DL-483

One file per unary upload, capped at agentmsg.MaxAttachmentBytes = MaxBytes - 1<<20 (15 MiB), checked in the store and mirrored by the agent, with the socket and dev CommsService mount gaining WithReadMaxBytes(siblingServiceMaxReadBytes); on the network door, UploadAttachment, RelayCommsCall and RelaySessionBlob get a body-read deadline of 30 s plus 1 s per 64 KiB of Content-Length (the read cap when unknown), never above 10 minutes, instead of the flat 30 s; an uploader holding 8 unbound uploads from the last 24 hours gets ResourceExhausted (a capability bound, not a quota); an attachment lives as long as its message, nothing is deleted, and GC and erasure of attachments and session blobs are deferred to one follow-up

Status: Active (proposed, pending Matt, 2026-10-11)

Record: ../../agent/compass-comms-file-sharing/design.md#d4-size-cap-and-retention