ninox_core/

tmux.rs

use anyhow::{Context, Result};
use tokio::process::Command;

/// Name of the private tmux server socket all ninox sessions live on.
/// Isolates ninox from the user's own tmux server and ~/.tmux.conf — and,
/// via `is_test_binary`, isolates the test suite's own tmux server from the
/// real running app's. Without this, `cargo test` (or manually clearing a
/// stale "duplicate session" test collision with `tmux -L ninox
/// kill-server`) kills the user's actual live orchestrator/worker panes,
/// since tests and the production app previously shared this exact socket.
/// Not a `const` because it depends on that runtime check.
pub(crate) fn socket() -> &'static str {
    if is_test_binary() { "ninox-test" } else { "ninox" }
}

/// Cargo places every test/bench/example binary's compiled output under
/// `target/<profile>/deps/` (e.g. `target/debug/deps/ninox_core-<hash>`),
/// while the real `cargo build`/`cargo run` binary lives directly at
/// `target/<profile>/<name>` with no `deps` path component. Checking for
/// that segment is a reliable, zero-config way to tell "am I a test binary"
/// apart from "am I the real app" — no env var, no per-test setup required,
/// so it can't race under parallel test execution the way a shared env var
/// would (see `lifecycle::usage::ENV_TEST_GUARD` for a case where that
/// exact hazard already had to be worked around once in this codebase).
fn is_test_binary() -> bool {
    std::env::current_exe()
        .ok()
        .is_some_and(|p| p.components().any(|c| c.as_os_str() == "deps"))
}

/// Parse a `tmux -V` version string (e.g. "tmux 3.4" or "tmux 3.5a") into
/// (major, minor). Unparseable input degrades to (0, 0) so version checks
/// fail closed rather than panicking.
fn parse_tmux_version(raw: &str) -> (u32, u32) {
    let ver = raw.trim().strip_prefix("tmux ").unwrap_or(raw.trim());
    let mut parts = ver.split(|c: char| !c.is_ascii_digit());
    let major: u32 = parts.next().and_then(|s| s.parse().ok()).unwrap_or(0);
    let minor: u32 = parts.next().and_then(|s| s.parse().ok()).unwrap_or(0);
    (major, minor)
}

/// The installed tmux version, detected synchronously (a single fast `tmux
/// -V` call). Used to build a config that only uses directives the running
/// tmux actually supports, and by tests to gate assertions that only hold on
/// newer tmux. Returns (0, 0) if tmux is missing or unparseable.
pub fn detected_version_sync() -> (u32, u32) {
    std::process::Command::new("tmux")
        .arg("-V")
        .output()
        .ok()
        .filter(|o| o.status.success())
        .map(|o| parse_tmux_version(&String::from_utf8_lossy(&o.stdout)))
        .unwrap_or((0, 0))
}

/// `extended-keys-format` (needed to disambiguate keys like Shift+Enter as
/// CSI-u) was added in tmux 3.5; older tmux rejects the option outright.
fn supports_extended_keys_format((major, minor): (u32, u32)) -> bool {
    (major, minor) >= (3, 5)
}

/// Build the ninox-managed server config (spec §"Dedicated tmux server"),
/// tailored to what `version` actually supports so we never ask an older
/// tmux to parse a directive it doesn't understand.
fn server_config_for_version(version: (u32, u32)) -> String {
    let mut cfg = String::from("# Managed by ninox — rewritten on every app start. Do not edit.\n");
    cfg.push_str("set -g  default-terminal \"tmux-256color\"\n");
    cfg.push_str("set -as terminal-features \"xterm*:RGB:usstyle:extkeys:hyperlinks\"\n");
    cfg.push_str("set -s  extended-keys always\n");
    if supports_extended_keys_format(version) {
        cfg.push_str("set -s  extended-keys-format csi-u\n");
    }
    cfg.push_str("set -g  history-limit 100000\n");
    cfg.push_str("set -g  status off\n");
    cfg.push_str("set -s  escape-time 0\n");
    cfg.push_str("set -g  window-size latest\n");
    cfg.push_str("set -g  allow-passthrough on\n");
    cfg.push_str("set -g  focus-events on\n");
    // Keep the server alive with zero sessions/clients so the one-time
    // bootstrap in `ensure_server_ready` (a bare `start-server`, no session)
    // doesn't get reaped before later commands reach it.
    cfg.push_str("set -g  exit-empty off\n");
    cfg
}

fn config_path() -> std::path::PathBuf {
    let file = if is_test_binary() { "tmux-test.conf" } else { "tmux.conf" };
    dirs::config_dir()
        .unwrap_or_else(|| std::path::PathBuf::from("/tmp"))
        .join("ninox")
        .join(file)
}

