diff --git a/src/main.rs b/src/main.rs
index c0422b9..bf4d342 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -3,6 +3,7 @@ use crate::app::App;
 mod app;
 mod components;
 mod models;
+mod task;
 mod theme;
 mod view;
 
diff --git a/src/task/error.rs b/src/task/error.rs
new file mode 100644
index 0000000..1d8201d
--- /dev/null
+++ b/src/task/error.rs
@@ -0,0 +1,35 @@
+use std::fmt;
+
+pub enum TaskError {
+    Storage(String),
+    NotFound(uuid::Uuid),
+    InvalidTag(String),
+    InvalidProject(String),
+    InvalidPriority(String),
+    InvalidDue(String),
+    InvalidWait(String),
+    InvalidAnnotation(String),
+    InvalidDependency(String),
+}
+
+impl fmt::Display for TaskError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            TaskError::Storage(msg) => write!(f, "Storage error: {}", msg),
+            TaskError::NotFound(id) => write!(f, "Task not found: {}", id),
+            TaskError::InvalidTag(tag) => write!(f, "Invalid tag: {}", tag),
+            TaskError::InvalidProject(project) => write!(f, "Invalid project: {}", project),
+            TaskError::InvalidPriority(priority) => write!(f, "Invalid priority: {}", priority),
+            TaskError::InvalidDue(due) => write!(f, "Invalid due date: {}", due),
+            TaskError::InvalidWait(wait) => write!(f, "Invalid wait date: {}", wait),
+            TaskError::InvalidAnnotation(annotation) => {
+                write!(f, "Invalid annotation: {}", annotation)
+            }
+            TaskError::InvalidDependency(dependency) => {
+                write!(f, "Invalid dependency: {}", dependency)
+            }
+        }
+    }
+}
+
+pub type TaskResult<T> = Result<T, TaskError>;
diff --git a/src/task/filter.rs b/src/task/filter.rs
new file mode 100644
index 0000000..6926d5b
--- /dev/null
+++ b/src/task/filter.rs
@@ -0,0 +1,266 @@
+use std::collections::HashSet;
+
+use chrono::{DateTime, Utc};
+
+use super::model::{Task, TaskPriority, TaskStatus};
+use crate::models::{DueFilter, FilterState, PriorityFilter, StatusFilter};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum TagsFilterMode {
+    #[default]
+    And,
+    Or,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DueDateFilter {
+    Overdue,
+    Today,
+    ThisWeek,
+    NoDate,
+    Before(DateTime<Utc>),
+    After(DateTime<Utc>),
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct TaskFilter {
+    pub status: Option<TaskStatus>,
+    pub project: Option<String>,
+    pub project_include_children: bool,
+    pub tags: HashSet<String>,
+    pub tags_mode: TagsFilterMode,
+    pub priority: Option<TaskPriority>,
+    pub due_filter: Option<DueDateFilter>,
+    pub search_text: Option<String>,
+    pub is_active: Option<bool>,
+    pub is_blocked: Option<bool>,
+}
+
+impl TaskFilter {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn with_status(mut self, status: TaskStatus) -> Self {
+        self.status = Some(status);
+        self
+    }
+
+    pub fn with_project(mut self, project: String, include_children: bool) -> Self {
+        self.project = Some(project);
+        self.project_include_children = include_children;
+        self
+    }
+
+    pub fn with_tags(mut self, tags: HashSet<String>, mode: TagsFilterMode) -> Self {
+        self.tags = tags;
+        self.tags_mode = mode;
+        self
+    }
+
+    pub fn with_priority(mut self, priority: TaskPriority) -> Self {
+        self.priority = Some(priority);
+        self
+    }
+
+    pub fn with_due(mut self, filter: DueDateFilter) -> Self {
+        self.due_filter = Some(filter);
+        self
+    }
+
+    pub fn with_search(mut self, text: String) -> Self {
+        if !text.is_empty() {
+            self.search_text = Some(text.to_lowercase());
+        }
+        self
+    }
+}
+
+impl From<&FilterState> for TaskFilter {
+    fn from(state: &FilterState) -> Self {
+        let mut filter = Self::new();
+
+        filter.status = match state.status_filter {
+            StatusFilter::All => None,
+            StatusFilter::Pending => Some(TaskStatus::Pending),
+            StatusFilter::Completed => Some(TaskStatus::Completed),
+            StatusFilter::Waiting => Some(TaskStatus::Pending),
+            StatusFilter::Deleted => Some(TaskStatus::Deleted),
