[michaelm-afk]

Original emulated SDK pad packets add about one original update of avoidable
input delay. The default-off Low Input Latency mod uses the companion engine's
latest resolved digital sample at checked original reader boundaries. The full
original reader, edge/action locks and rumble paths still execute. Simulation
remains at the original PAL/NTSC rate; no rendering or interpolation is added.

Regional bindings

• USA: checked return 0x80028EEC for the original P1 caller.
• EU1 and EU2 Rev 1: checked return 0x800263B4; all original language relocations.
• EU2 original revision: checked return 0x80026368; all five languages.
• Japan: checked cached-P1 store 0x800207C8 and both original callers; retain the
  original combined P1/P2 BIOS producer. Convert its legacy byte-swapped button
  layout to canonical host bits for priming and back at the original guest store.
  Japan gameplay acceptance remains open.
  Whole reader/outer-function contracts and device guards retain original input
  on mismatch. Addresses/contracts come from owner-supplied original discs; no
  retail bytes or outside decompilation code are distributed.

Validation and actual limits

• 17 owner-extracted regional/language/revision EXEs pass the static/CPU-state
  fixture. Both Japanese callers are explicitly exercised by the fixture.
• English EU1: actual OFF/ON host-sample-to-read medians 34.35 / 14.16 ms;
  first presented avatar response 93.01 / 73.02 ms, 6 pulses per case. Original
  50 Hz simulation/presentation. The owner has twice confirmed a clearly more
  responsive personal build, most recently on 28 October 2026.
• USA: regular LOAD outside the Hundred Year Old Man's hut, 4 direction pulses
  and a jump/landing pass. Median sample-to-read 11.52 ms versus 27.97 ms at the
  original SDK shadow observation; median paired gain 16.45 ms.
• EU2 original English: regular LOAD in Village of All Beginnings, same short
  movement/jump check passes. Medians 13.66 / 33.50 ms; paired gain 19.94 ms.
• USA/EU2 shadow values are observed in the same ON run, not separate OFF gameplay
  measurements. Each has 4 press/release direction edges and one jump/release,
  no extra/lost observed edges. This is internal software timing, not controller-TV.
• Japan: a bounded follow-up identified a concrete legacy-layout mismatch:
  original left=0x8000 / host left=0x0080, original cross=0x0040 / host cross=0x4000.
  This necessary title-boundary correction is covered for all button bits, both
  callers and canonical priming/fallback. The original LOAD menu lists the hut
  save, but the follow-up still did not establish controllable gameplay. No Japan
  gameplay pass or latency number is claimed; guarded optional source is retained.
• Other European languages and EU2 Rev 1 are statically covered, not newly played.
• No full campaign, new area-transition/save roundtrip, physical hotplug/rumble,
  analog or multiplayer gameplay acceptance. Recognized unsupported controller
  routes fall back; unregistered guest-only controller patches are not validated.

All games used verified disposable card copies with two independent backups;
original cards and old releases were unchanged. RA/100-Hz experiments, credentials,
private configuration, ROMs, cards and native binaries are excluded from this PR.

Integration
Requires RetroPortingToolKit/psxrecomp#780 (the separate psxrecomp snapshot API); merge that engine PR first. Base is TombaRecomp master cf6171b,
remotely rechecked 28 October 2026. Rebuild the runtimes and native overlays with
the added mod_instruction_sites; never reuse/rename a stale native-cache namespace.
Runtime measurements used the existing isolated personal engine backport; the
public adapter fixture was compiled against the public companion engine headers.
A new complete public-master release build is not claimed by this validation.

The confirmed US/EU paths are unchanged. Japan received only the necessary
legacy-button encoding correction; the shared engine API is unchanged. No further
small, proven safe optimization was found: earlier polling or presentation changes
need separate correctness work. Keep the feature default-off and the remaining
Japan/runtime limits explicit during review.