diff --git a/src/cli/completion.test.ts b/src/cli/completion.test.ts
new file mode 100644
index 0000000..adb1307
--- /dev/null
+++ b/src/cli/completion.test.ts
@@ -0,0 +1,80 @@
+import { describe, it, expect } from 'vitest';
+import { generateBashCompletion, generateZshCompletion, generateFishCompletion } from './completion.js';
+
+const EXPECTED_SUBCOMMANDS = ['start', 'tui', 'send', 'sessions', 'doctor', 'config', 'completion'];
+
+describe('generateBashCompletion', () => {
+  it('generates valid bash completion', () => {
+    const script = generateBashCompletion();
+    expect(script).toContain('_flynn_completions');
+    expect(script).toContain('complete -F _flynn_completions flynn');
+  });
+
+  it('contains all subcommands', () => {
+    const script = generateBashCompletion();
+    for (const cmd of EXPECTED_SUBCOMMANDS) {
+      expect(script).toContain(cmd);
+    }
+  });
+
+  it('contains global options', () => {
+    const script = generateBashCompletion();
+    expect(script).toContain('--help');
+    expect(script).toContain('--version');
+  });
+
+  it('contains subcommand-specific options', () => {
+    const script = generateBashCompletion();
+    expect(script).toContain('--config');
+    expect(script).toContain('--fullscreen');
+    expect(script).toContain('--no-tools');
+    expect(script).toContain('--raw');
+  });
+});
+
+describe('generateZshCompletion', () => {
+  it('generates valid zsh completion', () => {
+    const script = generateZshCompletion();
+    expect(script).toContain('#compdef flynn');
+    expect(script).toContain('compdef _flynn flynn');
+  });
+
+  it('contains all subcommands', () => {
+    const script = generateZshCompletion();
+    for (const cmd of EXPECTED_SUBCOMMANDS) {
+      expect(script).toContain(cmd);
+    }
+  });
+
+  it('contains subcommand-specific options', () => {
+    const script = generateZshCompletion();
+    expect(script).toContain('--config');
+    expect(script).toContain('--fullscreen');
+  });
+});
+
+describe('generateFishCompletion', () => {
+  it('generates valid fish completion', () => {
+    const script = generateFishCompletion();
+    expect(script).toContain('complete -c flynn');
+    expect(script).toContain('__fish_use_subcommand');
+  });
+
+  it('contains all subcommands', () => {
+    const script = generateFishCompletion();
+    for (const cmd of EXPECTED_SUBCOMMANDS) {
+      expect(script).toContain(cmd);
+    }
+  });
+
+  it('contains subcommand-specific options', () => {
+    const script = generateFishCompletion();
+    expect(script).toContain('__fish_seen_subcommand_from start');
+    expect(script).toContain('__fish_seen_subcommand_from tui');
+  });
+
+  it('contains shell type completions for completion subcommand', () => {
+    const script = generateFishCompletion();
+    expect(script).toContain("'bash zsh fish'");
+  });
+});
diff --git a/src/cli/completion.ts b/src/cli/completion.ts
new file mode 100644
index 0000000..7ab349c
--- /dev/null
+++ b/src/cli/completion.ts
@@ -0,0 +1,149 @@
+import type { Command } from 'commander';
+import { mkdirSync, writeFileSync } from 'fs';
+import { resolve } from 'path';
+import { homedir } from 'os';
+
+const SUBCOMMANDS = ['start', 'tui', 'send', 'sessions', 'doctor', 'config', 'completion'];
+
+const SUBCOMMAND_OPTIONS: Record<string, string[]> = {
+  start: ['-c', '--config'],
+  tui: ['-c', '--config', '-f', '--fullscreen'],
+  send: ['-c', '--config', '--no-tools'],
+  config: ['-c', '--config', '--raw'],
+  completion: ['--install'],
+};
+
+export function generateBashCompletion(): string {
+  const subcmds = SUBCOMMANDS.join(' ');
+  const cases = Object.entries(SUBCOMMAND_OPTIONS)
+    .map(([cmd, opts]) => `      ${cmd}) COMPREPLY=( $(compgen -W "${opts.join(' ')}" -- "$cur") ) ;;`)
