From 7dfe5b37202266f5f0ec1c57aca7838a85f09b7d Mon Sep 17 00:00:00 2001
From: Egor Seredin <4819888+agmt@users.noreply.github.com>
Date: Wed, 22 Apr 2026 02:37:43 +0000
Subject: [PATCH 1/2] Test: body field after nested repeating group

---
 message_test.go | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/message_test.go b/message_test.go
index 72f11dcd0..4a1b51a21 100644
--- a/message_test.go
+++ b/message_test.go
@@ -113,6 +113,48 @@ func (s *MessageSuite) TestParseOutOfOrder() {
 	s.Nil(ParseMessage(s.msg, rawMsg))
 }
 
+func (s *MessageSuite) TestParseGroup_BodyFieldAfterNestedGroup() {
+	dict, dictErr := datadictionary.Parse("spec/FIX44.xml")
+	s.Nil(dictErr)
+
+	// Wire layout (FIX 4.4 MassQuoteAcknowledgement):
+	//   117=QID              QuoteID (body)
+	//   296=1                NoQuoteSets count (body group)
+	//     302=SET1           QuoteSetID (inside NoQuoteSets)
+	//     295=1              NoQuoteEntries count (nested group)
+	//       299=E1           QuoteEntryID (inside NoQuoteEntries)
+	//       132=100          BidPx (inside NoQuoteEntries)
+	//       133=101          OfferPx (inside NoQuoteEntries)
+	//   297=0                QuoteStatus (BODY level, AFTER the group)
+	rawMsg := bytes.NewBufferString(
+		"8=FIX.4.4
9=63
35=b
117=QID
" +
+			"296=1
302=SET1
" +
+			"295=1
299=E1
132=100
133=101
" +
+			"297=1
" +
+			"10=002
")
+
+	err := ParseMessageWithDataDictionary(s.msg, rawMsg, dict, dict)
+	s.Nil(err)
+
+	rebuildBytes := s.msg.build()
+	expectedBytes := rawMsg.Bytes()
+	s.True(bytes.Equal(expectedBytes, rebuildBytes), "Unexpected bytes,\n +%s\n -%s", rebuildBytes, expectedBytes)
+
+	// NoQuoteSets count (group delimiter) lands in Body as expected.
+	s.True(s.msg.Body.Has(Tag(296)))
+
+	// ToDo: should be correct — QuoteStatus (297) must be a top-level body
+	// field per FIX 4.4. Current parseGroup logic silently absorbs 297 into
+	// the NoQuoteSets group buffer because it only checks whether the
+	// parent tag is a NumInGroup, not whether 297 is a member of the
+	// parent group template.
+	s.False(s.msg.Body.Has(Tag(297)),
+		"BUG: QuoteStatus (297) is absent from Body.FieldMap — parser "+
+			"mis-attributed it to the parent NoQuoteSets group. This "+
+			"assertion documents the bug; flip to s.True(...) when "+
+			"parseGroup is fixed.")
+}
+
 func (s *MessageSuite) TestBuild() {
 	s.msg.Header.SetField(tagBeginString, FIXString(BeginStringFIX44))
 	s.msg.Header.SetField(tagMsgType, FIXString("A"))

From 57fef4cc7f3ce91d63fd61090fb76ac3d78880e9 Mon Sep 17 00:00:00 2001
From: Egor Seredin <4819888+agmt@users.noreply.github.com>
Date: Wed, 22 Apr 2026 02:41:27 +0000
Subject: [PATCH 2/2] parseGroup: stop misattributing body fields after nested
 groups

---
 message.go      | 20 ++++++++++----------
 message_test.go | 17 +++++++----------
 2 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/message.go b/message.go
index 5bea1d375..550f68fb0 100644
--- a/message.go
+++ b/message.go
@@ -310,6 +310,7 @@ func parseGroup(mp *msgParser, tags []Tag) {
 	dm := mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1]
 	fields := getGroupFields(mp.msg, tags, mp.appDataDictionary)
 
+parseLoop:
 	for {
 		mp.fieldIndex++
 		mp.parsedFieldBytes = &mp.msg.fields[mp.fieldIndex]
@@ -350,16 +351,15 @@ func parseGroup(mp *msgParser, tags []Tag) {
 				fields = getGroupFields(mp.msg, searchTags, mp.appDataDictionary)
 				continue
 			}
-			if len(tags) > 1 {
-				searchTags = tags[:len(tags)-1]
-			}
-			// Did this tag occur after a nested group and belongs to the parent group.
-			if isNumInGroupField(mp.msg, searchTags, mp.appDataDictionary) {
-				// Add the field member to the group.
-				dm = append(dm, *mp.parsedFieldBytes)
-				// Continue parsing the parent group.
-				fields = getGroupFields(mp.msg, searchTags, mp.appDataDictionary)
-				continue
+			// The tag isn't a member of the current group. Walk up: if an
+			// ancestor group includes it, resume there; otherwise it's body-level.
+			for len(tags) > 1 {
+				tags = tags[:len(tags)-1]
+				fields = getGroupFields(mp.msg, tags, mp.appDataDictionary)
+				if isGroupMember(mp.parsedFieldBytes.tag, fields) {
+					dm = append(dm, *mp.parsedFieldBytes)
+					continue parseLoop
+				}
 			}
 			// Add the repeating group.
 			mp.msg.Body.add(dm)
diff --git a/message_test.go b/message_test.go
index 4a1b51a21..7bdd3af37 100644
--- a/message_test.go
+++ b/message_test.go
@@ -143,16 +143,13 @@ func (s *MessageSuite) TestParseGroup_BodyFieldAfterNestedGroup() {
 	// NoQuoteSets count (group delimiter) lands in Body as expected.
 	s.True(s.msg.Body.Has(Tag(296)))
 
-	// ToDo: should be correct — QuoteStatus (297) must be a top-level body
-	// field per FIX 4.4. Current parseGroup logic silently absorbs 297 into
-	// the NoQuoteSets group buffer because it only checks whether the
-	// parent tag is a NumInGroup, not whether 297 is a member of the
-	// parent group template.
-	s.False(s.msg.Body.Has(Tag(297)),
-		"BUG: QuoteStatus (297) is absent from Body.FieldMap — parser "+
-			"mis-attributed it to the parent NoQuoteSets group. This "+
-			"assertion documents the bug; flip to s.True(...) when "+
-			"parseGroup is fixed.")
+	// QuoteStatus (297) must be a top-level body field per FIX 4.4.
+	s.True(s.msg.Body.Has(Tag(297)),
+		"QuoteStatus (297) must land at the body level; it is a body field "+
+			"in MassQuoteAcknowledgement, not a member of NoQuoteSets.")
+	val, verr := s.msg.Body.GetInt(Tag(297))
+	s.Nil(verr)
+	s.Equal(1, val)
 }
 
 func (s *MessageSuite) TestBuild() {