diff --git a/internal/app/app.go b/internal/app/app.go
index 5ffa4c7..439903f 100644
--- a/internal/app/app.go
+++ b/internal/app/app.go
@@ -197,6 +197,14 @@ type processors struct {
 	recipientProcessor             *processor.RecipientProcessorImpl
 	letterDispositionProcessor     *processor.LetterDispositionProcessorImpl
 	letterDispositionDeptProcessor *processor.LetterDispositionDepartmentProcessorImpl
+	// Modular processors for letter outgoing
+	letterValidationProcessor          processor.LetterValidationProcessor
+	letterCreationProcessor            processor.LetterCreationProcessor
+	letterApprovalProcessor            processor.LetterApprovalProcessor
+	letterAttachmentProcessor          processor.LetterAttachmentProcessor
+	letterOutgoingRecipientProcessor   processor.LetterOutgoingRecipientProcessor
+	letterActivityProcessor            processor.LetterActivityProcessor
+	txManager                          *repository.TxManager
 }
 
 func (a *App) initProcessors(cfg *config.Config, repos *repositories) *processors {
@@ -218,6 +226,31 @@ func (a *App) initProcessors(cfg *config.Config, repos *repositories) *processor
 		letterNumberGen, repos.dispositionRouteRepo,
 	)
 
+	// Create modular processors for letter outgoing
+	letterValidationProc := processor.NewLetterValidationProcessor()
+	letterCreationProc := processor.NewLetterCreationProcessor(
+		repos.letterOutgoingRepo,
+		repos.approvalFlowRepo,
+		letterNumberGen,
+	)
+	letterApprovalProc := processor.NewLetterApprovalProcessor(
+		repos.letterOutgoingApprovalRepo,
+		repos.approvalFlowRepo,
+		repos.letterOutgoingRepo,
+	)
+	letterAttachmentProc := processor.NewLetterAttachmentProcessor(
+		repos.letterOutgoingAttachmentRepo,
+	)
+	letterOutgoingRecipientProc := processor.NewLetterOutgoingRecipientProcessor(
+		repos.letterOutgoingRecipientRepo,
+		repos.approvalFlowRepo,
+		repos.userDeptRepo,
+	)
+	letterActivityProc := processor.NewLetterActivityProcessor(
+		repos.letterOutgoingActivityLogRepo,
+	)
+	
+	// Create the main letter outgoing processor for backward compatibility
 	letterOutgoingProc := processor.NewLetterOutgoingProcessor(
 		a.db,
 		repos.letterOutgoingRepo,
@@ -307,6 +340,14 @@ func (a *App) initProcessors(cfg *config.Config, repos *repositories) *processor
 		recipientProcessor:             recipientProc,
 		letterDispositionProcessor:     letterDispositionProc,
 		letterDispositionDeptProcessor: letterDispositionDeptProc,
+		// Modular processors
+		letterValidationProcessor:        letterValidationProc,
+		letterCreationProcessor:          letterCreationProc,
+		letterApprovalProcessor:          letterApprovalProc,
+		letterAttachmentProcessor:        letterAttachmentProc,
+		letterOutgoingRecipientProcessor: letterOutgoingRecipientProc,
+		letterActivityProcessor:          letterActivityProc,
+		txManager:                        txMgr,
 	}
 }
 
@@ -352,7 +393,16 @@ func (a *App) initServices(processors *processors, repos *repositories, cfg *con
 		processors.activityLogger,
 	)
 	dispRouteSvc := service.NewDispositionRouteService(repos.dispositionRouteRepo)
-	letterOutgoingSvc := service.NewLetterOutgoingService(processors.letterOutgoingProcessor)
+	letterOutgoingSvc := service.NewLetterOutgoingService(
+		processors.letterOutgoingProcessor,
+		processors.txManager,
+		processors.letterValidationProcessor,
+		processors.letterCreationProcessor,
+		processors.letterApprovalProcessor,
+		processors.letterAttachmentProcessor,
+		processors.letterOutgoingRecipientProcessor,
+		processors.letterActivityProcessor,
+	)
 
 	approvalFlowStepRepo := repository.NewApprovalFlowStepRepository(a.db)
 	approvalFlowSvc := service.NewApprovalFlowService(
diff --git a/internal/entities/department.go b/internal/entities/department.go
index e93f7b3..35a65f1 100644
--- a/internal/entities/department.go
+++ b/internal/entities/department.go
@@ -7,12 +7,17 @@ import (
 )
 
 type Department struct {
-	ID        uuid.UUID `gorm:"type:uuid;primary_key;default:gen_random_uuid()" json:"id"`
-	Name      string    `gorm:"not null" json:"name"`
-	Code      string    `json:"code,omitempty"`
-	Path      string    `gorm:"not null" json:"path"`
-	CreatedAt time.Time `gorm:"autoCreateTime" json:"created_at"`
-	UpdatedAt time.Time `gorm:"autoUpdateTime" json:"updated_at"`
+	ID                 uuid.UUID  `gorm:"type:uuid;primary_key;default:gen_random_uuid()" json:"id"`
+	Name               string     `gorm:"not null" json:"name"`
+	Code               string     `json:"code,omitempty"`
+	Path               string     `gorm:"not null" json:"path"`
+	ParentDepartmentID *uuid.UUID `gorm:"type:uuid" json:"parent_department_id,omitempty"`
+	CreatedAt          time.Time  `gorm:"autoCreateTime" json:"created_at"`
+	UpdatedAt          time.Time  `gorm:"autoUpdateTime" json:"updated_at"`
+	
+	// Relations
+	ParentDepartment *Department  `gorm:"foreignKey:ParentDepartmentID" json:"parent_department,omitempty"`
+	ChildDepartments []Department `gorm:"foreignKey:ParentDepartmentID" json:"child_departments,omitempty"`
 }
 