+    .join('\n');
+
+  return `# Flynn bash completion — generated by 'flynn completion bash'
+_flynn_completions() {
+  local cur prev subcmd
+  cur="\${COMP_WORDS[COMP_CWORD]}"
+  prev="\${COMP_WORDS[COMP_CWORD-1]}"
+
+  if [[ \${COMP_CWORD} -eq 1 ]]; then
+    COMPREPLY=( $(compgen -W "${subcmds} --help --version" -- "$cur") )
+    return
+  fi
+
+  subcmd="\${COMP_WORDS[1]}"
+  case "$subcmd" in
+${cases}
+      completion) COMPREPLY=( $(compgen -W "bash zsh fish --install" -- "$cur") ) ;;
+      *) COMPREPLY=() ;;
+  esac
+}
+complete -F _flynn_completions flynn
+`;
+}
+
+export function generateZshCompletion(): string {
+  const subcmds = SUBCOMMANDS.map(c => `'${c}:${c} subcommand'`).join(' ');
+  const cases = Object.entries(SUBCOMMAND_OPTIONS)
+    .map(([cmd, opts]) => {
+      const flags = opts.filter(o => o.startsWith('--')).map(o => `'${o}'`).join(' ');
+      return `    ${cmd}) compadd ${flags} ;;`;
+    })
+    .join('\n');
+
+  return `#compdef flynn
+# Flynn zsh completion — generated by 'flynn completion zsh'
+_flynn() {
+  local -a subcmds
+  subcmds=(${subcmds})
+
+  if (( CURRENT == 2 )); then
+    _describe 'command' subcmds
+    return
+  fi
+
+  case "\${words[2]}" in
+${cases}
+    completion) compadd bash zsh fish '--install' ;;
+    *) ;;
+  esac
+}
+compdef _flynn flynn
+`;
+}
+
+export function generateFishCompletion(): string {
+  const lines = [
+    `# Flynn fish completion — generated by 'flynn completion fish'`,
+    `# Disable file completions by default`,
+    `complete -c flynn -f`,
+    ``,
+    `# Subcommands`,
+  ];
+
+  for (const cmd of SUBCOMMANDS) {
+    lines.push(`complete -c flynn -n '__fish_use_subcommand' -a '${cmd}' -d '${cmd} subcommand'`);
+  }
+  lines.push(`complete -c flynn -n '__fish_use_subcommand' -l help -d 'Show help'`);
+  lines.push(`complete -c flynn -n '__fish_use_subcommand' -l version -d 'Show version'`);
+  lines.push('');
+  lines.push('# Subcommand options');
+
+  for (const [cmd, opts] of Object.entries(SUBCOMMAND_OPTIONS)) {
+    for (const opt of opts) {
+      const flag = opt.replace(/^-+/, '');
+      const short = opt.startsWith('--') ? '' : ` -s ${flag}`;
+      const long = opt.startsWith('--') ? ` -l ${flag}` : '';
+      lines.push(`complete -c flynn -n '__fish_seen_subcommand_from ${cmd}'${short}${long}`);
+    }
+  }
+
+  lines.push(`complete -c flynn -n '__fish_seen_subcommand_from completion' -a 'bash zsh fish' -d 'Shell type'`);
+  lines.push('');
+
+  return lines.join('\n');
+}
+
+function getInstallPath(shell: string): string {
+  const home = homedir();
+  switch (shell) {
+    case 'bash': return resolve(home, '.local/share/bash-completion/completions/flynn');
+    case 'zsh': return resolve(home, '.zfunc/_flynn');
+    case 'fish': return resolve(home, '.config/fish/completions/flynn.fish');
+    default: throw new Error(`Unknown shell: ${shell}`);
+  }
+}
+
+export function registerCompletionCommand(program: Command): void {
+  program
+    .command('completion')
+    .description('Generate shell completion script')
+    .argument('<shell>', 'Shell type: bash, zsh, or fish')
+    .option('--install', 'Install to standard location')
+    .action((shell: string, opts: { install?: boolean }) => {
+      const generators: Record<string, () => string> = {
+        bash: generateBashCompletion,
+        zsh: generateZshCompletion,
+        fish: generateFishCompletion,
+      };
+
+      const generator = generators[shell];
+      if (!generator) {
+        console.error(`Unknown shell: ${shell}. Supported: bash, zsh, fish`);
+        process.exit(1);
+      }
+
+      const script = generator();
+
+      if (opts.install) {
+        const installPath = getInstallPath(shell);
