D270 — Assets above 10 MiB are not versioned, and the asset listing survives stray files

Decision. kb.AssetMaxFileSize is a fixed 10 MiB and means "the largest file still worth versioning in the KB's git history": asset_write refuses a larger file, asset_read will not return one. ListAssets never fails on a file it can describe: hidden files and directories are skipped (they are not assets), and a file above the cap is listed with oversized: true, hashed by streaming, and stays deletable. Lint reports it as oversized_asset (warning); an owner whose assets cannot be listed at all is one unlistable_assets finding, not an aborted run. concept_collapse refuses when the directory holds anything besides index.md.

Why. The old 1 MiB cap was a transport budget, and it was enforced on list as well as write. Assets reach a KB through git too — a push, an import — so one 2 MiB PDF or a .DS_Store in any expanded concept made lint fail on the whole KB and left the file impossible to list or delete through the API. The stdio transport decodes with json.Decoder and has no per-line cap, so the size limit is free to express a storage policy instead. The cost: an agent can now move 10 MiB (about 13 MiB of base64) in a single call.

Alternatives rejected. - A configurable cap (per server or per KB): one more knob for a value nobody has needed to tune; a constant can become a setting later without changing the contract. - Git LFS for large assets: adds a server and client dependency for a KB that is meant to hold text and small evidence. - Keeping the listing strict and fixing only lint: concept_delete and concept_collapse depend on the same listing and would still be blocked by one file.

Consequences. Path-safety rules on API input are unchanged: a hidden, escaping, .md or symlinked path is still refused by read, write and delete. A symlink or special file inside an expanded concept still makes ListAssets fail — deliberately, since it is not safe to describe — and lint turns that into a finding. Files larger than the cap are expected to live outside the KB and be cited by link.