LithosAnanake/v4/README.md

# 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` into `capsules/v4/nucleus-64.f18` | The assembled words, as a capsule of F18 code: sent through its port to a node born empty |
| 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, after `ENGINE.md` step 1: all six builds start the nucleus,
load `v4:forth79.4th`, pass POST and reach `ok>`, with the same lines:

```
PARITY:V4_NUCLEUS name=v4:nucleus-64.f18 capsule_id=... capsule_hash=0x97a655081b2af559 words=298
PARITY:V4_CAPSULE name=v4:forth79.4th capsule_id=... dict_hash=...
PARITY:V4_POST tests=538 pass=538 fail=0
PARITY:V4_SYSTEM word_count=314 dict_hash=...
PARITY:OK
POST: PASSED
ok>
```

Bare-metal logs: `logs/20261006-110551/amd64/`, `logs/20261006-111621/aarch64/`,
`logs/20261006-111341/riscv64/`. On each, seven lines were then typed at the
prompt through the serial port — a definition, its use with the capsule's
`U*`, `COLD`, the capsule word again, a `FORGET` of it (refused), a kernel
word no one serves, and `BYE` — and each was answered as the hosted binary
answers it. The
capsules were unsigned (no signing key on this machine).

**A node is sent text as a message** (`docs/v4.0.0/MESH.md` section 6). It
does not read its own command line, prints no prompt and has no console of
its own. With nothing to do it is blocked reading its ports. A neighbour
writes it a message; text for it is interpreted; what it prints goes back
as messages to the sender, and then a message saying how the text ended.
Its console says ` ok` or ` ERROR` and prompts, as the kernel's REPL does
for a v3 VM. A message carries 1024 characters, a block. `v4/src/message.c`
is the format for a host; `v4_boot_line` (`v4/system/boot.c`) is the
console both products and the capsule loader use.

**A node asks its kernel by writing to its port** (`ENGINE.md` 3.3). The
write blocks the node until it has been served. A kernel word is a
dictionary entry made by `n KERNEL-WORD name`, whose body writes `n` to the
port; its arguments and results are on the data stack. `BYE` is the one
kernel word so far. A node can be stopped between any two instruction
words and is blocked while it waits at its port, which is what a system of
many users and tasks, preemptive and cooperative, needs of it
(`ENGINE.md` 3a).

**The two products have parted** (`ENGINE.md` 3c). They share the engine,
the FORTH-79 capsule and its POST; their nuclei may differ. The hosted
product is its own and may become a hosted SDK. The bare-metal product is
to be LithosAnanke with the node in the StarForth VM's place, and
everything about word records, the fleet and identity is its alone.

**Nodes that talk** (`docs/v4.0.0/MESH.md`) are the next step, ahead of
making v4 equal v3 on bare metal. Its first part is built and tested in
the engine: a node has `V4_PORTS` ports; a read from one blocks until the
neighbour writes and a write until the neighbour reads; a node is born
empty with `P` at its ports and executes what a neighbour sends it, which
is how each product's node now gets its nucleus, as a capsule; and
the fabric (`v4/src/fabric.c`) is the nodes there are and the table of how
their ports are wired, both of which change while they run. The products
below are still one node each; they become the five nodes at `MESH.md`
steps 8 and 9.

**Finding the way** (`MESH.md` step 4) is built: a node has a table of
which port leads toward which node (`ROUTE`, `DEFAULT-ROUTE`, `NO-ROUTES`),
passes on a message that is not for it, and `SEND`s text to another node;
`v4/tests/test_host_mesh.c` runs three StarForth nodes in a row. A node
looks before it begins a message (`MESH.md` section 7a): it takes in what
its neighbours are waiting to write to it, keeps those messages until it
has nothing else to do, and writes only to a neighbour that is waiting to
read -- or, of two neighbours, the one with the lower number may wait.
`NEIGHBOUR ( node port -- )` tells a node who is on each port. A node with
no room for one more message lets it go and counts it in `(LOST)`.

**Five nodes from nothing** (`MESH.md` step 5) is built and proven in the
fabric under test: Hera asks whoever holds the fabric for a node
(`v4/src/manage.c`: `NODE-BORN`, `NODE-WIRE` and the rest), sends it the
nucleus through the port that joins them, then FORTH-79 a line at a
time, and joins four such nodes in a square round her
(`capsules/v4/hera.4th`: `BIRTH`, `UNIT`). `v4/tests/test_host_unit.c`.
The two products are not yet this: they become the five nodes at steps 8
and 9.
A node she births is not POSTed: POST is the kernel's, once, on Hera.

