feat: add configurable default shell

refs #196

13 files changed, 133 insertions, 6 deletions

diff --git a/src/app/api.rs b/src/app/api.rs
index ab26f82b..6eb95f03 100644
--- a/src/app/api.rs
+++ b/src/app/api.rs
@@ -637,6 +637,9 @@ impl App {
                     .or_else(|| std::env::current_dir().ok())
                     .unwrap_or_else(|| std::path::PathBuf::from("/"));
                 let (rows, cols) = self.state.estimate_pane_size();
+                let default_shell = self.state.default_shell.clone();
+                let scrollback_limit_bytes = self.state.pane_scrollback_limit_bytes;
+                let host_terminal_theme = self.state.host_terminal_theme;
                 let result = self
                     .state
                     .workspaces
@@ -647,8 +650,9 @@ impl App {
                             rows,
                             cols,
                             cwd,
-                            self.state.pane_scrollback_limit_bytes,
-                            self.state.host_terminal_theme,
+                            scrollback_limit_bytes,
+                            host_terminal_theme,
+                            &default_shell,
                         )
                     });
                 match result {
@@ -1019,6 +1023,9 @@ impl App {
                         )
                     })
                 });
+                let default_shell = self.state.default_shell.clone();
+                let scrollback_limit_bytes = self.state.pane_scrollback_limit_bytes;
+                let host_terminal_theme = self.state.host_terminal_theme;
                 let Some(ws) = self.state.workspaces.get_mut(ws_idx) else {
                     return serde_json::to_string(&ErrorResponse {
                         id: request.id,
@@ -1043,8 +1050,9 @@ impl App {
                     rows,
                     cols,
                     split_cwd,
-                    self.state.pane_scrollback_limit_bytes,
-                    self.state.host_terminal_theme,
+                    scrollback_limit_bytes,
+                    host_terminal_theme,
+                    &default_shell,
                     params.focus,
                 ) {
                     Some(Ok(result)) => result,
diff --git a/src/app/creation.rs b/src/app/creation.rs
index f1638e15..f3d8644e 100644
--- a/src/app/creation.rs
+++ b/src/app/creation.rs
@@ -87,6 +87,7 @@ impl App {
             initial_cwd,
             self.state.pane_scrollback_limit_bytes,
             self.state.host_terminal_theme,
+            &self.state.default_shell,
         )?;
         self.state
             .terminal_runtimes
@@ -118,6 +119,7 @@ impl App {
             cols,
             self.state.pane_scrollback_limit_bytes,
             self.state.host_terminal_theme,
+            &self.state.default_shell,
             self.event_tx.clone(),
             self.render_notify.clone(),
             self.render_dirty.clone(),
diff --git a/src/app/input/mod.rs b/src/app/input/mod.rs
index ad68f9da..4cafc926 100644
--- a/src/app/input/mod.rs
+++ b/src/app/input/mod.rs
@@ -259,6 +259,7 @@ impl AppState {
                 cwd,
                 self.pane_scrollback_limit_bytes,
                 self.host_terminal_theme,
+                &self.default_shell,
             ) {
                 let new_id = new_pane.pane_id;
                 self.terminal_runtimes
diff --git a/src/app/input/navigate.rs b/src/app/input/navigate.rs
index 34d0a342..a2967ca3 100644
--- a/src/app/input/navigate.rs
+++ b/src/app/input/navigate.rs
@@ -1092,6 +1092,7 @@ mod tests {
             80,
             app.state.pane_scrollback_limit_bytes,
             app.state.host_terminal_theme,
+            &app.state.default_shell,
             app.event_tx.clone(),
             app.render_notify.clone(),
             app.render_dirty.clone(),
diff --git a/src/app/mod.rs b/src/app/mod.rs
index 3e8a8b83..ca053ba1 100644
--- a/src/app/mod.rs
+++ b/src/app/mod.rs
@@ -234,6 +234,7 @@ impl App {
                 24,
                 80,
                 config.advanced.scrollback_limit_bytes,
+                &config.terminal.default_shell,
                 event_tx.clone(),
                 render_notify.clone(),
                 render_dirty.clone(),
@@ -412,6 +413,7 @@ impl App {
             prompt_new_tab_name: config.ui.prompt_new_tab_name,
             show_agent_labels_on_pane_borders: config.ui.show_agent_labels_on_pane_borders,
             kitty_graphics_enabled: config.experimental.kitty_graphics,
+            default_shell: config.terminal.default_shell.clone(),
             pane_scrollback_limit_bytes: config.advanced.scrollback_limit_bytes,
             accent: crate::config::parse_color(&config.ui.accent),
             sound: config.ui.sound.clone(),
@@ -891,6 +893,10 @@ impl App {
             self.state.pane_scrollback_limit_bytes = config.advanced.scrollback_limit_bytes;
         }
 
