When using cdebootstrap from within buster/stable to create a rootfs for sid/unstable, it will fail with:
E: Internal error: download
Seems "64k ought to be enough for everyone" strikes again as this is functionally a dupe of Bug#554444 though it is now that a READSIZE of 65536 in libdebian-installer/src/parser_rfc822.c is now insufficient. I downloaded the deb-src, updated READSIZE to 262144, debuild'ed it and installed it, cdebootstrap would then complete successfully for sid/unstable. My diff is:
diff --git a/src/parser_rfc822.c b/src/parser_rfc822.c
index afd336a..b14859e 100644
--- a/src/parser_rfc822.c
+++ b/src/parser_rfc822.c
@@ -35,7 +35,7 @@
#include <sys/types.h>
#include <unistd.h>
-#define READSIZE 65536
+#define READSIZE 262144
int di_parser_rfc822_read (char *begin, size_t size, di_parser_info *info, di_parser_read_entry_new entry_new, di_parser_read_entry_finish entry_finish, void *user_data)
{