terminal session output for later review",
     "allowSessionSharing": "Allow Session Sharing",
@@ -1796,7 +1796,7 @@
     "reopenTab": "Reopen",
     "sectionOpen": "Open",
     "sectionBackground": "Background",
-    "backgroundDesc": "Sessions persist for 30 minutes after disconnect and can be reconnected.",
+    "backgroundDesc": "Sessions persist for {{minutes}} minutes after disconnect and can be reconnected.",
     "persisted": "Persisted in background",
     "expiresIn": "Expires in {{duration}}",
     "search": "Search connections...",
@@ -1989,6 +1989,11 @@
     }
   },
   "terminal": {
+    "sessionExpiredNotice": "Your previous session on {{host}} expired after {{minutes}} minutes disconnected; the shell and anything running in it are gone. Enable Auto-Tmux on this host to keep sessions alive.",
+    "sessionExpiredNoticeNoMinutes": "Your previous session on {{host}} expired while disconnected; the shell and anything running in it are gone. Enable Auto-Tmux on this host to keep sessions alive.",
+    "enableAutoTmuxAction": "Enable Auto-Tmux",
+    "autoTmuxEnabled": "Auto-Tmux enabled for {{host}}. It applies from the next connection.",
+    "autoTmuxEnableFailed": "Failed to enable Auto-Tmux",
     "connect": "Connect to Host",
     "clear": "Clear",
     "paste": "Paste",
@@ -3645,6 +3650,14 @@
     "hostDefaultsStatusCheckEnabled": "Enable Status Check",
     "hostDefaultsStatusCheckEnabledDesc": "Poll online/offline status on new hosts by default",
     "hostDefaultsTerminal": "Terminal",
+    "hostDefaultsAutoTmux": "Auto-Tmux",
+    "hostDefaultsAutoTmuxDesc": "Run new hosts' terminals inside tmux so sessions survive disconnects (needs tmux on the host)",
+    "terminalSessionTimeout": "Terminal Session Persistence",
+    "terminalSessionTimeoutDesc": "How long a disconnected terminal is kept alive on the server before it is closed. Min 1 · Max 1440 minutes. For sessions that must outlive this, enable Auto-Tmux on the host.",
+    "terminalSessionTimeoutRange": "Enter a value between 1 and 1440 minutes",
+    "terminalSessionTimeoutSaved": "Terminal session persistence saved",
+    "terminalSessionTimeoutSaveFailed": "Failed to save terminal session persistence",
+    "minutes": "minutes",
     "hostDefaultsSessionLogging": "Session Logging",
     "hostDefaultsSessionLoggingDesc": "Record terminal sessions on new hosts by default",
     "hostDefaultsCommandHistory": "Command History",
diff --git a/src/ui/sidebar/AdminSettingsPanel.tsx b/src/ui/sidebar/AdminSettingsPanel.tsx
index 06d5c843..9ece3214 100644
--- a/src/ui/sidebar/AdminSettingsPanel.tsx
+++ b/src/ui/sidebar/AdminSettingsPanel.tsx
@@ -94,6 +94,10 @@ import {
   type AdminUser,
 } from "./AdminManagementSections";
 import { toast } from "sonner";
+import {
+  getTerminalSessionSettings,
+  updateTerminalSessionSettings,
+} from "@/api/settings-api";
 import { getDatabaseTransferUrl } from "@/lib/database-transfer-url";
 import {
   AdminDatabaseSection,
@@ -154,6 +158,12 @@ export function AdminSettingsPanel({
   const [allowPasswordLogin, setAllowPasswordLogin] = useState(true);
   const [allowPasswordReset, setAllowPasswordReset] = useState(true);
   const [sessionTimeout, setSessionTimeout] = useState("24");
+  const [terminalTimeout, setTerminalTimeout] = useState("30");
+  useEffect(() => {
+    getTerminalSessionSettings()
+      .then((settings) => setTerminalTimeout(String(settings.timeoutMinutes)))
+      .catch(() => {});
+  }, []);
   const [statusInterval, setStatusInterval] = useState("60");
   const [metricsInterval, setMetricsInterval] = useState("30");
   const [metricsHistoryRetention, setMetricsHistoryRetention] = useState("7");
@@ -689,6 +699,20 @@ export function AdminSettingsPanel({
     }
   }
 
+  async function handleSaveTerminalTimeout() {
+    const minutes = parseInt(terminalTimeout, 10);
+    if (isNaN(minutes) || minutes < 1 || minutes > 1440) {
+      toast.error(t("admin.terminalSessionTimeoutRange"));
+      return;
+    }
+    try {
+      await updateTerminalSessionSettings({ timeoutMinutes: minutes });
+      toast.success(t("admin.terminalSessionTimeoutSaved"));
+    } catch {
+      toast.error(t("admin.terminalSessionTimeoutSaveFailed"));
+    }
+  }
+
   async function handleSaveMonitoring() {
     const status = parseInt(statusInterval, 10);
     const metrics = parseInt(metricsInterval, 10);
@@ -1164,6 +1188,9 @@ export function AdminSettingsPanel({
         sessionTimeout={sessionTimeout}
