--- a/libarchive/archive_string.c
+++ b/libarchive/archive_string.c
@@ -1551,10 +1551,10 @@ my_atoi(const char *p)
 }
 
 /*
- * Return ANSI Code Page of current locale set by setlocale().
+ * Return ANSI Code Page of current locale set by setlocale() (uncached).
  */
 static unsigned
-get_current_codepage(void)
+get_current_codepage_uncached(void)
 {
 	char *locale, *p;
 	unsigned cp;
@@ -1574,6 +1574,28 @@ get_current_codepage(void)
 	return (cp);
 }
 
+/*
+ * Bun: cache the codepage after the first call. The process never changes
+ * its locale at runtime, but `bun install` creates a charset converter per
+ * extracted archive on many worker threads at once, and hammering the UCRT's
+ * setlocale(LC_CTYPE, NULL) query from all of them concurrently is both
+ * wasted work and a needless trip through the CRT locale machinery (and its
+ * heap) on every archive. Compute once; later callers read the cached value.
+ */
+static unsigned
+get_current_codepage(void)
+{
+	static volatile LONG cached_cp = -1;
+	LONG cp = cached_cp;
+
+	if (cp == -1) {
+		cp = (LONG)get_current_codepage_uncached();
+		InterlockedCompareExchange(&cached_cp, cp, -1);
+		cp = cached_cp;
+	}
+	return ((unsigned)cp);
+}
+
 /*
  * Translation table between Locale Name and ACP/OEMCP.
  */
@@ -1626,10 +1648,10 @@ static struct {
 };
 
 /*
- * Return OEM Code Page of current locale set by setlocale().
+ * Return OEM Code Page of current locale set by setlocale() (uncached).
  */
 static unsigned
-get_current_oemcp(void)
+get_current_oemcp_uncached(void)
 {
 	int i;
 	char *locale, *p;
@@ -1652,6 +1674,23 @@ get_current_oemcp(void)
 	}
 	return (GetOEMCP());
 }
+
+/*
+ * Bun: cached for the same reason as get_current_codepage() above.
+ */
+static unsigned
+get_current_oemcp(void)
+{
+	static volatile LONG cached_ocp = -1;
+	LONG ocp = cached_ocp;
+
+	if (ocp == -1) {
+		ocp = (LONG)get_current_oemcp_uncached();
+		InterlockedCompareExchange(&cached_ocp, ocp, -1);
+		ocp = cached_ocp;
+	}
+	return ((unsigned)ocp);
+}
 #else
 
 /*