diff --git a/changelog/unreleased/fix-log-data-path-at-startup.md b/changelog/unreleased/fix-log-data-path-at-startup.md
new file mode 100644
index 00000000000..b3232e8411a
--- /dev/null
+++ b/changelog/unreleased/fix-log-data-path-at-startup.md
@@ -0,0 +1,10 @@
+Enhancement: Log effective data and config paths at startup
+
+oCIS now logs the effective data path and config path at startup so
+operators can immediately verify that data is written to the expected
+location. This helps catch misconfigured Docker volume mounts where
+data silently falls back to an ephemeral container path instead of
+the intended persistent mount.
+
+https://github.com/owncloud/ocis/pull/XXXX
+https://github.com/owncloud/ocis/issues/12044
diff --git a/ocis/pkg/runtime/service/service.go b/ocis/pkg/runtime/service/service.go
index 14478ebe49a..145a1a9e394 100644
--- a/ocis/pkg/runtime/service/service.go
+++ b/ocis/pkg/runtime/service/service.go
@@ -27,6 +27,7 @@ import (
 	"github.com/thejerf/suture/v4"
 
 	ociscfg "github.com/owncloud/ocis/v2/ocis-pkg/config"
+	"github.com/owncloud/ocis/v2/ocis-pkg/config/defaults"
 	"github.com/owncloud/ocis/v2/ocis-pkg/log"
 	ogrpc "github.com/owncloud/ocis/v2/ocis-pkg/service/grpc"
 	"github.com/owncloud/ocis/v2/ocis-pkg/shared"
@@ -370,6 +371,13 @@ func Start(ctx context.Context, o ...Option) error {
 		return err
 	}
 
+	// Log the effective data and config paths at startup so operators can
+	// verify that data is written to the expected location.
+	s.Log.Info().
+		Str("data_path", defaults.BaseDataPath()).
+		Str("config_path", defaults.BaseConfigPath()).
+		Msg("effective data and config paths")
+
 	// cancel the context when a signal is received.
 	var cancel context.CancelFunc = func() {}
 	if ctx == nil {