diff --git a/src/app.rs b/src/app.rs
index dc15c0c..352cd1d 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -1,7 +1,11 @@
-use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+use std::sync::Arc;
+
 use chrono::NaiveDateTime;
+use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
+use tokio::sync::mpsc;
 
 use crate::domain::models::*;
+use crate::infrastructure::api::ApiClient;
 use crate::infrastructure::db::Db;
 use crate::ui::{Focus, NetworkStatus, Popup};
 
@@ -19,11 +23,18 @@ pub struct App {
     pub should_quit: bool,
     pub task_list_scroll: u16,
     pub detail_scroll: u16,
-    pub db: Db,
+    pub db: Arc<Db>,
+    pub api_client: Arc<ApiClient>,
+    sync_tx: mpsc::Sender<SyncCommand>,
+}
+
+pub enum SyncCommand {
+    TriggerSync,
+    Shutdown,
 }
 
 impl App {
-    pub fn new(db: Db) -> Self {
+    pub fn new(db: Arc<Db>, api_client: Arc<ApiClient>, sync_tx: mpsc::Sender<SyncCommand>) -> Self {
         let lists = db.get_lists();
         let tasks = if !lists.is_empty() {
             let list_id = &lists[0].id;
@@ -47,9 +58,15 @@ impl App {
             task_list_scroll: 0,
             detail_scroll: 0,
             db,
+            api_client,
+            sync_tx,
         }
     }
 
