- HistoryModifiedValue gains explicit SourceTimeUtc (SqlServer + QuestDB populate it); the node manager's resume cursor uses it instead of the prior value's nullable source timestamp (MinValue for inserts).
- ACL test now uses a trail-returning data source and asserts Good + data on the allow leg.
- Node-manager tests: end-only backward open-ended paging, reverse resume cursor, null-prior cursor.
- QuestDB updater logs a Warning (tag + time range) when a sample write fails after its trail rows landed.
- docs/Historian.md: rolling-upgrade window, IDENTITY-vs-commit ordering, QuestDB cross-node ModifiedId clock ordering.
Every HistoryUpdate a SQL backend applies now leaves a modification trail
(prior value, principal, Part 11 update type, modification time), and
HistoryReadRaw with IsReadModified=true serves it as HistoryModifiedData.
- Core: HistoryUpdateContext threaded into all three IHistorianDataUpdater
methods; IHistorianDataSource.ReadModifiedAsync (default NotSupported =>
BadHistoryOperationUnsupported on Gateway/Null); HistoryModified* contracts.
- SqlServer: schema v2 (002_sample_modified.sql, RequiredVersion=2, docs copy);
trail written by OUTPUT ... INTO on the same MERGE/DELETE statement, so a
failed update leaves no audit row; retention purges SampleModified per tag on
the source-time cutoff; ReadModifiedAsync keyed on (SourceTimeUtc, ModifiedId).
- QuestDB: append-only {prefix}sample_modified (TTL like samples), trail row
written BEFORE the change (orphan-on-crash, never an untracked change);
existence reads now carry the prior value; ReadModifiedAsync.
- Node manager: modified reads dispatch + page via the #669 continuation store
(HistoryContinuationState gains HistoryCursorKind + LastModifiedId), gated by
the existing HistoryRead decision; session principal / key id passed to the
updater. IsDeleteModified stays unsupported.
- Client.CLI: historyread --modified.
- Tests: node-manager dispatch/paging/cursor binding/principal threading,
over-the-wire HistoryModifiedData, shared ModifiedValueConformance on both
backends, SqlServer atomicity (forced trail failure => no change) + v1->v2
upgrade + retention trail purge.
- Docs: Historian.md (Modified-value history section, schema v2 upgrade note),
security.md, Client.CLI.md, CLAUDE.md.
Joseph Doherty