**Refusals and waits** (`MESH.md` 7b, step 6c). A node is never left
waiting on a node that is gone, and a wait on a node that is alive and
stuck is ended by Hera's killing it, or from the console. A node with no
room for a message, or no way to pass it on, or that would be the
sixteenth to pass it on, sends a NACK to whoever waits on it; `(REFUSED)`
counts them. `AWAIT` ends in an error if the answer is not going to come:
"Message refused", "Node gone", or "Interrupted" when a line is typed at
the console. `n KILL` on Hera removes node n and tells every other node it
is gone; a node believes that only from its centre. A stuck node can hold
up its neighbours until it is killed: `MESH.md` 7b.7 says how.

**Blocks** (`MESH.md` step 6). The block words are the kernel's, as they
are for a v3 VM: `BLOCK`, `BUFFER`, `UPDATE`, `SAVE-BUFFERS` and
`EMPTY-BUFFERS` each write one request to port 0, by block number only
(`v4/include/v4/blocks.h`). The node has a window of four slots in its
memory; the kernel copies blocks into it, keeps the record of what is in
it, and decides when a block is written (`v4/system/blocks.c`). The blocks
are the kernel's block subsystem's, which is v3's
(`v3/src/block_subsystem.c`):
one chain, the same blocks at the same numbers for every node. A hosted
program has the chain's fast RAM, blocks 1 to 2047. On bare metal the chain
is fast RAM, the ramdrive and the virtio disk; the disk is read and not yet
written, because nothing in v4 gives its owner's word that it may be
formatted. Who may have which block is not checked yet.

**This is still the lone node.** On bare metal `kernel_main.c` starts it
before the fleet tables, beside the kernel's own system and not in the VM's
place. `ENGINE.md` sets out the steps from here; step 1 is done and step 2 is
part done. `V3-PARITY.md` records the rulings it is built from.

**What this does not yet show.** `forth79.4th` holds two definitions, `U*`
and `U/MOD`. Every other word is still in the assembled nucleus, so POST is
so far a test of the assembled words. Moving them to the capsule, a group at
a time with POST after each, is the next step (`NUCLEUS.md` section 8).

## POST

POST is the kernel's, as in v3 (`MESH.md` step 6b, `NUCLEUS.md` 6.3). The
kernel holds the cases, `v4/system/post_cases.c`: 538 of them, covering 126
of the 130 words of the FORTH-79 Required Word Set. 431 are v3's cases with
what the hosted v3 binary did as the expected result; every other case,
and the v3 cases left out, are listed with reasons in
`docs/v4.0.0/POST79.md`.

- `make -C v4 post` boots the amd64 system: the quick check after a change.
- `make -C v4 hosted-check` boots all three hosted ISAs and compares them.
- `make -C v4 post79` writes the cases again (`tools/mkpost.py`,
  `tools/post79_rules.py`); it needs the hosted v3 binary.

The runner, `v4/system/post.c`, feeds each case to the node a line at a
time, keeps what the node prints, reads its data stack from outside, and
judges: an error exactly if one is expected, and otherwise the stack and
every character printed. Nothing of POST is in the node's dictionary, and
POST leaves nothing: the system is sealed before it, and afterwards the
kernel puts the node back to the system as sealed, as v3 puts the
dictionary back after each of its suites. The boot then prints
`PARITY:V4_SYSTEM word_count=N dict_hash=0x...`, and passes only if no
case failed (`v4/system/boot.c`). A case the node does not come back from
ends POST there, named. `make -C v4 hosted-check` also boots a program
whose POST has failing cases and requires that the boot fails.

Not tested: `KEY`, `EXPECT`, `QUERY` (the keyboard) and `QUIT` (it returns
without ` ok`).

Open: `PAD 42 OVER !` faults on v4, because `PAD` is a byte address and `!`
takes a cell address (D-1). FORTH-79 expects it to work. The v3 case for it
is left out until that is ruled.

The Required Word Set list in `tools/mkpost.py` was written from memory of
the standard and has not been checked against the document.