feat(ecc2): implement live output streaming per agent (#774)

- PTY output capture via tokio::process with stdout/stderr piping
- Ring buffer (1000 lines) per session
- Output pane wired to show selected session with auto-scroll
- Broadcast channel for output events

ecc2/src/session/mod.rs

@@ -1,5 +1,7 @@
 pub mod daemon;
 pub mod manager;
+pub mod output;
+pub mod runtime;
 pub mod store;
 
 use chrono::{DateTime, Utc};

ecc2/src/session/output.rs

@@ -0,0 +1,149 @@
+use std::collections::{HashMap, VecDeque};
+use std::sync::{Arc, Mutex, MutexGuard};
+
+use serde::{Deserialize, Serialize};
+use tokio::sync::broadcast;
+
+pub const OUTPUT_BUFFER_LIMIT: usize = 1000;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum OutputStream {
+    Stdout,
+    Stderr,
+}
+
+impl OutputStream {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Stdout => "stdout",
+            Self::Stderr => "stderr",
+        }
+    }
+
+    pub fn from_db_value(value: &str) -> Self {
+        match value {
+            "stderr" => Self::Stderr,
+            _ => Self::Stdout,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct OutputLine {
+    pub stream: OutputStream,
+    pub text: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct OutputEvent {
+    pub session_id: String,
+    pub line: OutputLine,
+}
+
+#[derive(Clone)]
+pub struct SessionOutputStore {
+    capacity: usize,
+    buffers: Arc<Mutex<HashMap<String, VecDeque<OutputLine>>>>,
+    tx: broadcast::Sender<OutputEvent>,
+}
+
+impl Default for SessionOutputStore {
+    fn default() -> Self {
+        Self::new(OUTPUT_BUFFER_LIMIT)
+    }
+}
+
+impl SessionOutputStore {
+    pub fn new(capacity: usize) -> Self {
+        let capacity = capacity.max(1);
+        let (tx, _) = broadcast::channel(capacity.max(16));
+
+        Self {
+            capacity,
+            buffers: Arc::new(Mutex::new(HashMap::new())),
+            tx,
+        }
+    }
+
+    pub fn subscribe(&self) -> broadcast::Receiver<OutputEvent> {
+        self.tx.subscribe()
+    }
+
+    pub fn push_line(&self, session_id: &str, stream: OutputStream, text: impl Into<String>) {
+        let line = OutputLine {
+            stream,
+            text: text.into(),
+        };
+
+        {
+            let mut buffers = self.lock_buffers();
+            let buffer = buffers.entry(session_id.to_string()).or_default();
+            buffer.push_back(line.clone());
+
+            while buffer.len() > self.capacity {
+                let _ = buffer.pop_front();
+            }
+        }
+
+        let _ = self.tx.send(OutputEvent {
+            session_id: session_id.to_string(),
+            line,
+        });
+    }
+
+    pub fn replace_lines(&self, session_id: &str, lines: Vec<OutputLine>) {
+        let mut buffer: VecDeque<OutputLine> = lines.into_iter().collect();
+
+        while buffer.len() > self.capacity {
+            let _ = buffer.pop_front();
+        }
+
+        self.lock_buffers().insert(session_id.to_string(), buffer);
+    }
+
+    pub fn lines(&self, session_id: &str) -> Vec<OutputLine> {
+        self.lock_buffers()
+            .get(session_id)
+            .map(|buffer| buffer.iter().cloned().collect())
+            .unwrap_or_default()
+    }
+
+    fn lock_buffers(&self) -> MutexGuard<'_, HashMap<String, VecDeque<OutputLine>>> {
+        self.buffers
+            .lock()
+            .unwrap_or_else(|poisoned| poisoned.into_inner())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{OutputStream, SessionOutputStore};
+
+    #[test]
+    fn ring_buffer_keeps_most_recent_lines() {
+        let store = SessionOutputStore::new(3);
+
+        store.push_line("session-1", OutputStream::Stdout, "line-1");
+        store.push_line("session-1", OutputStream::Stdout, "line-2");
+        store.push_line("session-1", OutputStream::Stdout, "line-3");
+        store.push_line("session-1", OutputStream::Stdout, "line-4");
+
+        let lines = store.lines("session-1");
+        let texts: Vec<_> = lines.iter().map(|line| line.text.as_str()).collect();
+
+        assert_eq!(texts, vec!["line-2", "line-3", "line-4"]);
+    }
+
+    #[tokio::test]
+    async fn pushing_output_broadcasts_events() {
+        let store = SessionOutputStore::new(8);
+        let mut rx = store.subscribe();
+
+        store.push_line("session-1", OutputStream::Stderr, "problem");
+
+        let event = rx.recv().await.expect("broadcast event");
+        assert_eq!(event.session_id, "session-1");
+        assert_eq!(event.line.stream, OutputStream::Stderr);
+        assert_eq!(event.line.text, "problem");
+    }
+}

