diff --git a/crates/owlen-tui/Cargo.toml b/crates/owlen-tui/Cargo.toml
index 4f52c0b..de83d9a 100644
--- a/crates/owlen-tui/Cargo.toml
+++ b/crates/owlen-tui/Cargo.toml
@@ -31,6 +31,7 @@ syntect = "5.3"
 once_cell = "1.19"
 owlen-markdown = { path = "../owlen-markdown" }
 shellexpand = { workspace = true }
+regex = { workspace = true }
 
 # Async runtime
 tokio = { workspace = true }
diff --git a/crates/owlen-tui/keymap.toml b/crates/owlen-tui/keymap.toml
index a37857f..7d926b2 100644
--- a/crates/owlen-tui/keymap.toml
+++ b/crates/owlen-tui/keymap.toml
@@ -72,3 +72,28 @@ command = "composer.submit"
 mode = "normal"
 keys = ["Ctrl+;"]
 command = "mode.command"
+
+[[binding]]
+mode = "normal"
+keys = ["F12"]
+command = "debug.toggle"
+
+[[binding]]
+mode = "editing"
+keys = ["F12"]
+command = "debug.toggle"
+
+[[binding]]
+mode = "visual"
+keys = ["F12"]
+command = "debug.toggle"
+
+[[binding]]
+mode = "command"
+keys = ["F12"]
+command = "debug.toggle"
+
+[[binding]]
+mode = "help"
+keys = ["F12"]
+command = "debug.toggle"
diff --git a/crates/owlen-tui/src/chat_app.rs b/crates/owlen-tui/src/chat_app.rs
index 6fe271f..ae92197 100644
--- a/crates/owlen-tui/src/chat_app.rs
+++ b/crates/owlen-tui/src/chat_app.rs
@@ -48,10 +48,11 @@ use crate::events::Event;
 use crate::model_info_panel::ModelInfoPanel;
 use crate::slash::{self, McpSlashCommand, SlashCommand};
 use crate::state::{
-    CodeWorkspace, CommandPalette, FileFilterMode, FileIconResolver, FileNode, FileTreeState,
-    Keymap, ModelPaletteEntry, PaletteSuggestion, PaneDirection, PaneRestoreRequest,
-    RepoSearchMessage, RepoSearchState, SplitAxis, SymbolSearchMessage, SymbolSearchState,
-    WorkspaceSnapshot, spawn_repo_search_task, spawn_symbol_search_task,
+    CodeWorkspace, CommandPalette, DebugLogEntry, DebugLogState, FileFilterMode, FileIconResolver,
+    FileNode, FileTreeState, Keymap, ModelPaletteEntry, PaletteSuggestion, PaneDirection,
+    PaneRestoreRequest, RepoSearchMessage, RepoSearchState, SplitAxis, SymbolSearchMessage,
+    SymbolSearchState, WorkspaceSnapshot, install_global_logger, spawn_repo_search_task,
+    spawn_symbol_search_task,
 };
 use crate::toast::{Toast, ToastLevel, ToastManager};
 use crate::ui::format_tool_output;
@@ -75,6 +76,7 @@ use std::sync::Arc;
 use std::time::{Duration, Instant, SystemTime};
 
 use dirs::{config_dir, data_local_dir};
+use log::Level;
 use serde_json::{Value, json};
 
 const ONBOARDING_STATUS_LINE: &str =
@@ -481,6 +483,7 @@ pub struct ChatApp {
     queued_consents: VecDeque<ConsentDialogState>, // Backlog of consent requests
     system_status: String,        // System/status messages (tool execution, status, etc)
     toasts: ToastManager,
+    debug_log: DebugLogState,
     /// Simple execution budget: maximum number of tool calls allowed per session.
     _execution_budget: usize,
     /// Agent mode enabled
@@ -655,6 +658,8 @@ impl ChatApp {
         let file_tree = FileTreeState::new(workspace_root);
         let file_icons = FileIconResolver::from_mode(icon_mode);
 
