From a603c0c57c9d259827fdfb954d2a67b493e341e0 Mon Sep 17 00:00:00 2001
From: Alberto Caliva <alberto.caliva@cern.ch>
Date: Thu, 23 Jul 2026 21:06:42 +0200
Subject: [PATCH] Fix seg fault caused by stale particle indices after
 coalescence from HF decays

---
 MC/config/common/external/generator/CoalescencePythia8.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/MC/config/common/external/generator/CoalescencePythia8.h b/MC/config/common/external/generator/CoalescencePythia8.h
index 7e4abc53e..270184a73 100644
--- a/MC/config/common/external/generator/CoalescencePythia8.h
+++ b/MC/config/common/external/generator/CoalescencePythia8.h
@@ -152,6 +152,9 @@ bool CoalescencePythia8(Pythia8::Event& event, std::vector<unsigned int> inputPd
       for (int iN{0}; iN < neutrons[iC].size(); ++iN) {
         if (nuclearMask & (1 << kDeuteron)) {
           coalHappened |= doCoal(event, iC, pdgList[kDeuteron], massList[kDeuteron], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], neutrons[iC][iN]);
+          if (nuclFromDecay && coalHappened) {
+            return true;
+          }
         }
         if (nuclearMask & (1 << kTriton)) {
           for (int iN2{iN + 1}; iN2 < neutrons[iC].size(); ++iN2) {