diff --git a/backend/src/__tests__/tasks-by-key.test.ts b/backend/src/__tests__/tasks-by-key.test.ts
new file mode 100644
index 0000000..f9e7238
--- /dev/null
+++ b/backend/src/__tests__/tasks-by-key.test.ts
@@ -0,0 +1,74 @@
+/**
+ * GET /api/tasks/by-key/:key — issue-key lookup.
+ *
+ *  1. Existing key returns the same payload as GET /api/tasks/:id
+ *  2. Unknown key → 404
+ *  3. Invalid key format → 400
+ *  4. Cross-workspace lookup → 404 (no information leak)
+ */
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { auth, registerUser, createWorkspace, createBoard, cleanupTestData, api } from './helpers.js';
+
+describe('GET /api/tasks/by-key/:key', () => {
+  let ownerToken: string;
+  let strangerToken: string;
+  let issueKey: string;
+  let taskId: string;
+
+  beforeAll(async () => {
+    const owner = await registerUser();
+    ownerToken = owner.token;
+    const ws = await createWorkspace(ownerToken);
+    const board = await createBoard(ownerToken, ws.id);
+
+    const created = await api
+      .post(`/api/boards/${board.id}/tasks`)
+      .set(auth(ownerToken))
+      .send({ title: 'Look me up' });
+    expect(created.status).toBe(201);
+    taskId = created.body.id;
+    issueKey = created.body.issueKey;
+
+    const stranger = await registerUser();
+    strangerToken = stranger.token;
+  });
+
+  afterAll(cleanupTestData);
+
+  it('returns the task by issueKey with same shape as /api/tasks/:id', async () => {
+    const byKey = await api.get(`/api/tasks/by-key/${issueKey}`).set(auth(ownerToken));
+    const byId = await api.get(`/api/tasks/${taskId}`).set(auth(ownerToken));
+    expect(byKey.status).toBe(200);
+    expect(byId.status).toBe(200);
+    expect(byKey.body.id).toBe(taskId);
+    expect(byKey.body.issueKey).toBe(issueKey);
+    expect(byKey.body.title).toBe('Look me up');
+    expect(byKey.body.title).toBe(byId.body.title);
+  });
+
+  it('returns 404 for an unknown issueKey', async () => {
+    const res = await api.get('/api/tasks/by-key/DEV-99999').set(auth(ownerToken));
+    expect(res.status).toBe(404);
+  });
+
+  it('rejects malformed issueKey with 400', async () => {
+    const lowercase = await api.get('/api/tasks/by-key/dev-1').set(auth(ownerToken));
+    expect(lowercase.status).toBe(400);
+
+    const noDash = await api.get('/api/tasks/by-key/DEV1').set(auth(ownerToken));
+    expect(noDash.status).toBe(400);
+
+    const tooShort = await api.get('/api/tasks/by-key/D-1').set(auth(ownerToken));
+    expect(tooShort.status).toBe(400);
+  });
+
+  it('returns 404 (not 403) for cross-workspace lookup to avoid information leak', async () => {
+    const res = await api.get(`/api/tasks/by-key/${issueKey}`).set(auth(strangerToken));
+    expect(res.status).toBe(404);
+  });
+
+  it('requires authentication', async () => {
+    const res = await api.get(`/api/tasks/by-key/${issueKey}`);
+    expect(res.status).toBe(401);
+  });
+});
diff --git a/backend/src/modules/tasks/tasks.dto.ts b/backend/src/modules/tasks/tasks.dto.ts
index 0c0812a..45f778b 100644
--- a/backend/src/modules/tasks/tasks.dto.ts
+++ b/backend/src/modules/tasks/tasks.dto.ts
@@ -73,8 +73,17 @@ export const myTasksFiltersDto = z.object({
   offset: z.coerce.number().int().min(0).default(0).optional(),
 });
 
+export const issueKeyParamDto = z.object({
+  // Board prefix is alphanumeric (letters + digits), 2-10 chars, must start
+  // with a letter to avoid clashes with UUID-like ids. Number is unsigned int.
+  key: z
+    .string()
+    .regex(/^[A-Z][A-Z0-9]{1,9}-\d+$/, 'Issue key должен быть формата PREFIX-NUMBER (например, DEV-42)'),
+});
+
 export type CreateTaskDto = z.infer<typeof createTaskDto>;
 export type UpdateTaskDto = z.infer<typeof updateTaskDto>;
 export type BulkUpdateDto = z.infer<typeof bulkUpdateDto>;
 export type TaskFiltersDto = z.infer<typeof taskFiltersDto>;
 export type MyTasksFiltersDto = z.infer<typeof myTasksFiltersDto>;
+export type IssueKeyParamDto = z.infer<typeof issueKeyParamDto>;
diff --git a/backend/src/modules/tasks/tasks.router.ts b/backend/src/modules/tasks/tasks.router.ts
index a53bd17..332eb28 100644
--- a/backend/src/modules/tasks/tasks.router.ts
+++ b/backend/src/modules/tasks/tasks.router.ts
@@ -12,6 +12,7 @@ import {
   myTasksFiltersDto,
   bulkUpdateDto,
   bulkDeleteDto,
+  issueKeyParamDto,
   type BulkUpdateDto,
 } from './tasks.dto.js';
 import * as tasks from './tasks.service.js';
@@ -56,6 +57,18 @@ boardTasksRouter.post('/bulk-delete', bulkLimit, validate(bulkDeleteDto), authHa
 // ─── /tasks/:id ───────────────────────────────────────────────────────────────
 const router = Router();
 router.use(authenticate);
+
+// Registered BEFORE /:id route + taskMfaGuard so "by-key" doesn't get
+// caught as id="by-key". The handler resolves issueKey → id and then
+// delegates to getTask which enforces workspace access.
+router.get(
+  '/by-key/:key',
+  validate(issueKeyParamDto, 'params'),
+  authHandler(async (req, res) => {
+    res.json(await tasks.getTaskByIssueKey(String(req.params.key), req.user!.userId));
+  }),
+);
+
 router.use('/:id', asyncHandler(taskMfaGuard()));
 
 router.get('/:id', authHandler(async (req, res) => {
diff --git a/backend/src/modules/tasks/tasks.service.ts b/backend/src/modules/tasks/tasks.service.ts
index 5704eaf..05e590d 100644
--- a/backend/src/modules/tasks/tasks.service.ts
+++ b/backend/src/modules/tasks/tasks.service.ts
@@ -244,6 +244,23 @@ export async function createTask(boardId: string, userId: string, dto: CreateTas
   return task;
 }
 
+// ─── Get task by issue key ────────────────────────────────────────────────────
+
+/**
+ * Look up a task by its human-readable issue key (e.g. "DEV-42") and return
+ * the same shape as {@link getTask}. Authorization is delegated to getTask:
+ * if the caller doesn't have access to the underlying board's workspace,
+ * they get a 404 (consistent with not revealing existence cross-workspace).
+ */
+export async function getTaskByIssueKey(issueKey: string, userId: string) {
+  const found = await prisma.task.findUnique({
+    where: { issueKey },
+    select: { id: true },
+  });
+  if (!found) throw new AppError(404, 'Task not found or access denied');
+  return getTask(found.id, userId);
+}
+
 // ─── Get task detail ──────────────────────────────────────────────────────────
 
 export async function getTask(taskId: string, userId: string) {