+        install_global_logger();
+
         let mut app = Self {
             controller,
             mode: InputMode::Normal,
@@ -748,6 +753,7 @@ impl ChatApp {
                 String::new()
             },
             toasts: ToastManager::new(),
+            debug_log: DebugLogState::new(),
             _execution_budget: 50,
             agent_mode: false,
             agent_running: false,
@@ -1866,6 +1872,25 @@ impl ChatApp {
         &self.theme
     }
 
+    pub fn is_debug_log_visible(&self) -> bool {
+        self.debug_log.is_visible()
+    }
+
+    pub fn toggle_debug_log_panel(&mut self) {
+        let now_visible = self.debug_log.toggle_visible();
+        if now_visible {
+            self.status = "Debug log open — F12 to hide".to_string();
+            self.error = None;
+        } else {
+            self.status = "Debug log hidden".to_string();
+            self.error = None;
+        }
+    }
+
+    pub fn debug_log_entries(&self) -> Vec<DebugLogEntry> {
+        self.debug_log.entries()
+    }
+
     pub fn toasts(&self) -> impl Iterator<Item = &Toast> {
         self.toasts.iter()
     }
@@ -1878,6 +1903,56 @@ impl ChatApp {
         self.toasts.retain_active();
     }
 
+    fn poll_debug_log_updates(&mut self) {
+        let new_entries = self.debug_log.take_unseen();
+        if new_entries.is_empty() {
+            return;
+        }
+
+        let mut latest_summary: Option<(Level, String)> = None;
+
+        for entry in new_entries.iter() {
+            let toast_level = match entry.level {
+                Level::Error => ToastLevel::Error,
+                Level::Warn => ToastLevel::Warning,
+                _ => continue,
+            };
+
+            let summary = format!("{}: {}", entry.target, entry.message);
+            let clipped = Self::ellipsize(&summary, 120);
+            self.push_toast(toast_level, clipped.clone());
+            latest_summary = Some((entry.level, clipped));
+        }
+
+        if !self.debug_log.is_visible() {
+            if let Some((level, message)) = latest_summary {
+                let level_label = match level {
+                    Level::Error => "Error",
+                    Level::Warn => "Warning",
+                    _ => "Log",
+                };
+                self.status = format!("{level_label}: {message}  (F12 to open debug log)");
+                self.error = None;
+            }
+        }
+    }
+
+    fn ellipsize(message: &str, max_len: usize) -> String {
+        if message.chars().count() <= max_len {
+            return message.to_string();
+        }
+
+        let mut truncated = String::new();
+        for (idx, ch) in message.chars().enumerate() {
+            if idx + 1 >= max_len {
+                truncated.push('…');
+                break;
+            }
+            truncated.push(ch);
+        }
+        truncated
+    }
+
     pub fn input_max_rows(&self) -> u16 {
         let config = self.controller.config();
         config.ui.input_max_rows.max(1)
@@ -3264,6 +3339,11 @@ impl ChatApp {
                 self.handle_app_effects(effects).await?;
                 Ok(true)
             }
+            AppCommand::ToggleDebugLog => {
+                self.pending_key = None;
+                self.toggle_debug_log_panel();
+                Ok(true)
+            }
         }
     }
 
@@ -4877,6 +4957,7 @@ impl ChatApp {
             Event::Tick => {
                 self.poll_repo_search();
                 self.poll_symbol_search();
+                self.poll_debug_log_updates();
                 self.prune_toasts();
                 // Future: update streaming timers
             }
diff --git a/crates/owlen-tui/src/commands/mod.rs b/crates/owlen-tui/src/commands/mod.rs
index 5192915..50fbdda 100644
--- a/crates/owlen-tui/src/commands/mod.rs
+++ b/crates/owlen-tui/src/commands/mod.rs
@@ -243,6 +243,10 @@ const COMMANDS: &[CommandSpec] = &[
         keyword: "explorer",
         description: "Alias for files",
     },
+    CommandSpec {
+        keyword: "debug log",
+        description: "Toggle the debug log panel",
+    },
 ];
 
