# 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.

Acceptance (`JUSTIFICATION.md` §16): v4 must be equivalent to v3 at any point
in time, with the same vocabularies and behaviour, on the F18-derived engine;
and every ISA, hosted and bare metal, must still reach its `ok` prompt.
`make -C v4 test` passing is a development check, not acceptance.

What exists so far is the single node: registers, circular stacks, memory, all
32 opcodes, per-opcode and per-call-target heat, and three console
registers (`CONSOLE-TX`, which captures output, and `CONSOLE-RX` and `CONSOLE-STATUS`, which hand out
input a test feeds) standing in for the console node until the mesh exists. The tests load definitions
onto a node either opcode by opcode (`v4/include/v4/asm.h`) or as text in the notation `DECOMPOSITION.md`
uses (`v4/include/v4/text.h`). `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 POST and no K measurement yet.

## The system: nucleus, capsules, prompt

`docs/v4.0.0/NUCLEUS.md` is the design. A v4 system is four things:

| Part | Where | What it is |
|---|---|---|
| Engine | `v4/src` | The golden model of the 32-opcode node |
| Nucleus | `v4/capsule/*.v4`, built by `v4/tools/mkimage.c` | The assembled words, as a memory image linked into the binary |
| Capsules | `capsules/v4/*.4th`, baked by `tools/mkcapsule.c` | FORTH source, loaded when the system comes up |
| Boot | `v4/system/boot.c` | Starts the nucleus, checks and loads each capsule, prints the parity lines, gives the prompt |

Two products link the same four and differ only in the console:

- **Hosted Linux**, `v4/tools/hosted.c`: `make -C v4 hosted` builds
  `v4/build/starforth4-amd64`, `-aarch64` and `-riscv64`, static, 64-bit cells.
- **Bare metal**, `kernel/src/v4/sk_v4.c`: `make -f kernel/Makefile ARCH=<arch> STARFORTH_V4=1`.

A boot prints:

```
PARITY:V4_NUCLEUS words=292 image_hash=0x...
PARITY:V4_CAPSULE name=v4:forth79.4th capsule_id=0x... capsule_hash=0x... dict_hash=0x...
PARITY:OK
ok>
```

Every build of one commit prints the same hashes. `make -C v4 hosted-check`
boots the three hosted binaries (the two foreign ones under user-mode QEMU)
and fails unless their output is identical and ends in `PARITY:OK`.

A capsule line the node does not answer ` ok` to ends the boot, naming the
capsule, block and line, with `PARITY:FAIL` and `POST: FAILED`.

State, 2026-10-05: capsule loading works on all six builds. The three hosted
binaries and the three bare-metal kernels (`clean qemu` with `STARFORTH_V4=1`)
print the same four lines and reach `ok>`:

```
PARITY:V4_NUCLEUS words=292 image_hash=0x60b74e4f87adb0ac
PARITY:V4_CAPSULE name=v4:forth79.4th capsule_id=0xa4b74bdc7deaf204 capsule_hash=0xa4b74bdc7deaf204 dict_hash=0x0baed67626b4fac4
PARITY:OK
ok>
```

Bare-metal logs: `logs/20261005-152955/amd64/`, `logs/20261005-154021/aarch64/`,
`logs/20261005-154150/riscv64/`. Each run was ended once the prompt was in the
log; nothing was typed at a bare-metal prompt, so keyboard input there is not
yet verified. The capsules were unsigned (no signing key on this machine).

`forth79.4th` holds no definitions yet: all 292 words are still in the
nucleus. There is no POST yet.