/// Write the ninox tmux server config. Called once at startup so config
/// drift between app versions cannot accumulate. The content is tailored to
/// the installed tmux version (see `server_config_for_version`).
pub fn write_server_config() -> Result<std::path::PathBuf> {
    let path = config_path();
    if let Some(dir) = path.parent() {
        std::fs::create_dir_all(dir)?;
    }
    std::fs::write(&path, server_config_for_version(detected_version_sync()))?;
    Ok(path)
}

/// argv prefix routing a tmux invocation to the private ninox server.
/// Does NOT include `-f`: config application is handled once, deterministically,
/// by `ensure_server_ready` (see its doc comment for why `-f` on every
/// invocation is not safe to rely on).
fn socket_args() -> Vec<String> {
    vec!["-L".into(), socket().into()]
}

/// Fail fast if tmux is missing or older than 3.2 (extended-keys support).
pub async fn require_version() -> Result<()> {
    let out = Command::new("tmux").arg("-V").output().await
        .context("tmux not found — install tmux (brew install tmux / apt install tmux)")?;
    let v = String::from_utf8_lossy(&out.stdout);
    let ver = v.trim().strip_prefix("tmux ").unwrap_or(v.trim());
    let version = parse_tmux_version(&v);
    anyhow::ensure!(
        version >= (3, 2),
        "ninox requires tmux >= 3.2 for extended keyboard support; found {ver}"
    );
    if !supports_extended_keys_format(version) {
        tracing::warn!(
            "tmux {ver} detected — extended-keys-format csi-u requires tmux >= 3.5; \
             Shift+Enter and other disambiguated keys may not reach apps correctly \
             on this version"
        );
    }
    Ok(())
}

/// Ensure the ninox config file exists, the private tmux server is running,
/// and that server has our config applied — exactly once per process, no
/// matter how many concurrent callers race to be first.
///
/// Why this exists: `tmux -f <path>` silently falls back to built-in
/// defaults — no error, nothing on stderr — if `<path>` doesn't exist yet
/// (verified directly: `tmux -f /does/not/exist new-session -d ...` exits 0
/// with default options). `write_server_config` is normally called once by
/// `main` before any session is created, but nothing else guarantees that
/// ordering — a caller that creates a session before the config file has
/// ever been written (e.g. this crate's test suite, or a future call site)
/// gets a server silently running with tmux defaults (status bar visible,
/// 2000-line history, no window-size follow) for that server's entire
/// lifetime, since config is only read once, at server start. Reproduced
/// deterministically on a from-scratch Linux `$HOME` (no prior ninox run to
/// have left the file behind) — exactly the shape of a fresh CI runner or a
/// fresh install, which is why this only ever showed up on Ubuntu CI.
/// Funnelling every ninox-socket command through this guard first means the
/// file is written, and the server started against it, exactly once, before
/// anything else can race ahead and start the server unconfigured.
async fn ensure_server_ready() {
    static READY: tokio::sync::OnceCell<()> = tokio::sync::OnceCell::const_new();
    READY.get_or_init(|| async {
        if let Err(e) = write_server_config() {
            tracing::warn!("failed to write tmux config: {e}");
        }
        let conf = config_path().display().to_string();
        // `start-server` needs no session; `exit-empty off` (in our config)
        // keeps the freshly-started server alive with none. If a server
        // from an older ninox run is already up, `-f` here is a no-op, so
        // `source-file` re-applies our (possibly newer) config explicitly —
        // this is also what makes "rewritten on every app start" true for a
        // long-lived server, not just for the file on disk.
        let _ = run_raw(&["-L", socket(), "-f", &conf, "start-server"]).await;
        let _ = run_raw(&["-L", socket(), "source-file", &conf]).await;
    }).await;
}

fn is_missing_session(e: &anyhow::Error) -> bool {
    let msg = e.to_string();
    msg.contains("can't find session")
        || msg.contains("session not found")
        || msg.contains("no server running")
        || msg.contains("no sessions")
        // tmux's message for a session-targeted command (has-session,
        // kill-session, list-panes, ...) when the server is up but holds
        // zero sessions total — a state that's now reachable because
        // `ensure_server_ready` keeps the ninox server alive empty
        // (`exit-empty off`) rather than only ever existing once a real
        // session has been created on it.
        || msg.contains("no current target")
}

