feat(twincat): opt-in ADS sum-read and /hosts diagnostics bag; refresh TwinCAT backlog (#645, #612)

Sum-read (#310): batches a poll's reads per device into sum commands capped at sumReadMaxItems,
per-item ADS errors mapped per tag, falls back to individual reads when the target refuses the
command. Diagnostics (#314): ADS state, app name, online-change count, task cycle/exec/jitter via
IDriverDiagnostics. Re-implemented against the current raw-byte read path (stranded auto/driver-gaps
commits predate it). Sum-write not ported. Unit tests only; live gate pending a route.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

CLAUDE.md

@@ -1130,6 +1130,11 @@ host logger factory (wired in `DriverFactoryBootstrap`; the FOCAS and TwinCAT fa
   `DriverHealthChanged.Diagnostics` / proto `has_diagnostics`+`diagnostics`; its digest is in the publish fingerprint).
 - **TwinCAT (#637):** TIME/TOD publish Float64 ms, DATE/DT a UTC DateTime; a tag authored `UDInt` keeps the raw counter
   (and keeps historizing — DateTime is not historized).
+- **TwinCAT (#645, #310/#314):** opt-in ADS sum-read (`useSumRead`, `sumReadMaxItems` default 200; reads raw bytes by index
+  group/offset and decodes with the same codecs as a single read; a target refusing the sum command (overall ADS 1792-1798)
+  flips that device to individual reads, a comms failure does not). `/hosts` diagnostics via `IDriverDiagnostics`
+  (`TwinCAT.AdsState`/`AppName`/`OnlineChangeCnt`/`CycleTimeMs`/`LastExecTimeMs`/`JitterMs`, probe-sampled). Unit-tested only; live
+  gate pending a user-approved route (the presses' routes name the Mac's old VPN IP). Sum-write not ported.
 - **AbLegacy (#636):** `AbLegacyAddress` (in `AbLegacy.Contracts`) is family-aware: PLC-5 `I:`/`O:` indices are OCTAL
   and are emitted to libplctag as decimal (libplctag's `pccc.c` parses decimal only). MicroLogix function files parse
   but read `BadNotSupported`. Indirect `N7:[N7:0]` (#646) is resolved by the driver at read/write time (index re-read

docs/drivers/TwinCAT.md

@@ -185,9 +185,47 @@ notifications; `DInt` over a `STRING(80)` → `BadTypeMismatch` in both paths wi
 the rest of the subscription Good. No PLC value held a genuine non-ASCII string
 to exercise Windows-1252 live — that rule is unit-tested only.
 
+## Sum-read and diagnostics (Gitea #645)
+
+Two items ported from the stranded `auto/driver-gaps` branch (#310, #314), re-implemented against the
+current raw-byte read path rather than cherry-picked (the branch predates the type guard, the string codec
+and the array codec). Unit-tested against the fake client only; the live gate is read-only and pending a
+route (see `docs/v3/twincat-backlog.md`).
+
+### Sum-read (opt-in)
+
+`useSumRead: true` (default **off**) batches a poll's reads for one device into ADS sum-read commands
+(`IndexGroup 0xF080`) of at most `sumReadMaxItems` symbols (default 200) instead of one round-trip per tag.
+TC2 CE 2.11 support for the sum command is unverified, hence opt-in.
+
+- The client plans each item exactly as a single read does — symbol from the Beckhoff symbol cache, declared
+  type checked by `TwinCATTypeGuard` — and then reads the raw bytes at the symbol's index group / offset in
+  one command, decoding with the same `TwinCATArrayCodec` (a scalar is a one-element array). A type-mismatched
+  item gets `BadTypeMismatch` without joining the batch; a bit-indexed BOOL and a handle-addressed symbol
+  (`0xF005`) are read individually inside the call.
+- Per-item ADS error codes map to that tag only (`MapAdsError`); the overall code is the command's.
+- **Fallback.** If the target refuses the command as a whole (overall ADS 1792–1798: service / group /
+  offset / size not supported) the client throws `TwinCATSumReadRefusedException`; the driver logs once,
+  marks the device `SumReadUnsupported`, and re-reads that batch with individual reads. The flag is sticky
+  until the driver is re-initialised. A comms-level failure is **not** a refusal: that chunk goes
+  `BadCommunicationError` and the next poll tries the sum command again.
+- A one-item chunk is just a single read. Sum-**write** is not implemented (writes stay per-tag).
+
+### `/hosts` diagnostics (`IDriverDiagnostics`)
+
+The driver implements the optional `IDriverDiagnostics` bag (the S7 `NegotiatedPduSize` precedent, #640),
+so these ride the health snapshot to `/hosts` — deliberately not synthetic raw tags. Sampled once per
+healthy probe tick: ADS device state (`ReadState`), and `TwinCAT_SystemInfoVarList` `_AppInfo.AppName`,
+`_AppInfo.OnlineChangeCnt`, `_TaskInfo[1].CycleTime`, `_TaskInfo[1].LastExecTime` (100 ns ticks).
+Keys: `TwinCAT.AdsState`, `.AppName`, `.OnlineChangeCnt`, `.CycleTimeMs`, `.LastExecTimeMs`, `.JitterMs`
+(last exec − cycle; positive = the task overran). Several devices prefix `TwinCAT.<DeviceName or host>.`;
+the host caps the bag at 16 entries. Times are rounded to 0.1 ms because the bag's digest is in the
+publish fingerprint. Each symbol is best-effort: a runtime that does not export one (older TC2) keeps the
+others, and a symbol answering "not found" is not re-asked until the client is rebuilt.
+
 ## Capability surface
 
-`TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery, ISubscribable, IHostConnectivityProbe, IPerCallHostResolver, IRediscoverable`
+`TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery, ISubscribable, IHostConnectivityProbe, IPerCallHostResolver, IRediscoverable, ISkippedTagReporter, IDriverDiagnostics`
 (`src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDriver.cs`).
 
 | Capability | Path | Notes |

docs/v3/twincat-backlog.md

@@ -5,27 +5,61 @@ The v2 TwinCAT driver is considered solid: 28 integration tests (14 `[TwinCATFac
 three latent driver bugs shaken out (notification cycle units, `STRING(N)` mapper,
 bit-indexed BOOL path). Further work is deferred.
 
-Archived from `docs/drivers/TwinCAT-Test-Fixture.md` § Follow-up candidates.
+Archived from `docs/drivers/TwinCAT-Test-Fixture.md` § Follow-up candidates. Refreshed 2026-10-08
+(Gitea #612 / #645); live-validation results live in `docs/drivers/TwinCAT.md` § "Live validation".
 
-## Deferred items
+## Hardware available (as of 2026-10-08)
 
-1. **TC2 coverage** — spin up a TC2 runtime (Windows CE IPC or legacy XAR)
+The Elma cleaner fleet (25 presses, 23 live) is the only real TwinCAT hardware in reach, and it is
-   and run the same suite; any delta surfaces. Blocked on hardware.
+**production — strictly read-only**:
 
-2. **Notification coalescing under load** — run the subscribe test while
+| Press | Runtime | AMS | Notes |
-   the PLC cycle is saturated (bump `lineSim` complexity, watch for
+|---|---|---|---|
-   dropped notifications). Doable on current rig; deferred as lower
+| 22 presses (e.g. Z33856 `10.201.45.236.1.1`, Z33733 `5.25.53.46.1.1`) | **TC2 2.11 on WinCE 6.0** | port **801** | read-validated 2026-10-07 |
-   priority than v3 feature work.
+| **Z35474** (`5.118.56.93.1.1`, 10.201.23.227) | **TC3 3.1.4024** (Win NT 10) | port **851** | the **only TC3 press**; "Plc30 App" |
+| TCBSD fixture `10.100.0.128` (`41.169.163.43.1.1:851`) | TC3 | 851 | not a press; unreachable from the Mac |
 
-3. **Multi-hop AMS route** — add a test behind an IPC gateway with a
+Access facts: ADS is TCP 48898. The driver sends no AddRoute (routes are provisioned out of band) and has
-   chained route entry. Blocked on hardware (gateway IPC).
+no IP field, so a host needs a local AMS router — TwinCAT XAR, or `Beckhoff.TwinCAT.Ads.TcpRouter` hosted
+in-process (the driver csproj does not reference TcpRouter; the 2026-10-07 run used a scratch harness).
+The Mac reaches the presses directly over the VPN. **The PLC routes left by earlier tooling are STALE:**
+they name the Mac's old VPN IP (10.181.198.189), and the Mac is now 10.181.207.140, so a source NetId of
+`10.181.207.140.1.1` has no route on any press. We must not AddRoute on production, so the **live gate for
+this backlog is deferred pending a user-approved route** (owner refreshes the route, or the user approves
+reusing the old source NetId). Nothing below that says "live" has been run against TC3.
 
