AgentHub/server/lib/tmux.js

/**
 * @file tmux.js
 * @description Thin wrapper around the `tmux` CLI for the terminal-run
 * feature. Every dashboard-managed session is named `agenthub-lane-<id>` (see
 * `pty-run.js`) so a real terminal can attach to the exact same session with
 * `tmux attach -t agenthub-lane-<id>` (or `agenthub lanes shell`). Never builds a
 * shell string — every call is `execFileSync("tmux", [...argv])` (a member's
 * listing: `execFile`) with an explicit argument array (matches this repo's
 * rule for git in worktree.js).
 * No call composes a shell command line at all, `sendCommand` included: it
 * takes over an idle pane with `respawn-pane -- <argv>` rather than typing a
 * quoted line into that pane's shell, which keeps an API key passed in `env`
 * out of the pane's rendered text, its scrollback and the user's shell history.
 * `sendText` is the one primitive that sends typed text — a pane running an
 * interactive chat program that reads stdin as a message, not a shell — and
 * `sendKey` presses one named key (Shift+Tab for `pane-mode.js`), never text.
 *
 * Server mode, one Linux user per account (S3): a member's panes live on THAT
 * member's tmux server, socket `<home>/.agenthub/tmux/sock` (`run-as.js`), so
 * they run as the member. Every call naming a session goes there, resolved
 * from the session's workspace, and runs AS the member (`sudo -u`, tmux by
 * the absolute path sudoers lists) — never as a host client: the member owns
 * that socket's folder, and a host client on it could be handed a fake server
 * or replaced by a member's command (`detach-client -E`). sudo logs its
 * command line, so a session's environment and argv travel in a launch file
 * (`run-as.launchArgv`) and a paste on stdin. Listing covers every server;
 * a member's runs in the background and a poll reads its last answer.
 * With no member (local mode, S3 not installed, the host's own workspaces)
 * nothing changes.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const { execFile, execFileSync } = require("node:child_process");

// Test seam: swap the exec implementation so unit tests never invoke a real
// tmux binary. Mirrors run-spawner.js's __injectChildForTest/__reset style.
// stderr is ignored, not inherited: every caller already wraps these in
// try/catch and treats failure as "no session" — piping tmux's own
// "error connecting to ..." noise to the process's stderr just spams the
// journal on every poll while no tmux server is running yet.
// cwd "/": a tmux server is forked from the call that starts it and keeps
// that cwd; once it is deleted, tmux ignores every pane's `-c` (issue #69).
const EXEC_OPTS = { encoding: "utf8", stdio: ["pipe", "pipe", "ignore"], cwd: "/" };
let execImpl = (args, opts = EXEC_OPTS) => execFileSync("tmux", args, opts);

// Linux: the tmux server lives in the cgroup of whatever started it — the
// dashboard's systemd unit, or the terminal/IDE scope a dev server runs in —
// and dies when that cgroup is stopped (an update's restart under a unit
// without KillMode=process, systemd-oomd, closing that app). So the FIRST
// session, which starts the server, is created inside a transient scope of
// its own: panes end only on Quit (`quit.js`) or with the machine. `--scope`
// runs tmux as a child, so it keeps this process's environment.
const realScopeImpl = (args) =>
  execFileSync(
    "systemd-run",
    [
      "--user",
      "--scope",
      "--quiet",
      "--collect",
      "--description=AgentHub tmux server",
      "--",
      "tmux",
      ...args,
    ],
    EXEC_OPTS
  );
let scopeImpl = realScopeImpl;

