docs: the stale-Good quality contract, stated once (R3-02)

2026-08-20 10:56:16 -04:00
parent e3a72dc385
commit 5dc8d34472
6 changed files with 123 additions and 4 deletions
@@ -476,6 +476,17 @@ not — clients pick those up on their next browse. And a **degraded** non-rebui
 (some node failed to materialise) deliberately does not record its composition as
 applied, so the next deploy re-diffs and repairs it.

+## Quality on a UNS node
+
+A UNS reference variable mirrors its backing raw tag exactly — value, status and timestamps — so when
+that tag's driver stops communicating the mirror goes **`BadNoCommunication` with its last value
+retained**, in the same fan-out message as the raw node, and clears only when the driver re-publishes.
+A VirtualTag on the same equipment follows the same rule from its own inputs: it holds while any input
+is Bad and reports that input's sub-code. The contract, and every seam that implements it, is stated
+once in [`docs/DriverLifecycle.md` §"The quality contract"](DriverLifecycle.md#the-quality-contract);
+what a script sees is in
+[`docs/ScriptEditor.md`](ScriptEditor.md#input-quality-what-a-script-sees-and-when-it-runs-at-all).
+
 ## See also

 - [Configuration.md](Configuration.md) — the underlying config entities.