ecc2/src/session/runtime.rs

@@ -0,0 +1,176 @@
+use std::path::{Path, PathBuf};
+use std::process::ExitStatus;
+use std::process::Stdio;
+
+use anyhow::{Context, Result};
+use tokio::io::{AsyncBufReadExt, AsyncRead, BufReader};
+use tokio::process::Command;
+
+use super::output::{OutputStream, SessionOutputStore};
+use super::store::StateStore;
+use super::SessionState;
+
+pub async fn capture_command_output(
+    db_path: PathBuf,
+    session_id: String,
+    mut command: Command,
+    output_store: SessionOutputStore,
+) -> Result<ExitStatus> {
+    let result = async {
+        let mut child = command
+            .stdout(Stdio::piped())
+            .stderr(Stdio::piped())
+            .spawn()
+            .with_context(|| format!("Failed to start process for session {}", session_id))?;
+
+        update_session_state(&db_path, &session_id, SessionState::Running)?;
+
+        let stdout = child.stdout.take().context("Child stdout was not piped")?;
+        let stderr = child.stderr.take().context("Child stderr was not piped")?;
+
+        let stdout_task = tokio::spawn(capture_stream(
+            db_path.clone(),
+            session_id.clone(),
+            stdout,
+            OutputStream::Stdout,
+            output_store.clone(),
+        ));
+        let stderr_task = tokio::spawn(capture_stream(
+            db_path.clone(),
+            session_id.clone(),
+            stderr,
+            OutputStream::Stderr,
+            output_store,
+        ));
+
+        let status = child.wait().await?;
+        stdout_task.await??;
+        stderr_task.await??;
+
+        let final_state = if status.success() {
+            SessionState::Completed
+        } else {
+            SessionState::Failed
+        };
+        update_session_state(&db_path, &session_id, final_state)?;
+
+        Ok(status)
+    }
+    .await;
+
+    if result.is_err() {
+        let _ = update_session_state(&db_path, &session_id, SessionState::Failed);
+    }
+
+    result
+}
+
+async fn capture_stream<R>(
+    db_path: PathBuf,
+    session_id: String,
+    reader: R,
+    stream: OutputStream,
+    output_store: SessionOutputStore,
+) -> Result<()>
+where
+    R: AsyncRead + Unpin,
+{
+    let mut lines = BufReader::new(reader).lines();
+
+    while let Some(line) = lines.next_line().await? {
+        output_store.push_line(&session_id, stream, line.clone());
+        append_output_line(&db_path, &session_id, stream, &line)?;
+    }
+
+    Ok(())
+}
+
+fn append_output_line(
+    db_path: &Path,
+    session_id: &str,
+    stream: OutputStream,
+    line: &str,
+) -> Result<()> {
+    let db = StateStore::open(db_path)?;
+    db.append_output_line(session_id, stream, line)?;
+    Ok(())
+}
+
+fn update_session_state(db_path: &Path, session_id: &str, state: SessionState) -> Result<()> {
+    let db = StateStore::open(db_path)?;
+    db.update_state(session_id, &state)?;
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashSet;
+    use std::env;
+
+    use anyhow::Result;
+    use chrono::Utc;
+    use tokio::process::Command;
+    use uuid::Uuid;
+
+    use super::capture_command_output;
+    use crate::session::output::{SessionOutputStore, OUTPUT_BUFFER_LIMIT};
+    use crate::session::store::StateStore;
+    use crate::session::{Session, SessionMetrics, SessionState};
+
+    #[tokio::test]
+    async fn capture_command_output_persists_lines_and_events() -> Result<()> {
+        let db_path = env::temp_dir().join(format!("ecc2-runtime-{}.db", Uuid::new_v4()));
+        let db = StateStore::open(&db_path)?;
+        let session_id = "session-1".to_string();
+        let now = Utc::now();
+
+        db.insert_session(&Session {
+            id: session_id.clone(),
+            task: "stream output".to_string(),
+            agent_type: "test".to_string(),
+            state: SessionState::Pending,
+            worktree: None,
+            created_at: now,
+            updated_at: now,
+            metrics: SessionMetrics::default(),
+        })?;
+
+        let output_store = SessionOutputStore::default();
+        let mut rx = output_store.subscribe();
+        let mut command = Command::new("/bin/sh");
+        command
+            .arg("-c")
+            .arg("printf 'alpha\\n'; printf 'beta\\n' >&2");
+
+        let status =
+            capture_command_output(db_path.clone(), session_id.clone(), command, output_store)
+                .await?;
+
+        assert!(status.success());
+
+        let db = StateStore::open(&db_path)?;
+        let session = db
+            .get_session(&session_id)?
+            .expect("session should still exist");
+        assert_eq!(session.state, SessionState::Completed);
+
+        let lines = db.get_output_lines(&session_id, OUTPUT_BUFFER_LIMIT)?;
+        let texts: HashSet<_> = lines.iter().map(|line| line.text.as_str()).collect();
+        assert_eq!(lines.len(), 2);
+        assert!(texts.contains("alpha"));
+        assert!(texts.contains("beta"));
+
+        let mut events = Vec::new();
+        while let Ok(event) = rx.try_recv() {
+            events.push(event.line.text);
+        }
+
+        assert_eq!(events.len(), 2);
+        assert!(events.iter().any(|line| line == "alpha"));
+        assert!(events.iter().any(|line| line == "beta"));
+
+        let _ = std::fs::remove_file(db_path);
+
+        Ok(())
+    }
+}

