N1: a refusal of the DWORD-addressed request permanently settled the layout
as per-element, so a tag deployed before the online edit that creates its
BOOL array later read DWORD n and published byte 0 as Good. The native runtime
now keeps an explicit layout (Unsettled / Packed / PerElement) that ONLY a
reply type changes: 0xD3 settles packed (Bits[n/32], bit n%32), 0xC1 settles
per-element (Bits[n]). Refusals and comms faults leave it unsettled, so the
next read asks again. A reply whose type disagrees with the addressing it was
asked under is discarded and re-read once under the shown layout (it would be
some other element), also when an online edit re-types a settled array. A
scalar BOOL answered 0xD3 with no element bit, or not settled packed, is
refused BadTypeMismatch instead of decoding byte 0.
m1: the write-owned Degraded marker is set together with the CAS that installs
it, under one lock, so concurrent failing writes cannot leave it naming a
different instance (a good write then clears it); a refusal-only read batch
still keeps it write-owned.
m2/m3/m5: documented (breaker accounting of a superseded init; libplctag
throw-only NotImplemented assumption; the TypeMismatch write status word is
libplctag-only).
m4: test for a write on an unsettled layout (settles by a read first).
Refs #737
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
I1: the U11 Bits[n] -> Bits[n/32] rewrite was unconditional. The native
runtime now keeps the original element path until the first reply settles the
layout: 0xD3 confirms DWORD addressing (bit n%32); any other reply type (e.g.
a 0xC1 per-element BOOL array) or a refusal of the DWORD index falls back to
Bits[n] and re-reads, and a write settles the layout by a read first, so it can
never decode or write element n/32 of an element-addressed array.
I2: libplctag ErrorNoMatch/ErrorBadDevice no longer fold into NotFound (they
now read as BadConnection: comms, Degraded, LastSuccessfulRead preserved).
ErrorNotImplemented - and the native runtime's own pre-send refusals - raise
AbCipLocalRefusalException: BadNotSupported, no health, LastSuccessfulRead NOT
advanced, no backoff record, not reachable for the probe or Test Connect.
M1: the bit RMW's parent read/write status words follow the health contract
(refusal: per-tag Bad + Warning; comms: evict the parent + Degraded).
M2: device Unsupported read refusals return Refused (advance
LastSuccessfulRead); device write refusals call RecordWriteAnswered (not the
pre-send native type gate).
M3: a good write clears a Degraded a write comms fault recorded (a read-side
Degraded is still left for the read path).
M4: a superseded init throws AbCipInitializationSupersededException (not an
OCE); ShutdownAsync stamps Unknown only if no newer init published meanwhile.
M5: the sync-Dispose timing assert is 2 s against a 4 s probe read; the
unencodable-array test asserts health.
Refs #737
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
H19: Format/InvalidCast/Overflow on a client value never touched the wire but
latched Degraded; a good write set Healthy and so undid a Degraded the poll
loop had just recorded for other tags (the batch read path is worst-wins for
exactly this reason).
- The three conversion failures map to BadTypeMismatch/BadOutOfRange with a
once-per-tag Warning and no health write (AbLegacy's rule).
- A good write (scalar or bit RMW) advances LastSuccessfulRead only - the
device answered - and leaves the state alone.
- A write comms fault (thrown, or a non-refusal status word, which used to
write no health at all) is Degraded with LastSuccessfulRead preserved and
never downgrades Faulted.
Refs #737
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty