diff --git a/license-backend/README.md b/license-backend/README.md
index 21c9948..9f06332 100644
--- a/license-backend/README.md
+++ b/license-backend/README.md
@@ -74,6 +74,7 @@ Optional: `email`, `note`, `expires_at` (ISO date; omit for lifetime).
 |---|---|---|
 | POST | `/api/v1/licenses` | generate a key |
 | GET  | `/api/v1/licenses/:key` | inspect (status + bound domains) |
+| PATCH | `/api/v1/licenses/:key` | modify (seat limit, email, note, expiry, status) |
 | POST | `/api/v1/licenses/:key/disable` | revoke |
 | POST | `/api/v1/licenses/:key/enable` | un-revoke |
 | GET  | `/api/v1/products` | list products |
diff --git a/license-backend/src/server.js b/license-backend/src/server.js
index 53929c7..c77b19c 100644
--- a/license-backend/src/server.js
+++ b/license-backend/src/server.js
@@ -594,6 +594,49 @@ app.get('/api/v1/licenses/:key', adminOnly, (req, res) => {
   });
 });
 
+// Modify a license (e.g. change the seat limit). Partial update; only the
+// provided fields are changed. Body (JSON), any of:
+//   max_activations (>=1 or -1), email, note, expires_at (ISO|null), status (active|disabled)
+app.patch('/api/v1/licenses/:key', adminOnly, (req, res) => {
+  const license = Q.licenseByKey.get(req.params.key);
+  if (!license) return fail(res, 404, 'not found');
+
+  const fields = {};
+
+  if ('max_activations' in req.body) {
+    const max = Number(req.body.max_activations);
+    if (!Number.isInteger(max) || (max < 1 && max !== -1)) {
+      return fail(res, 400, 'max_activations must be a positive integer or -1 (unlimited)');
+    }
+    fields.max_activations = max;
+  }
+  if ('email' in req.body) fields.email = req.body.email ? String(req.body.email).trim() : null;
+  if ('note' in req.body) fields.note = req.body.note ? String(req.body.note).trim() : null;
+  if ('expires_at' in req.body) fields.expires_at = req.body.expires_at ? String(req.body.expires_at).trim() : null;
+  if ('status' in req.body) {
+    const st = String(req.body.status);
+    if (!['active', 'disabled'].includes(st)) return fail(res, 400, 'status must be active or disabled');
+    fields.status = st;
+  }
+
+  const cols = Object.keys(fields); // fixed allow-list above → safe to interpolate
+  if (!cols.length) return fail(res, 400, 'no updatable fields provided');
+
+  const setClause = cols.map((c) => `${c} = @${c}`).join(', ');
+  db.prepare(`UPDATE licenses SET ${setClause} WHERE id = @id`).run({ ...fields, id: license.id });
+
+  const u = Q.licenseByKey.get(req.params.key);
+  return res.json({
+    ok: true,
+    key: u.key,
+    max_activations: u.max_activations,
+    status: u.status,
+    email: u.email,
+    note: u.note,
+    expires_at: u.expires_at,
+  });
+});
+
 // Disable a license (revokes it everywhere on next check).
 app.post('/api/v1/licenses/:key/disable', adminOnly, (req, res) => {
   const license = Q.licenseByKey.get(req.params.key);
diff --git a/license-backend/test/integration.mjs b/license-backend/test/integration.mjs
index 9b835d1..47275d0 100644
--- a/license-backend/test/integration.mjs
+++ b/license-backend/test/integration.mjs
@@ -215,6 +215,19 @@ try {
   const fuLocal = await admin('POST', '/api/v1/releases/from-url', { product: P, version: '1.2.0', zip_url: 'http://127.0.0.1/a.zip' });
   ok('from-url private host → 400', fuLocal.status === 400, JSON.stringify(fuLocal.json));
 
+  // ── Modify a license (PATCH) ──
+  // key1 is max=1 (1 domain bound). Switch it to unlimited and prove it works.
+  const patch = await admin('PATCH', `/api/v1/licenses/${key1}`, { max_activations: -1 });
+  ok('patch to unlimited', patch.status === 200 && patch.json.max_activations === -1, JSON.stringify(patch.json));
+  const extra = await pub('/api/v1/activate', { key: key1, product: P, domain: 'extra.de' });
+  ok('after unlimited, extra domain activates', extra.json.status === 'valid', JSON.stringify(extra.json));
+
+  const patchBad = await admin('PATCH', `/api/v1/licenses/${key1}`, { max_activations: 0 });
+  ok('patch bad value → 400', patchBad.status === 400, JSON.stringify(patchBad.json));
+
+  const patchUnknown = await admin('PATCH', '/api/v1/licenses/ZZZZ-ZZZZ-ZZZZ-ZZZZ', { max_activations: 3 });
+  ok('patch unknown key → 404', patchUnknown.status === 404, JSON.stringify(patchUnknown.json));
+
 } catch (e) {
   console.error(e);
   fail++;