// S3: the member account a session belongs to (null = the host's own server),
// and how a tmux command runs AS that member on their server (`input` = its
// stdin). Seams, so tests never sudo.
let accountImpl = (name) => require("./run-as").accountForSession(name);
// A member's server is theirs: they can stop it (SIGSTOP) or fill it with
// sessions. So each call on it is bounded (time, output), and a server that
// timed out or flooded us is not asked again for MEMBER_BACKOFF_MS — its
// panes read as UNKNOWN meanwhile. LISTING (every poll: GET /api/run and
// /api/lanes, the heal beat, the liveness reaper) never waits for a member:
// it runs async (`memberListImpl`) into `listed`, which the poll reads. A
// call a user's click makes (new-session, send-keys, kill, has-session)
// stays synchronous.
// ponytail: a click on a frozen member's pane (and a pane-token / gateway
// has-session check) still blocks up to MEMBER_TIMEOUT_MS once per backoff;
// make those async too if that ever shows.
const MEMBER_TIMEOUT_MS = 3000;
const MEMBER_BACKOFF_MS = 60_000;
const MEMBER_OPTS = {
  ...EXEC_OPTS,
  timeout: MEMBER_TIMEOUT_MS,
  killSignal: "SIGKILL",
  maxBuffer: 1 << 20,
};
const { stdio: _piped, ...MEMBER_LIST_OPTS } = MEMBER_OPTS; // execFile always pipes
const sudoTmux = (acct, args) => {
  const runAs = require("./run-as");
  return runAs.sudoArgv(acct, "tmux", ["-S", runAs.tmuxSocket(acct), ...args]);
};
const realMemberImpl = (acct, args, input) => {
  const [cmd, argv] = sudoTmux(acct, args);
  return execFileSync(cmd, argv, input == null ? MEMBER_OPTS : { ...MEMBER_OPTS, input });
};
// The same, async, with execFileSync's error shape: `status` = exit code,
// ETIMEDOUT / ENOBUFS for a kill at the timeout / a flood.
const realMemberListImpl = (acct, args) =>
  new Promise((resolve, reject) => {
    const [cmd, argv] = sudoTmux(acct, args);
    execFile(cmd, argv, MEMBER_LIST_OPTS, (err, out) => {
      if (!err) return resolve(out);
      if (typeof err.code === "number") err.status = err.code;
      if (err.killed) err.code = "ETIMEDOUT";
      if (err.code === "ERR_CHILD_PROCESS_STDIO_MAXBUFFER") err.code = "ENOBUFS";
      reject(err);
    });
  });
let memberImpl = realMemberImpl;
let memberListImpl = realMemberListImpl;
let unreachable = new Map(); // member login → backoff end
function reachable(acct) {
  if ((unreachable.get(acct.login) || 0) > Date.now()) {
    throw Object.assign(new Error(`${acct.login}: tmux server not answering`), {
      code: "ETMUXHUNG",
    });
  }
}
function noteHang(acct, err) {
  if (err.code === "ETIMEDOUT" || err.code === "ENOBUFS") {
    unreachable.set(acct.login, Date.now() + MEMBER_BACKOFF_MS);
  }
}
function memberCall(acct, args, input) {
  reachable(acct);
  try {
    return memberImpl(acct, args, input);
  } catch (err) {
    noteHang(acct, err);
    throw err;
  }
}
/** Test seam. A sync `member` fake also answers the async listing. */
function __setAccountImpl(fn, member) {
  accountImpl = fn;
  if (member) {
    memberImpl = member;
    memberListImpl = (acct, args) => new Promise((resolve) => resolve(member(acct, args)));
  }
}
function accountOf(name) {
  try {
    return accountImpl(name);
  } catch (err) {
    // A member's workspace with no usable account never falls back to the
    // host's server: that would run the pane as the host in their folder.
    if (err.code === "EMEMBERGONE") throw err;
    return null; // no DB yet, a malformed name: the host's own server
  }
}
/** Run a tmux command on the server that holds session `name`. */
function onServerOf(name, args, input) {
  const acct = accountOf(name);
  return acct ? memberCall(acct, args, input) : execImpl(args);
}

// Whether this tmux takes `=name` targets: true for tmux itself, false for
// psmux (the WinGet `tmux` on Windows), null until a live session has shown
// which. A fake exec in a test is real tmux unless it says otherwise.
let exactTargets = null;

function __setExecImpl(fn, { exact = true } = {}) {
  execImpl = fn;
  scopeImpl = null; // a fake tmux never starts a real scope

  exactTargets = exact;
  listed = new Map();
  listGen++;
}
function __setScopeImpl(fn) {
  scopeImpl = fn;
}
function __reset() {
  execImpl = (args, opts = EXEC_OPTS) => execFileSync("tmux", args, opts);
  scopeImpl = realScopeImpl;
  accountImpl = (name) => require("./run-as").accountForSession(name);
  memberImpl = realMemberImpl;
  memberListImpl = realMemberListImpl;
  exactTargets = null;
  listed = new Map();
  listGen++;
  unreachable = new Map();
}