-4. **License-rotation automation** — XAR's 7-day trial expires on
+## Status of the original items
-   schedule. Either automate `TcActivate.exe /reactivate` via a scheduled
-   task on the VM (not officially supported; reportedly works for some
-   TC3 builds), or buy a paid runtime license (~$1k one-time per runtime
-   per CPU) to kill the rotation. Ops item, not code.
 
-5. **Lab rig** — cheapest IPC (CX7000 / CX9020) on a dedicated network;
+1. **TC2 coverage — DONE (read side).** No longer "blocked on hardware": the 2026-10-07 Elma run
-   the only route that covers TC2 + real EtherCAT I/O timing + cycle
+   (TwinCAT 2.11) verified browse, scalar/array/string reads and native notifications on TC2. What is
-   jitter under CPU load. Blocked on hardware + budget.
+   still unverified there: sum-read support (see item 6) and anything that writes.
+
+2. **Notification coalescing under load** — run the subscribe test while the PLC cycle is saturated.
+   Needs the TCBSD fixture (loading a production press is out of the question) and the `GVL_Perf` /
+   `FB_PerfChurn` fixture project from the stranded `auto/driver-gaps` branch. Fixture-gated.
+
+3. **Multi-hop AMS route** — a test behind an IPC gateway with a chained route entry. No hardware.
+
+4. **License-rotation automation** — XAR's 7-day trial expires on schedule. Ops item, not code.
+
+5. **Lab rig** — cheapest IPC on a dedicated network; the only route that covers real EtherCAT I/O
+   timing and cycle jitter under CPU load. Blocked on hardware + budget.
+
+## Added by #612 / #645
+
+6. **ADS sum-read (#310) — code DONE, live gate pending.** Opt-in `useSumRead` / `sumReadMaxItems`
+   (see `docs/drivers/TwinCAT.md` § "Sum-read"). Unit-tested against the fake client only. Live gate
+   (read-only, valid on a press): enable on Z33856 / Z33733 (TC2) and Z35474 (TC3), compare a batched poll
+   to individual reads value-for-value, and record whether TC2 CE 2.11 answers or refuses the sum command
+   (either outcome is a result — a refusal must fall back cleanly). Needs the route above.
+
+7. **Driver diagnostics (#314) — code DONE, live gate pending.** ADS state, app name, online-change
+   count, task cycle time, last exec time and jitter on the `/hosts` diagnostics bag. Live gate: confirm
+   `TwinCAT_SystemInfoVarList._TaskInfo[1]` resolves on TC2 2.11 (the driver tolerates its absence).
+
+8. **Flat vs VirtualTree browse on TC3 (#612)** — open. Only Z35474 is TC3; read-only symbol-table
+   upload in both modes, compare leaf sets. Add a `SymbolsLoadMode` option only if Flat drops struct
+   members. Needs the route. (Flat on TC2 already proved fine: 45,083 / 42,666 variables.)
+
+9. **Discovered struct/FB member writes (#612)** — deferred: writes, never on a press; fixture-only.
+   Likewise **sum-write** was deliberately NOT ported from the stranded branch.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Contracts/TwinCATDriverOptions.cs

@@ -61,6 +61,22 @@ public sealed class TwinCATDriverOptions
     /// </summary>
     public int NotificationMaxDelayMs { get; init; }
 
+    /// <summary>
+    ///     When <c>true</c>, a poll's reads for one device are batched into ADS sum-read commands
+    ///     (IndexGroup <c>0xF080</c>) of up to <see cref="SumReadMaxItems"/> symbols each instead of one
+    ///     round-trip per tag (Gitea #645 / #310). Default <c>false</c> (opt-in): a TwinCAT 2 CE runtime's
+    ///     sum-command support is unverified. A target that refuses the sum command is detected at runtime
+    ///     and that device falls back to individual reads for the rest of the driver's life.
+    /// </summary>
+    public bool UseSumRead { get; init; }
+
+    /// <summary>
+    ///     Maximum symbols per ADS sum-read command; larger polls are split into chunks of this size.
+    ///     Bounds the request/response size against the target's ADS buffer. Values below 1 are treated as 1.
+    ///     Only consulted when <see cref="UseSumRead"/> is <c>true</c>.
+    /// </summary>
+    public int SumReadMaxItems { get; init; } = 200;
+
     /// <summary>
     ///     Timeout for the AdminUI Test Connect probe, in seconds. The AdminUI clamps to a
     ///     60s server-side maximum; this default is what the form pre-fills for new instances.

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/AdsTwinCATClient.cs

@@ -3,6 +3,7 @@ using System.Runtime.CompilerServices;
 using System.Threading.Channels;
 using TwinCAT;
 using TwinCAT.Ads;
+using TwinCAT.Ads.SumCommand;
 using TwinCAT.Ads.TypeSystem;
 using TwinCAT.TypeSystem;
 
@@ -166,6 +167,151 @@ internal sealed class AdsTwinCATClient : ITwinCATClient
         }
     }
 
+    /// <inheritdoc />
+    public async Task<IReadOnlyList<(object? value, uint status)>> ReadValuesAsync(
+        IReadOnlyList<TwinCATBulkReadItem> reads, CancellationToken cancellationToken)
+    {
+        var results = new (object? value, uint status)[reads.Count];
+        var planned = new List<PlannedSumRead>(reads.Count);
+
+        // Plan every item exactly as the single read would (symbol resolved from the Beckhoff symbol cache,
+        // declared type checked against it), but stop short of the wire read: those become ONE sum command.
+        // Anything the sum command cannot carry is read on its own right here.
+        for (var i = 0; i < reads.Count; i++)
+        {
+            var r = reads[i];
+            try
+            {
+                if (r.BitIndex is not null && r.Type == TwinCATDataType.Bool)
+                {
+                    results[i] = await ReadValueAsync(r.SymbolPath, r.Type, r.BitIndex, r.ArrayCount, cancellationToken)
+                        .ConfigureAwait(false);
+                    continue;
+                }
+
+                var (shape, array, symbol, symbolStatus) = await DescribeSymbolAsync(r.SymbolPath, cancellationToken)
+                    .ConfigureAwait(false);
+                if (symbolStatus != TwinCATStatusMapper.Good) { results[i] = (null, symbolStatus); continue; }
+
+                TwinCATArrayLayout layout;
+                if (r.ArrayCount is int count)
+                {
+                    if (TwinCATTypeGuard.CheckArray(r.Type, count, shape, array, out layout) is not null)
+                    {
+                        results[i] = (null, TwinCATStatusMapper.BadTypeMismatch);
+                        continue;
+                    }
+                }
+                else
+                {
+                    if (TwinCATTypeGuard.CheckRead(r.Type, shape) is not null)
+                    {
+                        results[i] = (null, TwinCATStatusMapper.BadTypeMismatch);
+                        continue;
+                    }
+                    // A scalar is a one-element "array" at the type's own width (a STRING at the PLC's declared
+                    // width), so scalar and array share one raw decode.
+                    layout = new TwinCATArrayLayout(1, r.Type is TwinCATDataType.String or TwinCATDataType.WString
+                        ? shape.ByteSize
+                        : TwinCATTypeGuard.DeclaredByteSize(r.Type));
+                }
+
+                // A handle-addressed symbol (0xF005) needs a fresh variable handle per read — not expressible
+                // as an index-group/offset sum entry. Read it individually.
+                if (symbol!.IndexGroup == SymbolValueByHandle)
+                {
+                    results[i] = await ReadValueAsync(r.SymbolPath, r.Type, r.BitIndex, r.ArrayCount, cancellationToken)
+                        .ConfigureAwait(false);
+                    continue;
+                }
+
+                planned.Add(new PlannedSumRead(i, symbol.IndexGroup, symbol.IndexOffset, layout, r.ArrayCount is not null));
+            }
+            catch (AdsErrorException ex)
+            {
+                results[i] = (null, MapAndSignal((uint)ex.ErrorCode));
+            }
+        }
+
+        if (planned.Count == 0) return results;
+
+        ResultSumReadRaw sum;
+        try
+        {
+            var entities = new List<IgIoSumReadEntity>(planned.Count);
+            foreach (var p in planned)
+                entities.Add(new IgIoSumReadEntity(p.IndexGroup, p.IndexOffset, p.Layout.ByteLength));
+            sum = await new SumRead(_client, entities, SumCommandErrorStrategy.Relaxed)
+                .ReadRawAsync(cancellationToken).ConfigureAwait(false);
+        }
+        catch (AdsErrorException ex) when (IsSumRefusal((uint)ex.ErrorCode))
+        {
+            throw new TwinCATSumReadRefusedException((uint)ex.ErrorCode, ex);
+        }
+        catch (AdsSumCommandException)
+        {
+            // The library gave up on the batch without an overall ADS code (a sub-item failure under its
+            // strict handling). Not a refusal of the service: read these items one by one this time.
+            foreach (var p in planned)
+                results[p.Index] = await ReadValueAsync(reads[p.Index].SymbolPath, reads[p.Index].Type,
+                    reads[p.Index].BitIndex, reads[p.Index].ArrayCount, cancellationToken).ConfigureAwait(false);
+            return results;
+        }
+
+        // The overall code is the sum command itself; per-item codes are in SubErrors.
+        if (sum.ErrorCode != AdsErrorCode.NoError)
+        {
+            var overall = (uint)sum.ErrorCode;
+            if (IsSumRefusal(overall))
+                throw new TwinCATSumReadRefusedException(overall);
+            var mapped = MapAndSignal(overall);
+            foreach (var p in planned) results[p.Index] = (null, mapped);
+            return results;
+        }
+
+        for (var k = 0; k < planned.Count; k++)
+        {
+            var p = planned[k];
+            var subError = sum.SubErrors is { } errs && k < errs.Length ? errs[k] : AdsErrorCode.NoError;
+            if (subError != AdsErrorCode.NoError)
+            {
+                results[p.Index] = (null, MapAndSignal((uint)subError));
+                continue;
+            }
+            if (sum.ReadBlocks is not { } blocks || k >= blocks.Count || blocks[k].Length < p.Layout.ByteLength)
+            {
+                // A short block would decode garbage; treat it as a size mismatch, not a value.
+                results[p.Index] = (null, TwinCATStatusMapper.MapAdsError(1797));
+                continue;
+            }
+            var decoded = TwinCATArrayCodec.Decode(reads[p.Index].Type, sum.ReadBlocks![k].Span, p.Layout, StringsAreUtf8());
+            results[p.Index] = (p.IsArray ? decoded : decoded.GetValue(0), TwinCATStatusMapper.Good);
+        }
+        return results;
+    }
+
+    private const uint SymbolValueByHandle = 0xF005;
+
+    private readonly record struct PlannedSumRead(int Index, uint IndexGroup, uint IndexOffset, TwinCATArrayLayout Layout, bool IsArray);
+
+    /// <summary>
+    ///     True for an overall ADS code that means "this target does not do sum commands" (service / index
+    ///     group / offset / size not supported) rather than a comms fault.
+    /// </summary>
+    internal static bool IsSumRefusal(uint adsError) => adsError is 1792 or 1793 or 1794 or 1795 or 1797 or 1798;
+
+    /// <inheritdoc />
+    public async Task<string?> ReadAdsStateAsync(CancellationToken cancellationToken)
+    {
+        try
+        {
+            var state = await _client.ReadStateAsync(cancellationToken).ConfigureAwait(false);
+            return state.ErrorCode == AdsErrorCode.NoError ? state.State.AdsState.ToString() : null;
+        }
+        catch (OperationCanceledException) { throw; }
+        catch { return null; }
+    }
+
     /// <summary>
     ///     Resolves the PLC symbol behind <paramref name="symbolPath"/> into the facts
     ///     <see cref="TwinCATTypeGuard"/> compares a declared type against. Uses the Beckhoff symbol

