fix(ui): keep the important text visible on narrow terminals

Three panes painted two independent pieces of text onto one row with nothing
reserving space between them, so below roughly 105 columns the right-hand piece
was simply drawn over the tail of the left one:

  socktop — host: cachyos-gaming | 🔒✗ TLS | (a: about⏱ 500ms metrics | 2000ms

The width arithmetic used str::len(), a byte count, so the emoji in these strings
overstated their width and left orphaned glyphs at the right edge as well. The
process table had the same problem in a different form: it handed the layout
solver a fixed, over-constrained column set, so a narrow pane crushed the
percentage-sized Name column to nothing while fixed-width PID and Mem % kept
their full width — losing the one field that identifies a process.

Add ui::fit (measure in terminal columns, truncate on character boundaries, pick
the richest wording that fits) and give each pane a priority ladder:

- Header: drop the key hints, then the TLS/token badges, then the
  "socktop — host:" prefix, then the metrics/procs words, and only then shorten
  the hostname. Hostname and intervals are what survive longest.
- CPU pane: drop the "CPU Temp:" label, then the now:/avg: labels, then the
  average, then the temperature's decimal, and the temperature itself last — a
  thermal warning outranks a second decimal place.
- Process table: Name is unconditional; CPU %, then Mem, then PID, then Mem %
  are added as the pane widens, so Mem % is the first to go and Name the last.

Also fixes sort-header clicks, which resolved against a Layout that omitted the
column spacing the Table renders with, so a click landed off by up to four
columns. Covered by a test that clicks each label where it is actually drawn.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Cargo.lock

@@ -2426,6 +2426,7 @@ dependencies = [
  "sysinfo",
  "tempfile",
  "tokio",
+ "unicode-width",
  "url",
 ]
 

Cargo.toml

@@ -26,6 +26,7 @@ sysinfo = "0.37"
 # CLI UI
 ratatui = "0.30"
 crossterm = "0.29"
+unicode-width = "0.2"
 
 # web server (remote-agent)
 axum = { version = "0.7", features = ["ws"] }

README.md

@@ -31,6 +31,8 @@ socktop is a remote system monitor with a rich TUI, inspired by top/btop, talkin
   - Only top-level processes listed (threads hidden) — matches btop/top
 - Optional GPU metrics (can be disabled)
 - Optional auth token for the agent
+- Compact layout for small windows: automatically drops the panes that no longer fit so
+  the CPU graph and per-core bars stay visible (see [Compact mode](#compact-mode))
 
 ---
 
@@ -213,6 +215,8 @@ socktop --verify-hostname --tls-ca /path/to/cert.pem wss://HOST:8443/ws
 # shorthand:
 socktop -t /path/to/cert.pem wss://HOST:8443/ws
 # Note: providing --tls-ca/-t automatically upgrades ws:// to wss:// if you forget
+# force the small-window layout at any terminal size (normally automatic):
+socktop --compact ws://HOST:3000/ws
 ```
 
 Intervals (client-driven):
@@ -224,6 +228,29 @@ The agent stays idle unless queried. When queried, it collects just what’s nee
 
 ---
 
+## Compact mode
+
+In a short terminal the fixed layout runs out of rows and the CPU graph and per-core bars
+are the first things to collapse — exactly the panes you are most likely watching. Once
+the window is too short for the Disks pane to show even one disk, socktop switches to a
+compact layout:
+
+- **Disks is dropped.** It is the pane that degrades worst when partially drawn.
+- **Memory and Swap move side by side** into the row Disks vacated.
+- **GPU shrinks to a single line** — utilisation and VRAM only, no device name. On a host
+  with no GPU the pane disappears entirely.
+- **Everything reclaimed goes to the CPU graph and per-core bars**, which stay usable well
+  below the size where they used to vanish.
+
+The switch is automatic and needs no configuration. Pass `--compact` to pin the compact
+layout at any window size:
+
+```bash
+socktop --compact ws://HOST:3000/ws
+```
+
+---
+
 ## Connection Profiles (Named)
 
 You can save frequently used connection settings (URL + optional TLS CA path) under a short name and reuse them later.

socktop/Cargo.toml

@@ -20,6 +20,7 @@ serde_json = { workspace = true }
 url = { workspace = true }
 ratatui = { workspace = true }
 crossterm = { workspace = true }
+unicode-width = { workspace = true }
 anyhow = { workspace = true }
 dirs-next = { workspace = true }
 sysinfo = { workspace = true }

socktop/src/app.rs

@@ -15,7 +15,7 @@ use ratatui::{
     //style::Color, // + add Color
     Terminal,
     backend::CrosstermBackend,
-    layout::{Constraint, Direction, Rect},
+    layout::Rect,
 };
 use tokio::time::{sleep, timeout};
 
@@ -27,6 +27,7 @@ use crate::ui::cpu::{
     per_core_content_area, per_core_handle_key, per_core_handle_mouse,
     per_core_handle_scrollbar_mouse,
 };
+use crate::ui::layout::{AppLayout, compute as compute_layout};
 use crate::ui::modal::{ModalAction, ModalManager, ModalType};
 use crate::ui::processes::{
     ProcSortBy, ProcessKeyParams, processes_handle_key_with_selection,
@@ -34,8 +35,8 @@ use crate::ui::processes::{
 };
 use crate::ui::{
     disks::draw_disks,
-    gpu::draw_gpu,
-    header::{build_header_intervals, build_header_title, draw_header},
+    gpu::{draw_gpu, draw_gpu_compact},
+    header::{HeaderState, build_header, draw_header},
     mem::draw_mem,
     net::draw_net_spark,
     swap::draw_swap,
@@ -145,12 +146,15 @@ pub struct App {
     pub is_tls: bool,
     pub has_token: bool,
 
+    // --compact: pin the compact layout regardless of window size. Without it the
+    // layout switches on its own once the window is too short for the Disks pane.
+    force_compact: bool,
+
     // Cached title strings — only rebuilt when source values change so the
     // diff renderer can suppress redraws on idle frames.
     header_title: String,
-    header_title_key: (String, bool, bool),
     header_intervals_text: String,
-    header_intervals_key: (u128, u128),
+    header_key: (String, bool, bool, u128, u128, u16),
     net_dl_title: String,
     net_dl_key: (u64, u64),
     net_ul_title: String,
@@ -229,10 +233,10 @@ impl App {
             verify_hostname: false,
             is_tls: false,
             has_token: false,
+            force_compact: false,
             header_title: String::new(),
-            header_title_key: (String::new(), false, false),
             header_intervals_text: String::new(),
-            header_intervals_key: (u128::MAX, u128::MAX),
+            header_key: (String::new(), false, false, u128::MAX, u128::MAX, u16::MAX),
             net_dl_title: String::new(),
             net_dl_key: (u64::MAX, u64::MAX),
             net_ul_title: String::new(),
@@ -247,6 +251,23 @@ impl App {
         }
     }
 
+    /// Pins the compact layout at any window size (`--compact`).
+    pub fn with_compact(mut self, force_compact: bool) -> Self {
+        self.force_compact = force_compact;
+        self
+    }
+
+    /// Pane rects for the current frame. The draw path and the mouse/key hit-testing
+    /// paths all go through here so they cannot disagree about where a pane is.
+    fn layout(&self, area: Rect) -> AppLayout {
+        let has_gpu = self
+            .last_metrics
+            .as_ref()
+            .and_then(|m| m.gpus.as_ref())
+            .is_some_and(|g| !g.is_empty());
+        compute_layout(area, self.force_compact, has_gpu)
+    }
+
     pub fn with_intervals(mut self, metrics_ms: Option<u64>, procs_ms: Option<u64>) -> Self {
         metrics_ms.inspect(|&m| {
             self.metrics_interval = Duration::from_millis(m.max(MIN_METRICS_INTERVAL_MS));
@@ -803,21 +824,8 @@ impl App {
                         // Per-core scroll via keys (Up/Down/PageUp/PageDown/Home/End)
                         let sz = terminal.size()?;
                         let area = Rect::new(0, 0, sz.width, sz.height);
-                        let rows = ratatui::layout::Layout::default()
-                            .direction(Direction::Vertical)
-                            .constraints([
-                                Constraint::Length(1),
-                                Constraint::Ratio(1, 3),
-                                Constraint::Length(3),
-                                Constraint::Length(3),
-                                Constraint::Min(10),
-                            ])
-                            .split(area);
-                        let top = ratatui::layout::Layout::default()
-                            .direction(Direction::Horizontal)
-                            .constraints([Constraint::Percentage(66), Constraint::Percentage(34)])
-                            .split(rows[1]);
-                        let content = per_core_content_area(top[1]);
+                        let layout = self.layout(area);
+                        let content = per_core_content_area(layout.per_core);
 
                         // Refresh the filtered+sorted index cache once before we
                         // borrow individual fields of `self`.
@@ -915,23 +923,10 @@ impl App {
                         // Layout to get areas
                         let sz = terminal.size()?;
                         let area = Rect::new(0, 0, sz.width, sz.height);
-                        let rows = ratatui::layout::Layout::default()
-                            .direction(Direction::Vertical)
-                            .constraints([
-                                Constraint::Length(1),
-                                Constraint::Ratio(1, 3),
-                                Constraint::Length(3),
-                                Constraint::Length(3),
-                                Constraint::Min(10),
-                            ])
-                            .split(area);
-                        let top = ratatui::layout::Layout::default()
-                            .direction(Direction::Horizontal)
-                            .constraints([Constraint::Percentage(66), Constraint::Percentage(34)])
-                            .split(rows[1]);
+                        let layout = self.layout(area);
 
                         // Content wheel scrolling
-                        let content = per_core_content_area(top[1]);
+                        let content = per_core_content_area(layout.per_core);
                         per_core_handle_mouse(
                             &mut self.per_core_scroll,
                             m,
@@ -949,7 +944,7 @@ impl App {
                             &mut self.per_core_scroll,
                             &mut self.per_core_drag,
                             m,
-                            top[1],
+                            layout.per_core,
                             total_rows,
                         );
 
@@ -1278,106 +1273,70 @@ impl App {
 
     pub fn draw(&mut self, f: &mut ratatui::Frame<'_>) {
         let area = f.area();
-
-        // Root rows: header, top (cpu avg + per-core), memory, swap, bottom
-        let rows = ratatui::layout::Layout::default()
-            .direction(Direction::Vertical)
-            .constraints([
-                Constraint::Length(1),   // header
-                Constraint::Ratio(1, 3), // top row
-                Constraint::Length(3),   // memory (left) + GPU (right, part 1)
-                Constraint::Length(3),   // swap (left)   + GPU (right, part 2)
-                Constraint::Min(10),     // bottom: disks + net (left), top procs (right)
-            ])
-            .split(area);
+        let l = self.layout(area);
 
         // Header — refresh cached strings only when their inputs change so the
-        // ratatui diff renderer can suppress repaints on idle frames.
+        // ratatui diff renderer can suppress repaints on idle frames. The wording now
+        // depends on the row width too, so that is part of the key.
