# Compatibility follow-up: 0.26.0-10232026

Tested source commit: `62bfebf`.
Kernel SHA-256: `76bc80d0d674bb4c0826f4b4ac1b7d88d80bace9ba3098006e4c8ab6d0a84aae`.
Environment: QEMU i386, CPU 486, 64 MiB RAM, serial console. Existing
FAT16 application images from the 2026-10-23 DOS compatibility batches were
copied for each run. Tests ran through `dosrun` in ManiOS.

## Results

- Costa GUI 1.8.0: the former port `21h` fault is passed. `DESKTOP.EXE` then
  prints `Illegal function call in line 0 of module COSTALIB at address
  15CA:2E00` and returns to the shell. No usable desktop was reached.
- DATES 2002.08: the former port `21h` fault is passed. Startup then faults on
  opcode `FF` at `0A34:5CD8`; no date list or usage screen was reached.
- Cash Register 7.1j: the former PIC and PIT channel-0 port faults are passed.
  It renders part of its text UI, then faults on unsupported `ARPL` at
  `6DCC:0293`; no register operation was completed.
- Life2: the former PIT channel-0 port fault is passed. The program enters RUN
  mode and stays active, but the bounded observation did not confirm an
  evolving generation. Its status remains Partial.

The DOS regression suite also covers the master PIC mask at port `21h` and
PIT channel 0 modes 0, 2 and 3, count latching and byte-pair reloads. Full
protected-mode/DPMI, x87, general hardware IRQ delivery and arbitrary port I/O
remain outside this compatibility update.