+        };
+
+        if let Some(ref project) = state.selected_project {
+            filter.project = Some(project.clone());
+            filter.project_include_children = true;
+        }
+
+        if !state.active_tags.is_empty() {
+            filter.tags = state.active_tags.clone();
+            filter.tags_mode = TagsFilterMode::And;
+        }
+
+        filter.priority = match state.priority_filter {
+            PriorityFilter::All => None,
+            PriorityFilter::High => Some(TaskPriority::High),
+            PriorityFilter::Medium => Some(TaskPriority::Medium),
+            PriorityFilter::Low => Some(TaskPriority::Low),
+            PriorityFilter::None => Some(TaskPriority::None),
+        };
+
+        filter.due_filter = match state.due_filter {
+            DueFilter::All => None,
+            DueFilter::Overdue => Some(DueDateFilter::Overdue),
+            DueFilter::Today => Some(DueDateFilter::Today),
+            DueFilter::ThisWeek => Some(DueDateFilter::ThisWeek),
+            DueFilter::NoDate => Some(DueDateFilter::NoDate),
+        };
+
+        if !state.search_text.is_empty() {
+            filter.search_text = Some(state.search_text.to_lowercase());
+        }
+
+        filter
+    }
+}
+
+impl From<FilterState> for TaskFilter {
+    fn from(state: FilterState) -> Self {
+        Self::from(&state)
+    }
+}
+
+impl TaskFilter {
+    pub fn matches(&self, task: &Task) -> bool {
+        if let Some(status) = &self.status {
+            match status {
+                TaskStatus::Pending => {
+                    if !matches!(task.status, TaskStatus::Pending) {
+                        return false;
+                    }
+                    if task.wait.map(|w| w > Utc::now()).unwrap_or(false) {
+                        return false;
+                    }
+                }
+                _ => {
+                    if &task.status != status {
+                        return false;
+                    }
+                }
+            }
+        }
+
+        if let Some(project) = &self.project {
+            match &task.project {
+                None => return false,
+                Some(task_project) => {
+                    if self.project_include_children {
+                        if !task_project.starts_with(project) {
+                            return false;
+                        }
+                    } else if task_project != project {
+                        return false;
+                    }
+                }
+            }
+        }
+
+        if !self.tags.is_empty() {
+            match self.tags_mode {
+                TagsFilterMode::And => {
+                    for tag in &self.tags {
+                        if !task.tags.contains(tag) {
+                            return false;
+                        }
+                    }
+                }
+                TagsFilterMode::Or => {
+                    let has_any = self.tags.iter().any(|t| task.tags.contains(t));
+                    if !has_any {
+                        return false;
+                    }
+                }
+            }
+        }
+
+        if let Some(priority) = &self.priority {
+            if &task.priority != priority {
+                return false;
+            }
+        }
+
+        if let Some(due_filter) = &self.due_filter {
+            match due_filter {
+                DueDateFilter::Overdue => {
+                    if !task.is_overdue() {
+                        return false;
+                    }
+                }
+                DueDateFilter::Today => {
+                    if !task.is_due_today() {
+                        return false;
+                    }
+                }
+                DueDateFilter::ThisWeek => {
+                    let is_due_this_week = task
+                        .due
+                        .map(|d| {
+                            let now = Utc::now();
+                            let week_end = now + chrono::Duration::days(7);
+                            d >= now && d <= week_end
+                        })
+                        .unwrap_or(false);
+
+                    if !is_due_this_week {
+                        return false;
