Issue 087: the controller cannot tell that a node's host is too old for what it sends

2026-09-22 19:43:01 +02:00
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 status: open
 opened: 2026-09-22
 located-in: []
 fixed-by:
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 # 087 — The controller cannot tell that a node's host is too old for what it sends
 ## What was observed
 Found in review of the adoption-mode build, 2026-09-22, by reading the code.
 A host parses a declaration strictly: a field it does not know makes it refuse the whole
 declaration, and nothing is applied. That is deliberate, and it is what keeps a half-understood
 declaration off a machine. It also means every new field in a declaration is a flag day: hosts
 must be upgraded before the controller sends it.
 The controller has no record of which version of the host a node runs. It is not in what a node
 reports, and it is not in the node's profile. So when a node refuses a declaration for that
 reason, the mesh shows the node failing and relays the host's refusal. Nothing says *the host on
 this machine is older than what the mesh now sends*, and nothing could have said so beforehand.
 Adoption mode adds four such fields, one of them on the declaration of **every** node, and its
 merge order exists for this reason alone: the host merges first, every machine is upgraded, then
 the controller.
 ## Why it matters beyond this instance
 Every future field in a declaration has the same flag day, and the mesh upgrades itself. A mesh
 that cannot say which machines are ready for what it is about to send has to be upgraded by
 someone remembering the order. The rule that a host refuses what it does not understand is right;
 the missing half is that the controller should know before it sends.
 ## Open questions
 - Should a node report the version of its host, so the controller can refuse to send a
  declaration a node cannot parse, and say which machines are behind?
 - Should the mesh refuse to send a field no node understands yet, or refuse per node and say so?
 - Is there a general shape here — a declaration saying which version of the host it needs — or is
  a reported version enough?