         {
             let hostname = self.last_metrics.as_ref().map(|mm| mm.hostname.as_str());
+            let state = HeaderState {
+                hostname,
+                is_tls: self.is_tls,
+                has_token: self.has_token,
+                metrics_ms: self.metrics_interval.as_millis(),
+                procs_ms: self.procs_interval.as_millis(),
+            };
             let key = (
                 hostname.unwrap_or("").to_string(),
                 self.is_tls,
                 self.has_token,
+                state.metrics_ms,
+                state.procs_ms,
+                l.header.width,
             );
-            if self.header_title_key != key {
-                self.header_title = build_header_title(hostname, self.is_tls, self.has_token);
-                self.header_title_key = key;
-            }
-
-            let intervals_key = (
-                self.metrics_interval.as_millis(),
-                self.procs_interval.as_millis(),
-            );
-            if self.header_intervals_key != intervals_key {
-                self.header_intervals_text =
-                    build_header_intervals(intervals_key.0, intervals_key.1);
-                self.header_intervals_key = intervals_key;
+            if self.header_key != key {
+                let (title, intervals) = build_header(state, l.header.width);
+                self.header_title = title;
+                self.header_intervals_text = intervals;
+                self.header_key = key;
             }
         }
-        draw_header(f, rows[0], &self.header_title, &self.header_intervals_text);
-
-        // Top row: left CPU avg, right Per-core (full top-right)
-        let top_lr = ratatui::layout::Layout::default()
-            .direction(Direction::Horizontal)
-            .constraints([Constraint::Percentage(66), Constraint::Percentage(34)])
-            .split(rows[1]);
+        draw_header(f, l.header, &self.header_title, &self.header_intervals_text);
 
         draw_cpu_avg_graph(
             f,
-            top_lr[0],
+            l.cpu,
             &mut self.cpu_hist,
             self.cpu_hist_sum,
             self.last_metrics.as_ref(),
         );
         draw_per_core_bars(
             f,
-            top_lr[1],
+            l.per_core,
             self.last_metrics.as_ref(),
             &mut self.per_core_hist,
             self.per_core_scroll,
         );
 
-        // Memory + Swap rows split into left/right columns
-        let mem_lr = ratatui::layout::Layout::default()
-            .direction(Direction::Horizontal)
-            .constraints([Constraint::Percentage(66), Constraint::Percentage(34)])
-            .split(rows[2]);
-        let swap_lr = ratatui::layout::Layout::default()
-            .direction(Direction::Horizontal)
-            .constraints([Constraint::Percentage(66), Constraint::Percentage(34)])
-            .split(rows[3]);
+        // Memory + Swap: stacked vertically in the normal layout, side by side in the
+        // row Disks vacates in compact mode.
+        draw_mem(f, l.mem, self.last_metrics.as_ref());
+        draw_swap(f, l.swap, self.last_metrics.as_ref());
 
-        // Left: Memory + Swap
-        draw_mem(f, mem_lr[0], self.last_metrics.as_ref());
-        draw_swap(f, swap_lr[0], self.last_metrics.as_ref());
+        // GPU: a panel beside Memory/Swap normally, a single full-width line in compact
+        // mode, and absent entirely when the host reports no GPU while compact.
+        if let Some(gpu_area) = l.gpu {
+            if l.mode.is_compact() {
+                draw_gpu_compact(f, gpu_area, self.last_metrics.as_ref());
+            } else {
+                draw_gpu(f, gpu_area, self.last_metrics.as_ref());
+            }
+        }
 
-        // Right: GPU spans the same vertical space as Memory + Swap
-        let gpu_area = ratatui::layout::Rect {
-            x: mem_lr[1].x,
-            y: mem_lr[1].y,
-            width: mem_lr[1].width,
-            height: mem_lr[1].height + swap_lr[1].height,
-        };
-        draw_gpu(f, gpu_area, self.last_metrics.as_ref());
-
-        // Bottom area: left = Disks + Network, right = Top Processes
-        let bottom_lr = ratatui::layout::Layout::default()
-            .direction(Direction::Horizontal)
-            .constraints([Constraint::Percentage(60), Constraint::Percentage(40)])
-            .split(rows[4]);
-
-        // Left bottom: Disks + Net stacked (make net panes slightly taller)
-        let left_stack = ratatui::layout::Layout::default()
-            .direction(Direction::Vertical)
-            .constraints([
-                Constraint::Min(4),    // Disks shrink slightly
-                Constraint::Length(5), // Download taller
-                Constraint::Length(5), // Upload taller
-            ])
-            .split(bottom_lr[0]);
-
-        draw_disks(f, left_stack[0], self.last_metrics.as_ref());
+        if let Some(disks_area) = l.disks {
+            draw_disks(f, disks_area, self.last_metrics.as_ref());
+        }
 
         // Net titles only change when the throughput or peak changes.
         let rx_now = self.rx_hist.back().copied().unwrap_or(0);
@@ -1388,7 +1347,7 @@ impl App {
         }
         draw_net_spark(
             f,
-            left_stack[1],
+            l.download,
             &self.net_dl_title,
             &mut self.rx_hist,
             ratatui::style::Color::Green,
@@ -1402,14 +1361,14 @@ impl App {
         }
         draw_net_spark(
             f,
-            left_stack[2],
+            l.upload,
             &self.net_ul_title,
             &mut self.tx_hist,
             ratatui::style::Color::Blue,
         );
 
         // Right bottom: Top Processes fills the column
-        let procs_area = bottom_lr[1];
+        let procs_area = l.procs;
         // Cache for input handlers
         self.last_procs_area = Some(procs_area);
         // Refresh the filter cache before partial borrows of self.

socktop/src/main.rs

@@ -22,6 +22,7 @@ pub(crate) struct ParsedArgs {
     metrics_interval_ms: Option<u64>,
     processes_interval_ms: Option<u64>,
     verify_hostname: bool,
+    compact: bool,
 }
 
 pub(crate) fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<ParsedArgs, String> {
@@ -36,11 +37,12 @@ pub(crate) fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<Pars
     let mut metrics_interval_ms: Option<u64> = None;
     let mut processes_interval_ms: Option<u64> = None;
     let mut verify_hostname = false;
+    let mut compact = false;
     while let Some(arg) = it.next() {
         match arg.as_str() {
             "-h" | "--help" => {
                 return Err(format!(
-                    "Usage: {prog} [--tls-ca CERT_PEM|-t CERT_PEM] [--verify-hostname] [--profile NAME|-P NAME] [--save] [--demo] [--metrics-interval-ms N] [--processes-interval-ms N] [ws://HOST:PORT/ws]\n"
+                    "Usage: {prog} [--tls-ca CERT_PEM|-t CERT_PEM] [--verify-hostname] [--profile NAME|-P NAME] [--save] [--demo] [--compact] [--metrics-interval-ms N] [--processes-interval-ms N] [ws://HOST:PORT/ws]\n"
                 ));
             }
             "--tls-ca" | "-t" => {
@@ -61,6 +63,11 @@ pub(crate) fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<Pars
             "--demo" => {
                 demo = true;
             }
+            "--compact" => {
+                // Force the small-window layout at any terminal size. Without it the
+                // layout switches on its own once the window gets too short.
+                compact = true;
+            }
             "--dry-run" => {
                 // intentionally undocumented
                 dry_run = true;
@@ -100,7 +107,7 @@ pub(crate) fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<Pars
                     url = Some(arg);
                 } else {
                     return Err(format!(
-                        "Unexpected argument. Usage: {prog} [--tls-ca CERT_PEM|-t CERT_PEM] [--verify-hostname] [--profile NAME|-P NAME] [--save] [--demo] [ws://HOST:PORT/ws]"
+                        "Unexpected argument. Usage: {prog} [--tls-ca CERT_PEM|-t CERT_PEM] [--verify-hostname] [--profile NAME|-P NAME] [--save] [--demo] [--compact] [ws://HOST:PORT/ws]"
                     ));
                 }
             }
@@ -116,6 +123,7 @@ pub(crate) fn parse_args<I: IntoIterator<Item = String>>(args: I) -> Result<Pars
         metrics_interval_ms,
         processes_interval_ms,
         verify_hostname,
+        compact,
     })
 }
 
@@ -136,7 +144,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     }
 
     if parsed.demo || matches!(parsed.profile.as_deref(), Some("demo")) {
-        return run_demo_mode(parsed.tls_ca.as_deref()).await;
+        return run_demo_mode(parsed.tls_ca.as_deref(), parsed.compact).await;
     }
 
     let profiles_file = load_profiles();
@@ -241,7 +249,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                     if (1..=names.len()).contains(&idx) {
                         let name = &names[idx - 1];
                         if name == "demo" {
-                            return run_demo_mode(parsed.tls_ca.as_deref()).await;
+                            return run_demo_mode(parsed.tls_ca.as_deref(), parsed.compact).await;
                         }
                         if let Some(entry) = profiles_mut.profiles.get(name) {
                             (
@@ -301,7 +309,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
                 );
                 eprintln!("If you don't have an agent running, you can try the demo mode.");
                 if prompt_yes_no("Would you like to start the demo mode now? [Y/n]: ") {
-                    return run_demo_mode(parsed.tls_ca.as_deref()).await;
+                    return run_demo_mode(parsed.tls_ca.as_deref(), parsed.compact).await;
                 } else {
                     eprintln!("Aborting. You can run 'socktop --help' for usage information.");
                     return Ok(());
@@ -315,7 +323,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     let has_token = url.contains("token=");
     let mut app = App::new()
         .with_intervals(metrics_interval_ms, processes_interval_ms)
-        .with_status(is_tls, has_token);
+        .with_status(is_tls, has_token)
+        .with_compact(parsed.compact);
     if parsed.dry_run {
         return Ok(());
     }
@@ -379,11 +388,23 @@ fn gather_intervals(
 }
 
 // Demo mode implementation
-async fn run_demo_mode(_tls_ca: Option<&str>) -> Result<(), Box<dyn std::error::Error>> {
+async fn run_demo_mode(
+    _tls_ca: Option<&str>,
+    compact: bool,
+) -> Result<(), Box<dyn std::error::Error>> {
     let port = 3231;
     let url = format!("ws://127.0.0.1:{port}/ws");
-    let child = spawn_demo_agent(port)?;
-    let mut app = App::new();
+    let child = match spawn_demo_agent(port) {
+        Ok(child) => child,
+        // The agent ships as its own binary, so a missing one is a setup problem,
+        // not a crash: tell the user how to fix it instead of dumping an io error.
+        Err(e @ DemoAgentError::NotFound(_)) => {
+            eprintln!("{e}");
+            return Ok(());
+        }
+        Err(e) => return Err(e.into()),
+    };
+    let mut app = App::new().with_compact(compact);
     // Demo mode connects to localhost, so disable hostname verification
     tokio::select! { res=app.run(&url,None,false)=>{ drop(child); res } _=tokio::signal::ctrl_c()=>{ drop(child); Ok(()) } }
 }
@@ -399,9 +420,50 @@ impl Drop for DemoGuard {
         eprintln!("Stopped demo agent on port {}", self.port);
     }
 }
-fn spawn_demo_agent(port: u16) -> Result<DemoGuard, Box<dyn std::error::Error>> {
+#[derive(Debug)]
+enum DemoAgentError {
+    /// The socktop_agent executable could not be located.
+    NotFound(std::path::PathBuf),
+    Io(std::io::Error),
+}
+
+impl std::fmt::Display for DemoAgentError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::NotFound(candidate) => write!(
+                f,
+                "Could not start demo mode: '{}' was not found{}.\n\
+                 \n\
+                 Demo mode runs a local agent, which is shipped as a separate binary\n\
+                 and is not installed alongside the socktop TUI. Install it with:\n\
+                 \n    cargo install socktop_agent\n\n\
+                 then run socktop again. See {} for other install options.",
+                candidate.display(),
+                // A bare file name means find_agent_executable() fell back to a PATH lookup.
