diff --git a/hub/cmd/hub/main.go b/hub/cmd/hub/main.go
index a574e94d..2eae95ec 100644
--- a/hub/cmd/hub/main.go
+++ b/hub/cmd/hub/main.go
@@ -136,6 +136,9 @@ func (m MailConfig) effectiveFromDomains() []string {
 func main() {
 	configPath := flag.String("config", "/etc/felhom-hub/hub.yaml", "Path to configuration file")
 	showVersion := flag.Bool("version", false, "Show version and exit")
+	// R-879 roll-back: open the sealed box secrets back to plaintext so a pre-R-879 hub (<= 0.137.0)
+	// can run on this database, then exit. Same -config and OFFSITE_SECRET_KEY as the server.
+	unsealBox := flag.Bool("unseal-box-secrets", false, "R-879 roll-back: unseal box API keys, passphrases and PBS tokens to plaintext, then exit")
 	flag.Parse()
 
 	if *showVersion {
@@ -188,6 +191,11 @@ func main() {
 	// that is NOT in the database (Secret/offsite-secret-key). Without it the hub cannot store, read or
 	// use any sub-account password — provisioning and the key registrar refuse (fail-closed), and the
 	// legacy plaintext rows stay as they are until the key arrives.
+	if *unsealBox {
+		code := runUnsealBoxSecrets(dataStore, logger)
+		dataStore.Close()
+		os.Exit(code)
+	}
 	offsiteKeyReady := false
 	if v := os.Getenv("OFFSITE_SECRET_KEY"); v == "" {
 		logger.Printf("[ERROR] OFFSITE_SECRET_KEY unset — off-site passwords cannot be sealed; provisioning and the key registrar are DISABLED")
@@ -1015,3 +1023,25 @@ func pruneAll(s *store.Store, maxDays int, logger *log.Logger) {
 		logger.Printf("[INFO] Pruned %d stale app issues", n)
 	}
 }
+
+// runUnsealBoxSecrets is `felhom-hub -unseal-box-secrets` (R-879 roll-back). It installs the sealing key
+// exactly as the server does, opens every sealed box secret back to plaintext (all or nothing), logs
+// counts only, and returns the process exit code. It never starts the server and never seals anything.
+func runUnsealBoxSecrets(st *store.Store, logger *log.Logger) int {
+	key, err := store.ParseOffsiteSecretKey(os.Getenv("OFFSITE_SECRET_KEY"))
+	if err != nil {
+		logger.Printf("[ERROR] unseal-box-secrets: OFFSITE_SECRET_KEY: %v — nothing changed", err)
+		return 2
+	}
+	if err := st.SetOffsiteSecretKey(key); err != nil {
+		logger.Printf("[ERROR] unseal-box-secrets: %v — nothing changed", err)
+		return 2
+	}
+	n, err := st.UnsealBoxSecrets()
+	if err != nil {
+		logger.Printf("[ERROR] unseal-box-secrets: %v", err)
+		return 1
+	}
+	logger.Printf("[INFO] unseal-box-secrets: %d sealed value(s) opened back to plaintext; a hub <= 0.137.0 can run on this database now", n)
+	return 0
+}
diff --git a/hub/cmd/hub/r879_unseal_cmd_test.go b/hub/cmd/hub/r879_unseal_cmd_test.go
new file mode 100644
index 00000000..fd1c3459
--- /dev/null
+++ b/hub/cmd/hub/r879_unseal_cmd_test.go
@@ -0,0 +1,58 @@
+package main
+
+import (
+	"bytes"
+	"database/sql"
+	"encoding/hex"
+	"log"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.dooplex.hu/admin/felhom-hub/internal/store"
+	_ "modernc.org/sqlite"
+)
+
+// R-879 roll-back command, run the way `felhom-hub -unseal-box-secrets` runs it: key from the env, exit
+// code, counts-only log. Afterwards the 0.137.0-shaped `WHERE api_key = ?` finds the box again.