+                    }
+                }
+                DueDateFilter::NoDate => {
+                    if task.due.is_some() {
+                        return false;
+                    }
+                }
+                DueDateFilter::Before(dt) => {
+                    if task.due.map(|d| d >= *dt).unwrap_or(true) {
+                        return false;
+                    }
+                }
+                DueDateFilter::After(dt) => {
+                    if task.due.map(|d| d <= *dt).unwrap_or(true) {
+                        return false;
+                    }
+                }
+            }
+        }
+
+        if let Some(search) = &self.search_text {
+            let desc_match = task.description.to_lowercase().contains(search);
+            let proj_match = task
+                .project
+                .as_ref()
+                .map(|p| p.to_lowercase().contains(search))
+                .unwrap_or(false);
+            let tag_match = task.tags.iter().any(|t| t.to_lowercase().contains(search));
+
+            if !desc_match && !proj_match && !tag_match {
+                return false;
+            }
+        }
+
+        if let Some(is_active) = self.is_active {
+            if task.is_active != is_active {
+                return false;
+            }
+        }
+
+        if let Some(is_blocked) = self.is_blocked {
+            if task.is_blocked != is_blocked {
+                return false;
+            }
+        }
+
+        true
+    }
+
+    pub fn apply(&self, tasks: &[Task]) -> Vec<Task> {
+        tasks.iter().filter(|t| self.matches(t)).cloned().collect()
+    }
+}
diff --git a/src/task/mod.rs b/src/task/mod.rs
new file mode 100644
index 0000000..a6f1414
--- /dev/null
+++ b/src/task/mod.rs
@@ -0,0 +1,9 @@
+pub mod error;
+pub mod filter;
+pub mod model;
+pub mod service;
+
+pub use error::{TaskError, TaskResult};
+pub use filter::{DueDateFilter, TagsFilterMode, TaskFilter};
+pub use model::{Task, TaskAnnotation, TaskPriority, TaskStatus, TaskUpdate};
+pub use service::{SyncResult, TaskService};
diff --git a/src/task/model.rs b/src/task/model.rs
new file mode 100644
index 0000000..9bcbc04
--- /dev/null
+++ b/src/task/model.rs
@@ -0,0 +1,216 @@
+use std::collections::HashSet;
+
+use chrono::{DateTime, Utc};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum TaskPriority {
+    High,
+    Medium,
+    Low,
+    None,
+}
+
+impl Default for TaskPriority {
+    fn default() -> Self {
+        TaskPriority::None
+    }
+}
+
+impl std::fmt::Display for TaskPriority {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TaskPriority::High => write!(f, "High"),
+            TaskPriority::Medium => write!(f, "Medium"),
+            TaskPriority::Low => write!(f, "Low"),
+            TaskPriority::None => write!(f, "None"),
+        }
+    }
+}
+
+impl From<&str> for TaskPriority {
+    fn from(s: &str) -> Self {
+        match s {
+            "high" | "High" | "H" | "h" => TaskPriority::High,
+            "medium" | "Medium" | "M" | "m" => TaskPriority::Medium,
+            "low" | "Low" | "L" | "l" => TaskPriority::Low,
+            _ => TaskPriority::None,
+        }
+    }
+}
+
+impl From<String> for TaskPriority {
+    fn from(s: String) -> Self {
+        Self::from(s.as_str())
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum TaskStatus {
+    Pending,
+    Completed,
+    Deleted,
+    Unknown(String),
+    Recurring,
+}
+
+impl Default for TaskStatus {
+    fn default() -> Self {
+        TaskStatus::Pending
+    }
+}
+
+impl From<&str> for TaskStatus {
+    fn from(s: &str) -> Self {
+        match s {
+            "pending" | "Pending" | "P" | "p" => TaskStatus::Pending,
+            "completed" | "Completed" | "C" | "c" => TaskStatus::Completed,
+            "deleted" | "Deleted" | "D" | "d" => TaskStatus::Deleted,
+            "recurring" | "Recurring" | "R" | "r" => TaskStatus::Recurring,
+            _ => TaskStatus::Unknown(String::new()),
+        }
+    }
+}
+
+impl From<String> for TaskStatus {
+    fn from(s: String) -> Self {
+        Self::from(s.as_str())
+    }
+}
+
+impl From<taskchampion::Status> for TaskStatus {
+    fn from(status: taskchampion::Status) -> Self {