         setSessionTimeout={setSessionTimeout}
         handleSaveSessionTimeout={handleSaveSessionTimeout}
+        terminalTimeout={terminalTimeout}
+        setTerminalTimeout={setTerminalTimeout}
+        handleSaveTerminalTimeout={handleSaveTerminalTimeout}
         statusInterval={statusInterval}
         setStatusInterval={setStatusInterval}
         metricsInterval={metricsInterval}
diff --git a/src/ui/sidebar/AdminSettingsSections.tsx b/src/ui/sidebar/AdminSettingsSections.tsx
index d4ec6e08..38dab945 100644
--- a/src/ui/sidebar/AdminSettingsSections.tsx
+++ b/src/ui/sidebar/AdminSettingsSections.tsx
@@ -50,6 +50,9 @@ type GeneralSettingsSectionProps = {
   sessionTimeout: string;
   setSessionTimeout: Dispatch<SetStateAction<string>>;
   handleSaveSessionTimeout: () => void;
+  terminalTimeout: string;
+  setTerminalTimeout: Dispatch<SetStateAction<string>>;
+  handleSaveTerminalTimeout: () => void;
   statusInterval: string;
   setStatusInterval: Dispatch<SetStateAction<string>>;
   metricsInterval: string;
@@ -101,6 +104,9 @@ export function AdminGeneralSettingsSection({
   sessionTimeout,
   setSessionTimeout,
   handleSaveSessionTimeout,
+  terminalTimeout,
+  setTerminalTimeout,
+  handleSaveTerminalTimeout,
   statusInterval,
   setStatusInterval,
   metricsInterval,
@@ -299,6 +305,36 @@ export function AdminGeneralSettingsSection({
           </span>
         </div>
 
+        <div className="flex flex-col gap-2 pt-3 mt-2">
+          <span className="text-[10px] font-bold uppercase tracking-widest text-muted-foreground">
+            {t("admin.terminalSessionTimeout")}
+          </span>
+          <div className="flex items-center gap-2">
+            <Input
+              type="number"
+              min={1}
+              max={1440}
+              value={terminalTimeout}
+              onChange={(e) => setTerminalTimeout(e.target.value)}
+              className="w-20 text-sm"
+            />
+            <span className="text-xs text-muted-foreground">
+              {t("admin.minutes")}
+            </span>
+            <Button
+              variant="outline"
+              size="sm"
+              className="text-xs border-accent-brand/40 text-accent-brand hover:bg-accent-brand/10 hover:text-accent-brand h-7"
+              onClick={handleSaveTerminalTimeout}
+            >
+              {t("common.save")}
+            </Button>
+          </div>
+          <span className="text-[10px] text-muted-foreground">
+            {t("admin.terminalSessionTimeoutDesc")}
+          </span>
+        </div>
+
         <div className="flex flex-col gap-2 border-t border-border pt-3 mt-2">
           <span className="text-[10px] font-bold uppercase tracking-widest text-muted-foreground">
             {t("admin.monitoringDefaults")}
@@ -1096,6 +1132,17 @@ export function AdminHostDefaultsSection({
           <span className="text-[10px] font-bold uppercase tracking-widest text-muted-foreground">
             {t("admin.hostDefaultsTerminal")}
           </span>
+          <SettingRow
+            label={t("admin.hostDefaultsAutoTmux")}
+            description={t("admin.hostDefaultsAutoTmuxDesc")}
+          >
+            <AdminToggle
+              on={defaults.autoTmux ?? false}
+              onToggle={() =>
+                setDefaults((p) => ({ ...p, autoTmux: !(p.autoTmux ?? false) }))
+              }
+            />
+          </SettingRow>
           <SettingRow
             label={t("admin.hostDefaultsSessionLogging")}
             description={t("admin.hostDefaultsSessionLoggingDesc")}
diff --git a/src/ui/sidebar/ConnectionsPanel.tsx b/src/ui/sidebar/ConnectionsPanel.tsx
index 011d8692..2d77f216 100644
--- a/src/ui/sidebar/ConnectionsPanel.tsx
+++ b/src/ui/sidebar/ConnectionsPanel.tsx
@@ -314,6 +314,14 @@ export function ConnectionsPanel({
 }) {
   const { t } = useTranslation();
   const [now, setNow] = useState(Date.now());
+
+  const [persistMinutes, setPersistMinutes] = useState(30);
+  useEffect(() => {
+    import("@/api/settings-api")
+      .then(({ getTerminalSessionSettings }) => getTerminalSessionSettings())
+      .then((settings) => setPersistMinutes(settings.timeoutMinutes))
+      .catch(() => {});
+  }, []);
   const [activeSessions, setActiveSessions] = useState<ActiveSessionInfo[]>([]);
   const activeSessionsRef = useRef(activeSessions);
   activeSessionsRef.current = activeSessions;
@@ -589,7 +597,9 @@ export function ConnectionsPanel({
           />
           <div className="px-3 py-1.5 border-b border-border/40">
