Files
histsdk/docs/reverse-engineering/wcf-string-handle-wall.md
T
Joseph Doherty 108220c36b R1.5 GetTagExtendedPropertiesAsync (GetTepByNm) + R1.6 closed (no op)
Ship tag extended-property reads over the 2020 WCF aa/Retr/GetTepByNm op:
HistorianClient.GetTagExtendedPropertiesAsync(tag) -> name/value pairs.

String-handle op reached with the Open2 storage-session GUID formatted
uppercase (same format that unlocked GETRP/GETHI/ExeC). Routed via the
name-based native path (GetTagExtendedPropertiesByName, server-fetch flag),
not the index-based TagQuery path.

Evidence-backed findings from the capture:
- GetTepByNm (and GetTgByNm) succeed with the uppercase handle -- further
  validates the resolved string-handle wall.
- QTB (StartTagQuery) does NOT punch through: captured uppercase, it still
  fails server-side (CMdServer::StartActiveTagnamesQuery over the
  aahMetadataServer pipe) -- a metadata-server blocker, not handle format.
- R1.6 (localized properties) has NO distinct op (only error-message/UI-text
  localization in the managed client); collapses into R1.5. Closed, not throwing.

Wire format (golden-pinned, synthetic bytes -- no dev tag names committed):
- request tagNames = uint count + per-name(uint charCount + UTF-16)
- response = uint tagCount + per-tag(marker + compact-ASCII name +
  uint propCount + per-prop(marker + compact-ASCII name + 0x43 VT_BSTR value)
  + trailer); sequence-paged.

Adds: HistorianTagExtendedProperty model, HistorianTagExtendedPropertyProtocol
(codec), HistorianWcfTagExtendedPropertyClient (orchestration), dialect +
public API; golden WcfTagExtendedPropertyProtocolTests (4) + gated live test
(HISTORIAN_TEP_TAG). Tooling: Capture-TagExtendedProperties.ps1,
decode-tag-properties-capture.py, harness tag-extended-properties scenario.
Docs: wcf-tag-extended-properties.md; roadmap R1.5 DONE / R1.6 collapsed;
wall doc + memory updated with the QTB-server-side nuance. 228 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC
2026-06-20 22:52:07 -04:00

