diff --git a/internal/services/planning_iterations.go b/internal/services/planning_iterations.go
index 260265843..6cb5b7290 100644
--- a/internal/services/planning_iterations.go
+++ b/internal/services/planning_iterations.go
@@ -140,6 +140,7 @@ func (s *PlanningService) FindIterationByName(workspaceID int, name string) (*It
 
 // ListIterations retrieves iterations with pagination and filtering.
 func (s *PlanningService) ListIterations(params IterationListParams) ([]IterationResult, int, error) {
+	params.Status = normalizePlanningStatus(params.Status)
 	list := newPlanningListQuery(iterationSelectQuery+"\nWHERE 1=1", "SELECT COUNT(*) FROM iterations i WHERE 1=1")
 	list.addWorkspaceScope("i.workspace_id", "i.is_global", params.WorkspaceID, params.WorkspaceIDs, params.IncludeGlobal)
 	list.addNullableIDFilter("i.type_id", params.TypeID)
@@ -245,6 +246,7 @@ func (s *PlanningService) CreateIteration(params CreateIterationParams) (*Iterat
 	if params.Status == "" {
 		params.Status = "planned"
 	}
+	params.Status = normalizePlanningStatus(params.Status)
 	if err := s.validateIterationMutation(params); err != nil {
 		return nil, err
 	}
@@ -287,6 +289,7 @@ type UpdateIterationParams struct {
 
 // UpdateIteration updates an existing iteration within its declared scope.
 func (s *PlanningService) UpdateIteration(params UpdateIterationParams) (*IterationResult, error) {
+	params.Status = normalizePlanningStatus(params.Status)
 	if err := s.validateIterationMutation(CreateIterationParams{
 		Name:        params.Name,
 		Description: params.Description,
diff --git a/internal/services/planning_milestones.go b/internal/services/planning_milestones.go
index bc724acf8..b5251a0db 100644
--- a/internal/services/planning_milestones.go
+++ b/internal/services/planning_milestones.go
@@ -269,6 +269,7 @@ type MilestoneListParams struct {
 
 // ListMilestones retrieves milestones with pagination and filtering.
 func (s *PlanningService) ListMilestones(params MilestoneListParams) ([]MilestoneResult, int, error) {
+	params.Status = normalizePlanningStatus(params.Status)
 	list := newPlanningListQuery(milestoneSelectQuery+"\nWHERE 1=1", "SELECT COUNT(*) FROM milestones m WHERE 1=1")
 	list.addWorkspaceScope("m.workspace_id", "m.is_global", params.WorkspaceID, params.WorkspaceIDs, params.IncludeGlobal)
 	list.addNullableIDFilter("m.category_id", params.CategoryID)
@@ -445,6 +446,7 @@ func (s *PlanningService) CreateMilestone(params CreateMilestoneParams) (*Milest
 	if params.Status == "" {
 		params.Status = "planning"
 	}
+	params.Status = normalizePlanningStatus(params.Status)
 	if err := s.validateMilestoneMutation(params); err != nil {
 		return nil, err
 	}
@@ -522,6 +524,7 @@ func (s *PlanningService) FindMilestoneByName(workspaceID int, name string) (*Mi
 // milestone to "in-progress" or "completed" without disturbing the other
 // fields. Returns a "not found" error when no row matches the scope.
 func (s *PlanningService) SetMilestoneStatus(milestoneID, workspaceID int, status string) error {
+	status = normalizePlanningStatus(status)
 	if !validMilestoneStatus(status) {
 		return planningValidationError("status", milestoneStatusValidationMessage)
 	}
@@ -589,6 +592,7 @@ type UpdateMilestoneParams struct {
 // UpdateMilestone updates an existing milestone within its declared scope.
 // is_global / workspace_id cannot be changed via this method.
 func (s *PlanningService) UpdateMilestone(params UpdateMilestoneParams) (*MilestoneResult, error) {
+	params.Status = normalizePlanningStatus(params.Status)
 	if err := s.validateMilestoneMutation(CreateMilestoneParams{
 		Name:        params.Name,
 		Description: params.Description,
diff --git a/internal/services/planning_validation.go b/internal/services/planning_validation.go
index 3fbccb450..336a237f1 100644
--- a/internal/services/planning_validation.go
+++ b/internal/services/planning_validation.go
@@ -43,6 +43,17 @@ func planningValidationErrorWithCause(field, message string, cause error) error
 
 const cancelledPlanningStatus = "cancelled" //nolint:misspell // Persisted API status.
 