+        if !invalid_section("terminal") {
+            self.state.default_shell = config.terminal.default_shell.clone();
+        }
+
         if !invalid_section("theme") {
             self.state.palette = resolve_palette_with_legacy_accent(config, !invalid_section("ui"));
             self.state.theme_name = config
@@ -1321,7 +1327,7 @@ mod tests {
         std::fs::create_dir_all(path.parent().unwrap()).unwrap();
         std::fs::write(
             &path,
-            "[keys]\nnew_workspace = \"g\"\nprefix = \"ctrl+a\"\n[ui]\nagent_panel_scope = \"current\"\n[ui.toast]\ndelivery = \"herdr\"\n",
+            "[terminal]\ndefault_shell = \"nu\"\n[keys]\nnew_workspace = \"g\"\nprefix = \"ctrl+a\"\n[ui]\nagent_panel_scope = \"current\"\n[ui.toast]\ndelivery = \"herdr\"\n",
         )
         .unwrap();
         std::env::set_var(crate::config::CONFIG_PATH_ENV_VAR, &path);
@@ -1344,6 +1350,7 @@ mod tests {
             app.state.agent_panel_scope,
             state::AgentPanelScope::CurrentWorkspace
         );
+        assert_eq!(app.state.default_shell, "nu");
         assert!(app.state.config_diagnostic.is_none());
         let toast = app.state.toast.as_ref().unwrap();
         assert_eq!(toast.kind, crate::app::state::ToastKind::UpdateInstalled);
diff --git a/src/app/state.rs b/src/app/state.rs
index 746474df..0c38171d 100644
--- a/src/app/state.rs
+++ b/src/app/state.rs
@@ -965,6 +965,7 @@ pub struct AppState {
     pub prompt_new_tab_name: bool,
     pub show_agent_labels_on_pane_borders: bool,
     pub kitty_graphics_enabled: bool,
+    pub default_shell: String,
     pub pane_scrollback_limit_bytes: usize,
     #[allow(dead_code)] // kept for backward compat; palette.accent is the source of truth
     pub accent: Color,
@@ -1211,6 +1212,7 @@ impl AppState {
             prompt_new_tab_name: true,
             show_agent_labels_on_pane_borders: false,
             kitty_graphics_enabled: false,
+            default_shell: String::new(),
             pane_scrollback_limit_bytes: crate::config::DEFAULT_SCROLLBACK_LIMIT_BYTES,
             accent: Color::Cyan,
             sound: SoundConfig {
diff --git a/src/config/io.rs b/src/config/io.rs
index 268a1e8b..07b63d37 100644
--- a/src/config/io.rs
+++ b/src/config/io.rs
@@ -162,6 +162,14 @@ fn load_live_config_from_str(content: &str) -> Result<LoadedConfig, Vec<String>>
     );
     load_live_section(
         table,
+        "terminal",
+        "terminal config",
+        &mut diagnostics,
+        &mut invalid_sections,
+        |section| config.terminal = section,
+    );
+    load_live_section(
+        table,
         "ui",
         "ui config",
         &mut diagnostics,
diff --git a/src/config/model.rs b/src/config/model.rs
index 673eec02..ff3a7b22 100644
--- a/src/config/model.rs
+++ b/src/config/model.rs
@@ -34,6 +34,13 @@ pub struct ToastConfig {
     pub delivery: ToastDelivery,
 }
 