+    fn trigger_sync(&self) {
+        let _ = self.sync_tx.try_send(SyncCommand::TriggerSync);
+    }
+
     pub fn handle_key(&mut self, key: KeyEvent) {
         if let Some(ref popup) = self.show_popup.clone() {
             self.handle_popup_key(key, popup);
@@ -167,6 +184,7 @@ impl App {
                                     &list.id,
                                     &serde_json::to_string(&list).unwrap_or_default(),
                                 ).ok();
+                                self.trigger_sync();
                                 self.load_lists();
                             }
                             Focus::TaskList => {
@@ -188,13 +206,14 @@ impl App {
                                         list_id,
                                         &serde_json::to_string(&task).unwrap_or_default(),
                                     ).ok();
+                                    self.trigger_sync();
                                     self.load_tasks();
                                 }
                             }
                             Focus::Detail => {
                                 if !self.tasks.is_empty() {
                                     let task = &mut self.tasks[self.selected_task];
-                            task.title = input;
+                                    task.title = input;
                                     self.db.update_task(task).ok();
                                     self.db.push_sync(
                                         SyncAction::Update,
@@ -202,9 +221,8 @@ impl App {
                                         &task.list_id,
                                         &serde_json::to_string(task).unwrap_or_default(),
                                     ).ok();
+                                    self.trigger_sync();
                                     self.load_tasks();
-                                    if !self.tasks.is_empty() && self.selected_task < self.tasks.len() {
-                                    }
                                 }
                             }
                         }
@@ -257,6 +275,7 @@ impl App {
                             &task.list_id,
                             &serde_json::to_string(task).unwrap_or_default(),
                         ).ok();
+                        self.trigger_sync();
                         self.load_tasks();
                     }
                     self.show_popup = None;
@@ -285,6 +304,7 @@ impl App {
                                     &list_id,
                                     "",
                                 ).ok();
+                                self.trigger_sync();
                                 self.load_lists();
                                 if self.selected_list >= self.lists.len() {
                                     self.selected_list = self.lists.len().saturating_sub(1);
@@ -304,6 +324,7 @@ impl App {
                                     &list_id,
                                     "",
                                 ).ok();
+                                self.trigger_sync();
                                 self.load_tasks();
                                 if self.selected_task >= self.tasks.len() {
                                     self.selected_task = self.tasks.len().saturating_sub(1);
@@ -354,6 +375,7 @@ impl App {
                 &list_id,
                 &payload.to_string(),
             ).ok();
+            self.trigger_sync();
             self.selected_task = new_index as usize;
             self.load_tasks();
         }
diff --git a/src/infrastructure/api.rs b/src/infrastructure/api.rs
index 0116a35..f61b02a 100644
--- a/src/infrastructure/api.rs
+++ b/src/infrastructure/api.rs
@@ -1 +1,431 @@
-// TODO: Fase 5 - Google Tasks API integration
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use chrono::{DateTime, Utc};
+use reqwest::Client;
+use serde::{Deserialize, Serialize};
+use tokio::sync::Mutex;
+use tokio::time::{sleep, Duration};
+
+use crate::domain::models::*;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct OAuthToken {
+    pub access_token: String,
+    pub refresh_token: Option<String>,
+    pub expires_at: Option<DateTime<Utc>>,
+}
+
+#[derive(Debug)]
+pub enum ApiError {
+    Network(String),
+    Auth(String),
+    Api(String),
+}
+
+pub struct ApiClient {
+    client: Client,
+    client_id: String,
+    client_secret: String,
+    token: Arc<Mutex<Option<OAuthToken>>>,
+    token_path: PathBuf,
+}
+
+impl ApiClient {
+    pub fn new(client_id: String, client_secret: String) -> Self {
+        let token_path = dirs::config_dir()
+            .unwrap_or_else(|| PathBuf::from("."))
+            .join("task_app")
+            .join("token.json");
+
+        Self {
+            client: Client::new(),
+            client_id,
+            client_secret,
+            token: Arc::new(Mutex::new(None)),
+            token_path,
+        }
+    }
+
+    pub async fn load_token(&self) -> Option<OAuthToken> {
+        let content = std::fs::read_to_string(&self.token_path).ok()?;
+        serde_json::from_str(&content).ok()
+    }
+
+    pub async fn save_token(&self, token: &OAuthToken) {
+        if let Some(parent) = self.token_path.parent() {
+            std::fs::create_dir_all(parent).ok();
+        }
+        if let Ok(content) = serde_json::to_string_pretty(token) {
+            std::fs::write(&self.token_path, content).ok();
+        }
+    }
+
+    pub async fn authenticate(&self) -> Result<(String, String), ApiError> {
+        let params = serde_json::json!({
+            "client_id": self.client_id,
+            "scope": "https://www.googleapis.com/auth/tasks",
+        });
+
+        let resp = self
+            .client
+            .post("https://oauth2.googleapis.com/device/code")
+            .json(&params)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        let data: serde_json::Value = resp
+            .json()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        let url = data["verification_url"]
