A spreadsheet engine,
cut for .NET.
Tessera 2026.8.0-alpha.1 is a release candidate for the private-evaluation channel: spreadsheets and the shared Open XML packaging they sit on, built from one verified source revision.
A broad workbook model, under test.
Reading, writing, formulas, streaming, and the spreadsheet formats share hardened Open XML packaging infrastructure.
Streaming read
Process XLSX rows forward-only while retaining workbook structure and shared-string metadata in memory.
Streaming write
Emit XLSX rows without constructing the complete in-memory worksheet model.
Formula engine
Evaluates the workbook in-process - references, ranges, and the common function set, no Excel required.
Allocation-conscious paths
Span-based internals and streaming APIs reduce per-row work; shared strings and workbook metadata still consume memory.
Open XML packages
Reads and writes styles, shared strings, content types, and relationships without Office interop.
Object mapping
Write rows from annotated objects through a source generator, without reflection on the generated path.
What 2026.8.0-alpha.1 actually contains
Taken from the checksummed release manifest, not from a roadmap.
Modern .NET, no Office install
No native dependency, no COM interop, no Excel install. Just the runtime.
Cut spreadsheets like stone.
Tessera 2026.8.0-alpha.1 is a release candidate on the private-evaluation channel. The packages are built and checksummed but not published, so there is nothing to restore yet. Read the format boundaries and known limitations first.