CSV, TSV and any single-byte ASCII separator, and XLSX and ODS workbooks, read by a native Rust core into typed column batches. The core owns no memory: this gem allocates the buffers once and the core fills them in one native call per batch. Every cell is a HyperCast verdict — the value, or a reason plus the offending span — and a file that is not rows of cells at all is an exception raised after the intact rows. Two backends behind one surface, selected automatically and both shipped prebuilt: a Magnus extension where a precompiled platform gem matches, and stdlib Fiddle everywhere else. No compile on install.