+            .as_str()
+            .unwrap_or(&data["verification_url"].to_string())
+            .to_string();
+        let code = data["user_code"]
+            .as_str()
+            .unwrap_or("")
+            .to_string();
+        let device_code = data["device_code"].as_str().unwrap_or("").to_string();
+        let interval = data["interval"].as_u64().unwrap_or(5);
+
+        tokio::spawn({
+            let client = self.client.clone();
+            let client_id = self.client_id.clone();
+            let client_secret = self.client_secret.clone();
+            let device_code = device_code.clone();
+            let token = self.token.clone();
+            let token_path = self.token_path.clone();
+
+            async move {
+                loop {
+                    sleep(Duration::from_secs(interval)).await;
+
+                    let poll = serde_json::json!({
+                        "client_id": client_id,
+                        "client_secret": client_secret,
+                        "device_code": device_code,
+                        "grant_type": "urn:ietf:params:oauth:grant_type:device_code",
+                    });
+
+                    if let Ok(resp) = client
+                        .post("https://oauth2.googleapis.com/token")
+                        .json(&poll)
+                        .send()
+                        .await
+                    {
+                        if let Ok(data) = resp.json::<serde_json::Value>().await {
+                            if let Some(access_token) = data["access_token"].as_str() {
+                                let expires_in = data["expires_in"].as_i64().unwrap_or(3600);
+                                let oauth_token = OAuthToken {
+                                    access_token: access_token.to_string(),
+                                    refresh_token: data["refresh_token"].as_str().map(|s| s.to_string()),
+                                    expires_at: Some(Utc::now() + chrono::Duration::seconds(expires_in)),
+                                };
+
+                                if let Ok(content) = serde_json::to_string_pretty(&oauth_token) {
+                                    std::fs::write(&token_path, content).ok();
+                                }
+
+                                let mut t = token.lock().await;
+                                *t = Some(oauth_token);
+                                break;
+                            }
+                        }
+                    }
+                }
+            }
+        });
+
+        Ok((url, code))
+    }
+
+    pub async fn refresh_access_token(&self, refresh_token: &str) -> Result<(), ApiError> {
+        let params = serde_json::json!({
+            "client_id": self.client_id,
+            "client_secret": self.client_secret,
+            "refresh_token": refresh_token,
+            "grant_type": "refresh_token",
+        });
+
+        let resp = self
+            .client
+            .post("https://oauth2.googleapis.com/token")
+            .json(&params)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        let data: serde_json::Value = resp
+            .json()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        if let Some(access_token) = data["access_token"].as_str() {
+            let expires_in = data["expires_in"].as_i64().unwrap_or(3600);
+            let token = OAuthToken {
+                access_token: access_token.to_string(),
+                refresh_token: Some(refresh_token.to_string()),
+                expires_at: Some(Utc::now() + chrono::Duration::seconds(expires_in)),
+            };
+
+            self.save_token(&token).await;
+            let mut t = self.token.lock().await;
+            *t = Some(token);
+            Ok(())
+        } else {
+            Err(ApiError::Auth("Failed to refresh token".to_string()))
+        }
+    }
+
+    pub async fn ensure_token(&self) -> Result<String, ApiError> {
+        let mut token = self.token.lock().await;
+        if let Some(ref t) = *token {
+            if let Some(expires_at) = t.expires_at {
+                if Utc::now() < expires_at {
+                    return Ok(t.access_token.clone());
+                }
+            }
+            if let Some(ref refresh) = t.refresh_token {
+                let refresh_token = refresh.clone();
+                drop(token);
+                self.refresh_access_token(&refresh_token).await?;
+                let t2 = self.token.lock().await;
+                if let Some(ref t) = *t2 {
+                    return Ok(t.access_token.clone());
+                }
+            }
+            Err(ApiError::Auth("Token expired and no refresh token".to_string()))
+        } else if let Some(saved) = self.load_token().await {
+            *token = Some(saved);
+            if let Some(ref t) = *token {
+                Ok(t.access_token.clone())
+            } else {
+                Err(ApiError::Auth("No token available".to_string()))
+            }
+        } else {
+            Err(ApiError::Auth("Not authenticated".to_string()))
+        }
+    }
+
+    pub async fn fetch_lists(&self) -> Result<Vec<TaskList>, ApiError> {
+        let token = self.ensure_token().await?;
+
+        let resp = self
+            .client
+            .get("https://tasks.googleapis.com/tasks/v1/users/@me/lists")
+            .bearer_auth(&token)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        let data: serde_json::Value = resp
+            .json()
+            .await
+            .map_err(|e| ApiError::Api(e.to_string()))?;
+
+        let empty = vec![];
+        let items = data["items"].as_array().unwrap_or(&empty);
+        let lists = items
+            .iter()
+            .map(|item| TaskList {
+                id: item["id"].as_str().unwrap_or("").to_string(),
+                title: item["title"].as_str().unwrap_or("").to_string(),
+            })
+            .collect();
+
+        Ok(lists)
+    }
+
+    pub async fn fetch_tasks(&self, list_id: &str) -> Result<Vec<Task>, ApiError> {
