From 6029db28e244d9a95375386cd2b9a07d3a7e0540 Mon Sep 17 00:00:00 2001
From: Kegan Dougal <7190048+kegsay@users.noreply.github.com>
Date: Wed, 13 Aug 2025 13:33:38 +0100
Subject: [PATCH 1/4] Ensure the create event is cached prior to sorting

---
 stateresolutionv2.go | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/stateresolutionv2.go b/stateresolutionv2.go
index 770d9282..10c7bc6c 100644
--- a/stateresolutionv2.go
+++ b/stateresolutionv2.go
@@ -391,17 +391,26 @@ func ResolveStateConflictsV2New(
 // using Kahn's algorithm in order to topologically order them. The
 // result array of events will be sorted so that "earlier" events appear
 // first.
+// FIXME: this function does not sort correctly because it doesn't lookup PL events
+// correctly, meaning it will sort incorrectly for PL tiebreaks.
 func ReverseTopologicalOrdering(input []PDU, order TopologicalOrder) []PDU {
-	r := stateResolverV2{}
+	r := stateResolverV2{
+		resolvedCreate: getCreateEvent(input),
+	}
 	return r.reverseTopologicalOrdering(input, order)
 }
 
+// TODO: Remove this function. Use ReverseTopologicalOrdering.
 // HeaderedReverseTopologicalOrdering takes a set of input events and sorts
 // them using Kahn's algorithm in order to topologically order them. The
 // result array of events will be sorted so that "earlier" events appear
 // first.
+// FIXME: this function does not sort correctly because it doesn't lookup PL events
+// correctly, meaning it will sort incorrectly for PL tiebreaks.
 func HeaderedReverseTopologicalOrdering(events []PDU, order TopologicalOrder) []PDU {
-	r := stateResolverV2{}
+	r := stateResolverV2{
+		resolvedCreate: getCreateEvent(events),
+	}
 	input := make([]PDU, len(events))
 	for i := range events {
 		unwrapped := events[i]
@@ -414,6 +423,15 @@ func HeaderedReverseTopologicalOrdering(events []PDU, order TopologicalOrder) []
 	return result
 }
 
+func getCreateEvent(input []PDU) PDU {
+	for _, ev := range input {
+		if ev.Type() == spec.MRoomCreate && ev.StateKeyEquals("") {
+			return ev
+		}
+	}
+	return nil
+}
+
 // isControlEvent returns true if the event meets the criteria for being classed
 // as a "control" event for reverse topological sorting. If not then the event
 // will be mainline sorted.

From 3c641bb19714c015e99c5cdaf794ff98cea782d5 Mon Sep 17 00:00:00 2001
From: Kegan Dougal <7190048+kegsay@users.noreply.github.com>
Date: Wed, 13 Aug 2025 14:11:15 +0100
Subject: [PATCH 2/4] Fix invites in v12 rooms

They would previously include the create event because `stateNeeded`
returns the state needed for auth purposes, not for setting `auth_events`.
---
 performinvite.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/performinvite.go b/performinvite.go
index 69ea5152..5bc7e2ae 100644
--- a/performinvite.go
+++ b/performinvite.go
@@ -112,6 +112,9 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 	if len(stateNeeded.Tuples()) == 0 {
 		return nil, spec.InternalServerError{}
 	}
+	if stateNeeded.Create && verImpl.DomainlessRoomIDs() {
+		stateNeeded.Create = false
+	}
 
 	latestEvents, err := input.EventQuerier(ctx, input.RoomID, stateNeeded.Tuples())
 	if err != nil {

From 908a63a3eeeae3fa791e81dd76ed4d7a189a0d8e Mon Sep 17 00:00:00 2001
From: Kegan Dougal <7190048+kegsay@users.noreply.github.com>
Date: Wed, 13 Aug 2025 15:43:41 +0100
Subject: [PATCH 3/4] Debug logging

---
 performinvite.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/performinvite.go b/performinvite.go
index 5bc7e2ae..1dd8cf1b 100644
--- a/performinvite.go
+++ b/performinvite.go
@@ -115,6 +115,7 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 	if stateNeeded.Create && verImpl.DomainlessRoomIDs() {
 		stateNeeded.Create = false
 	}
+	fmt.Println("debug-invite:: stateNeeded.Create=", stateNeeded.Create, "domainless=", verImpl.DomainlessRoomIDs())
 
 	latestEvents, err := input.EventQuerier(ctx, input.RoomID, stateNeeded.Tuples())
 	if err != nil {
@@ -155,6 +156,8 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 			)
 			return spec.Forbidden(err.Error())
 		}
+		c, e := authEventProvider.Create()
+		fmt.Println("debug-invite:: checkEventAllowed authEventProvider create=", c, "err=", e)
 
 		// Check if the event is allowed.
 		if err = Allowed(inviteEvent, authEventProvider, input.UserIDQuerier); err != nil {

From 06887dd976e0d11003b6c728c5f2f206a9f9655f Mon Sep 17 00:00:00 2001
From: Kegan Dougal <7190048+kegsay@users.noreply.github.com>
Date: Wed, 13 Aug 2025 15:59:41 +0100
Subject: [PATCH 4/4] Revert "Debug logging"

This reverts commit 908a63a3eeeae3fa791e81dd76ed4d7a189a0d8e.
---
 performinvite.go | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/performinvite.go b/performinvite.go
index 1dd8cf1b..5bc7e2ae 100644
--- a/performinvite.go
+++ b/performinvite.go
@@ -115,7 +115,6 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 	if stateNeeded.Create && verImpl.DomainlessRoomIDs() {
 		stateNeeded.Create = false
 	}
-	fmt.Println("debug-invite:: stateNeeded.Create=", stateNeeded.Create, "domainless=", verImpl.DomainlessRoomIDs())
 
 	latestEvents, err := input.EventQuerier(ctx, input.RoomID, stateNeeded.Tuples())
 	if err != nil {
@@ -156,8 +155,6 @@ func PerformInvite(ctx context.Context, input PerformInviteInput, fedClient Fede
 			)
 			return spec.Forbidden(err.Error())
 		}
-		c, e := authEventProvider.Create()
-		fmt.Println("debug-invite:: checkEventAllowed authEventProvider create=", c, "err=", e)
 
 		// Check if the event is allowed.
 		if err = Allowed(inviteEvent, authEventProvider, input.UserIDQuerier); err != nil {