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/ITwinCATClient.cs

@@ -55,6 +55,45 @@ public interface ITwinCATClient : IDisposable
         int? arrayCount,
         CancellationToken cancellationToken);
 
+    /// <summary>
+    ///     Reads several symbols at once — the ADS sum-read path (Gitea #645 / #310). The result is a parallel
+    ///     list: element <c>i</c> is the outcome of <paramref name="reads"/>[<c>i</c>], each decoded and
+    ///     status-mapped exactly as <see cref="ReadValueAsync"/> would (an item the sum command cannot carry —
+    ///     a bit-indexed BOOL, a handle-addressed symbol — is read individually inside the call).
+    /// </summary>
+    /// <remarks>
+    ///     The default implementation reads one item at a time, so a client without a sum path (or a test
+    ///     fake) is correct if not faster. An implementation that issues a real sum command throws
+    ///     <see cref="TwinCATSumReadRefusedException"/> when the TARGET refuses the command as a whole
+    ///     (service / index group not supported); the caller then falls back to individual reads. A
+    ///     comms-level failure propagates as the ordinary exception.
+    /// </remarks>
+    /// <param name="reads">The symbols to read, at most the caller's chunk size.</param>
+    /// <param name="cancellationToken">Cancellation token for the read.</param>
+    /// <returns>One <c>(value, status)</c> per item, in request order.</returns>
+    /// <exception cref="TwinCATSumReadRefusedException">The target refused the sum command itself.</exception>
+    async Task<IReadOnlyList<(object? value, uint status)>> ReadValuesAsync(
+        IReadOnlyList<TwinCATBulkReadItem> reads, CancellationToken cancellationToken)
+    {
+        var results = new (object? value, uint status)[reads.Count];
+        for (var i = 0; i < reads.Count; i++)
+        {
+            var r = reads[i];
+            results[i] = await ReadValueAsync(r.SymbolPath, r.Type, r.BitIndex, r.ArrayCount, cancellationToken)
+                .ConfigureAwait(false);
+        }
+        return results;
+    }
+
+    /// <summary>
+    ///     The target's ADS device state (<c>Run</c>, <c>Stop</c>, <c>Config</c>, …) as text, or <c>null</c>
+    ///     when it cannot be read. Feeds the driver's <c>/hosts</c> diagnostics (Gitea #645 / #314).
+    ///     Default <c>null</c> — a client without a state read simply reports none.
+    /// </summary>
+    /// <param name="cancellationToken">Cancellation token for the read.</param>
+    /// <returns>The state name, or <c>null</c>.</returns>
+    Task<string?> ReadAdsStateAsync(CancellationToken cancellationToken) => Task.FromResult<string?>(null);
+
     /// <summary>
     ///     Write a symbolic value. Returns the mapped OPC UA status for the operation
     ///     (0 = Good, non-zero = error mapped via <see cref="TwinCATStatusMapper"/>).
@@ -132,6 +171,18 @@ public interface ITwinCATClient : IDisposable
     IAsyncEnumerable<TwinCATDiscoveredSymbol> BrowseSymbolsAsync(CancellationToken cancellationToken);
 }
 
+/// <summary>One element of an <see cref="ITwinCATClient.ReadValuesAsync"/> request — the same four facts
+/// <see cref="ITwinCATClient.ReadValueAsync"/> takes.</summary>
+/// <param name="SymbolPath">The ADS symbol path (a bit-indexed BOOL keeps its <c>.N</c> suffix, as for a single read).</param>
+/// <param name="Type">The declared data type.</param>
+/// <param name="BitIndex">The bit to extract for a BOOL-within-word tag; null otherwise.</param>
+/// <param name="ArrayCount">The authored array length for an array tag; null for a scalar.</param>
+public sealed record TwinCATBulkReadItem(
+    string SymbolPath,
+    TwinCATDataType Type,
+    int? BitIndex = null,
+    int? ArrayCount = null);
+
 /// <summary>Opaque handle for a registered ADS notification. <see cref="IDisposable.Dispose"/> tears it down.</summary>
 public interface ITwinCATNotificationHandle : IDisposable { }
 

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDeviceDiagnostics.cs

@@ -0,0 +1,25 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
+
+/// <summary>
+///     One device's probe-sampled PLC facts (Gitea #645 / #314), surfaced through the driver's
+///     <see cref="Core.Abstractions.IDriverDiagnostics"/> bag to the <c>/hosts</c> page. Every field is
+///     best-effort: a runtime that does not export a system symbol leaves that field at its last known value
+///     (null if never seen).
+/// </summary>
+/// <param name="AdsState">The ADS device state name (<c>Run</c>, <c>Stop</c>, <c>Config</c>, …).</param>
+/// <param name="AppName">The running PLC application's name (<c>_AppInfo.AppName</c>).</param>
+/// <param name="OnlineChangeCnt">How many online changes the application has taken (<c>_AppInfo.OnlineChangeCnt</c>).</param>
+/// <param name="CycleTimeMs">The first PLC task's configured cycle time in milliseconds.</param>
+/// <param name="LastExecTimeMs">How long the task's last cycle took to execute, in milliseconds.</param>
+/// <param name="UpdatedUtc">When the snapshot was taken.</param>
+internal sealed record TwinCATDeviceDiagnostics(
+    string? AdsState,
+    string? AppName,
+    uint? OnlineChangeCnt,
+    double? CycleTimeMs,
+    double? LastExecTimeMs,
+    DateTime UpdatedUtc)
+{
+    /// <summary>Gets last execution time minus cycle time: positive means the task overran its cycle.</summary>
+    public double? JitterMs => CycleTimeMs is { } c && LastExecTimeMs is { } x ? x - c : null;
+}

