1 files changed, 33 insertions, 14 deletions

diff --git a/internal/admin/api_rooms.go b/internal/admin/api_rooms.go
index 16fc7a0..f9508f6 100644
--- a/internal/admin/api_rooms.go
+++ b/internal/admin/api_rooms.go
@@ -144,11 +144,38 @@ func (s *AdminServer) handleRooms(w http.ResponseWriter, r *http.Request) {
 
 		var extraFiles []ExtraFile
 
+		// Prepare the reciprocal exit in the destination map BEFORE the
+		// destination file is committed, so the written file is complete.
+		if linkFrom != nil && linkDir != nil && *linkDir != "" {
+			if dir := world.ExitDir(strings.ToLower(*linkDir)); dir != "" {
+				if opp, ok := world.OppositeExit[dir]; ok && !linkOneWay {
+					exits[string(opp)] = map[string]any{"room": *linkFrom}
+				}
+			}
+		}
+
+		// The destination room is committed FIRST: if it cannot be written,
+		// nothing else has been mutated yet. The old order wrote the
+		// source room's new exit first, so a failed destination write left
+		// a dangling exit pointing at a room that never existed, with no
+		// undo entry to repair it.
+		path := filepath.Join(subdir, strconv.Itoa(id)+".yaml")
+		newContent, writeErr := writeMapAsYAML(path, m)
+		if writeErr != nil {
+			failJSON(w, fmt.Sprintf("write room: %v", writeErr))
+			return
+		}
+
 		if linkFrom != nil && linkDir != nil && *linkDir != "" {
 			dir := world.ExitDir(strings.ToLower(*linkDir))
-			if opp, ok := world.OppositeExit[dir]; ok {
+			if _, ok := world.OppositeExit[dir]; ok {
 				srcRoom, loadErr := s.world.LoadRoom(*linkFrom)
 				if loadErr != nil {
+					// Roll back the destination so a failed create leaves
+					// no half-created room behind.
+					if rmErr := os.Remove(path); rmErr != nil {
+						log.Printf("room create rollback: remove %s: %v", path, rmErr)
+					}
 					failJSON(w, fmt.Sprintf("load link_from room %d: %v", *linkFrom, loadErr))
 					return
 				}
@@ -160,31 +187,23 @@ func (s *AdminServer) handleRooms(w http.ResponseWriter, r *http.Request) {
 				srcPath, srcOk := s.world.GetRoomPath(*linkFrom)
 				if srcOk {
 					oldContent, _ := snapshotFile(srcPath)
-					newContent, writeErr := writeYAMLFile(srcPath, srcRoom)
+					srcContent, writeErr := writeYAMLFile(srcPath, srcRoom)
 					if writeErr != nil {
+						if rmErr := os.Remove(path); rmErr != nil {
+							log.Printf("room create rollback: remove %s: %v", path, rmErr)
+						}
 						failJSON(w, fmt.Sprintf("write source room: %v", writeErr))
 						return
 					}
 					extraFiles = append(extraFiles, ExtraFile{
 						FilePath:   srcPath,
 						OldContent: oldContent,
-						NewContent: newContent,
+						NewContent: srcContent,
 					})
 				}
-
-				if !linkOneWay {
-					exits[string(opp)] = map[string]any{"room": *linkFrom}
-				}
 			}
 		}
 
-		path := filepath.Join(subdir, strconv.Itoa(id)+".yaml")
-		newContent, writeErr := writeMapAsYAML(path, m)
-		if writeErr != nil {
-			failJSON(w, fmt.Sprintf("write room: %v", writeErr))
-			return
-		}
-
 		s.world.AddRoomPath(id, path)
 		s.undoStack.Push(ChangeDesc{
 			Description: fmt.Sprintf("create room %d", id),