feat(projects/orders): project status machine + bidirectional project-order sync; order reopen

- projects.service: VALID_TRANSITIONS (aktivni->dokonceny/zruseny,
  terminal->aktivni reopen), tolerant of legacy statuses; getProject returns
  valid_transitions; updateProject validates transitions (invalid_transition
  token -> Czech 400 in the route).
- NEW project->order cascade, transactional with the project update: finishing/
  cancelling a project completes/cancels its linked received order — only while
  the order is still open (never resurrects storno, never cancels completed);
  reopen never cascades. Direct tx write, no service recursion; cascaded order
  change gets its own audit row.
- orders.service: reopen edges (dokoncena/stornovana -> v_realizaci);
  syncProjectStatus is reopen-aware (reopen skips project sync) and returns
  the cascaded projects for per-project audit rows in the route.
- orders.schema: fix phantom 'zrusena' enum token -> canonical 'stornovana'
  (every storno PUT through the route 400ed with a raw English Zod message;
  latent until now because no UI sent it) + route-level regression test.
- NEW project-order-status-sync.test.ts: 15 tests — both cascade directions,
  guards, reopen-no-cascade, legacy tolerance, forward-sync regression.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/__tests__/orders-list.test.ts

@@ -196,6 +196,31 @@ describe("order attachment payload hygiene", () => {
     expect(withoutDetail!.attachment_name).toBeNull();
   });
 
+  it("PUT /:id accepts the canonical storno token through the Zod layer", async () => {
+    // Regression: UpdateOrderSchema carried a phantom "zrusena" enum member
+    // until 2026-07, so { status: "stornovana" } 400ed at parseBody with a
+    // raw English Zod message. Service-level tests bypass the schema — this
+    // must stay a route-level test.
+    const customer = await makeCustomer();
+    const res = await createOrder({
+      ...baseOrder,
+      customer_id: customer.id,
+      create_project: false,
+    });
+    if (!("id" in res)) failResult(res);
+    createdOrderIds.push(res.id!);
+
+    const put = await app.inject({
+      method: "PUT",
+      url: `/api/admin/orders/${res.id}`,
+      headers: { authorization: `Bearer ${adminToken}` },
+      payload: { status: "stornovana" },
+    });
+    expect(put.statusCode).toBe(200);
+    const row = await prisma.orders.findUnique({ where: { id: res.id! } });
+    expect(row!.status).toBe("stornovana");
+  });
+
   it("HTTP list/detail JSON carries no attachment_data; /attachment still serves the binary", async () => {
     const { withId, withoutId } = await makeOrderPair();
     const headers = { authorization: `Bearer ${adminToken}` };