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDriver.cs

@@ -12,7 +12,8 @@ namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
 ///     resolver land in PRs 2 and 3.
 /// </summary>
 public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery, ISubscribable,
-    IHostConnectivityProbe, IPerCallHostResolver, IRediscoverable, ISkippedTagReporter, IDisposable, IAsyncDisposable
+    IHostConnectivityProbe, IPerCallHostResolver, IRediscoverable, ISkippedTagReporter, IDriverDiagnostics,
+    IDisposable, IAsyncDisposable
 {
     /// <summary>Authored tags this driver could not build into its poll table (Gitea #541).</summary>
     private readonly SkippedTagLedger _skippedTags = new();
@@ -271,6 +272,10 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
         var now = DateTime.UtcNow;
         var results = new DataValueSnapshot[fullReferences.Count];
 
+        // #645/#310: with UseSumRead the reads for one device are gathered and issued as ADS sum-reads
+        // after this pass; everything else (and a device that refused the sum command) reads one by one.
+        Dictionary<DeviceState, List<SumReadEntry>>? buckets = null;
+
         for (var i = 0; i < fullReferences.Count; i++)
         {
             var reference = fullReferences[i];
@@ -285,6 +290,34 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
                 continue;
             }
 
+            if (_options.UseSumRead && !device.SumReadUnsupported)
+            {
+                var parsed = TwinCATSymbolPath.TryParse(def.SymbolPath);
+                var symbolName = parsed?.ToAdsSymbolName() ?? def.SymbolPath;
+                buckets ??= [];
+                if (!buckets.TryGetValue(device, out var bucket))
+                    buckets[device] = bucket = [];
+                bucket.Add(new SumReadEntry(i, reference, def, symbolName, parsed?.BitIndex));
+                continue;
+            }
+
+            results[i] = await ReadOneAsync(reference, def, device, now, cancellationToken).ConfigureAwait(false);
+        }
+
+        if (buckets is not null)
+            foreach (var (device, bucket) in buckets)
+                await ReadBucketAsync(device, bucket, results, now, cancellationToken).ConfigureAwait(false);
+
+        return results;
+    }
+
+    private readonly record struct SumReadEntry(
+        int Index, string Reference, TwinCATTagDefinition Def, string SymbolName, int? BitIndex);
+
+    /// <summary>One tag read on its own — the pre-sum-read path, also the fallback for a refused sum command.</summary>
+    private async Task<DataValueSnapshot> ReadOneAsync(
+        string reference, TwinCATTagDefinition def, DeviceState device, DateTime now, CancellationToken cancellationToken)
+    {
         try
         {
             var client = await EnsureConnectedAsync(device, cancellationToken).ConfigureAwait(false);
@@ -297,12 +330,26 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
             var (value, status) = await client.ReadValueAsync(
                 symbolName, def.DataType, parsed?.BitIndex, def.ArrayLength, cancellationToken)
                 .ConfigureAwait(false);
-
+            return CompleteRead(reference, def, symbolName, value, status, now);
-                results[i] = new DataValueSnapshot(value, status, now, now);
+        }
-                if (status == TwinCATStatusMapper.Good)
+        catch (OperationCanceledException) { throw; }
-                    _health = new DriverHealth(DriverState.Healthy, now, null);
+        catch (Exception ex)
-                else
         {
+            _health = new DriverHealth(DriverState.Degraded, _health.LastSuccessfulRead, ex.Message);
+            return new DataValueSnapshot(null, TwinCATStatusMapper.BadCommunicationError, null, now);
+        }
+    }
+
+    /// <summary>Maps one read outcome to a snapshot and applies the health / log side effects.</summary>
+    private DataValueSnapshot CompleteRead(
+        string reference, TwinCATTagDefinition def, string symbolName, object? value, uint status, DateTime now)
+    {
+        if (status == TwinCATStatusMapper.Good)
+        {
+            _health = new DriverHealth(DriverState.Healthy, now, null);
+            return new DataValueSnapshot(value, status, now, now);
+        }
+
         if (status == TwinCATStatusMapper.BadTypeMismatch)
             _logger.LogWarning(
                 "TwinCAT driver '{DriverInstanceId}' refused '{Reference}': declared {DataType} " +
@@ -315,17 +362,63 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
                 _driverInstanceId, status, reference);
         _health = new DriverHealth(DriverState.Degraded, _health.LastSuccessfulRead,
             $"ADS status {status:X8} reading {reference}");
+        return new DataValueSnapshot(value, status, now, now);
+    }
+
+    /// <summary>
+    ///     Reads one device's gathered tags as ADS sum-reads of at most <c>SumReadMaxItems</c> symbols each.
+    ///     A target that refuses the sum command flips <see cref="DeviceState.SumReadUnsupported"/> and the
+    ///     rest of the bucket is read individually; any other failure marks only the affected chunk Bad.
+    /// </summary>
+    private async Task ReadBucketAsync(
+        DeviceState device, List<SumReadEntry> bucket, DataValueSnapshot[] results, DateTime now,
+        CancellationToken cancellationToken)
+    {
+        var chunkSize = Math.Max(1, _options.SumReadMaxItems);
+        for (var start = 0; start < bucket.Count; start += chunkSize)
+        {
+            var chunk = bucket.GetRange(start, Math.Min(chunkSize, bucket.Count - start));
+
+            if (device.SumReadUnsupported || chunk.Count == 1)
+            {
+                foreach (var e in chunk)
+                    results[e.Index] = await ReadOneAsync(e.Reference, e.Def, device, now, cancellationToken).ConfigureAwait(false);
+                continue;
+            }
+
+            try
+            {
+                var client = await EnsureConnectedAsync(device, cancellationToken).ConfigureAwait(false);
+                var items = new TwinCATBulkReadItem[chunk.Count];
+                for (var k = 0; k < chunk.Count; k++)
+                    items[k] = new TwinCATBulkReadItem(chunk[k].SymbolName, chunk[k].Def.DataType, chunk[k].BitIndex, chunk[k].Def.ArrayLength);
+
+                var bulk = await client.ReadValuesAsync(items, cancellationToken).ConfigureAwait(false);
+                for (var k = 0; k < chunk.Count; k++)
+                {
+                    var e = chunk[k];
+                    var (value, status) = k < bulk.Count ? bulk[k] : (null, TwinCATStatusMapper.BadCommunicationError);
+                    results[e.Index] = CompleteRead(e.Reference, e.Def, e.SymbolName, value, status, now);
                 }
             }
             catch (OperationCanceledException) { throw; }
+            catch (TwinCATSumReadRefusedException refused)
+            {
+                device.SumReadUnsupported = true;
+                _logger.LogWarning(
+                    "TwinCAT driver '{DriverInstanceId}' device '{Device}' refused the ADS sum-read command " +
+                    "(ADS error {AdsError}); falling back to individual reads for this device",
+                    _driverInstanceId, device.Options.HostAddress, refused.AdsErrorCode);
+                foreach (var e in chunk)
+                    results[e.Index] = await ReadOneAsync(e.Reference, e.Def, device, now, cancellationToken).ConfigureAwait(false);
+            }
             catch (Exception ex)
             {
-                results[i] = new DataValueSnapshot(null, TwinCATStatusMapper.BadCommunicationError, null, now);
+                foreach (var e in chunk)
+                    results[e.Index] = new DataValueSnapshot(null, TwinCATStatusMapper.BadCommunicationError, null, now);
                 _health = new DriverHealth(DriverState.Degraded, _health.LastSuccessfulRead, ex.Message);
             }
         }
-
-        return results;
     }
 
     // ---- IWritable ----
@@ -793,7 +886,11 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
                 else
                     // 05/STAB-16: on a healthy tick, re-register any notifications whose replay
                     // failed (a transient AddNotification blip) so they recover without a client swap.
+                {
                     await RetryDeadRegistrationsAsync(state, ct).ConfigureAwait(false);
+                    // #645/#314: sample the PLC state / task-cycle facts for /hosts. Best-effort.
+                    await SampleDeviceDiagnosticsAsync(state, client, ct).ConfigureAwait(false);
+                }
             }
             catch (OperationCanceledException) when (ct.IsCancellationRequested) { break; }
             catch
@@ -813,6 +910,114 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
         }
     }
 