+func TestR879_UnsealCommand(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "hub.db")
+	st, err := store.New(path, log.New(&bytes.Buffer{}, "", 0))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { st.Close() })
+	const hostKey = "cmd-host-key-0123456789abcdef"
+	if err := st.UpsertHost(&store.Host{HostID: "h1", CustomerID: "c1", APIKey: hostKey}); err != nil {
+		t.Fatal(err)
+	}
+	db, err := sql.Open("sqlite", path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	oldLookup := func() string {
+		var id string
+		_ = db.QueryRow(`SELECT host_id FROM hosts WHERE api_key = ?`, hostKey).Scan(&id)
+		return id
+	}
+	if oldLookup() != "" {
+		t.Fatal("precondition: the key should be sealed")
+	}
+
+	var logBuf bytes.Buffer
+	t.Setenv("OFFSITE_SECRET_KEY", "")
+	if code := runUnsealBoxSecrets(st, log.New(&logBuf, "", 0)); code == 0 {
+		t.Fatal("unseal with no key exited 0")
+	}
+	t.Setenv("OFFSITE_SECRET_KEY", hex.EncodeToString([]byte("felhom-hub-test-only-seal-key-32")))
+	if code := runUnsealBoxSecrets(st, log.New(&logBuf, "", 0)); code != 0 {
+		t.Fatalf("unseal exit = %d, log: %s", code, logBuf.String())
+	}
+	if got := oldLookup(); got != "h1" {
+		t.Fatalf("0.137.0-shaped lookup after the command = %q, want h1", got)
+	}
+	if strings.Contains(logBuf.String(), hostKey) || !strings.Contains(logBuf.String(), "1 sealed value(s) opened") {
+		t.Fatalf("log must carry the count and never the value: %s", logBuf.String())
+	}
+}
diff --git a/hub/cmd/hub/r879_wiring_test.go b/hub/cmd/hub/r879_wiring_test.go
index 9efd1d3d..3bcc5abf 100644
--- a/hub/cmd/hub/r879_wiring_test.go
+++ b/hub/cmd/hub/r879_wiring_test.go
@@ -4,6 +4,8 @@ import (
 	"go/ast"
 	"go/parser"
 	"go/token"
+	"os"
+	"strings"
 	"testing"
 )
 
@@ -27,3 +29,19 @@ func TestR879_MainSealsLegacyBoxSecrets(t *testing.T) {
 		t.Fatal("cmd/hub/main.go never calls SealLegacyBoxSecrets — legacy box secrets stay in plaintext")
 	}
 }
+
+// R-879 roll-back wiring: the -unseal-box-secrets flag must reach UnsealBoxSecrets and must exit BEFORE
+// the start-up sealing runs (otherwise the command would unseal and the same process re-seal).
+func TestR879_UnsealFlagIsWiredBeforeSealing(t *testing.T) {
+	src, err := os.ReadFile("main.go")
+	if err != nil {
+		t.Fatal(err)
+	}
+	s := string(src)
+	flagAt := strings.Index(s, `"unseal-box-secrets"`)
+	runAt := strings.Index(s, "code := runUnsealBoxSecrets(dataStore, logger)")
+	sealAt := strings.Index(s, "dataStore.SealLegacyBoxSecrets()")
+	if flagAt < 0 || runAt < 0 || sealAt < 0 || runAt > sealAt || !strings.Contains(s, "st.UnsealBoxSecrets()") {
+		t.Fatalf("unseal wiring broken: flag@%d run@%d seal@%d", flagAt, runAt, sealAt)
+	}
+}
diff --git a/hub/internal/store/r879_box_seal.go b/hub/internal/store/r879_box_seal.go
index 29e11711..59c6c840 100644
--- a/hub/internal/store/r879_box_seal.go
+++ b/hub/internal/store/r879_box_seal.go
@@ -114,18 +114,8 @@ func (s *Store) SealLegacyBoxSecrets() (int, error) {
 	if s.sealer == nil {
 		return 0, ErrNoSealKey
 	}
-	type col struct {
-		table, idCol, col string
-		withHash          bool
-	}
-	cols := []col{
-		{"hosts", "host_id", "api_key", true},
-		{"customer_configs", "customer_id", "api_key", true},
-		{"customer_configs", "customer_id", "retrieval_password", false},
-		{"host_pbs_secrets", "host_id", "value", false},
-	}
 	n := 0
-	for _, c := range cols {
+	for _, c := range r879Columns {
 		rows, err := s.db.Query(`SELECT ` + c.idCol + `, ` + c.col + ` FROM ` + c.table +
 			` WHERE ` + c.col + ` <> '' AND ` + c.col + ` NOT LIKE 'enc:v1:%'`)
 		if err != nil {
@@ -174,3 +164,75 @@ func (s *Store) sealAPIKey(key string) (sealed, hash string, err error) {
 	}
 	return sealed, hash, nil
 }
+
+// r879Columns are the four sealed box-facing columns, in one place for the seal and the reverse.