src/__tests__/project-order-status-sync.test.ts

@@ -0,0 +1,301 @@
+import { describe, it, expect, afterEach, afterAll } from "vitest";
+import prisma from "../config/database";
+import {
+  updateProject,
+  getProject,
+  VALID_TRANSITIONS as PROJECT_VALID_TRANSITIONS,
+} from "../services/projects.service";
+import { updateOrder } from "../services/orders.service";
+
+/**
+ * Bidirectional project⇄order status sync (spec 2026-07-04):
+ *  - projects gain a status machine (aktivni ⇄ dokonceny/zruseny) with
+ *    legacy-status tolerance,
+ *  - finishing/cancelling a project cascades onto its linked OPEN order
+ *    (prijata/v_realizaci) — terminal orders are never touched,
+ *  - reopen (project → aktivni, order → v_realizaci) is now a legal
+ *    transition and NEVER cascades,
+ *  - regression: the existing order→project forward sync stays intact.
+ *
+ * Real app_test DB via the service layer (suite convention). Fixtures use a
+ * unique prefix; projects are created without project_number so getProject's
+ * NAS folder probe is skipped.
+ */
+
+const N = "posync_";
+
+const createdProjectIds: number[] = [];
+const createdOrderIds: number[] = [];
+let seq = 0;
+
+async function mkOrder(status: string) {
+  const order = await prisma.orders.create({
+    data: { order_number: `${N}${Date.now()}_${seq++}`, status },
+  });
+  createdOrderIds.push(order.id);
+  return order;
+}
+
+async function mkProject(status: string, orderId?: number) {
+  const project = await prisma.projects.create({
+    data: { name: `${N}project_${seq++}`, status, order_id: orderId ?? null },
+  });
+  createdProjectIds.push(project.id);
+  return project;
+}
+
+// FK-safe order: projects reference orders (Restrict), so projects go first.
+afterEach(async () => {
+  await prisma.projects.deleteMany({
+    where: { id: { in: createdProjectIds } },
+  });
+  await prisma.orders.deleteMany({ where: { id: { in: createdOrderIds } } });
+  createdProjectIds.length = 0;
+  createdOrderIds.length = 0;
+});
+
+afterAll(async () => {
+  await prisma.$disconnect();
+});
+
+function assertOk<T>(
+  res: T,
+): asserts res is Exclude<T, null | { error: unknown }> {
+  if (!res || (typeof res === "object" && "error" in res)) {
+    throw new Error(`expected success, got ${JSON.stringify(res)}`);
+  }
+}
+
+describe("project → order cascade (updateProject)", () => {
+  it("aktivni→dokonceny completes a linked v_realizaci order and returns synced_order", async () => {
+    const order = await mkOrder("v_realizaci");
+    const project = await mkProject("aktivni", order.id);
+
+    const res = await updateProject(project.id, { status: "dokonceny" });
+    assertOk(res);
+    expect(res.synced_order).toEqual({
+      id: order.id,
+      order_number: order.order_number,
+      from: "v_realizaci",
+      to: "dokoncena",
+    });
+    expect(res.old_status).toBe("aktivni");
+
+    const freshOrder = await prisma.orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(freshOrder?.status).toBe("dokoncena");
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("dokonceny");
+  });
+
+  it("aktivni→zruseny cancels a linked prijata order", async () => {
+    const order = await mkOrder("prijata");
+    const project = await mkProject("aktivni", order.id);
+
+    const res = await updateProject(project.id, { status: "zruseny" });
+    assertOk(res);
+    expect(res.synced_order).toEqual({
+      id: order.id,
+      order_number: order.order_number,
+      from: "prijata",
+      to: "stornovana",
+    });
+
+    const freshOrder = await prisma.orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(freshOrder?.status).toBe("stornovana");
+  });
+
+  it("guard: never resurrects a terminal order (stornovana stays stornovana)", async () => {
+    const order = await mkOrder("stornovana");
+    const project = await mkProject("aktivni", order.id);
+
+    const res = await updateProject(project.id, { status: "dokonceny" });
+    assertOk(res);
+    expect(res.synced_order).toBeNull();
+
+    const freshOrder = await prisma.orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(freshOrder?.status).toBe("stornovana");
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("dokonceny");
+  });
+
+  it("reopen (dokonceny→aktivni) never touches the linked order", async () => {
+    const order = await mkOrder("dokoncena");
+    const project = await mkProject("dokonceny", order.id);
+
+    const res = await updateProject(project.id, { status: "aktivni" });
+    assertOk(res);
+    expect(res.synced_order).toBeNull();
+
+    const freshOrder = await prisma.orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(freshOrder?.status).toBe("dokoncena");
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("aktivni");
+  });
+
+  it("no linked order → no cascade, synced_order null", async () => {
+    const project = await mkProject("aktivni");
+    const res = await updateProject(project.id, { status: "dokonceny" });
+    assertOk(res);
+    expect(res.synced_order).toBeNull();
+  });
+});
+