 func (Department) TableName() string { return "departments" }
diff --git a/internal/processor/department_processor.go b/internal/processor/department_processor.go
new file mode 100644
index 0000000..70c4827
--- /dev/null
+++ b/internal/processor/department_processor.go
@@ -0,0 +1,270 @@
+package processor
+
+import (
+	"context"
+	"fmt"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+// DepartmentProcessor handles all department-related business logic
+type DepartmentProcessor interface {
+	Create(ctx context.Context, department *entities.Department) error
+	Get(ctx context.Context, id uuid.UUID) (*entities.Department, error)
+	GetByPath(ctx context.Context, path string) (*entities.Department, error)
+	Update(ctx context.Context, department *entities.Department) error
+	Delete(ctx context.Context, id uuid.UUID) error
+	List(ctx context.Context, search string, limit, offset int) ([]entities.Department, int64, error)
+	
+	// Hierarchy operations
+	GetChildren(ctx context.Context, parentID uuid.UUID) ([]entities.Department, error)
+	GetAllDescendants(ctx context.Context, parentID uuid.UUID) ([]entities.Department, error)
+	UpdateChildrenPaths(ctx context.Context, oldPath, newPath string) error
+	ValidateHierarchy(ctx context.Context, departmentID, newParentID uuid.UUID) error
+	
+	// Tree building operations
+	GetDepartmentWithDescendants(ctx context.Context, departmentID uuid.UUID) ([]entities.Department, error)
+	GetDepartmentWithParentAndSiblings(ctx context.Context, departmentID uuid.UUID) ([]entities.Department, error)
+	GetAllDepartments(ctx context.Context) ([]entities.Department, error)
+	GetDepartmentsByRootPath(ctx context.Context, rootPath string) ([]entities.Department, error)
+}
+
+type DepartmentProcessorImpl struct {
+	departmentRepo *repository.DepartmentRepository
+	txManager      *repository.TxManager
+}
+
+// NewDepartmentProcessor creates a new department processor
+func NewDepartmentProcessor(
+	departmentRepo *repository.DepartmentRepository,
+	txManager *repository.TxManager,
+) *DepartmentProcessorImpl {
+	return &DepartmentProcessorImpl{
+		departmentRepo: departmentRepo,
+		txManager:      txManager,
+	}
+}
+
+// Create creates a new department
+func (p *DepartmentProcessorImpl) Create(ctx context.Context, department *entities.Department) error {
+	// Build path based on parent
+	if department.ParentDepartmentID != nil && *department.ParentDepartmentID != uuid.Nil {
+		parent, err := p.departmentRepo.GetByID(ctx, *department.ParentDepartmentID)
+		if err != nil {
+			return fmt.Errorf("parent department not found: %w", err)
+		}
+		department.Path = parent.Path + "." + department.Code
+	} else {
+		department.Path = department.Code
+	}
+	
+	return p.departmentRepo.Create(ctx, department)
+}
+
+// Get retrieves a department by ID
+func (p *DepartmentProcessorImpl) Get(ctx context.Context, id uuid.UUID) (*entities.Department, error) {
+	return p.departmentRepo.Get(ctx, id)
+}
+
+// GetByPath retrieves a department by its path
+func (p *DepartmentProcessorImpl) GetByPath(ctx context.Context, path string) (*entities.Department, error) {
+	return p.departmentRepo.GetByPath(ctx, path)
+}
+
+// Update updates a department with hierarchy validation
+func (p *DepartmentProcessorImpl) Update(ctx context.Context, department *entities.Department) error {
+	return p.txManager.WithTransaction(ctx, func(txCtx context.Context) error {
+		// Get the current department state
+		current, err := p.departmentRepo.Get(txCtx, department.ID)
+		if err != nil {
+			return err
+		}
+		
+		// Store old values for comparison
+		oldPath := current.Path
+		oldParentID := current.ParentDepartmentID
+		pathChanged := false
+		
+		// Update path if parent or code changed
+		if department.ParentDepartmentID != oldParentID || department.Code != current.Code {
+			// Rebuild path
+			if department.ParentDepartmentID == nil {
+				department.Path = department.Code
+			} else {
+				parent, err := p.departmentRepo.GetByID(txCtx, *department.ParentDepartmentID)
+				if err != nil {
+					return fmt.Errorf("parent department not found: %w", err)
+				}
+				department.Path = parent.Path + "." + department.Code
+			}
+			
+			if department.Path != oldPath {
+				pathChanged = true
+			}
+		}
+		
+		// Update the department
+		if err := p.departmentRepo.Update(txCtx, department); err != nil {
+			return err
+		}
+		
+		// Update children paths if necessary
+		if pathChanged {
+			if err := p.updateChildrenPathsRecursively(txCtx, department.ID, department.Path); err != nil {
+				return fmt.Errorf("failed to update children paths: %w", err)
+			}
+		}
+		
+		return nil
+	})
+}
+
+// Delete deletes a department
+func (p *DepartmentProcessorImpl) Delete(ctx context.Context, id uuid.UUID) error {
+	return p.departmentRepo.Delete(ctx, id)
+}
+
+// List lists departments with pagination
+func (p *DepartmentProcessorImpl) List(ctx context.Context, search string, limit, offset int) ([]entities.Department, int64, error) {
+	return p.departmentRepo.List(ctx, search, limit, offset)
+}
+
+// GetChildren gets direct children of a department
+func (p *DepartmentProcessorImpl) GetChildren(ctx context.Context, parentID uuid.UUID) ([]entities.Department, error) {
+	// First get the parent department to get its path
+	parent, err := p.departmentRepo.Get(ctx, parentID)
+	if err != nil {
+		return nil, err
+	}
+	if parent == nil {
+		return []entities.Department{}, nil
+	}
+	return p.departmentRepo.GetChildren(ctx, parent.Path)
+}
+
+// GetAllDescendants gets all descendants of a department
+func (p *DepartmentProcessorImpl) GetAllDescendants(ctx context.Context, parentID uuid.UUID) ([]entities.Department, error) {
+	return p.departmentRepo.GetAllDescendants(ctx, parentID)
+}
+
+// UpdateChildrenPaths updates paths for all children
+func (p *DepartmentProcessorImpl) UpdateChildrenPaths(ctx context.Context, oldPath, newPath string) error {
+	return p.departmentRepo.UpdateChildrenPaths(ctx, oldPath, newPath)
+}
+
+// ValidateHierarchy validates that setting newParentID won't create circular references
+func (p *DepartmentProcessorImpl) ValidateHierarchy(ctx context.Context, departmentID, newParentID uuid.UUID) error {
+	// Can't be its own parent
+	if departmentID == newParentID {
+		return fmt.Errorf("department cannot be its own parent")
+	}
+	
+	// Check if new parent is a descendant
+	descendants, err := p.GetAllDescendants(ctx, departmentID)
+	if err != nil {
+		return fmt.Errorf("failed to check descendants: %w", err)
+	}
+	
+	for _, desc := range descendants {
+		if desc.ID == newParentID {
+			return fmt.Errorf("cannot set a descendant as parent (circular reference)")
+		}
+	}
+	
+	return nil
+}
+
+// GetDepartmentWithDescendants gets a department and all its descendants
+func (p *DepartmentProcessorImpl) GetDepartmentWithDescendants(ctx context.Context, departmentID uuid.UUID) ([]entities.Department, error) {
+	// Get the department
+	dept, err := p.departmentRepo.Get(ctx, departmentID)
+	if err != nil {
+		return nil, err
+	}
+	
+	departments := []entities.Department{*dept}
+	
+	// Get all descendants
+	descendants, err := p.departmentRepo.GetAllDescendants(ctx, departmentID)
+	if err == nil {
+		departments = append(departments, descendants...)
+	}
+	
+	return departments, nil
+}
+
+// GetDepartmentWithParentAndSiblings gets a department with its parent and all siblings
+func (p *DepartmentProcessorImpl) GetDepartmentWithParentAndSiblings(ctx context.Context, departmentID uuid.UUID) ([]entities.Department, error) {
+	// Get the department
+	dept, err := p.departmentRepo.Get(ctx, departmentID)
+	if err != nil {
+		return nil, err
+	}
+	
+	var departments []entities.Department
+	
+	// If has parent, get parent and all its descendants
+	if dept.ParentDepartmentID != nil {
+		parent, err := p.departmentRepo.Get(ctx, *dept.ParentDepartmentID)
+		if err == nil {
+			departments = append(departments, *parent)
+			
+			// Get all descendants of parent (includes siblings)
+			descendants, err := p.departmentRepo.GetAllDescendants(ctx, parent.ID)
+			if err == nil {
+				departments = append(departments, descendants...)
+			}
+		} else {
+			// Fallback to just department and its descendants
+			return p.GetDepartmentWithDescendants(ctx, departmentID)
+		}
+	} else {
+		// No parent, just get department and descendants
+		return p.GetDepartmentWithDescendants(ctx, departmentID)
+	}
+	
+	return departments, nil
+}
+
+// GetAllDepartments gets all departments in the system
+func (p *DepartmentProcessorImpl) GetAllDepartments(ctx context.Context) ([]entities.Department, error) {
+	departments, _, err := p.departmentRepo.List(ctx, "", 0, 0)
+	return departments, err
+}
+
+// GetDepartmentsByRootPath gets departments starting from a specific path
+func (p *DepartmentProcessorImpl) GetDepartmentsByRootPath(ctx context.Context, rootPath string) ([]entities.Department, error) {
+	// Find the root department
+	rootDept, err := p.departmentRepo.GetByPath(ctx, rootPath)
+	if err != nil {
+		return nil, err
+	}
+	
+	return p.GetDepartmentWithDescendants(ctx, rootDept.ID)
+}
+
+// updateChildrenPathsRecursively updates paths for all children recursively
+func (p *DepartmentProcessorImpl) updateChildrenPathsRecursively(ctx context.Context, parentID uuid.UUID, parentPath string) error {
+	children, err := p.departmentRepo.GetChildren(ctx, parentPath)
+	if err != nil {
+		return err
+	}
+	
+	for _, child := range children {
+		// Update child's path
+		child.Path = parentPath + "." + child.Code
+		if err := p.departmentRepo.Update(ctx, &child); err != nil {
+			return err
+		}
+		
+		// Recursively update grandchildren
+		if err := p.updateChildrenPathsRecursively(ctx, child.ID, child.Path); err != nil {
+			return err
+		}
+	}
+	
+	return nil
+}
\ No newline at end of file
diff --git a/internal/processor/letter_activity_processor.go b/internal/processor/letter_activity_processor.go
new file mode 100644
index 0000000..714e74a
--- /dev/null
+++ b/internal/processor/letter_activity_processor.go
@@ -0,0 +1,52 @@
+package processor
+
+import (
+	"context"
