email-connect/deploy/caller-rollout/user-engine-mail-bindings.patch

--- /dev/null
+++ b/src/user_engine/mail_bindings.py
@@ -0,0 +1,40 @@
+"""Explicit tenant globs for the scoped invitation mail transport."""
+
+from __future__ import annotations
+
+import json
+import re
+from fnmatch import fnmatchcase
+
+IDENTIFIER = re.compile(r"[A-Za-z0-9][A-Za-z0-9._:-]{0,127}\Z")
+PATTERN = re.compile(r"[A-Za-z0-9*?][A-Za-z0-9._:*?-]{0,127}\Z")
+
+
+def load_mail_client_bindings(raw):
+    if raw is None:
+        return None
+    try:
+        rows = json.loads(raw)
+        if not isinstance(rows, list) or not 1 <= len(rows) <= 128:
+            raise ValueError
+        result = []
+        for row in rows:
+            if (not isinstance(row, list) or len(row) != 2
+                    or not isinstance(row[0], str) or not PATTERN.fullmatch(row[0])
+                    or not isinstance(row[1], str) or not IDENTIFIER.fullmatch(row[1])):
+                raise ValueError
+            result.append(tuple(row))
+        if len({row[0] for row in result}) != len(result):
+            raise ValueError
+        return tuple(result)
+    except (ValueError, TypeError):
+        raise ValueError("mail_client_bindings_invalid") from None
+
+
+def mail_client_for(tenant, bindings):
+    if not isinstance(tenant, str) or not IDENTIFIER.fullmatch(tenant):
+        raise ValueError("mail_binding_denied")
+    matches = {client for pattern, client in bindings if fnmatchcase(tenant, pattern)}
+    if len(matches) != 1:
+        raise ValueError("mail_binding_denied")
+    return matches.pop()
--- a/src/user_engine/adapters/delivery.py
+++ b/src/user_engine/adapters/delivery.py
@@ -19,6 +19,7 @@
 
 
 from user_engine.domain import OutboxEvent
+from user_engine.mail_bindings import load_mail_client_bindings, mail_client_for
 
 _MAIL_EVENTS = {"family_member.invited", "family_invitation.resent"}
 
@@ -34,12 +35,14 @@
         mail_url: str | None = None,
         mail_bearer_token: str | None = None,
         timeout_seconds: float = 5.0,
+        mail_client_bindings: str | None = None,
     ) -> None:
         self.event_url = event_url
         self.mail_url = mail_url
         self.event_bearer_token = event_bearer_token
         self.mail_bearer_token = mail_bearer_token
         self.timeout_seconds = timeout_seconds
+        self.mail_client_bindings = load_mail_client_bindings(mail_client_bindings)
 