+        let token = self.ensure_token().await?;
+
+        let url = format!(
+            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks?showCompleted=true&showHidden=true",
+            list_id
+        );
+
+        let resp = self
+            .client
+            .get(&url)
+            .bearer_auth(&token)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        let data: serde_json::Value = resp
+            .json()
+            .await
+            .map_err(|e| ApiError::Api(e.to_string()))?;
+
+        let empty = vec![];
+        let items = data["items"].as_array().unwrap_or(&empty);
+        let tasks = items
+            .iter()
+            .enumerate()
+            .map(|(i, item)| {
+                let due_str = item["due"].as_str().and_then(|s| {
+                    chrono::NaiveDateTime::parse_from_str(
+                        &s.replace("T", " ").replace("Z", "").chars().take(16).collect::<String>(),
+                        "%Y-%m-%d %H:%M",
+                    )
+                    .ok()
+                });
+
+                Task {
+                    id: item["id"].as_str().unwrap_or("").to_string(),
+                    list_id: list_id.to_string(),
+                    title: item["title"].as_str().unwrap_or("").to_string(),
+                    notes: item["notes"].as_str().map(|s| s.to_string()),
+                    status: if item["status"].as_str() == Some("completed") {
+                        TaskStatus::Completed
+                    } else {
+                        TaskStatus::NeedsAction
+                    },
+                    due: due_str,
+                    position: i as i64,
+                }
+            })
+            .collect();
+
+        Ok(tasks)
+    }
+
+    pub async fn create_task(&self, list_id: &str, task: &Task) -> Result<(), ApiError> {
+        let token = self.ensure_token().await?;
+
+        let mut body = serde_json::json!({
+            "title": task.title,
+        });
+
+        if let Some(ref notes) = task.notes {
+            body["notes"] = serde_json::Value::String(notes.clone());
+        }
+        if let Some(due) = task.due {
+            body["due"] = serde_json::Value::String(due.format("%Y-%m-%dT%H:%M:00.000Z").to_string());
+        }
+        if task.status == TaskStatus::Completed {
+            body["status"] = serde_json::Value::String("completed".to_string());
+        }
+
+        let url = format!(
+            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks",
+            list_id
+        );
+
+        let resp = self
+            .client
+            .post(&url)
+            .bearer_auth(&token)
+            .json(&body)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        if !resp.status().is_success() {
+            return Err(ApiError::Api(format!("Create failed: {}", resp.status())));
+        }
+
+        Ok(())
+    }
+
+    pub async fn update_task(&self, list_id: &str, task: &Task) -> Result<(), ApiError> {
+        let token = self.ensure_token().await?;
+
+        let mut body = serde_json::json!({
+            "title": task.title,
+        });
+
+        if let Some(ref notes) = task.notes {
+            body["notes"] = serde_json::Value::String(notes.clone());
+        }
+        if let Some(due) = task.due {
+            body["due"] = serde_json::Value::String(due.format("%Y-%m-%dT%H:%M:00.000Z").to_string());
+        }
+        body["status"] = serde_json::Value::String(match task.status {
+            TaskStatus::Completed => "completed".to_string(),
+            TaskStatus::NeedsAction => "needsAction".to_string(),
+        });
+
+        let url = format!(
+            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}",
+            list_id, task.id
+        );
+
+        let resp = self
+            .client
+            .patch(&url)
+            .bearer_auth(&token)
+            .json(&body)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        if !resp.status().is_success() {
+            return Err(ApiError::Api(format!("Update failed: {}", resp.status())));
+        }
+
+        Ok(())
+    }
+
+    pub async fn delete_task(&self, list_id: &str, task_id: &str) -> Result<(), ApiError> {
+        let token = self.ensure_token().await?;
+
+        let url = format!(
+            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}",
+            list_id, task_id
+        );
+
+        let resp = self
+            .client
+            .delete(&url)
+            .bearer_auth(&token)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        if !resp.status().is_success() {
+            return Err(ApiError::Api(format!("Delete failed: {}", resp.status())));
+        }
+
+        Ok(())
+    }
+
+    pub async fn move_task(
+        &self,
+        list_id: &str,
+        task_id: &str,
+        prev: Option<&str>,
+        sibling: Option<&str>,
+    ) -> Result<(), ApiError> {
+        let token = self.ensure_token().await?;
+
+        let mut url = format!(
+            "https://tasks.googleapis.com/tasks/v1/lists/{}/tasks/{}/move",
+            list_id, task_id
+        );
+
+        if let Some(p) = prev {
+            url.push_str(&format!("&previous={}", p));
+        }
+        if let Some(s) = sibling {
+            url.push_str(&format!("&destinationTaskList={}", s));
+        }
+
+        let resp = self
+            .client
+            .post(&url)
+            .bearer_auth(&token)
+            .send()
+            .await
+            .map_err(|e| ApiError::Network(e.to_string()))?;
+
+        if !resp.status().is_success() {
+            return Err(ApiError::Api(format!("Move failed: {}", resp.status())));
+        }
+
+        Ok(())
+    }
+}
diff --git a/src/infrastructure/db.rs b/src/infrastructure/db.rs
index 0ad54b7..f1c621c 100644
--- a/src/infrastructure/db.rs
+++ b/src/infrastructure/db.rs
@@ -1,10 +1,12 @@
-use rusqlite::{params, Connection, Result as SqlResult};
+use std::sync::Mutex;
+
 use chrono::NaiveDateTime;
+use rusqlite::{params, Connection, Result as SqlResult};
 
