path: root/tests/detach_reattach.rs

//! Integration tests for detach/reattach flow.
//!

#![cfg(unix)]

pub mod support;

use std::fs;
use std::io::{BufRead, BufReader, Write};
use std::os::unix::net::UnixStream;
use std::path::PathBuf;
use std::sync::{Mutex, MutexGuard, OnceLock};
use std::thread;
use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};

use portable_pty::{native_pty_system, Child, CommandBuilder, MasterPty, PtySize};
use serde_json::Value;
use support::{
    cleanup_test_base, client_shell_handshake, drain_messages, register_runtime_dir,
    register_spawned_herdr_pid, send_detach, unregister_spawned_herdr_pid, wait_for_disconnect,
    wait_for_socket, wait_until, CURRENT_ENDPOINT_PROTOCOL_GENERATION as CURRENT_PROTOCOL,
};

const CUSTOM_HEADLESS_SIZE_CONFIG: &str = r#"onboarding = false

[server]
headless_cols = 132
headless_rows = 41

[ui]
sidebar_start_collapsed = true
sidebar_collapsed_mode = "hidden"
hide_tab_bar_when_single_tab = true
pane_scrollbars = false
"#;

fn unique_test_dir() -> PathBuf {
    let nanos = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_nanos())
        .unwrap_or(0);
    PathBuf::from(format!(
        "/tmp/herdr-detach-test-{}-{nanos}",
        std::process::id()
    ))
}

struct SpawnedHerdr {
    _master: Box<dyn MasterPty + Send>,
    child: Box<dyn Child + Send + Sync>,
}

impl Drop for SpawnedHerdr {
    fn drop(&mut self) {
        let pid = self.child.process_id();
        let _ = self.child.kill();

        if let Some(pid) = pid {
            let deadline = Instant::now() + Duration::from_secs(2);
            while Instant::now() < deadline {
                let mut status = 0;
                let result =
                    unsafe { libc::waitpid(pid as libc::pid_t, &mut status, libc::WNOHANG) };
                if result == pid as libc::pid_t || result == -1 {
                    break;
                }
                thread::sleep(Duration::from_millis(20));
            }

            unregister_spawned_herdr_pid(Some(pid));
        }
    }
}

fn cleanup_spawned_herdr(spawned: SpawnedHerdr, base: PathBuf) {
    drop(spawned);
    cleanup_test_base(&base);
}

fn test_lock() -> MutexGuard<'static, ()> {
    static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
    LOCK.get_or_init(|| Mutex::new(()))
        .lock()
        .unwrap_or_else(|poisoned| poisoned.into_inner())
}

fn spawn_server(
    config_home: &PathBuf,
    runtime_dir: &PathBuf,
    api_socket_path: &PathBuf,
    client_socket_path: &PathBuf,
) -> SpawnedHerdr {
    spawn_server_with_config(
        config_home,
        runtime_dir,
        api_socket_path,
        client_socket_path,
        "onboarding = false\n",
    )
}

fn spawn_server_with_config(
    config_home: &PathBuf,
    runtime_dir: &PathBuf,
    api_socket_path: &PathBuf,
    _client_socket_path: &PathBuf,
    config: &str,
) -> SpawnedHerdr {
    fs::create_dir_all(config_home.join("herdr")).unwrap();
    fs::create_dir_all(runtime_dir).unwrap();
    register_runtime_dir(runtime_dir);
    fs::write(config_home.join("herdr/config.toml"), config).unwrap();

    let pair = native_pty_system()
        .openpty(PtySize {
            rows: 24,
            cols: 80,
            pixel_width: 0,
            pixel_height: 0,
        })
        .unwrap();

    let mut cmd = CommandBuilder::new(env!("CARGO_BIN_EXE_herdr"));
    cmd.arg("server");
    cmd.env("XDG_CONFIG_HOME", config_home);
    cmd.env("XDG_RUNTIME_DIR", runtime_dir);
    cmd.env("HERDR_SOCKET_PATH", api_socket_path);
    cmd.env_remove("HERDR_CLIENT_SOCKET_PATH");
    cmd.env("HERDR_CONFIG_PATH", config_home.join("herdr/config.toml"));
    cmd.env("SHELL", "/bin/sh");
    cmd.env_remove("HERDR_ENV");

    let child = pair.slave.spawn_command(cmd).unwrap();
    register_spawned_herdr_pid(child.process_id());
    drop(pair.slave);