+    // ---- IDriverDiagnostics (#645 / #314) ----
+
+    // Well-known system symbols, exported by TC3 (and most TC2) PLC runtimes under TwinCAT_SystemInfoVarList.
+    // _TaskInfo[1] is the first PLC task; CycleTime / LastExecTime are UDINT counts of 100 ns.
+    internal const string SymOnlineChangeCnt = "TwinCAT_SystemInfoVarList._AppInfo.OnlineChangeCnt";
+    internal const string SymAppName = "TwinCAT_SystemInfoVarList._AppInfo.AppName";
+    internal const string SymCycleTime = "TwinCAT_SystemInfoVarList._TaskInfo[1].CycleTime";
+    internal const string SymLastExecTime = "TwinCAT_SystemInfoVarList._TaskInfo[1].LastExecTime";
+
+    /// <summary>Converts a TwinCAT 100 ns tick count to milliseconds.</summary>
+    internal static double TicksToMilliseconds(uint ticks100ns) => ticks100ns / 10_000.0;
+
+    /// <summary>
+    ///     Most recent <see cref="TwinCATDeviceDiagnostics"/> for a device, or null before its first
+    ///     successful probe sample (or for an unknown host address).
+    /// </summary>
+    /// <param name="hostAddress">The device's ADS host address.</param>
+    /// <returns>The snapshot, or null.</returns>
+    internal TwinCATDeviceDiagnostics? GetDeviceDiagnostics(string hostAddress) =>
+        _devices.TryGetValue(hostAddress, out var s) ? s.LastDiagnostics : null;
+
+    /// <summary>
+    ///     Samples the ADS device state and the four system symbols once per healthy probe tick and stores the
+    ///     result on <see cref="DeviceState.LastDiagnostics"/>. Every read is individually best-effort: a
+    ///     runtime that does not export a symbol (older TwinCAT 2 builds) keeps the previous value, and a
+    ///     symbol that answers "not found" is not asked again until the client is rebuilt. Never throws
+    ///     (except cancellation) — diagnostics must not disturb the probe.
+    /// </summary>
+    internal async Task SampleDeviceDiagnosticsAsync(DeviceState state, ITwinCATClient client, CancellationToken ct)
+    {
+        try
+        {
+            var prev = state.LastDiagnostics;
+            var adsState = prev?.AdsState;
+            try { adsState = await client.ReadAdsStateAsync(ct).ConfigureAwait(false) ?? adsState; }
+            catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
+            catch { /* keep previous */ }
+
+            var appName = await ReadDiagSymbolAsync(state, client, SymAppName, TwinCATDataType.String, ct).ConfigureAwait(false) as string
+                ?? prev?.AppName;
+            var onlineChange = ToUInt(await ReadDiagSymbolAsync(state, client, SymOnlineChangeCnt, TwinCATDataType.UDInt, ct).ConfigureAwait(false))
+                ?? prev?.OnlineChangeCnt;
+            var cycleTicks = ToUInt(await ReadDiagSymbolAsync(state, client, SymCycleTime, TwinCATDataType.UDInt, ct).ConfigureAwait(false));
+            var execTicks = ToUInt(await ReadDiagSymbolAsync(state, client, SymLastExecTime, TwinCATDataType.UDInt, ct).ConfigureAwait(false));
+            var cycleMs = cycleTicks is { } c ? TicksToMilliseconds(c) : prev?.CycleTimeMs;
+            var execMs = execTicks is { } x ? TicksToMilliseconds(x) : prev?.LastExecTimeMs;
+
+            state.LastDiagnostics = new TwinCATDeviceDiagnostics(adsState, appName, onlineChange, cycleMs, execMs, DateTime.UtcNow);
+        }
+        catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
+        catch { /* best-effort */ }
+    }
+
+    private static uint? ToUInt(object? v) => v switch
+    {
+        uint u => u,
+        null => null,
+        _ => Convert.ToUInt32(v, System.Globalization.CultureInfo.InvariantCulture),
+    };
+
+    private async Task<object?> ReadDiagSymbolAsync(
+        DeviceState state, ITwinCATClient client, string symbol, TwinCATDataType type, CancellationToken ct)
+    {
+        if (state.UnavailableDiagSymbols.ContainsKey(symbol)) return null;
+        try
+        {
+            var (value, status) = await client.ReadValueAsync(symbol, type, null, null, ct).ConfigureAwait(false);
+            if (status == TwinCATStatusMapper.Good) return value;
+            if (status == TwinCATStatusMapper.BadNodeIdUnknown)
+                state.UnavailableDiagSymbols[symbol] = 0;
+            return null;
+        }
+        catch (OperationCanceledException) when (ct.IsCancellationRequested) { throw; }
+        catch { return null; }
+    }
+
+    /// <summary>
+    ///     The <c>/hosts</c> diagnostics bag (Gitea #640 channel): per device, ADS state, PLC app name, online
+    ///     change count, task cycle time, last execution time and jitter (last exec − cycle). A single-device
+    ///     driver uses flat <c>TwinCAT.*</c> keys; several devices prefix the device name (or host address).
+    ///     A pure in-memory read — the probe loop does the sampling. The host bounds the bag
+    ///     (<see cref="DriverDiagnostics.MaxEntries"/>), so a many-device driver keeps the first keys in
+    ///     ordinal order.
+    /// </summary>
+    /// <returns>The key/value pairs; empty before the first sample.</returns>
+    IReadOnlyDictionary<string, string> IDriverDiagnostics.GetDiagnostics()
+    {
+        var bag = new Dictionary<string, string>(StringComparer.Ordinal);
+        var multi = _devices.Count > 1;
+        foreach (var state in _devices.Values)
+        {
+            if (state.LastDiagnostics is not { } d) continue;
+            var prefix = multi ? $"TwinCAT.{state.Options.DeviceName ?? state.Options.HostAddress}." : "TwinCAT.";
+            if (d.AdsState is not null) bag[prefix + "AdsState"] = d.AdsState;
+            if (!string.IsNullOrEmpty(d.AppName)) bag[prefix + "AppName"] = d.AppName;
+            if (d.OnlineChangeCnt is { } oc) bag[prefix + "OnlineChangeCnt"] = oc.ToString(System.Globalization.CultureInfo.InvariantCulture);
+            if (d.CycleTimeMs is { } cy) bag[prefix + "CycleTimeMs"] = FormatMs(cy);
+            if (d.LastExecTimeMs is { } ex) bag[prefix + "LastExecTimeMs"] = FormatMs(ex);
+            if (d.JitterMs is { } j) bag[prefix + "JitterMs"] = FormatMs(j);
+        }
+        return bag;
+    }
+
+    // 0.1 ms resolution: the bag is published on a heartbeat and its digest is in the publish fingerprint,
+    // so sub-0.1 ms wobble should not read as a change.
+    private static string FormatMs(double ms) =>
+        Math.Round(ms, 1, MidpointRounding.AwayFromZero).ToString("0.0", System.Globalization.CultureInfo.InvariantCulture);
+
     private void TransitionDeviceState(DeviceState state, HostState newState)
     {
         HostState old;
@@ -1234,10 +1439,22 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
         public Task? ProbeTask { get; set; }
 
         /// <summary>Disposes the active ADS client if any.</summary>
+        /// <summary>Set when the target refused the ADS sum-read command (#645); the device reads one tag at a
+        ///     time from then on. Cleared only by a fresh <see cref="DeviceState"/> (driver re-initialise).</summary>
+        public volatile bool SumReadUnsupported;
+
+        /// <summary>Latest probe-sampled PLC diagnostics (#645 / #314); null before the first sample.</summary>
+        public TwinCATDeviceDiagnostics? LastDiagnostics { get; set; }
+
+        /// <summary>Diagnostic system symbols the target answered "not found" for — not re-asked until the client is rebuilt.</summary>
+        public ConcurrentDictionary<string, byte> UnavailableDiagSymbols { get; } = new(StringComparer.Ordinal);
+
         public void DisposeClient()
         {
             Client?.Dispose();
             Client = null;
+            // A rebuilt client may face a PLC that now exports the symbols (e.g. after a program download).
+            UnavailableDiagSymbols.Clear();
         }
 
         /// <summary>Disposes the connection gate semaphore.</summary>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDriverFactoryExtensions.cs

@@ -78,6 +78,8 @@ public static class TwinCATDriverFactoryExtensions
             UseNativeNotifications = dto.UseNativeNotifications ?? true,
             EnableControllerBrowse = dto.EnableControllerBrowse ?? false,
             NotificationMaxDelayMs = dto.NotificationMaxDelayMs ?? 0,
+            UseSumRead = dto.UseSumRead ?? false,
+            SumReadMaxItems = dto.SumReadMaxItems ?? 200,
         };
     }
 
@@ -114,6 +116,12 @@ public static class TwinCATDriverFactoryExtensions
         /// <summary>Gets or sets the maximum notification delay in milliseconds.</summary>
         public int? NotificationMaxDelayMs { get; init; }
 
+        /// <summary>Gets or sets a value indicating whether a poll's reads are batched into ADS sum-reads.</summary>
+        public bool? UseSumRead { get; init; }
+
+        /// <summary>Gets or sets the maximum symbols per sum-read command.</summary>
+        public int? SumReadMaxItems { get; init; }
+
         /// <summary>Gets or sets the list of configured devices.</summary>
         public List<TwinCATDeviceDto>? Devices { get; init; }
 

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATSumReadRefusedException.cs