 use crate::domain::models::*;
 
 pub struct Db {
-    conn: Connection,
+    conn: Mutex<Connection>,
 }
 
 impl Db {
@@ -38,11 +40,12 @@ impl Db {
                 created_at TEXT NOT NULL
             );",
         )?;
-        Ok(Self { conn })
+        Ok(Self { conn: Mutex::new(conn) })
     }
 
     pub fn get_lists(&self) -> Vec<TaskList> {
-        let mut stmt = self.conn
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn
             .prepare("SELECT id, title FROM task_lists ORDER BY title")
             .unwrap();
         stmt.query_map([], |row| {
@@ -57,7 +60,8 @@ impl Db {
     }
 
     pub fn insert_list(&self, list: &TaskList) -> SqlResult<()> {
-        self.conn.execute(
+        let conn = self.conn.lock().unwrap();
+        conn.execute(
             "INSERT OR REPLACE INTO task_lists (id, title) VALUES (?1, ?2)",
             params![list.id, list.title],
         )?;
@@ -65,13 +69,15 @@ impl Db {
     }
 
     pub fn delete_list(&self, list_id: &str) -> SqlResult<()> {
-        self.conn.execute("DELETE FROM tasks WHERE list_id = ?1", params![list_id])?;
-        self.conn.execute("DELETE FROM task_lists WHERE id = ?1", params![list_id])?;
+        let conn = self.conn.lock().unwrap();
+        conn.execute("DELETE FROM tasks WHERE list_id = ?1", params![list_id])?;
+        conn.execute("DELETE FROM task_lists WHERE id = ?1", params![list_id])?;
         Ok(())
     }
 
