Compatibility coverage and evidence

These changes extend the published 0.13.0 baseline (c7bb2eeff47b9c631c5b0c61020bd9fcc4f699c2) without changing the package version. Existing native snapshots remain evidence only for their recorded operations. New verification was run in Linux; it includes no new Windows Office save/reopen validation.

Format/version	Operation	New behavior	Verification	Remaining boundary
CFB v3 rebuild	List, edit and rebuild directory metadata; repair	Exact unsigned FILETIME ticks survive instead of losing sub-millisecond precision; pre-1970 dates floor correctly	Zero, pre-epoch, sub-ms and maximum ticks; timestamp edits and invalid-range refusals; strict parser and packed consumer	Rebuild remains v3; this does not expand v4 writes or directory-name normalization
XLS BIFF8	Replace existing RK/MULRK with a finite value outside RK encoding	Promote to exact IEEE NUMBER, splitting packed siblings and checking BOUNDSHEET/INDEX/DBCELL relocation	Native-generated RK/MULRK inputs; raw sibling/XF preservation; independent xlrd values/types/styles comparison; mixed retained handles and malformed pointer refusals	No native Excel acceptance of these new outputs; no formula execution or unchecked pointer relocation; explicit cell creation is bounded as described below
DOC Word 97 binary	Same-length paragraph edit and supported paragraph growth	Refuse multi-paragraph field overlap even on the same-length fast path; validate section CP bounds and table aliases before growth	Derivative of an existing historical Word fixture (origin unverified), byte-preserving failure checks, valid growth followed by same-length edit	Bookmark growth stays refused; table structure and arbitrary feature-table relocation remain unsupported
PPT 97–2003	Read active slide text; replace fixed-length text	Bounded record/text/slide reads and refusal of missing, malformed or shared TextHeader ownership	Native-supported existing edit suites plus authored ownership and resource-limit cases; packed consumer type check	Text growth, absent-run creation and arbitrary ownership reconstruction remain unsupported
VSD v11	Inspect explicit geometry	Read per-header section flags and stored MoveTo/LineTo/ArcTo operands through immutable model snapshots	Compressed/uncompressed authored records, owner/sibling isolation, malformed operands; existing native fixture hidden-section and rectangle values	ArcTo and multiple-section coverage is authored; physical order only, no list-order/formula/inheritance evaluation, guides or geometry writes

The increment retains compatibility APIs and opaque streams. Refused edits return the original bytes or throw the model's explicit unsupported-edit error without committing state. Synthetic self-roundtrips and independent parser agreement do not establish native parity.

Run npm run typecheck, npm test, npm run build and npm run test:package from the repository. The packed check installs a tarball in an isolated temporary consumer and compiles readonly/type-checked API use; it does not publish anything.

Verification

• TypeScript typecheck and build passed.
• Full Vitest suite: 81 files, 835 tests passed.
• Packed-package runtime and TypeScript consumer checks passed.
• git diff --check passed.
• xlrd 2.0.1 independently read promoted copies of workbook-mulrk.xls (25 slots, one sheet) and workbook-features.xls (4,388 slots, four sheets): exact PI target and unchanged remaining values, cell types and XF indices. scripts/check-xls-numeric-promotion.py reproduces this check when xlrd is already installed; it adds no package runtime dependency.
• Independent code review covered all five lanes and found no confirmed corruption or type-safety blocker.

Additional bounded operations

Explicit cell creation and geometry inspection retain the existing unsupported write boundaries.

Format/version	Operation	Additional behavior	Evidence and limits
XLS BIFF8	Explicit absent numeric-cell creation	sheet.createNumericCell(row, col, value, xf) creates a NUMBER after a verified numeric predecessor in an existing nonempty ROW/DBCELL block; ROW column extent and stream pointers update; returns a stable editable handle	Requires a selected existing cell XF and existing DIMENSIONS extent; refuses new rows, before-first placement, existing physical cells, merged/formula ranges, unsupported pointers and malformed blocks. Native-generated inputs and independent xlrd output checks; fresh native Excel save/reopen remains pending
VSD v11	Stored Ellipse inspection	Geometry section rows include six readonly Ellipse operands: center, left and top points	Primary libvisio layout reference and compressed/uncompressed authored regressions, including truncation/nonfinite data. Native Ellipse acceptance is unverified; guide ownership and geometry writes stay refused
DOC Word 97 binary	Equal-length paragraph replacement	Refuses text pieces overlapping the FIB or referenced CHPX/PAPX pages; bounds formatting descriptor allocation	Malformed derivatives of the existing historical input and unchanged valid same-length edit behavior across four existing fixtures. No new bookmark support or native Word acceptance claim

The existing DOC corpus has empty bookmark tables in all seven inspected fixtures. Bookmark-aware growth remains refused until its structures and native acceptance can be verified. VSD guide ownership likewise lacks a verified corpus/model and remains refused.

Independent creation evidence

xlrd 2.0.1 read created copies of the existing Excel-generated fixtures: workbook-mulrk.xls at row 3/column 2/XF 62 (25 cell slots), and workbook-features.xls separately at row 2/column 6 and row 3/column 3/XF 15 (4,388 slots in each copy). In each case the originally absent cell reads as PI/NUMBER with the selected XF; all other values, cell types, XF indices, sheet order and dimensions match the input. Reproduce with scripts/check-xls-numeric-promotion.py ORIGINAL EDITED ROW COL --created --xf XF. No application native acceptance is implied.

Independent review also verified the final malformed-cell-order regression against the actual fixture records and passed all 23 creation tests. Creation checks enforce 64 MiB input and 100,000-record budgets before building the physical record model. Combined packed consumers exercise creation, subsequent value edits, retained existing handles, duplicate-creation refusal and readonly Ellipse types.

Fixture provenance follows test/fixtures/NATIVE-VALIDATION.md: historical DOC/PPT origins remain unverified; repository-owned native-generated fixtures are distinguished from those historical inputs. No new external historical fixture was added.

Bookmark admission boundary

Bookmark-dependent growth remains refused after independent layout and architecture review. The prerequisites report records the pairing, duplicate-order, sentinel, selection and allocation rules, the seven-fixture audit, and the required native fixture/snapshot evidence. Two new authored in-memory regressions on an owned Word fixture verify growth refusal before/after a bookmark, clean and dirty model atomicity, stable handles and byte-identical table preservation during an allowed same-length edit. This does not admit bookmark relocation or establish native acceptance.

The captured runtime coverage includes exact CFB timestamps, checked XLS numeric promotion and explicit bounded cell creation, DOC field and structural safeguards, bounded PPT text/ownership checks, and stored VSD ArcTo/Ellipse/section inspection. No package release is implied by integrating these source changes.