@@ -0,0 +1,21 @@
+namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
+
+/// <summary>
+///     Thrown by <see cref="ITwinCATClient.ReadValuesAsync"/> when the TARGET refuses the ADS sum-read
+///     command as a whole (service or index group not supported). It is not a comms fault: the driver marks
+///     the device "no sum-read" and re-reads the batch with individual reads, so the poll still completes.
+/// </summary>
+internal sealed class TwinCATSumReadRefusedException : Exception
+{
+    /// <summary>Initializes a new instance of the <see cref="TwinCATSumReadRefusedException"/> class.</summary>
+    /// <param name="adsErrorCode">The overall ADS error code the target answered with.</param>
+    /// <param name="inner">The underlying exception, if any.</param>
+    public TwinCATSumReadRefusedException(uint adsErrorCode, Exception? inner = null)
+        : base($"ADS sum-read refused by the target (ADS error {adsErrorCode})", inner)
+    {
+        AdsErrorCode = adsErrorCode;
+    }
+
+    /// <summary>Gets the overall ADS error code.</summary>
+    public uint AdsErrorCode { get; }
+}

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Drivers/Forms/TwinCATDriverForm.razor

@@ -43,6 +43,20 @@
                              class="form-control form-control-sm" />
                 <div class="form-text">0 = push immediately. Increase to coalesce high-churn signals.</div>
             </div>
+            <div class="col-md-4 mb-3">
+                <div class="form-check form-switch mt-4">
+                    <InputCheckbox id="tcSumRead" @bind-Value="_form.UseSumRead" @bind-Value:after="EmitAsync"
+                                   class="form-check-input" />
+                    <label class="form-check-label" for="tcSumRead">Batch polled reads (ADS sum-read)</label>
+                </div>
+                <div class="form-text">One round-trip per chunk instead of per tag. Falls back to single reads if the target refuses it. Default off.</div>
+            </div>
+            <div class="col-md-4 mb-3">
+                <label class="form-label" for="tcSumReadMax">Sum-read max items</label>
+                <InputNumber id="tcSumReadMax" @bind-Value="_form.SumReadMaxItems" @bind-Value:after="EmitAsync"
+                             class="form-control form-control-sm" />
+                <div class="form-text">Symbols per sum-read command (default 200).</div>
+            </div>
         </div>
     </div>
 </section>
@@ -151,6 +165,8 @@
         public bool UseNativeNotifications { get; set; } = true;
         public bool EnableControllerBrowse { get; set; } = false;
         public int NotificationMaxDelayMs { get; set; } = 0;
+        public bool UseSumRead { get; set; } = false;
+        public int SumReadMaxItems { get; set; } = 200;
 
         // Probe
         public bool ProbeEnabled { get; set; } = true;
@@ -168,6 +184,8 @@
             UseNativeNotifications = o.UseNativeNotifications,
             EnableControllerBrowse = o.EnableControllerBrowse,
             NotificationMaxDelayMs = o.NotificationMaxDelayMs,
+            UseSumRead = o.UseSumRead,
+            SumReadMaxItems = o.SumReadMaxItems,
             ProbeEnabled = o.Probe.Enabled,
             ProbeIntervalSeconds = (int)o.Probe.Interval.TotalSeconds,
             ProbeTimeoutSeconds = (int)o.Probe.Timeout.TotalSeconds,
@@ -181,6 +199,8 @@
             UseNativeNotifications = UseNativeNotifications,
             EnableControllerBrowse = EnableControllerBrowse,
             NotificationMaxDelayMs = NotificationMaxDelayMs,
+            UseSumRead = UseSumRead,
+            SumReadMaxItems = SumReadMaxItems,
             Probe = new TwinCATProbeOptions
             {
                 Enabled = ProbeEnabled,

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests/FakeTwinCATClient.cs

@@ -71,12 +71,49 @@ internal class FakeTwinCATClient : ITwinCATClient
         string symbolPath, TwinCATDataType type, int? bitIndex, int? arrayCount, CancellationToken ct)
     {
         if (ThrowOnRead) throw Exception ?? new InvalidOperationException();
+        SingleReadCount++;
         LastReadArrayCount = arrayCount;
         var status = ReadStatuses.TryGetValue(symbolPath, out var s) ? s : TwinCATStatusMapper.Good;
         var value = Values.TryGetValue(symbolPath, out var v) ? v : null;
         return Task.FromResult((value, status));
     }
 
+    /// <summary>Gets the number of individual <see cref="ReadValueAsync"/> calls served.</summary>
+    public int SingleReadCount { get; private set; }
+    /// <summary>Gets the size of each <see cref="ReadValuesAsync"/> batch the driver issued, in order (#645).</summary>
+    public List<int> SumReadBatches { get; } = new();
+    /// <summary>Gets or sets an exception <see cref="ReadValuesAsync"/> throws instead of answering — a
+    ///     <see cref="TwinCATSumReadRefusedException"/> models a target without sum commands.</summary>
+    public Exception? SumReadException { get; set; }
+    /// <summary>Gets or sets the ADS state text <see cref="ReadAdsStateAsync"/> returns.</summary>
+    public string? AdsStateText { get; set; }
+
+    /// <summary>Simulates an ADS sum-read: records the batch size, then answers each item from the same
+    ///     tables the single read uses.</summary>
+    /// <param name="reads">The batch.</param>
+    /// <param name="ct">The cancellation token.</param>
+    /// <returns>One outcome per item.</returns>
+    public virtual Task<IReadOnlyList<(object? value, uint status)>> ReadValuesAsync(
+        IReadOnlyList<TwinCATBulkReadItem> reads, CancellationToken ct)
+    {
+        if (ThrowOnRead) throw Exception ?? new InvalidOperationException();
+        SumReadBatches.Add(reads.Count);
+        if (SumReadException is { } ex) throw ex;
+        var results = new (object? value, uint status)[reads.Count];
+        for (var i = 0; i < reads.Count; i++)
+        {
+            var path = reads[i].SymbolPath;
+            results[i] = (Values.TryGetValue(path, out var v) ? v : null,
+                ReadStatuses.TryGetValue(path, out var s) ? s : TwinCATStatusMapper.Good);
+        }
+        return Task.FromResult<IReadOnlyList<(object? value, uint status)>>(results);
+    }
+
+    /// <summary>Simulates reading the ADS device state.</summary>
+    /// <param name="ct">The cancellation token.</param>
+    /// <returns>The configured state text.</returns>
+    public virtual Task<string?> ReadAdsStateAsync(CancellationToken ct) => Task.FromResult(AdsStateText);
+
     /// <summary>Simulates writing a value to a symbol.</summary>
     /// <param name="symbolPath">The path to the symbol to write.</param>
     /// <param name="type">The data type of the symbol.</param>

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests/TwinCATDiagnosticsTests.cs

