diff --git a/src/app.rs b/src/app.rs
index 6cea50b1..d324155f 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -20,6 +20,7 @@ use crate::theme::Theme;
 /// needs to hand back to the main thread for status / conflict / budget
 /// post-processing. All fields are owned values so the struct is `Send`
 /// and can be returned across `tokio::task::spawn_blocking`.
+#[derive(Default)]
 pub struct RefreshIoOutput {
     pub sessions: Vec<AgentSession>,
     pub new_pids: Vec<u32>,
@@ -900,6 +901,10 @@ pub struct App {
     /// duplicates each tick — the next tick reuses the existing
     /// worker's eventual result. Cleared once the result is recv'd.
     pub refresh_in_flight: bool,
+    /// The I/O-heavy pass a refresh runs. Always [`do_refresh_io`] in
+    /// production; a seam so tests can exercise the scheduling and channel
+    /// plumbing without scanning the host's real `~/.claude`.
+    pub(crate) refresh_worker: fn(Vec<AgentSession>) -> RefreshIoOutput,
     pub table_state: TableState,
     pub should_quit: bool,
     pub status_msg: String,
@@ -1061,13 +1066,16 @@ impl App {
         self.replace_data(new_data);
     }
 
+    /// No session scan, no ledger read, no background thread — only the
+    /// parked-session file is read. Use [`App::with_host_state`] for a real run.
     pub fn new() -> Self {
         let (refresh_tx, refresh_rx) = tokio::sync::mpsc::unbounded_channel();
-        let mut app = Self {
+        Self {
             data: Arc::new(RwLock::new(Arc::new(AppData::default()))),
             refresh_tx,
             refresh_rx,
             refresh_in_flight: false,
+            refresh_worker: do_refresh_io,
             table_state: TableState::default(),
             should_quit: false,
             status_msg: String::new(),
@@ -1133,7 +1141,13 @@ impl App {
             idle_mode_active: false,
             idle_tasks_launched: Vec::new(),
             idle_report: Vec::new(),
-        };
+        }
+    }
+
+    /// Construct and populate from the host: the session scan, ledger
+    /// rollups, and background usage scan a real run needs.
+    pub fn with_host_state() -> Self {
+        let mut app = Self::new();
         app.refresh();
         // Seed rollups from any rows already in the CSV — instant via
         // the in-memory ledger cache. Don't block startup on
@@ -1169,7 +1183,7 @@ impl App {
         // `do_refresh_io` on a worker and routes the result through a
         // channel, then calls `apply_refresh_output` on the main thread.
         let prev_sessions = self.data_snapshot().sessions.clone();
-        let out = do_refresh_io(prev_sessions);
+        let out = (self.refresh_worker)(prev_sessions);
         self.apply_refresh_output(out, tick_start);
     }
 
@@ -1211,17 +1225,18 @@ impl App {
         // in a runtime context (tests, one-shot CLI), fall back to a
         // synchronous refresh on the calling thread.
         let prev_sessions = self.data_snapshot().sessions.clone();
+        let worker = self.refresh_worker;
         if let Ok(handle) = tokio::runtime::Handle::try_current() {
             let tx = self.refresh_tx.clone();
             handle.spawn_blocking(move || {
-                let out = do_refresh_io(prev_sessions);
+                let out = worker(prev_sessions);
                 let _ = tx.send(out);
             });
             self.refresh_in_flight = true;
         } else if !applied_any {
             // No runtime AND we didn't already apply a result this tick:
             // run synchronously so the caller still gets fresh data.
-            let out = do_refresh_io(prev_sessions);
+            let out = worker(prev_sessions);
             self.apply_refresh_output(out, std::time::Instant::now());
             applied_any = true;
         }
@@ -4148,19 +4163,9 @@ mod tests {
         app
     }
 
-    /// Build an App with empty AppData, bypassing the host-side
-    /// session discovery that `App::new()` does in its constructor.
-    /// The data-helper tests below assert on the post-replace state
-    /// directly, so we don't want real sessions leaking in.
-    fn app_with_empty_data() -> App {
-        let app = App::new();
-        app.replace_data(AppData::default());
-        app
-    }
-
     #[test]
     fn data_snapshot_returns_empty_appdata_after_clear() {
-        let app = app_with_empty_data();
+        let app = App::new();
         let snap = app.data_snapshot();
         assert!(snap.sessions.is_empty());
         assert_eq!(snap.ledger_today.msg_count, 0);
@@ -4170,7 +4175,7 @@ mod tests {
 
     #[test]
     fn replace_data_swaps_atomically_and_takes_effect_for_next_snapshot() {
-        let app = app_with_empty_data();
+        let app = App::new();
         let snap_before = app.data_snapshot();
         assert!(snap_before.sessions.is_empty());
 
@@ -4202,7 +4207,7 @@ mod tests {
 
     #[test]
     fn modify_data_mutates_in_place_and_visible_to_subsequent_snapshot() {
-        let app = app_with_empty_data();
+        let app = App::new();
         app.modify_data(|d| {
             d.ledger_week.fresh_input = 12345;
             d.sessions.push(make_session(
@@ -4253,51 +4258,45 @@ mod tests {
 
     #[test]
     fn refresh_nonblocking_falls_back_to_sync_when_no_runtime() {
-        // No tokio runtime is active in unit tests by default — the
-        // function must therefore run `do_refresh_io` synchronously
-        // and return `true` (work was applied) with refresh_in_flight
-        // cleared, rather than dispatching to a worker that never runs.
-        let mut app = app_with_empty_data();
+        // With no runtime the work must run on the calling thread and be
+        // applied before the call returns, not dispatched to a worker that
+        // never runs.
+        let mut app = App::new();
+        app.refresh_worker = |_| RefreshIoOutput::default();
         assert!(app.refresh_nonblocking());
         assert!(!app.refresh_in_flight);
     }
 
