R1.4 GetHistorianInfo: bounded out on 2020 WCF (named-value-only, no struct)

Captured the native HistorianAccess.GetHistorianInfo(out HistorianInfo, out err)
and decoded the wire: over 2020 WCF, GETHI is a named-value query whose only
working key is "HistorianVersion" (response ~30 bytes = the version string).
Probed 7 storage-mode key names -> all ok=False/err. The 518-byte HISTORIAN_INFO
struct + EventStorageMode@514 is the 2023R2 HCAL-native/gRPC model (confirmed
from the decompiled 2023R2 source); on 2020 the native client derives the mode
outside the WCF wire.

Version is already exposed (ProbeAsync/GetRuntimeParameterAsync), so no hollow
GetHistorianInfoAsync is shipped (same disposition as R1.3 timezone). This
completes the reachable 2020-WCF M1 read surface; remaining M1 = config writes
(gated on explicit request) or gRPC/2023R2-only items.

RE aids kept: harness `historian-info` scenario, Capture-HistorianInfo.ps1,
decode-historian-info-capture.py, and StringHandleProbeDiagnosticTests
.GETHI_CandidateInfoNames (asserts the named-value-only finding; gated).
Docs: wcf-historian-info.md (new) + roadmap/matrix/wall-doc updates. 230 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC

docs/reverse-engineering/wcf-historian-info.md

@@ -0,0 +1,68 @@
+# GetHistorianInfo over 2020 WCF — GETHI is named-value-only (HCAL R1.4)
+
+**Status: ⚠ Bounded out on 2020 WCF (2026-06-20).** `GetHistorianInfoAsync` is **not shipped**:
+the one field that motivates it — `EventStorageMode` — is **not on the 2020 WCF wire**. The
+version field that GETHI *does* return over WCF is already exposed (`ProbeAsync`,
+`GetRuntimeParameterAsync("HistorianVersion")`), so there is nothing new to ship here without a
+2023 R2 gRPC server. This parallels R1.3 (`GetServerTimeZone`), which is likewise 2023R2-only.
+
+## What the capture showed
+
+`scripts/Capture-HistorianInfo.ps1` drives the native `HistorianAccess.GetHistorianInfo(out
+HistorianInfo, out error)` through the instrumented (`instrument-wcf-{write,read}message`)
+`current/aahClientManaged.dll`. The native call **succeeds** and returns
+`EventStorageMode = Blocks`, `ServerVersion = 20,0,000,000`, no error.
+
+But the wire tells a different story (`scripts/decode-historian-info-capture.py`):
+
+- The only `GETHI` op on the wire is **`aa/Stat/GETHI(handle, pRequestBuff)`** with
+  `pRequestBuff = 53 67 02 00` (sig `0x6753` + version `2`) `+ uint charCount(16) + UTF-16
+  "HistorianVersion"` — i.e. the **named-value request**, identical to the GETRP/version shape.
+- Its response `pResponseBuff` is **~30 bytes**: `uint charCount(12) + UTF-16 "20,0,000,000"`
+  (+ a `02 00 01 00` trailer). **Just the version** — not a 518-byte struct.
+- The post-GETHI ops in the same capture are `Hist/UpdC3` + a run of `Stat/GetSystemParameter`
+  (`AllowOriginals`, `HistorianPartner`, `HistorianVersion`, `MaxCyclicStorageTimeout`,
+  `RealTimeWindow`, `FutureTimeThreshold`, `AllowRenameTags`). **None carries a storage-mode
+  value.** So the native wrapper's `EventStorageMode` is derived by the C++ HCAL **outside the
+  WCF wire**, not fetched over it.
+
+## Probe: does GETHI expose storage mode under any name?
+
+`StringHandleProbeDiagnosticTests.GETHI_CandidateInfoNames_AgainstLocalHistorian` (gated on
+`HISTORIAN_HOST=localhost`) issues GETHI for `HistorianVersion` plus seven storage-mode name
+guesses. Result on the live 2020 server:
+
+| GETHI parameter name | result |
+|---|---|
+| `HistorianVersion` | **ok=True**, respLen=32 (version) |
+| `EventStorageMode`, `EventStorageType`, `StorageType`, `HistorianEventStorageMode`, `EventStorage`, `StorageMode`, `HistorianInfo` | **ok=False**, errLen=5, empty |
+
+So GETHI on 2020 WCF is a strict named-value lookup with exactly one known-good key
+(`HistorianVersion`). There is no storage-mode key, no full-struct request.
+
+## Why the 518-byte struct doesn't apply here
+
+The 2023 R2 decompiled `ArchestrA.HistorianAccess.GetHistorianInfo` (analysis folder) allocates
+a **518-byte `HISTORIAN_INFO`** struct, pre-inits `int32 @514` to `-1`, calls native HCAL
+(vtable+648) which fills it, then reads version (UTF-16 @0) + `EventStorageMode` (`@514`:
+`-1`=Unsupported, `0`=Database, else=Blocks). That is the **HCAL-native / 2023R2 gRPC**
+front-door model (`StatusService.GetHistorianInfo` returns `bytes btHistorianInfo`). On **2020
+WCF** that struct is never marshaled across the wire — only the version named-value is. The
+native client's `EventStorageMode` therefore comes from C++-internal state the managed WCF
+replay cannot observe or reproduce.
+
+## Conclusion / where it lands
+
+- **2020 WCF:** `GetHistorianInfoAsync` would add nothing over existing surface (version only) and
+  could not report a real `EventStorageMode` — so it is intentionally **not shipped** (no hollow
+  `Unsupported`-returning API; project discipline: don't ship misleading behavior).
+- **2023 R2 gRPC:** `Status.GetHistorianInfo` returns the full 518-byte `btHistorianInfo`; decode
+  version@0 + `EventStorageMode`@514 there. Build + verify against a live 2023 R2 server. The
+  `HistorianInfo` / `HistorianEventStorageMode` public types should land alongside that path.
+
+## Tooling kept as RE aids
+
+- `tools/AVEVA.Historian.NativeTraceHarness` `historian-info` scenario (drives the native call).
+- `scripts/Capture-HistorianInfo.ps1` + `scripts/decode-historian-info-capture.py`.
+- `StringHandleProbeDiagnosticTests.GETHI_CandidateInfoNames_AgainstLocalHistorian` (locks the
+  named-value-only finding; gated).