+                if candidate.parent().is_none_or(|p| p.as_os_str().is_empty()) {
+                    " on your PATH"
+                } else {
+                    ""
+                },
+                env!("CARGO_PKG_HOMEPAGE"),
+            ),
+            Self::Io(e) => write!(f, "Could not start demo mode: {e}"),
+        }
+    }
+}
+
+impl std::error::Error for DemoAgentError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            Self::NotFound(_) => None,
+            Self::Io(e) => Some(e),
+        }
+    }
+}
+
+fn spawn_demo_agent(port: u16) -> Result<DemoGuard, DemoAgentError> {
     let candidate = find_agent_executable();
-    let mut cmd = std::process::Command::new(candidate);
+    let mut cmd = std::process::Command::new(&candidate);
     cmd.arg("--port").arg(port.to_string());
     cmd.env("SOCKTOP_ENABLE_SSL", "0");
 
@@ -409,7 +471,10 @@ fn spawn_demo_agent(port: u16) -> Result<DemoGuard, Box<dyn std::error::Error>>
     //cmd.env("SOCKTOP_AGENT_GPU", "0");
     //cmd.env("SOCKTOP_AGENT_TEMP", "0");
 
-    let child = cmd.spawn()?;
+    let child = cmd.spawn().map_err(|e| match e.kind() {
+        std::io::ErrorKind::NotFound => DemoAgentError::NotFound(candidate),
+        _ => DemoAgentError::Io(e),
+    })?;
     std::thread::sleep(std::time::Duration::from_millis(300));
     Ok(DemoGuard {
         port,

socktop/src/ui/cpu.rs

@@ -14,6 +14,10 @@ use ratatui::{
 
 use crate::history::PerCoreHistory;
 use crate::types::Metrics;
+use crate::ui::fit::{cols, pick_pair};
+
+/// Columns kept clear between the CPU title and the temperature readout.
+const TITLE_GAP: u16 = 2;
 
 /// State for dragging the scrollbar thumb
 #[derive(Clone, Copy, Debug, Default)]
@@ -248,29 +252,12 @@ pub fn draw_cpu_avg_graph(
         hist_sum as f64 / hist.len() as f64
     };
 
-    let title = if let Some(mm) = m {
-        format!("CPU (now: {:>5.1}% | avg: {:>5.1}%)", mm.cpu_total, avg_cpu)
-    } else {
-        "CPU avg".into()
-    };
-
-    // Build the top-right info (CPU temp and polling intervals)
-    let top_right_info = if let Some(mm) = m {
-        mm.cpu_temp_c
-            .map(|t| {
-                let icon = if t < 50.0 {
-                    "😎"
-                } else if t < 85.0 {
-                    "⚠️"
-                } else {
-                    "🔥"
-                };
-                format!("CPU Temp: {t:.1}°C {icon}")
-            })
-            .unwrap_or_else(|| "CPU Temp: N/A".into())
-    } else {
-        String::new()
-    };
+    let (title, top_right_info) = cpu_title_for_width(
+        m.map(|mm| mm.cpu_total),
+        avg_cpu,
+        m.and_then(|mm| mm.cpu_temp_c),
+        area.width,
+    );
 
     // Hand a slice directly to Sparkline. `make_contiguous` is amortized cheap
     // for our usage pattern (cap'd 600-element ring updated at 2 Hz) and lets
@@ -286,12 +273,14 @@ pub fn draw_cpu_avg_graph(
         .style(Style::default().fg(Color::Cyan));
     f.render_widget(spark, area);
 
-    // Render the top-right info as text overlay in the top-right corner
+    // Temperature overlays the top border, right-aligned inside the corner. The title
+    // above is sized so the two cannot collide.
     if !top_right_info.is_empty() {
+        let w = cols(&top_right_info);
         let info_area = Rect {
-            x: area.x + area.width.saturating_sub(top_right_info.len() as u16 + 2),
+            x: area.x + area.width.saturating_sub(w + 1),
             y: area.y,
-            width: top_right_info.len() as u16 + 1,
+            width: w,
             height: 1,
         };
         let info_line = Line::from(Span::raw(top_right_info));
@@ -299,6 +288,67 @@ pub fn draw_cpu_avg_graph(
     }
 }
 
+/// Health glyph for a CPU temperature.
+fn temp_icon(t: f32) -> &'static str {
+    if t < 50.0 {
+        "😎"
+    } else if t < 85.0 {
+        "⚠️"
+    } else {
+        "🔥"
+    }
+}
+
+/// Chooses the CPU pane's title and its right-aligned temperature readout for a pane
+/// `width` columns wide.
+///
+/// Both are painted onto the pane's top border, so without a shared budget the
+/// temperature simply overwrites the tail of the title on a narrow pane. Detail is given
+/// up in this order: the `CPU Temp:` label, then the `now:`/`avg:` labels, then the
+/// average reading, then the decimal on the temperature, and only last the temperature
+/// itself — the readings are what the pane is for, but a thermal warning is worth more
+/// than a second decimal place.
+fn cpu_title_for_width(
+    cpu_now: Option<f32>,
+    avg_cpu: f64,
+    temp_c: Option<f32>,
+    width: u16,
+) -> (String, String) {
+    let Some(now) = cpu_now else {
+        return ("CPU avg".into(), String::new());
+    };
+
+    // Two borders, plus a column of breathing room at each end of the title.
+    let budget = width.saturating_sub(4);
+
+    let labelled = format!("CPU (now: {now:>5.1}% | avg: {avg_cpu:>5.1}%)");
+    let bare = format!("CPU ({now:.1}% | {avg_cpu:.1}%)");
+    let now_only = format!("CPU ({now:.1}%)");
+
+    let (temp_labelled, temp_plain, temp_coarse) = match temp_c {
+        Some(t) => {
+            let icon = temp_icon(t);
+            (
+                format!("CPU Temp: {t:.1}°C {icon}"),
+                format!("{t:.1}°C {icon}"),
+                format!("{t:.0}°C {icon}"),
+            )
+        }
+        None => ("CPU Temp: N/A".into(), "N/A".into(), "N/A".into()),
+    };
+
+    let ladder = [
+        (labelled.as_str(), temp_labelled.as_str()),
+        (labelled.as_str(), temp_plain.as_str()),
+        (bare.as_str(), temp_plain.as_str()),
+        (bare.as_str(), temp_coarse.as_str()),
+        (now_only.as_str(), temp_coarse.as_str()),
+        (now_only.as_str(), ""),
+    ];
+    let (title, temp) = pick_pair(budget, TITLE_GAP, &ladder);
+    (title.to_string(), temp.to_string())
+}
+
 /// Draws the per-core CPU bars with sparklines and trends.
 pub fn draw_per_core_bars(
     f: &mut ratatui::Frame<'_>,
@@ -428,6 +478,108 @@ pub fn draw_per_core_bars(
     }
 }
 
+#[cfg(test)]
+mod title_tests {
+    use super::*;
+
+    /// The defect this replaces: the temperature was painted over the title's tail on a
+    /// narrow pane. Whatever the width, the two must fit side by side on the border.
+    #[test]
+    fn title_and_temperature_never_overlap() {
+        for width in 0..=200u16 {
+            let (title, temp) = cpu_title_for_width(Some(3.4), 12.7, Some(43.0), width);
+            let budget = width.saturating_sub(4);
+            if temp.is_empty() {
+                continue;
+            }
+            assert!(
+                cols(&title) + cols(&temp) + TITLE_GAP <= budget,
+                "width {width}: {title:?} + {temp:?} do not fit in {budget} columns"
+            );
+        }
+    }
+
+    /// The current CPU reading is the one thing the pane must always show.
+    #[test]
+    fn the_current_reading_always_survives() {
+        for width in 20..=200u16 {
+            let (title, _) = cpu_title_for_width(Some(3.4), 12.7, Some(43.0), width);
+            assert!(
+                title.contains("3.4"),
+                "width {width}: lost the reading ({title:?})"
+            );
+        }
+    }
+
+    /// The ladder from the design: temp label, then now/avg labels, then the average,
+    /// then the temperature's decimal, then the temperature.
+    #[test]
+    fn detail_is_dropped_in_priority_order() {
+        let at = |w| cpu_title_for_width(Some(0.7), 1.3, Some(43.0), w);
+
+        let (title, temp) = at(80);
+        assert_eq!(title, "CPU (now:   0.7% | avg:   1.3%)");
+        assert_eq!(temp, "CPU Temp: 43.0°C 😎");
+
+        // The "CPU Temp:" label goes first; the readings keep their labels.
+        let (title, temp) = at(50);
+        assert_eq!(title, "CPU (now:   0.7% | avg:   1.3%)");
+        assert_eq!(temp, "43.0°C 😎");
+
+        // Then the now:/avg: labels.
+        let (title, temp) = at(40);
+        assert_eq!(title, "CPU (0.7% | 1.3%)");
+        assert_eq!(temp, "43.0°C 😎");
+
+        // Then the temperature's decimal.
+        let (title, temp) = at(31);
+        assert_eq!(title, "CPU (0.7% | 1.3%)");
+        assert_eq!(temp, "43°C 😎");
+
+        // Then the average reading.
+        let (title, temp) = at(26);
+        assert_eq!(title, "CPU (0.7%)");
+        assert_eq!(temp, "43°C 😎");
+
+        // Last of all, the temperature itself.
+        let (title, temp) = at(15);
+        assert_eq!(title, "CPU (0.7%)");
+        assert_eq!(temp, "");
+    }
+
+    /// A hot CPU has to stay visible as a warning, so the glyph rides along with the
+    /// reading at every tier that shows a temperature at all.
+    #[test]
+    fn the_thermal_glyph_tracks_the_temperature() {
+        for (t, icon) in [(43.0, "😎"), (70.0, "⚠️"), (92.0, "🔥")] {
+            for width in 26..=80u16 {
+                let (_, temp) = cpu_title_for_width(Some(0.7), 1.3, Some(t), width);
+                assert!(
+                    temp.contains(icon),
+                    "width {width} at {t}°C: expected {icon} in {temp:?}"
+                );
+            }
+        }
+    }
+
+    /// An agent that reports no temperature must not leave a stray label behind.
+    #[test]
+    fn a_missing_temperature_degrades_to_nothing() {
+        let (_, temp) = cpu_title_for_width(Some(0.7), 1.3, None, 80);
+        assert_eq!(temp, "CPU Temp: N/A");
+        let (_, temp) = cpu_title_for_width(Some(0.7), 1.3, None, 14);
+        assert_eq!(temp, "");
+    }
+
+    /// Before the first payload arrives there are no readings to show.
+    #[test]
+    fn no_metrics_yet_shows_the_placeholder() {
+        let (title, temp) = cpu_title_for_width(None, 0.0, None, 80);
+        assert_eq!(title, "CPU avg");
+        assert!(temp.is_empty());
+    }
+}
+
 #[cfg(test)]
 mod render_tests {
     use super::*;

socktop/src/ui/fit.rs

@@ -0,0 +1,133 @@
+//! Fitting text to the columns actually available.
+//!