    SpawnedHerdr {
        _master: pair.master,
        child,
    }
}

fn ping_socket(socket_path: &PathBuf) -> String {
    let mut stream = UnixStream::connect(socket_path).expect("should connect to API socket");

    let request = r#"{"id":"1","method":"ping","params":{}}"#;
    writeln!(stream, "{}", request).unwrap();

    let mut reader = BufReader::new(stream);
    let mut response = String::new();
    reader.read_line(&mut response).unwrap();
    response.trim().to_string()
}

fn send_json_request(socket_path: &PathBuf, request: &str) -> Value {
    let mut stream = UnixStream::connect(socket_path).expect("should connect to API socket");
    writeln!(stream, "{}", request).unwrap();

    let mut reader = BufReader::new(stream);
    let mut response = String::new();
    reader.read_line(&mut response).unwrap();
    serde_json::from_str(&response).expect("response should be valid JSON")
}

fn workspace_create(socket_path: &PathBuf, label: &str) -> Value {
    send_json_request(
        socket_path,
        &format!(
            r#"{{"id":"workspace_create","method":"workspace.create","params":{{"label":"{label}"}}}}"#
        ),
    )
}

fn workspace_list(socket_path: &PathBuf) -> Value {
    send_json_request(
        socket_path,
        r#"{"id":"workspace_list","method":"workspace.list","params":{}}"#,
    )
}

fn pane_list(socket_path: &PathBuf, workspace_id: &str) -> Value {
    send_json_request(
        socket_path,
        &format!(
            r#"{{"id":"pane_list","method":"pane.list","params":{{"workspace_id":"{workspace_id}"}}}}"#
        ),
    )
}

fn pane_read_recent(socket_path: &PathBuf, pane_id: &str) -> Value {
    send_json_request(
        socket_path,
        &format!(
            r#"{{"id":"pane_read","method":"pane.read","params":{{"pane_id":"{pane_id}","source":"recent"}}}}"#
        ),
    )
}

fn pane_read_recent_text(socket_path: &PathBuf, pane_id: &str) -> String {
    pane_read_recent(socket_path, pane_id)["result"]["read"]["text"]
        .as_str()
        .unwrap_or_default()
        .to_string()
}

fn pane_send_text(socket_path: &PathBuf, pane_id: &str, text: &str) -> Value {
    send_json_request(
        socket_path,
        &format!(
            r#"{{"id":"pane_send_text","method":"pane.send_text","params":{{"pane_id":"{pane_id}","text":{}}}}}"#,
            serde_json::to_string(text).unwrap()
        ),
    )
}

fn parse_size_after_marker(text: &str, marker: &str) -> Option<(u16, u16)> {
    let lines: Vec<&str> = text.lines().collect();
    for (idx, line) in lines.iter().enumerate() {
        if !line.contains(marker) {
            continue;
        }
        for candidate in lines.iter().skip(idx + 1).take(6) {
            let mut parts = candidate.split_whitespace();
            let Some(rows) = parts.next().and_then(|part| part.parse::<u16>().ok()) else {
                continue;
            };
            let Some(cols) = parts.next().and_then(|part| part.parse::<u16>().ok()) else {
                continue;
            };
            if parts.next().is_none() {
                return Some((rows, cols));
            }
        }
    }
    None
}

fn read_pane_tty_size_after_marker(
    socket_path: &PathBuf,
    pane_id: &str,
    marker: &str,
    timeout: Duration,
) -> (u16, u16) {
    pane_send_text(socket_path, pane_id, &format!("echo {marker}; stty size\n"));

    let deadline = Instant::now() + timeout;
    let mut last_text = String::new();
    while Instant::now() < deadline {
        last_text = pane_read_recent_text(socket_path, pane_id);
        if let Some(size) = parse_size_after_marker(&last_text, marker) {
            return size;
        }
        thread::sleep(Duration::from_millis(50));
    }

    panic!("did not observe tty size after marker {marker}. pane output:\n{last_text}");
}

fn workspace_id_by_label(response: &Value, label: &str) -> String {
    response["result"]["workspaces"]
        .as_array()
        .expect("workspace.list should return an array")
        .iter()
        .find(|workspace| workspace["label"] == label)
        .and_then(|workspace| workspace["workspace_id"].as_str())
        .expect("workspace with expected label should exist")
        .to_string()
}

fn first_pane_id(response: &Value) -> String {
    response["result"]["panes"]
        .as_array()
        .expect("pane.list should return an array")
        .first()
        .and_then(|pane| pane["pane_id"].as_str())
        .expect("pane.list should contain at least one pane")
        .to_string()
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