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# The 2020 WCF string-handle wall (2026-06-20)
> ## ✅✅ RESOLVED (2026-06-20): the "wall" was a handle-FORMAT bug, not a registration wall.
>
> The string-handle ops are reachable from the pure-managed client after all. The Open2
> storage-session GUID must be passed as the `string handle` **UPPERCASE, dash-separated,
> no braces** — `storageSessionId.ToString("D").ToUpperInvariant()`. The earlier probes that
> "proved" the wall passed the GUID in .NET's default **lowercase** `ToString("D")`, which the
> server's session table does not match. Live-verified end-to-end against the local 2020 server:
> - **GETRP** (R1.2) → returns the runtime `HistorianVersion` (shipped).
> - **GETHI** (R1.4) → `returned=True`, returns the version buffer (`0C000000` + UTF-16 "20,0,000,000").
> - **ExeC** (R1.1) → `returned=True`, `Retr.GetV` prime + `ExeC("SELECT 1 AS ProbeValue", option=0)`
> yields `queryHandle`, then `GetR(handle, queryHandle, sequence=0)` returns a 1232-byte result =
> a **BinaryFormatter-serialized .NET DataTable** (stream header `…System.Data, Version=4.0.0.0…`).
>
> Probes: gated `StringHandleProbeDiagnosticTests` (GETHI + ExeC). Captures:
> `scripts/Capture-RuntimeParam.ps1`, `scripts/Capture-ExecSql.ps1`. The handle for ExeC/GetR is the
> **same** Open2 storage-session GUID (confirmed = `outBuff[5..21]`). The original analysis below is
> retained for history; treat its "blocked" conclusions as **superseded** — the only missing piece
> was the uppercase format.
>
> **Update 2026-06-20 — R1.5 `GetTepByNm` shipped; QTB nuance.** `GetTagExtendedPropertiesFromName`
> (`GetTepByNm`) is now **shipped + live-verified** with the uppercase handle
> (`GetTagExtendedPropertiesAsync`; see `wcf-tag-extended-properties.md`). It confirms the
> string-handle Retrieval family is reachable (and `GetTgByNm`/GetTagInfosFromName was observed
> succeeding alongside it). **But not every string-handle op is just a format fix:** `QTB`
> (`StartTagQuery`) was captured being sent with a correctly-**uppercase** handle and still failed
> with `error 1` *server-side* (`CMdServer::StartTagQuery::StartActiveTagnamesQuery` over
> `\\.\pipe\aahMetadataServer\console`). So QTB/QTG (the active-tagnames query family) are blocked by
> the metadata server, not the handle format — distinct from the handle-format wall. **R1.6
> (localized properties) has no distinct op** and collapses into R1.5.
---
Live-probing the local **Historian 2020** (WCF, port 32568) for HCAL roadmap M1
surfaced a clean structural boundary on what the pure-managed client can call. It
explains why R1.1/R1.4/R1.5 all fail and identifies the single RE target that
unblocks the rest of the M1 read surface.
> ⚠️ **Superseded — see the RESOLVED banner above.** The boundary below is real *only* when the
> handle is sent lowercase. With the uppercased storage GUID the string-handle ops succeed.
## The dichotomy
Retrieval/Status/History ops split by the **type of their first (handle) parameter**:
| Handle type | Examples | Status on 2020 WCF |
|---|---|---|
| **`uint` client handle** (Open2 output) | `StartQuery2`, `GetNextQueryResultBuffer2`, `IsOriginalAllowed`, `GetTagInfosFromName`/`GetTagInfoFromName` (GetTgByNm), `GetSystemParameter`, `StartEventQuery`, `GetNextEventQueryResultBuffer`, `RegisterTags2`, `EnsureTags2`, `UpdateClientStatus3` | ✅ **work** — the proven read/browse/metadata/status-param/event/write surface |
| **`string` GUID handle** | `ExecuteSqlCommand` (ExeC), `StartTagQuery` (QTB), `QueryTag` (QTG), `GetHistorianInfo` (GETHI), `GetTagExtendedPropertiesFromName` (GetTepByNm), `GetTagInfosFromName2` (GetTgByNm2), `GetTagidsByTagnameAndSource` | ⛔ **blocked** — native error type 4, code **51 (InvalidParameter)** or **1 (Failure)** |
## Evidence (this probe + prior notes)
- **ExeC** → type 4 / code 51 for every handle variant (storageGuid, contextGuid).
Matches `implementation-status.md` ~982 / ~1404 ("StartTagQuery depends on earlier
native session/filter registration … do not wire through guessed calls").
- **GETHI** (`HistorianVersion` param query — the *exact* native request shape from
`BuildGetHistorianInfoRequest`, with `Stat.GetV ×2` priming) → type 4 / code **1**
for all five handle formats tried: storage-session GUID, context GUID, uint as
decimal, uint as `X8` hex, uint as `0x`-hex. In the only place GETHI is used (the
event-priming chain) its result is wrapped in `TryRun` and **discarded**, so there
was never evidence it actually returns data from the managed client.
- **GetTepByNm / QTB / QTG / GetTgByNm2** all take a `string handle` → same family.
## Why
The string-handle ops are keyed off a **native-side session/filter registration**
that the C++ client performs but the managed replay does not reproduce. The uint
client handle is the Open2 session token the server already trusts; the string GUID
handle indexes a *different* per-service registration table that stays empty unless
the native priming is replicated faithfully. `Stat.GetV ×2` alone is insufficient.
## Consequence for the roadmap
Every remaining **M1 read** item is a string-handle op:
- R1.1 `ExecuteSqlCommandAsync` (ExeC) — blocked
- R1.4 `GetHistorianInfoAsync` (GETHI) — blocked
- R1.5 extended-property read (GetTepByNm) — blocked (string handle, confirmed)
- R1.6 localized-property read — same family
So **M1 read-surface completion on 2020 WCF is gated entirely behind one RE target:
the native session/filter registration for string-handle ops.** Reverse-engineer it
once and the whole family unlocks. Until then, the alternatives are:
1. **RE the registration** — instrument the native `CRetrievalConnectionWCF` /
`CStatusConnectionWCF` priming between Open2 and the first successful string-handle
call (capture-tier; the highest-leverage single RE task for M1).
2. **2023 R2 gRPC server** — these ops are first-class on the gRPC front door, where
the handle/envelope differs and the registration wall may not apply.
Do **not** ship any string-handle op via guessed calls (project discipline:
"leave them throwing until evidence supports an implementation").
## ⚠️ Update (2026-06-20): GETRP punches through — the wall is not absolute
Roadmap **R1.2 `GetRuntimeParameterAsync`** turned out to be a **`string`-handle op**
(`aa/Stat/GETRP(string handle, byte[] pRequestBuff) → (bool, byte[] pResponseBuff,
byte[] errorBuffer)`) — the **same shape as GETHI**, and in the same native session it
uses the **same handle GUID** as GETHI (confirmed: the GUID equals the Open2 `outBuff`
storage-session id at `[5..21]`, the value the managed `ParseOpenConnectionResponse`
already extracts as `StorageSessionId`).
Yet GETRP **works from the pure-managed client** — live-verified, returns the runtime
`HistorianVersion` value `20,0,000,000`. The only material difference from the failed
GETHI probe is the **handle string format**: the native client sends the GUID
**UPPERCASE, dash-separated, no braces** (format example
`XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX`, all hex upper), i.e.
`storageSessionId.ToString("D").ToUpperInvariant()`. `.NET Guid.ToString("D")` is
lowercase, so a probe that passed the GUID without upcasing would not byte-match what
the server's session table is keyed on.
**Implication / open lead (not yet retested):** the GETHI/ExeC/QTB/QTG family failures
may be (at least partly) a **handle-format** issue, not (only) a missing native
registration step. The highest-value cheap follow-up is to **re-probe GETHI and ExeC
with the uppercased storage-session GUID** before assuming the registration wall. If
they also return data, the "wall" collapses to a formatting bug and R1.4/R1.5/R1.6/R1.1
may be reachable without any new RE. This has **not** been done yet — do not reclassify
those items until it is. GETRP is shipped because it was directly captured + live-verified
end-to-end; the rest remain `ProtocolEvidenceMissingException`/unprobed until tested.
See `HistorianRuntimeParameterProtocol`, `IStatusServiceContract2.GetRuntimeParameter`,
golden `WcfRuntimeParameterProtocolTests`, and capture tooling
`scripts/Capture-RuntimeParam.ps1` + `scripts/decode-runtime-param-capture.py`.