+        mkdirSync(resolve(installPath, '..'), { recursive: true });
+        writeFileSync(installPath, script, 'utf-8');
+        console.log(`Completion script installed to: ${installPath}`);
+        if (shell === 'zsh') {
+          console.log(`Ensure ~/.zfunc is in your fpath: fpath=(~/.zfunc $fpath)`);
+        }
+      } else {
+        process.stdout.write(script);
+      }
+    });
+}
diff --git a/src/cli/doctor.ts b/src/cli/doctor.ts
index 84172d4..c10dc9c 100644
--- a/src/cli/doctor.ts
+++ b/src/cli/doctor.ts
@@ -185,6 +185,22 @@ const checkSkills: Check = async (ctx) => {
   }
 };
 
+const checkTailscale: Check = async (ctx) => {
+  if (!ctx.config?.server?.tailscale?.serve) {
+    return { status: 'skip', label: 'Tailscale Serve', detail: '(not enabled)' };
+  }
+  try {
+    const { isTailscaleAvailable } = await import('../gateway/tailscale.js');
+    const result = await isTailscaleAvailable();
+    if (result.available) {
+      return { status: 'pass', label: 'Tailscale Serve', detail: `(v${result.version})` };
+    }
+    return { status: 'fail', label: 'Tailscale Serve', detail: result.error ?? 'Tailscale not available' };
+  } catch (err) {
+    return { status: 'fail', label: 'Tailscale Serve', detail: err instanceof Error ? err.message : String(err) };
+  }
+};
+
 const allChecks: Check[] = [
   checkConfigExists,
   checkConfigParses,
@@ -196,6 +212,7 @@ const allChecks: Check[] = [
   checkTelegram,
   checkMcpServers,
   checkSkills,
+  checkTailscale,
 ];
 
 /** Run all doctor checks in order. Exported for testing. */
diff --git a/src/cli/index.ts b/src/cli/index.ts
index 59b9453..70b6314 100644
--- a/src/cli/index.ts
+++ b/src/cli/index.ts
@@ -6,6 +6,7 @@ import { registerSessionsCommand } from './sessions.js';
 import { registerDoctorCommand } from './doctor.js';
 import { registerConfigCommand } from './config-cmd.js';
 import { registerTuiCommand } from './tui.js';
+import { registerCompletionCommand } from './completion.js';
 
 export function createProgram(): Command {
   const program = new Command();
@@ -21,6 +22,7 @@ export function createProgram(): Command {
   registerSessionsCommand(program);
   registerDoctorCommand(program);
   registerConfigCommand(program);
+  registerCompletionCommand(program);
 
   return program;
 }
diff --git a/src/config/schema.ts b/src/config/schema.ts
index 28f0933..ac67d95 100644
--- a/src/config/schema.ts
+++ b/src/config/schema.ts
@@ -6,8 +6,26 @@ const telegramSchema = z.object({
   require_mention: z.boolean().default(true),
 });
 
+const tailscaleSchema = z.object({
+  /** Enable Tailscale Serve to expose gateway on tailnet. */
+  serve: z.boolean().default(false),
+  /** Custom hostname for Tailscale Serve. Defaults to machine hostname. */
+  hostname: z.string().optional(),
+  /** Tailscale Serve HTTPS port. */
+  port: z.number().default(443),
+}).default({});
+
+const pairingSchema = z.object({
+  /** Enable DM pairing codes for unknown senders. */
+  enabled: z.boolean().default(false),
+  /** Pairing code time-to-live duration (e.g. '5m', '1h'). */
+  code_ttl: z.string().default('5m'),
+  /** Length of generated pairing codes. */
+  code_length: z.number().default(6),
+}).default({});
+
 const serverSchema = z.object({
-  tailscale_only: z.boolean().default(true),
+  tailscale: tailscaleSchema,
   localhost: z.boolean().default(true),
   port: z.number().default(18800),
   /** Static bearer token for gateway auth. If set, all connections must provide it. */
@@ -16,6 +34,8 @@ const serverSchema = z.object({
   tailscale_identity: z.boolean().default(false),
   /** Apply token auth to HTTP requests too (not just WebSocket). Default: true when token is set. */
   auth_http: z.boolean().default(true),
+  /** Single-client gateway lock. When true, only one WebSocket client can be connected at a time. */