+#[derive(Debug, Default, Deserialize)]
+#[serde(default)]
+pub struct TerminalConfig {
+    /// Executable used for new interactive panes. Empty means SHELL, then /bin/sh.
+    pub default_shell: String,
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Deserialize, Serialize)]
 #[serde(rename_all = "snake_case")]
 pub enum ConfigReloadStatus {
@@ -66,6 +73,7 @@ pub fn validated_sidebar_bounds(min: u16, max: u16) -> Option<(u16, u16)> {
 pub struct Config {
     pub onboarding: Option<bool>,
     pub theme: ThemeConfig,
+    pub terminal: TerminalConfig,
     pub keys: KeysConfig,
     pub ui: UiConfig,
     pub advanced: AdvancedConfig,
@@ -298,6 +306,19 @@ mod tests {
     use super::*;
 
     #[test]
+    fn terminal_default_shell_defaults_empty_and_parses() {
+        let default_config = Config::default();
+        assert!(default_config.terminal.default_shell.is_empty());
+
+        let toml = r#"
+[terminal]
+default_shell = "nu"
+"#;
+        let config: Config = toml::from_str(toml).unwrap();
+        assert_eq!(config.terminal.default_shell, "nu");
+    }
+
+    #[test]
     fn agent_panel_scope_config_parses() {
         let toml = r#"
 [ui]
diff --git a/src/main.rs b/src/main.rs
index c8811328..0814c09e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -75,6 +75,11 @@ const DEFAULT_CONFIG: &str = r##"# herdr configuration
 # red = "#ff6188"
 # green = "#a6e3a1"
 
+[terminal]
+# Executable used for new interactive panes.
+# Empty means $SHELL, then /bin/sh.
+# default_shell = ""
+
 [keys]
 # Prefix key to enter navigate mode (default: "ctrl+b")
 # Examples: "ctrl+b", "f12", "esc", "-"
diff --git a/src/pane.rs b/src/pane.rs
index aba31943..10112f0f 100644
--- a/src/pane.rs
+++ b/src/pane.rs
@@ -250,6 +250,22 @@ fn shutdown_pane_processes(pane_id: PaneId, child_pid: u32) {
     );
 }
 
+fn pane_shell(configured_shell: &str) -> String {
+    pane_shell_from(configured_shell, std::env::var("SHELL").ok())
+}
+
+fn pane_shell_from(configured_shell: &str, env_shell: Option<String>) -> String {
+    let configured_shell = configured_shell.trim();
+    if !configured_shell.is_empty() {
+        return configured_shell.to_string();
+    }
+
+    env_shell
+        .map(|shell| shell.trim().to_string())
+        .filter(|shell| !shell.is_empty())
+        .unwrap_or_else(|| "/bin/sh".into())
+}
+
 impl PaneRuntime {
     pub fn shutdown(self) {
         self.detect_handle.abort();
@@ -267,11 +283,12 @@ impl PaneRuntime {
         cwd: std::path::PathBuf,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         events: mpsc::Sender<AppEvent>,
         render_notify: Arc<Notify>,
         render_dirty: Arc<AtomicBool>,
     ) -> std::io::Result<Self> {
-        let shell = std::env::var("SHELL").unwrap_or_else(|_| "/bin/sh".into());
+        let shell = pane_shell(default_shell);
         let mut cmd = CommandBuilder::new(&shell);
         cmd.cwd(cwd);
         cmd.env(crate::HERDR_ENV_VAR, crate::HERDR_ENV_VALUE);
@@ -1100,6 +1117,28 @@ mod tests {
     }
 
