diff --git a/fusion_centralize_billing/models/service.py b/fusion_centralize_billing/models/service.py
index 5dc83a1e..40046759 100644
--- a/fusion_centralize_billing/models/service.py
+++ b/fusion_centralize_billing/models/service.py
@@ -62,3 +62,34 @@ class FusionBillingService(models.Model):
             return self.browse()
         key_hash = hashlib.sha256(raw_key.encode()).hexdigest()
         return self.search([('api_key_hash', '=', key_hash), ('active', '=', True)], limit=1)
+
+    def _api_upsert_customer(self, payload):
+        self.ensure_one()
+        ext = payload.get('external_id')
+        if not ext:
+            return {'status': 'error', 'error': 'external_id required'}
+        link = self.env['fusion.billing.account.link']._resolve_or_create_partner(
+            self, ext, name=payload.get('name'), email=payload.get('email'))
+        return {'status': 'ok', 'partner_id': link.partner_id.id, 'external_id': ext}
+
+    def _api_record_usage(self, payload):
+        self.ensure_one()
+        events = payload.get('events') or []
+        Usage = self.env['fusion.billing.usage']
+        accepted = 0
+        for ev in events:
+            sub = self.env['sale.order'].browse(int(ev['subscription_external_id']))
+            Usage._record_usage(
+                sub, ev['metric_code'], float(ev['quantity']),
+                ev['period_start'], ev['period_end'], idem=ev.get('idempotency_key'))
+            accepted += 1
+        return {'status': 'ok', 'accepted': accepted}
+
+    def _api_catalog(self):
+        self.ensure_one()
+        charges = self.env['fusion.billing.charge'].search([('active', '=', True)])
+        return {'status': 'ok', 'charges': [{
+            'plan_code': c.plan_code, 'metric': c.metric_id.code,
+            'included_quota': c.included_quota, 'price_per_unit': c.price_per_unit,
+            'unit_batch': c.unit_batch, 'charge_model': c.charge_model,
+        } for c in charges]}
diff --git a/fusion_centralize_billing/tests/__init__.py b/fusion_centralize_billing/tests/__init__.py
index 07117e0d..225b18dc 100644
--- a/fusion_centralize_billing/tests/__init__.py
+++ b/fusion_centralize_billing/tests/__init__.py
@@ -1,3 +1,4 @@
 from . import test_identity
 from . import test_charge
 from . import test_usage
+from . import test_api
diff --git a/fusion_centralize_billing/tests/test_api.py b/fusion_centralize_billing/tests/test_api.py
new file mode 100644
index 00000000..5ff65b2d
--- /dev/null
+++ b/fusion_centralize_billing/tests/test_api.py
@@ -0,0 +1,47 @@
+# -*- coding: utf-8 -*-
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install')
+class TestApiHandlers(TransactionCase):
+
+    def setUp(self):
+        super().setUp()
+        self.service = self.env['fusion.billing.service'].sudo().create(
+            {'name': 'NexaMaps', 'code': 'nexamaps'})
+        self.env['fusion.billing.metric'].sudo().create(
+            {'name': 'API Calls', 'code': 'api_calls', 'aggregation': 'sum'})
+        self.plan = self.env['sale.subscription.plan'].sudo().create(
+            {'name': 'Monthly', 'billing_period_value': 1, 'billing_period_unit': 'month'})
+
+    def test_api_upsert_customer(self):
+        res = self.service._api_upsert_customer(
+            {'external_id': 'client-9', 'name': 'Globex', 'email': 'billing@globex.test'})
+        self.assertEqual(res['status'], 'ok')
+        link = self.env['fusion.billing.account.link'].search(
+            [('service_id', '=', self.service.id), ('external_id', '=', 'client-9')])
+        self.assertEqual(link.partner_id.name, 'Globex')
+
+    def test_api_record_usage_batch(self):
+        self.service._api_upsert_customer({'external_id': 'client-9', 'name': 'Globex'})
+        partner = self.env['fusion.billing.account.link'].search(
+            [('external_id', '=', 'client-9')]).partner_id
+        sub = self.env['sale.order'].sudo().create(
+            {'partner_id': partner.id, 'is_subscription': True, 'plan_id': self.plan.id})
+        res = self.service._api_record_usage({'events': [{
+            'subscription_external_id': str(sub.id), 'metric_code': 'api_calls',
+            'quantity': 1234.0, 'period_start': '2026-05-01', 'period_end': '2026-06-01',
+            'idempotency_key': 'maps:client-9:2026-05-01',
+        }]})
+        self.assertEqual(res['accepted'], 1)
+        usage = self.env['fusion.billing.usage'].search([('subscription_id', '=', sub.id)])
+        self.assertEqual(usage.quantity, 1234.0)
+
+    def test_api_catalog_lists_active_charges(self):
+        self.env['fusion.billing.charge'].sudo().create({
+            'name': 'Maps overage', 'plan_code': 'maps-business',
+            'metric_id': self.env['fusion.billing.metric'].search([('code', '=', 'api_calls')]).id,
+            'included_quota': 5_000_000.0, 'price_per_unit': 0.10, 'unit_batch': 1000.0})
+        cat = self.service._api_catalog()
+        codes = [c['plan_code'] for c in cat['charges']]
+        self.assertIn('maps-business', codes)