feat: configure mobile width threshold (#317)

7 files changed, 68 insertions, 6 deletions

diff --git a/src/app/mod.rs b/src/app/mod.rs
index cad09a71..12fb704e 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -478,6 +478,7 @@ impl App {
             sidebar_width,
             sidebar_min_width,
             sidebar_max_width,
+            mobile_width_threshold: config.ui.mobile_width_threshold,
             sidebar_width_source,
             sidebar_width_auto: false,
             sidebar_collapsed: false,
@@ -1079,6 +1080,7 @@ impl App {
                 }
                 self.state.sidebar_min_width = config.ui.sidebar_min_width;
                 self.state.sidebar_max_width = config.ui.sidebar_max_width;
+                self.state.mobile_width_threshold = config.ui.mobile_width_threshold;
                 // Re-clamp the live width to the new bounds. No source guard — bounds
                 // always apply, including to widths owned by Persisted or Manual.
                 self.state.sidebar_width = self
@@ -1778,6 +1780,10 @@ mod tests {
         // Default bounds.
         assert_eq!(app.state.sidebar_min_width, 18);
         assert_eq!(app.state.sidebar_max_width, 36);
+        assert_eq!(
+            app.state.mobile_width_threshold,
+            crate::config::DEFAULT_MOBILE_WIDTH_THRESHOLD
+        );
 
         // Manually set a width and flip the source so the existing
         // sidebar_width-only-when-config-owned guard does NOT update it.
@@ -1818,6 +1824,29 @@ mod tests {
     }
 
     #[test]
+    fn reload_config_updates_mobile_width_threshold() {
+        let _guard = config_env_lock().lock().unwrap();
+        let path = temp_config_path("reload-config-mobile-width-threshold");
+        std::fs::create_dir_all(path.parent().unwrap()).unwrap();
+        std::env::set_var(crate::config::CONFIG_PATH_ENV_VAR, &path);
+
+        let mut app = test_app();
+        assert_eq!(
+            app.state.mobile_width_threshold,
+            crate::config::DEFAULT_MOBILE_WIDTH_THRESHOLD
+        );
+
+        std::fs::write(&path, "[ui]\nmobile_width_threshold = 96\n").unwrap();
+        let report = app.reload_config();
+
+        assert_eq!(report.status, crate::config::ConfigReloadStatus::Applied);
+        assert_eq!(app.state.mobile_width_threshold, 96);
+
+        std::env::remove_var(crate::config::CONFIG_PATH_ENV_VAR);
+        let _ = std::fs::remove_dir_all(path.parent().unwrap());
+    }
+
+    #[test]
     fn app_new_falls_back_to_default_bounds_on_inverted_config() {
         let mut config = Config::default();
         config.ui.sidebar_min_width = 50;
diff --git a/src/app/state.rs b/src/app/state.rs
index de1db052..7c47973c 100644
--- a/src/app/state.rs
+++ b/src/app/state.rs
@@ -1119,6 +1119,7 @@ pub struct AppState {
     pub sidebar_width: u16,
     pub sidebar_min_width: u16,
     pub sidebar_max_width: u16,
+    pub mobile_width_threshold: u16,
     pub sidebar_width_source: SidebarWidthSource,
     pub sidebar_width_auto: bool,
     pub sidebar_collapsed: bool,
@@ -1424,6 +1425,7 @@ impl AppState {
             sidebar_width: 26,
             sidebar_min_width: 18,
             sidebar_max_width: 36,
+            mobile_width_threshold: crate::config::DEFAULT_MOBILE_WIDTH_THRESHOLD,
             sidebar_width_source: SidebarWidthSource::ConfigDefault,
             sidebar_width_auto: false,
             sidebar_collapsed: false,
diff --git a/src/config.rs b/src/config.rs
index d874455e..b4fcf1ef 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -30,6 +30,7 @@ pub(crate) use self::io::upsert_top_level_bool;
 pub const CONFIG_PATH_ENV_VAR: &str = "HERDR_CONFIG_PATH";
 pub const DEFAULT_SCROLLBACK_LIMIT_BYTES: usize = 10_000_000;
 pub const DEFAULT_MOUSE_SCROLL_LINES: usize = 3;
+pub const DEFAULT_MOBILE_WIDTH_THRESHOLD: u16 = 64;
 
 #[cfg(test)]
 pub(crate) fn app_dir_name() -> &'static str {
diff --git a/src/config/model.rs b/src/config/model.rs
index d4830df1..ac304973 100644
--- a/src/config/model.rs
+++ b/src/config/model.rs
@@ -3,8 +3,8 @@ use std::num::NonZeroUsize;
 use serde::{Deserialize, Deserializer, Serialize};
 
