SDK

Casual Sheets ships React surfaces for hosts that want to embed the spreadsheet inside their own app — Drive, internal portals, anywhere you have a React tree and want a real .xlsx editor without sending users off-site.

The surfaces are the same shape as Casual Editor’s SDK — the same signing pipeline, the same EmbedTransport, the same iframe envelopes. The only product-specific bit is the field anchor: sheets use { sheet, cell }, editor uses { paraId }.

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What’s published

Sheet doesn’t ship as a public npm package today — @sheet/web is a workspace-internal name. If you’re integrating Casual Sheets into another React app:

• Public deploy users — use the iframe embedding path. One URL, no install.
• Self-hosters embedding into a sibling app — vendor the relevant surfaces (apps/web/src/signing/, apps/web/src/embed/, apps/web/src/file-source/) into your tree, or import from the workspace directly. A first-class npm package is on the roadmap; the wire shapes are already pinned via the iframe protocol contract.

Co-edit topology

Casual Sheets’s co-edit is handled by a dedicated server (apps/server). When you embed the editor into Drive, Drive points at one of two topologies:

• Single-user mode — no co-edit server. Drive bundles the editor; bytes round-trip through Drive’s HTTP API; no Yjs / Hocuspocus runtime.
• Co-edit mode — Drive operator runs apps/server as a second container. The editor opens a WS to it. Initial load + final snapshot still flow through Drive; the WS carries the Yjs deltas in between.

This mirrors Casual Editor’s topology. Operators get a clear cost equation: skip co-edit → simpler deploy; add it → multi-user editing.

Other embedded surfaces

• SigningProvider / SigningPane / capture components — see Signatures.
• EmbedTransport — see Iframe embedding.
• PersonalAuthGate / UserMenu / file-source — same shapes as Casual Editor; covered in Architecture and Customization.

What’s NOT in the SDK surface

• Drive’s chrome — file picker, breadcrumbs, right panel. Those are host responsibilities.
• Authentication. The personal-auth gate is there for the standalone Casual Sheets deploy; Drive integrators replace it with their own.

Source of truth

The integration playbook is mirrored in the sheets repo. When the iframe protocol contract changes in document/docs/internal/13-iframe-protocol.md, both products update in lockstep.