1 files changed, 17 insertions, 9 deletions
diff --git a/internal/game/cmd_dig.go b/internal/game/cmd_dig.go
index c58ba63..ff33490 100644
--- a/internal/game/cmd_dig.go
+++ b/internal/game/cmd_dig.go
@@ -127,7 +127,7 @@ func (g *Game) executeDig(sess *net.Session, args []string, rawInput string) {
 		return
 	}
 
-	newID, err := findNextRoomID(curPath)
+	newID, err := findNextRoomID(filepath.Dir(curPath), g.World.RoomIndex())
 	if err != nil {
 		sess.WriteLine("Error scanning room directory.")
 		return
@@ -222,14 +222,22 @@ func (g *Game) executeDig(sess *net.Session, args []string, rawInput string) {
 	g.checkAggro(sess)
 }
 
-func findNextRoomID(currentRoomPath string) (int, error) {
-	dir := filepath.Dir(currentRoomPath)
-	entries, err := os.ReadDir(dir)
+// findNextRoomID returns the first free room ID at or above localDir's
+// minimum, checked against every room ID in the world (globallyUsed). The
+// admin allocator (admin/id_alloc.go) does the same. A directory-scoped scan
+// could hand out an ID that already exists in another area, and
+// World.AddRoomPath would then silently shadow that room for the rest of the
+// process while leaving a duplicate file on disk.
+func findNextRoomID(localDir string, globallyUsed map[int]bool) (int, error) {
+	entries, err := os.ReadDir(localDir)
 	if err != nil {
 		return 0, err
 	}
 
-	used := make(map[int]bool)
+	used := make(map[int]bool, len(globallyUsed)+len(entries))
+	for id := range globallyUsed {
+		used[id] = true
+	}
 	minID := 0
 	first := true
 	for _, entry := range entries {
@@ -248,11 +256,11 @@ func findNextRoomID(currentRoomPath string) (int, error) {
 		}
 	}
 
-	if first {
-		return 1, nil
+	start := 1
+	if !first {
+		start = minID
 	}
-
-	for id := minID; ; id++ {
+	for id := start; ; id++ {
 		if !used[id] {
 			return id, nil
 		}