Update task status handling to reset runner_id on job cancellation and failure

- Modified SQL queries in multiple functions to set runner_id to NULL when updating task statuses for cancelled jobs and failed tasks.
- Ensured that tasks are properly marked as failed with the correct error messages and updated completion timestamps.
- Improved handling of task statuses to prevent potential issues with task assignment and execution.

internal/manager/jobs.go

@@ -944,7 +944,7 @@ func (s *Manager) handleCancelJob(w http.ResponseWriter, r *http.Request) {
 
 		// Cancel all pending tasks
 		_, err = conn.Exec(
-			`UPDATE tasks SET status = ? WHERE job_id = ? AND status = ?`,
+			`UPDATE tasks SET status = ?, runner_id = NULL WHERE job_id = ? AND status = ?`,
 			types.TaskStatusFailed, jobID, types.TaskStatusPending,
 		)
 		return err
@@ -3024,9 +3024,6 @@ func (s *Manager) handleListJobTasks(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	defer rows.Close()
-	if err != nil {
-		total = -1
-	}
 
 	tasks := []types.Task{}
 	for rows.Next() {

internal/manager/manager.go

@@ -89,6 +89,9 @@ type Manager struct {
 	// Throttling for task status updates (per task)
 	taskUpdateTimes   map[int64]time.Time // key: taskID
 	taskUpdateTimesMu sync.RWMutex
+	// Per-job mutexes to serialize updateJobStatusFromTasks calls and prevent race conditions
+	jobStatusUpdateMu   map[int64]*sync.Mutex // key: jobID
+	jobStatusUpdateMuMu sync.RWMutex
 
 	// Client WebSocket connections (new unified WebSocket)
 	// Key is "userID:connID" to support multiple tabs per user
@@ -162,6 +165,8 @@ func NewManager(db *database.DB, cfg *config.Config, auth *authpkg.Auth, storage
 		runnerJobConns:          make(map[string]*websocket.Conn),
 		runnerJobConnsWriteMu:   make(map[string]*sync.Mutex),
 		runnerJobConnsWriteMuMu: sync.RWMutex{}, // Initialize the new field
+		// Per-job mutexes for serializing status updates
+		jobStatusUpdateMu: make(map[int64]*sync.Mutex),
 	}
 
 	// Check for required external tools

internal/manager/runners.go

@@ -390,7 +390,7 @@ func (s *Manager) handleNextJob(w http.ResponseWriter, r *http.Request) {
 			        t.condition
 			 FROM tasks t
 			 JOIN jobs j ON t.job_id = j.id
-			 WHERE t.status = ? AND j.status != ?
+			 WHERE t.status = ? AND t.runner_id IS NULL AND j.status != ?
 			 ORDER BY t.created_at ASC
 			 LIMIT 50`,
 			types.TaskStatusPending, types.JobStatusCancelled,
@@ -1019,6 +1019,10 @@ func (s *Manager) handleGetJobStatusForRunner(w http.ResponseWriter, r *http.Req
 			&job.CreatedAt, &startedAt, &completedAt, &errorMessage,
 		)
 	})
+	if err == sql.ErrNoRows {
+		s.respondError(w, http.StatusNotFound, "Job not found")
+		return
+	}
 	if err != nil {
 		s.respondError(w, http.StatusInternalServerError, fmt.Sprintf("Failed to query job: %v", err))
 		return
@@ -1037,15 +1041,6 @@ func (s *Manager) handleGetJobStatusForRunner(w http.ResponseWriter, r *http.Req
 		job.OutputFormat = &outputFormat.String
 	}
 