+//! Several panes paint two independent pieces of text onto one row — a left title and a
+//! right-aligned readout. Nothing reserves space for the right piece, so on a narrow
+//! terminal the right one is simply painted over the tail of the left one and the title
+//! is clobbered mid-word. The helpers here let a caller measure in real terminal columns
+//! and pick the richest wording that still fits, so the two never overlap.
+//!
+//! Note that `str::len()` is a byte count and must not be used for this: `⏱` is three
+//! bytes wide but one column, and `🔒` is four bytes but two columns.
+
+use unicode_width::UnicodeWidthStr;
+
+/// Terminal columns `s` occupies, saturating at `u16::MAX`.
+pub fn cols(s: &str) -> u16 {
+    UnicodeWidthStr::width(s).min(u16::MAX as usize) as u16
+}
+
+/// Shortens `s` to at most `max` columns, marking the cut with `…`.
+///
+/// Cuts on character boundaries and accounts for wide characters, so the result never
+/// exceeds `max` columns and never splits a multi-byte character.
+pub fn truncate_cols(s: &str, max: u16) -> String {
+    if cols(s) <= max {
+        return s.to_string();
+    }
+    if max == 0 {
+        return String::new();
+    }
+    // Reserve one column for the ellipsis.
+    let budget = max.saturating_sub(1);
+    let mut used = 0u16;
+    let mut out = String::new();
+    for ch in s.chars() {
+        let w = cols(ch.encode_utf8(&mut [0u8; 4]));
+        if used + w > budget {
+            break;
+        }
+        used += w;
+        out.push(ch);
+    }
+    out.push('…');
+    out
+}
+
+/// Picks the first (richest) candidate pair that fits side by side in `width` columns
+/// with at least `gap` columns between them.
+///
+/// Candidates are ordered most- to least-detailed; the last one is the floor and is
+/// returned even if it does not fit, so callers always get something to render.
+pub fn pick_pair<'a>(
+    width: u16,
+    gap: u16,
+    candidates: &[(&'a str, &'a str)],
+) -> (&'a str, &'a str) {
+    let fits = |left: &str, right: &str| {
+        let needed = cols(left)
+            .saturating_add(cols(right))
+            .saturating_add(if right.is_empty() { 0 } else { gap });
+        needed <= width
+    };
+    for &(left, right) in candidates {
+        if fits(left, right) {
+            return (left, right);
+        }
+    }
+    candidates.last().copied().unwrap_or(("", ""))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// The bug these helpers exist to prevent: byte length overstates the width of the
+    /// glyphs socktop puts in its header, which is what pushed the right-hand text into
+    /// the title in the first place.
+    #[test]
+    fn cols_counts_columns_not_bytes() {
+        assert_eq!(cols("abc"), 3);
+        // Stopwatch: 3 bytes, 1 column.
+        assert_eq!("⏱".len(), 3);
+        assert_eq!(cols("⏱"), 1);
+        // Lock: 4 bytes, 2 columns.
+        assert_eq!("🔒".len(), 4);
+        assert_eq!(cols("🔒"), 2);
+        assert_eq!(cols("⏱ 500ms metrics | 2000ms procs"), 30);
+    }
+
+    #[test]
+    fn truncate_respects_the_column_budget() {
+        assert_eq!(truncate_cols("cachyos-gaming", 20), "cachyos-gaming");
+        assert_eq!(truncate_cols("cachyos-gaming", 14), "cachyos-gaming");
+        assert_eq!(truncate_cols("cachyos-gaming", 10), "cachyos-g…");
+        assert_eq!(cols(&truncate_cols("cachyos-gaming", 10)), 10);
+        assert_eq!(truncate_cols("cachyos-gaming", 1), "…");
+        assert_eq!(truncate_cols("cachyos-gaming", 0), "");
+    }
+
+    /// Truncation must never land mid-character or overrun the budget on wide glyphs.
+    #[test]
+    fn truncate_handles_wide_and_multibyte_characters() {
+        for max in 0..12u16 {
+            let out = truncate_cols("🔒🔒🔒 TLS", max);
+            assert!(cols(&out) <= max, "{out:?} exceeds {max} columns");
+            assert!(out.chars().all(|c| c != '\u{fffd}'), "{out:?} split a char");
+        }
+        // A wide glyph that cannot fit beside the ellipsis is dropped whole.
+        assert_eq!(truncate_cols("🔒ab", 2), "…");
+    }
+
+    #[test]
+    fn pick_pair_takes_the_richest_that_fits() {
+        let candidates = [
+            ("full left text", "full right text"),
+            ("left text", "right text"),
+            ("left", "right"),
+        ];
+        assert_eq!(pick_pair(80, 2, &candidates), candidates[0]);
+        assert_eq!(pick_pair(24, 2, &candidates), candidates[1]);
+        assert_eq!(pick_pair(12, 2, &candidates), candidates[2]);
+        // Below the floor the last candidate is still returned.
+        assert_eq!(pick_pair(1, 2, &candidates), candidates[2]);
+    }
+
+    /// The gap is what keeps the two pieces from touching; it must not be charged when
+    /// there is no right-hand piece to separate.
+    #[test]
+    fn pick_pair_only_charges_the_gap_when_both_sides_are_present() {
+        let candidates = [("0123456789", "x"), ("0123456789", "")];
+        assert_eq!(pick_pair(11, 2, &candidates), candidates[1]);
+        assert_eq!(pick_pair(13, 2, &candidates), candidates[0]);
+    }
+}

socktop/src/ui/gpu.rs

@@ -121,3 +121,209 @@ pub fn draw_gpu(f: &mut ratatui::Frame<'_>, area: Rect, m: Option<&Metrics>) {
         );
     }
 }
+
+/// One-line GPU strip for compact mode: no device name (it is the first thing to lose
+/// value when rows are scarce), just utilisation and VRAM on the single content row
+/// between the block borders. Only the first GPU fits; the title says so when there are
+/// more.
+pub fn draw_gpu_compact(f: &mut ratatui::Frame<'_>, area: Rect, m: Option<&Metrics>) {
+    let gpus = m.and_then(|mm| mm.gpus.as_ref());
+    let count = gpus.map(|g| g.len()).unwrap_or(0);
+    let title = if count > 1 {
+        format!("GPU (1/{count})")
+    } else {
+        "GPU".to_string()
+    };
+    f.render_widget(Block::default().borders(Borders::ALL).title(title), area);
+
+    if area.height < 3 || area.width <= 2 {
+        return;
+    }
+    let inner = Rect {
+        x: area.x + 1,
+        y: area.y + 1,
+        width: area.width - 2,
+        height: 1,
+    };
+
+    let Some(g) = gpus.and_then(|v| v.first()) else {
+        f.render_widget(Paragraph::new("No GPUs"), inner);
+        return;
+    };
+
+    let util = g.utilization.unwrap_or(0.0).clamp(0.0, 100.0) as u16;
+    let used = g.mem_used.unwrap_or(0);
+    let total = g.mem_total.unwrap_or(1);
+    let mem_ratio = if total > 0 {
+        (used as f64 / total as f64).clamp(0.0, 1.0)
+    } else {
+        0.0
+    };
+    let util_label = format!("util: {util}%");
+    let mem_label = format!(
+        "vram: {}/{} ({}%)",
+        fmt_bytes(used),
+        fmt_bytes(total),
+        (mem_ratio * 100.0).round() as u16
+    );
+
+    // Bars are sized explicitly rather than left to stretch: an idle bar renders as
+    // empty cells, so a full-width one turns into a long blank run between two labels.
+    const MIN_GAUGE_W: u16 = 6;
+    const MAX_GAUGE_W: u16 = 24;
+    let labels_w = util_label.len() as u16 + mem_label.len() as u16 + 4; // one space each side
+    let gauge_w = inner
+        .width
+        .saturating_sub(labels_w)
+        .min(2 * MAX_GAUGE_W)
+        .div_euclid(2);
+
+    // Too narrow for bars worth drawing: keep the numbers, drop the bars.
+    if gauge_w < MIN_GAUGE_W {
+        f.render_widget(
+            Paragraph::new(Span::raw(format!("{util_label}  {mem_label}")))
+                .style(Style::default().fg(Color::Gray)),
+            inner,
+        );
+        return;
+    }
+
+    // Each label leads its own bar. Bar-then-label (as the tall panel does) is ambiguous
+    // on a single line: with an idle bar rendering empty, the next pair's fill ends up
+    // flush against the previous pair's text and reads as belonging to it.
+    let mut x = inner.x;
+    let mut place = |w: u16| {
+        let r = Rect {
+            x,
+            y: inner.y,
+            width: w,
+            height: 1,
+        };
+        x += w;
+        r
+    };
+    let util_rect = place(util_label.len() as u16 + 2);
+    let util_bar = place(gauge_w);
+    let mem_rect = place(mem_label.len() as u16 + 2);
+    let mem_bar = place(gauge_w);
+
+    let label = |text: &str| {
+        Paragraph::new(Span::raw(format!(" {text} "))).style(Style::default().fg(Color::Gray))
+    };
+
+    f.render_widget(label(&util_label), util_rect);
+    f.render_widget(
+        Gauge::default()
+            .gauge_style(Style::default().fg(Color::Green))
+            .label(Span::raw(""))
+            .ratio(util as f64 / 100.0),
+        util_bar,
+    );
+    f.render_widget(label(&mem_label), mem_rect);
+    f.render_widget(
+        Gauge::default()
+            .gauge_style(Style::default().fg(Color::LightMagenta))
+            .label(Span::raw(""))
+            .ratio(mem_ratio),
+        mem_bar,
+    );
+}
+
+#[cfg(test)]
+mod render_tests {
+    use super::*;
+    use ratatui::Terminal;
+    use ratatui::backend::TestBackend;
+    use socktop_connector::{GpuInfo, Metrics};
+
+    fn gpu(name: &str) -> GpuInfo {
+        GpuInfo {
+            name: Some(name.into()),
+            vendor: None,
+            utilization: Some(42.0),
+            mem_used: Some(4_724_464_025),
+            mem_total: Some(17_070_817_280),
+            temp: None,
+        }
+    }
+
+    fn metrics(gpus: Option<Vec<GpuInfo>>) -> Metrics {
+        Metrics {
+            cpu_total: 0.0,
+            cpu_per_core: vec![],
+            mem_total: 1024,
+            mem_used: 0,
+            swap_total: 0,
+            swap_used: 0,
+            hostname: "t".into(),
+            cpu_temp_c: None,
+            disks: vec![],
+            networks: vec![],
+            top_processes: vec![],
+            gpus,
+            process_count: Some(0),
+        }
+    }
+
+    fn render(width: u16, m: &Metrics) -> String {
+        let mut terminal = Terminal::new(TestBackend::new(width, 3)).unwrap();
+        terminal
+            .draw(|f| draw_gpu_compact(f, Rect::new(0, 0, width, 3), Some(m)))
+            .unwrap();
+        let buf = terminal.backend().buffer();
+        let mut out = String::new();
+        for y in 0..buf.area().height {
+            for x in 0..buf.area().width {
+                out.push_str(buf[(x, y)].symbol());
+            }
+            out.push('\n');
+        }
+        out
+    }
+
+    /// Compact mode drops the device name — the row is one line and the numbers are
+    /// what the space is for.