 /// Return the static catalog of commands.
diff --git a/crates/owlen-tui/src/commands/registry.rs b/crates/owlen-tui/src/commands/registry.rs
index c704b1c..7aa625f 100644
--- a/crates/owlen-tui/src/commands/registry.rs
+++ b/crates/owlen-tui/src/commands/registry.rs
@@ -13,6 +13,7 @@ pub enum AppCommand {
     FocusPanel(FocusedPanel),
     ComposerSubmit,
     EnterCommandMode,
+    ToggleDebugLog,
 }
 
 #[derive(Debug)]
@@ -65,6 +66,7 @@ impl CommandRegistry {
         );
         commands.insert("composer.submit".to_string(), AppCommand::ComposerSubmit);
         commands.insert("mode.command".to_string(), AppCommand::EnterCommandMode);
+        commands.insert("debug.toggle".to_string(), AppCommand::ToggleDebugLog);
 
         Self { commands }
     }
diff --git a/crates/owlen-tui/src/state/debug_log.rs b/crates/owlen-tui/src/state/debug_log.rs
new file mode 100644
index 0000000..f503684
--- /dev/null
+++ b/crates/owlen-tui/src/state/debug_log.rs
@@ -0,0 +1,235 @@
+use chrono::{DateTime, Local};
+use log::{Level, LevelFilter, Metadata, Record};
+use once_cell::sync::{Lazy, OnceCell};
+use regex::Regex;
+use std::collections::VecDeque;
+use std::sync::Mutex;
+
+/// Maximum number of entries to retain in the in-memory ring buffer.
+const MAX_ENTRIES: usize = 256;
+
+/// Global access handle for the debug log store.
+static STORE: Lazy<DebugLogStore> = Lazy::new(DebugLogStore::default);
+static LOGGER: OnceCell<()> = OnceCell::new();
+static DEBUG_LOGGER: DebugLogger = DebugLogger;
+
+/// Install the in-process logger that feeds the debug log ring buffer.
+pub fn install_global_logger() {
+    LOGGER.get_or_init(|| {
+        if log::set_logger(&DEBUG_LOGGER).is_ok() {
+            log::set_max_level(LevelFilter::Trace);
+        }
+    });
+}
+
+/// Per-application state for presenting and acknowledging debug log entries.
+#[derive(Debug)]
+pub struct DebugLogState {
+    visible: bool,
+    last_seen_id: u64,
+}
+
+impl DebugLogState {
+    pub fn new() -> Self {
+        let last_seen_id = STORE.latest_id();
+        Self {
+            visible: false,
+            last_seen_id,
+        }
+    }
+
+    pub fn toggle_visible(&mut self) -> bool {
+        self.visible = !self.visible;
+        if self.visible {
+            self.mark_seen();
+        }
+        self.visible
+    }
+
+    pub fn set_visible(&mut self, visible: bool) {
+        self.visible = visible;
+        if visible {
+            self.mark_seen();
+        }
+    }
+
+    pub fn is_visible(&self) -> bool {
+        self.visible
+    }
+
+    pub fn entries(&self) -> Vec<DebugLogEntry> {
+        STORE.snapshot()
+    }
+
+    pub fn take_unseen(&mut self) -> Vec<DebugLogEntry> {
+        let entries = STORE.entries_since(self.last_seen_id);
+        if let Some(entry) = entries.last() {
+            self.last_seen_id = entry.id;
+        }
+        entries
+    }
+
+    pub fn has_unseen(&self) -> bool {
+        STORE.latest_id() > self.last_seen_id
+    }
+
+    fn mark_seen(&mut self) {
+        self.last_seen_id = STORE.latest_id();
+    }
+}
+
+impl Default for DebugLogState {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+/// Metadata describing a single debug log entry.
+#[derive(Clone, Debug)]
+pub struct DebugLogEntry {
+    pub id: u64,
+    pub timestamp: DateTime<Local>,
+    pub level: Level,
+    pub target: String,
+    pub message: String,
+}
+
+#[derive(Default)]
+struct DebugLogStore {
+    inner: Mutex<Inner>,
+}
+
+#[derive(Default)]
+struct Inner {
+    entries: VecDeque<DebugLogEntry>,
+    next_id: u64,
+}
+
+impl DebugLogStore {
+    fn snapshot(&self) -> Vec<DebugLogEntry> {
+        let inner = self.inner.lock().unwrap();
+        inner.entries.iter().cloned().collect()
+    }
+
+    fn latest_id(&self) -> u64 {
+        let inner = self.inner.lock().unwrap();
+        inner.next_id
+    }
+
+    fn entries_since(&self, last_seen_id: u64) -> Vec<DebugLogEntry> {
+        let inner = self.inner.lock().unwrap();
+        inner
+            .entries
