diff --git a/src/cli.rs b/src/cli.rs
index 18a8e3a..7a90277 100644
--- a/src/cli.rs
+++ b/src/cli.rs
@@ -165,6 +165,15 @@ impl ChatCLI {
             "/effort" => {
                 self.handle_effort_command(&parts)?;
             }
+            "/stats" => {
+                self.show_session_stats()?;
+            }
+            "/optimize" => {
+                self.optimize_session()?;
+            }
+            "/cleanup" => {
+                self.cleanup_session()?;
+            }
             _ => {
                 self.display.print_error(&format!("Unknown command: {} (see /help)", parts[0]));
             }
@@ -226,7 +235,8 @@ impl ChatCLI {
     }
 
     fn list_sessions(&self) -> Result<()> {
-        let sessions = Session::list_sessions()?;
+        use crate::core::session::Session;
+        let sessions = Session::list_sessions_lazy(true)?;
         
         if sessions.is_empty() {
             self.display.print_info("No saved sessions");
@@ -234,10 +244,20 @@ impl ChatCLI {
         }
 
         self.display.print_info("Saved sessions:");
-        for (name, updated) in sessions {
-            let marker = if name == self.session.name { "★" } else { " " };
-            let date_str = updated.format("%Y-%m-%d %H:%M:%S");
-            println!("  {} {} (updated: {})", marker, name, date_str);
+        for session_info in sessions {
+            let marker = if session_info.name == self.session.name { "★" } else { " " };
+            let date_str = session_info.last_modified.format("%Y-%m-%d %H:%M:%S");
+            let model = session_info.model.as_deref().unwrap_or("unknown");
+            let msg_count = session_info.message_count.unwrap_or(0);
+            let file_size = session_info.file_size.unwrap_or(0);
+            let size_str = if file_size > 1024 { 
+                format!("{:.1}KB", file_size as f64 / 1024.0) 
+            } else { 
+                format!("{}B", file_size) 
+            };
+            
+            println!("  {} {} ({}msgs, {}, {}, {})", 
+                marker, session_info.name, msg_count, model, size_str, date_str);
         }
         
         Ok(())
@@ -429,4 +449,74 @@ impl ChatCLI {
         
         Ok(())
     }
+
+    fn show_session_stats(&self) -> Result<()> {
+        let stats = self.session.get_stats();
+        
+        self.display.print_info("Session Statistics:");
+        println!("  Total messages: {}", stats.total_messages);
+        println!("  User messages: {}", stats.user_messages);
+        println!("  Assistant messages: {}", stats.assistant_messages);
+        println!("  Total characters: {}", stats.total_characters);
+        println!("  Average message length: {}", stats.average_message_length);
+        
+        let memory_usage = std::mem::size_of_val(&self.session) + 
+                          self.session.messages.iter()
+                              .map(|m| m.content.len() + m.role.len())
+                              .sum::<usize>();
+        
+        let memory_str = if memory_usage > 1024 * 1024 {
+            format!("{:.1} MB", memory_usage as f64 / (1024.0 * 1024.0))
+        } else if memory_usage > 1024 {
+            format!("{:.1} KB", memory_usage as f64 / 1024.0)
+        } else {
+            format!("{} bytes", memory_usage)
+        };
+        
+        println!("  Estimated memory usage: {}", memory_str);
+        
+        if self.session.needs_cleanup() {
+            self.display.print_warning("Session is large and may benefit from cleanup (/cleanup)");
+        }
+        
+        Ok(())
+    }
+
+    fn optimize_session(&mut self) -> Result<()> {
+        let stats_before = self.session.get_stats();
+        
+        self.session.optimize_for_memory();
+        self.session.save()?;
+        
+        let stats_after = self.session.get_stats();
+        let chars_saved = stats_before.total_characters.saturating_sub(stats_after.total_characters);
+        
+        self.display.print_command_result(&format!(
+            "Session optimized: {} characters cleaned up",
+            chars_saved
+        ));
+        
+        Ok(())
+    }
+
+    fn cleanup_session(&mut self) -> Result<()> {
+        let stats_before = self.session.get_stats();
+        
+        if self.input.confirm("This will remove older messages to reduce memory usage. Continue?")? {
+            self.session.cleanup_for_memory();
+            self.session.save()?;
+            
+            let stats_after = self.session.get_stats();
+            let messages_removed = stats_before.total_messages.saturating_sub(stats_after.total_messages);
+            
+            self.display.print_command_result(&format!(
+                "Session cleaned up: {} messages removed, keeping most recent conversations",
+                messages_removed
+            ));
+        } else {
+            self.display.print_info("Cleanup cancelled");
+        }
+        
+        Ok(())
+    }
 }
\ No newline at end of file
diff --git a/src/core/session.rs b/src/core/session.rs
index 4de9878..875dd4b 100644
--- a/src/core/session.rs
+++ b/src/core/session.rs
@@ -18,6 +18,24 @@ pub struct Message {
     pub content: String,
 }
 