@@ -0,0 +1,148 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;
+
+/// <summary>Gitea #645 / #314 — PLC state / task-cycle facts on the optional IDriverDiagnostics bag.</summary>
+[Trait("Category", "Unit")]
+public sealed class TwinCATDiagnosticsTests
+{
+    private const string Host1 = "ads://5.23.91.23.1.1:851";
+    private const string Host2 = "ads://5.23.91.24.1.1:851";
+
+    private static TwinCATDriver NewDriver(FakeTwinCATClientFactory factory, bool probe, params (string host, string? name)[] devices) =>
+        new(new TwinCATDriverOptions
+        {
+            Devices = [.. devices.Select(d => new TwinCATDeviceOptions(d.host, d.name))],
+            Probe = new TwinCATProbeOptions { Enabled = probe, Interval = TimeSpan.FromMilliseconds(20) },
+        }, "drv-diag", factory);
+
+    private static FakeTwinCATClient PlcClient() => new()
+    {
+        AdsStateText = "Run",
+        Values =
+        {
+            [TwinCATDriver.SymAppName] = "Plc30 App",
+            [TwinCATDriver.SymOnlineChangeCnt] = 7u,
+            [TwinCATDriver.SymCycleTime] = 100_000u,   // 10.0 ms
+            [TwinCATDriver.SymLastExecTime] = 25_000u, // 2.5 ms
+        },
+    };
+
+    private static async Task Sample(TwinCATDriver drv, FakeTwinCATClient client, string host)
+    {
+        var state = drv.GetDeviceState(host)!;
+        await drv.SampleDeviceDiagnosticsAsync(state, client, CancellationToken.None);
+    }
+
+    /// <summary>Verifies the driver advertises the optional capability and is empty before any sample.</summary>
+    [Fact]
+    public async Task Bag_is_empty_before_the_first_sample()
+    {
+        var drv = NewDriver(new FakeTwinCATClientFactory(), false, (Host1, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+
+        var diag = drv.ShouldBeAssignableTo<IDriverDiagnostics>()!;
+        diag.GetDiagnostics().ShouldBeEmpty();
+    }
+
+    /// <summary>Verifies a single-device driver publishes flat keys with state, app, cycle, exec and jitter.</summary>
+    [Fact]
+    public async Task Single_device_publishes_flat_keys()
+    {
+        var drv = NewDriver(new FakeTwinCATClientFactory(), false, (Host1, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        await Sample(drv, PlcClient(), Host1);
+
+        var bag = ((IDriverDiagnostics)drv).GetDiagnostics();
+
+        bag["TwinCAT.AdsState"].ShouldBe("Run");
+        bag["TwinCAT.AppName"].ShouldBe("Plc30 App");
+        bag["TwinCAT.OnlineChangeCnt"].ShouldBe("7");
+        bag["TwinCAT.CycleTimeMs"].ShouldBe("10.0");
+        bag["TwinCAT.LastExecTimeMs"].ShouldBe("2.5");
+        bag["TwinCAT.JitterMs"].ShouldBe("-7.5");
+        DriverDiagnostics.Bound(bag).Count.ShouldBe(bag.Count); // within the host's 16-entry cap
+    }
+
+    /// <summary>Verifies several devices are told apart by device name, falling back to host address.</summary>
+    [Fact]
+    public async Task Multiple_devices_are_prefixed()
+    {
+        var drv = NewDriver(new FakeTwinCATClientFactory(), false, (Host1, "Elma01"), (Host2, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        await Sample(drv, PlcClient(), Host1);
+        await Sample(drv, PlcClient(), Host2);
+
+        var bag = ((IDriverDiagnostics)drv).GetDiagnostics();
+
+        bag["TwinCAT.Elma01.AdsState"].ShouldBe("Run");
+        bag[$"TwinCAT.{Host2}.CycleTimeMs"].ShouldBe("10.0");
+        bag.ContainsKey("TwinCAT.AdsState").ShouldBeFalse();
+    }
+
+    /// <summary>Verifies a runtime without _TaskInfo (older TwinCAT 2) still yields the facts it has, and
+    /// the missing symbols are asked for once, not on every probe tick.</summary>
+    [Fact]
+    public async Task Missing_task_info_gives_a_partial_bag_and_is_not_re_asked()
+    {
+        var drv = NewDriver(new FakeTwinCATClientFactory(), false, (Host1, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        var client = new FakeTwinCATClient { AdsStateText = "Run" };
+        client.Values[TwinCATDriver.SymAppName] = "Plc1";
+        client.ReadStatuses[TwinCATDriver.SymCycleTime] = TwinCATStatusMapper.BadNodeIdUnknown;
+        client.ReadStatuses[TwinCATDriver.SymLastExecTime] = TwinCATStatusMapper.BadNodeIdUnknown;
+        client.ReadStatuses[TwinCATDriver.SymOnlineChangeCnt] = TwinCATStatusMapper.BadNodeIdUnknown;
+
+        await Sample(drv, client, Host1);
+        var readsAfterFirst = client.SingleReadCount;
+        await Sample(drv, client, Host1);
+
+        var bag = ((IDriverDiagnostics)drv).GetDiagnostics();
+        bag["TwinCAT.AdsState"].ShouldBe("Run");
+        bag["TwinCAT.AppName"].ShouldBe("Plc1");
+        bag.Keys.ShouldNotContain("TwinCAT.CycleTimeMs");
+        bag.Keys.ShouldNotContain("TwinCAT.JitterMs");
+        client.SingleReadCount.ShouldBe(readsAfterFirst + 1); // only AppName is read again
+    }
+
+    /// <summary>Verifies a failed sample keeps the previous snapshot rather than blanking the bag.</summary>
+    [Fact]
+    public async Task Failed_sample_keeps_the_last_values()
+    {
+        var drv = NewDriver(new FakeTwinCATClientFactory(), false, (Host1, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        var client = PlcClient();
+        await Sample(drv, client, Host1);
+
+        client.ThrowOnRead = true;
+        client.AdsStateText = null;
+        await Sample(drv, client, Host1);
+
+        var bag = ((IDriverDiagnostics)drv).GetDiagnostics();
+        bag["TwinCAT.CycleTimeMs"].ShouldBe("10.0");
+        bag["TwinCAT.AdsState"].ShouldBe("Run");
+    }
+
+    /// <summary>Verifies the probe loop itself fills the bag — no manual sampling.</summary>
+    [Fact]
+    public async Task Probe_loop_populates_the_bag()
+    {
+        var factory = new FakeTwinCATClientFactory { Customise = PlcClient };
+        var drv = NewDriver(factory, true, (Host1, null));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        try
+        {
+            IReadOnlyDictionary<string, string> bag = new Dictionary<string, string>();
+            for (var i = 0; i < 100 && bag.Count == 0; i++)
+            {
+                await Task.Delay(50);
+                bag = ((IDriverDiagnostics)drv).GetDiagnostics();
+            }
+            bag["TwinCAT.OnlineChangeCnt"].ShouldBe("7");
+        }
+        finally { await drv.ShutdownAsync(CancellationToken.None); }
+    }
+}