+        match status {
+            taskchampion::Status::Pending => TaskStatus::Pending,
+            taskchampion::Status::Completed => TaskStatus::Completed,
+            taskchampion::Status::Deleted => TaskStatus::Deleted,
+            taskchampion::Status::Unknown(reason) => TaskStatus::Unknown(reason),
+            taskchampion::Status::Recurring => TaskStatus::Recurring,
+        }
+    }
+}
+
+impl std::fmt::Display for TaskStatus {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            TaskStatus::Pending => write!(f, "Pending"),
+            TaskStatus::Completed => write!(f, "Completed"),
+            TaskStatus::Deleted => write!(f, "Deleted"),
+            TaskStatus::Unknown(reason) => write!(f, "Unknown ({})", reason),
+            TaskStatus::Recurring => write!(f, "Recurring"),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct TaskAnnotation {
+    pub entry: DateTime<Utc>,
+    pub content: String,
+}
+
+impl From<taskchampion::Annotation> for TaskAnnotation {
+    fn from(annotation: taskchampion::Annotation) -> Self {
+        TaskAnnotation {
+            entry: annotation.entry,
+            content: annotation.description,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct Task {
+    pub uuid: uuid::Uuid,
+    pub status: TaskStatus,
+    pub description: String,
+    pub project: Option<String>,
+    pub priority: TaskPriority,
+    pub tags: HashSet<String>,
+    pub due: Option<DateTime<Utc>>,
+    pub wait: Option<DateTime<Utc>>,
+    pub entry: Option<DateTime<Utc>>,
+    pub modified: Option<DateTime<Utc>>,
+    pub annotations: Vec<TaskAnnotation>,
+    pub dependencies: HashSet<uuid::Uuid>,
+    pub is_active: bool,
+    pub is_blocked: bool,
+    pub working_id: Option<usize>,
+}
+
+impl Task {
+    pub fn new(
+        uuid: uuid::Uuid,
+        status: TaskStatus,
+        description: String,
+        project: Option<String>,
+        priority: TaskPriority,
+        tags: HashSet<String>,
+        due: Option<DateTime<Utc>>,
+        wait: Option<DateTime<Utc>>,
+        entry: Option<DateTime<Utc>>,
+        modified: Option<DateTime<Utc>>,
+        annotations: Vec<TaskAnnotation>,
+        dependencies: HashSet<uuid::Uuid>,
+        is_active: bool,
+        is_blocked: bool,
+        working_id: Option<usize>,
+    ) -> Self {
+        Self {
+            uuid,
+            status,
+            description,
+            project,
+            priority,
+            tags,
+            due,
+            wait,
+            entry,
+            modified,
+            annotations,
+            dependencies,
+            is_active,
+            is_blocked,
+            working_id,
+        }
+    }
+
+    pub fn is_overdue(&self) -> bool {
+        self.due.map_or(false, |due| due < Utc::now())
+    }
+
+    pub fn is_due_today(&self) -> bool {
+        self.due
+            .map_or(false, |due| due.date_naive() == Utc::now().date_naive())
+    }
+}
+
+impl From<taskchampion::Task> for Task {
+    fn from(task: taskchampion::Task) -> Self {
+        Self {
+            uuid: task.get_uuid(),
+            status: task.get_status().into(),
+            description: task.get_description().to_string(),
+            project: task.get_value("project").map(|v| v.to_string()),
+            priority: task.get_priority().into(),
+            tags: task.get_tags().map(|t| t.to_string()).collect(),
+            due: task.get_due().map(Into::into),
+            wait: task.get_wait().map(Into::into),
+            entry: task.get_entry().map(Into::into),
+            modified: task.get_modified().map(Into::into),
+            annotations: task.get_annotations().map(Into::into).collect(),
+            dependencies: task.get_dependencies().map(Into::into).collect(),
+            is_active: task.is_active(),
+            is_blocked: task.is_blocked(),
+            working_id: None,
+        }
+    }
+}
+
+pub struct TaskUpdate {
+    pub description: Option<String>,
+    pub project: Option<String>,
+    pub priority: Option<String>,
+    pub tags: Option<HashSet<String>>,
+    pub due: Option<DateTime<Utc>>,
+    pub wait: Option<DateTime<Utc>>,
+    pub annotations: Option<Vec<String>>,
+    pub dependencies: Option<Vec<String>>,
+}