     #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
     async fn refresh_nonblocking_kicks_worker_under_runtime() {
-        // With a multi-threaded tokio runtime the first call kicks
-        // a `do_refresh_io` worker onto the blocking pool. Subsequent
-        // calls return false until the worker sends its result back
-        // through the channel; once the result is applied,
-        // refresh_nonblocking returns true. We poll on the return
-        // value rather than `refresh_in_flight` because each call
-        // also schedules the NEXT worker, so the flag is true on
+        // We poll the return value rather than `refresh_in_flight` because
+        // each call also schedules the NEXT worker, so the flag is true on
         // exit even after a successful drain.
-        //
-        // Note: `do_refresh_io` reads the real host filesystem
-        // (~/.claude/sessions, ~/.claude/projects). On a heavy box
-        // the cold pass can take seconds; the 60 s deadline is
-        // generous to keep this test reliable on slow CI/sandboxes.
-        let mut app = app_with_empty_data();
+        let mut app = App::new();
+        app.refresh_worker = |_| RefreshIoOutput::default();
+
         let kicked = app.refresh_nonblocking();
         assert!(!kicked, "first call only schedules; nothing applied yet");
         assert!(app.refresh_in_flight, "worker must be scheduled");
 
-        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(60);
+        // A hang guard, not a performance bound: the worker is in-memory.
+        let deadline = std::time::Instant::now() + std::time::Duration::from_secs(5);
         loop {
             tokio::task::yield_now().await;
             if app.refresh_nonblocking() {
                 break;
             }
-            if std::time::Instant::now() >= deadline {
-                panic!("refresh worker did not complete within 60 s");
-            }
-            tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+            assert!(
+                std::time::Instant::now() < deadline,
+                "worker result never arrived through the channel"
+            );
+            tokio::time::sleep(std::time::Duration::from_millis(5)).await;
         }
     }
 
     #[test]
     fn with_sessions_preserves_ledger_fields() {
-        let app = app_with_empty_data();
+        let app = App::new();
         app.modify_data(|d| {
             d.ledger_month.cost_usd = 999.99;
         });
diff --git a/src/commands.rs b/src/commands.rs
index 95cc6fb2..f52948fd 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -914,10 +914,22 @@ pub(crate) fn run_clean(
         .map(std::path::PathBuf::from)
         .unwrap_or_else(|| std::path::PathBuf::from("/tmp"));
 
-    // Collect active PIDs to avoid deleting live sessions
-    let active_pids: std::collections::HashSet<u32> = {
-        let app = App::new();
-        app.data_snapshot().sessions.iter().map(|s| s.pid).collect()
+    // One host scan for both liveness questions. The `--finished` filter below
+    // runs per JSONL file, so asking it to build its own App cost a full scan
+    // and a `ps` fork for every file in `~/.claude/projects`.
+    let (active_pids, active_jsonl): (
+        std::collections::HashSet<u32>,
+        std::collections::HashSet<std::path::PathBuf>,
+    ) = {
+        let app = App::with_host_state();
+        let snap = app.data_snapshot();
+        (
+            snap.sessions.iter().map(|s| s.pid).collect(),
+            snap.sessions
+                .iter()
+                .filter_map(|s| s.jsonl_path.clone())
+                .collect(),
+        )
     };
 
     let mut removed_sessions = 0u64;
@@ -999,18 +1011,8 @@ pub(crate) fn run_clean(
                 }
 
                 // If --finished only, skip JSONL files whose corresponding session is still active
-                if finished_only {
-                    // Check if any active session is using this JSONL
-                    let app = App::new();
-                    let is_active = app.data_snapshot().sessions.iter().any(|s| {
-                        s.jsonl_path
-                            .as_ref()
-                            .map(|p| p == &file_path)
-                            .unwrap_or(false)
-                    });
-                    if is_active {
-                        continue;
-                    }
+                if finished_only && active_jsonl.contains(&file_path) {
+                    continue;
                 }
 
                 let size = metadata.len();
@@ -1055,7 +1057,7 @@ pub(crate) fn run_clean(
 
 pub(crate) fn print_summary(since: &str) -> io::Result<()> {
     let since_duration = parse_duration_str(since);
-    let app = App::new();
+    let app = App::with_host_state();
     let snap = app.data_snapshot();
 
     if snap.sessions.is_empty() {
@@ -1193,7 +1195,7 @@ fn make_app(demo: bool, filters: &ViewFilters) -> App {
         });
         app
     } else {
-        App::new()
+        App::with_host_state()
     };
     apply_filters(&mut app, filters);
     app
@@ -1273,7 +1275,7 @@ pub(crate) fn run_watch(
     use crate::session::SessionStatus;
     use std::collections::HashMap;
 
-    let mut app = App::new();
+    let mut app = App::with_host_state();
     apply_filters(&mut app, filters);
     let mut prev_statuses: HashMap<u32, SessionStatus> = app
         .data_snapshot()
diff --git a/src/main.rs b/src/main.rs
index 051dd431..aefaf618 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -766,7 +766,7 @@ fn run_tui<W: io::Write>(
     max_duration: Option<Duration>,
     auto_init_summary: Option<String>,
 ) -> io::Result<()> {
-    let mut app = App::new();
+    let mut app = App::with_host_state();
     app.notify = cfg.notify;
     app.debug = cfg.debug;
     app.webhook_url = cfg.webhook.clone();
@@ -820,7 +820,7 @@ fn run_tui<W: io::Write>(
                 config::BrainConfig::default(),
             ));
         }
-        // Re-refresh to replace real sessions discovered during App::new()
+        // Replace the real sessions the host scan found with demo ones.
         app.refresh();
     }