/envelope/ — returns 413 via Axum's body-limit middleware:

• relay-server/src/endpoints/envelope.rs#L128 —post(handle).route_layer(DefaultBodyLimit::max(config.max_envelope_size())). Oversize is rejected before the handler, so Axum returns the standard 413.

/minidump/ — multipart bypasses the body-limit layer and reports oversize as 400:

• relay-server/src/endpoints/minidump.rs#L264 — multipart path: utils::multipart_from_request(request, state.config().max_attachments_size())
• relay-server/src/endpoints/minidump.rs#L288 — raw-minidump path still uses DefaultBodyLimit::max(config.max_attachment_size()) (this one would return 413)
• relay-server/src/utils/multipart.rs#L283-L288 — limit enforced via multer::Constraints::new().size_limit(...)
• relay-server/src/utils/multipart.rs#L241 — on exceed: return Err(multer::Error::StreamSizeExceeded { ... })

Status-code mapping — the multer error becomes 400, not 413:

• relay-server/src/endpoints/common.rs#L62 — InvalidMultipart(#[from] multer::Error)
• relay-server/src/endpoints/common.rs#L136 — only BadStoreRequest::Overflow maps to PAYLOAD_TOO_LARGE
• relay-server/src/endpoints/common.rs#L140 — everything else, including InvalidMultipart(StreamSizeExceeded), falls through to BAD_REQUEST