// The `list-sessions` answer, shared for LIST_TTL_MS. Every open dashboard
// polls GET /api/run, and each synchronous spawn forks this whole process —
// measured 2,247 calls, 60 s of a 90 s run blocked, at 10 browsers. A session
// this process creates or kills clears it, so only a pane that exits on its
// own can read as live for up to a second. "No server" (exit 1) is an answer
// too and is shared; any other failure is not.
const LIST_TTL_MS = 1000;
const LIST_ARGS = ["list-sessions", "-F", "#{session_name}"];
// psmux (Windows) ignores `-F` and prints `name: 1 windows (created …)`. A
// session name never holds a `:` (tmux rewrites it), so the text before the
// first one is the name in either form.
const sessionNames = (out) =>
  String(out)
    .split("\n")
    .map((l) => l.split(":")[0].trim())
    .filter(Boolean)
    .join("\n");
let listed = new Map(); // member login ("" = ours) → { at, out } | { at, err }
let listGen = 0; // bumped by a change this process makes: drops lists in flight
function listOutput(acct = null) {
  if (acct) return memberListOutput(acct);
  const hit = listed.get("");
  if (hit && Date.now() - hit.at < LIST_TTL_MS) {
    if (hit.err) throw hit.err;
    return hit.out;
  }
  try {
    const out = sessionNames(execImpl(LIST_ARGS));
    listed.set("", { at: Date.now(), out });
    return out;
  } catch (err) {
    if (err.status === 1 || err.code === "ENOENT") listed.set("", { at: Date.now(), err });
    else listed.delete("");
    throw err;
  }
}

// A member's list is never waited for: a read answers from `listed` and,
// once that is LIST_TTL_MS old, starts one async re-list. Until a first
// answer — or once the last is MEMBER_LIST_MAX_AGE_MS old (nobody polled) —
// or while their server fails, it throws: their panes are UNKNOWN. A session
// this process creates or kills is written into the answer at once (`noteSession`).
const MEMBER_LIST_MAX_AGE_MS = 15_000; // > the 10 s heal beat
const refreshing = new Set(); // member logins with a list in flight
function memberListOutput(acct) {
  const hit = listed.get(acct.login);
  const age = hit ? Date.now() - hit.at : Infinity;
  if (age >= LIST_TTL_MS) refreshList(acct);
  if (age >= MEMBER_LIST_MAX_AGE_MS) {
    throw Object.assign(new Error(`${acct.login}: tmux list pending`), { code: "ETMUXPENDING" });
  }
  if (hit.err) throw hit.err;
  return hit.out;
}
function refreshList(acct) {
  const key = acct.login;
  if (refreshing.has(key)) return;
  refreshing.add(key);
  const gen = listGen;
  const hangs = unreachable; // a test's __reset starts a new one
  const done = (entry) => {
    refreshing.delete(key);
    if (gen === listGen) listed.set(key, { at: Date.now(), ...entry });
  };
  new Promise((resolve) => {
    reachable(acct);
    resolve(memberListImpl(acct, LIST_ARGS));
  }).then(
    // A member's server answers for their own workspaces only: a name it
    // lists that belongs to anyone else (a server the member runs to lie
    // about another pane) is not believed.
    (out) =>
      done({
        out: sessionNames(out)
          .split("\n")
          .filter((n) => ownedBy(n.trim(), acct))
          .join("\n"),
      }),
    (err) => {
      if (hangs === unreachable) noteHang(acct, err);
      // "No server" is an empty list; any other failure is shared too, so a
      // broken server of theirs is not asked again on every poll.
      done(err.status === 1 || err.code === "ENOENT" ? { out: "" } : { err });
    }
  );
}
/** A session this process made or ended: ours re-lists, a member's answer is
 *  corrected in place (an unknown one stays unknown). */
function noteSession(name, acct, alive) {
  listGen++;
  listed.delete("");
  const hit = acct && listed.get(acct.login);
  if (!hit || hit.err) return;
  const names = hit.out.split("\n").filter((n) => n.trim() && n.trim() !== name);
  if (alive) names.push(name);
  listed.set(acct.login, { at: hit.at, out: names.join("\n") });
}
/** Test seam: resolves once no member list is in flight. */
async function __settle() {
  while (refreshing.size) await new Promise((r) => setImmediate(r));
}

function ownedBy(name, acct) {
  try {
    return accountImpl(name)?.login === acct.login;
  } catch {
    return false;
  }
}

/** Our own server first, then every member's (S3). */
function allServers() {
  try {
    return [null, ...require("./run-as").membersWithTmux()];
  } catch {
    return [null];
  }
}