+            .iter()
+            .filter(|entry| entry.id > last_seen_id)
+            .cloned()
+            .collect()
+    }
+
+    fn push(&self, level: Level, target: &str, message: &str) -> DebugLogEntry {
+        let sanitized = sanitize_message(message);
+        let mut inner = self.inner.lock().unwrap();
+        inner.next_id = inner.next_id.saturating_add(1);
+        let entry = DebugLogEntry {
+            id: inner.next_id,
+            timestamp: Local::now(),
+            level,
+            target: target.to_string(),
+            message: sanitized,
+        };
+        inner.entries.push_back(entry.clone());
+        while inner.entries.len() > MAX_ENTRIES {
+            inner.entries.pop_front();
+        }
+        entry
+    }
+}
+
+struct DebugLogger;
+
+impl log::Log for DebugLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= LevelFilter::Trace
+    }
+
+    fn log(&self, record: &Record) {
+        if !self.enabled(record.metadata()) {
+            return;
+        }
+
+        // Only persist warnings and errors in the in-memory buffer.
+        if record.level() < Level::Warn {
+            return;
+        }
+
+        let message = record.args().to_string();
+        let entry = STORE.push(record.level(), record.target(), &message);
+
+        if record.level() == Level::Error {
+            eprintln!(
+                "[owlen:error][{}] {}",
+                entry.timestamp.format("%Y-%m-%d %H:%M:%S"),
+                entry.message
+            );
+        } else if record.level() == Level::Warn {
+            eprintln!(
+                "[owlen:warn][{}] {}",
+                entry.timestamp.format("%Y-%m-%d %H:%M:%S"),
+                entry.message
+            );
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+fn sanitize_message(message: &str) -> String {
+    static AUTH_HEADER: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?i)\b(authorization)(\s*[:=]\s*)([^\r\n]+)").unwrap());
+    static GENERIC_SECRET: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?i)\b(api[_-]?key|token)(\s*[:=]\s*)([^,\s;]+)").unwrap());
+    static BEARER_TOKEN: Lazy<Regex> =
+        Lazy::new(|| Regex::new(r"(?i)\bBearer\s+[A-Za-z0-9._\-+/=]+").unwrap());
+
+    let step = AUTH_HEADER.replace_all(message, |caps: &regex::Captures<'_>| {
+        format!("{}{}<redacted>", &caps[1], &caps[2])
+    });
+
+    let step = GENERIC_SECRET.replace_all(&step, |caps: &regex::Captures<'_>| {
+        format!("{}{}<redacted>", &caps[1], &caps[2])
+    });
+
+    BEARER_TOKEN
+        .replace_all(&step, "Bearer <redacted>")
+        .into_owned()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn sanitize_masks_common_tokens() {
+        let input =
+            "Authorization: Bearer abc123 token=xyz456 KEY=value Authorization=Token secretStuff";
+        let sanitized = sanitize_message(input);
+        assert!(!sanitized.contains("abc123"));
+        assert!(!sanitized.contains("xyz456"));
+        assert!(!sanitized.contains("secretStuff"));
+        assert_eq!(sanitized, "Authorization: <redacted>");
+    }
+
+    #[test]
+    fn ring_buffer_discards_old_entries() {
+        install_global_logger();
+        let initial_latest = STORE.latest_id();
+        for idx in 0..(MAX_ENTRIES as u64 + 10) {
+            let message = format!("warn #{idx}");
+            STORE.push(Level::Warn, "test", &message);
+        }
+
+        let entries = STORE.snapshot();
+        assert_eq!(entries.len(), MAX_ENTRIES);
+        assert!(entries.first().unwrap().id > initial_latest);
+    }
+}
diff --git a/crates/owlen-tui/src/state/keymap.rs b/crates/owlen-tui/src/state/keymap.rs
index f9e9f03..7d9e60f 100644
--- a/crates/owlen-tui/src/state/keymap.rs
+++ b/crates/owlen-tui/src/state/keymap.rs
@@ -284,7 +284,6 @@ fn normalize_modifiers(modifiers: KeyModifiers) -> KeyModifiers {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::widgets::model_picker::FilterMode;
     use crossterm::event::{KeyCode, KeyModifiers};
 
