feat(zen-mode): add shortlist switcher plugin

Cargo.toml

@@ -2,7 +2,13 @@
 resolver = "3"
 # Rust plugins must be listed here. Plugins in other languages live under
 # plugins/ too but are not cargo members.
-members = ["crates/herdr-client", "plugins/command-palette", "plugins/git-glance", "plugins/project-runner"]
+members = [
+    "crates/herdr-client",
+    "plugins/command-palette",
+    "plugins/git-glance",
+    "plugins/project-runner",
+    "plugins/zen-mode",
+]
 
 [workspace.package]
 edition = "2024"

README.md

@@ -150,3 +150,51 @@ description = "run project script"
 
 `↑`/`↓` or `ctrl-p`/`ctrl-n` move · `enter` runs in a new tab · `ctrl-v` split
 right · `ctrl-x` split down · `esc` closes · `ctrl-u` clears.
+
+## Zen mode (`plugins/zen-mode`)
+
+Switcher shortlist for focused work: pick up to **two workspaces** and **three
+tabs** in each, then toggle zen on to focus into that set. Deactivating keeps
+the selection. Unselected tabs stay open and visible in Herdr (this is a
+switcher, not host chrome filtering). Missing saved workspaces/tabs toast via
+`notification.show` and are skipped on activate.
+
+State: `~/.local/state/herdr/plugins/jacob.zen-mode/zen.toml`.
+
+### Keybinding
+
+One binding opens the switcher. Activate or deactivate zen from inside it with
+`z` (no second shortcut required). `jacob.zen-mode.toggle` remains available
+from the command palette if you want it without a keybind.
+
+```toml
+[[keys.command]]
+key = "cmd+shift+z"
+type = "plugin_action"
+command = "jacob.zen-mode.configure"
+description = "zen mode"
+```
+
+### Configure keys
+
+`↑`/`↓` or `j`/`k` move · `enter` focuses the selected tab (or workspace) and
+closes · `z` toggles zen on/off (on focuses a shortlist tab and closes; off
+stays in the popup) · `r` replace · `a` add workspace · `t` add tab · `d`
+remove · `esc` close. In pickers, type to filter · `enter` selects · `esc`
+backs out. Tabs and workspaces show agent status (`● working`, `blocked`,
+`done`, `idle`) when Herdr reports one.
+
+### Notes / limits
+
+- Zen does **not** hide unselected workspaces or tabs in Herdr’s sidebar or tab
+  bar. It only remembers a shortlist, toggles focus into it, and lets you jump
+  to a picked tab from configure.
+- Collapsing the left sidebar is a Herdr UI action, not something this plugin
+  can do on toggle. There is no sidebar collapse API for plugins today.
+  - Toggle manually: default `prefix+b` (`toggle_sidebar` in
+    `~/.config/herdr/config.toml`).
+  - Or start collapsed on next launch:
+    ```toml
+    sidebar_start_collapsed = true
+    sidebar_collapsed_mode = "hidden"   # or "compact" for a thin rail
+    ```

plugins/zen-mode/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "zen-mode"
+version = "0.1.0"
+edition.workspace = true
+
+[dependencies]
+herdr-client.workspace = true
+ratatui.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+toml.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true

plugins/zen-mode/herdr-plugin.toml

@@ -0,0 +1,29 @@
+id = "jacob.zen-mode"
+name = "Zen Mode"
+version = "0.1.0"
+min_herdr_version = "0.9.0"
+description = "Switcher shortlist: up to two workspaces and three tabs each; toggle focus among the selection"
+platforms = ["macos", "linux"]
+
+[[build]]
+command = ["cargo", "build", "--release", "--target-dir", "target"]
+
+[[actions]]
+id = "configure"
+title = "Configure zen mode"
+contexts = ["workspace"]
+command = ["sh", "-c", "exec \"$HERDR_BIN_PATH\" plugin pane open --plugin jacob.zen-mode --entrypoint configure"]
+
+[[actions]]
+id = "toggle"
+title = "Toggle zen mode"
+contexts = ["workspace"]
+command = ["target/release/zen-mode", "toggle"]
+
+[[panes]]
+id = "configure"
+title = "Zen Mode"
+placement = "popup"
+width = "60%"
+height = "50%"
+command = ["target/release/zen-mode", "ui"]