#[test]
fn explicit_detach_message_causes_clean_disconnect() {
    // Client sends ClientMessage::Detach
    // directly (not via keybind), server handles it gracefully.
    // This is the flow when the client process is exiting cleanly (Ctrl+C).
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    // Connect and handshake.
    let mut stream = UnixStream::connect(&client_socket).expect("should connect");
    let (version, error) = client_shell_handshake(&mut stream, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Drain initial frames.
    drain_messages(&mut stream);

    // Send ClientMessage::Detach directly.
    send_detach(&mut stream).expect("send detach message");

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist after client Detach message"
    );

    // Verify server is still alive.
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should persist after client Detach message: {response}"
    );

    // The client connection should eventually be closed.
    // After sending Detach, the server removes the client.
    // We may still receive a few queued frames before the connection closes.
    let got_eof =
        wait_for_disconnect(&mut stream, Duration::from_secs(2)).expect("wait for disconnect");
    assert!(
        got_eof,
        "client connection should be closed after explicit Detach message"
    );

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn reattach_after_detach_shows_current_state() {
    // Flow:
    // 1. Start server
    // 2. Connect client A, create a workspace via API
    // 3. Client A detaches
    // 4. Connect client B (reattach), verify it receives a frame
    // 5. Verify client B can see the workspace created by client A
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    // --- Client A ---
    let mut stream_a = UnixStream::connect(&client_socket).expect("client A should connect");
    let (version, error) = client_shell_handshake(&mut stream_a, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Drain initial frames.
    drain_messages(&mut stream_a);

    // Create a workspace via API while client A is attached.
    let mut ws_stream = UnixStream::connect(&api_socket).expect("connect to API");
    let request = r#"{"id":"1","method":"workspace.create","params":{"label":"reattach-test"}}"#;
    writeln!(ws_stream, "{}", request).unwrap();
    let mut reader = BufReader::new(ws_stream);
    let mut ws_response = String::new();
    reader.read_line(&mut ws_response).unwrap();
    assert!(
        ws_response.contains("workspace_created") || ws_response.contains("ok"),
        "workspace creation should succeed: {ws_response}"
    );

    // Client A detaches (send ClientMessage::Detach).
    send_detach(&mut stream_a).expect("send detach");

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist after detach"
    );

    // Verify server is still alive.
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should persist after detach: {response}"
    );

    // --- Client B (reattach) ---
    let mut stream_b = UnixStream::connect(&client_socket).expect("client B should connect");
    let (version, error) = client_shell_handshake(&mut stream_b, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(
        error.is_none(),
        "reattach handshake should succeed: {:?}",
        error
    );

    // Client B receives the client-owned shell projection.
    // including the workspace created while client A was attached.
    support::wait_for_client_shell_bootstrap(&mut stream_b, Duration::from_secs(5))
        .expect("client shell bootstrap");

    // Verify the workspace still exists via API.
    let mut list_stream = UnixStream::connect(&api_socket).expect("connect to API");
    let list_request = r#"{"id":"2","method":"workspace.list","params":{}}"#;
    writeln!(list_stream, "{}", list_request).unwrap();
    let mut list_reader = BufReader::new(list_stream);
    let mut list_response = String::new();
    list_reader.read_line(&mut list_response).unwrap();
    assert!(
        list_response.contains("reattach-test"),
        "workspace should still exist after detach/reattach: {list_response}"
    );

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn processes_survive_during_and_after_detach() {
    // PTY processes continue running during and after detach.
    //
    // Simplified flow:
    // 1. Start server
    // 2. Connect client, send "echo SURVIVED" to the pane
    // 3. Detach client
    // 4. Verify server is still alive and API works
    // 5. Reattach and verify we can receive a frame
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    // Verify server starts with a workspace (session restore or fresh state).
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should respond to ping: {response}"
    );

    // Connect and handshake.
    let mut stream = UnixStream::connect(&client_socket).expect("should connect");
    let (version, error) = client_shell_handshake(&mut stream, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Drain initial frames.
    drain_messages(&mut stream);

    // Drive the pane through the JSON API; the shell transport carries only
    // client-composed UI state, not legacy raw shell input.
    let created = workspace_create(&api_socket, "process-survival");
    let pane_id = created["result"]["root_pane"]["pane_id"]
        .as_str()
        .expect("root pane id")
        .to_string();
    pane_send_text(&api_socket, &pane_id, "echo SURVIVED_DETACH\n");
    assert!(wait_until(
        Duration::from_secs(5),
        Duration::from_millis(50),
        || pane_read_recent_text(&api_socket, &pane_id).contains("SURVIVED_DETACH")
    ));

    // Drain any shell projection updates.
    drain_messages(&mut stream);

    // Detach the client via explicit Detach message.
    send_detach(&mut stream).expect("send detach");