+describe("project status machine (updateProject validation)", () => {
+  it("rejects dokonceny→zruseny with the invalid_transition token", async () => {
+    const project = await mkProject("dokonceny");
+    const res = await updateProject(project.id, { status: "zruseny" });
+    expect(res && "error" in res && res.error).toBe("invalid_transition");
+    expect(res).toMatchObject({
+      currentStatus: "dokonceny",
+      newStatus: "zruseny",
+    });
+
+    // Nothing was written.
+    const fresh = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(fresh?.status).toBe("dokonceny");
+  });
+
+  it("legacy tolerance: an unknown current status may move to any canonical target", async () => {
+    const project = await mkProject("stary");
+    const res = await updateProject(project.id, { status: "dokonceny" });
+    assertOk(res);
+    const fresh = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(fresh?.status).toBe("dokonceny");
+  });
+
+  it("legacy tolerance still rejects a non-canonical target", async () => {
+    const project = await mkProject("stary");
+    const res = await updateProject(project.id, { status: "nesmysl" });
+    expect(res && "error" in res && res.error).toBe("invalid_transition");
+  });
+
+  it("status-unchanged payloads pass without transition validation", async () => {
+    const project = await mkProject("dokonceny");
+    const res = await updateProject(project.id, {
+      status: "dokonceny",
+      notes: `${N}note`,
+    });
+    assertOk(res);
+  });
+});
+
+describe("order reopen + order → project sync (updateOrder)", () => {
+  it("dokoncena→v_realizaci is now valid and skips project sync (reopen)", async () => {
+    const order = await mkOrder("dokoncena");
+    const project = await mkProject("dokonceny", order.id);
+
+    const res = await updateOrder(order.id, { status: "v_realizaci" });
+    expect("error" in res).toBe(false);
+    if ("error" in res) throw new Error(res.error);
+    expect(res.synced_projects).toEqual([]);
+
+    const freshOrder = await prisma.orders.findUnique({
+      where: { id: order.id },
+    });
+    expect(freshOrder?.status).toBe("v_realizaci");
+    // Reopen never cascades — the project keeps its terminal status.
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("dokonceny");
+  });
+
+  it("stornovana→v_realizaci is valid too; other exits from terminal stay rejected", async () => {
+    const order = await mkOrder("stornovana");
+    const res = await updateOrder(order.id, { status: "v_realizaci" });
+    expect("error" in res).toBe(false);
+
+    const back = await mkOrder("dokoncena");
+    const rejected = await updateOrder(back.id, { status: "prijata" });
+    expect("error" in rejected).toBe(true);
+    if ("error" in rejected) {
+      expect(rejected.status).toBe(400);
+      expect(rejected.error).toContain("Neplatný přechod stavu");
+    }
+  });
+
+  it("regression: v_realizaci→dokoncena still completes the linked project and reports it", async () => {
+    const order = await mkOrder("v_realizaci");
+    const project = await mkProject("aktivni", order.id);
+
+    const res = await updateOrder(order.id, { status: "dokoncena" });
+    expect("error" in res).toBe(false);
+    if ("error" in res) throw new Error(res.error);
+    expect(res.synced_projects).toEqual([
+      {
+        id: project.id,
+        project_number: null,
+        from: "aktivni",
+        to: "dokonceny",
+      },
+    ]);
+
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("dokonceny");
+  });
+
+  it("regression: prijata→stornovana still cancels the linked project", async () => {
+    const order = await mkOrder("prijata");
+    const project = await mkProject("aktivni", order.id);
+
+    const res = await updateOrder(order.id, { status: "stornovana" });
+    expect("error" in res).toBe(false);
+    if ("error" in res) throw new Error(res.error);
+    expect(res.synced_projects).toHaveLength(1);
+
+    const freshProject = await prisma.projects.findUnique({
+      where: { id: project.id },
+    });
+    expect(freshProject?.status).toBe("zruseny");
+  });
+});
+
+describe("getProject valid_transitions", () => {
+  it("matches the machine for canonical statuses", async () => {
+    const active = await mkProject("aktivni");
+    expect((await getProject(active.id))?.valid_transitions).toEqual(
+      PROJECT_VALID_TRANSITIONS["aktivni"],
+    );
+    expect((await getProject(active.id))?.valid_transitions).toEqual([
+      "dokonceny",
+      "zruseny",
+    ]);
+
+    const done = await mkProject("dokonceny");
+    expect((await getProject(done.id))?.valid_transitions).toEqual(["aktivni"]);
+
+    const cancelled = await mkProject("zruseny");
+    expect((await getProject(cancelled.id))?.valid_transitions).toEqual([
+      "aktivni",
+    ]);
+  });
+
+  it("offers all canonical targets for a legacy/unknown status", async () => {
+    const legacy = await mkProject("stary");
+    expect((await getProject(legacy.id))?.valid_transitions).toEqual([
+      "aktivni",
+      "dokonceny",
+      "zruseny",
+    ]);
+  });
+});