ecc2/src/session/store.rs

@@ -1,7 +1,9 @@
 use anyhow::Result;
 use rusqlite::Connection;
 use std::path::Path;
+use std::time::Duration;
 
+use super::output::{OutputLine, OutputStream, OUTPUT_BUFFER_LIMIT};
 use super::{Session, SessionMetrics, SessionState};
 
 pub struct StateStore {
@@ -11,6 +13,7 @@ pub struct StateStore {
 impl StateStore {
     pub fn open(path: &Path) -> Result<Self> {
         let conn = Connection::open(path)?;
+        conn.busy_timeout(Duration::from_secs(5))?;
         let store = Self { conn };
         store.init_schema()?;
         Ok(store)
@@ -57,9 +60,19 @@ impl StateStore {
                 timestamp TEXT NOT NULL
             );
 
+            CREATE TABLE IF NOT EXISTS session_output (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                session_id TEXT NOT NULL REFERENCES sessions(id),
+                stream TEXT NOT NULL,
+                line TEXT NOT NULL,
+                timestamp TEXT NOT NULL
+            );
+
             CREATE INDEX IF NOT EXISTS idx_sessions_state ON sessions(state);
             CREATE INDEX IF NOT EXISTS idx_tool_log_session ON tool_log(session_id);
             CREATE INDEX IF NOT EXISTS idx_messages_to ON messages(to_session, read);
+            CREATE INDEX IF NOT EXISTS idx_session_output_session
+                ON session_output(session_id, id);
             ",
         )?;
         Ok(())
@@ -170,16 +183,12 @@ impl StateStore {
 
     pub fn get_session(&self, id: &str) -> Result<Option<Session>> {
         let sessions = self.list_sessions()?;
-        Ok(sessions.into_iter().find(|s| s.id == id || s.id.starts_with(id)))
+        Ok(sessions
+            .into_iter()
+            .find(|s| s.id == id || s.id.starts_with(id)))
     }
 