+  lock: z.boolean().default(false),
 });
 
 const modelConfigBaseSchema = z.object({
diff --git a/src/daemon/index.ts b/src/daemon/index.ts
index 8637a17..0b7564b 100644
--- a/src/daemon/index.ts
+++ b/src/daemon/index.ts
@@ -811,6 +811,7 @@ export async function startDaemon(config: Config): Promise<DaemonContext> {
       tailscaleIdentity: config.server.tailscale_identity,
     },
     authHttp: config.server.auth_http,
+    lock: config.server.lock,
     uiDir: resolve(import.meta.dirname, '../gateway/ui'),
     config,
     channelRegistry,
@@ -1002,6 +1003,24 @@ export async function startDaemon(config: Config): Promise<DaemonContext> {
 
   await gateway.start();
 
+  // ── Tailscale Serve ────────────────────────────────────────────
+  if (config.server.tailscale?.serve) {
+    const { startTailscaleServe, stopTailscaleServe } = await import('../gateway/tailscale.js');
+    const tsConfig = {
+      localPort: config.server.port,
+      servePort: config.server.tailscale.port,
+      hostname: config.server.tailscale.hostname,
+    };
+    try {
+      await startTailscaleServe(tsConfig);
+      lifecycle.onShutdown(async () => {
+        await stopTailscaleServe(tsConfig);
+      });
+    } catch {
+      console.warn('Tailscale Serve failed to start — gateway still accessible on local port');
+    }
+  }
+
   // ── Heartbeat Monitor ──────────────────────────────────────────
   const heartbeatMonitor = new HeartbeatMonitor({
     config: config.automation.heartbeat,
diff --git a/src/gateway/handlers/handlers.test.ts b/src/gateway/handlers/handlers.test.ts
index eab11b2..70289e2 100644
--- a/src/gateway/handlers/handlers.test.ts
+++ b/src/gateway/handlers/handlers.test.ts
@@ -444,7 +444,7 @@ describe('config handlers', () => {
   function makeConfig() {
     return {
       telegram: { bot_token: 'secret-token-123', allowed_chat_ids: [12345] },
-      server: { tailscale_only: true, localhost: true, port: 18800 },
+      server: { tailscale: {}, localhost: true, port: 18800 },
       models: {
         default: { provider: 'anthropic' as const, model: 'claude-3-haiku', api_key: 'sk-secret-key' },
         fallback_chain: ['anthropic'],
@@ -551,7 +551,7 @@ describe('redactConfig – comprehensive credential redaction', () => {
       telegram: { bot_token: 'tg-secret', allowed_chat_ids: [1], require_mention: true },
       discord: { bot_token: 'dc-secret', allowed_guild_ids: ['g1'], allowed_channel_ids: [], require_mention: true },
       slack: { bot_token: 'sl-bot', app_token: 'sl-app', signing_secret: 'sl-sign', allowed_channel_ids: [], require_mention: false },
-      server: { tailscale_only: true, localhost: true, port: 18800, token: 'bearer-secret', tailscale_identity: false, auth_http: true },
+      server: { tailscale: {}, localhost: true, port: 18800, token: 'bearer-secret', tailscale_identity: false, auth_http: true },
       models: {
         default: { provider: 'anthropic' as const, model: 'claude', api_key: 'sk-def', auth_token: 'at-def',
           fallback: { provider: 'openai' as const, model: 'gpt-4', api_key: 'sk-def-fb', auth_token: 'at-def-fb' },
@@ -704,7 +704,7 @@ describe('redactConfig – comprehensive credential redaction', () => {
     expect((result.slack as any).allowed_channel_ids).toEqual([]);
     // server
     expect((result.server as any).port).toBe(18800);
-    expect((result.server as any).tailscale_only).toBe(true);
+    expect((result.server as any).tailscale).toBeDefined();
     // models
     expect((result.models as any).default.provider).toBe('anthropic');
     expect((result.models as any).default.model).toBe('claude');
diff --git a/src/gateway/index.ts b/src/gateway/index.ts
index 3c67692..9bb7380 100644
--- a/src/gateway/index.ts
