From f2a1e52d9ce05dacbe01f65c7b3f4e3d06847ad2 Mon Sep 17 00:00:00 2001
From: T1nyBear <324255370+T1nyBear@users.noreply.github.com>
Date: Fri, 4 Sep 2026 05:43:19 +0200
Subject: [PATCH] fix randomized X25519MLKEM768 key share consistency

---
 u_parrots.go | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/u_parrots.go b/u_parrots.go
index 8416fa3363..aa162d2e25 100644
--- a/u_parrots.go
+++ b/u_parrots.go
@@ -3339,7 +3339,8 @@ func generateRandomizedSpec(
 	points := SupportedPointsExtension{SupportedPoints: []byte{pointFormatUncompressed}}
 
 	curveIDs := []CurveID{}
-	if r.FlipWeightedCoin(id.Weights.CurveIDs_Append_X25519) && p.TLSVersMax == VersionTLS13 {
+	includeX25519MLKEM768 := r.FlipWeightedCoin(id.Weights.CurveIDs_Append_X25519) && p.TLSVersMax == VersionTLS13
+	if includeX25519MLKEM768 {
 		curveIDs = append(curveIDs, X25519MLKEM768)
 	}
 	if r.FlipWeightedCoin(id.Weights.CurveIDs_Append_X25519) || p.TLSVersMax == VersionTLS13 {
@@ -3399,9 +3400,11 @@ func generateRandomizedSpec(
 			if r.FlipWeightedCoin(id.Weights.KeyShare_Append_RandomGroups) {
 				ks.KeyShares = append(ks.KeyShares, KeyShare{Group: CurveP256})
 			}
-			if r.FlipWeightedCoin(id.Weights.KeyShare_Append_RandomGroups) {
-				ks.KeyShares = append([]KeyShare{{Group: X25519MLKEM768}}, ks.KeyShares...)
-			}
+			// Preserve PRNG progression for existing randomized seeds.
+			_ = r.FlipWeightedCoin(id.Weights.KeyShare_Append_RandomGroups)
+		}
+		if includeX25519MLKEM768 {
+			ks.KeyShares = append([]KeyShare{{Group: X25519MLKEM768}}, ks.KeyShares...)
 		}
 		pskExchangeModes := PSKKeyExchangeModesExtension{[]uint8{pskModeDHE}}
 		supportedVersionsExt := SupportedVersionsExtension{