-    pub fn send_message(
-        &self,
-        from: &str,
-        to: &str,
-        content: &str,
-        msg_type: &str,
-    ) -> Result<()> {
+    pub fn send_message(&self, from: &str, to: &str, content: &str, msg_type: &str) -> Result<()> {
         self.conn.execute(
             "INSERT INTO messages (from_session, to_session, content, msg_type, timestamp)
              VALUES (?1, ?2, ?3, ?4, ?5)",
@@ -187,4 +196,114 @@ impl StateStore {
         )?;
         Ok(())
     }
+
+    pub fn append_output_line(
+        &self,
+        session_id: &str,
+        stream: OutputStream,
+        line: &str,
+    ) -> Result<()> {
+        let now = chrono::Utc::now().to_rfc3339();
+
+        self.conn.execute(
+            "INSERT INTO session_output (session_id, stream, line, timestamp)
+             VALUES (?1, ?2, ?3, ?4)",
+            rusqlite::params![session_id, stream.as_str(), line, now],
+        )?;
+
+        self.conn.execute(
+            "DELETE FROM session_output
+             WHERE session_id = ?1
+               AND id NOT IN (
+                   SELECT id
+                   FROM session_output
+                   WHERE session_id = ?1
+                   ORDER BY id DESC
+                   LIMIT ?2
+               )",
+            rusqlite::params![session_id, OUTPUT_BUFFER_LIMIT as i64],
+        )?;
+
+        self.conn.execute(
+            "UPDATE sessions SET updated_at = ?1 WHERE id = ?2",
+            rusqlite::params![chrono::Utc::now().to_rfc3339(), session_id],
+        )?;
+
+        Ok(())
+    }
+
+    pub fn get_output_lines(&self, session_id: &str, limit: usize) -> Result<Vec<OutputLine>> {
+        let mut stmt = self.conn.prepare(
+            "SELECT stream, line
+             FROM (
+                 SELECT id, stream, line
+                 FROM session_output
+                 WHERE session_id = ?1
+                 ORDER BY id DESC
+                 LIMIT ?2
+             )
+             ORDER BY id ASC",
+        )?;
+
+        let lines = stmt
+            .query_map(rusqlite::params![session_id, limit as i64], |row| {
+                let stream: String = row.get(0)?;
+                let text: String = row.get(1)?;
+
+                Ok(OutputLine {
+                    stream: OutputStream::from_db_value(&stream),
+                    text,
+                })
+            })?
+            .collect::<Result<Vec<_>, _>>()?;
+
+        Ok(lines)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::env;
+
+    use anyhow::Result;
+    use chrono::Utc;
+    use uuid::Uuid;
+
+    use super::StateStore;
+    use crate::session::output::{OutputStream, OUTPUT_BUFFER_LIMIT};
+    use crate::session::{Session, SessionMetrics, SessionState};
+
+    #[test]
+    fn append_output_line_keeps_latest_buffer_window() -> Result<()> {
+        let db_path = env::temp_dir().join(format!("ecc2-store-{}.db", Uuid::new_v4()));
+        let db = StateStore::open(&db_path)?;
+        let now = Utc::now();
+
+        db.insert_session(&Session {
+            id: "session-1".to_string(),
+            task: "buffer output".to_string(),
+            agent_type: "claude".to_string(),
+            state: SessionState::Running,
+            worktree: None,
+            created_at: now,
+            updated_at: now,
+            metrics: SessionMetrics::default(),
+        })?;
+
+        for index in 0..(OUTPUT_BUFFER_LIMIT + 5) {
+            db.append_output_line("session-1", OutputStream::Stdout, &format!("line-{index}"))?;
+        }
+
+        let lines = db.get_output_lines("session-1", OUTPUT_BUFFER_LIMIT)?;
+        let texts: Vec<_> = lines.iter().map(|line| line.text.as_str()).collect();
+
+        assert_eq!(lines.len(), OUTPUT_BUFFER_LIMIT);
+        assert_eq!(texts.first().copied(), Some("line-5"));
+        let expected_last_line = format!("line-{}", OUTPUT_BUFFER_LIMIT + 4);
+        assert_eq!(texts.last().copied(), Some(expected_last_line.as_str()));
+
+        let _ = std::fs::remove_file(db_path);
+
+        Ok(())
+    }
 }

ecc2/src/tui/dashboard.rs

@@ -1,20 +1,28 @@
+use std::collections::HashMap;
+
 use ratatui::{
     prelude::*,
     widgets::{Block, Borders, List, ListItem, Paragraph, Tabs},
 };
+use tokio::sync::broadcast;
 