src/routes/admin/orders.ts

@@ -331,6 +331,26 @@ export default async function ordersRoutes(
         entityId: id,
         description: `Upravena objednávka ${result.data.order_number}`,
       });
+      // The order→project cascade updated linked project(s) — give each its
+      // own audit trail entry.
+      for (const p of result.synced_projects ?? []) {
+        const verb =
+          p.to === "dokonceny"
+            ? "dokončen"
+            : p.to === "zruseny"
+              ? "zrušen"
+              : "aktivován";
+        await logAudit({
+          request,
+          authData: request.authData,
+          action: "update",
+          entityType: "project",
+          entityId: p.id,
+          description: `Projekt ${p.project_number ?? `#${p.id}`} automaticky ${verb} (synchronizace s objednávkou)`,
+          oldValues: { status: p.from },
+          newValues: { status: p.to },
+        });
+      }
       return success(reply, { id }, 200, "Objednávka byla uložena");
     },
   );

src/routes/admin/projects.ts

@@ -131,6 +131,12 @@ export default async function projectsRoutes(
       const result = await updateProject(id, parsed.data);
       if (!result) return error(reply, "Projekt nenalezen", 404);
       if ("error" in result) {
+        if (result.error === "invalid_transition" && "currentStatus" in result)
+          return error(
+            reply,
+            `Neplatný přechod stavu z "${result.currentStatus}" na "${result.newStatus}"`,
+            400,
+          );
         return error(
           reply,
           result.error,
@@ -138,6 +144,7 @@ export default async function projectsRoutes(
         );
       }
 
+      const statusChanged = result.old_status !== result.status;
       await logAudit({
         request,
         authData: request.authData,
@@ -145,7 +152,26 @@ export default async function projectsRoutes(
         entityType: "project",
         entityId: id,
         description: `Upraven projekt ${result.name}`,
+        oldValues: statusChanged ? { status: result.old_status } : undefined,
+        newValues: statusChanged ? { status: result.status } : undefined,
       });
+      // The project→order cascade updated the linked order too — give the
+      // order its own audit trail entry.
+      if (result.synced_order) {
+        const so = result.synced_order;
+        await logAudit({
+          request,
+          authData: request.authData,
+          action: "update",
+          entityType: "order",
+          entityId: so.id,
+          description: `Objednávka ${so.order_number ?? `#${so.id}`} automaticky ${
+            so.to === "dokoncena" ? "dokončena" : "stornována"
+          } (synchronizace s projektem)`,
+          oldValues: { status: so.from },
+          newValues: { status: so.to },
+        });
+      }
       return success(reply, { id }, 200, "Projekt byl uložen");
     },
   );

src/schemas/orders.schema.ts

@@ -36,7 +36,7 @@ export const CreateOrderSchema = z.object({
   quotation_id: nullableIntIdFromForm.nullish(),
   customer_id: nullableIntIdFromForm.nullish(),
   status: z
-    .enum(["prijata", "v_realizaci", "dokoncena", "zrusena"])
+    .enum(["prijata", "v_realizaci", "dokoncena", "stornovana"])
     .optional()
     .default("prijata"),
   currency: z.string().max(10).optional().default("CZK"),
@@ -52,7 +52,9 @@ export const CreateOrderSchema = z.object({
 