+    #[test]
+    fn compact_strip_omits_the_device_name() {
+        let m = metrics(Some(vec![gpu("NVIDIA GeForce RTX 5080")]));
+        let out = render(80, &m);
+        assert!(
+            !out.contains("NVIDIA"),
+            "name leaked into compact strip:\n{out}"
+        );
+        assert!(out.contains("util: 42%"), "{out}");
+        assert!(out.contains("vram: 4.4G/15.9G (28%)"), "{out}");
+    }
+
+    /// A second GPU cannot fit on one line, so the title has to say the strip is partial
+    /// rather than silently showing only the first card.
+    #[test]
+    fn multiple_gpus_are_flagged_in_the_title() {
+        let one = render(80, &metrics(Some(vec![gpu("a")])));
+        assert!(one.contains("GPU") && !one.contains("1/"), "{one}");
+
+        let two = render(80, &metrics(Some(vec![gpu("a"), gpu("b")])));
+        assert!(two.contains("GPU (1/2)"), "{two}");
+    }
+
+    /// Narrow terminals drop the gauges rather than rendering two-cell stubs, but must
+    /// never drop the numbers.
+    #[test]
+    fn narrow_strip_keeps_the_numbers() {
+        let m = metrics(Some(vec![gpu("a")]));
+        for width in [20u16, 30, 40, 47, 48, 80, 200] {
+            let out = render(width, &m);
+            if width >= 40 {
+                assert!(out.contains("util: 42%"), "width {width}:\n{out}");
+            }
+            // No panic, and the block always closes on the last row.
+            assert_eq!(out.lines().count(), 3, "width {width}");
+        }
+    }
+
+    #[test]
+    fn missing_gpu_payload_does_not_panic() {
+        assert!(render(80, &metrics(None)).contains("No GPUs"));
+        assert!(render(80, &metrics(Some(vec![]))).contains("No GPUs"));
+    }
+}

socktop/src/ui/header.rs

@@ -1,44 +1,232 @@
-//! Top header with hostname and CPU temperature indicator.
+//! Top header with hostname, connection status and polling intervals.
+//!
+//! The row carries two pieces of text — session identity on the left, polling intervals
+//! on the right — and both matter. Rather than let the right one overwrite the left when
+//! they no longer both fit, the header drops detail in priority order: the hostname and
+//! the intervals are what survive longest, because they are what tells you *which* host
+//! you are looking at and how fresh the numbers are.
 
+use crate::ui::fit::{cols, pick_pair, truncate_cols};
 use ratatui::{
     layout::Rect,
     text::{Line, Span},
     widgets::{Block, Borders, Paragraph},
 };
 
-/// Build the header's left-side title from session state. Callers cache the
-/// returned String and only rebuild it when one of the inputs changes.
-pub fn build_header_title(hostname: Option<&str>, is_tls: bool, has_token: bool) -> String {
-    let base = match hostname {
-        Some(h) => format!("socktop — host: {h}"),
-        None => "socktop — connecting...".into(),
-    };
-    let tls_txt = if is_tls { "🔒 TLS" } else { "🔒✗ TLS" };
-    let mut parts = vec![base, tls_txt.into()];
-    if has_token {
-        parts.push("🔑 token".into());
-    }
-    parts.push("(a: about, h: help, q: quit)".into());
-    parts.join(" | ")
+/// Columns kept clear between the left and right halves.
+const GAP: u16 = 2;
+/// Never shorten the hostname below this before dropping the intervals instead.
+const HOSTNAME_FLOOR: u16 = 8;
+
+/// Session state the header renders.
+#[derive(Clone, Copy)]
+pub struct HeaderState<'a> {
+    pub hostname: Option<&'a str>,
+    pub is_tls: bool,
+    pub has_token: bool,
+    pub metrics_ms: u128,
+    pub procs_ms: u128,
 }
 
-/// Build the right-side polling interval text. Callers cache this string.
-pub fn build_header_intervals(metrics_ms: u128, procs_ms: u128) -> String {
-    format!("⏱ {metrics_ms}ms metrics | {procs_ms}ms procs")
+/// Builds the left and right halves of the header for a row `width` columns wide.
+///
+/// Detail is dropped in this order as the row narrows: the key hints, then the TLS/token
+/// badges, then the `socktop — host:` prefix (leaving the bare hostname), then the
+/// `metrics`/`procs` words, and only then is the hostname itself shortened. The two
+/// halves are always sized to sit side by side, so neither can paint over the other.
+///
+/// Callers cache the result and rebuild it only when the state or the width changes.
+pub fn build_header(state: HeaderState<'_>, width: u16) -> (String, String) {
+    let host = state.hostname.unwrap_or("connecting...");
+    let tls = if state.is_tls {
+        "🔒 TLS"
+    } else {
+        "🔒✗ TLS"
+    };
+    let badges = if state.has_token {
+        format!("{tls} | 🔑 token")
+    } else {
+        tls.to_string()
+    };
+
+    let named = format!("socktop — host: {host}");
+    let with_badges = format!("{named} | {badges}");
+    let with_keys = format!("{with_badges} | (a: about, h: help, q: quit)");
+
+    let intervals = format!(
+        "⏱ {}ms metrics | {}ms procs",
+        state.metrics_ms, state.procs_ms
+    );
+    let intervals_short = format!("⏱ {}ms | {}ms", state.metrics_ms, state.procs_ms);
+
+    // Richest first. The bare hostname is reached before the intervals lose their
+    // labels, and the hostname is only shortened once nothing else is left to give.
+    let ladder = [
+        (with_keys.as_str(), intervals.as_str()),
+        (with_badges.as_str(), intervals.as_str()),
+        (named.as_str(), intervals.as_str()),
+        (host, intervals.as_str()),
+        (host, intervals_short.as_str()),
+    ];
+    let (left, right) = pick_pair(width, GAP, &ladder);
+    if cols(left) + cols(right) + GAP <= width {
+        return (left.to_string(), right.to_string());
+    }
+
+    // Past the floor of the ladder: shorten the hostname, and give up the intervals only
+    // if even a stub of a hostname will not fit beside them.
+    let room = width
+        .saturating_sub(cols(&intervals_short))
+        .saturating_sub(GAP);
+    if room >= HOSTNAME_FLOOR {
+        return (truncate_cols(host, room), intervals_short);
+    }
+    (truncate_cols(host, width), String::new())
 }
 
 pub fn draw_header(f: &mut ratatui::Frame<'_>, area: Rect, title: &str, intervals: &str) {
     f.render_widget(Block::default().title(title).borders(Borders::BOTTOM), area);
 
-    let intervals_width = intervals.len() as u16;
-    if area.width > intervals_width + 2 {
+    if intervals.is_empty() {
+        return;
+    }
+    let intervals_width = cols(intervals);
+    if area.width >= intervals_width {
         let right_area = Rect {
-            x: area.x + area.width.saturating_sub(intervals_width + 1),
+            x: area.x + area.width - intervals_width,
             y: area.y,
             width: intervals_width,
             height: 1,
         };
-        let intervals_line = Line::from(Span::raw(intervals));
-        f.render_widget(Paragraph::new(intervals_line), right_area);
+        f.render_widget(Paragraph::new(Line::from(Span::raw(intervals))), right_area);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn state(hostname: Option<&str>) -> HeaderState<'_> {
+        HeaderState {
+            hostname,
+            is_tls: false,
+            has_token: false,
+            metrics_ms: 500,
+            procs_ms: 2000,
+        }
+    }
+
+    /// The defect this replaces: the two halves were painted independently, so below
+    /// ~105 columns the right half landed on top of the title. Whatever the width, they
+    /// must now fit side by side.
+    #[test]
+    fn halves_never_overlap_at_any_width() {
+        for width in 0..=200u16 {
+            let (left, right) = build_header(state(Some("cachyos-gaming")), width);
+            let used = cols(&left) + cols(&right);
+            if right.is_empty() {
+                assert!(cols(&left) <= width, "width {width}: {left:?} overflows");
+            } else {
+                assert!(
+                    used + GAP <= width,
+                    "width {width}: {left:?} + {right:?} = {used} cols, no room for both"
+                );
+            }
+        }
+    }
+
+    /// Hostname and intervals are the two things worth keeping; everything else is
+    /// context that can go.
+    #[test]
+    fn hostname_and_intervals_survive_longest() {
+        for width in 34..=200u16 {
+            let (left, right) = build_header(state(Some("cachyos-gaming")), width);
+            assert!(
+                left.contains("cachyos-gaming"),
+                "width {width}: lost the hostname ({left:?})"
+            );
+            assert!(
+                right.contains("500ms") && right.contains("2000ms"),
+                "width {width}: lost the intervals ({right:?})"
+            );
+        }
+    }
+
+    /// The ladder from the design: key hints, then badges, then the prefix, then the
+    /// interval labels, then the hostname itself.
+    #[test]
+    fn detail_is_dropped_in_priority_order() {
+        let s = state(Some("cachyos-gaming"));
+
+        let (left, right) = build_header(s, 120);
+        assert_eq!(
+            left,
+            "socktop — host: cachyos-gaming | 🔒✗ TLS | (a: about, h: help, q: quit)"
+        );
+        assert_eq!(right, "⏱ 500ms metrics | 2000ms procs");
+
+        // Key hints go first.
+        let (left, _) = build_header(s, 80);
+        assert_eq!(left, "socktop — host: cachyos-gaming | 🔒✗ TLS");
+
+        // Then the badges.
+        let (left, _) = build_header(s, 70);
+        assert_eq!(left, "socktop — host: cachyos-gaming");
+
+        // Then the prefix, leaving the bare hostname.
+        let (left, right) = build_header(s, 50);
+        assert_eq!(left, "cachyos-gaming");
+        assert_eq!(right, "⏱ 500ms metrics | 2000ms procs");
+
+        // Then the interval labels.
+        let (left, right) = build_header(s, 34);
+        assert_eq!(left, "cachyos-gaming");
+        assert_eq!(right, "⏱ 500ms | 2000ms");
+
+        // Only then is the hostname itself shortened.
+        // 30 columns - 16 for the short intervals - 2 gap leaves 12 for the hostname.
+        let (left, right) = build_header(s, 30);
+        assert_eq!(left, "cachyos-gam…");
+        assert_eq!(right, "⏱ 500ms | 2000ms");
+    }
+
+    /// A long hostname must not push the intervals off the row.
+    #[test]
+    fn a_long_hostname_is_shortened_rather_than_winning_the_row() {
+        let long = "a-very-long-hostname-that-will-not-fit-anywhere";
+        for width in 30..=100u16 {
+            let (left, right) = build_header(state(Some(long)), width);
+            assert!(!right.is_empty(), "width {width}: intervals were dropped");
+            assert!(cols(&left) + cols(&right) + GAP <= width, "width {width}");
+        }
+    }
+
+    /// Widths too small for both: the hostname is the last thing standing.
+    #[test]
+    fn hostname_is_the_final_survivor() {
+        let (left, right) = build_header(state(Some("cachyos-gaming")), 20);
+        assert!(right.is_empty(), "intervals should have been dropped");
+        assert!(!left.is_empty());
+        assert!(cols(&left) <= 20);
+    }
+
+    #[test]
+    fn tls_and_token_badges_appear_when_there_is_room() {
+        let s = HeaderState {
+            hostname: Some("host"),
+            is_tls: true,
+            has_token: true,
+            metrics_ms: 500,
+            procs_ms: 2000,
+        };
+        let (left, _) = build_header(s, 200);
+        assert!(left.contains("🔒 TLS"), "{left}");
+        assert!(left.contains("🔑 token"), "{left}");
+    }
+
+    #[test]
+    fn a_missing_hostname_reads_as_connecting() {
+        let (left, _) = build_header(state(None), 120);
+        assert!(left.contains("connecting"), "{left}");
     }
 }

socktop/src/ui/layout.rs

@@ -0,0 +1,352 @@
+//! Root layout computation, shared by the draw path and the input hit-testing paths.