+++ b/src/gateway/index.ts
@@ -8,6 +8,8 @@ export { LaneQueue } from './lane-queue.js';
 export { authenticateRequest } from './auth.js';
 export type { AuthConfig, AuthResult } from './auth.js';
 export { serveStatic } from './static.js';
+export { isTailscaleAvailable, startTailscaleServe, stopTailscaleServe } from './tailscale.js';
+export type { TailscaleServeConfig } from './tailscale.js';
 export {
   ErrorCode,
   isValidRequest,
diff --git a/src/gateway/server.ts b/src/gateway/server.ts
index 1dfb06c..22fa23f 100644
--- a/src/gateway/server.ts
+++ b/src/gateway/server.ts
@@ -11,6 +11,7 @@ import type { AuthConfig } from './auth.js';
 import {
   parseMessage,
   makeError,
+  makeResponse,
   ErrorCode,
   type OutboundMessage,
 } from './protocol.js';
@@ -39,6 +40,8 @@ export interface GatewayServerConfig {
   toolExecutor: ToolExecutor;
   version?: string;
   auth?: AuthConfig;
+  /** When true, only one WebSocket client can be connected at a time. */
+  lock?: boolean;
   /** Whether to apply token auth to HTTP requests too (default: true when token is set). */
   authHttp?: boolean;
   uiDir?: string;
@@ -159,6 +162,15 @@ export class GatewayServer {
         this.handleConnection(ws, authResult.identity);
       });
 
+      // Register system.lock handler (needs access to connectionMap)
+      this.router.register('system.lock', async (request) => {
+        return makeResponse(request.id, {
+          locked: this.config.lock ?? false,
+          activeClients: this.connectionMap.size,
+          maxClients: this.config.lock ? 1 : null,
+        });
+      });
+
       this.httpServer.listen(port, host, () => {
         console.log(`Gateway server listening on ${host}:${port}`);
         resolve();
@@ -199,6 +211,12 @@ export class GatewayServer {
   }
 
   private handleConnection(ws: WebSocket, identity?: string): void {
+    // Gateway lock — reject if another client is already connected
+    if (this.config.lock && this.connectionMap.size > 0) {
+      ws.close(4003, 'Gateway locked — another client is already connected');
+      return;
+    }
+
     const connectionId = randomUUID();
     this.sessionBridge.connect(connectionId);
     this.connectionMap.set(ws, connectionId);
diff --git a/src/gateway/tailscale.test.ts b/src/gateway/tailscale.test.ts
new file mode 100644
index 0000000..2ab7347
--- /dev/null
+++ b/src/gateway/tailscale.test.ts
@@ -0,0 +1,123 @@
+import { describe, it, expect, vi, beforeAll, beforeEach } from 'vitest';
+import { execFile } from 'child_process';
+
+// Mock child_process before importing module
+vi.mock('child_process', () => ({
+  execFile: vi.fn(),
+}));
+
+const mockExecFile = vi.mocked(execFile);
+
+describe('tailscale', () => {
+  // Import after mocking
+  let isTailscaleAvailable: typeof import('./tailscale.js').isTailscaleAvailable;
+  let startTailscaleServe: typeof import('./tailscale.js').startTailscaleServe;
+  let stopTailscaleServe: typeof import('./tailscale.js').stopTailscaleServe;
+
+  beforeAll(async () => {
+    const mod = await import('./tailscale.js');
+    isTailscaleAvailable = mod.isTailscaleAvailable;
+    startTailscaleServe = mod.startTailscaleServe;
+    stopTailscaleServe = mod.stopTailscaleServe;
+  });
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe('isTailscaleAvailable', () => {
+    it('returns available when tailscale CLI works', async () => {
+      mockExecFile
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, '1.62.0', '');
+          return {} as any;
+        })
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, '{}', '');
+          return {} as any;
+        });
+
+      const result = await isTailscaleAvailable();
+      expect(result.available).toBe(true);
+      expect(result.version).toBe('1.62.0');