     pub fn get_tasks(&self, list_id: &str) -> Vec<Task> {
-        let mut stmt = self.conn
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn
             .prepare(
                 "SELECT id, list_id, title, notes, status, due, position
                  FROM tasks WHERE list_id = ?1 ORDER BY position ASC",
@@ -104,19 +110,18 @@ impl Db {
             TaskStatus::Completed => "completed",
             TaskStatus::NeedsAction => "needsAction",
         };
+        let conn = self.conn.lock().unwrap();
         let position = if task.position == 0 {
-            let max: i64 = self.conn
-                .query_row(
-                    "SELECT COALESCE(MAX(position), -1) + 1 FROM tasks WHERE list_id = ?1",
-                    params![task.list_id],
-                    |row| row.get(0),
-                )
-                .unwrap_or(0);
-            max
+            conn.query_row(
+                "SELECT COALESCE(MAX(position), -1) + 1 FROM tasks WHERE list_id = ?1",
+                params![task.list_id],
+                |row| row.get(0),
+            )
+            .unwrap_or(0)
         } else {
             task.position
         };
-        self.conn.execute(
+        conn.execute(
             "INSERT OR REPLACE INTO tasks (id, list_id, title, notes, status, due, position, updated_at)
              VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8)",
             params![
@@ -139,7 +144,8 @@ impl Db {
             TaskStatus::Completed => "completed",
             TaskStatus::NeedsAction => "needsAction",
         };
-        self.conn.execute(
+        let conn = self.conn.lock().unwrap();
+        conn.execute(
             "UPDATE tasks SET title=?1, notes=?2, status=?3, due=?4, position=?5, updated_at=?6
              WHERE id=?7",
             params![
@@ -156,12 +162,14 @@ impl Db {
     }
 
     pub fn delete_task(&self, task_id: &str) -> SqlResult<()> {
-        self.conn.execute("DELETE FROM tasks WHERE id = ?1", params![task_id])?;
+        let conn = self.conn.lock().unwrap();
+        conn.execute("DELETE FROM tasks WHERE id = ?1", params![task_id])?;
         Ok(())
     }
 
     pub fn reorder_task(&self, task_id: &str, new_position: i64) -> SqlResult<()> {
-        let (old_position, list_id): (i64, String) = self.conn.query_row(
+        let conn = self.conn.lock().unwrap();
+        let (old_position, list_id): (i64, String) = conn.query_row(
             "SELECT position, list_id FROM tasks WHERE id = ?1",
             params![task_id],
             |row| Ok((row.get(0)?, row.get(1)?)),
@@ -172,20 +180,20 @@ impl Db {
         }
 
         if new_position > old_position {
-            self.conn.execute(
+            conn.execute(
                 "UPDATE tasks SET position = position - 1
                  WHERE list_id = ?1 AND position > ?2 AND position <= ?3",
                 params![list_id, old_position, new_position],
             )?;
         } else {
-            self.conn.execute(
+            conn.execute(
                 "UPDATE tasks SET position = position + 1
                  WHERE list_id = ?1 AND position >= ?2 AND position < ?3",
                 params![list_id, new_position, old_position],
             )?;
         }
 
-        self.conn.execute(
+        conn.execute(
             "UPDATE tasks SET position = ?1 WHERE id = ?2",
             params![new_position, task_id],
         )?;
@@ -194,7 +202,9 @@ impl Db {
     }
 
     pub fn replace_all_lists(&self, lists: &[TaskList]) -> SqlResult<()> {
-        self.conn.execute("DELETE FROM task_lists", [])?;
+        let conn = self.conn.lock().unwrap();
+        conn.execute("DELETE FROM task_lists", [])?;
+        drop(conn);
         for list in lists {
             self.insert_list(list)?;
         }
@@ -202,7 +212,9 @@ impl Db {
     }
 
     pub fn replace_all_tasks(&self, list_id: &str, tasks: &[Task]) -> SqlResult<()> {
-        self.conn.execute("DELETE FROM tasks WHERE list_id = ?1", params![list_id])?;
+        let conn = self.conn.lock().unwrap();
+        conn.execute("DELETE FROM tasks WHERE list_id = ?1", params![list_id])?;
+        drop(conn);
         for (i, task) in tasks.iter().enumerate() {
             let mut t = task.clone();
             if t.position == 0 {
@@ -215,8 +227,14 @@ impl Db {
     }
 