+	"time"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+type LetterActivityProcessor interface {
+	LogActivity(ctx context.Context, letterID uuid.UUID, action string, userID uuid.UUID, details map[string]interface{}) error
+	LogStatusChange(ctx context.Context, letterID uuid.UUID, fromStatus, toStatus string, userID uuid.UUID) error
+	GetActivitiesByLetterID(ctx context.Context, letterID uuid.UUID) ([]entities.LetterOutgoingActivityLog, error)
+}
+
+type LetterActivityProcessorImpl struct {
+	activityLogRepo *repository.LetterOutgoingActivityLogRepository
+}
+
+func NewLetterActivityProcessor(activityLogRepo *repository.LetterOutgoingActivityLogRepository) *LetterActivityProcessorImpl {
+	return &LetterActivityProcessorImpl{
+		activityLogRepo: activityLogRepo,
+	}
+}
+
+func (p *LetterActivityProcessorImpl) LogActivity(ctx context.Context, letterID uuid.UUID, action string, userID uuid.UUID, details map[string]interface{}) error {
+	log := &entities.LetterOutgoingActivityLog{
+		LetterID:      letterID,
+		ActionType:    action,
+		ActorUserID:   &userID,
+		Context:       details,
+		OccurredAt:    time.Now(),
+	}
+
+	return p.activityLogRepo.Create(ctx, log)
+}
+
+func (p *LetterActivityProcessorImpl) LogStatusChange(ctx context.Context, letterID uuid.UUID, fromStatus, toStatus string, userID uuid.UUID) error {
+	details := map[string]interface{}{
+		"from_status": fromStatus,
+		"to_status":   toStatus,
+	}
+
+	return p.LogActivity(ctx, letterID, "status_changed", userID, details)
+}
+
+func (p *LetterActivityProcessorImpl) GetActivitiesByLetterID(ctx context.Context, letterID uuid.UUID) ([]entities.LetterOutgoingActivityLog, error) {
+	return p.activityLogRepo.ListByLetter(ctx, letterID)
+}
\ No newline at end of file
diff --git a/internal/processor/letter_approval_processor.go b/internal/processor/letter_approval_processor.go
new file mode 100644
index 0000000..dfcb7a8
--- /dev/null
+++ b/internal/processor/letter_approval_processor.go
@@ -0,0 +1,113 @@
+package processor
+
+import (
+	"context"
+	"time"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+type LetterApprovalProcessor interface {
+	CreateApprovalSteps(ctx context.Context, letter *entities.LetterOutgoing) error
+	ProcessApprovalAction(ctx context.Context, letterID uuid.UUID, approval *entities.LetterOutgoingApproval, userID uuid.UUID, isApproval bool) error
+	UpdateApprovalStatus(ctx context.Context, approval *entities.LetterOutgoingApproval, status entities.ApprovalStatus, userID uuid.UUID) error
+	CheckAllApprovalsComplete(ctx context.Context, letterID uuid.UUID) (bool, error)
+}
+
+type LetterApprovalProcessorImpl struct {
+	approvalRepo     *repository.LetterOutgoingApprovalRepository
+	approvalFlowRepo *repository.ApprovalFlowRepository
+	letterRepo       *repository.LetterOutgoingRepository
+}
+
+func NewLetterApprovalProcessor(
+	approvalRepo *repository.LetterOutgoingApprovalRepository,
+	approvalFlowRepo *repository.ApprovalFlowRepository,
+	letterRepo *repository.LetterOutgoingRepository,
+) *LetterApprovalProcessorImpl {
+	return &LetterApprovalProcessorImpl{
+		approvalRepo:     approvalRepo,
+		approvalFlowRepo: approvalFlowRepo,
+		letterRepo:       letterRepo,
+	}
+}
+
+func (p *LetterApprovalProcessorImpl) CreateApprovalSteps(ctx context.Context, letter *entities.LetterOutgoing) error {
+	if letter.ApprovalFlowID == nil {
+		return nil
+	}
+
+	flow, err := p.approvalFlowRepo.Get(ctx, *letter.ApprovalFlowID)
+	if err != nil || flow == nil || len(flow.Steps) == 0 {
+		return err
+	}
+
+	// Find the minimum step order (first step)
+	minStepOrder := flow.Steps[0].StepOrder
+	for _, step := range flow.Steps {
+		if step.StepOrder < minStepOrder {
+			minStepOrder = step.StepOrder
+		}
+	}
+
+	// Create approval records for each step
+	for _, step := range flow.Steps {
+		approval := entities.LetterOutgoingApproval{
+			LetterID:      letter.ID,
+			StepID:        step.ID,
+			StepOrder:     step.StepOrder,
+			ParallelGroup: step.ParallelGroup,
+			IsRequired:    step.Required,
+			ApproverID:    step.ApproverUserID,
+		}
+
+		// Set initial status
+		if step.StepOrder == minStepOrder {
+			approval.Status = entities.ApprovalStatusPending
+		} else {
+			approval.Status = entities.ApprovalStatusNotStarted
+		}
+
+		if err := p.approvalRepo.Create(ctx, &approval); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (p *LetterApprovalProcessorImpl) ProcessApprovalAction(ctx context.Context, letterID uuid.UUID, approval *entities.LetterOutgoingApproval, userID uuid.UUID, isApproval bool) error {
+	status := entities.ApprovalStatusApproved
+	if !isApproval {
+		status = entities.ApprovalStatusRejected
+	}
+
+	return p.UpdateApprovalStatus(ctx, approval, status, userID)
+}
+
+func (p *LetterApprovalProcessorImpl) UpdateApprovalStatus(ctx context.Context, approval *entities.LetterOutgoingApproval, status entities.ApprovalStatus, userID uuid.UUID) error {
+	approval.Status = status
+	approval.ApproverID = &userID
+	now := time.Now()
+	approval.ActedAt = &now
+
+	return p.approvalRepo.Update(ctx, approval)
+}
+
+func (p *LetterApprovalProcessorImpl) CheckAllApprovalsComplete(ctx context.Context, letterID uuid.UUID) (bool, error) {
+	approvals, err := p.approvalRepo.ListByLetter(ctx, letterID)
+	if err != nil {
+		return false, err
+	}
+
+	for _, approval := range approvals {
+		if approval.IsRequired && approval.Status != entities.ApprovalStatusApproved {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
\ No newline at end of file
diff --git a/internal/processor/letter_attachment_processor.go b/internal/processor/letter_attachment_processor.go
new file mode 100644
index 0000000..3ec7ead
--- /dev/null
+++ b/internal/processor/letter_attachment_processor.go
@@ -0,0 +1,54 @@
+package processor
+
+import (
+	"context"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+type LetterAttachmentProcessor interface {
+	CreateAttachments(ctx context.Context, letterID uuid.UUID, attachments []entities.LetterOutgoingAttachment) error
+	RemoveAttachment(ctx context.Context, letterID uuid.UUID, attachmentID uuid.UUID) error
+	GetAttachmentsByLetterID(ctx context.Context, letterID uuid.UUID) ([]entities.LetterOutgoingAttachment, error)
+}
+
+type LetterAttachmentProcessorImpl struct {
+	attachmentRepo *repository.LetterOutgoingAttachmentRepository
+}
+
+func NewLetterAttachmentProcessor(attachmentRepo *repository.LetterOutgoingAttachmentRepository) *LetterAttachmentProcessorImpl {
+	return &LetterAttachmentProcessorImpl{
+		attachmentRepo: attachmentRepo,
+	}
+}
+
+func (p *LetterAttachmentProcessorImpl) CreateAttachments(ctx context.Context, letterID uuid.UUID, attachments []entities.LetterOutgoingAttachment) error {
+	if len(attachments) == 0 {
+		return nil
+	}
+
+	// Set letter ID for all attachments
+	for i := range attachments {
+		attachments[i].LetterID = letterID
+	}
+
+	return p.attachmentRepo.CreateBulk(ctx, attachments)
+}
+
+func (p *LetterAttachmentProcessorImpl) RemoveAttachment(ctx context.Context, letterID uuid.UUID, attachmentID uuid.UUID) error {
+	return p.attachmentRepo.Delete(ctx, attachmentID)
+}
+
+func (p *LetterAttachmentProcessorImpl) GetAttachmentsByLetterID(ctx context.Context, letterID uuid.UUID) ([]entities.LetterOutgoingAttachment, error) {
+	attachmentMap, err := p.attachmentRepo.ListByLetterIDs(ctx, []uuid.UUID{letterID})
+	if err != nil {
+		return nil, err
+	}
+	if attachments, ok := attachmentMap[letterID]; ok {
+		return attachments, nil
+	}
+	return []entities.LetterOutgoingAttachment{}, nil
+}
\ No newline at end of file
diff --git a/internal/processor/letter_creation_processor.go b/internal/processor/letter_creation_processor.go
new file mode 100644
index 0000000..419a125
--- /dev/null
+++ b/internal/processor/letter_creation_processor.go
@@ -0,0 +1,72 @@
+package processor
+
+import (
+	"context"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+type LetterCreationProcessor interface {
+	PrepareLetterForCreation(ctx context.Context, letter *entities.LetterOutgoing, departmentID uuid.UUID) error
+	CreateLetter(ctx context.Context, letter *entities.LetterOutgoing) error
+	GenerateLetterNumber(ctx context.Context, letter *entities.LetterOutgoing) error
+}
+
+type LetterCreationProcessorImpl struct {
+	letterRepo       *repository.LetterOutgoingRepository
+	approvalFlowRepo *repository.ApprovalFlowRepository
+	numberGenerator  LetterNumberGenerator
+}
+
+func NewLetterCreationProcessor(
+	letterRepo *repository.LetterOutgoingRepository,
+	approvalFlowRepo *repository.ApprovalFlowRepository,
+	numberGenerator LetterNumberGenerator,
+) *LetterCreationProcessorImpl {
+	return &LetterCreationProcessorImpl{
+		letterRepo:       letterRepo,
+		approvalFlowRepo: approvalFlowRepo,
+		numberGenerator:  numberGenerator,
+	}
+}
+
+func (p *LetterCreationProcessorImpl) PrepareLetterForCreation(ctx context.Context, letter *entities.LetterOutgoing, departmentID uuid.UUID) error {
+	// Assign approval flow from department if not provided
+	if letter.ApprovalFlowID == nil && departmentID != uuid.Nil {
+		flow, err := p.approvalFlowRepo.GetByDepartment(ctx, departmentID)
+		if err == nil && flow != nil {
+			letter.ApprovalFlowID = &flow.ID
+		}
+	}
+
+	// Set initial status based on approval flow
+	if letter.ApprovalFlowID != nil {
+		letter.Status = entities.LetterOutgoingStatusPendingApproval
+	} else {
+		letter.Status = entities.LetterOutgoingStatusApproved
+	}
+
+	return nil
+}
+
+func (p *LetterCreationProcessorImpl) CreateLetter(ctx context.Context, letter *entities.LetterOutgoing) error {
+	return p.letterRepo.Create(ctx, letter)
+}
+
+func (p *LetterCreationProcessorImpl) GenerateLetterNumber(ctx context.Context, letter *entities.LetterOutgoing) error {
+	letterNumber, err := p.numberGenerator.GenerateNumber(
+		ctx,
+		"outgoing_letter_prefix",
+		"outgoing_letter_sequence",
+		"ESLO",
+	)
+	if err != nil {
+		return err
+	}
+
+	letter.LetterNumber = letterNumber
+	return nil
+}
\ No newline at end of file
diff --git a/internal/processor/letter_outgoing_recipient_processor.go b/internal/processor/letter_outgoing_recipient_processor.go