+    });
+
+    it('returns unavailable when tailscale CLI fails', async () => {
+      mockExecFile.mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+        callback(new Error('command not found'), '', 'command not found');
+        return {} as any;
+      });
+
+      const result = await isTailscaleAvailable();
+      expect(result.available).toBe(false);
+      expect(result.error).toBeDefined();
+    });
+  });
+
+  describe('startTailscaleServe', () => {
+    it('calls tailscale serve with correct args', async () => {
+      mockExecFile
+        // serve command
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, '', '');
+          return {} as any;
+        })
+        // status for hostname
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, JSON.stringify({ Self: { DNSName: 'myhost.tailnet.ts.net.' } }), '');
+          return {} as any;
+        });
+
+      const url = await startTailscaleServe({ localPort: 18800 });
+      expect(url).toBe('https://myhost.tailnet.ts.net');
+
+      const serveCall = mockExecFile.mock.calls[0];
+      expect(serveCall[0]).toBe('tailscale');
+      expect(serveCall[1]).toEqual(['serve', '--bg', '--https=443', 'http://127.0.0.1:18800']);
+    });
+
+    it('uses custom serve port', async () => {
+      mockExecFile
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, '', '');
+          return {} as any;
+        })
+        .mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+          callback(null, JSON.stringify({ Self: { DNSName: 'myhost.tailnet.ts.net.' } }), '');
+          return {} as any;
+        });
+
+      const url = await startTailscaleServe({ localPort: 18800, servePort: 8443 });
+      expect(url).toBe('https://myhost.tailnet.ts.net:8443');
+
+      const serveCall = mockExecFile.mock.calls[0];
+      expect(serveCall[1]).toEqual(['serve', '--bg', '--https=8443', 'http://127.0.0.1:18800']);
+    });
+  });
+
+  describe('stopTailscaleServe', () => {
+    it('calls tailscale serve off', async () => {
+      mockExecFile.mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+        callback(null, '', '');
+        return {} as any;
+      });
+
+      await stopTailscaleServe({ localPort: 18800 });
+
+      expect(mockExecFile).toHaveBeenCalledOnce();
+      const call = mockExecFile.mock.calls[0];
+      expect(call[0]).toBe('tailscale');
+      expect(call[1]).toEqual(['serve', '--https=443', 'off']);
+    });
+
+    it('does not throw on failure', async () => {
+      mockExecFile.mockImplementationOnce((_cmd, _args, _opts, callback: any) => {
+        callback(new Error('failed'), '', 'failed');
+        return {} as any;
+      });
+
+      // Should not throw
+      await stopTailscaleServe({ localPort: 18800 });
+    });
+  });
+});
diff --git a/src/gateway/tailscale.ts b/src/gateway/tailscale.ts
new file mode 100644
index 0000000..d1ac4d5
--- /dev/null
+++ b/src/gateway/tailscale.ts
@@ -0,0 +1,94 @@
+import { execFile } from 'child_process';
+
+export interface TailscaleServeConfig {
+  /** The gateway's local port (e.g. 18800). */
+  localPort: number;
+  /** Tailscale Serve HTTPS port (default 443). */
+  servePort?: number;
+  /** Custom hostname (default: machine hostname). */
+  hostname?: string;
+}
+
+/** Execute a command with a timeout, returning stdout. */
+function exec(cmd: string, args: string[], timeoutMs = 5000): Promise<string> {
+  return new Promise((resolve, reject) => {
+    execFile(cmd, args, { timeout: timeoutMs }, (error, stdout, stderr) => {
+      if (error) {
+        reject(new Error(`${cmd} ${args.join(' ')} failed: ${stderr || error.message}`));
+      } else {
+        resolve(stdout.trim());
+      }
+    });
+  });
+}
+
+/**
+ * Check if Tailscale CLI is available and the daemon is running.