 export const UpdateOrderSchema = z.object({
   customer_order_number: z.string().max(100).nullish(),
-  status: z.enum(["prijata", "v_realizaci", "dokoncena", "zrusena"]).optional(),
+  status: z
+    .enum(["prijata", "v_realizaci", "dokoncena", "stornovana"])
+    .optional(),
   currency: z.string().max(10).optional(),
   language: z.string().max(5).optional(),
   scope_title: z.string().max(255).nullish(),

src/services/orders.service.ts

@@ -31,12 +31,13 @@ interface OrderSectionInput {
   position?: number;
 }
 
-// Status transition rules matching PHP
+// Status transition rules matching PHP, plus the deliberate reopen edges
+// dokoncena/stornovana → v_realizaci (spec 2026-07-04 — status quick actions).
 export const VALID_TRANSITIONS: Record<string, string[]> = {
   prijata: ["v_realizaci", "stornovana"],
   v_realizaci: ["dokoncena", "stornovana"],
-  dokoncena: [],
+  dokoncena: ["v_realizaci"],
-  stornovana: [],
+  stornovana: ["v_realizaci"],
 };
 
 const ORDER_ALLOWED_SORT_FIELDS = [
@@ -54,23 +55,53 @@ const ORDER_TO_PROJECT_STATUS: Record<string, string> = {
   stornovana: "zruseny",
 };
 
+// Order statuses that count as terminal — a transition OUT of one is a REOPEN,
+// which deliberately never cascades to the linked project(s) (spec 2026-07-04).
+const TERMINAL_ORDER_STATUSES = ["dokoncena", "stornovana"];
+
+/** Project change performed by syncProjectStatus, returned for auditing. */
+export interface SyncedProject {
+  id: number;
+  project_number: string | null;
+  from: string | null;
+  to: string;
+}
+
 /**
  * Propagate an order status change onto its linked project(s). No-op when the
- * new status has no project-status mapping. Accepts a Prisma client (the tx
+ * new status has no project-status mapping, or when the change is a reopen
- * client inside a transaction, or the base client otherwise) so both update
+ * (previous status terminal — reopening never cascades, spec 2026-07-04).
- * branches share one implementation.
+ * Accepts a Prisma client (the tx client inside a transaction, or the base
+ * client otherwise) so both update branches share one implementation.
+ * Returns the projects it actually changed so the route can audit them.
  */
 async function syncProjectStatus(
   client: Prisma.TransactionClient,
   orderId: number,
+  previousStatus: string,
   newStatus: string,
-): Promise<void> {
+): Promise<SyncedProject[]> {
+  if (TERMINAL_ORDER_STATUSES.includes(previousStatus)) return [];
   const projectStatus = ORDER_TO_PROJECT_STATUS[newStatus];
-  if (!projectStatus) return;
+  if (!projectStatus) return [];
-  await client.projects.updateMany({
+  const linked = await client.projects.findMany({
     where: { order_id: orderId },
+    select: { id: true, project_number: true, status: true },
+  });
+  // Filter in JS (not via `status: { not: … }`) so NULL-status projects are
+  // still picked up — SQL `<>` would exclude them.
+  const changed = linked.filter((p) => p.status !== projectStatus);
+  if (changed.length === 0) return [];
+  await client.projects.updateMany({
+    where: { id: { in: changed.map((p) => p.id) } },
     data: { status: projectStatus },
   });
+  return changed.map((p) => ({
+    id: p.id,
+    project_number: p.project_number,
+    from: p.status,
+    to: projectStatus,
+  }));
 }
 
 // ⚠ Also called by getOrderTotals with a MINIMAL select (currency, item
@@ -640,6 +671,10 @@ export async function updateOrder(id: number, body: UpdateOrderData) {
     }
   }
 