+var r879Columns = []struct {
+	table, idCol, col string
+	withHash          bool
+}{
+	{"hosts", "host_id", "api_key", true},
+	{"customer_configs", "customer_id", "api_key", true},
+	{"customer_configs", "customer_id", "retrieval_password", false},
+	{"host_pbs_secrets", "host_id", "value", false},
+}
+
+// UnsealBoxSecrets is the ROLL-BACK primitive for R-879: it opens every sealed value in the four
+// columns back to plaintext, so a hub older than R-879 (which looks keys up with `WHERE api_key = ?`
+// and serves the passphrase column as it is) works on this database again. api_key_hash is kept
+// (an older hub ignores it; a newer one re-seals at its next start).
+//
+// All or nothing: every sealed value is opened FIRST; if any one does not open (missing/wrong key,
+// corrupt) it returns an error and changes NOTHING. The writes then go in one transaction, each guarded
+// by the sealed value it read (a row rewritten meanwhile is left alone and not counted). Idempotent: a
+// second run finds nothing sealed and returns 0. Values are never logged.
+// Run by `felhom-hub -unseal-box-secrets` (cmd/hub). Pinned by TestR879_UnsealRestoresPreR879Lookup.
+func (s *Store) UnsealBoxSecrets() (int, error) {
+	if s.sealer == nil {
+		return 0, ErrNoSealKey
+	}
+	type todo struct {
+		table, idCol, col, id, sealed, plain string
+	}
+	var all []todo
+	for _, c := range r879Columns {
+		rows, err := s.db.Query(`SELECT ` + c.idCol + `, ` + c.col + ` FROM ` + c.table + ` WHERE ` + c.col + ` LIKE 'enc:v1:%'`)
+		if err != nil {
+			return 0, fmt.Errorf("%s.%s: %w", c.table, c.col, err)
+		}
+		for rows.Next() {
+			t := todo{table: c.table, idCol: c.idCol, col: c.col}
+			if err := rows.Scan(&t.id, &t.sealed); err != nil {
+				rows.Close()
+				return 0, err
+			}
+			all = append(all, t)
+		}
+		rows.Close()
+	}
+	for i := range all {
+		pt, err := s.openSecret(all[i].sealed)
+		if err != nil {
+			return 0, fmt.Errorf("%s.%s for %s does not open — nothing was changed: %w", all[i].table, all[i].col, all[i].id, err)
+		}
+		all[i].plain = pt
+	}
+	tx, err := s.db.Begin()
+	if err != nil {
+		return 0, err
+	}
+	defer tx.Rollback()
+	n := 0
+	for _, t := range all {
+		res, err := tx.Exec(`UPDATE `+t.table+` SET `+t.col+` = ? WHERE `+t.idCol+` = ? AND `+t.col+` = ?`, t.plain, t.id, t.sealed)
+		if err != nil {
+			return 0, fmt.Errorf("%s.%s: %w", t.table, t.col, err)
+		}
+		if k, _ := res.RowsAffected(); k > 0 {
+			n++
+		}
+	}
+	if err := tx.Commit(); err != nil {
+		return 0, err
+	}
+	return n, nil
+}
diff --git a/hub/internal/store/r879_box_seal_test.go b/hub/internal/store/r879_box_seal_test.go
index 19dddd0d..7455e84c 100644
--- a/hub/internal/store/r879_box_seal_test.go
+++ b/hub/internal/store/r879_box_seal_test.go
@@ -288,3 +288,54 @@ func TestR879_BoxAuthSurvivesFailedSealing(t *testing.T) {
 		t.Fatal("the stored passphrase was damaged while the key was wrong")
 	}
 }
+
+// The roll-back: after UnsealBoxSecrets a hub older than R-879 works on the database again — its lookup
+// is literally `WHERE api_key = ?`, and it serves retrieval_password / host_pbs_secrets.value as stored.
