diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7126de6..aac2e0c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,27 @@
 ## Changelog
 
+### v0.52.0 — Phase 1 GATE: deploy-side double-nest fix + path-agreement lock (2026-06-13)
+
+Completes the Model-A double-nest reconciliation deferred in v0.48.0. v0.51.0 fixed the **backup
+helper** side (`NamespaceRoot` provenance); the **deploy/compose** side still wrote one segment too
+deep. On a Model-A in-guest drive the guest mount `/mnt/<drive>` already IS the host's
+`<drive>/felhom-data` namespace, so the catalog templates' `${HDD_PATH}/felhom-data/appdata/<app>`
+double-nested to `.../felhom-data/felhom-data/...` on disk — diverging from where the backup helpers
+look (`AppDataDir(NamespaceRoot(HDD_PATH,true))`, single-nested).
+
+- **Fix lives in the app catalog** (`app-catalog-felhom.eu`): all four HDD app templates
+  (`romm`, `nextcloud`, `immich`, `paperless-ngx`) changed `${HDD_PATH}/felhom-data/appdata/<app>` →
+  `${HDD_PATH}/appdata/<app>`. The controller passes `HDD_PATH` through verbatim and never appended
+  the segment, so no controller runtime change was needed. Catalog change lands via git-sync /
+  "Sablonok frissítése".
+- **Agreement test (new):** `internal/stacks/hddpath_agreement_test.go` resolves a compose's
+  `${HDD_PATH}` bind mounts via the real deploy-side `ParseComposeHDDMounts` and asserts they are
+  byte-identical to the backup-side `AppDataDir(NamespaceRoot(HDD_PATH,true))` — no doubled
+  `felhom-data`, deploy and backup locked together so they cannot drift again.
+- **Live migration:** existing drive-resident apps whose data sat at the doubled
+  `…/felhom-data/felhom-data/appdata/<app>` are migrated (stop → move → verify → redeploy) to the
+  single-nested path (RomM confirmed on the demo guest).
+
 ### v0.51.0 — offsite-backup UI (felhom-pbs DR) + Model-A double-nest fix (2026-06-12)
 
 Pairs with felhom-agent v0.28.0 (whole-guest backup re-targeted to the offsite PBS tier).
diff --git a/controller/internal/stacks/hddpath_agreement_test.go b/controller/internal/stacks/hddpath_agreement_test.go
new file mode 100644
index 0000000..bd98a09
--- /dev/null
+++ b/controller/internal/stacks/hddpath_agreement_test.go
@@ -0,0 +1,69 @@
+package stacks_test
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.dooplex.hu/admin/felhom-controller/internal/appbackup"
+	"gitea.dooplex.hu/admin/felhom-controller/internal/stacks"
+)
+
+// TestDeployPathAgreesWithBackupHelpers is the Phase-1 GATE invariant: the host path an app actually
+// writes to — resolved from its compose ${HDD_PATH} bind mounts, exactly as deploy does — must be
+// byte-identical to where the app-data backup helpers look. Single-nested, no doubled felhom-data.
+//
+// Before the fix, catalog templates used ${HDD_PATH}/felhom-data/appdata/<app>. On a Model-A in-guest
+// drive the guest mount /mnt/<drive> ALREADY is the host's <drive>/felhom-data namespace, so that extra
+// segment produced .../felhom-data/felhom-data/... on disk, while NamespaceRoot(drive, true) resolved
+// the single-nested .../appdata/<app>. Deploy and backup disagreed. The catalog templates now use
+// ${HDD_PATH}/appdata/<app>; this test locks the two sides together so they can't drift again.
+func TestDeployPathAgreesWithBackupHelpers(t *testing.T) {
+	const hddPath = "/mnt/felhom-usb" // an enrolled in-guest drive mount (basename is NOT felhom-data)
+	const app = "romm"
+
+	// A compose volumes block in the FIXED form (no felhom-data segment), mirroring the catalog template.
+	compose := "services:\n" +
+		"  romm:\n" +
+		"    volumes:\n" +
+		"      - ${HDD_PATH}/appdata/romm/library:/romm/library\n" +
+		"      - ${HDD_PATH}/appdata/romm/resources:/romm/resources\n" +
+		"      - romm_config:/romm/config\n" +
+		"volumes:\n" +
+		"  romm_config:\n"
+
+	dir := t.TempDir()
+	composePath := filepath.Join(dir, "docker-compose.yml")
+	if err := os.WriteFile(composePath, []byte(compose), 0600); err != nil {
+		t.Fatalf("writing temp compose: %v", err)
+	}
+
+	// Deploy side: where the app's bytes actually land (named volume romm_config is correctly excluded).
+	mounts := stacks.ParseComposeHDDMounts(composePath, hddPath)
+	if len(mounts) != 2 {
+		t.Fatalf("expected 2 HDD bind mounts, got %d: %v", len(mounts), mounts)
+	}
+
+	// Backup side: the app-data dir the helpers resolve for the same in-guest drive.
+	ns := appbackup.NamespaceRoot(hddPath, true) // in-guest Model-A drive → mount as-is, no felhom-data
+	wantAppDir := filepath.ToSlash(appbackup.AppDataDir(ns, app))
+	if wantAppDir != "/mnt/felhom-usb/appdata/romm" {
+		t.Fatalf("backup app-data dir unexpected: %q", wantAppDir)
+	}
+
+	for _, m := range mounts {
+		s := filepath.ToSlash(m)
+		// (1) No doubled felhom-data, and in guest-path space no felhom-data segment at all.
+		if strings.Contains(s, appbackup.FelhomDataDir+"/"+appbackup.FelhomDataDir) {
+			t.Errorf("deploy mount double-nests felhom-data: %q", s)
+		}
+		if n := strings.Count(s, appbackup.FelhomDataDir); n > 0 {
+			t.Errorf("deploy mount unexpectedly carries %d felhom-data segment(s): %q", n, s)
+		}
+		// (2) Every app bind mount lives under the backup helpers' app-data dir — deploy and backup agree.
+		if !strings.HasPrefix(s, wantAppDir+"/") {
+			t.Errorf("deploy mount %q is not under backup app-data dir %q — the two sides diverge", s, wantAppDir)
+		}
+	}
+}