     def __call__(self, event: OutboxEvent) -> None:
         envelope = {
@@ -57,7 +60,15 @@
         if self.mail_url and event.event_type in _MAIL_EVENTS:
             if not self.mail_bearer_token:
                 raise RuntimeError("mail delivery token is required")
-            self._post(self.mail_url, envelope, self.mail_bearer_token)
+            mail_envelope = dict(envelope)
+            if self.mail_client_bindings is not None:
+                try:
+                    mail_envelope["client_id"] = mail_client_for(
+                        event.tenant, self.mail_client_bindings
+                    )
+                except ValueError:
+                    raise DeliveryError("mail_binding_denied") from None
+            self._post(self.mail_url, mail_envelope, self.mail_bearer_token)
         event_envelope = dict(envelope)
         event_data = dict(envelope["data"])
         if "primary_email" in event_data:
--- a/src/user_engine/runtime.py
+++ b/src/user_engine/runtime.py
@@ -65,6 +65,7 @@
             else None
         ),
         timeout_seconds=float(os.environ.get("USER_ENGINE_DELIVERY_TIMEOUT", "5")),
+        mail_client_bindings=os.environ.get("USER_ENGINE_MAIL_CLIENT_BINDINGS"),
     )
     app = PortalApplication(
         service,
--- /dev/null
+++ b/tests/test_mail_bindings.py
@@ -0,0 +1,73 @@
+"""Scoped mail migration uses synthetic identities and a mocked HTTP boundary."""
+
+import json
+import unittest
+from unittest.mock import patch
+
+from user_engine.adapters.delivery import HTTPOutboxDeliveryAdapter, DeliveryError
+from user_engine.domain import OutboxEvent
+from user_engine.mail_bindings import load_mail_client_bindings, mail_client_for
+
+
+class MailBindingsTests(unittest.TestCase):
+    def test_whole_case_sensitive_globs_and_literal_clients(self):
+        bindings = load_mail_client_bindings('[ ["tenant:*-family", "coulomb-social"] ]')
+        self.assertEqual(mail_client_for("tenant:synthetic-family", bindings), "coulomb-social")
+        for tenant in ("tenant:platform", "tenant:Synthetic-Family", "tenant:x-family/path"):
+            with self.assertRaisesRegex(ValueError, "mail_binding_denied"):
+                mail_client_for(tenant, bindings)
+
+    def test_invalid_configuration_never_falls_back(self):
+        for raw in ('', '[]', '{}', '[["*", "*"]]', '[["[a]", "client"]]',
+                    '[["*", "one"], ["*", "two"]]', '[[true, "client"]]'):
+            with self.assertRaisesRegex(ValueError, "mail_client_bindings_invalid"):
+                load_mail_client_bindings(raw)
+        self.assertIsNone(load_mail_client_bindings(None))
+
+    def test_conflicting_overlaps_are_denied(self):
+        bindings = load_mail_client_bindings('[["tenant:*", "one"], ["tenant:x", "two"]]')
+        with self.assertRaisesRegex(ValueError, "mail_binding_denied"):
+            mail_client_for("tenant:x", bindings)
+
+    def adapter(self, bindings=None):
+        return HTTPOutboxDeliveryAdapter(event_url="http://events.example.test",
+            event_bearer_token="synthetic-event-token", mail_url="http://mail.example.test",
+            mail_bearer_token="synthetic-mail-token", mail_client_bindings=bindings)
+
+    def event(self, kind="family_member.invited", tenant="tenant:synthetic-family"):
+        return OutboxEvent(event_id="evt-synthetic", event_type=kind, aggregate_id="inv-synthetic",
+            payload={"primary_email": "member@example.test", "invitation_id": "inv-synthetic"},
+            tenant=tenant, correlation_id="trace-synthetic")
+
+    def test_binding_only_changes_mail_transport_not_event_or_outbox(self):
+        event = self.event()
+        adapter = self.adapter('[["tenant:*-family", "coulomb-social"]]')
+        with patch.object(adapter, "_post") as post:
+            adapter(event)
+        mail, audit = [call.args[1] for call in post.call_args_list]
+        self.assertEqual(mail["client_id"], "coulomb-social")
+        self.assertNotIn("client_id", audit)
+        self.assertNotIn("primary_email", audit["data"])
+        self.assertNotIn("client_id", event.payload)
+        self.assertEqual(mail["id"], event.event_id)
+
+    def test_legacy_mode_and_non_mail_events_preserve_envelopes(self):
+        adapter = self.adapter()
+        with patch.object(adapter, "_post") as post:
+            adapter(self.event())
+        self.assertNotIn("client_id", post.call_args_list[0].args[1])
+        adapter = self.adapter('[["tenant:*-family", "coulomb-social"]]')
+        with patch.object(adapter, "_post") as post:
+            adapter(self.event("membership.added", "tenant:platform"))
+        self.assertEqual(post.call_count, 1)
+
+    def test_unadmitted_mail_tenant_contacts_neither_lane(self):
+        adapter = self.adapter('[["tenant:*-family", "coulomb-social"]]')
+        with patch.object(adapter, "_post") as post:
+            with self.assertRaisesRegex(DeliveryError, "mail_binding_denied"):
+                adapter(self.event(tenant="tenant:platform"))
+        post.assert_not_called()
+
+
+if __name__ == "__main__":
+    unittest.main()