/// Metadata about a running tmux session from `list-sessions`.
#[derive(Debug, Clone)]
pub struct TmuxSession {
    pub id:         String,
    pub created_ms: i64,
    pub pid:        Option<u32>,
    pub tty:        Option<String>,
}

/// Run a tmux subcommand against the ninox server and return trimmed stdout.
async fn run(args: &[&str]) -> Result<String> {
    ensure_server_ready().await;
    let prefix = socket_args();
    let mut full: Vec<&str> = prefix.iter().map(String::as_str).collect();
    full.extend_from_slice(args);
    run_raw(&full).await
}

/// Run tmux with NO socket routing (the user's default server) — only for
/// legacy sessions created by pre-private-socket builds.
async fn run_default(args: &[&str]) -> Result<String> {
    run_raw(args).await
}

/// The old `run` body, renamed: spawn tmux with exactly these args.
async fn run_raw(args: &[&str]) -> Result<String> {
    let out = Command::new("tmux")
        .args(args)
        .kill_on_drop(true)
        .output()
        .await
        .context("tmux not found — install tmux (brew install tmux / apt install tmux)")?;
    if !out.status.success() {
        let stderr = String::from_utf8_lossy(&out.stderr);
        anyhow::bail!("tmux {:?} failed: {}", args, stderr.trim());
    }
    Ok(String::from_utf8_lossy(&out.stdout).trim_end().to_string())
}

/// Run a command that targets an existing session. Tries the ninox server
/// first, then falls back to the default server for legacy sessions.
async fn run_session_scoped(args: &[&str]) -> Result<String> {
    match run(args).await {
        Err(e) if is_missing_session(&e) => run_default(args).await,
        other => other,
    }
}

/// Run tmux; swallow errors and return empty string on failure.
/// Logs warnings for debugging; does not propagate errors.
async fn run_best_effort(args: &[&str]) -> String {
    match run(args).await {
        Ok(result) => result,
        Err(e) => {
            tracing::warn!("tmux {:?} failed (ignored): {}", args, e);
            String::new()
        }
    }
}

/// `run_best_effort`, but against the default (non-ninox) socket — used to
/// surface legacy sessions from pre-private-socket builds.
async fn run_best_effort_default(args: &[&str]) -> String {
    match run_default(args).await {
        Ok(result) => result,
        Err(e) => {
            tracing::warn!("tmux (default socket) {:?} failed (ignored): {}", args, e);
            String::new()
        }
    }
}

/// Shell-quote a string to prevent injection in tmux commands.
/// Wraps the string in single quotes and escapes interior single quotes.
fn shell_quote(s: &str) -> String {
    format!("'{}'", s.replace('\'', "'\\''"))
}

/// Create a detached tmux session.  Kills a stale session with the same name
/// if one exists, then hides the status bar so the terminal widget is clean.
pub async fn create_session(
    id:        &str,
    workspace: &str,
    cmd:       &str,
    env:       &[(&str, &str)],
) -> Result<()> {
    // tmux does NOT fail on a nonexistent `-c` dir (verified on 3.6a: exit 0,
    // pane silently starts in $HOME). For harnesses with cwd-scoped state —
    // claude-code keys conversations to the directory it starts in — that
    // fallback breaks `--resume` with "No conversation found with session
    // ID". Fail loudly here instead.
    anyhow::ensure!(
        std::path::Path::new(workspace).is_dir(),
        "workspace directory does not exist: {workspace}"
    );
    // Build -e KEY=VALUE pairs
    let mut env_pairs: Vec<String> = Vec::new();
    for (k, v) in env {
        anyhow::ensure!(!k.contains('='), "env key must not contain '=': {k}");
        env_pairs.push(format!("{k}={v}"));
    }
    let mut extra: Vec<&str> = Vec::new();
    for pair in &env_pairs {
        // Values are passed as separate argv tokens via execve — no shell quoting needed.
        extra.push("-e");
        extra.push(pair.as_str());
    }

    // Wrap the command in a login shell so the full user PATH is available.
    // tmux sessions do not inherit shell rc files, so tools installed via
    // nvm / cargo / homebrew etc. would not be found otherwise.
    let shell = std::env::var("SHELL").unwrap_or_else(|_| "/bin/bash".to_string());
    let shell_cmd = format!("{shell} -l -c {}", shell_quote(cmd));

