diff --git a/weed/server/master_block_failover.go b/weed/server/master_block_failover.go
index ada422c79..0afbe6f41 100644
--- a/weed/server/master_block_failover.go
+++ b/weed/server/master_block_failover.go
@@ -54,8 +54,7 @@ type FailoverVolumeState struct {
 // Volume-oriented: each entry describes one volume's failover state.
 // Aggregate counts are derived from the volume list.
 type FailoverDiagnostic struct {
-	V2PromotionEnabled   bool           // T3: whether durability-first V2 promotion is active
-	V2PromotionReady     bool           // T3: whether V2 evidence querier is wired (false = fail-closed placeholder)
+	V2PromotionMode      string         // T3: "disabled", "placeholder_fail_closed", "transport_ready"
 	Volumes              []FailoverVolumeState
 	PendingRebuildCount  map[string]int // dead server → count of pending rebuilds
 	DeferredPromotionCount map[string]int // dead server → count of deferred promotion timers
@@ -99,8 +98,14 @@ func (fs *blockFailoverState) DiagnosticSnapshot() FailoverDiagnostic {
 // V2 promotion rollout state so operators can observe the active mode.
 func (ms *MasterServer) FailoverDiagnosticSnapshot() FailoverDiagnostic {
 	diag := ms.blockFailover.DiagnosticSnapshot()
-	diag.V2PromotionEnabled = ms.blockV2Promotion
-	diag.V2PromotionReady = ms.blockV2Promotion && ms.blockVSQueryEvidence != nil
+	switch {
+	case !ms.blockV2Promotion:
+		diag.V2PromotionMode = "disabled"
+	case ms.blockV2EvidenceTransport:
+		diag.V2PromotionMode = "transport_ready"
+	default:
+		diag.V2PromotionMode = "placeholder_fail_closed"
+	}
 	return diag
 }
 
diff --git a/weed/server/master_server.go b/weed/server/master_server.go
index 868d69b66..0fbb775c4 100644
--- a/weed/server/master_server.go
+++ b/weed/server/master_server.go
@@ -110,9 +110,10 @@ type MasterServer struct {
 	blockVSPrepareExpand func(ctx context.Context, server string, name string, newSize, expandEpoch uint64) error
 	blockVSCommitExpand  func(ctx context.Context, server string, name string, expandEpoch uint64) (uint64, error)
 	blockVSCancelExpand  func(ctx context.Context, server string, name string, expandEpoch uint64) error
-	blockVSQueryEvidence BlockPromotionEvidenceQuerier // T2: fresh on-demand promotion evidence
-	nextExpandEpoch      atomic.Uint64
-	blockV2Promotion     bool // T3: when true, use durability-first V2 promotion; when false, legacy V1
+	blockVSQueryEvidence      BlockPromotionEvidenceQuerier // T2: fresh on-demand promotion evidence
+	blockV2EvidenceTransport  bool                          // T3: true only when real gRPC querier is installed (not placeholder)
+	nextExpandEpoch           atomic.Uint64
+	blockV2Promotion          bool // T3: when true, use durability-first V2 promotion; when false, legacy V1
 
 	// Test-only hook: called after AcquireExpandInflight but before the
 	// re-read Lookup in coordinated expand. Nil in production.