diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 3596376..41e3a1b 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -42,6 +42,7 @@ arboard = "3.6.1"
 # stores it). Must be unconditional, not Linux-only — naming a type from
 # a transitive dep requires the dep be listed here too.
 sqlx = { version = "0.8", features = ["sqlite", "runtime-tokio"] }
+uuid = { version = "1", features = ["v4"] }
 
 [target.'cfg(target_os = "linux")'.dependencies]
 webkit2gtk = "2.0"
diff --git a/src-tauri/src/commands/tasks.rs b/src-tauri/src/commands/tasks.rs
index ab9d659..baf3bd4 100644
--- a/src-tauri/src/commands/tasks.rs
+++ b/src-tauri/src/commands/tasks.rs
@@ -4,10 +4,16 @@
 
 use serde::{Deserialize, Serialize};
 
+use uuid::Uuid;
+
 use kon_storage::{
+    complete_subtask_and_check_parent as db_complete_subtask,
     complete_task as db_complete_task,
     delete_task as db_delete_task,
+    get_task_by_id as db_get_task,
+    insert_subtask as db_insert_subtask,
     insert_task as db_insert_task,
+    list_subtasks as db_list_subtasks,
     list_tasks as db_list_tasks,
     TaskRow,
 };
@@ -115,3 +121,50 @@ pub async fn uncomplete_task_cmd(
         .map(|_| ())
 }
 
+#[tauri::command]
+pub async fn decompose_and_store(
+    state: tauri::State<'_, AppState>,
+    parent_task_id: String,
+) -> Result<Vec<TaskDto>, String> {
+    let parent = db_get_task(&state.db, &parent_task_id)
+        .await
+        .map_err(|e| e.to_string())?
+        .ok_or_else(|| format!("Task {parent_task_id} not found"))?;
+
+    let steps = state.llm_engine.decompose_task(&parent.text)?;
+
+    let mut created = Vec::new();
+    for text in steps {
+        let id = Uuid::new_v4().to_string();
+        db_insert_subtask(&state.db, &id, &text, &parent_task_id)
+            .await
+            .map_err(|e| e.to_string())?;
+        if let Some(row) = db_get_task(&state.db, &id).await.map_err(|e| e.to_string())? {
+            created.push(TaskDto::from(row));
+        }
+    }
+
+    Ok(created)
+}
+
+#[tauri::command]
+pub async fn list_subtasks_cmd(
+    state: tauri::State<'_, AppState>,
+    parent_task_id: String,
+) -> Result<Vec<TaskDto>, String> {
+    db_list_subtasks(&state.db, &parent_task_id)
+        .await
+        .map(|rows| rows.into_iter().map(TaskDto::from).collect())
+        .map_err(|e| e.to_string())
+}
+
+#[tauri::command]
+pub async fn complete_subtask_cmd(
+    state: tauri::State<'_, AppState>,
+    subtask_id: String,
+) -> Result<(), String> {
+    db_complete_subtask(&state.db, &subtask_id)
+        .await
+        .map_err(|e| e.to_string())
+}
+
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 7f187d5..e92b319 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -8,6 +8,7 @@ use sqlx::SqlitePool;
 use tauri::Manager;
 
 use kon_core::types::EngineName;
+use kon_llm::LlmEngine;
 use kon_storage::{database_path, get_setting, init as init_db, set_setting};
 use kon_transcription::LocalEngine;
 
@@ -16,6 +17,7 @@ pub struct AppState {
     pub whisper_engine: Arc<LocalEngine>,
     pub parakeet_engine: Arc<LocalEngine>,
     pub db: SqlitePool,
+    pub llm_engine: Arc<LlmEngine>,
 }
 
 /// Holds the preferences init script for injection into secondary windows.
@@ -214,6 +216,7 @@ pub fn run() {
                     EngineName::new("parakeet"),
                 )),
                 db,
+                llm_engine: Arc::new(LlmEngine::new()),
             });
 
             {
@@ -258,6 +261,9 @@ pub fn run() {
             commands::tasks::complete_task_cmd,
             commands::tasks::delete_task_cmd,
             commands::tasks::uncomplete_task_cmd,
+            commands::tasks::decompose_and_store,
+            commands::tasks::list_subtasks_cmd,
+            commands::tasks::complete_subtask_cmd,
             // Transcripts (canonical SQLite-backed history) — Day 4
             commands::transcripts::add_transcript,
             commands::transcripts::list_transcripts,