+// With a wrong key nothing changes; a second run is a no-op.
+func TestR879_UnsealRestoresPreR879Lookup(t *testing.T) {
+	st := sealTestStore(t)
+	r879Seed(t, st)
+	before := r879Raw(t, st, `SELECT api_key FROM hosts WHERE host_id='h1'`)
+
+	// Wrong key: refused, all or nothing.
+	if err := st.SetOffsiteSecretKey([]byte("another-key-of-exactly-32-bytes!")); err != nil {
+		t.Fatal(err)
+	}
+	if n, err := st.UnsealBoxSecrets(); err == nil || n != 0 {
+		t.Fatalf("UnsealBoxSecrets with a wrong key = %d, %v — want a refusal", n, err)
+	}
+	if got := r879Raw(t, st, `SELECT api_key FROM hosts WHERE host_id='h1'`); got != before {
+		t.Fatal("a refused unseal changed a row")
+	}
+	if err := st.SetOffsiteSecretKey([]byte("felhom-hub-test-only-seal-key-32")); err != nil {
+		t.Fatal(err)
+	}
+
+	n, err := st.UnsealBoxSecrets()
+	if err != nil || n != 4 {
+		t.Fatalf("UnsealBoxSecrets = %d, %v — want the four sealed values", n, err)
+	}
+	// The 0.137.0-shaped queries, verbatim.
+	if got := r879Raw(t, st, `SELECT host_id FROM hosts WHERE api_key = ?`, r879HostKey); got != "h1" {
+		t.Fatalf("pre-R-879 host lookup found %q", got)
+	}
+	if got := r879Raw(t, st, `SELECT customer_id FROM customer_configs WHERE api_key = ?`, r879CustKey); got != "c1" {
+		t.Fatalf("pre-R-879 controller lookup found %q", got)
+	}
+	if got := r879Raw(t, st, `SELECT retrieval_password FROM customer_configs WHERE customer_id='c1'`); got != r879Pass {
+		t.Fatalf("passphrase column after unseal = %q", got)
+	}
+	if got := r879Raw(t, st, `SELECT value FROM host_pbs_secrets WHERE host_id='h1'`); got != r879PBSToken {
+		t.Fatalf("PBS token column after unseal = %q", got)
+	}
+	if n, err := st.UnsealBoxSecrets(); err != nil || n != 0 {
+		t.Fatalf("second UnsealBoxSecrets = %d, %v — want a no-op", n, err)
+	}
+	// And forward again: the current code still authenticates, and a re-seal works.
+	if h, _ := st.GetHostByAPIKey(r879HostKey); h == nil {
+		t.Fatal("after an unseal the current hub no longer authenticates the box")
+	}
+	if n, err := st.SealLegacyBoxSecrets(); err != nil || n != 4 {
+		t.Fatalf("re-seal after unseal = %d, %v", n, err)
+	}
+}