diff --git a/server/services/projectKindAssign.js b/server/services/projectKindAssign.js
index fe85f32..ec3fc25 100644
--- a/server/services/projectKindAssign.js
+++ b/server/services/projectKindAssign.js
@@ -50,6 +50,7 @@ export async function completeAssignment(
     const customer = !!forCustomer
     let createdTicketId = null
     let finalTicketId = null
+    const warnings = []
 
     if (customer) {
       if (!(await loadOrNull(config.collections.customers, customerId))) throw fail(400, 'Kunde nicht gefunden.')
@@ -80,7 +81,9 @@ export async function completeAssignment(
       }
 
       try {
-        await assign(projectId, { customerId, ticketId: finalTicketId }, { now })
+        const assigned = await assign(projectId, { customerId, ticketId: finalTicketId }, { now })
+        // assignProject schluckt Umzug-/Nachtrage-Fehler und meldet sie als Warnungen.
+        if (assigned?.warnings?.length) warnings.push(...assigned.warnings)
       } catch (err) {
         if (createdTicketId) await deleteTicket(createdTicketId).catch(() => {})
         throw err
@@ -100,9 +103,10 @@ export async function completeAssignment(
         await updateProject(projectId, { subdomain: preview.subdomain, projectType: 'preview' })
       } catch (err) {
         // Art und Zuordnung sind gespeichert - die Preview laesst sich nachtraeglich einschalten.
-        result.warnings = [`Die Preview konnte nicht eingeschaltet werden (${err.message}).`]
+        warnings.push(`Die Preview konnte nicht eingeschaltet werden (${err.message}).`)
       }
     }
+    if (warnings.length) result.warnings = warnings
     return result
   })
 }
diff --git a/test/projectKindAssign.test.js b/test/projectKindAssign.test.js
index 92db8d4..bcecf93 100644
--- a/test/projectKindAssign.test.js
+++ b/test/projectKindAssign.test.js
@@ -44,6 +44,10 @@ before(async () => {
         newProj('p9', 'doppelt'),
         newProj('p10', 'prev'),
         newProj('p11', 'route'),
+        newProj('p13', 'warn'),
+        newProj('p14', 'race'),
+        newProj('p15', 'kunde'),
+        newProj('p16', 'eins'),
         newProj('p12', 'schon', { kind: 'app', kindSetBy: 'Max', kindSetAt: '2026-09-29T08:00:00.000Z' }),
       ],
       workorders: [
@@ -176,6 +180,47 @@ test('Website mit Subdomain ⇒ updateWebsiteProject(preview)', async () => {
   assert.deepEqual(s.calls.update, [['p10', { subdomain: 'prev', projectType: 'preview' }]])
 })
 
+test('Warnungen von assignProject und Preview-Fehler werden zusammengefuehrt', async () => {
+  const s = stubs()
+  s.deps.assignProject = async () => ({ ok: true, warnings: ['Umzug fehlgeschlagen'] })
+  s.deps.updateWebsiteProject = async () => { throw new Error('Gitea aus') }
+  const r = await completeAssignment('p13', { kind: 'website', forCustomer: true, customerId: 'c1', ticketId: 't1', preview: { subdomain: 'w' } }, opts(s.deps))
+  assert.equal(r.ticketId, 't1')
+  assert.equal(r.warnings.length, 2)
+  assert.equal(r.warnings[0], 'Umzug fehlgeschlagen')
+  assert.match(r.warnings[1], /Preview/)
+  assert.equal(aw.get('websiteProjects', 'p13').kind, 'website')
+})
+
+test('gleichzeitiger Doppelaufruf ⇒ genau ein Ticket und ein 409', async () => {
+  const s = stubs()
+  const before = aw.all('workorders').length
+  const body = { kind: 'app', forCustomer: true, customerId: 'c1', newTicket: { topic: 'race' } }
+  const res = await Promise.allSettled([completeAssignment('p14', body, opts(s.deps)), completeAssignment('p14', body, opts(s.deps))])
+  assert.equal(res.filter((x) => x.status === 'fulfilled').length, 1)
+  const rej = res.find((x) => x.status === 'rejected')
+  assert.equal(rej.reason.status, 409)
+  assert.equal(aw.all('workorders').length, before + 1)
+})
+
+test('forCustomer mit unbekanntem Kunden ⇒ 400', async () => {
+  const s = stubs()
+  await assert.rejects(
+    () => completeAssignment('p15', { kind: 'website', forCustomer: true, customerId: 'nix', newTicket: { topic: 'x' } }, opts(s.deps)),
+    (e) => e.status === 400
+  )
+  assert.equal(aw.get('websiteProjects', 'p15').kind, undefined)
+})
+
+test('ticketId und newTicket beide oder keins ⇒ 400', async () => {
+  const s = stubs()
+  const base = { kind: 'website', forCustomer: true, customerId: 'c1' }
+  for (const extra of [{ ticketId: 't1', newTicket: { topic: 'x' } }, {}]) {
+    await assert.rejects(() => completeAssignment('p16', { ...base, ...extra }, opts(s.deps)), (e) => e.status === 400)
+  }
+  assert.equal(aw.get('websiteProjects', 'p16').kind, undefined)
+})
+
 test('Route: ohne Staff-JWT ⇒ 401, mit JWT intern 200, bereits zugeordnet 409, unbekannt 404', async () => {
   const post = (id, body, jwt) =>
     fetch(`${baseUrl}/api/admin/website-projects/${id}/zuordnen`, {