diff --git a/internal/ctxmgr/semantic_summary.go b/internal/ctxmgr/semantic_summary.go
index d8ab6e58..de8d72ab 100644
--- a/internal/ctxmgr/semantic_summary.go
+++ b/internal/ctxmgr/semantic_summary.go
@@ -253,7 +253,9 @@ func applySemanticShadow(ctx context.Context, sum *ChatSummary, msgs []ChatMessa
 	if report.Protocol == "" {
 		report.Protocol = semanticProtocolV1
 	}
-	// Explicitly do NOT swap sum.Narrative even if REPLACE env is true.
+	// Explicitly do NOT swap sum.Narrative even if REPLACE env is true
+	// (Wave 5 X-2 sealed; see wave5-deadcode-decisions.md#x-2).
+	// Keep the call so envBool parsing stays covered; do not "fix" by wiring REPLACE.
 	_ = SemanticSummaryReplaceEnabled()
 	sum.Shadow = report
 }
diff --git a/internal/ctxmgr/summary_flags.go b/internal/ctxmgr/summary_flags.go
index 31bf2764..c6d43a26 100644
--- a/internal/ctxmgr/summary_flags.go
+++ b/internal/ctxmgr/summary_flags.go
@@ -7,12 +7,18 @@ import (
 )
 
 const (
-	EnvSemanticSummaryShadow  = "SEMANTIC_SUMMARY_SHADOW"
+	EnvSemanticSummaryShadow = "SEMANTIC_SUMMARY_SHADOW"
+	// SEALED (Wave 5 X-2, 2026-09-18): REPLACE must stay unwired indefinitely per
+	// system-health-remediation-plan.md Wave5 + red-line "SEMANTIC_SUMMARY_REPLACE
+	// 不接线". Enabling REPLACE to swap served narrative requires a separate
+	// explicit user authorization + fail-closed rollout design; do not wire it as
+	// a side effect of an unrelated change. See .doc/ops/short-term/2026-09-18-
+	// wave5-deadcode-decisions.md#x-2.
 	EnvSemanticSummaryReplace = "SEMANTIC_SUMMARY_REPLACE"
 )
 
 // SummaryFeatureFlags controls semantic summary rollout.
-// REPLACE is reserved and must remain unwired in PU6 shadow delivery.
+// REPLACE is reserved and must remain unwired in PU6 shadow delivery (Wave 5 X-2 sealed).
 type SummaryFeatureFlags struct {
 	Shadow  bool
 	Replace bool
@@ -51,7 +57,8 @@ func SemanticSummaryShadowEnabled() bool {
 }
 
 // SemanticSummaryReplaceEnabled reports the REPLACE env bit.
-// PU6 must not use this to swap the served deterministic narrative.
+// SEALED (Wave 5 X-2): PU6 must not use this to swap the served deterministic narrative.
+// See .doc/ops/short-term/2026-09-18-wave5-deadcode-decisions.md#x-2.
 func SemanticSummaryReplaceEnabled() bool {
 	return CurrentSummaryFlags().Replace
 }