new file mode 100644
index 0000000..76423cd
--- /dev/null
+++ b/internal/processor/letter_outgoing_recipient_processor.go
@@ -0,0 +1,221 @@
+package processor
+
+import (
+	"context"
+
+	"eslogad-be/internal/entities"
+	"eslogad-be/internal/repository"
+
+	"github.com/google/uuid"
+)
+
+// LetterOutgoingRecipientProcessor handles all recipient-related operations for outgoing letters
+type LetterOutgoingRecipientProcessor interface {
+	// CreateRecipients creates multiple recipients for a letter
+	CreateRecipients(ctx context.Context, letterID uuid.UUID, recipients []entities.LetterOutgoingRecipient) error
+	
+	// CreateInitialRecipients creates recipients from both approval workflow and department members
+	CreateInitialRecipients(ctx context.Context, letter *entities.LetterOutgoing, creatorDepartmentID uuid.UUID) error
+	
+	// UpdateRecipient updates a single recipient's information
+	UpdateRecipient(ctx context.Context, recipient *entities.LetterOutgoingRecipient) error
+	
+	// RemoveRecipient removes a recipient from a letter
+	RemoveRecipient(ctx context.Context, letterID uuid.UUID, recipientID uuid.UUID) error
+	
+	// GetRecipientsByLetterID retrieves all recipients for a specific letter
+	GetRecipientsByLetterID(ctx context.Context, letterID uuid.UUID) ([]entities.LetterOutgoingRecipient, error)
+}
+
+type LetterOutgoingRecipientProcessorImpl struct {
+	recipientRepo    *repository.LetterOutgoingRecipientRepository
+	approvalFlowRepo *repository.ApprovalFlowRepository
+	userDeptRepo     *repository.UserDepartmentRepository
+}
+
+func NewLetterOutgoingRecipientProcessor(
+	recipientRepo *repository.LetterOutgoingRecipientRepository,
+	approvalFlowRepo *repository.ApprovalFlowRepository,
+	userDeptRepo *repository.UserDepartmentRepository,
+) *LetterOutgoingRecipientProcessorImpl {
+	return &LetterOutgoingRecipientProcessorImpl{
+		recipientRepo:    recipientRepo,
+		approvalFlowRepo: approvalFlowRepo,
+		userDeptRepo:     userDeptRepo,
+	}
+}
+
+// CreateRecipients creates multiple recipients for a letter
+func (p *LetterOutgoingRecipientProcessorImpl) CreateRecipients(
+	ctx context.Context, 
+	letterID uuid.UUID, 
+	recipients []entities.LetterOutgoingRecipient,
+) error {
+	if len(recipients) == 0 {
+		return nil
+	}
+
+	// Ensure all recipients have the correct letter ID and default status
+	for i := range recipients {
+		recipients[i].LetterID = letterID
+		if recipients[i].Status == "" {
+			recipients[i].Status = "pending"
+		}
+	}
+
+	return p.recipientRepo.CreateBulk(ctx, recipients)
+}
+
+// CreateInitialRecipients creates the initial set of recipients for an outgoing letter
+// It combines:
+// 1. Approvers from the approval workflow (if exists)
+// 2. All active users from the letter creator's department
+func (p *LetterOutgoingRecipientProcessorImpl) CreateInitialRecipients(
+	ctx context.Context, 
+	letter *entities.LetterOutgoing, 
+	creatorDepartmentID uuid.UUID,
+) error {
+	// Track unique users to avoid duplicates
+	uniqueUsers := make(map[uuid.UUID]bool)
+	var allRecipients []entities.LetterOutgoingRecipient
+
+	// Step 1: Add recipients from approval workflow
+	approvalRecipients := p.collectApprovalWorkflowRecipients(ctx, letter, uniqueUsers)
+	allRecipients = append(allRecipients, approvalRecipients...)
+
+	// Step 2: Add all users from the creator's department
+	departmentRecipients := p.collectDepartmentRecipients(ctx, letter.ID, creatorDepartmentID, uniqueUsers)
+	allRecipients = append(allRecipients, departmentRecipients...)
+
+	// Step 3: Mark the first recipient as primary and save all
+	if len(allRecipients) > 0 {
+		allRecipients[0].IsPrimary = true
+		return p.recipientRepo.CreateBulk(ctx, allRecipients)
+	}
+
+	return nil
+}
+
+// collectApprovalWorkflowRecipients gathers all users who are approvers in the workflow
+func (p *LetterOutgoingRecipientProcessorImpl) collectApprovalWorkflowRecipients(
+	ctx context.Context,
+	letter *entities.LetterOutgoing,
+	existingUsers map[uuid.UUID]bool,
+) []entities.LetterOutgoingRecipient {
+	var recipients []entities.LetterOutgoingRecipient
+	
+	// If no approval workflow is assigned, return empty
+	if letter.ApprovalFlowID == nil {
+		return recipients
+	}
+
+	// Fetch the approval workflow
+	approvalFlow, err := p.approvalFlowRepo.Get(ctx, *letter.ApprovalFlowID)
+	if err != nil || approvalFlow == nil || len(approvalFlow.Steps) == 0 {
+		return recipients
+	}
+
+	// Add each approver as a recipient
+	for _, step := range approvalFlow.Steps {
+		if step.ApproverUserID == nil {
+			continue
+		}
+		
+		userID := *step.ApproverUserID
+		
+		// Skip if user is already added
+		if existingUsers[userID] {
+			continue
+		}
+		
+		existingUsers[userID] = true
+		
+		recipient := entities.LetterOutgoingRecipient{
+			LetterID:  letter.ID,
+			UserID:    &userID,
+			IsPrimary: false,
+			Status:    "pending",
+		}
+		
+		recipients = append(recipients, recipient)
+	}
+
+	return recipients
+}
+
+// collectDepartmentRecipients gathers all active users from a specific department
+func (p *LetterOutgoingRecipientProcessorImpl) collectDepartmentRecipients(
+	ctx context.Context,
+	letterID uuid.UUID,
+	departmentID uuid.UUID,
+	existingUsers map[uuid.UUID]bool,
+) []entities.LetterOutgoingRecipient {
+	var recipients []entities.LetterOutgoingRecipient
+	
+	// If no department specified, return empty
+	if departmentID == uuid.Nil {
+		return recipients
+	}
+
+	// Fetch all active users in the department
+	userDepartmentMappings, err := p.userDeptRepo.ListActiveByDepartmentIDs(ctx, []uuid.UUID{departmentID})
+	if err != nil {
+		return recipients
+	}
+
+	// Add each department user as a recipient
+	for _, mapping := range userDepartmentMappings {
+		// Skip if user is already added (e.g., from approval workflow)
+		if existingUsers[mapping.UserID] {
+			continue
+		}
+		
+		existingUsers[mapping.UserID] = true
+		
+		recipient := entities.LetterOutgoingRecipient{
+			LetterID:     letterID,
+			UserID:       &mapping.UserID,
+			DepartmentID: &mapping.DepartmentID,
+			IsPrimary:    false,
+			Status:       "pending",
+		}
+		
+		recipients = append(recipients, recipient)
+	}
+
+	return recipients
+}
+
+// UpdateRecipient updates an existing recipient's information
+func (p *LetterOutgoingRecipientProcessorImpl) UpdateRecipient(
+	ctx context.Context, 
+	recipient *entities.LetterOutgoingRecipient,
+) error {
+	return p.recipientRepo.Update(ctx, recipient)
+}
+
+// RemoveRecipient removes a recipient from a letter
+func (p *LetterOutgoingRecipientProcessorImpl) RemoveRecipient(
+	ctx context.Context, 
+	letterID uuid.UUID, 
+	recipientID uuid.UUID,
+) error {
+	return p.recipientRepo.Delete(ctx, recipientID)
+}
+
+// GetRecipientsByLetterID retrieves all recipients for a specific letter
+func (p *LetterOutgoingRecipientProcessorImpl) GetRecipientsByLetterID(
+	ctx context.Context, 
+	letterID uuid.UUID,
+) ([]entities.LetterOutgoingRecipient, error) {
+	recipientMap, err := p.recipientRepo.ListByLetterIDs(ctx, []uuid.UUID{letterID})
+	if err != nil {
+		return nil, err
+	}
+	
+	if recipients, ok := recipientMap[letterID]; ok {
+		return recipients, nil
+	}
+	
+	return []entities.LetterOutgoingRecipient{}, nil
+}
\ No newline at end of file
diff --git a/internal/processor/letter_validation_processor.go b/internal/processor/letter_validation_processor.go
new file mode 100644
index 0000000..b695947
--- /dev/null
+++ b/internal/processor/letter_validation_processor.go
@@ -0,0 +1,71 @@
+package processor
+
+import (
+	"context"
+	"errors"
+
+	"eslogad-be/internal/entities"
+
+	"github.com/google/uuid"
+)
+
+type LetterValidationProcessor interface {
+	ValidateCreateOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing) error
+	ValidateUpdateOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing, existingLetter *entities.LetterOutgoing) error
+	ValidateDeleteOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing) error
+	ValidateApprovalSubmission(ctx context.Context, letter *entities.LetterOutgoing) error
+}
+
+type LetterValidationProcessorImpl struct{}
+
+func NewLetterValidationProcessor() *LetterValidationProcessorImpl {
+	return &LetterValidationProcessorImpl{}
+}
+
+func (p *LetterValidationProcessorImpl) ValidateCreateOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing) error {
+	if letter.Subject == "" {
+		return errors.New("letter subject is required")
+	}
+
+	if letter.CreatedBy == uuid.Nil {
+		return errors.New("letter creator is required")
+	}
+
+	if letter.IssueDate.IsZero() {
+		return errors.New("letter issue date is required")
+	}
+
+	return nil
+}
+
+func (p *LetterValidationProcessorImpl) ValidateUpdateOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing, existingLetter *entities.LetterOutgoing) error {
+	if existingLetter.Status != entities.LetterOutgoingStatusDraft {
+		return errors.New("only draft letters can be updated")
+	}
+
+	if letter.Subject == "" {
+		return errors.New("letter subject cannot be empty")
+	}
+
+	return nil
+}
+
+func (p *LetterValidationProcessorImpl) ValidateDeleteOutgoingLetter(ctx context.Context, letter *entities.LetterOutgoing) error {
+	if letter.Status != entities.LetterOutgoingStatusDraft {
+		return errors.New("only draft letters can be deleted")
+	}
+
+	return nil
+}
+
+func (p *LetterValidationProcessorImpl) ValidateApprovalSubmission(ctx context.Context, letter *entities.LetterOutgoing) error {
+	if letter.Status != entities.LetterOutgoingStatusDraft {
+		return errors.New("only draft letters can be submitted for approval")
+	}
+
+	if letter.ApprovalFlowID == nil {
+		return errors.New("approval flow is required for submission")
+	}
+
+	return nil
+}
\ No newline at end of file
diff --git a/internal/repository/master_repository.go b/internal/repository/master_repository.go
index 64de9ba..6fad42c 100644
--- a/internal/repository/master_repository.go
+++ b/internal/repository/master_repository.go
@@ -356,6 +356,26 @@ func (r *DepartmentRepository) GetChildren(ctx context.Context, parentPath strin
 	return departments, nil
 }
 