plugins/zen-mode/src/activate.rs

@@ -0,0 +1,134 @@
+//! Toggle zen on/off: resolve the shortlist, toast gaps, focus a tab.
+
+use herdr_client::Api;
+use serde_json::json;
+
+use crate::resolve::{self, Resolution};
+use crate::state::ZenState;
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ToggleOutcome {
+    pub active: bool,
+    pub resolution: Resolution,
+}
+
+/// Flip `active`, persist, and when turning on focus the best available tab.
+pub fn toggle(api: &impl Api, state: &mut ZenState, current_tab_id: Option<&str>) -> Result<ToggleOutcome, String> {
+    if state.active {
+        state.active = false;
+        return Ok(ToggleOutcome {
+            active: false,
+            resolution: Resolution { available_tab_ids: Vec::new(), missing: Vec::new(), focus_tab_id: None },
+        });
+    }
+
+    state.active = true;
+    let workspaces = api.workspace_list().map_err(|err| err.to_string())?;
+    let tabs = api.tab_list().map_err(|err| err.to_string())?;
+    let resolution = resolve::resolve(state, &workspaces, &tabs, current_tab_id);
+
+    for message in &resolution.missing {
+        notify(api, "Zen mode", message)?;
+    }
+    if resolution.available_tab_ids.is_empty() {
+        notify(api, "Zen mode", "no selected tabs available")?;
+    } else if let Some(tab_id) = &resolution.focus_tab_id {
+        api.request("tab.focus", json!({ "tab_id": tab_id })).map_err(|err| err.to_string())?;
+    }
+
+    Ok(ToggleOutcome { active: true, resolution })
+}
+
+pub fn notify(api: &impl Api, title: &str, body: &str) -> Result<(), String> {
+    api.request(
+        "notification.show",
+        json!({
+            "title": title,
+            "body": body,
+            "sound": "none",
+        }),
+    )
+    .map_err(|err| err.to_string())?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::state::WorkspaceSlot;
+    use crate::testing::FakeApi;
+    use serde_json::json;
+
+    fn live_lists() -> FakeApi {
+        FakeApi::new()
+            .ok(
+                "workspace.list",
+                json!({
+                    "workspaces": [
+                        {"workspace_id": "w1", "number": 1, "label": "Core", "focused": true, "agent_status": "idle"},
+                        {"workspace_id": "w2", "number": 2, "label": "Docs", "focused": false, "agent_status": "idle"}
+                    ]
+                }),
+            )
+            .ok(
+                "tab.list",
+                json!({
+                    "tabs": [
+                        {"tab_id": "w1:t1", "workspace_id": "w1", "number": 1, "label": "Claude", "focused": true, "agent_status": "idle"},
+                        {"tab_id": "w1:t2", "workspace_id": "w1", "number": 2, "label": "Logs", "focused": false, "agent_status": "idle"},
+                        {"tab_id": "w2:t1", "workspace_id": "w2", "number": 1, "label": "Write", "focused": false, "agent_status": "idle"}
+                    ]
+                }),
+            )
+            .ok("tab.focus", json!({}))
+            .ok("notification.show", json!({}))
+    }
+
+    #[test]
+    fn activate_focuses_and_toasts_missing_without_closing() {
+        let api = live_lists();
+        let mut state = ZenState {
+            active: false,
+            workspaces: vec![
+                WorkspaceSlot { workspace_id: "w1".into(), tab_ids: vec!["w1:t1".into(), "w1:t9".into()] },
+                WorkspaceSlot { workspace_id: "w9".into(), tab_ids: vec!["w9:t1".into()] },
+            ],
+        };
+        let outcome = toggle(&api, &mut state, Some("w1:t1")).unwrap();
+        assert!(outcome.active);
+        assert!(state.active);
+        assert_eq!(outcome.resolution.focus_tab_id.as_deref(), Some("w1:t1"));
+        assert_eq!(state.workspaces[0].tab_ids, ["w1:t1", "w1:t9"]);
+
+        let methods: Vec<_> = api.calls().into_iter().map(|(method, _)| method).collect();
+        assert!(methods.contains(&"tab.focus".to_string()));
+        assert!(methods.contains(&"notification.show".to_string()));
+        assert!(!methods.iter().any(|method| method.contains("close") || method.contains("move")));
+    }
+
+    #[test]
+    fn deactivate_clears_active_and_keeps_selection() {
+        let api = FakeApi::new();
+        let mut state = ZenState {
+            active: true,
+            workspaces: vec![WorkspaceSlot { workspace_id: "w1".into(), tab_ids: vec!["w1:t1".into()] }],
+        };
+        let outcome = toggle(&api, &mut state, None).unwrap();
+        assert!(!outcome.active);
+        assert!(!state.active);
+        assert_eq!(state.workspaces[0].tab_ids, ["w1:t1"]);
+        assert!(api.calls().is_empty());
+    }
+
+    #[test]
+    fn activate_with_empty_shortlist_notifies_and_skips_focus() {
+        let api = live_lists();
+        let mut state = ZenState::default();
+        let outcome = toggle(&api, &mut state, None).unwrap();
+        assert!(outcome.active);
+        assert!(outcome.resolution.focus_tab_id.is_none());
+        let methods: Vec<_> = api.calls().into_iter().map(|(method, _)| method).collect();
+        assert!(methods.contains(&"notification.show".to_string()));
+        assert!(!methods.contains(&"tab.focus".to_string()));
+    }
+}