+// normalizePlanningStatus maps the US spelling "canceled" onto the canonical
+// persisted planning status. Clients send either spelling; validation,
+// filters, and storage all use the canonical one. Any other value passes
+// through so validation can reject it.
+func normalizePlanningStatus(status string) string {
+	if strings.EqualFold(strings.TrimSpace(status), "canceled") {
+		return cancelledPlanningStatus
+	}
+	return status
+}
+
 func validMilestoneStatus(status string) bool {
 	switch status {
 	case "planning", "in-progress", "completed", cancelledPlanningStatus:
diff --git a/internal/wscli/milestone.go b/internal/wscli/milestone.go
index 3f5c5b847..bc7602263 100644
--- a/internal/wscli/milestone.go
+++ b/internal/wscli/milestone.go
@@ -6,6 +6,10 @@ import (
 	"github.com/spf13/cobra"
 )
 
+// milestoneCancelledStatus is the canonical persisted milestone status. The
+// API also accepts the US spelling "canceled" and normalizes it.
+const milestoneCancelledStatus = "cancelled" //nolint:misspell // Persisted API status.
+
 var milestoneCmd = &cobra.Command{
 	Use:   "milestone",
 	Short: "Manage milestones",
@@ -236,7 +240,7 @@ func init() {
 	milestoneCmd.AddCommand(milestoneUpdateCmd)
 
 	// List filters
-	milestoneListCmd.Flags().StringVarP(&milestoneStatusFilter, "status", "s", "", "filter by status (planning, in-progress, completed, canceled)")
+	milestoneListCmd.Flags().StringVarP(&milestoneStatusFilter, "status", "s", "", "filter by status (planning, in-progress, completed, "+milestoneCancelledStatus+")")
 	milestoneListCmd.Flags().BoolVar(&milestoneGlobalOnly, "global", false, "show only global milestones")
 
 	// Get flags
@@ -246,11 +250,11 @@ func init() {
 	milestoneCreateCmd.Flags().StringVarP(&milestoneCreateName, "name", "n", "", "milestone name (required)")
 	milestoneCreateCmd.Flags().StringVarP(&milestoneCreateDesc, "description", "d", "", "milestone description")
 	milestoneCreateCmd.Flags().StringVar(&milestoneCreateTarget, "target", "", "target date (YYYY-MM-DD)")
-	milestoneCreateCmd.Flags().StringVar(&milestoneCreateStatus, "status", "", "initial status (default: planning)")
+	milestoneCreateCmd.Flags().StringVar(&milestoneCreateStatus, "status", "", "initial status: planning (default), in-progress, completed, "+milestoneCancelledStatus)
 
 	// Update flags
 	milestoneUpdateCmd.Flags().StringVarP(&milestoneUpdateName, "name", "n", "", "new milestone name")
 	milestoneUpdateCmd.Flags().StringVarP(&milestoneUpdateDesc, "description", "d", "", "new description")
 	milestoneUpdateCmd.Flags().StringVar(&milestoneUpdateTarget, "target", "", "new target date (YYYY-MM-DD)")
-	milestoneUpdateCmd.Flags().StringVar(&milestoneUpdateStatus, "status", "", "new status")
+	milestoneUpdateCmd.Flags().StringVar(&milestoneUpdateStatus, "status", "", "new status: planning, in-progress, completed, "+milestoneCancelledStatus)
 }