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist after detach"
    );

    // Verify server is still alive after detach.
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should persist after detach: {response}"
    );

    assert!(
        wait_for_disconnect(&mut stream, Duration::from_secs(2)).expect("wait for detach"),
        "detached client connection should close"
    );

    // Reattach — verify we can connect and receive a frame.
    let mut stream_b = UnixStream::connect(&client_socket).expect("should reattach");
    let (version, error) = client_shell_handshake(&mut stream_b, CURRENT_PROTOCOL, 80, 24)
        .expect("reattach handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Verify the reattached client receives a frame.
    support::wait_for_client_shell_bootstrap(&mut stream_b, Duration::from_secs(5))
        .expect("client shell bootstrap");

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn server_persists_after_client_connection_drop() {
    // Server continues running after a client
    // disconnects (not just detach — also connection drop).
    // Verify that after a client connection is abruptly closed (not via Detach),
    // the server continues running and can accept new connections.
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    // Connect and handshake.
    let mut stream = UnixStream::connect(&client_socket).expect("should connect");
    let (version, error) = client_shell_handshake(&mut stream, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Drain initial frames.
    drain_messages(&mut stream);

    // Drop the connection abruptly (simulating client crash).
    drop(stream);

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist after client connection drop"
    );

    // Verify server is still alive.
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should persist after client connection drop: {response}"
    );

    // Reattach — verify we can connect and handshake again.
    let mut stream_b = UnixStream::connect(&client_socket).expect("should reattach");
    let (version, error) = client_shell_handshake(&mut stream_b, CURRENT_PROTOCOL, 80, 24)
        .expect("reattach handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "reattach should succeed: {:?}", error);

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn pane_created_without_client_uses_configured_headless_size() {
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server_with_config(
        &config_home,
        &runtime_dir,
        &api_socket,
        &client_socket,
        CUSTOM_HEADLESS_SIZE_CONFIG,
    );
    wait_for_socket(&api_socket, Duration::from_secs(10));

    let create = workspace_create(&api_socket, "headless-size");
    let pane_id = create["result"]["root_pane"]["pane_id"]
        .as_str()
        .expect("root pane id")
        .to_string();

    // A second request cannot run until the full render triggered by workspace
    // creation has applied the virtual headless geometry.
    assert!(ping_socket(&api_socket).contains("pong"));
    let size = read_pane_tty_size_after_marker(
        &api_socket,
        &pane_id,
        "HEADLESS_SIZE",
        Duration::from_secs(5),
    );

    assert_eq!(size, (41, 132));

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn pane_created_after_detach_uses_configured_headless_size() {
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server_with_config(
        &config_home,
        &runtime_dir,
        &api_socket,
        &client_socket,
        CUSTOM_HEADLESS_SIZE_CONFIG,
    );
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    let mut stream = UnixStream::connect(&client_socket).expect("client should connect");
    let (version, error) = client_shell_handshake(&mut stream, CURRENT_PROTOCOL, 160, 50)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{error:?}");
    support::wait_for_client_shell_bootstrap(&mut stream, Duration::from_secs(5))
        .expect("client shell bootstrap");

    let first = workspace_create(&api_socket, "attached-size");
    let first_pane_id = first["result"]["root_pane"]["pane_id"]
        .as_str()
        .expect("first root pane id")
        .to_string();
    let attached_size = read_pane_tty_size_after_marker(
        &api_socket,
        &first_pane_id,
        "ATTACHED_SIZE",
        Duration::from_secs(5),
    );
    assert_eq!(attached_size, (50, 160));

    send_detach(&mut stream).expect("send detach");
    assert!(
        wait_for_disconnect(&mut stream, Duration::from_secs(2)).expect("wait for detach"),
        "detached client connection should close"
    );
    drop(stream);

    let second = workspace_create(&api_socket, "headless-size");
    let second_pane_id = second["result"]["root_pane"]["pane_id"]
        .as_str()
        .expect("second root pane id")
        .to_string();
    let headless_size = read_pane_tty_size_after_marker(
        &api_socket,
        &second_pane_id,
        "HEADLESS_SIZE_AFTER_DETACH",
        Duration::from_secs(5),
    );
    let preserved_size = read_pane_tty_size_after_marker(
        &api_socket,
        &first_pane_id,
        "PRESERVED_SIZE_AFTER_DETACH",
        Duration::from_secs(5),
    );

    assert_eq!(headless_size, (41, 132));
    assert_eq!(preserved_size, attached_size);

