# 087 — resolved: the mesh knows which host runs a machine

*2026-09-30.*

## The field existed and was thrown away on arrival

The machine has reported its host version since
[ADR 0141](../../02-DECISIONS/0141-the-host-delivers-its-own-successor.md) — `Host` on the report, with
a comment saying why it must be there: *"without it nothing can say a machine is behind."*

**The controller's own copy of the report did not have the field.** Two structs describe one message,
one on each side of the wire, and only the sending side had it — so it unmarshalled into nothing and the
mesh could not answer a question the machine had been answering for a week. That is the whole of this
issue's mechanism, and it is worth stating plainly because neither side was wrong on its own.

## What it says now

`node show` names it per machine:

```
  last heard from   here
  host              2026-09-30-0214
```

`not reported — this machine has not said since the mesh began keeping it` where the mesh has not been
told, because a machine that has not said is a different thing from a machine running nothing.

`status` names the machines that are behind another:

```
1 machine(s) run an older host than another machine does:
  ace          2026-09-29-0113

  the newest any machine reports is 2026-09-30-0214. A host refuses a declaration carrying a
  field it does not know, whole — so a new field reaches these machines last
```

## Disagreement, not staleness, and that is deliberate

The open questions asked whether the controller should refuse to send a declaration a node cannot
parse. It cannot yet, honestly: **nothing delivers a host version** (ADR 0141 is accepted and not
built, which is [issue 142](../142-the-host-is-the-one-thing-the-mesh-does-not-deliver/00-report.md)),
so the mesh holds no canonical current version and "behind" has no fixed point to be behind.

What it can say truthfully is that these machines do not all run the same host, and which is newest of
the ones it has been told about. That is the fact that matters before a declaration gains a field: **the
oldest host in the mesh is what the mesh may send.**

Two deliberate refusals to guess:

- **A machine that has reported nothing is not called behind.** It may be running anything. `node show`
  says it has not said, per machine, which is the honest form.
- **Versions compare as strings.** That suits the timestamps and commits this mesh uses and is wrong
  for a scheme where `10` sorts before `9`. Said in the code at the place that would have to learn,
  rather than left as a surprise.

## The open questions, answered as far as they can be

- *Should a node report the version of its host?* It already did. The gap was the reading.
- *Should the mesh refuse to send a field no node understands yet, or refuse per node and say so?*
  Neither, yet — refusing needs the mesh to know which fields need which version, which is the third
  question below and is not answered here. What it does is make the disagreement visible before
  somebody adds a field.
- *Is there a general shape — a declaration saying which version of the host it needs?* Still open, and
  now cheaper to answer: the versions are recorded, so a minimum-version field on a declaration has
  something to compare against. It belongs with
  [issue 107](../107-a-declaration-carries-no-order/00-report.md), which wants to add a field and is the
  first thing this makes safe.