     #[test]
diff --git a/crates/owlen-tui/src/state/mod.rs b/crates/owlen-tui/src/state/mod.rs
index 3b802e5..d1dd0c3 100644
--- a/crates/owlen-tui/src/state/mod.rs
+++ b/crates/owlen-tui/src/state/mod.rs
@@ -6,6 +6,7 @@
 //! to test in isolation.
 
 mod command_palette;
+mod debug_log;
 mod file_icons;
 mod file_tree;
 mod keymap;
@@ -13,6 +14,7 @@ mod search;
 mod workspace;
 
 pub use command_palette::{CommandPalette, ModelPaletteEntry, PaletteGroup, PaletteSuggestion};
+pub use debug_log::{DebugLogEntry, DebugLogState, install_global_logger};
 pub use file_icons::{FileIconResolver, FileIconSet, IconDetection};
 pub use file_tree::{
     FileNode, FileTreeState, FilterMode as FileFilterMode, GitDecoration, VisibleFileEntry,
diff --git a/crates/owlen-tui/src/ui.rs b/crates/owlen-tui/src/ui.rs
index ed257ce..d74202c 100644
--- a/crates/owlen-tui/src/ui.rs
+++ b/crates/owlen-tui/src/ui.rs
@@ -1,3 +1,4 @@
+use log::Level;
 use pathdiff::diff_paths;
 use ratatui::Frame;
 use ratatui::layout::{Alignment, Constraint, Direction, Layout, Rect};
@@ -366,6 +367,20 @@ pub fn render_chat(frame: &mut Frame<'_>, app: &mut ChatApp) {
         render_code_workspace(frame, area, app);
     }
 
+    if app.is_debug_log_visible() {
+        let min_height = 6;
+        let computed_height = content_area.height.saturating_div(3).max(min_height);
+        let panel_height = computed_height.min(content_area.height);
+
+        if panel_height >= 4 {
+            let y = content_area
+                .y
+                .saturating_add(content_area.height.saturating_sub(panel_height));
+            let log_area = Rect::new(content_area.x, y, content_area.width, panel_height);
+            render_debug_log_panel(frame, log_area, app);
+        }
+    }
+
     render_toasts(frame, app, content_area);
 }
 
@@ -1964,6 +1979,134 @@ fn render_system_output(frame: &mut Frame<'_>, area: Rect, app: &ChatApp, messag
     frame.render_widget(paragraph, area);
 }
 