 use super::{
-    BindingConfig, CommandKeybindConfig, SoundConfig, ThemeConfig, DEFAULT_MOUSE_SCROLL_LINES,
-    DEFAULT_SCROLLBACK_LIMIT_BYTES,
+    BindingConfig, CommandKeybindConfig, SoundConfig, ThemeConfig, DEFAULT_MOBILE_WIDTH_THRESHOLD,
+    DEFAULT_MOUSE_SCROLL_LINES, DEFAULT_SCROLLBACK_LIMIT_BYTES,
 };
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Deserialize, Serialize, Default)]
@@ -259,6 +259,8 @@ pub struct UiConfig {
     pub sidebar_min_width: u16,
     /// Maximum sidebar width (columns) when expanded. Default: 36.
     pub sidebar_max_width: u16,
+    /// Terminal width at or below which Herdr uses the mobile single-column layout. Default: 64.
+    pub mobile_width_threshold: u16,
     /// Capture mouse input for Herdr's mouse UI. Default: true.
     pub mouse_capture: bool,
     /// Force a full host-terminal redraw when the outer terminal regains focus. Default: true.
@@ -420,6 +422,7 @@ impl Default for UiConfig {
             sidebar_width: 26,
             sidebar_min_width: 18,
             sidebar_max_width: 36,
+            mobile_width_threshold: DEFAULT_MOBILE_WIDTH_THRESHOLD,
             mouse_capture: true,
             redraw_on_focus_gained: true,
             mouse_scroll_lines: None,
@@ -642,15 +645,21 @@ cjk_ime_agents = ["claude", "codex"]
         let default_config = Config::default();
         assert_eq!(default_config.ui.sidebar_min_width, 18);
         assert_eq!(default_config.ui.sidebar_max_width, 36);
+        assert_eq!(
+            default_config.ui.mobile_width_threshold,
+            DEFAULT_MOBILE_WIDTH_THRESHOLD
+        );
 
         let toml = r#"
 [ui]
 sidebar_min_width = 12
 sidebar_max_width = 80
+mobile_width_threshold = 96
 "#;
         let config: Config = toml::from_str(toml).unwrap();
         assert_eq!(config.ui.sidebar_min_width, 12);
         assert_eq!(config.ui.sidebar_max_width, 80);
+        assert_eq!(config.ui.mobile_width_threshold, 96);
     }
 
     #[test]
diff --git a/src/main.rs b/src/main.rs
index 0d42effe..5f20d3a3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -178,6 +178,10 @@ const DEFAULT_CONFIG: &str = r##"# herdr configuration
 # Maximum sidebar width when expanded (columns)
 # sidebar_max_width = 36
 
+# Terminal width at or below which Herdr uses the mobile single-column layout.
+# Increase this for foldables, tablets, or wide phone terminals.
+# mobile_width_threshold = 64
+
 # Capture mouse input for Herdr's mouse UI.
 # Set false to let the terminal handle normal clicks, such as Cmd-clicking URLs.
 # Pane apps like lazygit and btop can still receive mouse when they request it.
diff --git a/src/ui.rs b/src/ui.rs
index 7b45c8c4..78c4b2e7 100644
--- a/src/ui.rs
+++ b/src/ui.rs
@@ -170,7 +170,7 @@ fn compute_view_internal(
     resize_panes: bool,
     cell_size: crate::kitty_graphics::HostCellSize,
 ) {
-    if is_mobile_width(area) {
+    if is_mobile_width(area, app.mobile_width_threshold) {
         compute_mobile_view(app, terminal_runtimes, area, resize_panes, cell_size);
         return;
     }
@@ -544,6 +544,24 @@ mod tests {
     }
 
     #[test]
+    fn configured_mobile_width_threshold_controls_layout_switch() {
+        let mut app = crate::app::state::AppState::test_new();
+        app.workspaces = vec![Workspace::test_new("one")];
+        app.active = Some(0);
+        app.selected = 0;
+        app.mode = Mode::Terminal;
+
+        compute_view(&mut app, Rect::new(0, 0, 80, 20));
+        assert_eq!(app.view.layout, ViewLayout::Desktop);
+
+        app.mobile_width_threshold = 90;
+        compute_view(&mut app, Rect::new(0, 0, 80, 20));
+        assert_eq!(app.view.layout, ViewLayout::Mobile);
+        assert_eq!(app.view.mobile_header_rect, Rect::new(0, 0, 80, 2));
+        assert_eq!(app.view.terminal_area, Rect::new(0, 2, 80, 18));
+    }
+
+    #[test]
     fn product_announcement_renders_above_config_diagnostic() {
         let mut app = crate::app::state::AppState::test_new();
         app.workspaces = vec![Workspace::test_new("one")];
diff --git a/src/ui/mobile.rs b/src/ui/mobile.rs
index 2de79d23..c1dd57b6 100644
--- a/src/ui/mobile.rs
+++ b/src/ui/mobile.rs
@@ -14,7 +14,6 @@ use crate::detect::AgentState;
 use crate::layout::PaneId;
 use crate::terminal::TerminalRuntimeRegistry;
 
-pub(crate) const MOBILE_WIDTH_THRESHOLD: u16 = 64;
 const SWITCH_BUTTON_WIDTH: u16 = 10;
 
 #[derive(Debug, Clone, Copy, Default)]
@@ -42,8 +41,8 @@ pub(crate) enum MobileSwitcherTarget {
     Menu(usize),
 }
 
-pub(crate) fn is_mobile_width(area: Rect) -> bool {
-    area.width > 0 && area.width <= MOBILE_WIDTH_THRESHOLD
+pub(crate) fn is_mobile_width(area: Rect, threshold: u16) -> bool {
+    area.width > 0 && area.width <= threshold
 }
 
 pub(crate) fn compute_mobile_header_hit_areas(_app: &AppState, area: Rect) -> MobileHeaderHitAreas {