Add task branching feature (#15)

2 files changed, 87 insertions, 12 deletions

diff --git a/makima/src/db/models.rs b/makima/src/db/models.rs
index 291fad7..bf95a3a 100644
--- a/makima/src/db/models.rs
+++ b/makima/src/db/models.rs
@@ -519,6 +519,12 @@ pub struct Task {
     /// When the task was last interrupted due to daemon disconnect
     #[serde(skip_serializing_if = "Option::is_none")]
     pub interrupted_at: Option<DateTime<Utc>>,
+
+    // Task branching
+    /// Source task ID when this task was branched from another task's conversation.
+    /// Used to track the origin of "what if" explorations.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub branched_from_task_id: Option<Uuid>,
 }
 
 impl Task {
@@ -598,8 +604,8 @@ pub struct TaskListResponse {
 #[derive(Debug, Deserialize, ToSchema)]
 #[serde(rename_all = "camelCase")]
 pub struct CreateTaskRequest {
-    /// Contract this task belongs to (required)
-    pub contract_id: Uuid,
+    /// Contract this task belongs to (optional for branched/anonymous tasks)
+    pub contract_id: Option<Uuid>,
     /// Name of the task
     pub name: String,
     /// Optional description
@@ -633,6 +639,10 @@ pub struct CreateTaskRequest {
     pub copy_files: Option<Vec<String>>,
     /// Checkpoint SHA to branch from (optional)
     pub checkpoint_sha: Option<String>,
+    /// Source task ID when branching from another task's conversation
+    pub branched_from_task_id: Option<Uuid>,
+    /// Conversation history to initialize the task with (JSON array of messages)
+    pub conversation_history: Option<serde_json::Value>,
 }
 
 /// Request payload for updating a task
@@ -681,6 +691,37 @@ pub struct SendMessageRequest {
     pub message: String,
 }
 
+/// Default for include_conversation field in BranchTaskRequest
+fn default_include_conversation() -> bool {
+    true
+}
+
+/// Request to branch a task from an existing task's conversation.
+/// Creates a new anonymous task that continues from the source task's state.
+#[derive(Debug, Deserialize, ToSchema)]
+#[serde(rename_all = "camelCase")]
+pub struct BranchTaskRequest {
+    /// The initial message/instructions for the branched task
+    pub message: String,
+    /// Optional name for the branched task (auto-generated if not provided)
+    pub name: Option<String>,
+    /// Whether to include conversation history from the source task (default: true)
+    #[serde(default = "default_include_conversation")]
+    pub include_conversation: bool,
+}
+
+/// Response from branching a task.
+#[derive(Debug, Serialize, ToSchema)]
+#[serde(rename_all = "camelCase")]
+pub struct BranchTaskResponse {
+    /// The newly created branched task
+    pub task: Task,
+    /// Number of conversation messages included from source task
+    pub message_count: usize,
+    /// Daemon ID if the task was started (None if no daemon available)
+    pub daemon_id: Option<Uuid>,
+}
+
 // =============================================================================
 // Daemon Types
 // =============================================================================
diff --git a/makima/src/db/repository.rs b/makima/src/db/repository.rs
index 536bc9b..7387735 100644
--- a/makima/src/db/repository.rs
+++ b/makima/src/db/repository.rs
@@ -654,8 +654,8 @@ pub async fn create_task(pool: &PgPool, req: CreateTaskRequest) -> Result<Task,
 
             let new_depth = parent.depth + 1;
 
-            // Subtasks inherit contract_id from parent
-            let contract_id = parent.contract_id.unwrap_or(req.contract_id);
+            // Subtasks inherit contract_id from parent (or use request contract_id if parent has none)
+            let contract_id = parent.contract_id.or(req.contract_id);
 
             // Inherit repo settings if not provided
             let repo_url = req.repository_url.clone().or(parent.repository_url);
@@ -669,7 +669,7 @@ pub async fn create_task(pool: &PgPool, req: CreateTaskRequest) -> Result<Task,
 