     pub fn push_sync(&self, action: SyncAction, task_id: &str, list_id: &str, payload: &str) -> SqlResult<()> {
-        let action_str = serde_json::to_string(&action).unwrap_or_default();
-        self.conn.execute(
+        let action_str = match action {
+            SyncAction::Create => "Create",
+            SyncAction::Update => "Update",
+            SyncAction::Delete => "Delete",
+            SyncAction::Reorder => "Reorder",
+        };
+        let conn = self.conn.lock().unwrap();
+        conn.execute(
             "INSERT INTO sync_queue (action, task_id, list_id, payload, created_at)
              VALUES (?1, ?2, ?3, ?4, ?5)",
             params![
@@ -231,13 +249,20 @@ impl Db {
     }
 
     pub fn drain_sync(&self) -> Vec<SyncQueueItem> {
+        let conn = self.conn.lock().unwrap();
         let items: Vec<SyncQueueItem> = {
-            let mut stmt = self.conn
+            let mut stmt = conn
                 .prepare("SELECT id, action, task_id, list_id, payload, created_at FROM sync_queue ORDER BY id")
                 .unwrap();
             stmt.query_map([], |row| {
                 let action_str: String = row.get(1)?;
-                let action: SyncAction = serde_json::from_str(&action_str).unwrap_or(SyncAction::Update);
+                let action = match action_str.as_str() {
+                    "\"Create\"" | "Create" => SyncAction::Create,
+                    "\"Update\"" | "Update" => SyncAction::Update,
+                    "\"Delete\"" | "Delete" => SyncAction::Delete,
+                    "\"Reorder\"" | "Reorder" => SyncAction::Reorder,
+                    _ => SyncAction::Update,
+                };
                 Ok(SyncQueueItem {
                     id: row.get(0)?,
                     action,
@@ -253,7 +278,7 @@ impl Db {
         };
 
         if !items.is_empty() {
-            self.conn.execute("DELETE FROM sync_queue", []).unwrap();
+            conn.execute("DELETE FROM sync_queue", []).unwrap();
         }
 
         items
diff --git a/src/main.rs b/src/main.rs
index c26e983..013661b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,16 +4,20 @@ mod infrastructure;
 mod ui;
 
 use std::io;
+use std::sync::Arc;
 
 use crossterm::event::{self, Event};
 use crossterm::terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen};
 use crossterm::ExecutableCommand;
 use ratatui::backend::CrosstermBackend;
 use ratatui::Terminal;
+use tokio::sync::Mutex;
 
-use crate::app::App;
+use crate::app::{App, SyncCommand};
+use crate::domain::models::*;
+use crate::infrastructure::api::ApiClient;
 use crate::infrastructure::db::Db;
-use crate::ui::{draw, AppView};
+use crate::ui::{draw, AppView, NetworkStatus};
 
 fn main() -> io::Result<()> {
     let db_path = dirs::data_dir()
@@ -23,7 +27,7 @@ fn main() -> io::Result<()> {
 
     std::fs::create_dir_all(db_path.parent().unwrap()).ok();
 
-    let db = Db::new(db_path.to_str().unwrap()).expect("Failed to open database");
+    let db = Arc::new(Db::new(db_path.to_str().unwrap()).expect("Failed to open database"));
 
     enable_raw_mode()?;
     let mut stdout = io::stdout();
@@ -31,10 +35,35 @@ fn main() -> io::Result<()> {
     let backend = CrosstermBackend::new(stdout);
     let mut terminal = Terminal::new(backend)?;
 