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn detached_output_preserves_last_attached_pty_size() {
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    let mut stream = UnixStream::connect(&client_socket).expect("client should connect");
    let (version, error) = client_shell_handshake(&mut stream, CURRENT_PROTOCOL, 120, 40)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);
    drain_messages(&mut stream);

    let create = workspace_create(&api_socket, "detached-size");
    let pane_id = create["result"]["root_pane"]["pane_id"]
        .as_str()
        .expect("root pane id")
        .to_string();

    let before = read_pane_tty_size_after_marker(
        &api_socket,
        &pane_id,
        "SIZE_BEFORE_DETACH",
        Duration::from_secs(5),
    );

    send_detach(&mut stream).expect("send detach");
    drop(stream);

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist after detach"
    );

    let while_detached = read_pane_tty_size_after_marker(
        &api_socket,
        &pane_id,
        "SIZE_WHILE_DETACHED",
        Duration::from_secs(5),
    );

    assert_eq!(
        while_detached, before,
        "detached renders should not resize live pane PTYs to a fallback size"
    );

    cleanup_spawned_herdr(spawned, base);
}

#[test]
fn output_accumulated_while_detached_visible_on_reattach() {
    // Output produced while detached is visible in the
    // reattached client's scrollback.
    //
    // Simplified flow:
    // 1. Start server, attach client A
    // 2. Detach client A (without sending any special input)
    // 3. Use API to send text to a pane while detached
    // 4. Reattach as client B
    // 5. Verify client B receives a frame
    // 6. Verify the pane content via API includes the text sent while detached
    let _lock = test_lock();
    let base = unique_test_dir();
    let config_home = base.join("config");
    let runtime_dir = base.join("runtime");
    let api_socket = runtime_dir.join("herdr.sock");
    let client_socket = runtime_dir.join("herdr-client.sock");

    let spawned = spawn_server(&config_home, &runtime_dir, &api_socket, &client_socket);
    wait_for_socket(&api_socket, Duration::from_secs(10));
    wait_for_socket(&client_socket, Duration::from_secs(10));

    // Connect and handshake client A.
    let mut stream_a = UnixStream::connect(&client_socket).expect("client A should connect");
    let (version, error) = client_shell_handshake(&mut stream_a, CURRENT_PROTOCOL, 80, 24)
        .expect("handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Detach client A immediately.
    send_detach(&mut stream_a).expect("send detach");

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            ping_socket(&api_socket).contains("pong")
        }),
        "server should persist"
    );

    // Verify server alive.
    let response = ping_socket(&api_socket);
    assert!(
        response.contains("pong"),
        "server should persist: {response}"
    );

    // Use API to send text to a pane while no client is attached.
    // First create a workspace and find its pane.
    let ws_create_response = workspace_create(&api_socket, "scrollback-test");
    assert_eq!(ws_create_response["result"]["type"], "workspace_created");

    // Find the workspace and pane IDs.
    let ws_response = workspace_list(&api_socket);
    let ws_id = workspace_id_by_label(&ws_response, "scrollback-test");

    // Get pane list for this workspace.
    let pane_response = pane_list(&api_socket, &ws_id);
    let pane_id = first_pane_id(&pane_response);

    // Send text to the pane via API while detached.
    let mut send_stream = UnixStream::connect(&api_socket).expect("connect to API");
    let send_request = format!(
        r#"{{"id":"4","method":"pane.send_text","params":{{"pane_id":"{pane_id}","text":"echo DURING_DETACH\n"}}}}"#
    );
    writeln!(send_stream, "{}", send_request).unwrap();
    let mut send_reader = BufReader::new(send_stream);
    let mut send_response = String::new();
    send_reader.read_line(&mut send_response).unwrap();

    assert!(
        wait_until(Duration::from_secs(2), Duration::from_millis(25), || {
            let read_response = pane_read_recent(&api_socket, &pane_id);
            read_response["result"]["read"]["text"]
                .as_str()
                .unwrap_or_default()
                .contains("DURING_DETACH")
        }),
        "pane should contain output produced while detached before reattach"
    );

    // --- Client B (reattach) ---
    let mut stream_b = UnixStream::connect(&client_socket).expect("client B should connect");
    let (version, error) = client_shell_handshake(&mut stream_b, CURRENT_PROTOCOL, 80, 24)
        .expect("reattach handshake should succeed");
    assert_eq!(version, CURRENT_PROTOCOL);
    assert!(error.is_none(), "{:?}", error);

    // Client B should receive a frame with the current state.
    support::wait_for_client_shell_bootstrap(&mut stream_b, Duration::from_secs(5))
        .expect("client shell bootstrap");

    cleanup_spawned_herdr(spawned, base);
}