/**
 * Probe once, on a session that exists: `=name` failing where the bare name
 * answers means this tmux has no exact-match syntax (psmux answers
 * "no server running on session '=name'"), so every target there is the bare
 * name. Until a session exists to ask, tmux's own syntax.
 */
function exact() {
  if (exactTargets !== null) return exactTargets;
  let first;
  try {
    first = sessionNames(execImpl(LIST_ARGS))
      .split("\n")
      .map((x) => x.trim())
      .find(Boolean);
  } catch {
    return true;
  }
  if (!first) return true;
  const answers = (t) => {
    try {
      execImpl(["has-session", "-t", t]);
      return true;
    } catch {
      return false;
    }
  };
  if (answers(`=${first}`)) exactTargets = true;
  else if (answers(first)) exactTargets = false;
  return exactTargets ?? true;
}

// tmux resolves a bare `-t agenthub-lane-1` by PREFIX when no exact match
// exists, so it would hit `agenthub-lane-12` once lane 1's session is gone —
// and killSession would kill the wrong lane. `=` forces an exact match; pane
// and option targets need the trailing `:` (tmux 3.4 rejects `=name` there).
// psmux has neither form and names a session by its bare name.
const session = (name) => (exact() ? `=${name}` : name);
const pane = (name) => (exact() ? `=${name}:` : name);

function hasSession(name) {
  try {
    onServerOf(name, ["has-session", "-t", session(name)]);
    return true;
  } catch {
    return false;
  }
}

/** Our running tmux server's pid, or null when none answers. */
function serverPid() {
  try {
    const pid = String(execImpl(["display-message", "-p", "#{pid}"])).trim();
    return /^\d+$/.test(pid) ? pid : null;
  } catch {
    return null;
  }
}

/** `-e NAME=value` pairs for tmux, in a stable order. */
function envFlags(env) {
  const flags = [];
  for (const [key, value] of Object.entries(env || {})) flags.push("-e", `${key}=${value}`);
  return flags;
}

/**
 * Create a detached tmux session running `argv` as the pane's command. Throws
 * if tmux itself fails to start (caller decides how to surface that).
 *
 * `env` becomes tmux `-e NAME=value` pairs, which tmux puts in the pane's own
 * environment (tmux >= 3.2). The dashboard uses it for AGENTHUB_LANE_ID so a `agenthub`
 * call from inside the pane knows exactly which lane it belongs to instead of
 * guessing from cwd — see resolveLaneArg in bin/agenthub.js.
 */
function newSession({ name, cwd, argv, env }) {
  // No argv = tmux's own default shell (a Windows Terminal pane).
  const cmd = argv.length ? ["--", ...argv] : [];
  noteSession(name, null, false);
  const args = ["new-session", "-d", "-s", name, "-c", cwd, ...envFlags(env), ...cmd];
  const acct = accountOf(name);
  if (acct) {
    // As the member (the first call starts their server); env and argv in
    // the launch file, never on sudo's logged command line.
    const launch = require("./run-as").launchArgv(acct, env, argv);
    memberCall(acct, ["new-session", "-d", "-s", name, "-c", cwd, "--", ...launch]);
    noteSession(name, acct, true);
  } else if (scopeImpl && process.platform === "linux" && !serverPid()) {
    try {
      scopeImpl(args);
    } catch {
      // No user manager (SSH without linger, no systemd): the plain start.
      if (!hasSession(name)) execImpl(args);
    }
  } else {
    execImpl(args);
  }
  try {
    enableMouse(name);
  } catch (err) {
    // The pane's command exited at once (a CLI that refuses the terminal tmux
    // gives it, say) and tmux closed the session with it: say that, not the
    // "Command failed: tmux set-option …" that hid the real problem.
    if (hasSession(name)) throw err;
    throw Object.assign(
      new Error(
        `the session's command exited as soon as it started: ${argv[0] || "the default shell"}`
      ),
      { code: "EPANEEXITED" }
    );
  }
}