+func (r *DepartmentRepository) GetAllDescendants(ctx context.Context, parentID uuid.UUID) ([]entities.Department, error) {
+	db := DBFromContext(ctx, r.db)
+	
+	// First get the parent department to get its path
+	var parent entities.Department
+	if err := db.WithContext(ctx).First(&parent, "id = ?", parentID).Error; err != nil {
+		return nil, err
+	}
+	
+	var departments []entities.Department
+	// Get all descendants using ltree
+	if err := db.WithContext(ctx).
+		Where("path <@ ? AND path != ?", parent.Path, parent.Path).
+		Order("path ASC").
+		Find(&departments).Error; err != nil {
+		return nil, err
+	}
+	return departments, nil
+}
+
 func (r *DepartmentRepository) UpdateChildrenPaths(ctx context.Context, oldPath, newPath string) error {
 	db := DBFromContext(ctx, r.db)
 	// Use raw SQL for ltree path update
diff --git a/internal/service/letter_outgoing_service.go b/internal/service/letter_outgoing_service.go
index 99f58d3..3b85fb4 100644
--- a/internal/service/letter_outgoing_service.go
+++ b/internal/service/letter_outgoing_service.go
@@ -53,31 +53,57 @@ type LetterOutgoingService interface {
 }
 
 type LetterOutgoingServiceImpl struct {
-	processor processor.LetterOutgoingProcessor
+	processor           processor.LetterOutgoingProcessor
+	txManager           *repository.TxManager
+	validationProcessor processor.LetterValidationProcessor
+	creationProcessor   processor.LetterCreationProcessor
+	approvalProcessor   processor.LetterApprovalProcessor
+	attachmentProcessor processor.LetterAttachmentProcessor
+	recipientProcessor  processor.LetterOutgoingRecipientProcessor
+	activityProcessor   processor.LetterActivityProcessor
 }
 