 use crate::config::Config;
-use crate::session::{Session, SessionState};
+use crate::session::output::{OutputEvent, OutputLine, SessionOutputStore, OUTPUT_BUFFER_LIMIT};
 use crate::session::store::StateStore;
+use crate::session::{Session, SessionState};
 
 pub struct Dashboard {
     db: StateStore,
-    cfg: Config,
+    output_store: SessionOutputStore,
+    output_rx: broadcast::Receiver<OutputEvent>,
     sessions: Vec<Session>,
+    session_output_cache: HashMap<String, Vec<OutputLine>>,
     selected_pane: Pane,
     selected_session: usize,
     show_help: bool,
-    scroll_offset: usize,
+    output_follow: bool,
+    output_scroll_offset: usize,
+    last_output_height: usize,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq)]
@@ -26,23 +34,39 @@ enum Pane {
 
 impl Dashboard {
     pub fn new(db: StateStore, cfg: Config) -> Self {
+        Self::with_output_store(db, cfg, SessionOutputStore::default())
+    }
+
+    pub fn with_output_store(
+        db: StateStore,
+        _cfg: Config,
+        output_store: SessionOutputStore,
+    ) -> Self {
         let sessions = db.list_sessions().unwrap_or_default();
-        Self {
+        let output_rx = output_store.subscribe();
+
+        let mut dashboard = Self {
             db,
-            cfg,
+            output_store,
+            output_rx,
             sessions,
+            session_output_cache: HashMap::new(),
             selected_pane: Pane::Sessions,
             selected_session: 0,
             show_help: false,
-            scroll_offset: 0,
-        }
+            output_follow: true,
+            output_scroll_offset: 0,
+            last_output_height: 0,
+        };
+        dashboard.sync_selected_output();
+        dashboard
     }
 
-    pub fn render(&self, frame: &mut Frame) {
+    pub fn render(&mut self, frame: &mut Frame) {
         let chunks = Layout::default()
             .direction(Direction::Vertical)
             .constraints([
-                Constraint::Length(3),  // Header
+                Constraint::Length(3), // Header
                 Constraint::Min(10),   // Main content
                 Constraint::Length(3), // Status bar
             ])
@@ -79,7 +103,11 @@ impl Dashboard {
     }
 
     fn render_header(&self, frame: &mut Frame, area: Rect) {
-        let running = self.sessions.iter().filter(|s| s.state == SessionState::Running).count();
+        let running = self
+            .sessions
+            .iter()
+            .filter(|s| s.state == SessionState::Running)
+            .count();
         let total = self.sessions.len();
 
         let title = format!(" ECC 2.0 | {running} running / {total} total ");
@@ -90,7 +118,11 @@ impl Dashboard {
                 Pane::Output => 1,
                 Pane::Metrics => 2,
             })
-            .highlight_style(Style::default().fg(Color::Cyan).add_modifier(Modifier::BOLD));
+            .highlight_style(
+                Style::default()
+                    .fg(Color::Cyan)
+                    .add_modifier(Modifier::BOLD),
+            );
 
         frame.render_widget(tabs, area);
     }
@@ -110,11 +142,18 @@ impl Dashboard {
                     SessionState::Pending => "◌",
                 };
                 let style = if i == self.selected_session {
-                    Style::default().fg(Color::Cyan).add_modifier(Modifier::BOLD)
+                    Style::default()
+                        .fg(Color::Cyan)
+                        .add_modifier(Modifier::BOLD)
                 } else {
                     Style::default()
                 };
-                let text = format!("{state_icon} {} [{}] {}", &s.id[..8.min(s.id.len())], s.agent_type, s.task);
+                let text = format!(
+                    "{state_icon} {} [{}] {}",
+                    &s.id[..8.min(s.id.len())],
+                    s.agent_type,
+                    s.task
+                );
                 ListItem::new(text).style(style)
             })
             .collect();
@@ -134,9 +173,21 @@ impl Dashboard {
         frame.render_widget(list, area);
     }
 
