diff --git a/eventversion.go b/eventversion.go
index 9f38585d..596458e2 100644
--- a/eventversion.go
+++ b/eventversion.go
@@ -39,6 +39,14 @@ type IRoomVersion interface {
 	DomainlessRoomIDs() bool
 	PrivilegedCreators() bool
 	StateDAGs() bool
+	// returns true if this room version requires a "creator" field
+	// in the m.room.create event content (room versions 1–10). The field
+	// was removed in room version 11, where the creator is instead derived from
+	// the event sender.
+	CreatorInCreateEvent() bool
+	// StrictEventByteLimits returns true if this room version enforces field
+	// length limits in bytes rather than Unicode codepoints (introduced in v11 for synapse).
+	StrictEventByteLimits() bool
 }
 
 type KnownRoomVersionFunc func(RoomVersion) bool
@@ -110,6 +118,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV1,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV1,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV1,
@@ -130,6 +139,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV1,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV1,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV1,
@@ -150,6 +160,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -170,6 +181,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -190,6 +202,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -210,6 +223,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               disallowKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -230,6 +244,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -250,6 +265,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         allowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -270,6 +286,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         allowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -290,6 +307,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         allowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -310,6 +328,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         allowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV2,
+		strictEventByteLimits:                  true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -330,6 +349,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:       checkKnocking,
 		checkRestrictedJoinAllowedFunc: allowRestrictedJoins,
 		checkCreateEvent:               checkCreateEventV3,
+		strictEventByteLimits:          true,
 		// v3 versions relax the room ID check as the room ID has no domain now.
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV3,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV3,
@@ -353,6 +373,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         allowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -373,6 +394,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkRestrictedJoinAllowedFunc:         disallowRestrictedJoins,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -392,6 +414,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		parsePowerLevelsFunc:                   parsePowerLevels,
 		checkKnockingAllowedFunc:               checkKnocking,
 		checkCreateEvent:                       checkCreateEventV1,
+		creatorInCreateEvent:                   true,
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV2,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV2,
 		newEventFromTrustedJSONWithEventIDFunc: newEventFromTrustedJSONWithEventIDV2,
@@ -436,6 +459,7 @@ var roomVersionMeta = map[RoomVersion]IRoomVersion{
 		checkKnockingAllowedFunc:       checkKnocking,
 		checkRestrictedJoinAllowedFunc: allowRestrictedJoins,
 		checkCreateEvent:               checkCreateEventV3,
+		strictEventByteLimits:          true,
 		// v3 versions relax the room ID check as the room ID has no domain now.
 		newEventFromUntrustedJSONFunc:          newEventFromUntrustedJSONV3,
 		newEventFromTrustedJSONFunc:            newEventFromTrustedJSONV3,
@@ -529,6 +553,13 @@ type RoomVersionImpl struct {
 	domainlessRoomID bool
 	// creators have infinite PL
 	privilegedCreators bool
+	// the m.room.create content includes a "creator" field
+	// (room versions 1–10). This is distinct from privilegedCreators, which
+	// governs power-levels; this flag only controls whether the field
+	// must be present in the create event content.
+	creatorInCreateEvent bool
+	// field length limits are in bytes rather than Unicode codepoints
+	strictEventByteLimits bool
 	// Events form two graphs, a state DAG and an event DAG.
 	stateDAGs                      bool
 	checkRestrictedJoin            func(ctx context.Context, localServerName spec.ServerName, roomQuerier RestrictedRoomJoinQuerier, roomID spec.RoomID, senderID spec.SenderID, privilegedCreators bool) (string, error)
@@ -562,6 +593,14 @@ func (v RoomVersionImpl) PrivilegedCreators() bool {
 	return v.privilegedCreators
 }
 
+func (v RoomVersionImpl) CreatorInCreateEvent() bool {
+	return v.creatorInCreateEvent
+}
+
+func (v RoomVersionImpl) StrictEventByteLimits() bool {
+	return v.strictEventByteLimits
+}
+
 // StateResAlgorithm returns the state resolution for the given room version.
 func (v RoomVersionImpl) StateResAlgorithm() StateResAlgorithm {
 	return v.stateResAlgorithm