Adds user-defined extended properties to an existing tag via the 2020 WCF
AddTEx (AddTagExtendedProperties) op. Write-enabled connection + uppercase
storage-session GUID handle; reuses the write orchestrator open/priming chain.
The AddTEx inBuff is the exact inverse of the R1.5 GetTepByNm read-response
framing, so the serializer mirrors the read parser:
uint32 groupCount + 0x01(group) + [0x09+u16+ASCII tag] + uint32 propCount
+ per prop{ 0x02 + [0x09+u16+ASCII name] + 0x43 VT_BSTR + u16 payloadLen
+ u16 charCount + UTF-16 value } + 0x01(group trailer) + 0x00(terminator).
The trailing 0x00 is required — without it inBuff is one byte short and the
server throws SErrorException in CHistStorage::AddTagExtendedProperties. The
golden fixture pins the clean inBuff the live server accepted (dumped via
AVEVA_HISTORIAN_TEP_DUMP); read-back verified via R1.5. String (0x43) values only.
Delete (DelTep) is deferred: the native DeleteTagExtendedPropertiesByName does a
client-side sync check and returns err 229 for a just-added property, so the
DelTep request never reaches the wire and its inBuff can't be captured yet.
Shipped: HistorianClient.AddTagExtendedPropertiesAsync/AddTagExtendedPropertyAsync;
HistorianTagExtendedPropertyProtocol.SerializeAddRequest; orchestrator path;
golden WcfTagExtendedPropertyWriteProtocolTests (4); gated live write/read-back test;
native-harness `add-tep` scenario + Capture-AddTagExtendedProperties.ps1 +
decode-add-tep-capture.py. Doc: wcf-add-tag-extended-properties.md. 233 tests green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B6mcaT2PjRFKcogzp9UkfC
Joseph Doherty