diff --git a/lib/task-status.ts b/lib/task-status.ts
new file mode 100644
index 0000000..523b61b
--- /dev/null
+++ b/lib/task-status.ts
@@ -0,0 +1,52 @@
+// Bidirectionele case-mappers voor de REST API-boundary.
+// DB houdt UPPER_SNAKE; API exposeert lowercase.
+
+import type { TaskStatus, StoryStatus } from '@prisma/client'
+
+const TASK_DB_TO_API = {
+  TO_DO: 'todo',
+  IN_PROGRESS: 'in_progress',
+  REVIEW: 'review',
+  DONE: 'done',
+} as const satisfies Record<TaskStatus, string>
+
+const TASK_API_TO_DB: Record<string, TaskStatus> = {
+  todo: 'TO_DO',
+  in_progress: 'IN_PROGRESS',
+  review: 'REVIEW',
+  done: 'DONE',
+}
+
+const STORY_DB_TO_API = {
+  OPEN: 'open',
+  IN_SPRINT: 'in_sprint',
+  DONE: 'done',
+} as const satisfies Record<StoryStatus, string>
+
+const STORY_API_TO_DB: Record<string, StoryStatus> = {
+  open: 'OPEN',
+  in_sprint: 'IN_SPRINT',
+  done: 'DONE',
+}
+
+export type TaskStatusApi = typeof TASK_DB_TO_API[TaskStatus]
+export type StoryStatusApi = typeof STORY_DB_TO_API[StoryStatus]
+
+export function taskStatusToApi(s: TaskStatus): TaskStatusApi {
+  return TASK_DB_TO_API[s]
+}
+
+export function taskStatusFromApi(s: string): TaskStatus | null {
+  return TASK_API_TO_DB[s.toLowerCase()] ?? null
+}
+
+export function storyStatusToApi(s: StoryStatus): StoryStatusApi {
+  return STORY_DB_TO_API[s]
+}
+
+export function storyStatusFromApi(s: string): StoryStatus | null {
+  return STORY_API_TO_DB[s.toLowerCase()] ?? null
+}
+
+export const TASK_STATUS_API_VALUES = Object.values(TASK_DB_TO_API)
+export const STORY_STATUS_API_VALUES = Object.values(STORY_DB_TO_API)