-    fn render_output(&self, frame: &mut Frame, area: Rect) {
-        let content = if let Some(session) = self.sessions.get(self.selected_session) {
-            format!("Agent output for session {}...\n\n(Live streaming coming soon)", session.id)
+    fn render_output(&mut self, frame: &mut Frame, area: Rect) {
+        self.sync_output_scroll(area.height.saturating_sub(2) as usize);
+
+        let content = if self.sessions.get(self.selected_session).is_some() {
+            let lines = self.selected_output_lines();
+
+            if lines.is_empty() {
+                "Waiting for session output...".to_string()
+            } else {
+                lines
+                    .iter()
+                    .map(|line| line.text.as_str())
+                    .collect::<Vec<_>>()
+                    .join("\n")
+            }
         } else {
             "No sessions. Press 'n' to start one.".to_string()
         };
@@ -147,12 +198,14 @@ impl Dashboard {
             Style::default()
         };
 
-        let paragraph = Paragraph::new(content).block(
-            Block::default()
-                .borders(Borders::ALL)
-                .title(" Output ")
-                .border_style(border_style),
-        );
+        let paragraph = Paragraph::new(content)
+            .block(
+                Block::default()
+                    .borders(Borders::ALL)
+                    .title(" Output ")
+                    .border_style(border_style),
+            )
+            .scroll((self.output_scroll_offset as u16, 0));
         frame.render_widget(paragraph, area);
     }
 
@@ -233,16 +286,38 @@ impl Dashboard {
     pub fn scroll_down(&mut self) {
         if self.selected_pane == Pane::Sessions && !self.sessions.is_empty() {
             self.selected_session = (self.selected_session + 1).min(self.sessions.len() - 1);
-        } else {
-            self.scroll_offset = self.scroll_offset.saturating_add(1);
+            self.reset_output_view();
+            self.sync_selected_output();
+        } else if self.selected_pane == Pane::Output {
+            let max_scroll = self.max_output_scroll();
+
+            if self.output_follow {
+                return;
+            }
+
+            if self.output_scroll_offset >= max_scroll.saturating_sub(1) {
+                self.output_follow = true;
+                self.output_scroll_offset = max_scroll;
+            } else {
+                self.output_scroll_offset = self.output_scroll_offset.saturating_add(1);
+            }
         }
     }
 
     pub fn scroll_up(&mut self) {
         if self.selected_pane == Pane::Sessions {
             self.selected_session = self.selected_session.saturating_sub(1);
+            self.reset_output_view();
+            self.sync_selected_output();
+        } else if self.selected_pane == Pane::Output {
+            if self.output_follow {
+                self.output_follow = false;
+                self.output_scroll_offset = self.max_output_scroll();
+            }
+
+            self.output_scroll_offset = self.output_scroll_offset.saturating_sub(1);
         } else {
-            self.scroll_offset = self.scroll_offset.saturating_sub(1);
+            self.output_scroll_offset = self.output_scroll_offset.saturating_sub(1);
         }
     }
 
@@ -260,6 +335,8 @@ impl Dashboard {
 
     pub fn refresh(&mut self) {
         self.sessions = self.db.list_sessions().unwrap_or_default();
+        self.clamp_selected_session();
+        self.sync_selected_output();
     }
 