-func NewLetterOutgoingService(processor processor.LetterOutgoingProcessor) *LetterOutgoingServiceImpl {
+func NewLetterOutgoingService(
+	processor processor.LetterOutgoingProcessor,
+	txManager *repository.TxManager,
+	validationProcessor processor.LetterValidationProcessor,
+	creationProcessor processor.LetterCreationProcessor,
+	approvalProcessor processor.LetterApprovalProcessor,
+	attachmentProcessor processor.LetterAttachmentProcessor,
+	recipientProcessor processor.LetterOutgoingRecipientProcessor,
+	activityProcessor processor.LetterActivityProcessor,
+) *LetterOutgoingServiceImpl {
 	return &LetterOutgoingServiceImpl{
-		processor: processor,
+		processor:           processor,
+		txManager:           txManager,
+		validationProcessor: validationProcessor,
+		creationProcessor:   creationProcessor,
+		approvalProcessor:   approvalProcessor,
+		attachmentProcessor: attachmentProcessor,
+		recipientProcessor:  recipientProcessor,
+		activityProcessor:   activityProcessor,
 	}
 }
 
 func (s *LetterOutgoingServiceImpl) CreateOutgoingLetter(ctx context.Context, req *contract.CreateOutgoingLetterRequest) (*contract.OutgoingLetterResponse, error) {
 	departmentID := getDepartmentIDFromContext(ctx)
+	userID := getUserIDFromContext(ctx)
 