diff --git a/src/task/service.rs b/src/task/service.rs
new file mode 100644
index 0000000..8e494ae
--- /dev/null
+++ b/src/task/service.rs
@@ -0,0 +1,570 @@
+use std::collections::{HashMap, HashSet};
+use std::path::PathBuf;
+
+use chrono::{DateTime, Utc};
+use taskchampion::{
+    Operations, Replica, ServerConfig, Status, StorageConfig, Tag, storage::AccessMode,
+};
+use uuid::Uuid;
+
+use super::error::{TaskError, TaskResult};
+use super::filter::TaskFilter;
+use super::model::{Task, TaskPriority, TaskStatus};
+
+pub struct TaskService {
+    replica: Replica,
+    taskdb_dir: PathBuf,
+}
+
+impl TaskService {
+    pub fn new() -> TaskResult<Self> {
+        let taskdb_dir = dirs::home_dir()
+            .ok_or_else(|| TaskError::Storage("Cannot find home directory".into()))?
+            .join(".task");
+
+        Self::with_path(taskdb_dir)
+    }
+
+    pub fn with_path(taskdb_dir: PathBuf) -> TaskResult<Self> {
+        let storage = StorageConfig::OnDisk {
+            taskdb_dir: taskdb_dir.clone(),
+            create_if_missing: true,
+            access_mode: AccessMode::ReadWrite,
+        };
+
+        let replica = Replica::new(
+            storage
+                .into_storage()
+                .map_err(|e| TaskError::Storage(e.to_string()))?,
+        );
+
+        Ok(Self {
+            replica,
+            taskdb_dir,
+        })
+    }
+
+    pub fn create_task(&mut self, description: String) -> TaskResult<Task> {
+        let uuid = Uuid::new_v4();
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .create_task(uuid, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        tc_task
+            .set_description(description, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        let working_set = self
+            .replica
+            .working_set()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+        let mut task: Task = tc_task.into();
+        task.working_id = working_set.by_uuid(uuid);
+
+        Ok(task)
+    }
+
+    pub fn get_task(&mut self, uuid: Uuid) -> TaskResult<Option<Task>> {
+        let tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        match tc_task {
+            None => Ok(None),
+            Some(task) => {
+                let working_set = self
+                    .replica
+                    .working_set()
+                    .map_err(|e| TaskError::Storage(e.to_string()))?;
+                let mut task: Task = task.into();
+                task.working_id = working_set.by_uuid(uuid);
+                Ok(Some(task))
+            }
+        }
+    }
+
+    pub fn get_all_tasks(&mut self) -> TaskResult<Vec<Task>> {
+        let all = self
+            .replica
+            .all_tasks()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+        let working_set = self
+            .replica
+            .working_set()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        let tasks: Vec<Task> = all
+            .iter()
+            .map(|(uuid, tc_task)| {
+                let mut task: Task = tc_task.clone().into();
+                task.working_id = working_set.by_uuid(*uuid);
+                task
+            })
+            .collect();
+
+        Ok(tasks)
+    }
+
+    pub fn get_filtered_tasks(&mut self, filter: &TaskFilter) -> TaskResult<Vec<Task>> {
+        let all = self.get_all_tasks()?;
+        Ok(filter.apply(&all))
+    }
+
+    pub fn update_task(
+        &mut self,
+        uuid: Uuid,
+        description: Option<String>,
+        project: Option<Option<String>>,
+        priority: Option<String>,
+        tags: Option<HashSet<String>>,
+        due: Option<Option<DateTime<Utc>>>,
+        wait: Option<Option<DateTime<Utc>>>,
+    ) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        if let Some(desc) = description {
+            tc_task
+                .set_description(desc, &mut ops)
+                .map_err(|e| TaskError::Storage(e.to_string()))?;
+        }
+
+        if let Some(proj) = project {
+            tc_task
+                .set_value("project", proj, &mut ops)
+                .map_err(|e| TaskError::Storage(e.to_string()))?;
+        }
+
+        if let Some(pri) = priority {
+            tc_task
+                .set_priority(pri, &mut ops)
