CR-2026-132 — Folder Upload: Restore + Structure Preservation — v0_1

Version. 0.1 Date. 2026-07-02 Status. Drafted, not staged for build. Number 132 confirmed free at staging (highest prior: CR-2026-131). Base: engine main @ 1afc723 (post-CR-2026-130 merge); OL main @ 4566233 (post-CR-2026-130 merge, Operator Layer). No build yet. Grounded on: CC Step-0 diagnosis 2026-07-02 (read-only, both repos at current main). Repos: loomworks (composer, uploads.ts, types.ts, UploadResultCard) + loomworks-engine (uploads.py, upload_event.py).

What this fixes

1. Folder-upload button regressed. In-engagement composer lost its folder picker during a 2026-06-26 mockup rewrite. Restore by pointing the composer's attach control at UploadAttachmentButton (already live and correct in ChatView.tsx). Near-zero-risk, mechanical, frontend-only.

1. Folder structure is dropped on upload. Client sends basename only; relative_path is stubbed to filename. Fix:

• Send webkitRelativePath from the client (Starlette already preserves / in multipart filenames — verified, no engine parsing change needed).
• Engine: split the single filename variable into basename (for original_filename/source_artifact_filename) and the full path (for relative_path). No schema change — relative_path field already exists.
• Lone-file-in-folder fix: a folder containing exactly one file currently collapses to the single-file response shape and drops folder_manifest. Fix so an explicit folder selection always preserves folder_manifest, even for one file.
• Display: relative_path is typed on the frontend but rendered nowhere. Add minimal display of the relative path per file in UploadResultCard (or equivalent), so preserved structure is visible to the Operator, not just stored.

No path-traversal risk

put_blob always uses a generated storage key, never the client-supplied path. The path is metadata only.

Seed check

No seed commitment on folder structure — specification-level, not seed-level. No conflict. Restoring the button aligns with "only show what is available" (the button vanishing was a rebuild casualty, not a deliberate absence).

Out of scope

No new upload types, no change to interpretation/description pipeline (CR-130/131 territory, already shipped).