UM/MOD is assembled exactly as DECOMPOSITION.md section 4 gives it and needs no change: it is exact for every uhi < ud at 32- and 64-bit cells. It is checked against q*d + r = uhi:ulo with r < d through v4_umul, so no second C divider has to be trusted. Coverage: all edge-vector triples with uhi < ud plus 20000 pseudo-random cases (top-bit, small and near-maximum divisors), optimised and under ASan+UBSan. Two hand mutations each fail more than 15000 checks. New headroom probe: runs a word with marked cells under the canary and under its return address and reports how many survive, since the D-2 circular stacks overwrite silently instead of faulting. Measured: UM* 6 data cells under its args, 4 return entries under its return UM/MOD 3 data cells under its args, 3 return entries under its return DECOMPOSITION.md: UM/MOD marked executed, with its defined range and stack limits. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
v4/
StarForth v4: the 32-instruction F18-derived core. The design lives in
docs/v4.0.0/JUSTIFICATION.md (why) and docs/v4.0.0/DECOMPOSITION.md
(every v3 word mapped to a v4 fate).
The first deliverable is the hosted C99 golden model (JUSTIFICATION.md §10,
step 1). It must pass POST and hold K≡1.0 with 32- and 64-bit cells on all
three host ISAs.
What exists so far is the single node: registers, circular stacks, memory, all
32 opcodes, and per-opcode and per-call-target heat. make -C v4 test builds
and runs the tests at both cell widths; make -C v4 sanitize repeats them
under ASan and UBSan. There is no compiler capsule, no POST and no K
measurement yet.