-	if err == sql.ErrNoRows {
-		s.respondError(w, http.StatusNotFound, "Job not found")
-		return
-	}
-	if err != nil {
-		s.respondError(w, http.StatusInternalServerError, fmt.Sprintf("Failed to query job: %v", err))
-		return
-	}
-
 	if startedAt.Valid {
 		job.StartedAt = &startedAt.Time
 	}
@@ -1368,7 +1363,7 @@ func (s *Manager) handleRunnerJobWebSocket(w http.ResponseWriter, r *http.Reques
 			log.Printf("Job WebSocket disconnected unexpectedly for task %d, marking as failed", taskID)
 			s.db.With(func(conn *sql.DB) error {
 				_, err := conn.Exec(
-					`UPDATE tasks SET status = ?, error_message = ?, completed_at = ? WHERE id = ?`,
+					`UPDATE tasks SET status = ?, runner_id = NULL, error_message = ?, completed_at = ? WHERE id = ?`,
 					types.TaskStatusFailed, "WebSocket connection lost", time.Now(), taskID,
 				)
 				return err
@@ -1683,11 +1678,10 @@ func (s *Manager) handleWebSocketTaskComplete(runnerID int64, taskUpdate WSTaskU
 	} else {
 		// No retries remaining - mark as failed
 		err = s.db.WithTx(func(tx *sql.Tx) error {
-			_, err := tx.Exec(`UPDATE tasks SET status = ? WHERE id = ?`, types.TaskStatusFailed, taskUpdate.TaskID)
-			if err != nil {
-				return err
-			}
-			_, err = tx.Exec(`UPDATE tasks SET completed_at = ? WHERE id = ?`, now, taskUpdate.TaskID)
+			_, err := tx.Exec(
+				`UPDATE tasks SET status = ?, runner_id = NULL, completed_at = ? WHERE id = ?`,
+				types.TaskStatusFailed, now, taskUpdate.TaskID,
+			)
 			if err != nil {
 				return err
 			}
@@ -1854,7 +1848,7 @@ func (s *Manager) cancelActiveTasksForJob(jobID int64) error {
 	// Tasks don't have a cancelled status - mark them as failed instead
 	err := s.db.With(func(conn *sql.DB) error {
 		_, err := conn.Exec(
-			`UPDATE tasks SET status = ?, error_message = ? WHERE job_id = ? AND status IN (?, ?)`,
+			`UPDATE tasks SET status = ?, runner_id = NULL, error_message = ? WHERE job_id = ? AND status IN (?, ?)`,
 			types.TaskStatusFailed, "Job cancelled", jobID, types.TaskStatusPending, types.TaskStatusRunning,
 		)
 		if err != nil {
@@ -1920,8 +1914,37 @@ func (s *Manager) evaluateTaskCondition(taskID int64, jobID int64, conditionJSON
 	}
 }
 
+// getJobStatusUpdateMutex returns the mutex for a specific jobID, creating it if needed.
+// This ensures serialized execution of updateJobStatusFromTasks per job to prevent race conditions.
+func (s *Manager) getJobStatusUpdateMutex(jobID int64) *sync.Mutex {
+	s.jobStatusUpdateMuMu.Lock()
+	defer s.jobStatusUpdateMuMu.Unlock()
+
+	mu, exists := s.jobStatusUpdateMu[jobID]
+	if !exists {
+		mu = &sync.Mutex{}
+		s.jobStatusUpdateMu[jobID] = mu
+	}
+	return mu
+}
+
+// cleanupJobStatusUpdateMutex removes the mutex for a jobID after it's no longer needed.
+// Should only be called when the job is in a final state (completed/failed) and no more updates are expected.
+func (s *Manager) cleanupJobStatusUpdateMutex(jobID int64) {
+	s.jobStatusUpdateMuMu.Lock()
+	defer s.jobStatusUpdateMuMu.Unlock()
+	delete(s.jobStatusUpdateMu, jobID)
+}
+
 // updateJobStatusFromTasks updates job status and progress based on task states
+// This function is serialized per jobID to prevent race conditions when multiple tasks
+// complete concurrently and trigger status updates simultaneously.
 func (s *Manager) updateJobStatusFromTasks(jobID int64) {
+	// Serialize updates per job to prevent race conditions
+	mu := s.getJobStatusUpdateMutex(jobID)
+	mu.Lock()
+	defer mu.Unlock()
+
 	now := time.Now()
 
 	// All jobs now use parallel runners (one task per frame), so we always use task-based progress
@@ -2087,6 +2110,11 @@ func (s *Manager) updateJobStatusFromTasks(jobID int64) {
 					"progress":     progress,
 					"completed_at": now,
 				})
+				// Clean up mutex for jobs in final states (completed or failed)
+				// No more status updates will occur for these jobs
+				if jobStatus == string(types.JobStatusCompleted) || jobStatus == string(types.JobStatusFailed) {
+					s.cleanupJobStatusUpdateMutex(jobID)
+				}
 			}
 		}