diff --git a/migrations/20260726100000_add_project_collapsed/down.sql b/migrations/20260726100000_add_project_collapsed/down.sql
new file mode 100644
index 0000000..0f9ea31
--- /dev/null
+++ b/migrations/20260726100000_add_project_collapsed/down.sql
@@ -0,0 +1 @@
+ALTER TABLE projects DROP COLUMN collapsed;
diff --git a/migrations/20260726100000_add_project_collapsed/up.sql b/migrations/20260726100000_add_project_collapsed/up.sql
new file mode 100644
index 0000000..7ebd689
--- /dev/null
+++ b/migrations/20260726100000_add_project_collapsed/up.sql
@@ -0,0 +1,2 @@
+ALTER TABLE projects ADD COLUMN collapsed BOOLEAN NOT NULL DEFAULT FALSE
+    CHECK (collapsed IN (FALSE, TRUE));
diff --git a/src/app.rs b/src/app.rs
index 6d29397..6426042 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -178,7 +178,7 @@ pub(crate) enum Message {
     ProjectNameChanged(String),
     ConfirmProject,
     CancelProject,
-    SelectProject(i32),
+    ToggleProject(i32),
     DeleteProject(i32),
     CreateSession(i32),
     DiscardSession(i32),
@@ -718,20 +718,22 @@ impl App {
                 self.project_name_input.clear();
                 self.error = None;
             }
-            Message::SelectProject(project_id) => {
-                if self.generating {
-                    self.error =
-                        Some("Stop the active generation before changing sessions.".into());
+            // Sidebar-only: collapsing a project leaves the open chat alone.
+            Message::ToggleProject(project_id) => {
+                let Some(item) = self
+                    .projects
+                    .iter_mut()
+                    .find(|item| item.project.id == project_id)
+                else {
                     return Task::none();
+                };
+                let collapsed = !item.project.collapsed;
+                item.project.collapsed = collapsed;
+                if let Some(database) = &mut self.database
+                    && let Err(error) = database.set_project_collapsed(project_id, collapsed)
+                {
+                    self.error = Some(error);
                 }
-                self.remember_project(project_id);
-                self.selected_session = None;
-                self.conversation.clear();
-                self.composer.clear();
-                self.context_used = 0;
-                self.context_limit = self.preferences.context_tokens.max(0) as u32;
-                self.tokens_per_second = None;
-                self.error = None;
             }
             Message::DeleteProject(project_id) => {
                 if self.generating && self.selected_project == Some(project_id) {
diff --git a/src/app/projects.rs b/src/app/projects.rs
index 3d27003..f87de3b 100644
--- a/src/app/projects.rs
+++ b/src/app/projects.rs
@@ -195,6 +195,7 @@ mod tests {
             id,
             name: name.into(),
             path: format!("/tmp/{name}"),
+            collapsed: false,
         }
     }
 
diff --git a/src/app/view.rs b/src/app/view.rs
index d62edd0..29b679b 100644
--- a/src/app/view.rs
+++ b/src/app/view.rs
@@ -155,12 +155,16 @@ impl App {
             projects = projects.push(
                 row![
                     button(
-                        row![icon(ICON_FOLDER, 17), text(&project.name).size(14)]
-                            .spacing(9)
-                            .align_y(Alignment::Center),
+                        row![
+                            text(if project.collapsed { "›" } else { "▾" }).size(12),
+                            icon(ICON_FOLDER, 17),
+                            text(&project.name).size(14)
+                        ]
+                        .spacing(9)
+                        .align_y(Alignment::Center),
                     )
                     .width(Length::Fill)
-                    .on_press(Message::SelectProject(project.id))
+                    .on_press(Message::ToggleProject(project.id))
                     .style(button::text),
                     button(icon(ICON_NEW_SESSION, 15))
                         .on_press(Message::CreateSession(project.id))
@@ -173,6 +177,10 @@ impl App {
                 .align_y(Alignment::Center),
             );
 
+            if project.collapsed {
+                continue;
+            }
+
             for session in item
                 .sessions
                 .iter()
diff --git a/src/database.rs b/src/database.rs
index eaa7c4e..2c49c42 100644
--- a/src/database.rs
+++ b/src/database.rs
@@ -257,6 +257,8 @@ pub struct Project {
     pub id: i32,
     pub name: String,
     pub path: String,
+    /// Sidebar state: hides this project's session rows.
+    pub collapsed: bool,
 }
 
 #[derive(Insertable)]
@@ -536,6 +538,18 @@ impl Database {
             .map_err(|error| error.to_string())
     }
 
+    pub fn set_project_collapsed(
+        &mut self,
+        project_id: i32,
+        collapsed: bool,
+    ) -> Result<(), String> {
+        diesel::update(projects::table.find(project_id))
+            .set(projects::collapsed.eq(collapsed))
+            .execute(&mut self.connection)
+            .map(|_| ())
+            .map_err(|error| error.to_string())
+    }
+
     pub fn delete_project(&mut self, project_id: i32) -> Result<(), String> {
         self.connection
             .transaction(|connection| {
@@ -863,6 +877,9 @@ mod tests {
 
         database.set_sidebar_collapsed(true).unwrap();
         database.set_last_project(Some(project.id)).unwrap();
+        assert!(!loaded[0].project.collapsed);
+        database.set_project_collapsed(project.id, true).unwrap();
+        assert!(database.load_projects().unwrap()[0].project.collapsed);
 
         database.delete_project(project.id).unwrap();
         assert!(database.load_projects().unwrap().is_empty());
diff --git a/src/schema.rs b/src/schema.rs
index 5383906..ec57583 100644
--- a/src/schema.rs
+++ b/src/schema.rs
@@ -15,6 +15,7 @@ diesel::table! {
         id -> Integer,
         name -> Text,
         path -> Text,
+        collapsed -> Bool,
     }
 }