+  // Projects cascaded onto by a status change — surfaced to the route for
+  // per-project audit rows.
+  let syncedProjects: SyncedProject[] = [];
+
   const data: Record<string, unknown> = { modified_at: new Date() };
   const strFields = [
     "customer_order_number",
@@ -678,7 +713,12 @@ export async function updateOrder(id: number, body: UpdateOrderData) {
 
       // Sync project status when order status changes (matching PHP)
       if (body.status !== undefined && String(body.status) !== currentStatus) {
-        await syncProjectStatus(tx, id, String(body.status));
+        syncedProjects = await syncProjectStatus(
+          tx,
+          id,
+          currentStatus,
+          String(body.status),
+        );
       }
 
       if (Array.isArray(body.items)) {
@@ -714,11 +754,19 @@ export async function updateOrder(id: number, body: UpdateOrderData) {
 
     // Sync project status when order status changes (matching PHP)
     if (body.status !== undefined && String(body.status) !== currentStatus) {
-      await syncProjectStatus(prisma, id, String(body.status));
+      syncedProjects = await syncProjectStatus(
+        prisma,
+        id,
+        currentStatus,
+        String(body.status),
+      );
     }
   }
 
-  return { data: { id, order_number: existing.order_number } };
+  return {
+    data: { id, order_number: existing.order_number },
+    synced_projects: syncedProjects,
+  };
 }
 
 export async function deleteOrder(id: number, deleteFiles = false) {

src/services/projects.service.ts

@@ -6,6 +6,7 @@ import {
 } from "./numbering.service";
 import { NasFileManager } from "./nas-file-manager";
 import type { CreateProjectInput } from "../schemas/projects.schema";
+import type { projects } from "../types";
 
 const nasFileManager = new NasFileManager();
 
@@ -17,6 +18,29 @@ const ALLOWED_SORT_FIELDS = [
   "created_at",
 ];
 
+// Status transition rules (spec 2026-07-04 — projects gain a status machine;
+// dokonceny/zruseny → aktivni is a deliberate reopen edge).
+export const VALID_TRANSITIONS: Record<string, string[]> = {
+  aktivni: ["dokonceny", "zruseny"],
+  dokonceny: ["aktivni"],
+  zruseny: ["aktivni"],
+};
+
+const CANONICAL_STATUSES = Object.keys(VALID_TRANSITIONS);
+
+/**
+ * Legal next statuses for a project. The status column is a legacy free-text
+ * string, so an unknown/legacy current status may move to any canonical value
+ * (minus itself) — tolerant, matching the updateProject validation.
+ */
+function validTransitionsFor(status: string | null): string[] {
+  const current = status ?? "";
+  if (Object.prototype.hasOwnProperty.call(VALID_TRANSITIONS, current)) {
+    return VALID_TRANSITIONS[current];
+  }
+  return CANONICAL_STATUSES.filter((s) => s !== current);
+}
+
 interface ListProjectsParams {
   page: number;
   limit: number;
@@ -91,13 +115,39 @@ export async function getProject(id: number) {
     order_number: orders?.order_number ?? null,
     order_status: orders?.status ?? null,
     quotation_number: quotations?.quotation_number ?? null,
+    // Computed server-side so the frontend renders only legal status buttons
+    // (same contract as offers/orders/issued orders).
+    valid_transitions: validTransitionsFor(project.status),
     has_nas_folder: project.project_number
       ? nasFileManager.projectFolderExists(project.project_number)
       : false,
   };
 }
 