+ */
+export async function isTailscaleAvailable(): Promise<{ available: boolean; version?: string; error?: string }> {
+  try {
+    const version = await exec('tailscale', ['version', '--short']);
+    // Check if daemon is running by getting status
+    await exec('tailscale', ['status', '--json']);
+    return { available: true, version };
+  } catch (err) {
+    return { available: false, error: err instanceof Error ? err.message : String(err) };
+  }
+}
+
+/**
+ * Get the MagicDNS hostname from Tailscale status.
+ */
+async function getTailscaleHostname(): Promise<string | undefined> {
+  try {
+    const statusJson = await exec('tailscale', ['status', '--json']);
+    const status = JSON.parse(statusJson) as { Self?: { DNSName?: string } };
+    const dnsName = status.Self?.DNSName;
+    // DNSName ends with a trailing dot — strip it
+    return dnsName?.replace(/\.$/, '');
+  } catch {
+    return undefined;
+  }
+}
+
+/**
+ * Start Tailscale Serve to expose the local gateway port on the tailnet.
+ *
+ * Runs: `tailscale serve --bg --https=<servePort> http://127.0.0.1:<localPort>`
+ */
+export async function startTailscaleServe(config: TailscaleServeConfig): Promise<string | undefined> {
+  const servePort = config.servePort ?? 443;
+  const target = `http://127.0.0.1:${config.localPort}`;
+
+  try {
+    await exec('tailscale', ['serve', '--bg', `--https=${servePort}`, target]);
+    const hostname = config.hostname ?? await getTailscaleHostname();
+    if (hostname) {
+      const url = servePort === 443 ? `https://${hostname}` : `https://${hostname}:${servePort}`;
+      console.log(`Tailscale Serve: Flynn available at ${url}`);
+      return url;
+    }
+    console.log('Tailscale Serve: started (could not determine hostname)');
+    return undefined;
+  } catch (err) {
+    console.error('Failed to start Tailscale Serve:', err instanceof Error ? err.message : err);
+    throw err;
+  }
+}
+
+/**
+ * Stop Tailscale Serve for the configured port.
+ *
+ * Runs: `tailscale serve --https=<servePort> off`
+ */
+export async function stopTailscaleServe(config: TailscaleServeConfig): Promise<void> {
+  const servePort = config.servePort ?? 443;
+
+  try {
+    await exec('tailscale', ['serve', `--https=${servePort}`, 'off']);
+    console.log('Tailscale Serve: stopped');
+  } catch (err) {
+    // Best effort — don't fail shutdown
+    console.error('Failed to stop Tailscale Serve:', err instanceof Error ? err.message : err);
+  }
+}
diff --git a/src/gateway/ui/lib/ws-client.js b/src/gateway/ui/lib/ws-client.js
index 87945ff..a66ca38 100644
--- a/src/gateway/ui/lib/ws-client.js
+++ b/src/gateway/ui/lib/ws-client.js
@@ -61,8 +61,14 @@ export class FlynnClient {
       this._handleMessage(event.data);
     };
 
-    this._ws.onclose = () => {
+    this._ws.onclose = (event) => {
       this._ws = null;
+      // Gateway lock — show specific message and don't auto-reconnect
+      if (event.code === 4003) {
+        this._setStatus('locked');
+        this._autoReconnect = false;
+        return;
+      }
       this._setStatus('disconnected');
       // Reject all pending requests
       for (const [id, pending] of this._pending) {