docs/reverse-engineering/wcf-string-handle-wall.md

@@ -111,7 +111,11 @@ GETHI and **ExeC both return data with the uppercased storage-session GUID**.
   read-only with `System.Formats.Nrbf` + `XDocument` (BinaryFormatter is gone from .NET 10).
   Shipped: `HistorianSqlResultProtocol`, `HistorianWcfSqlClient`, golden `WcfSqlResultProtocolTests`,
   gated live tests. See `docs/reverse-engineering/wcf-exec-sql.md`.
-- **GETHI (R1.4)** also returns data with the uppercase handle (probe; public API not yet shipped).
+- **GETHI (R1.4)** returns data with the uppercase handle, **but only the named `HistorianVersion`
+  value** — over 2020 WCF GETHI is a named-value query (the only working key), *not* a full-struct
+  read. `EventStorageMode` (the 518-byte-struct `@514` field) is **not on the 2020 WCF wire**; it is
+  the 2023R2 HCAL-native/gRPC model. So R1.4 is **bounded out on WCF / gRPC-2023R2-only** and the
+  public API is intentionally not shipped. Full analysis: `docs/reverse-engineering/wcf-historian-info.md`.
 
 So the "wall" collapses to the handle **format** for the Retrieval/Status string-handle ops.
 **Exception — QTB/QTG:** `StartTagQuery` does *not* punch through; captured with a correctly