    // Fix the terminal dimensions to match the canvas.  The canvas is roughly
    // (window_width - 220px sidebar) / 7.8px_per_col ≈ 135 cols on a 1280-wide
    // window.  Use 140 as a safe default; too-wide values push Claude Code's
    // centered content off-screen.
    let mut base = vec!["new-session", "-d", "-s", id, "-x", "140", "-y", "50", "-c", workspace];
    base.extend_from_slice(&extra);
    base.push(&shell_cmd);

    // A duplicate name means a LIVE tmux session already exists under this
    // id. Killing it to make room (the old behavior) silently destroys a
    // running agent whenever the store and tmux disagree about what exists —
    // surface the conflict to the caller instead; the spawn UI shows it.
    run(&base).await.map(|_| ())
}

/// Kill a tmux session.  Succeeds even if the session doesn't exist.
/// `run_session_scoped` falls back to the default socket when the session
/// isn't found on the ninox server, so legacy sessions are killed there too.
pub async fn kill_session(id: &str) -> Result<()> {
    match run_session_scoped(&["kill-session", "-t", id]).await {
        Ok(_) => Ok(()),
        Err(e) => {
            if is_missing_session(&e) {
                Ok(())
            } else {
                Err(e)
            }
        }
    }
}

/// Returns `true` if a tmux session with this name is currently running.
pub async fn has_session(id: &str) -> bool {
    run_session_scoped(&["has-session", "-t", id]).await.is_ok()
}

/// List every live tmux session.  Sessions on the ninox server are listed
/// first; legacy sessions on the default server are appended for any id not
/// already seen (ninox socket wins on conflicts).
pub async fn list_sessions() -> Result<Vec<TmuxSession>> {
    // A literal tab column separator is mangled by tmux's -F formatter on
    // older tmux (verified: tmux 3.4 rewrites an embedded tab byte in a -F
    // template to `_` in the output, so every field collapses into one;
    // tmux 3.6 passes it through untouched). `|` survives on both and can't
    // appear in any of these fields (ninox controls session-name shape;
    // the rest are numeric or a `/dev/...` path).
    const SEP: &str = "|";
    let fmt = format!("#{{session_name}}{SEP}#{{session_created}}{SEP}#{{pane_pid}}{SEP}#{{pane_tty}}");
    let ninox_raw = run_best_effort(&["list-sessions", "-F", &fmt]).await;
    let default_raw = run_best_effort_default(&["list-sessions", "-F", &fmt]).await;

    let mut seen = std::collections::HashSet::new();
    let mut sessions = Vec::new();
    for raw in [ninox_raw, default_raw] {
        for line in raw.lines().filter(|l| !l.is_empty()) {
            let mut cols = line.splitn(4, SEP);
            let Some(id) = cols.next().map(str::to_string) else { continue };
            if !seen.insert(id.clone()) {
                continue;
            }
            let sec = cols.next().and_then(|s| s.parse::<i64>().ok()).unwrap_or(0);
            let pid = cols.next().and_then(|s| s.parse::<u32>().ok());
            let tty = cols.next().map(str::to_string).filter(|s| !s.is_empty());
            sessions.push(TmuxSession { id, created_ms: sec * 1000, pid, tty });
        }
    }
    Ok(sessions)
}

/// Return the tty device path (e.g. `/dev/ttys003`) for the session's active pane.
pub async fn get_pane_tty(id: &str) -> Result<Option<String>> {
    let out = run_session_scoped(&["list-panes", "-t", id, "-F", "#{pane_tty}"]).await?;
    Ok(out
        .lines()
        .next()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty()))
}

/// Start piping pane output to `dest_path` (regular file, not FIFO).
/// Does NOT use `-o` so it force-restarts any existing pipe — required for reconnect.
pub async fn pipe_pane(id: &str, dest_path: &str) -> Result<()> {
    run_session_scoped(&["pipe-pane", "-t", id, &format!("cat > {}", shell_quote(dest_path))]).await?;
    Ok(())
}

/// Full argv for `tmux attach` for this session (element 0 is "tmux"),
/// resolving whether it lives on the ninox or the legacy default server.
pub async fn attach_args(session_id: &str) -> Vec<String> {
    let mut argv = vec!["tmux".to_string()];
    if run(&["has-session", "-t", session_id]).await.is_ok() {
        argv.extend(socket_args());
    } else {
        tracing::warn!(
            "session {session_id} predates the ninox socket — attaching on the \
             legacy default tmux server without the managed config (extended \
             keys / resize guarantees are degraded until it terminates naturally)"
        );
    }
    argv.extend(["attach-session", "-t", session_id].map(String::from));
    argv
}