+	// Create letter entity
 	letter := &entities.LetterOutgoing{
 		Subject:               req.Subject,
 		Description:           req.Description,
 		PriorityID:            req.PriorityID,
 		ReceiverInstitutionID: req.ReceiverInstitutionID,
 		IssueDate:             req.IssueDate,
-		CreatedBy:             req.UserID,
+		CreatedBy:             userID,
 	}
 
 	if req.ReferenceNumber != nil {
 		letter.ReferenceNumber = req.ReferenceNumber
 	}
 
+	// Prepare attachments
 	var attachments []entities.LetterOutgoingAttachment
 	if len(req.Attachments) > 0 {
 		attachments = make([]entities.LetterOutgoingAttachment, len(req.Attachments))
@@ -86,16 +112,57 @@ func (s *LetterOutgoingServiceImpl) CreateOutgoingLetter(ctx context.Context, re
 				FileURL:    a.FileURL,
 				FileName:   a.FileName,
 				FileType:   a.FileType,
-				UploadedBy: &req.UserID,
+				UploadedBy: &userID,
 			}
 		}
 	}
 
-	err := s.processor.CreateOutgoingLetter(ctx, letter, attachments, req.UserID, departmentID)
+	// Execute creation with transaction in service layer
+	err := s.txManager.WithTransaction(ctx, func(txCtx context.Context) error {
+		// Step 1: Validate letter
+		if err := s.validationProcessor.ValidateCreateOutgoingLetter(txCtx, letter); err != nil {
+			return err
+		}
+
+		// Step 2: Prepare letter for creation (assign approval flow, set initial status)
+		if err := s.creationProcessor.PrepareLetterForCreation(txCtx, letter, departmentID); err != nil {
+			return err
+		}
+
+		// Step 3: Generate letter number
+		if err := s.creationProcessor.GenerateLetterNumber(txCtx, letter); err != nil {
+			return err
+		}
+
+		// Step 4: Create the letter
+		if err := s.creationProcessor.CreateLetter(txCtx, letter); err != nil {
+			return err
+		}
+
+		// Step 5: Create approval steps if needed
+		if err := s.approvalProcessor.CreateApprovalSteps(txCtx, letter); err != nil {
+			return err
+		}
+
+		// Step 6: Create initial recipients (approval workflow users + department members)
+		if err := s.recipientProcessor.CreateInitialRecipients(txCtx, letter, departmentID); err != nil {
+			return err
+		}
+
+		// Step 7: Create attachments
+		if err := s.attachmentProcessor.CreateAttachments(txCtx, letter.ID, attachments); err != nil {
+			return err
+		}
+
+		// Step 8: Log the activity
+		return s.activityProcessor.LogActivity(txCtx, letter.ID, entities.LetterOutgoingActionCreated, userID, nil)
+	})
+
 	if err != nil {
 		return nil, err
 	}
 