     #[test]
+    fn pane_shell_prefers_configured_shell() {
+        assert_eq!(
+            pane_shell_from("/usr/bin/nu", Some("/bin/bash".to_string())),
+            "/usr/bin/nu"
+        );
+    }
+
+    #[test]
+    fn pane_shell_falls_back_to_shell_env() {
+        assert_eq!(
+            pane_shell_from("", Some("/bin/bash".to_string())),
+            "/bin/bash"
+        );
+    }
+
+    #[test]
+    fn pane_shell_ignores_empty_values() {
+        assert_eq!(pane_shell_from("   ", Some("  ".to_string())), "/bin/sh");
+        assert_eq!(pane_shell_from("", None), "/bin/sh");
+    }
+
+    #[test]
     fn pane_terminal_identity_overrides_outer_terminal_env() {
         let output = capture_shell_output("printf '%s\\n%s\\n' \"$TERM\" \"$COLORTERM\"", &[]);
         assert_eq!(output, "xterm-256color\ntruecolor\n");
diff --git a/src/persist/restore.rs b/src/persist/restore.rs
index 0ac49e80..f558761d 100644
--- a/src/persist/restore.rs
+++ b/src/persist/restore.rs
@@ -21,6 +21,7 @@ pub fn restore(
     rows: u16,
     cols: u16,
     scrollback_limit_bytes: usize,
+    default_shell: &str,
     events: mpsc::Sender<AppEvent>,
     render_notify: Arc<Notify>,
     render_dirty: Arc<AtomicBool>,
@@ -38,6 +39,7 @@ pub fn restore(
             rows,
             cols,
             scrollback_limit_bytes,
+            default_shell,
             events.clone(),
             render_notify.clone(),
             render_dirty.clone(),
@@ -57,6 +59,7 @@ fn restore_workspace(
     rows: u16,
     cols: u16,
     scrollback_limit_bytes: usize,
+    default_shell: &str,
     events: mpsc::Sender<AppEvent>,
     render_notify: Arc<Notify>,
     render_dirty: Arc<AtomicBool>,
@@ -78,6 +81,7 @@ fn restore_workspace(
             rows,
             cols,
             scrollback_limit_bytes,
+            default_shell,
             events.clone(),
             render_notify.clone(),
             render_dirty.clone(),
@@ -123,6 +127,7 @@ fn restore_tab(
     rows: u16,
     cols: u16,
     scrollback_limit_bytes: usize,
+    default_shell: &str,
     events: mpsc::Sender<AppEvent>,
     render_notify: Arc<Notify>,
     render_dirty: Arc<AtomicBool>,
@@ -181,6 +186,7 @@ fn restore_tab(
             cwd.clone(),
             scrollback_limit_bytes,
             crate::terminal_theme::TerminalTheme::default(),
+            default_shell,
             events.clone(),
             render_notify.clone(),
             render_dirty.clone(),
diff --git a/src/workspace.rs b/src/workspace.rs
index 69a83d75..47fa9cf7 100644
--- a/src/workspace.rs
+++ b/src/workspace.rs
@@ -89,6 +89,7 @@ impl Workspace {
         cols: u16,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         events: mpsc::Sender<AppEvent>,
         render_notify: Arc<Notify>,
         render_dirty: Arc<AtomicBool>,
@@ -99,6 +100,7 @@ impl Workspace {
             cols,
             scrollback_limit_bytes,
             host_terminal_theme,
+            default_shell,
             events,
             render_notify,
             render_dirty,
@@ -123,6 +125,7 @@ impl Workspace {
             cols,
             scrollback_limit_bytes,
             host_terminal_theme,
+            "",
             events,
             render_notify,
             render_dirty,
@@ -137,6 +140,7 @@ impl Workspace {
         cols: u16,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         events: mpsc::Sender<AppEvent>,
         render_notify: Arc<Notify>,
         render_dirty: Arc<AtomicBool>,
@@ -163,6 +167,7 @@ impl Workspace {
                 cols,
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
                 events,
                 render_notify,
                 render_dirty,
@@ -223,6 +228,7 @@ impl Workspace {
         cwd: PathBuf,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
     ) -> std::io::Result<(usize, TerminalState, TerminalRuntime)> {
         self.create_tab_with_runtime(
             rows,
@@ -230,6 +236,7 @@ impl Workspace {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            default_shell,
             None,
         )
     }
@@ -241,6 +248,7 @@ impl Workspace {
         cwd: PathBuf,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         argv: Option<&[String]>,
     ) -> std::io::Result<(usize, TerminalState, TerminalRuntime)> {
         let number = self.tabs.len() + 1;