+//!
+//! Two modes:
+//!
+//! * [`LayoutMode::Normal`] — the full layout. CPU graph and per-core bars on top,
+//!   Memory over Swap on the left with the GPU panel beside them, then Disks and the
+//!   network graphs next to the process table.
+//!
+//! * [`LayoutMode::Compact`] — entered when the window is too short for the Disks pane
+//!   to render even one complete disk card. Disks is dropped, Memory and Swap move side
+//!   by side into the space it vacated, the GPU collapses to a single full-width line
+//!   (and disappears entirely when the host has no GPU), and every row reclaimed goes to
+//!   the CPU graph and per-core bars — which in the fixed layout are squeezed to nothing
+//!   long before the rest of the panes stop being useful.
+
+use ratatui::layout::{Constraint, Direction, Layout, Rect};
+
+/// Which of the two layouts [`compute`] produced.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum LayoutMode {
+    Normal,
+    Compact,
+}
+
+impl LayoutMode {
+    pub fn is_compact(self) -> bool {
+        matches!(self, LayoutMode::Compact)
+    }
+}
+
+/// Rows the Disks pane needs before it can show one disk card: the card itself is
+/// 3 rows (`disks::draw_disks`) plus the pane's own top and bottom border.
+const DISKS_MIN_H: u16 = 5;
+
+/// Header line.
+const HEADER_H: u16 = 1;
+/// Memory and Swap gauges: 1 content row between borders.
+const GAUGE_H: u16 = 3;
+/// A network graph at its preferred height.
+const NET_H: u16 = 5;
+
+// Compact-mode budget. The top row is kept at `TOP_MIN_H` (3 content rows between
+// borders) before the network graphs are allowed to shrink, because restoring the CPU
+// panes is the entire point of the mode.
+const TOP_MIN_H: u16 = 5;
+const BOTTOM_PREF_H: u16 = GAUGE_H + 2 * NET_H;
+const BOTTOM_MIN_H: u16 = GAUGE_H + 2 * 3;
+
+/// Every pane rect for one frame. `disks` and `gpu` are `None` when the mode omits them.
+#[derive(Clone, Copy, Debug)]
+pub struct AppLayout {
+    pub mode: LayoutMode,
+    pub header: Rect,
+    pub cpu: Rect,
+    pub per_core: Rect,
+    pub gpu: Option<Rect>,
+    pub mem: Rect,
+    pub swap: Rect,
+    pub disks: Option<Rect>,
+    pub download: Rect,
+    pub upload: Rect,
+    pub procs: Rect,
+}
+
+/// Splits `area` into pane rects.
+///
+/// `force_compact` comes from `--compact` and pins the compact layout at any size.
+/// `has_gpu` decides whether compact mode reserves its one-line GPU strip; it is false
+/// until the first metrics payload arrives, so a GPU-less host never reserves the row.
+pub fn compute(area: Rect, force_compact: bool, has_gpu: bool) -> AppLayout {
+    if force_compact {
+        return compact(area, has_gpu);
+    }
+    let normal = normal(area);
+    match normal.disks {
+        Some(d) if d.height >= DISKS_MIN_H => normal,
+        _ => compact(area, has_gpu),
+    }
+}
+
+fn split(area: Rect, dir: Direction, constraints: &[Constraint]) -> std::rc::Rc<[Rect]> {
+    Layout::default()
+        .direction(dir)
+        .constraints(constraints)
+        .split(area)
+}
+
+/// 66/34 split used by every full-width row in the normal layout.
+fn left_right(area: Rect) -> std::rc::Rc<[Rect]> {
+    split(
+        area,
+        Direction::Horizontal,
+        &[Constraint::Percentage(66), Constraint::Percentage(34)],
+    )
+}
+
+fn normal(area: Rect) -> AppLayout {
+    let rows = split(
+        area,
+        Direction::Vertical,
+        &[
+            Constraint::Length(HEADER_H), // header
+            Constraint::Ratio(1, 3),      // top row
+            Constraint::Length(GAUGE_H),  // memory (left) + GPU (right, part 1)
+            Constraint::Length(GAUGE_H),  // swap (left)   + GPU (right, part 2)
+            Constraint::Min(2 * NET_H),   // bottom: disks + net (left), top procs (right)
+        ],
+    );
+
+    let top = left_right(rows[1]);
+    let mem_lr = left_right(rows[2]);
+    let swap_lr = left_right(rows[3]);
+
+    // GPU spans the same vertical space as Memory + Swap.
+    let gpu = Rect {
+        x: mem_lr[1].x,
+        y: mem_lr[1].y,
+        width: mem_lr[1].width,
+        height: mem_lr[1].height + swap_lr[1].height,
+    };
+
+    let bottom = split(
+        rows[4],
+        Direction::Horizontal,
+        &[Constraint::Percentage(60), Constraint::Percentage(40)],
+    );
+    let left_stack = split(
+        bottom[0],
+        Direction::Vertical,
+        &[
+            Constraint::Min(4),        // disks absorbs the slack
+            Constraint::Length(NET_H), // download
+            Constraint::Length(NET_H), // upload
+        ],
+    );
+
+    AppLayout {
+        mode: LayoutMode::Normal,
+        header: rows[0],
+        cpu: top[0],
+        per_core: top[1],
+        gpu: Some(gpu),
+        mem: mem_lr[0],
+        swap: swap_lr[0],
+        disks: Some(left_stack[0]),
+        download: left_stack[1],
+        upload: left_stack[2],
+        procs: bottom[1],
+    }
+}
+
+fn compact(area: Rect, has_gpu: bool) -> AppLayout {
+    let gpu_h = if has_gpu { GAUGE_H } else { 0 };
+    let avail = area.height.saturating_sub(HEADER_H + gpu_h);
+
+    // Give the top row its floor first, then share any surplus with the bottom so the
+    // process table keeps growing with the window instead of staying pinned at 13 rows.
+    let (top_h, bottom_h) = if avail >= TOP_MIN_H + BOTTOM_PREF_H {
+        let top = TOP_MIN_H + (avail - TOP_MIN_H - BOTTOM_PREF_H) / 2;
+        (top, avail - top)
+    } else if avail >= TOP_MIN_H + BOTTOM_MIN_H {
+        (TOP_MIN_H, avail - TOP_MIN_H)
+    } else {
+        // Smaller than both floors: the network graphs are already at their minimum, so
+        // the top row takes what is left (panes clip below this point).
+        let bottom = BOTTOM_MIN_H.min(avail);
+        (avail - bottom, bottom)
+    };
+
+    let rows = split(
+        area,
+        Direction::Vertical,
+        &[
+            Constraint::Length(HEADER_H),
+            Constraint::Length(top_h),
+            Constraint::Length(gpu_h),
+            Constraint::Length(bottom_h),
+        ],
+    );
+
+    let top = left_right(rows[1]);
+
+    let bottom = split(
+        rows[3],
+        Direction::Horizontal,
+        &[Constraint::Percentage(60), Constraint::Percentage(40)],
+    );
+    // Memory + Swap take the row Disks used to occupy; the graphs share what is left.
+    let left_stack = split(
+        bottom[0],
+        Direction::Vertical,
+        &[
+            Constraint::Length(GAUGE_H),
+            Constraint::Fill(1),
+            Constraint::Fill(1),
+        ],
+    );
+    let gauges = split(
+        left_stack[0],
+        Direction::Horizontal,
+        &[Constraint::Percentage(50), Constraint::Percentage(50)],
+    );
+
+    AppLayout {
+        mode: LayoutMode::Compact,
+        header: rows[0],
+        cpu: top[0],
+        per_core: top[1],
+        gpu: has_gpu.then_some(rows[2]),
+        mem: gauges[0],
+        swap: gauges[1],
+        disks: None,
+        download: left_stack[1],
+        upload: left_stack[2],
+        procs: bottom[1],
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn area(w: u16, h: u16) -> Rect {
+        Rect::new(0, 0, w, h)
+    }
+
+    /// The height where the normal layout still fits a full disk card. Below it the CPU
+    /// panes are the ones that collapse, which is what compact mode exists to prevent.
+    #[test]
+    fn tall_window_stays_normal() {
+        let l = compute(area(120, 40), false, true);
+        assert_eq!(l.mode, LayoutMode::Normal);
+        assert!(l.disks.expect("disks pane").height >= DISKS_MIN_H);
+    }
+
+    #[test]
+    fn short_window_switches_to_compact() {
+        let l = compute(area(120, 24), false, true);
+        assert_eq!(l.mode, LayoutMode::Compact);
+        assert!(l.disks.is_none());
+    }
+
+    /// The switch happens exactly when Disks can no longer show one card, and never
+    /// oscillates: every height above the crossover is normal, every height below is
+    /// compact.
+    #[test]
+    fn mode_is_monotonic_in_height() {
+        let mut first_normal = None;
+        for h in 10..=60u16 {
+            let mode = compute(area(120, h), false, true).mode;
+            match (mode, first_normal) {
+                (LayoutMode::Normal, None) => first_normal = Some(h),
+                (LayoutMode::Compact, Some(prev)) => {
+                    panic!("height {h} went back to compact after normal at {prev}")
+                }
+                _ => {}
+            }
+        }
+        assert!(first_normal.is_some(), "never reached the normal layout");
+    }
+
+    #[test]
+    fn force_compact_overrides_a_tall_window() {
+        let l = compute(area(200, 80), true, true);
+        assert_eq!(l.mode, LayoutMode::Compact);
+        assert!(l.disks.is_none());
+    }
+
+    #[test]
+    fn compact_drops_the_gpu_row_without_a_gpu() {
+        let with = compute(area(120, 24), true, true);
+        let without = compute(area(120, 24), true, false);
+        assert!(with.gpu.is_some());
+        assert_eq!(with.gpu.expect("gpu strip").height, GAUGE_H);
+        assert!(without.gpu.is_none());
+        // The rows a GPU-less host saves are shared between the CPU panes and the
+        // bottom half, and none of them are left as a gap.
+        assert!(without.cpu.height > with.cpu.height);
+        assert!(without.procs.height > with.procs.height);
+        assert_eq!(without.procs.y + without.procs.height, 24);
+    }
+
+    /// Compact exists to keep the CPU graph and per-core bars drawable: both need
+    /// content rows inside their borders.
+    #[test]
+    fn compact_keeps_the_cpu_panes_drawable() {
+        for h in 18..=32u16 {
+            let l = compute(area(120, h), false, true);
+            assert_eq!(l.mode, LayoutMode::Compact, "height {h}");
+            assert!(
+                l.cpu.height >= TOP_MIN_H,
+                "height {h}: cpu pane only {} rows",
+                l.cpu.height
+            );
+            assert_eq!(l.per_core.height, l.cpu.height);
+        }
+    }
+
+    /// Regression guard for the bug this mode fixes: at 18 rows the old fixed layout
+    /// left the top row with no drawable interior at all.
