# Xo 0.13 release notes


## Introduction

Xo 0.13 deletes the last third party C: TLS is written only in Xo. The
runtime's C went from about 5,800 lines to about 2,660.

## Runtime

- Mbed TLS and fiat-crypto are deleted (206,879 lines of third party C).
- The Windows event loop, main's threads, the network, clock, scope and
  fault entries, the x86-64 unwinder, the allocator's entries, and the
  handle code are Xo.
- The backends call the Xo runtime directly for faults, string compare,
  number formatting, network, clock, scope, cancellation, and real-time
  entries.
- A fault in a native server's connection ends only that connection.
- Sanitizer builds map the heap through libc, so ASan and TSan see it.