+#[derive(Debug, Clone)]
+pub struct ConversationStats {
+    pub total_messages: usize,
+    pub user_messages: usize,
+    pub assistant_messages: usize,
+    pub total_characters: usize,
+    pub average_message_length: usize,
+}
+
+#[derive(Debug, Clone)]
+pub struct SessionInfo {
+    pub name: String,
+    pub last_modified: DateTime<Utc>,
+    pub model: Option<String>,
+    pub message_count: Option<usize>,
+    pub file_size: Option<u64>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct SessionData {
     pub model: String,
@@ -144,6 +162,7 @@ impl Session {
             role: "user".to_string(),
             content,
         });
+        self.truncate_history_if_needed();
     }
 
     pub fn add_assistant_message(&mut self, content: String) {
@@ -151,6 +170,56 @@ impl Session {
             role: "assistant".to_string(),
             content,
         });
+        self.truncate_history_if_needed();
+    }
+
+    /// Truncates conversation history to stay within configured limits
+    fn truncate_history_if_needed(&mut self) {
+        let config = Config::load().unwrap_or_default();
+        let max_history = config.limits.max_conversation_history;
+        
+        // Always preserve the system prompt (first message)
+        if self.messages.len() > max_history + 1 {
+            let system_prompt = self.messages[0].clone();
+            let messages_to_keep = max_history;
+            let start_index = self.messages.len() - messages_to_keep;
+            
+            // Keep the most recent messages
+            let mut new_messages = vec![system_prompt];
+            new_messages.extend_from_slice(&self.messages[start_index..]);
+            
+            self.messages = new_messages;
+        }
+    }
+
+    /// Truncates individual messages that exceed reasonable length
+    pub fn truncate_long_messages(&mut self) {
+        const MAX_MESSAGE_LENGTH: usize = 10000; // 10k characters per message
+        const TRUNCATION_NOTICE: &str = "\n\n[Message truncated for performance...]";
+        
+        for message in &mut self.messages {
+            if message.content.len() > MAX_MESSAGE_LENGTH {
+                message.content.truncate(MAX_MESSAGE_LENGTH - TRUNCATION_NOTICE.len());
+                message.content.push_str(TRUNCATION_NOTICE);
+            }
+        }
+    }
+
+    /// Gets conversation statistics
+    pub fn get_stats(&self) -> ConversationStats {
+        let total_messages = self.messages.len();
+        let user_messages = self.messages.iter().filter(|m| m.role == "user").count();
+        let assistant_messages = self.messages.iter().filter(|m| m.role == "assistant").count();
+        let total_chars: usize = self.messages.iter().map(|m| m.content.len()).sum();
+        let avg_message_length = if total_messages > 0 { total_chars / total_messages } else { 0 };
+        
+        ConversationStats {
+            total_messages,
+            user_messages,
+            assistant_messages,
+            total_characters: total_chars,
+            average_message_length: avg_message_length,
+        }
     }
 
     pub fn clear_messages(&mut self) {
@@ -163,6 +232,13 @@ impl Session {
     }
 
     pub fn list_sessions() -> Result<Vec<(String, DateTime<Utc>)>> {
+        let sessions = Self::list_sessions_lazy(false)?;
+        Ok(sessions.into_iter().map(|s| (s.name, s.last_modified)).collect())
+    }
+
+    /// Lists sessions with lazy loading - only loads full data if detailed=true
+    pub fn list_sessions_lazy(detailed: bool) -> Result<Vec<SessionInfo>> {
+        let config = Config::load().unwrap_or_default();
         let sessions_dir = Self::sessions_dir()?;
         
         if !sessions_dir.exists() {
@@ -170,27 +246,124 @@ impl Session {
         }
 
         let mut sessions = Vec::new();
+        let mut count = 0;
         
         for entry in fs::read_dir(&sessions_dir)? {
             let entry = entry?;
             let path = entry.path();
             