// Without this the pane has no scrollbar/drag scroll at all — wheel events
// just pass through to the running program instead of entering tmux's own
// copy-mode scrollback. xterm.js forwards tmux's mouse-tracking escapes
// automatically once mouse mode is on, so no client-side change is needed.
// Called on every attach (not just at creation) so a session started before
// this option existed — or before a server restart picked up the change —
// still gets it; `set-option` is idempotent, so re-running it is harmless.
// The status bar goes off here too: the dashboard's tab bar already names the
// pane, and tmux's green line only eats a row of the terminal.
function enableMouse(name) {
  // tmux runs `;`-separated commands from ONE argv (each tmux call is a
  // synchronous spawn on the event loop), stopping at the first that fails —
  // so the options every tmux knows go first, in their own call. psmux (no
  // `=name` targets) is not known to chain, so it gets one call per option.
  const run = (...cmds) => {
    if (exact())
      return onServerOf(
        name,
        cmds.flatMap((c, i) => (i ? [";", ...c] : c))
      );
    for (const c of cmds) onServerOf(name, c);
  };
  run(
    ["set-option", "-t", pane(name), "mouse", "on"],
    ["set-option", "-t", pane(name), "status", "off"]
  );
  // A draggable scrollbar beside the pane (mouse mode makes it drag). Only a
  // tmux SERVER of 3.7+ knows the option; an older one refuses it, which is
  // fine — the pane just has none (`/agenthub-doctor` says how to upgrade).
  try {
    run(
      ["set-option", "-t", pane(name), "pane-scrollbars", "on"],
      // tmux's default (`fg=white,bg=black,width=1`) is a one-column track in
      // ANSI black — the terminal theme's border colour, almost the background —
      // so it reads as no scrollbar at all. Bright slider. ONE column: tmux 3.7c
      // reserves `width` columns but paints only the first, so a second one is
      // never cleared and shows stale cells — a ghost second scrollbar.
      [
        "set-option",
        "-t",
        pane(name),
        "pane-scrollbars-style",
        "fg=brightwhite,bg=black,width=1,pad=0",
      ]
    );
  } catch {
    /* tmux < 3.7 */
  }
}

/**
 * The command currently running in the session's active pane (`bash`, `zsh`,
 * `claude`, …). Null when tmux can't answer — callers treat that as "unknown,
 * don't touch the pane".
 */
function paneCommand(name) {
  try {
    return (
      onServerOf(name, [
        "display-message",
        "-p",
        "-t",
        pane(name),
        "#{pane_current_command}",
      ]).trim() || null
    );
  } catch {
    return null;
  }
}

/**
 * Run `argv` in an existing session's pane. Only ever called when the pane sits
 * at a shell prompt (see `paneCommand`), so what `-k` kills is an idle shell.
 *
 * `respawn-pane` and not `send-keys`, because `env` may carry a secret — an AI
 * Router's API key, which Codex reads from the variable its `env_key` names.
 * Typing it would put a `KEY='sk-live-…' codex …` line into the pane's rendered
 * text, which the dashboard streams to every attached browser, into the tmux
 * scrollback, and into the user's shell history. `-e` hands the value to the
 * tmux server through argv instead, exactly as `newSession` already does, and
 * the pane never renders it. Running argv directly also means no shell to quote
 * for, so the whole class of quoting bugs goes with it.
 */
function sendCommand(name, argv, env, cwd) {
  const acct = accountOf(name);
  if (acct) {
    const launch = require("./run-as").launchArgv(acct, env, argv);
    memberCall(acct, [
      "respawn-pane",
      "-k",
      "-t",
      pane(name),
      ...(cwd ? ["-c", cwd] : []),
      "--",
      ...launch,
    ]);
    return;
  }
  onServerOf(name, [
    "respawn-pane",
    "-k",
    "-t",
    pane(name),
    ...(cwd ? ["-c", cwd] : []),
    ...envFlags(env),
    "--",
    ...argv,
  ]);
}

/**
 * Type a literal line of plain text into an existing pane and press Enter —
 * for a program that reads stdin as a message rather than a shell command
 * (an interactive `claude`/`codex` chat pane), where `sendCommand`'s POSIX
 * quoting and `KEY=value ` env prefix would show up as literal punctuation in
 * the message instead of being interpreted. `text` must be single-line: `-l`
 * sends it as one literal keystroke burst, so an embedded newline would submit
 * only the first line and leave the rest sitting unsent in the input box.
 */
function sendText(name, text) {
  onServerOf(name, ["send-keys", "-t", pane(name), "-l", text]);
  onServerOf(name, ["send-keys", "-t", pane(name), "Enter"]);
}