     pub fn toggle_help(&mut self) {
@@ -267,7 +344,169 @@ impl Dashboard {
     }
 
     pub async fn tick(&mut self) {
-        // Periodic refresh every few ticks
+        loop {
+            match self.output_rx.try_recv() {
+                Ok(_event) => {}
+                Err(broadcast::error::TryRecvError::Empty) => break,
+                Err(broadcast::error::TryRecvError::Lagged(_)) => continue,
+                Err(broadcast::error::TryRecvError::Closed) => break,
+            }
+        }
+
         self.sessions = self.db.list_sessions().unwrap_or_default();
+        self.clamp_selected_session();
+        self.sync_selected_output();
+    }
+
+    fn clamp_selected_session(&mut self) {
+        if self.sessions.is_empty() {
+            self.selected_session = 0;
+        } else {
+            self.selected_session = self.selected_session.min(self.sessions.len() - 1);
+        }
+    }
+
+    fn sync_selected_output(&mut self) {
+        let Some(session_id) = self.selected_session_id().map(ToOwned::to_owned) else {
+            return;
+        };
+
+        match self.db.get_output_lines(&session_id, OUTPUT_BUFFER_LIMIT) {
+            Ok(lines) => {
+                self.output_store.replace_lines(&session_id, lines.clone());
+                self.session_output_cache.insert(session_id, lines);
+            }
+            Err(error) => {
+                tracing::warn!("Failed to load session output: {error}");
+            }
+        }
+    }
+
+    fn selected_session_id(&self) -> Option<&str> {
+        self.sessions
+            .get(self.selected_session)
+            .map(|session| session.id.as_str())
+    }
+
+    fn selected_output_lines(&self) -> &[OutputLine] {
+        self.selected_session_id()
+            .and_then(|session_id| self.session_output_cache.get(session_id))
+            .map(Vec::as_slice)
+            .unwrap_or(&[])
+    }
+
+    fn sync_output_scroll(&mut self, viewport_height: usize) {
+        self.last_output_height = viewport_height.max(1);
+        let max_scroll = self.max_output_scroll();
+
+        if self.output_follow {
+            self.output_scroll_offset = max_scroll;
+        } else {
+            self.output_scroll_offset = self.output_scroll_offset.min(max_scroll);
+        }
+    }
+
+    fn max_output_scroll(&self) -> usize {
+        self.selected_output_lines()
+            .len()
+            .saturating_sub(self.last_output_height.max(1))
+    }
+
+    fn reset_output_view(&mut self) {
+        self.output_follow = true;
+        self.output_scroll_offset = 0;
+    }
+
+    #[cfg(test)]
+    fn selected_output_text(&self) -> String {
+        self.selected_output_lines()
+            .iter()
+            .map(|line| line.text.clone())
+            .collect::<Vec<_>>()
+            .join("\n")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::env;
+
+    use anyhow::Result;
+    use chrono::Utc;
+    use uuid::Uuid;
+
+    use super::{Dashboard, Pane};
+    use crate::config::Config;
+    use crate::session::output::OutputStream;
+    use crate::session::store::StateStore;
+    use crate::session::{Session, SessionMetrics, SessionState};
+
+    #[test]
+    fn refresh_loads_selected_session_output_and_follows_tail() -> Result<()> {
+        let db_path = env::temp_dir().join(format!("ecc2-dashboard-{}.db", Uuid::new_v4()));
+        let db = StateStore::open(&db_path)?;
+        let now = Utc::now();
+
+        db.insert_session(&Session {
+            id: "session-1".to_string(),
+            task: "tail output".to_string(),
+            agent_type: "claude".to_string(),
+            state: SessionState::Running,
+            worktree: None,
+            created_at: now,
+            updated_at: now,
+            metrics: SessionMetrics::default(),
+        })?;
+
+        for index in 0..12 {
+            db.append_output_line("session-1", OutputStream::Stdout, &format!("line {index}"))?;
+        }
+
+        let mut dashboard = Dashboard::new(db, Config::default());
+        dashboard.selected_pane = Pane::Output;
+        dashboard.refresh();
+        dashboard.sync_output_scroll(4);
+
+        assert_eq!(dashboard.output_scroll_offset, 8);
+        assert!(dashboard.selected_output_text().contains("line 11"));
+
+        let _ = std::fs::remove_file(db_path);
+
+        Ok(())
+    }
+
+    #[test]
+    fn scrolling_up_disables_follow_mode() -> Result<()> {
+        let db_path = env::temp_dir().join(format!("ecc2-dashboard-{}.db", Uuid::new_v4()));
+        let db = StateStore::open(&db_path)?;
+        let now = Utc::now();
+
+        db.insert_session(&Session {
+            id: "session-1".to_string(),
+            task: "inspect output".to_string(),
+            agent_type: "claude".to_string(),
+            state: SessionState::Running,
+            worktree: None,
+            created_at: now,
+            updated_at: now,
+            metrics: SessionMetrics::default(),
+        })?;
+
+        for index in 0..6 {
+            db.append_output_line("session-1", OutputStream::Stdout, &format!("line {index}"))?;
+        }
+
+        let mut dashboard = Dashboard::new(db, Config::default());
+        dashboard.selected_pane = Pane::Output;
+        dashboard.refresh();
+        dashboard.sync_output_scroll(3);
+        dashboard.scroll_up();
+
+        assert!(!dashboard.output_follow);
+        assert_eq!(dashboard.output_scroll_offset, 2);
+
+        let _ = std::fs::remove_file(db_path);
+
+        Ok(())
     }
 }