+    #[test]
+    fn compact_beats_the_fixed_layout_at_18_rows() {
+        let compact = compute(area(120, 18), false, true);
+        let fixed = normal(area(120, 18));
+        assert!(fixed.cpu.height <= 2, "fixed layout unexpectedly usable");
+        assert!(compact.cpu.height > fixed.cpu.height);
+    }
+
+    #[test]
+    fn compact_panes_tile_the_area_without_gaps() {
+        for h in 16..=32u16 {
+            for has_gpu in [true, false] {
+                let l = compute(area(120, h), true, has_gpu);
+                assert_eq!(l.header.y, 0);
+                assert_eq!(l.cpu.y, l.header.y + l.header.height);
+                assert_eq!(l.per_core.x, l.cpu.x + l.cpu.width);
+
+                let after_cpu = l.cpu.y + l.cpu.height;
+                let bottom_y = match l.gpu {
+                    Some(g) => {
+                        assert_eq!(g.y, after_cpu);
+                        assert_eq!(g.width, 120, "gpu strip spans the full width");
+                        g.y + g.height
+                    }
+                    None => after_cpu,
+                };
+                assert_eq!(l.mem.y, bottom_y);
+                // Memory and Swap sit side by side on one row.
+                assert_eq!(l.swap.y, l.mem.y);
+                assert_eq!(l.swap.x, l.mem.x + l.mem.width);
+                assert_eq!(l.mem.height, GAUGE_H);
+                assert_eq!(l.download.y, l.mem.y + l.mem.height);
+                assert_eq!(l.upload.y, l.download.y + l.download.height);
+                assert_eq!(l.procs.y, bottom_y);
+            }
+        }
+    }
+
+    /// A degenerate size must not panic or produce rects outside the frame.
+    #[test]
+    fn tiny_windows_stay_inside_the_frame() {
+        for h in 0..=16u16 {
+            for w in [0u16, 1, 20, 80] {
+                let l = compute(area(w, h), false, true);
+                for r in [l.header, l.cpu, l.per_core, l.mem, l.swap, l.procs] {
+                    assert!(r.y + r.height <= h, "{r:?} escapes height {h}");
+                    assert!(r.x + r.width <= w, "{r:?} escapes width {w}");
+                }
+            }
+        }
+    }
+}

socktop/src/ui/mod.rs

@@ -2,8 +2,10 @@
 
 pub mod cpu;
 pub mod disks;
+pub mod fit;
 pub mod gpu;
 pub mod header;
+pub mod layout;
 pub mod mem;
 pub mod modal;
 pub mod modal_connection;

socktop/src/ui/processes.rs

@@ -134,14 +134,83 @@ pub fn rebuild_row_cache(metrics: &Metrics, out: &mut Vec<CachedRow>) -> f32 {
     peak
 }
 
-// Keep the original header widths here so drawing and hit-testing match.
-const COLS: [Constraint; 5] = [
-    Constraint::Length(8),      // PID
-    Constraint::Percentage(40), // Name
-    Constraint::Length(8),      // CPU %
-    Constraint::Length(12),     // Mem
-    Constraint::Length(8),      // Mem %
-];
+const PID_W: u16 = 8;
+const CPU_W: u16 = 8;
+const MEM_W: u16 = 12;
+const MEM_PCT_W: u16 = 8;
+/// Columns the Name field needs to identify anything. Every other column is only added
+/// once Name already has this much, so Name can no longer be squeezed to nothing.
+const NAME_MIN_W: u16 = 8;
+/// `Table::column_spacing`.
+const COL_SPACING: u16 = 1;
+
+/// Which process columns fit in the pane, and where they sit.
+///
+/// The table used to hand the layout solver a fixed, over-constrained set, so on a narrow
+/// pane the solver crushed the percentage-sized Name column to nothing while the fixed
+/// PID and Mem % columns kept their full width — losing the one field that identifies the
+/// process while keeping the ones that do not.
+///
+/// Columns are now added in priority order as the pane widens, so they are shed in
+/// reverse as it narrows: Name is unconditional, then CPU %, then Mem, then PID, and
+/// Mem % last (it is derivable from Mem, so it is the least costly to lose).
+///
+/// Both the draw path and the header-click hit-testing build this from the same width, so
+/// a sort click always lands on the column the user can actually see.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct ProcColumns {
+    pub pid: bool,
+    pub cpu: bool,
+    pub mem: bool,
+    pub mem_pct: bool,
+}
+
+impl ProcColumns {
+    pub fn for_width(width: u16) -> Self {
+        // Each tier is the previous one plus a column and the gap before it.
+        let with_cpu = NAME_MIN_W + COL_SPACING + CPU_W;
+        let with_mem = with_cpu + COL_SPACING + MEM_W;
+        let with_pid = with_mem + COL_SPACING + PID_W;
+        let with_mem_pct = with_pid + COL_SPACING + MEM_PCT_W;
+        Self {
+            cpu: width >= with_cpu,
+            mem: width >= with_mem,
+            pid: width >= with_pid,
+            mem_pct: width >= with_mem_pct,
+        }
+    }
+
+    /// Column constraints in render order. Name takes whatever the others leave.
+    pub fn constraints(&self) -> Vec<Constraint> {
+        let mut c = Vec::with_capacity(5);
+        if self.pid {
+            c.push(Constraint::Length(PID_W));
+        }
+        c.push(Constraint::Fill(1)); // Name
+        if self.cpu {
+            c.push(Constraint::Length(CPU_W));
+        }
+        if self.mem {
+            c.push(Constraint::Length(MEM_W));
+        }
+        if self.mem_pct {
+            c.push(Constraint::Length(MEM_PCT_W));
+        }
+        c
+    }
+
+    /// Position of the CPU % column, which is clickable to sort. `None` when too narrow
+    /// to render it.
+    pub fn cpu_index(&self) -> Option<usize> {
+        self.cpu.then(|| 1 + usize::from(self.pid))
+    }
+
+    /// Position of the Mem column, which is clickable to sort.
+    pub fn mem_index(&self) -> Option<usize> {
+        self.mem
+            .then(|| 1 + usize::from(self.pid) + usize::from(self.cpu))
+    }
+}
 
 pub fn draw_top_processes(f: &mut ratatui::Frame<'_>, area: Rect, params: ProcessDisplayParams) {
     // Draw outer block and title
@@ -233,6 +302,8 @@ pub fn draw_top_processes(f: &mut ratatui::Frame<'_>, area: Rect, params: Proces
             .fold(0.0_f32, f32::max)
     };
 
+    let columns = ProcColumns::for_width(content.width);
+
     let rows_iter = idxs.iter().skip(offset).take(show_n).map(|&ix| {
         let p = &mm.top_processes[ix];
 
@@ -304,16 +375,29 @@ pub fn draw_top_processes(f: &mut ratatui::Frame<'_>, area: Rect, params: Proces
                 .add_modifier(Modifier::BOLD);
         }
 
-        ratatui::widgets::Row::new(vec![
-            ratatui::widgets::Cell::from(pid_span).style(Style::default().fg(Color::DarkGray)),
-            ratatui::widgets::Cell::from(name_span),
-            ratatui::widgets::Cell::from(Span::raw(cpu_span_text))
-                .style(Style::default().fg(cpu_fg)),
-            ratatui::widgets::Cell::from(Span::raw(mem_span_text)),
-            ratatui::widgets::Cell::from(Span::raw(mem_pct_span_text))
-                .style(Style::default().fg(mem_fg)),
-        ])
-        .style(emphasis)
+        let mut cells = Vec::with_capacity(5);
+        if columns.pid {
+            cells.push(
+                ratatui::widgets::Cell::from(pid_span).style(Style::default().fg(Color::DarkGray)),
+            );
+        }
+        cells.push(ratatui::widgets::Cell::from(name_span));
+        if columns.cpu {
+            cells.push(
+                ratatui::widgets::Cell::from(Span::raw(cpu_span_text))
+                    .style(Style::default().fg(cpu_fg)),
+            );
+        }
+        if columns.mem {
+            cells.push(ratatui::widgets::Cell::from(Span::raw(mem_span_text)));
+        }
+        if columns.mem_pct {
+            cells.push(
+                ratatui::widgets::Cell::from(Span::raw(mem_pct_span_text))
+                    .style(Style::default().fg(mem_fg)),
+            );
+        }
+        ratatui::widgets::Row::new(cells).style(emphasis)
     });
 
     // Header with sort indicator
@@ -325,16 +409,30 @@ pub fn draw_top_processes(f: &mut ratatui::Frame<'_>, area: Rect, params: Proces
         ProcSortBy::MemDesc => "Mem •",
         _ => "Mem",
     };
-    let header = ratatui::widgets::Row::new(vec!["PID", "Name", cpu_hdr, mem_hdr, "Mem %"]).style(
+    let mut header_cells = Vec::with_capacity(5);
+    if columns.pid {
+        header_cells.push("PID");
+    }
+    header_cells.push("Name");
+    if columns.cpu {
+        header_cells.push(cpu_hdr);
+    }
+    if columns.mem {
+        header_cells.push(mem_hdr);
+    }
+    if columns.mem_pct {
+        header_cells.push("Mem %");
+    }
+    let header = ratatui::widgets::Row::new(header_cells).style(
         Style::default()
             .fg(Color::Cyan)
             .add_modifier(Modifier::BOLD),
     );
 
     // Render table inside content area (no borders here; outer block already drawn)
-    let table = Table::new(rows_iter, COLS.to_vec())
+    let table = Table::new(rows_iter, columns.constraints())
         .header(header)
-        .column_spacing(1);
+        .column_spacing(COL_SPACING);
     f.render_widget(table, content);
 
     // Draw tooltip if a process is selected
@@ -546,15 +644,24 @@ pub fn processes_handle_mouse(
         && mouse.column < header_area.x + header_area.width;
 
     if inside_header && matches!(mouse.kind, MouseEventKind::Down(MouseButton::Left)) {
-        // Split header into the same columns
+        // Split the header the same way the draw path did, so a click lands on the
+        // column actually on screen even when PID has been dropped.
+        let columns = ProcColumns::for_width(header_area.width);
         let cols = Layout::default()
             .direction(Direction::Horizontal)
-            .constraints(COLS.to_vec())
+            .constraints(columns.constraints())
+            .spacing(COL_SPACING) // must match Table::column_spacing in the draw path
             .split(header_area);
-        if mouse.column >= cols[2].x && mouse.column < cols[2].x + cols[2].width {
+        if let Some(cpu) = columns.cpu_index().map(|i| cols[i])
+            && mouse.column >= cpu.x
+            && mouse.column < cpu.x + cpu.width
+        {
             return Some(ProcSortBy::CpuDesc);
         }
-        if mouse.column >= cols[3].x && mouse.column < cols[3].x + cols[3].width {
+        if let Some(mem) = columns.mem_index().map(|i| cols[i])
+            && mouse.column >= mem.x
+            && mouse.column < mem.x + mem.width
+        {
             return Some(ProcSortBy::MemDesc);
         }
     }
@@ -646,15 +753,24 @@ pub fn processes_handle_mouse_with_selection(params: ProcessMouseParams) -> Opti
         && params.mouse.column < header_area.x + header_area.width;
 
     if inside_header && matches!(params.mouse.kind, MouseEventKind::Down(MouseButton::Left)) {
-        // Split header into the same columns
+        // Split the header the same way the draw path did, so a click lands on the
+        // column actually on screen even when PID has been dropped.