/**
 * Paste `text` into the pane as one bracketed paste, then press Enter. Unlike
 * `sendText` it may span lines: the text goes into a named buffer through an
 * argv element (`set-buffer -- <text>`), never a shell, and `-d` deletes the
 * buffer after the paste so a prompt does not linger in tmux's buffer list.
 */
function pasteText(name, text) {
  const buf = `agenthub-paste-${name}`;
  // A member's prompt goes in on stdin: sudo logs argv.
  if (accountOf(name)) onServerOf(name, ["load-buffer", "-b", buf, "-"], text);
  else onServerOf(name, ["set-buffer", "-b", buf, "--", text]);
  onServerOf(name, ["paste-buffer", "-p", "-d", "-b", buf, "-t", pane(name)]);
  onServerOf(name, ["send-keys", "-t", pane(name), "Enter"]);
}

/** The pane's visible screen as plain text (no escape sequences). */
function capturePane(name) {
  return String(onServerOf(name, ["capture-pane", "-p", "-t", pane(name)]));
}

/** Press ONE named key (`BTab`, `Escape`) in the pane — a key name, never text. */
function sendKey(name, key) {
  onServerOf(name, ["send-keys", "-t", pane(name), key]);
}

/** Idempotent — a session that's already gone is not an error. */
function killSession(name) {
  try {
    onServerOf(name, ["kill-session", "-t", session(name)]);
  } catch {
    /* already gone */
  }
  noteSession(name, accountOfQuiet(name), false);
}

/** Session names starting with `prefix`. Empty array if tmux has no server running at all. */
function listSessions(prefix) {
  const names = [];
  for (const acct of allServers()) {
    try {
      names.push(...listOutput(acct).split("\n"));
    } catch {
      /* no server there */
    }
  }
  return names.map((s) => s.trim()).filter((s) => s && s.startsWith(prefix));
}

/**
 * Every live session name from ONE `list-sessions` — what a poll asks instead
 * of a synchronous has-session per name, each of which blocks the event loop
 * (and so every terminal keystroke) for a whole tmux spawn. Empty when no
 * server runs (tmux exits 1) or tmux is not installed; null when OUR call
 * itself failed (EAGAIN/ENOMEM under memory pressure), which proves nothing
 * about the panes — a caller must not read that as "every pane is gone". A
 * MEMBER's server that fails (stopped, flooding, gone wrong) proves nothing
 * either, but only about that member's panes: `has` answers true for them,
 * so nobody's runs end and everyone else's are still checked.
 */
function liveSessions() {
  const live = new Set();
  const unknown = new Set(); // member logins whose server did not answer
  for (const acct of allServers()) {
    try {
      for (const s of listOutput(acct).split("\n")) if (s.trim()) live.add(s.trim());
    } catch (err) {
      if (err.status === 1 || err.code === "ENOENT") continue;
      if (!acct) return null;
      unknown.add(acct.login);
    }
  }
  if (unknown.size) {
    const has = live.has.bind(live);
    live.has = (name) => has(name) || unknown.has(accountOfQuiet(name)?.login);
  }
  return live;
}

function accountOfQuiet(name) {
  try {
    return accountImpl(name);
  } catch {
    return null;
  }
}

/**
 * `[file, args]` attaching a terminal to a MEMBER's session (as the member,
 * sudo), or null for one on our own server (pty-attach runs our binary).
 */
function memberAttach(name) {
  const acct = accountOf(name);
  if (!acct) return null;
  const runAs = require("./run-as");
  return runAs.sudoArgv(acct, "tmux", [
    ...["-S", runAs.tmuxSocket(acct), "attach-session", "-t", session(name)],
  ]);
}

function isTmuxAvailable() {
  return clientVersion() !== null;
}

/** The tmux binary's version (`3.7c`, `next-3.8`), null when it is absent. */
function clientVersion() {
  try {
    return execImpl(["-V"])
      .trim()
      .replace(/^tmux\s+/, "");
  } catch {
    return null;
  }
}

/** The RUNNING server's version, null when none runs. A server started before
 *  an upgrade keeps its old version until every tmux session has closed. */
function serverVersion() {
  try {
    return execImpl(["display-message", "-p", "#{version}"]).trim() || null;
  } catch {
    return null;
  }
}

module.exports = {
  __setScopeImpl,
  session,
  pane,
  hasSession,
  newSession,
  enableMouse,
  paneCommand,
  sendCommand,
  sendText,
  pasteText,
  capturePane,
  sendKey,
  killSession,
  listSessions,
  liveSessions,
  isTmuxAvailable,
  clientVersion,
  serverVersion,
  serverPid,
  memberAttach,
  __setExecImpl,
  __setAccountImpl,
  __settle,
  __reset,
};