# UNDF: UNDF-2026-000000991
--- a/sv_main.c
+++ b/sv_main.c
@@ -1468,12 +1468,21 @@ SV_SoundIndex

 ================
 */
+// Hash lookup for SV_SoundIndex: avoids O(S) linear scan on every sound reference.
+#define SV_SOUND_PRECACHE_HASHSIZE 512
+static int sv_sound_precache_hashtable[SV_SOUND_PRECACHE_HASHSIZE];
+static int sv_sound_precache_hashnext[MAX_SOUNDS];
+
+static unsigned SV_SoundPrecacheHash(const char *s)
+{
+	unsigned hash = 0;
+	for (; *s; s++)
+		hash = hash * 31 + (unsigned char)*s;
+	return hash % SV_SOUND_PRECACHE_HASHSIZE;
+}
+
 int SV_SoundIndex(const char *s, int precachemode)
 {
-	int i, limit = ((sv.protocol == PROTOCOL_QUAKE || sv.protocol == PROTOCOL_QUAKEDP || sv.protocol == PROTOCOL_NEHAHRAMOVIE || sv.protocol == PROTOCOL_NEHAHRABJP) ? 256 : MAX_SOUNDS);
+	int i, limit = ((sv.protocol == PROTOCOL_QUAKE || sv.protocol == PROTOCOL_QUAKEDP || sv.protocol == PROTOCOL_NEHAHRAMOVIE || sv.protocol == PROTOCOL_NEHAHRABJP) ? 256 : MAX_SOUNDS);
 	char filename[MAX_QPATH];
 	if (!s || !*s)
 		return 0;
@@ -1481,7 +1490,12 @@ int SV_SoundIndex(const char *s, int precachemode)
 	//	return 0;
 	dp_strlcpy(filename, s, sizeof(filename));
-	for (i = 1;i < limit;i++)
+	// Hash lookup: O(1) average instead of O(S) linear scan.
+	unsigned h = SV_SoundPrecacheHash(filename);
+	for (i = sv_sound_precache_hashtable[h]; i >= 0; i = sv_sound_precache_hashnext[i])
+		if (!strcmp(sv.sound_precache[i], filename))
+			return i;
+	// Not found: scan for empty slot to insert (precache mode)
+	for (i = 1;i < limit;i++)
 	{
 		if (!sv.sound_precache[i][0])
 		{
@@ -1503,8 +1517,11 @@ int SV_SoundIndex(const char *s, int precachemode)
 				MSG_WriteString(&sv.reliable_datagram, filename);
 			}
+			// Insert into hash table
+			sv_sound_precache_hashnext[i] = sv_sound_precache_hashtable[h];
+			sv_sound_precache_hashtable[h] = i;
 			return i;
 		}
-		if (!strcmp(sv.sound_precache[i], filename))
-			return i;
 	}
 	Con_Printf("SV_SoundIndex(\"%s\"): i (%i) == MAX_SOUNDS (%i)\n", filename, i, MAX_SOUNDS);