+            // Respect max sessions limit for performance
+            if count >= config.limits.max_sessions_to_list {
+                break;
+            }
+            
             if let Some(extension) = path.extension() {
-                if extension == "json" {
+                if extension == config.session.file_extension.as_str() {
                     if let Some(name) = path.file_stem().and_then(|s| s.to_str()) {
                         let metadata = entry.metadata()?;
                         let modified = metadata.modified()?;
                         let datetime = DateTime::<Utc>::from(modified);
-                        sessions.push((name.to_string(), datetime));
+                        let file_size = metadata.len();
+                        
+                        let (model, message_count) = if detailed {
+                            // Only load session data if detailed info is requested
+                            match Self::get_session_metadata(name) {
+                                Ok((model, count)) => (Some(model), Some(count)),
+                                Err(_) => (None, None)
+                            }
+                        } else {
+                            (None, None)
+                        };
+                        
+                        sessions.push(SessionInfo {
+                            name: name.to_string(),
+                            last_modified: datetime,
+                            model,
+                            message_count,
+                            file_size: Some(file_size),
+                        });
+                        
+                        count += 1;
                     }
                 }
             }
         }
         
-        sessions.sort_by(|a, b| b.1.cmp(&a.1)); // Sort by modification time, newest first
+        sessions.sort_by(|a, b| b.last_modified.cmp(&a.last_modified)); // Sort by modification time, newest first
         Ok(sessions)
     }
 
+    /// Gets metadata from a session file without loading all messages
+    fn get_session_metadata(name: &str) -> Result<(String, usize)> {
+        let path = Self::session_path(name)?;
+        
+        if !path.exists() {
+            return Err(anyhow::anyhow!("Session '{}' does not exist", name));
+        }
+
+        let json_data = fs::read_to_string(&path)
+            .with_context(|| format!("Failed to read session from {:?}", path))?;
+        
+        // Parse only the fields we need for metadata
+        let data: SessionData = serde_json::from_str(&json_data)
+            .with_context(|| format!("Failed to parse session data from {:?}", path))?;
+        
+        Ok((data.model, data.messages.len()))
+    }
+
+    /// Optimizes session data in memory by removing redundant information
+    pub fn optimize_for_memory(&mut self) {
+        // Truncate very long messages for memory efficiency
+        self.truncate_long_messages();
+        
+        // Remove excessive whitespace from messages
+        for message in &mut self.messages {
+            message.content = message.content
+                .lines()
+                .map(|line| line.trim())
+                .collect::<Vec<_>>()
+                .join("\n")
+                .trim()
+                .to_string();
+        }
+    }
+
+    /// Checks if session needs cleanup based on size and age
+    pub fn needs_cleanup(&self) -> bool {
+        let stats = self.get_stats();
+        let config = Config::load().unwrap_or_default();
+        
+        // Check if conversation is too long
+        if stats.total_messages > config.limits.max_conversation_history * 2 {
+            return true;
+        }
+        
+        // Check if total character count is excessive (>1MB)
+        if stats.total_characters > 1_000_000 {
+            return true;
+        }
+        
+        false
+    }
+
+    /// Performs aggressive cleanup for memory optimization
+    pub fn cleanup_for_memory(&mut self) {
+        let config = Config::load().unwrap_or_default();
+        let target_messages = config.limits.max_conversation_history / 2;
+        
+        if self.messages.len() > target_messages + 1 {
+            let system_prompt = self.messages[0].clone();
+            let start_index = self.messages.len() - target_messages;
+            
+            let mut new_messages = vec![system_prompt];
+            new_messages.extend_from_slice(&self.messages[start_index..]);
+            
+            self.messages = new_messages;
+        }
+        
+        self.optimize_for_memory();
+    }
+
     pub fn delete_session(name: &str) -> Result<()> {
         let path = Self::session_path(name)?;
         
diff --git a/src/utils/display.rs b/src/utils/display.rs
index 9f39e52..428cf77 100644
--- a/src/utils/display.rs
+++ b/src/utils/display.rs
@@ -80,6 +80,9 @@ Available Commands:
   /tool websearch on|off   - Enable/disable web search (OpenAI only)
   /reasoning on|off        - Enable/disable reasoning summaries (OpenAI only)
   /effort [low|medium|high] - Set reasoning effort level (GPT-5 only)
+  /stats                   - Show current session statistics
+  /optimize                - Optimize session memory usage  
+  /cleanup                 - Remove older messages to free memory
 
 Environment Variables:
   OPENAI_API_KEY          - Required for OpenAI models