/// Number of scrolled-off lines tmux holds for this pane.
pub async fn history_size(session_id: &str) -> i64 {
    run_session_scoped(&["display-message", "-p", "-t", session_id, "#{history_size}"])
        .await
        .ok()
        .and_then(|s| s.trim().parse().ok())
        .unwrap_or(0)
}

/// Capture styled pane content for the line range [start, end], where
/// negative indices address history (-1 = newest history line). No -J:
/// lines stay wrapped at pane width so they re-parse at the same columns.
pub async fn capture_history(session_id: &str, start: i64, end: i64) -> Vec<u8> {
    run_session_scoped(&[
        "capture-pane", "-p", "-e", "-t", session_id,
        "-S", &start.to_string(), "-E", &end.to_string(),
    ])
    .await
    .map(|s| s.into_bytes())
    .unwrap_or_default()
}

/// Send text to a tmux session as if typed at the keyboard.
/// The text is followed by Enter so the agent receives and acts on it.
/// Uses `tmux send-keys -l` (literal mode) to avoid tmux interpreting
/// special characters like `{`, `}`, arrows.
pub async fn send_keys(session_id: &str, text: &str) -> Result<()> {
    // Send the message text in literal mode
    run_session_scoped(&["send-keys", "-t", session_id, "-l", text]).await?;
    // Send Enter to submit
    run_session_scoped(&["send-keys", "-t", session_id, "Enter"]).await?;
    Ok(())
}

/// Write `bytes` to the session's master PTY via tmux's paste-buffer
/// mechanism — the supported way to inject raw input (as opposed to
/// `send-keys`, which tmux may reinterpret). `tmp_path` is a scratch file
/// used to stage the buffer contents and is removed afterwards regardless
/// of outcome.
pub async fn paste_buffer(session_id: &str, buf_name: &str, tmp_path: &str, bytes: &[u8]) -> Result<()> {
    std::fs::write(tmp_path, bytes)?;
    let result = run_session_scoped(&[
        "load-buffer", "-b", buf_name, tmp_path, ";",
        "paste-buffer", "-b", buf_name, "-t", session_id, "-d",
    ]).await;
    let _ = std::fs::remove_file(tmp_path);
    result.map(|_| ())
}

#[cfg(test)]
mod tests {
    use super::*;
    use tokio::time::{sleep, Duration};

    fn tmux_available() -> bool {
        std::process::Command::new("tmux")
            .args(["-V"])
            .output()
            .map(|o| o.status.success())
            .unwrap_or(false)
    }

    fn unique_id() -> String {
        // Millis alone collide when parallel test threads start within the
        // same tick, producing duplicate tmux session names; a per-process
        // counter guarantees uniqueness regardless of clock resolution (see
        // the same fix in client.rs's unique_id).
        static COUNTER: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(0);
        let n = COUNTER.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
        format!(
            "test-{}-{n}",
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_millis()
        )
    }

    /// The whole point of `is_test_binary`: every test in this suite must
    /// resolve to the isolated socket, never the real app's `"ninox"` — this
    /// is what stops `cargo test` (run by a developer with the real app open)
    /// from ever touching, or a stale-session cleanup from ever killing, a
    /// live session the user is actually using.
    #[test]
    fn tests_resolve_to_the_isolated_socket_not_the_real_apps() {
        assert!(is_test_binary(), "the test binary itself must be detected as a test binary");
        assert_eq!(socket(), "ninox-test");
        assert_ne!(socket(), "ninox");
    }

    #[tokio::test]
    async fn create_session_fails_when_workspace_dir_is_missing() {
        if !tmux_available() { return; }
        let id = unique_id();
        // tmux 3.6a exits 0 for `new-session -c <missing-dir>` and silently
        // starts the pane in $HOME instead — which made `claude --resume`
        // fail with "No conversation found with session ID" (conversations
        // are cwd-scoped). create_session must fail loudly instead.
        let result = create_session(&id, "/definitely/not/a/real/dir", "sleep 30", &[]).await;
        assert!(result.is_err(), "missing workspace must be an error, not a silent $HOME fallback");
        assert!(!has_session(&id).await, "no session may be left behind on failure");
    }

    #[tokio::test]
    async fn create_and_has_and_kill() {
        if !tmux_available() { return; }
        let id = unique_id();
        create_session(&id, "/tmp", "sleep 30", &[]).await.unwrap();
        assert!(has_session(&id).await);
        kill_session(&id).await.unwrap();
        assert!(!has_session(&id).await);
    }

