diff --git a/plugin/rules.ts b/plugin/rules.ts
index 1a69b44..ca00593 100644
--- a/plugin/rules.ts
+++ b/plugin/rules.ts
@@ -43,7 +43,10 @@ function stripTrailingMetadata(input: string): string {
 
 function getLastChar(input: string): string {
   const t = stripTrailingMetadata(input).trim();
-  return t.length ? t[t.length - 1] : "";
+  if (!t.length) return "";
+  // Use Array.from to handle multi-byte characters (emoji, surrogate pairs)
+  const chars = Array.from(t);
+  return chars[chars.length - 1] || "";
 }
 
 export function resolvePolicy(config: WhisperGateConfig, channelId?: string, channelPolicies?: Record<string, ChannelPolicy>) {