D101 - Guest memory is a separate binding

Status: decided Date: 2026-09-26

A translated module binds guest memory separately from the observation window its registers are copied into. A guest access outside the memory window reads zero and drops writes, checked per word by address.

Why: in one shared buffer a guest store could reach the observation window, and a memory fault would present as a register fault in an unrelated instruction. Out-of-range storage-buffer access is undefined, and wrapping an overrun onto word zero turns an ordinary guest bug into a plausible corruption of the start of memory.

Rejected:

• One buffer with memory at an offset: guest stores can reach the registers.
• Masking or wrapping the index: an overrun lands somewhere the guest never asked for.