-export async function updateProject(id: number, body: Record<string, unknown>) {
+/** Order change performed by the project→order cascade, returned for auditing. */
+export interface SyncedOrder {
+  id: number;
+  order_number: string | null;
+  from: string;
+  to: string;
+}
+
+// Explicit union — inference would normalize the members with `?: undefined`
+// props (and narrow synced_order to `null`, its value at the return
+// statement), breaking the route's `"error" in result` narrowing.
+type UpdateProjectResult =
+  | null
+  | { error: string; status: number }
+  | { error: "invalid_transition"; currentStatus: string; newStatus: string }
+  | (projects & {
+      old_status: string | null;
+      synced_order: SyncedOrder | null;
+    });
+
+export async function updateProject(
+  id: number,
+  body: Record<string, unknown>,
+): Promise<UpdateProjectResult> {
   const existing = await prisma.projects.findUnique({ where: { id } });
   if (!existing) return null;
 
@@ -108,6 +158,25 @@ export async function updateProject(id: number, body: Record<string, unknown>) {
     return { error: "Číslo projektu nelze změnit", status: 400 };
   }
 
+  // Status changes must follow the transition table (offers/orders parity).
+  // Legacy tolerance: the column is historic free text, so an unknown current
+  // status may move to any canonical value.
+  const currentStatus = existing.status ?? "";
+  const statusChanges =
+    body.status !== undefined && String(body.status) !== currentStatus;
+  const newStatus = statusChanges ? String(body.status) : null;
+  if (statusChanges && newStatus !== null) {
+    const allowed = Object.prototype.hasOwnProperty.call(
+      VALID_TRANSITIONS,
+      currentStatus,
+    )
+      ? VALID_TRANSITIONS[currentStatus]
+      : CANONICAL_STATUSES;
+    if (!allowed.includes(newStatus)) {
+      return { error: "invalid_transition" as const, currentStatus, newStatus };
+    }
+  }
+
   // FK pre-validation (mirrors createProject): a dangling id would raise
   // P2003 at Prisma and surface as a generic 500 — return the same Czech
   // 400s as the create path. null still clears the FK.
@@ -164,7 +233,45 @@ export async function updateProject(id: number, body: Record<string, unknown>) {
   if (body.end_date !== undefined)
     data.end_date = body.end_date ? new Date(String(body.end_date)) : null;
 
-  const updated = await prisma.projects.update({ where: { id }, data });
+  // Project → order cascade (spec 2026-07-04): finishing/cancelling a project
+  // completes/cancels its linked order iff the order is still open
+  // (prijata/v_realizaci). Reopen (→aktivni) never touches the order, and
+  // completed/cancelled orders are never resurrected. Direct tx write — no
+  // updateOrder recursion — in the SAME transaction as the project update.
+  let syncedOrder: SyncedOrder | null = null;
+
+  const wantsCascade =
+    statusChanges &&
+    (newStatus === "dokonceny" || newStatus === "zruseny") &&
+    existing.order_id != null;
+
+  const updated = wantsCascade
+    ? await prisma.$transaction(async (tx) => {
+        const row = await tx.projects.update({ where: { id }, data });
+        const order = await tx.orders.findUnique({
+          where: { id: existing.order_id! },
+          select: { id: true, order_number: true, status: true },
+        });
+        const orderStatus = order?.status ?? "";
+        if (
+          order &&
+          (orderStatus === "prijata" || orderStatus === "v_realizaci")
+        ) {
+          const to = newStatus === "dokonceny" ? "dokoncena" : "stornovana";
+          await tx.orders.update({
+            where: { id: order.id },
+            data: { status: to, modified_at: new Date() },
+          });
+          syncedOrder = {
+            id: order.id,
+            order_number: order.order_number,
+            from: orderStatus,
+            to,
+          };
+        }
+        return row;
+      })
+    : await prisma.projects.update({ where: { id }, data });
 
   if (
     body.name !== undefined &&
@@ -184,7 +291,9 @@ export async function updateProject(id: number, body: Record<string, unknown>) {
     }
   }
 
-  return updated;
+  // old_status + synced_order let the route audit the status change and the
+  // cascaded order update.
+  return { ...updated, old_status: existing.status, synced_order: syncedOrder };
 }
 
 /**