fix(driver-historian-wonderware): resolve Medium code-review finding (Driver.Historian.Wonderware-009)

Apply _config.MaxValuesPerRead as a bucket cap in ReadAggregateAsync,
mirroring the existing cap in ReadRawAsync. Without this guard a processed
read over a wide time range with a small IntervalMs could accumulate an
unbounded HistorianAggregateSample list; if the serialised reply exceeded
the 16 MiB FrameWriter frame cap WriteAsync would throw and the client
correlation-id wait would hang. Truncation now logs a Warning with a hint
to widen IntervalMs or reduce the time range.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

code-reviews/Driver.Historian.Wonderware/findings.md

@@ -235,7 +235,7 @@ treat an SDK error as an empty history.
 | Severity | Medium |
 | Category | Performance and resource management |
 | Location | `Backend/HistorianDataSource.cs:382-395`, `Ipc/Contracts.cs:85-99` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `ReadAggregateAsync` drains `query.MoveNext` into `results` with
 no upper bound, unlike `ReadRawAsync`, which honours `maxValues` /
@@ -252,7 +252,7 @@ sidecar holds the whole result set in memory.
 `ReadProcessedRequest`. Reject or truncate result sets that would exceed the frame
 cap with an explicit error reply rather than letting `WriteAsync` throw.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-22 — applied `_config.MaxValuesPerRead` as a bucket cap in `ReadAggregateAsync` mirroring the raw-read path; truncation logs a Warning with the limit and a hint to widen `IntervalMs` or reduce the time range.
 
 ### Driver.Historian.Wonderware-010
 

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Backend/HistorianDataSource.cs

@@ -373,6 +373,12 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Backend
                     return Task.FromResult(results);
                 }
 
+                // Apply the same bucket cap as the raw-read path so a wide time range with a
+                // small IntervalMs cannot produce an unbounded result set that would overflow
+                // the 16 MiB FrameWriter frame cap and lose the entire reply.
+                var bucketLimit = _config.MaxValuesPerRead;
+                var bucketCount = 0;
+
                 while (query.MoveNext(out error))
                 {
                     ct.ThrowIfCancellationRequested();
@@ -386,6 +392,15 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware.Backend
                         Value = value,
                         TimestampUtc = timestamp,
                     });
+
+                    bucketCount++;
+                    if (bucketLimit > 0 && bucketCount >= bucketLimit)
+                    {
+                        Log.Warning(
+                            "HistoryRead aggregate ({Aggregate}): {Tag} truncated at {Limit} buckets — widen IntervalMs or reduce time range",
+                            aggregateColumn, tagName, bucketLimit);
+                        break;
+                    }
                 }
 
                 query.EndQuery(out _);