Keep live TUI output raw under retransmit pressure

tests/integration_smoke.rs

@@ -112,6 +112,21 @@ fn write_server_config_with_output_interval(
     config
 }
 
+fn write_server_config_with_retransmit_window(
+    dir: &tempfile::TempDir,
+    port: u16,
+    retransmit_window: u64,
+) -> std::path::PathBuf {
+    let config = write_server_config(dir, port);
+    let mut raw = fs::read_to_string(&config).unwrap();
+    raw = raw.replace(
+        "retransmit_window = 256\n",
+        &format!("retransmit_window = {retransmit_window}\n"),
+    );
+    fs::write(&config, raw).unwrap();
+    config
+}
+
 fn start_server(dir: &tempfile::TempDir, config: &std::path::Path) -> Child {
     let server = env!("CARGO_BIN_EXE_dosh-server");
     let child = Command::new(server)
@@ -1694,6 +1709,69 @@ fn tui_graph_glyphs_survive_fast_repaints_without_snapshot_substitution() {
     );
 }
 
+#[test]
+fn btop_style_graph_output_stays_raw_when_retransmit_history_overflows() {
+    let dir = tempfile::tempdir().unwrap();
+    let port = free_udp_port();
+    let config = write_server_config_with_retransmit_window(&dir, port, 3);
+    let mut server = start_server(&dir, &config);
+    let (socket, bootstrap, ok) = direct_attach(&config, port, "read-write");
+
+    let graph = "DOSH_BTOP_NET ⠀⠁⠃⠇⡇⣇⣧⣷⣿";
+    let input = Input {
+        bytes: format!(
+            "stty -echo; \
+             printf '\\033[?1049h\\033[?2026h\\033[?25l'; \
+             for i in 1 2 3 4 5 6 7 8 9 10; do \
+               printf '\\033[6;4H\\033[38;2;80;220;140m{} %s\\033[0m' \"$i\"; \
+             done; \
+             printf '\\033[?25h\\033[?2026l\\033[?1049l'\n",
+            graph
+        )
+        .into_bytes(),
+    };
+    send_encrypted(
+        &socket,
+        port,
+        PacketKind::Input,
+        ok.client_id,
+        2,
+        0,
+        &bootstrap.session_key,
+        &protocol::to_body(&input).unwrap(),
+    );
+
+    let mut text = String::new();
+    let mut snapshots = 0usize;
+    let deadline = std::time::Instant::now() + Duration::from_secs(3);
+    while std::time::Instant::now() < deadline
+        && !(text.matches("DOSH_BTOP_NET").count() >= 10 && text.contains("\x1b[?2026l"))
+    {
+        if let Some((_header, frame)) = recv_frame(&socket, &bootstrap.session_key) {
+            if frame.snapshot {
+                snapshots += 1;
+            }
+            text.push_str(&String::from_utf8_lossy(&frame.bytes));
+        }
+    }
+
+    let _ = server.kill();
+    let _ = server.wait();
+
+    assert_eq!(
+        snapshots, 0,
+        "live btop-style graph output must not be replaced by snapshots; got {snapshots}"
+    );
+    assert!(
+        text.matches("DOSH_BTOP_NET").count() >= 10
+            && text.contains("⣿")
+            && text.contains("\x1b[38;2;80;220;140m")
+            && text.contains("\x1b[?2026h")
+            && text.contains("\x1b[?2026l"),
+        "expected raw btop-style graph output to survive under retransmit pressure, got {text:?}"
+    );
+}
+
 #[test]
 fn large_tui_paint_is_delivered_in_mtu_safe_frames() {
     let dir = tempfile::tempdir().unwrap();