diff --git a/src/core/hooks/auto-recall.ts b/src/core/hooks/auto-recall.ts
index e5760f0..036c1cd 100644
--- a/src/core/hooks/auto-recall.ts
+++ b/src/core/hooks/auto-recall.ts
@@ -776,11 +776,15 @@ function normalizeBudgetLimit(value: number | undefined): number | undefined {
 }
 
 function truncateRecallLine(line: string, maxChars: number): string {
-  if (line.length <= maxChars) return line;
+  // Count and slice by code point, not UTF-16 code unit, so a cut never lands
+  // between the halves of a surrogate pair (which would corrupt a non-BMP
+  // character to U+FFFD when the line is UTF-8 encoded for the request).
+  const cps = Array.from(line);
+  if (cps.length <= maxChars) return line;
   if (maxChars <= RECALL_TRUNCATION_SUFFIX.length) {
-    return line.slice(0, maxChars);
+    return cps.slice(0, maxChars).join("");
   }
-  return `${line.slice(0, maxChars - RECALL_TRUNCATION_SUFFIX.length).trimEnd()}${RECALL_TRUNCATION_SUFFIX}`;
+  return `${cps.slice(0, maxChars - RECALL_TRUNCATION_SUFFIX.length).join("").trimEnd()}${RECALL_TRUNCATION_SUFFIX}`;
 }
 
 /**