+                .map_err(|e| TaskError::Storage(e.to_string()))?;
+        }
+
+        if let Some(d) = due {
+            tc_task
+                .set_due(d, &mut ops)
+                .map_err(|e| TaskError::Storage(e.to_string()))?;
+        }
+
+        if let Some(w) = wait {
+            tc_task
+                .set_wait(w, &mut ops)
+                .map_err(|e| TaskError::Storage(e.to_string()))?;
+        }
+
+        if let Some(new_tags) = tags {
+            let current_tags: HashSet<String> = tc_task.get_tags().map(|t| t.to_string()).collect();
+
+            for tag_str in current_tags.difference(&new_tags) {
+                if let Ok(tag) = Tag::try_from(tag_str.as_str()) {
+                    tc_task
+                        .remove_tag(&tag, &mut ops)
+                        .map_err(|e| TaskError::Storage(e.to_string()))?;
+                }
+            }
+
+            for tag_str in new_tags.difference(&current_tags) {
+                if let Ok(tag) = Tag::try_from(tag_str.as_str()) {
+                    tc_task
+                        .add_tag(&tag, &mut ops)
+                        .map_err(|e| TaskError::Storage(e.to_string()))?;
+                }
+            }
+        }
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn complete_task(&mut self, uuid: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .done(&mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn reopen_task(&mut self, uuid: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .set_status(Status::Pending, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn delete_task(&mut self, uuid: Uuid) -> TaskResult<()> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .set_status(Status::Deleted, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        Ok(())
+    }
+
+    pub fn start_task(&mut self, uuid: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .start(&mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn stop_task(&mut self, uuid: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .stop(&mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn add_tag(&mut self, uuid: Uuid, tag_str: &str) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        let tag = Tag::try_from(tag_str).map_err(|_| TaskError::InvalidTag(tag_str.to_string()))?;
+
+        tc_task
+            .add_tag(&tag, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn remove_tag(&mut self, uuid: Uuid, tag_str: &str) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        let tag = Tag::try_from(tag_str).map_err(|_| TaskError::InvalidTag(tag_str.to_string()))?;
+
+        tc_task
+            .remove_tag(&tag, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn list_tags(&mut self) -> TaskResult<Vec<(String, usize)>> {
+        let all_tasks = self.get_all_tasks()?;
+        let mut tag_counts: HashMap<String, usize> = HashMap::new();
+
+        for task in all_tasks {
+            if matches!(task.status, TaskStatus::Pending) {
+                for tag in task.tags {
+                    *tag_counts.entry(tag).or_insert(0) += 1;
+                }
+            }
+        }
+
+        let mut stats: Vec<(String, usize)> = tag_counts.into_iter().collect();
+
+        stats.sort_by(|a, b| a.0.to_lowercase().cmp(&b.0.to_lowercase()));
+
+        Ok(stats)
+    }
+
+    pub fn list_projects(&mut self) -> TaskResult<Vec<(String, usize, usize)>> {
+        let all_tasks = self.get_all_tasks()?;
+        let mut project_counts: HashMap<String, (usize, usize)> = HashMap::new(); // (total, pending)
+
+        for task in all_tasks {
+            if let Some(project) = &task.project {
+                let entry = project_counts.entry(project.clone()).or_insert((0, 0));
+                entry.0 += 1;
+                if matches!(task.status, TaskStatus::Pending) {
+                    entry.1 += 1;
+                }
+            }
+        }
+
+        let stats: Vec<(String, usize, usize)> = project_counts
+            .into_iter()
+            .map(|(name, (task_count, pending_count))| (name, task_count, pending_count))
+            .collect();
+
+        Ok(stats)
+    }
+
+    pub fn get_projects_for_tree(&mut self) -> TaskResult<Vec<(String, usize)>> {
