diff --git a/packages/adcp-reporting-storage/src/adcp_reporting_storage/service.py b/packages/adcp-reporting-storage/src/adcp_reporting_storage/service.py
index a8fa46d38..8d202bfe4 100644
--- a/packages/adcp-reporting-storage/src/adcp_reporting_storage/service.py
+++ b/packages/adcp-reporting-storage/src/adcp_reporting_storage/service.py
@@ -4,7 +4,7 @@
 
 from collections.abc import Callable
 from datetime import datetime
-from typing import Any
+from typing import Any, TypeVar, overload
 
 from adcp.reporting.service import (
     ReliableReportingService,
@@ -15,6 +15,34 @@
 
 __all__ = ["postgres_reliable_reporting_service"]
 
+_ServiceT = TypeVar("_ServiceT", bound=ReliableReportingService)
+
+
+@overload
+def postgres_reliable_reporting_service(
+    *,
+    pool: Any,
+    account_context: ReportingContextResolver,
+    caller_resolver: ReportingCallerResolver | None = ...,
+    clock: Callable[[], datetime] | None = ...,
+    production: ReportingProductionOptions | None = ...,
+    service_class: None = ...,
+    **kwargs: Any,
+) -> ReliableReportingService: ...
+
+
+@overload
+def postgres_reliable_reporting_service(
+    *,
+    pool: Any,
+    account_context: ReportingContextResolver,
+    caller_resolver: ReportingCallerResolver | None = ...,
+    clock: Callable[[], datetime] | None = ...,
+    production: ReportingProductionOptions | None = ...,
+    service_class: type[_ServiceT],
+    **kwargs: Any,
+) -> _ServiceT: ...
+
 
 def postgres_reliable_reporting_service(
     *,
@@ -23,6 +51,7 @@ def postgres_reliable_reporting_service(
     caller_resolver: ReportingCallerResolver | None = None,
     clock: Callable[[], datetime] | None = None,
     production: ReportingProductionOptions | None = None,
+    service_class: type[ReliableReportingService] | None = None,
     **kwargs: Any,
 ) -> ReliableReportingService:
     """Create durable ledger, staging and seal stores over a borrowed pool.
@@ -32,6 +61,10 @@ def postgres_reliable_reporting_service(
     Startup installs all SDK-owned schemas. Explicit source-store overrides
     remain the adopter's responsibility. No pool is opened or closed here.
 
+    ``service_class`` builds an adopter's ``ReliableReportingService``
+    subclass, as ``SubClass.memory(...)`` does, so a host can override the
+    installed tool methods without copying this composition.
+
     This is what ``ReliableReportingService.postgres(...)`` was before the
     storage implementations moved to this distribution.
     """
@@ -45,7 +78,8 @@ def postgres_reliable_reporting_service(
         else PgReportingLedgerStore(pool=pool, clock=clock)
     )
     staging = PgReportingStagingStore(pool=pool)
-    return ReliableReportingService(
+    cls = ReliableReportingService if service_class is None else service_class
+    return cls(
         store=store,
         account_context=account_context,
         caller_resolver=caller_resolver,
diff --git a/tests/test_reporting_storage_service_class.py b/tests/test_reporting_storage_service_class.py
new file mode 100644
index 000000000..1e79b502a
--- /dev/null
+++ b/tests/test_reporting_storage_service_class.py
@@ -0,0 +1,35 @@
+"""``postgres_reliable_reporting_service`` builds an adopter's service subclass (#1588)."""
+
+from __future__ import annotations
+
+import pytest
+
+pytest.importorskip("psycopg_pool")
+
+from adcp_reporting_storage import postgres_reliable_reporting_service  # noqa: E402
+from psycopg_pool import AsyncConnectionPool  # noqa: E402
+
+from adcp.reporting import ReliableReportingService  # noqa: E402
+from tests.test_reliable_reporting_service import _account_context  # noqa: E402
+
+
+class HostReportingService(ReliableReportingService):
+    """A host subclass overriding an installed tool method."""
+
+
+def _pool() -> AsyncConnectionPool:
+    return AsyncConnectionPool("postgresql://unused", open=False)
+
+
+def test_default_builds_the_base_service() -> None:
+    service = postgres_reliable_reporting_service(pool=_pool(), account_context=_account_context)
+    assert type(service) is ReliableReportingService
+
+
+def test_service_class_builds_the_subclass_like_memory() -> None:
+    pg = postgres_reliable_reporting_service(
+        pool=_pool(), account_context=_account_context, service_class=HostReportingService
+    )
+    memory = HostReportingService.memory(account_context=_account_context)
+    assert type(pg) is HostReportingService
+    assert type(memory) is HostReportingService
diff --git a/tests/type_checks/reporting_storage_service_class.py b/tests/type_checks/reporting_storage_service_class.py
new file mode 100644
index 000000000..03ee37f82
--- /dev/null
+++ b/tests/type_checks/reporting_storage_service_class.py
@@ -0,0 +1,21 @@
+"""Adopter-facing type contract: the Postgres factory returns the requested subclass."""
+
+from typing import Any
+
+from adcp_reporting_storage import postgres_reliable_reporting_service
+
+from adcp.reporting import ReliableReportingService
+
+
+class HostReportingService(ReliableReportingService):
+    pass
+
+
+def build(pool: Any, account_context: Any) -> HostReportingService:
+    return postgres_reliable_reporting_service(
+        pool=pool, account_context=account_context, service_class=HostReportingService
+    )
+
+
+def build_default(pool: Any, account_context: Any) -> ReliableReportingService:
+    return postgres_reliable_reporting_service(pool=pool, account_context=account_context)