+	// Get the created letter with all relationships
 	result, err := s.processor.GetOutgoingLetterByID(ctx, letter.ID)
 	if err != nil {
 		return nil, err
diff --git a/migrations/000035_add_parent_department_id.down.sql b/migrations/000035_add_parent_department_id.down.sql
new file mode 100644
index 0000000..38ac6b4
--- /dev/null
+++ b/migrations/000035_add_parent_department_id.down.sql
@@ -0,0 +1,15 @@
+-- Drop the view
+DROP VIEW IF EXISTS department_hierarchy;
+
+-- Drop the functions
+DROP FUNCTION IF EXISTS get_department_hierarchy_path(UUID);
+DROP FUNCTION IF EXISTS check_department_hierarchy();
+
+-- Drop the trigger
+DROP TRIGGER IF EXISTS check_department_hierarchy_trigger ON departments;
+
+-- Drop the index
+DROP INDEX IF EXISTS idx_departments_parent_id;
+
+-- Remove the parent_department_id column
+ALTER TABLE departments DROP COLUMN IF EXISTS parent_department_id;
\ No newline at end of file
diff --git a/migrations/000035_add_parent_department_id.up.sql b/migrations/000035_add_parent_department_id.up.sql
new file mode 100644
index 0000000..cf67c90
--- /dev/null
+++ b/migrations/000035_add_parent_department_id.up.sql
@@ -0,0 +1,128 @@
+-- 1) Schema changes
+ALTER TABLE departments
+    ADD COLUMN parent_department_id UUID REFERENCES departments(id) ON DELETE CASCADE;
+
+CREATE INDEX idx_departments_parent_id ON departments(parent_department_id);
+
+-- (Optional but recommended for ltree lookups)
+-- CREATE EXTENSION IF NOT EXISTS ltree;
+-- CREATE INDEX idx_departments_path_gist ON departments USING GIST (path);
+-- CREATE INDEX idx_departments_path_nlevel ON departments ((nlevel(path)));
+
+-- 2) Migrate parent ids from existing ltree path
+-- Use ltree helpers: nlevel() and subpath()
+UPDATE departments d1
+SET parent_department_id = d2.id
+    FROM departments d2
+WHERE nlevel(d1.path) > 1
+  AND d2.path = subpath(d1.path, 0, nlevel(d1.path) - 1);
+
+-- 3) Guard against cycles/self-parent via trigger
+CREATE OR REPLACE FUNCTION check_department_hierarchy()
+RETURNS TRIGGER AS $$
+DECLARE
+current_id UUID;
+    max_depth INT := 100;
+    depth INT := 0;
+BEGIN
+    IF NEW.parent_department_id IS NULL THEN
+        RETURN NEW;
+END IF;
+
+    -- self-reference
+    IF NEW.parent_department_id = NEW.id THEN
+        RAISE EXCEPTION 'Department cannot be its own parent';
+END IF;
+
+    -- walk up the tree
+    current_id := NEW.parent_department_id;
+    WHILE current_id IS NOT NULL AND depth < max_depth LOOP
+        IF current_id = NEW.id THEN
+            RAISE EXCEPTION 'Circular reference detected in department hierarchy';
+END IF;
+
+SELECT parent_department_id INTO current_id
+FROM departments
+WHERE id = current_id;
+
+depth := depth + 1;
+END LOOP;
+
+    IF depth >= max_depth THEN
+        RAISE EXCEPTION 'Department hierarchy too deep (max: %)', max_depth;
+END IF;
+
+RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS check_department_hierarchy_trigger ON departments;
+
+CREATE TRIGGER check_department_hierarchy_trigger
+    BEFORE INSERT OR UPDATE OF parent_department_id ON departments
+    FOR EACH ROW
+    EXECUTE FUNCTION check_department_hierarchy();
+
+-- 4) Helper to rebuild dotted text path from codes (top.down.leaf)
+CREATE OR REPLACE FUNCTION get_department_hierarchy_path(dept_id UUID)
+RETURNS TEXT AS $$
+DECLARE
+path_text TEXT := '';
+    current_dept RECORD;
+    current_id UUID := dept_id;
+BEGIN
+    WHILE current_id IS NOT NULL LOOP
+SELECT id, name, parent_department_id, code
+INTO current_dept
+FROM departments
+WHERE id = current_id;
+
+IF current_dept IS NULL THEN
+            EXIT;
+END IF;
+
+        IF path_text = '' THEN
+            path_text := current_dept.code;
+ELSE
+            path_text := current_dept.code || '.' || path_text;
+END IF;
+
+        current_id := current_dept.parent_department_id;
+END LOOP;
+
+RETURN path_text;
+END;
+$$ LANGUAGE plpgsql;
+
+-- 5) View for easy hierarchy queries
+CREATE OR REPLACE VIEW department_hierarchy AS
+WITH RECURSIVE dept_tree AS (
+    -- roots
+    SELECT 
+        id,
+        name,
+        code,
+        parent_department_id,
+        path,
+        0  AS level,
+        ARRAY[id]   AS hierarchy_ids,
+        ARRAY[name] AS hierarchy_names
+    FROM departments
+    WHERE parent_department_id IS NULL
+
+    UNION ALL
+
+    -- children
+    SELECT 
+        d.id,
+        d.name,
+        d.code,
+        d.parent_department_id,
+        d.path,
+        dt.level + 1,
+        dt.hierarchy_ids   || d.id,
+        dt.hierarchy_names || d.name
+    FROM departments d
+    JOIN dept_tree dt ON d.parent_department_id = dt.id
+)
+SELECT * FROM dept_tree;