             (new_depth, contract_id, repo_url, base_branch, target_branch, merge_mode, target_repo_path, completion_action)
         } else {
-            // Top-level task: depth 0, use contract_id from request
+            // Top-level task: depth 0, use contract_id from request (may be None for branched tasks)
             (
                 0,
                 req.contract_id,
@@ -689,9 +689,10 @@ pub async fn create_task(pool: &PgPool, req: CreateTaskRequest) -> Result<Task,
         INSERT INTO tasks (
             contract_id, parent_task_id, depth, name, description, plan, priority,
             is_supervisor, repository_url, base_branch, target_branch, merge_mode,
-            target_repo_path, completion_action, continue_from_task_id, copy_files
+            target_repo_path, completion_action, continue_from_task_id, copy_files,
+            branched_from_task_id, conversation_state
         )
-        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16)
+        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18)
         RETURNING *
         "#,
     )
@@ -711,6 +712,8 @@ pub async fn create_task(pool: &PgPool, req: CreateTaskRequest) -> Result<Task,
     .bind(&completion_action)
     .bind(&req.continue_from_task_id)
     .bind(&copy_files_json)
+    .bind(&req.branched_from_task_id)
+    .bind(&req.conversation_history)
     .fetch_one(pool)
     .await
 }
@@ -1041,8 +1044,8 @@ pub async fn create_task_for_owner(
                 )));
             }
 
-            // Subtasks inherit contract_id from parent
-            let contract_id = parent.contract_id.unwrap_or(req.contract_id);
+            // Subtasks inherit contract_id from parent (or use request contract_id if parent has none)
+            let contract_id = parent.contract_id.or(req.contract_id);
 
             // Inherit repo settings if not provided
             let repo_url = req.repository_url.clone().or(parent.repository_url);
@@ -1056,7 +1059,7 @@ pub async fn create_task_for_owner(
 
             (new_depth, contract_id, repo_url, base_branch, target_branch, merge_mode, target_repo_path, completion_action)
         } else {
-            // Top-level task: depth 0, use contract_id from request
+            // Top-level task: depth 0, use contract_id from request (may be None for branched tasks)
             (
                 0,
                 req.contract_id,
@@ -1076,9 +1079,10 @@ pub async fn create_task_for_owner(
         INSERT INTO tasks (
             owner_id, contract_id, parent_task_id, depth, name, description, plan, priority,
             is_supervisor, repository_url, base_branch, target_branch, merge_mode,
-            target_repo_path, completion_action, continue_from_task_id, copy_files
+            target_repo_path, completion_action, continue_from_task_id, copy_files,
+            branched_from_task_id, conversation_state
         )
-        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17)
+        VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14, $15, $16, $17, $18, $19)
         RETURNING *
         "#,
     )
@@ -1099,6 +1103,8 @@ pub async fn create_task_for_owner(
     .bind(&completion_action)
     .bind(&req.continue_from_task_id)
     .bind(&copy_files_json)
+    .bind(&req.branched_from_task_id)
+    .bind(&req.conversation_history)
     .fetch_one(pool)
     .await
 }
@@ -3678,3 +3684,31 @@ pub async fn get_supervisor_conversation_full(
 ) -> Result<Option<SupervisorState>, sqlx::Error> {
     get_supervisor_state(pool, contract_id).await
 }
+
+// =============================================================================
+// Anonymous Task Cleanup Functions
+// =============================================================================
+
+/// Delete stale anonymous tasks (tasks with contract_id = NULL) that:
+/// - Are in a terminal state (done, failed, merged)
+/// - Are older than the specified number of days
+///
+/// Returns the number of deleted tasks.
+pub async fn cleanup_stale_anonymous_tasks(
+    pool: &PgPool,
+    max_age_days: i32,
+) -> Result<i64, sqlx::Error> {
+    let result = sqlx::query(
+        r#"
+        DELETE FROM tasks
+        WHERE contract_id IS NULL
+          AND status IN ('done', 'failed', 'merged')
+          AND created_at < NOW() - INTERVAL '1 day' * $1
+        "#,
+    )
+    .bind(max_age_days)
+    .execute(pool)
+    .await?;
+
+    Ok(result.rows_affected() as i64)
+}