@@ -278,6 +286,7 @@ impl Workspace {
                 cols,
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
                 events,
                 render_notify,
                 render_dirty,
@@ -343,6 +352,7 @@ impl Workspace {
         cwd: Option<PathBuf>,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
     ) -> std::io::Result<crate::workspace::tab::NewPane> {
         let new_pane = self
             .active_tab_mut()
@@ -354,6 +364,7 @@ impl Workspace {
                 cwd,
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
             )?;
         self.register_new_pane(new_pane.pane_id);
         Ok(new_pane)
@@ -368,6 +379,7 @@ impl Workspace {
         cwd: Option<PathBuf>,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         focus_new_pane: bool,
     ) -> Option<std::io::Result<(usize, crate::workspace::tab::NewPane)>> {
         self.split_pane_with_runtime(
@@ -378,6 +390,7 @@ impl Workspace {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            default_shell,
             focus_new_pane,
             None,
         )
@@ -404,6 +417,7 @@ impl Workspace {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            "",
             focus_new_pane,
             Some(argv),
         )
@@ -419,6 +433,7 @@ impl Workspace {
         cwd: Option<PathBuf>,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         focus_new_pane: bool,
         argv: Option<&[String]>,
     ) -> Option<std::io::Result<(usize, crate::workspace::tab::NewPane)>> {
@@ -444,6 +459,7 @@ impl Workspace {
                 cwd,
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
             )
         } {
             Ok(new_pane) => new_pane,
diff --git a/src/workspace/tab.rs b/src/workspace/tab.rs
index 943a45a0..3616b95c 100644
--- a/src/workspace/tab.rs
+++ b/src/workspace/tab.rs
@@ -53,6 +53,7 @@ impl Tab {
         cols: u16,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         events: mpsc::Sender<AppEvent>,
         render_notify: Arc<Notify>,
         render_dirty: Arc<AtomicBool>,
@@ -64,6 +65,7 @@ impl Tab {
             cols,
             scrollback_limit_bytes,
             host_terminal_theme,
+            default_shell,
             events,
             render_notify,
             render_dirty,
@@ -90,6 +92,7 @@ impl Tab {
             cols,
             scrollback_limit_bytes,
             host_terminal_theme,
+            "",
             events,
             render_notify,
             render_dirty,
@@ -105,6 +108,7 @@ impl Tab {
         cols: u16,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         events: mpsc::Sender<AppEvent>,
         render_notify: Arc<Notify>,
         render_dirty: Arc<AtomicBool>,
@@ -132,6 +136,7 @@ impl Tab {
                 initial_cwd.clone(),
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
                 events.clone(),
                 render_notify.clone(),
                 render_dirty.clone(),
@@ -189,6 +194,7 @@ impl Tab {
         cwd: Option<PathBuf>,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
     ) -> std::io::Result<NewPane> {
         self.split_focused_with_runtime(
             direction,
@@ -197,6 +203,7 @@ impl Tab {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            default_shell,
             None,
         )
     }
@@ -219,6 +226,7 @@ impl Tab {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            "",
             Some(SplitCommand::Shell { command, extra_env }),
         )
     }
@@ -240,6 +248,7 @@ impl Tab {
             cwd,
             scrollback_limit_bytes,
             host_terminal_theme,
+            "",
             Some(SplitCommand::Argv { argv }),
         )
     }
@@ -252,6 +261,7 @@ impl Tab {
         cwd: Option<PathBuf>,
         scrollback_limit_bytes: usize,
         host_terminal_theme: crate::terminal_theme::TerminalTheme,
+        default_shell: &str,
         command: Option<SplitCommand<'_>>,
     ) -> std::io::Result<NewPane> {
         let previous_focus = self.layout.focused();
@@ -298,6 +308,7 @@ impl Tab {
                 actual_cwd.clone(),
                 scrollback_limit_bytes,
                 host_terminal_theme,
+                default_shell,
                 self.events.clone(),
                 self.render_notify.clone(),
                 self.render_dirty.clone(),