-    let mut app = App::new(db);
+    let api_client = Arc::new(ApiClient::new(
+        std::env::var("GOOGLE_CLIENT_ID").unwrap_or_default(),
+        std::env::var("GOOGLE_CLIENT_SECRET").unwrap_or_default(),
+    ));
+
+    let network_status = Arc::new(Mutex::new(NetworkStatus::Online));
+    let (sync_tx, mut sync_rx) = tokio::sync::mpsc::channel::<SyncCommand>(32);
+
+    let mut app = App::new(db.clone(), api_client.clone(), sync_tx.clone());
+
+    let network_clone = network_status.clone();
+    let db_clone = db.clone();
+    let api_clone = api_client.clone();
+
+    std::thread::spawn(move || {
+        let rt = tokio::runtime::Runtime::new().unwrap();
+        rt.block_on(async move {
+            run_sync_engine(db_clone, api_clone, network_clone, &mut sync_rx).await;
+        });
+    });
 
     while !app.should_quit {
         terminal.draw(|frame| {
+            let status = {
+                let guard = network_status.blocking_lock();
+                guard.clone()
+            };
+            app.network_status = status;
+
             let view = AppView {
                 lists: &app.lists,
                 tasks: &app.tasks,
@@ -61,3 +90,102 @@ fn main() -> io::Result<()> {
     io::stdout().execute(LeaveAlternateScreen)?;
     Ok(())
 }
+
+async fn run_sync_engine(
+    db: Arc<Db>,
+    api: Arc<ApiClient>,
+    network_status: Arc<Mutex<NetworkStatus>>,
+    rx: &mut tokio::sync::mpsc::Receiver<SyncCommand>,
+) {
+    let mut interval = tokio::time::interval(tokio::time::Duration::from_secs(30));
+
+    loop {
+        tokio::select! {
+            _ = interval.tick() => {
+                process_sync_queue(&db, &api, &network_status).await;
+            }
+            cmd = rx.recv() => {
+                match cmd {
+                    Some(SyncCommand::TriggerSync) => {
+                        process_sync_queue(&db, &api, &network_status).await;
+                    }
+                    Some(SyncCommand::Shutdown) | None => break,
+                }
+            }
+        }
+    }
+}
+
+async fn process_sync_queue(
+    db: &Arc<Db>,
+    api: &Arc<ApiClient>,
+    network_status: &Arc<Mutex<NetworkStatus>>,
+) {
+    let token_available = api.load_token().await.is_some();
+    if !token_available {
+        *network_status.lock().await = NetworkStatus::Offline;
+        return;
+    }
+
+    let items = db.drain_sync();
+
+    if items.is_empty() {
+        *network_status.lock().await = NetworkStatus::Online;
+        return;
+    }
+
+    *network_status.lock().await = NetworkStatus::Syncing;
+
+    let mut all_ok = true;
+    for item in &items {
+        let result = match item.action {
+            SyncAction::Create => {
+                let task = serde_json::from_str::<Task>(&item.payload).unwrap_or_else(|_| Task {
+                    id: item.task_id.clone(),
+                    list_id: item.list_id.clone(),
+                    title: String::new(),
+                    notes: None,
+                    status: TaskStatus::NeedsAction,
+                    due: None,
+                    position: 0,
+                });
+                api.create_task(&item.list_id, &task).await
+            }
+            SyncAction::Update => {
+                let task = serde_json::from_str::<Task>(&item.payload).unwrap_or_else(|_| Task {
+                    id: item.task_id.clone(),
+                    list_id: item.list_id.clone(),
+                    title: String::new(),
+                    notes: None,
+                    status: TaskStatus::NeedsAction,
+                    due: None,
+                    position: 0,
+                });
+                api.update_task(&item.list_id, &task).await
+            }
+            SyncAction::Delete => {
+                api.delete_task(&item.list_id, &item.task_id).await
+            }
+            SyncAction::Reorder => {
+                api.move_task(&item.list_id, &item.task_id, None, None).await
+            }
+        };
+
+        if result.is_err() {
+            let _ = db.push_sync(
+                item.action.clone(),
+                &item.task_id,
+                &item.list_id,
+                &item.payload,
+            );
+            all_ok = false;
+            break;
+        }
+    }
+
+    *network_status.lock().await = if all_ok {
+        NetworkStatus::Online
+    } else {
+        NetworkStatus::Offline
+    };
+}