    #[tokio::test]
    async fn list_includes_created() {
        if !tmux_available() { return; }
        let id = unique_id();
        create_session(&id, "/tmp", "sleep 30", &[]).await.unwrap();
        let sessions = list_sessions().await.unwrap();
        assert!(sessions.iter().any(|s| s.id == id));
        kill_session(&id).await.unwrap();
    }

    #[tokio::test]
    async fn get_pane_tty_returns_dev_path() {
        if !tmux_available() { return; }
        let id = unique_id();
        create_session(&id, "/tmp", "sleep 30", &[]).await.unwrap();
        let tty = get_pane_tty(&id).await.unwrap();
        assert!(tty.map(|t| t.starts_with("/dev/")).unwrap_or(false));
        kill_session(&id).await.unwrap();
    }

    #[tokio::test]
    async fn send_keys_builds_correct_command() {
        // This test validates our argument construction without actually calling tmux.
        // We test the shell_quote helper used by send_keys.
        let quoted = shell_quote("hello world");
        assert_eq!(quoted, "'hello world'");
        let with_apostrophe = shell_quote("don't");
        assert_eq!(with_apostrophe, "'don'\\''t'");
    }

    #[test]
    fn server_config_is_written_and_contains_required_settings() {
        let path = write_server_config().unwrap();
        let body = std::fs::read_to_string(&path).unwrap();
        for required in [
            "default-terminal \"tmux-256color\"",
            "extended-keys always",
            "history-limit 100000",
            "status off",
            "window-size latest",
            "allow-passthrough on",
            "exit-empty off",
        ] {
            assert!(body.contains(required), "config missing {required:?}\n{body}");
        }
        // extended-keys-format requires tmux >= 3.5 (older tmux rejects the
        // option outright); the written config must match what's installed.
        if supports_extended_keys_format(detected_version_sync()) {
            assert!(body.contains("extended-keys-format csi-u"),
                    "config missing extended-keys-format on tmux >= 3.5\n{body}");
        } else {
            assert!(!body.contains("extended-keys-format"),
                    "config must omit extended-keys-format on tmux < 3.5 (rejected as invalid)\n{body}");
        }
    }

    #[tokio::test]
    async fn require_version_passes_on_installed_tmux() {
        if !tmux_available() { return; }
        require_version().await.unwrap();
    }

    #[tokio::test]
    async fn sessions_are_created_on_the_ninox_socket() {
        if !tmux_available() { return; }
        let id = unique_id();
        create_session(&id, "/tmp", "sleep 30", &[]).await.unwrap();
        // Visible via -L ninox …
        assert!(has_session(&id).await);
        // … and NOT on the default socket.
        let default_out = std::process::Command::new("tmux")
            .args(["has-session", "-t", &id])
            .output()
            .unwrap();
        assert!(!default_out.status.success(), "session leaked onto the default socket");
        kill_session(&id).await.unwrap();
    }

    #[tokio::test]
    async fn legacy_default_socket_sessions_are_still_reachable() {
        if !tmux_available() { return; }
        let id = unique_id();
        // Simulate a session created by an older build: default socket, no -L.
        let st = std::process::Command::new("tmux")
            .args(["new-session", "-d", "-s", &id, "-x", "80", "-y", "24", "sleep 30"])
            .status()
            .unwrap();
        assert!(st.success());
        assert!(has_session(&id).await, "has_session must fall back to the default socket");
        let argv = attach_args(&id).await;
        assert!(!argv.contains(&"-L".to_string()), "legacy session must attach without -L: {argv:?}");
        kill_session(&id).await.unwrap(); // must kill on the default socket too
        assert!(!has_session(&id).await);
    }

    #[tokio::test]
    async fn capture_history_returns_scrolled_off_lines() {
        if !tmux_available() { return; }
        let id = unique_id();
        // 50-row pane; print 80 numbered lines so the earliest ones scroll into history.
        create_session(&id, "/tmp", "bash -c 'for i in $(seq 1 80); do echo line-$i; done; sleep 30'", &[]).await.unwrap();
        sleep(Duration::from_millis(500)).await;
        let hist = history_size(&id).await;
        assert!(hist > 0, "expected history to accumulate, got {hist}");
        let bytes = capture_history(&id, -hist, -1).await;
        let text = String::from_utf8_lossy(&bytes);
        assert!(text.contains("line-1"), "oldest line missing from history capture: {text}");
        kill_session(&id).await.unwrap();
    }
}