+        let stats = self.list_projects()?;
+        Ok(stats
+            .into_iter()
+            .map(|(name, _total, pending)| (name, pending))
+            .collect())
+    }
+
+    pub fn add_annotation(&mut self, uuid: Uuid, description: String) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        let annotation = taskchampion::Annotation {
+            entry: Utc::now(),
+            description,
+        };
+
+        tc_task
+            .add_annotation(annotation, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn remove_annotation(&mut self, uuid: Uuid, entry: DateTime<Utc>) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .remove_annotation(entry, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn add_dependency(&mut self, uuid: Uuid, depends_on: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .add_dependency(depends_on, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn remove_dependency(&mut self, uuid: Uuid, depends_on: Uuid) -> TaskResult<Task> {
+        let mut ops = Operations::new();
+
+        let mut tc_task = self
+            .replica
+            .get_task(uuid)
+            .map_err(|e| TaskError::Storage(e.to_string()))?
+            .ok_or(TaskError::NotFound(uuid))?;
+
+        tc_task
+            .remove_dependency(depends_on, &mut ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .commit_operations(ops)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.get_task(uuid)?.ok_or(TaskError::NotFound(uuid))
+    }
+
+    pub fn sync(&mut self) -> TaskResult<SyncResult> {
+        let server_dir = self.taskdb_dir.join("server");
+
+        if !server_dir.exists() {
+            return Ok(SyncResult {
+                success: false,
+                message: "Server not configured".to_string(),
+                local_ops_before: 0,
+                local_ops_after: 0,
+            });
+        }
+
+        let local_ops_before = self
+            .replica
+            .num_local_operations()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        let server_config = ServerConfig::Local { server_dir };
+
+        let mut server = server_config
+            .into_server()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        self.replica
+            .sync(&mut server, false)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        let local_ops_after = self
+            .replica
+            .num_local_operations()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        Ok(SyncResult {
+            success: true,
+            message: "Sync completed".to_string(),
+            local_ops_before,
+            local_ops_after,
+        })
+    }
+
+    pub fn pending_sync_operations(&mut self) -> TaskResult<usize> {
+        Ok(self
+            .replica
+            .num_local_operations()
+            .map_err(|e| TaskError::Storage(e.to_string()))?)
+    }
+
+    pub fn rebuild_working_set(&mut self, renumber: bool) -> TaskResult<()> {
+        self.replica
+            .rebuild_working_set(renumber)
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+        Ok(())
+    }
+
+    pub fn expire_tasks(&mut self) -> TaskResult<()> {
+        self.replica
+            .expire_tasks()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+        Ok(())
+    }
+
+    pub fn working_set(&mut self) -> TaskResult<Vec<(usize, Task)>> {
+        let ws = self
+            .replica
+            .working_set()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+        let mut result = Vec::new();
+
+        for (idx, uuid) in ws.iter() {
+            if let Some(task) = self.get_task(uuid)? {
+                result.push((idx, task));
+            }
+        }
+
+        Ok(result)
+    }
+
+    pub fn get_task_by_working_id(&mut self, id: usize) -> TaskResult<Option<Task>> {
+        let ws = self
+            .replica
+            .working_set()
+            .map_err(|e| TaskError::Storage(e.to_string()))?;
+
+        match ws.by_index(id) {
+            None => Ok(None),
+            Some(uuid) => self.get_task(uuid),
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct SyncResult {
+    pub success: bool,
+    pub message: String,
+    pub local_ops_before: usize,
+    pub local_ops_after: usize,
+}