Follow-ups from the fleet-wide read-timeout audit that the S7 R2-01 read-leg
fix (PR #453) prompted. The audit confirmed S7 was the ONLY driver with the
async-read-ignores-socket-timeout hang; these are the two adjacent (non-hang)
findings it surfaced.
1. FOCAS TimeoutMs:0 footgun (the risky one): a non-positive Timeout made
SynchronizedFocasClient DISABLE its per-call wall-clock ceiling, reverting to
the caller's long-lived poll token — reintroducing exactly the frozen-peer
wedge S7 just eliminated, under misconfig. Clamp non-positive TimeoutMs to the
2s default at the config boundary so the deadline can never be authored away.
2. TimeoutMs validation symmetry: apply the same clamp in the AbCip + AbLegacy
factories. libplctag's Tag.Timeout setter throws on <=0, faulting tag creation
on every read/write; clamping keeps a misconfigured TimeoutMs:0 running on the
default bound instead. (Shared PositiveTimeoutOrDefault helper per factory.)
3. AbLegacy reconnect parity with AbCip: AbLegacy evicted the cached libplctag
runtime on neither the non-zero-status nor transport-exception read/write path
(AbCip evicts on both), so a data-path fault recovered only via the probe loop
/ libplctag internals. Added EvictRuntime + wired it into both read and write
failure paths so a fresh handle is created on the next call.
Tests: FOCAS 265->269 (clamp theory + positive), AbCip 336->339 (clamp theory +
positive), AbLegacy 209->212 (read-nonzero / read-exception / write-nonzero evict).
No production regressions; all three driver suites green.
Joseph Doherty
a5a0f96d49