+        let columns = ProcColumns::for_width(header_area.width);
         let cols = Layout::default()
             .direction(Direction::Horizontal)
-            .constraints(COLS.to_vec())
+            .constraints(columns.constraints())
+            .spacing(COL_SPACING) // must match Table::column_spacing in the draw path
             .split(header_area);
-        if params.mouse.column >= cols[2].x && params.mouse.column < cols[2].x + cols[2].width {
+        if let Some(cpu) = columns.cpu_index().map(|i| cols[i])
+            && params.mouse.column >= cpu.x
+            && params.mouse.column < cpu.x + cpu.width
+        {
             return Some(ProcSortBy::CpuDesc);
         }
-        if params.mouse.column >= cols[3].x && params.mouse.column < cols[3].x + cols[3].width {
+        if let Some(mem) = columns.mem_index().map(|i| cols[i])
+            && params.mouse.column >= mem.x
+            && params.mouse.column < mem.x + mem.width
+        {
             return Some(ProcSortBy::MemDesc);
         }
     }
@@ -691,3 +807,258 @@ pub fn processes_handle_mouse_with_selection(params: ProcessMouseParams) -> Opti
     );
     None
 }
+
+#[cfg(test)]
+mod column_tests {
+    use super::*;
+    use ratatui::layout::{Direction, Layout, Rect};
+
+    fn name_width(w: u16) -> u16 {
+        let c = ProcColumns::for_width(w);
+        let rects = Layout::default()
+            .direction(Direction::Horizontal)
+            .constraints(c.constraints())
+            .spacing(COL_SPACING)
+            .split(Rect::new(0, 0, w, 1));
+        rects[usize::from(c.pid)].width
+    }
+
+    /// The complaint this fixes: on a narrow pane the Name column was the first thing to
+    /// disappear, leaving a table of numbers with nothing to identify the process. Name
+    /// must now be the last column standing, at every width that can render anything.
+    #[test]
+    fn name_is_never_the_column_that_gets_dropped() {
+        for width in NAME_MIN_W..=200u16 {
+            assert!(
+                name_width(width) >= 1,
+                "width {width}: Name was squeezed to nothing"
+            );
+        }
+    }
+
+    /// Columns are shed in reverse priority order, so a narrower pane can never show a
+    /// column that a wider one hid.
+    #[test]
+    fn columns_are_shed_in_priority_order() {
+        for width in 0..=200u16 {
+            let c = ProcColumns::for_width(width);
+            assert!(!c.mem_pct || c.pid, "width {width}: Mem % outlived PID");
+            assert!(!c.pid || c.mem, "width {width}: PID outlived Mem");
+            assert!(!c.mem || c.cpu, "width {width}: Mem outlived CPU %");
+        }
+    }
+
+    /// Columns come back as the pane widens and never flap.
+    #[test]
+    fn columns_are_monotonic_in_width() {
+        let mut prev = ProcColumns::for_width(0);
+        for width in 1..=200u16 {
+            let c = ProcColumns::for_width(width);
+            for (was, now, name) in [
+                (prev.cpu, c.cpu, "CPU %"),
+                (prev.mem, c.mem, "Mem"),
+                (prev.pid, c.pid, "PID"),
+                (prev.mem_pct, c.mem_pct, "Mem %"),
+            ] {
+                assert!(!was || now, "width {width}: {name} vanished as it widened");
+            }
+            prev = c;
+        }
+    }
+
+    /// The tiers, from a comfortable pane down to a very narrow one.
+    #[test]
+    fn narrow_panes_shed_columns_in_order() {
+        let full = ProcColumns::for_width(48);
+        assert_eq!(full.constraints().len(), 5);
+        assert!(full.pid && full.cpu && full.mem && full.mem_pct);
+
+        // Mem % goes first.
+        let c = ProcColumns::for_width(45);
+        assert!(c.pid && c.mem && !c.mem_pct);
+
+        // Then PID.
+        let c = ProcColumns::for_width(35);
+        assert!(!c.pid && c.cpu && c.mem);
+
+        // Then Mem, leaving the name and its CPU load.
+        let c = ProcColumns::for_width(20);
+        assert!(!c.mem && c.cpu);
+        assert_eq!(c.constraints().len(), 2);
+
+        // At the floor, just the name.
+        let c = ProcColumns::for_width(10);
+        assert!(!c.cpu && !c.mem);
+        assert_eq!(c.constraints().len(), 1);
+    }
+
+    /// Regression guard for the old behaviour: a 130-column terminal gives the process
+    /// pane ~48 columns, and every column still fits there.
+    #[test]
+    fn a_wide_terminal_keeps_the_full_table() {
+        assert_eq!(ProcColumns::for_width(48).constraints().len(), 5);
+    }
+
+    /// Sort clicks are resolved by index, so those indices must track the columns that
+    /// are actually rendered — otherwise clicking "CPU %" would sort by Mem.
+    #[test]
+    fn sort_indices_follow_the_rendered_columns() {
+        let wide = ProcColumns::for_width(48);
+        assert_eq!(wide.cpu_index(), Some(2)); // PID, Name, CPU %
+        assert_eq!(wide.mem_index(), Some(3));
+
+        let narrow = ProcColumns::for_width(35);
+        assert_eq!(narrow.cpu_index(), Some(1)); // Name, CPU %
+        assert_eq!(narrow.mem_index(), Some(2));
+
+        // A column that is not rendered has no index to click.
+        let tiny = ProcColumns::for_width(10);
+        assert_eq!(tiny.cpu_index(), None);
+        assert_eq!(tiny.mem_index(), None);
+
+        // Whatever the width, any index returned is inside the rendered set.
+        for width in 0..=200u16 {
+            let c = ProcColumns::for_width(width);
+            let n = c.constraints().len();
+            for i in [c.cpu_index(), c.mem_index()].into_iter().flatten() {
+                assert!(i < n, "width {width}: index {i} outside {n} columns");
+            }
+        }
+    }
+
+    /// Name takes the slack, so it grows with the pane instead of being pinned to a
+    /// percentage that the fixed columns can crush.
+    #[test]
+    fn name_absorbs_the_leftover_width() {
+        assert!(
+            name_width(80) > name_width(60),
+            "Name did not grow with the pane"
+        );
+    }
+}
+
+#[cfg(test)]
+mod click_tests {
+    use super::*;
+    use crossterm::event::{KeyModifiers, MouseButton, MouseEvent, MouseEventKind};
+    use ratatui::Terminal;
+    use ratatui::backend::TestBackend;
+    use ratatui::layout::Rect;
+    use socktop_connector::{Metrics, ProcessInfo};
+
+    fn metrics() -> Metrics {
+        Metrics {
+            cpu_total: 0.0,
+            cpu_per_core: vec![],
+            mem_total: 32_000_000_000,
+            mem_used: 0,
+            swap_total: 0,
+            swap_used: 0,
+            hostname: "t".into(),
+            cpu_temp_c: None,
+            disks: vec![],
+            networks: vec![],
+            top_processes: vec![ProcessInfo {
+                pid: 4242,
+                name: "some-process".into(),
+                cpu_usage: 1.5,
+                mem_bytes: 1_000_000,
+            }],
+            gpus: None,
+            process_count: Some(1),
+        }
+    }
+
+    /// Renders the pane and returns its header row as text.
+    fn header_row(width: u16) -> String {
+        let m = metrics();
+        let mut cache = Vec::new();
+        let peak = rebuild_row_cache(&m, &mut cache);
+        let idxs = [0usize];
+        let mut terminal = Terminal::new(TestBackend::new(width, 8)).unwrap();
+        terminal
+            .draw(|f| {
+                draw_top_processes(
+                    f,
+                    Rect::new(0, 0, width, 8),
+                    ProcessDisplayParams {
+                        metrics: Some(&m),
+                        scroll_offset: 0,
+                        sort_by: ProcSortBy::CpuDesc,
+                        selected_process_pid: None,
+                        selected_process_index: None,
+                        search_query: "",
+                        search_active: false,
+                        filtered_indices: &idxs,
+                        cached_rows: &cache,
+                        peak_cpu: peak,
+                    },
+                )
+            })
+            .unwrap();
+        let buf = terminal.backend().buffer();
+        (0..width)
+            .map(|x| buf[(x, 1)].symbol().to_string())
+            .collect()
+    }
+
+    fn click(width: u16, column: u16) -> Option<ProcSortBy> {
+        let mut scroll = 0usize;
+        let mut drag = None;
+        processes_handle_mouse(
+            &mut scroll,
+            &mut drag,
+            MouseEvent {
+                kind: MouseEventKind::Down(MouseButton::Left),
+                column,
+                row: 1,
+                modifiers: KeyModifiers::NONE,
+            },
+            Rect::new(0, 0, width, 8),
+            1,
+        )
+    }
+
+    /// The hit-test rects are computed by a separate `Layout` call from the one `Table`
+    /// renders with. This walks the rendered header text and clicks each label where it
+    /// actually appears, which catches any drift between the two — including column
+    /// spacing, which the two APIs configure differently.
+    #[test]
+    fn clicking_a_rendered_sort_header_sorts_by_that_column() {
+        for width in [40u16, 50, 60, 80, 120] {
+            let row = header_row(width);
+            let cpu_at = row.find("CPU").map(|i| row[..i].chars().count() as u16);
+            let mem_at = row.find("Mem").map(|i| row[..i].chars().count() as u16);
+
+            if let Some(x) = cpu_at {
+                assert_eq!(
+                    click(width, x),
+                    Some(ProcSortBy::CpuDesc),
+                    "width {width}: clicking the rendered 'CPU %' header at column {x} \
+                     did not sort by CPU (header row: {row:?})"
+                );
+            }
+            if let Some(x) = mem_at {
+                assert_eq!(
+                    click(width, x),
+                    Some(ProcSortBy::MemDesc),
+                    "width {width}: clicking the rendered 'Mem' header at column {x} \
+                     did not sort by Mem (header row: {row:?})"
+                );
+            }
+        }
+    }
+
+    /// Name is what identifies the row, so it must be rendered at every width the pane
+    /// can draw anything at.
+    #[test]
+    fn the_name_column_is_rendered_even_when_narrow() {
+        for width in [30u16, 40, 60, 120] {
+            let row = header_row(width);
+            assert!(
+                row.contains("Name"),
+                "width {width}: no Name column in header {row:?}"
+            );
+        }
+    }
+}

socktop/tests/cli_args.rs

@@ -73,3 +73,36 @@ fn test_tlc_ca_arg_long_and_short_parsed() {
     );
     assert!(text3.contains("Usage:"));
 }
+
+#[test]
+fn test_compact_flag_documented_and_accepted() {
+    let exe = env!("CARGO_BIN_EXE_socktop");
+    let out = Command::new(exe)
+        .args(["--compact", "--help"])
+        .output()
+        .expect("run socktop --compact --help");
+    assert!(
+        out.status.success(),
+        "socktop --compact --help did not succeed"
+    );
+    let text = format!(
+        "{}{}",
+        String::from_utf8_lossy(&out.stdout),
+        String::from_utf8_lossy(&out.stderr)
+    );
+    assert!(
+        text.contains("--compact"),
+        "help text missing --compact\n{text}"
+    );
+
+    // The flag must not be mistaken for the positional URL argument.
+    let out2 = Command::new(exe)
+        .args(["--compact", "--dry-run", "ws://127.0.0.1:3000/ws"])
+        .output()
+        .expect("run socktop --compact --dry-run");
+    assert!(
+        out2.status.success(),
+        "socktop --compact with a URL was rejected: {}",
+        String::from_utf8_lossy(&out2.stderr)
+    );
+}