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests/TwinCATSumReadTests.cs

@@ -0,0 +1,237 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Driver.TwinCAT;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Tests;
+
+/// <summary>Gitea #645 / #310 — a poll's reads batched into ADS sum-read commands, with per-item status,
+/// a chunk cap and a fallback to individual reads when the target refuses the command.</summary>
+[Trait("Category", "Unit")]
+public sealed class TwinCATSumReadTests
+{
+    private const string Host = "ads://5.23.91.23.1.1:851";
+
+    private static TwinCATTagDefinition Tag(string name, TwinCATDataType type = TwinCATDataType.DInt) =>
+        new(name, Host, "MAIN." + name, type);
+
+    private static (TwinCATDriver drv, FakeTwinCATClientFactory factory) NewDriver(
+        bool useSumRead, int maxItems, params TwinCATTagDefinition[] tags)
+    {
+        var factory = new FakeTwinCATClientFactory();
+        var drv = new TwinCATDriver(new TwinCATDriverOptions
+        {
+            Devices = [new TwinCATDeviceOptions(Host)],
+            RawTags = TwinCATRawTags.Entries(tags),
+            Probe = new TwinCATProbeOptions { Enabled = false },
+            UseSumRead = useSumRead,
+            SumReadMaxItems = maxItems,
+        }, "drv-sum", factory);
+        return (drv, factory);
+    }
+
+    private static FakeTwinCATClient Seeded(params (string symbol, object value)[] values)
+    {
+        var c = new FakeTwinCATClient();
+        foreach (var (symbol, value) in values) c.Values[symbol] = value;
+        return c;
+    }
+
+    /// <summary>Verifies that sum-read is opt-in: off, every tag is read on its own.</summary>
+    [Fact]
+    public async Task Disabled_reads_each_tag_individually()
+    {
+        var (drv, factory) = NewDriver(false, 200, Tag("A"), Tag("B"), Tag("C"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () => Seeded(("MAIN.A", 1), ("MAIN.B", 2), ("MAIN.C", 3));
+
+        var snaps = await drv.ReadAsync(["A", "B", "C"], CancellationToken.None);
+
+        snaps.Select(s => s.Value).ShouldBe([1, 2, 3]);
+        factory.Clients[0].SumReadBatches.ShouldBeEmpty();
+        factory.Clients[0].SingleReadCount.ShouldBe(3);
+    }
+
+    /// <summary>Verifies that one poll's tags go out as a single sum command, values in request order.</summary>
+    [Fact]
+    public async Task Enabled_batches_a_poll_into_one_sum_command()
+    {
+        var (drv, factory) = NewDriver(true, 200, Tag("A"), Tag("B"), Tag("C"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () => Seeded(("MAIN.A", 1), ("MAIN.B", 2), ("MAIN.C", 3));
+
+        var snaps = await drv.ReadAsync(["C", "A", "B"], CancellationToken.None);
+
+        snaps.Select(s => s.Value).ShouldBe([3, 1, 2]);
+        snaps.ShouldAllBe(s => s.StatusCode == TwinCATStatusMapper.Good);
+        factory.Clients[0].SumReadBatches.ShouldBe([3]);
+        factory.Clients[0].SingleReadCount.ShouldBe(0);
+    }
+
+    /// <summary>Verifies that one item's error code lands on that tag only.</summary>
+    [Fact]
+    public async Task Per_item_error_code_is_mapped_to_that_tag_only()
+    {
+        var (drv, factory) = NewDriver(true, 200, Tag("A"), Tag("B"), Tag("C"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () =>
+        {
+            var c = Seeded(("MAIN.A", 1), ("MAIN.C", 3));
+            c.ReadStatuses["MAIN.B"] = TwinCATStatusMapper.BadNodeIdUnknown; // ADS 1808 DeviceSymbolNotFound
+            return c;
+        };
+
+        var snaps = await drv.ReadAsync(["A", "B", "C"], CancellationToken.None);
+
+        snaps[0].StatusCode.ShouldBe(TwinCATStatusMapper.Good);
+        snaps[1].StatusCode.ShouldBe(TwinCATStatusMapper.BadNodeIdUnknown);
+        snaps[1].Value.ShouldBeNull();
+        snaps[2].StatusCode.ShouldBe(TwinCATStatusMapper.Good);
+        snaps[2].Value.ShouldBe(3);
+    }
+
+    /// <summary>Verifies the size cap: a bigger poll splits into chunks and a lone remainder reads singly.</summary>
+    [Fact]
+    public async Task Poll_larger_than_the_cap_is_split_into_chunks()
+    {
+        var tags = Enumerable.Range(0, 5).Select(i => Tag("T" + i)).ToArray();
+        var (drv, factory) = NewDriver(true, 2, tags);
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () =>
+        {
+            var c = new FakeTwinCATClient();
+            for (var i = 0; i < 5; i++) c.Values["MAIN.T" + i] = i * 10;
+            return c;
+        };
+
+        var snaps = await drv.ReadAsync([.. tags.Select(t => t.Name)], CancellationToken.None);
+
+        snaps.Select(s => s.Value).ShouldBe([0, 10, 20, 30, 40]);
+        factory.Clients[0].SumReadBatches.ShouldBe([2, 2]);
+        factory.Clients[0].SingleReadCount.ShouldBe(1); // the 5th tag: a one-item "batch" is just a read
+    }
+
+    /// <summary>Verifies the refusal fallback: the poll still completes and the device stops asking.</summary>
+    [Fact]
+    public async Task Refused_sum_command_falls_back_to_individual_reads_and_sticks()
+    {
+        var (drv, factory) = NewDriver(true, 200, Tag("A"), Tag("B"), Tag("C"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () =>
+        {
+            var c = Seeded(("MAIN.A", 1), ("MAIN.B", 2), ("MAIN.C", 3));
+            c.SumReadException = new TwinCATSumReadRefusedException(1793);
+            return c;
+        };
+
+        var first = await drv.ReadAsync(["A", "B", "C"], CancellationToken.None);
+        var second = await drv.ReadAsync(["A", "B", "C"], CancellationToken.None);
+
+        first.Select(s => s.Value).ShouldBe([1, 2, 3]);
+        first.ShouldAllBe(s => s.StatusCode == TwinCATStatusMapper.Good);
+        second.Select(s => s.Value).ShouldBe([1, 2, 3]);
+        factory.Clients[0].SumReadBatches.ShouldBe([3]);   // tried once, never again
+        factory.Clients[0].SingleReadCount.ShouldBe(6);
+        drv.GetHealth().State.ShouldBe(Core.Abstractions.DriverState.Healthy);
+    }
+
+    /// <summary>Verifies a comms failure is not mistaken for a refusal: the chunk goes Bad, sum stays on.</summary>
+    [Fact]
+    public async Task Comms_failure_marks_the_chunk_bad_and_does_not_disable_sum_read()
+    {
+        var (drv, factory) = NewDriver(true, 200, Tag("A"), Tag("B"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () =>
+        {
+            var c = Seeded(("MAIN.A", 1), ("MAIN.B", 2));
+            c.SumReadException = new InvalidOperationException("router gone");
+            return c;
+        };
+
+        var failed = await drv.ReadAsync(["A", "B"], CancellationToken.None);
+        factory.Clients[0].SumReadException = null;
+        var recovered = await drv.ReadAsync(["A", "B"], CancellationToken.None);
+
+        failed.ShouldAllBe(s => s.StatusCode == TwinCATStatusMapper.BadCommunicationError);
+        recovered.Select(s => s.Value).ShouldBe([1, 2]);
+        factory.Clients[0].SumReadBatches.ShouldBe([2, 2]);
+    }
+
+    /// <summary>Verifies unknown references do not disturb result order.</summary>
+    [Fact]
+    public async Task Unknown_reference_keeps_its_slot_in_a_batched_poll()
+    {
+        var (drv, factory) = NewDriver(true, 200, Tag("A"), Tag("B"));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        factory.Customise = () => Seeded(("MAIN.A", 1), ("MAIN.B", 2));
+
+        var snaps = await drv.ReadAsync(["A", "nope", "B"], CancellationToken.None);
+
+        snaps[0].Value.ShouldBe(1);
+        snaps[1].StatusCode.ShouldBe(TwinCATStatusMapper.BadNodeIdUnknown);
+        snaps[2].Value.ShouldBe(2);
+        factory.Clients[0].SumReadBatches.ShouldBe([2]);
+    }
+
+    /// <summary>Verifies the batch carries bit index and array length so the client decodes like a single read.</summary>
+    [Fact]
+    public async Task Bulk_items_carry_array_length_and_bit_index()
+    {
+        var captured = new List<TwinCATBulkReadItem>();
+        var factory = new FakeTwinCATClientFactory { Customise = () => new CapturingClient(captured) };
+        var drv = new TwinCATDriver(new TwinCATDriverOptions
+        {
+            Devices = [new TwinCATDeviceOptions(Host)],
+            RawTags = TwinCATRawTags.Entries([
+                new TwinCATTagDefinition("Arr", Host, "MAIN.Arr", TwinCATDataType.Int, ArrayLength: 4),
+                new TwinCATTagDefinition("Bit", Host, "MAIN.Word.3", TwinCATDataType.Bool),
+            ]),
+            Probe = new TwinCATProbeOptions { Enabled = false },
+            UseSumRead = true,
+        }, "drv-sum", factory);
+        await drv.InitializeAsync("{}", CancellationToken.None);
+
+        await drv.ReadAsync(["Arr", "Bit"], CancellationToken.None);
+
+        captured.Count.ShouldBe(2);
+        captured[0].ArrayCount.ShouldBe(4);
+        captured[1].BitIndex.ShouldBe(3);
+    }
+
+    /// <summary>Verifies the JSON keys reach the options.</summary>
+    [Fact]
+    public void Options_parse_from_driver_config_json()
+    {
+        var on = TwinCATDriverFactoryExtensions.ParseOptionsForTests(
+            """{"useSumRead": true, "sumReadMaxItems": 50}""", "d");
+        on.UseSumRead.ShouldBeTrue();
+        on.SumReadMaxItems.ShouldBe(50);
+
+        var off = TwinCATDriverFactoryExtensions.ParseOptionsForTests("{}", "d");
+        off.UseSumRead.ShouldBeFalse();
+        off.SumReadMaxItems.ShouldBe(200);
+    }
+
+    /// <summary>Verifies which overall ADS codes mean "no sum commands here" rather than a comms fault.</summary>
+    [Theory]
+    [InlineData(1792u, true)]
+    [InlineData(1793u, true)]
+    [InlineData(1794u, true)]
+    [InlineData(1795u, true)]
+    [InlineData(1797u, true)]
+    [InlineData(1798u, true)]
+    [InlineData(6u, false)]    // TargetPortNotFound
+    [InlineData(1861u, false)] // ClientSyncTimeOut
+    [InlineData(1808u, false)] // symbol not found: a per-item matter
+    public void Overall_ads_codes_classify_as_refusal_only_for_service_errors(uint code, bool refusal) =>
+        AdsTwinCATClient.IsSumRefusal(code).ShouldBe(refusal);
+
+    private sealed class CapturingClient(List<TwinCATBulkReadItem> sink) : FakeTwinCATClient
+    {
+        public override Task<IReadOnlyList<(object? value, uint status)>> ReadValuesAsync(
+            IReadOnlyList<TwinCATBulkReadItem> reads, CancellationToken ct)
+        {
+            sink.AddRange(reads);
+            return base.ReadValuesAsync(reads, ct);
+        }
+    }
+}

tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/TwinCATDriverPageFormSerializationTests.cs

@@ -72,6 +72,8 @@ public sealed class TwinCATDriverPageFormSerializationTests
             UseNativeNotifications = true,
             EnableControllerBrowse = false,
             NotificationMaxDelayMs = 100,
+            UseSumRead = true,
+            SumReadMaxItems = 64,
             Probe = new TwinCATProbeOptions
             {
                 Enabled = true,
@@ -88,6 +90,8 @@ public sealed class TwinCATDriverPageFormSerializationTests
         roundTripped.UseNativeNotifications.ShouldBeTrue();
         roundTripped.EnableControllerBrowse.ShouldBeFalse();
         roundTripped.NotificationMaxDelayMs.ShouldBe(100);
+        roundTripped.UseSumRead.ShouldBeTrue();
+        roundTripped.SumReadMaxItems.ShouldBe(64);
         roundTripped.Probe.Enabled.ShouldBeTrue();
         roundTripped.Probe.Interval.ShouldBe(TimeSpan.FromSeconds(6));
         roundTripped.Probe.Timeout.ShouldBe(TimeSpan.FromSeconds(2));