+fn render_debug_log_panel(frame: &mut Frame<'_>, area: Rect, app: &ChatApp) {
+    let theme = app.theme();
+    frame.render_widget(Clear, area);
+
+    let title = Line::from(vec![
+        Span::styled(
+            " Debug log ",
+            Style::default()
+                .fg(theme.pane_header_active)
+                .add_modifier(Modifier::BOLD),
+        ),
+        Span::styled(
+            "warnings & errors",
+            Style::default()
+                .fg(theme.pane_hint_text)
+                .add_modifier(Modifier::DIM),
+        ),
+    ]);
+
+    let block = Block::default()
+        .borders(Borders::ALL)
+        .border_style(Style::default().fg(theme.focused_panel_border))
+        .style(Style::default().bg(theme.background).fg(theme.text))
+        .title(title);
+
+    let inner = block.inner(area);
+    frame.render_widget(block, area);
+
+    if inner.width == 0 || inner.height == 0 {
+        return;
+    }
+
+    let entries = app.debug_log_entries();
+    let available_rows = inner.height as usize;
+    let mut lines: Vec<Line> = Vec::new();
+
+    if entries.is_empty() {
+        lines.push(Line::styled(
+            "No warnings captured this session.",
+            Style::default()
+                .fg(theme.pane_hint_text)
+                .add_modifier(Modifier::DIM),
+        ));
+    } else {
+        let total_entries = entries.len();
+        let mut subset: Vec<_> = entries.into_iter().rev().take(available_rows).collect();
+        subset.reverse();
+
+        if total_entries > subset.len() && subset.len() == available_rows && !subset.is_empty() {
+            subset.remove(0);
+        }
+
+        let overflow = total_entries.saturating_sub(subset.len());
+        if overflow > 0 {
+            lines.push(Line::styled(
+                format!("… {overflow} older entries not shown"),
+                Style::default()
+                    .fg(theme.pane_hint_text)
+                    .add_modifier(Modifier::DIM),
+            ));
+        }
+
+        for entry in subset {
+            let (label, badge_style, message_style) = debug_level_styles(entry.level, theme);
+            let timestamp = entry.timestamp.format("%H:%M:%S");
+
+            let mut spans = vec![
+                Span::styled(format!(" {label} "), badge_style),
+                Span::raw(" "),
+                Span::styled(
+                    timestamp.to_string(),
+                    Style::default()
+                        .fg(theme.pane_hint_text)
+                        .add_modifier(Modifier::DIM),
+                ),
+            ];
+
+            if !entry.target.is_empty() {
+                spans.push(Span::raw(" "));
+                spans.push(Span::styled(
+                    entry.target,
+                    Style::default().fg(theme.pane_header_active),
+                ));
+            }
+
+            spans.push(Span::raw("  "));
+            spans.push(Span::styled(entry.message, message_style));
+            lines.push(Line::from(spans));
+        }
+    }
+
+    let paragraph = Paragraph::new(lines)
+        .wrap(Wrap { trim: true })
+        .alignment(Alignment::Left)
+        .style(Style::default().bg(theme.background));
+
+    frame.render_widget(paragraph, inner);
+}
+
+fn debug_level_styles(level: Level, theme: &Theme) -> (&'static str, Style, Style) {
+    match level {
+        Level::Error => (
+            "ERR",
+            Style::default()
+                .fg(theme.background)
+                .bg(theme.error)
+                .add_modifier(Modifier::BOLD),
+            Style::default().fg(theme.error),
+        ),
+        Level::Warn => (
+            "WARN",
+            Style::default()
+                .fg(theme.background)
+                .bg(theme.agent_action)
+                .add_modifier(Modifier::BOLD),
+            Style::default().fg(theme.agent_action),
+        ),
+        _ => (
+            "INFO",
+            Style::default()
+                .fg(theme.background)
+                .bg(theme.info)
+                .add_modifier(Modifier::BOLD),
+            Style::default().fg(theme.text),
+        ),
+    }
+}
+
 fn calculate_wrapped_line_count<'a, I>(lines: I, available_width: u16) -> usize
 where
     I: IntoIterator<Item = &'a str>,
@@ -2944,6 +3087,7 @@ fn render_help(frame: &mut Frame<'_>, app: &ChatApp) {
             Line::from("  Ctrl+↑/↓      → adjust chat ↔ thinking split"),
             Line::from("  Alt+←/→/↑/↓  → resize focused code pane"),
             Line::from("  g then t      → expand files panel and focus it"),
+            Line::from("  F12           → toggle debug log panel"),
             Line::from("  F1 or ?        → toggle this help overlay"),
             Line::from(""),
             Line::from(vec![Span::styled(
@@ -3086,6 +3230,7 @@ fn render_help(frame: &mut Frame<'_>, app: &ChatApp) {
             )]),
             Line::from("  :h, :help          → show this help"),
             Line::from("  F1 or ?           → toggle help overlay"),
+            Line::from("  F12               → toggle debug log panel"),
             Line::from("  :files, :explorer → toggle files panel"),
             Line::from("  :markdown [on|off] → toggle markdown rendering"),
             Line::from("  Ctrl+←/→          → resize files panel"),