             <span className="text-[10px] text-muted-foreground/50">
-              {t("connections.backgroundDesc")}
+              {t("connections.backgroundDesc", {
+                minutes: persistMinutes,
+              })}
             </span>
           </div>
           {filteredBackgroundTabs.map((record) => {
diff --git a/src/ui/sidebar/HostEditor.tsx b/src/ui/sidebar/HostEditor.tsx
index b0d1652d..7115afaf 100644
--- a/src/ui/sidebar/HostEditor.tsx
+++ b/src/ui/sidebar/HostEditor.tsx
@@ -1788,6 +1788,27 @@ export function HostEditor({
                       onValueChange={([v]) => setField("scrollback", v)}
                     />
                   </div>
+                  <SettingRow
+                    label={t("hosts.enableAutoTmux")}
+                    description={
+                      <>
+                        {t("hosts.enableAutoTmuxDesc")}{" "}
+                        <a
+                          href="https://docs.termix.site/features/terminal/tmux"
+                          target="_blank"
+                          rel="noreferrer"
+                          className="text-accent-brand hover:underline"
+                        >
+                          {t("hosts.docsLink")}
+                        </a>
+                      </>
+                    }
+                  >
+                    <FakeSwitch
+                      checked={form.autoTmux}
+                      onChange={(v) => setField("autoTmux", v)}
+                    />
+                  </SettingRow>
                   <SettingRow
                     label={t("hosts.sshAgentForwardingLabel")}
                     description={t("hosts.sshAgentForwardingShortDesc")}
@@ -1815,27 +1836,6 @@ export function HostEditor({
                       onChange={(v) => setField("autoMosh", v)}
                     />
                   </SettingRow>
-                  <SettingRow
-                    label={t("hosts.enableAutoTmux")}
-                    description={
-                      <>
-                        {t("hosts.enableAutoTmuxDesc")}{" "}
-                        <a
-                          href="https://docs.termix.site/features/terminal/tmux"
-                          target="_blank"
-                          rel="noreferrer"
-                          className="text-accent-brand hover:underline"
-                        >
-                          {t("hosts.docsLink")}
-                        </a>
-                      </>
-                    }
-                  >
-                    <FakeSwitch
-                      checked={form.autoTmux}
-                      onChange={(v) => setField("autoTmux", v)}
-                    />
-                  </SettingRow>
                   <SettingRow
                     label={t("hosts.enableSessionLogging")}
                     description={
diff --git a/src/ui/sidebar/HostEditorData.ts b/src/ui/sidebar/HostEditorData.ts
index 24fe3635..79416009 100644
--- a/src/ui/sidebar/HostEditorData.ts
+++ b/src/ui/sidebar/HostEditorData.ts
@@ -232,7 +232,7 @@ export function createHostEditorForm(
     moshCommand: host?.terminalConfig?.moshCommand ?? "",
     agentForwarding: host?.terminalConfig?.agentForwarding ?? false,
     autoMosh: host?.terminalConfig?.autoMosh ?? false,
-    autoTmux: host?.terminalConfig?.autoTmux ?? false,
+    autoTmux: host?.terminalConfig?.autoTmux ?? d?.autoTmux ?? false,
     sudoPasswordAutoFill: host?.terminalConfig?.sudoPasswordAutoFill ?? false,
     sudoPassword: host?.hasSudoPassword
       ? "existing_sudo_password"
diff --git a/src/ui/tests/sidebar/HostEditorData.test.ts b/src/ui/tests/sidebar/HostEditorData.test.ts
index c91a6f0e..e5ba485d 100644
--- a/src/ui/tests/sidebar/HostEditorData.test.ts
+++ b/src/ui/tests/sidebar/HostEditorData.test.ts
@@ -627,3 +627,17 @@ describe("createHostEditorForm credentialId", () => {
     expect(createHostEditorForm(null).credentialId).toBe("");
   });
 });
+
+describe("createHostEditorForm auto-tmux", () => {
+  it("inherits the admin default for a new host but keeps an existing host's own choice", () => {
+    expect(createHostEditorForm(null, { autoTmux: true }).autoTmux).toBe(true);
+    expect(createHostEditorForm(null, {}).autoTmux).toBe(false);
+
+    const host = {
+      id: "1",
+      name: "box",
+      terminalConfig: { autoTmux: false },
+    } as unknown as Host;
+    expect(createHostEditorForm(host, { autoTmux: true }).autoTmux).toBe(false);
+  });
+});