homelab-frontend/tasks/1.7-body-size-caps.md

1.7 — Per-route body size caps (GREEN)

Phase: 1 — Proxy core Stage: RED Depends on: 0.2, 1.1

• Each route enforces its own configured maximum request body size
• A body over the cap is rejected with 413 and a body the upstream never sees
• Rejection happens while reading, not after buffering the whole body into memory
• A request with a lying or absent Content-Length is still capped by bytes actually read
• A body at exactly the cap is accepted and proxied intact
• The rejection is logged with a reason distinguishing it from other rejections
• No global default cap silently applies to a route that failed to declare one — that is a config error, per 0.2

nginx in front is configured with proxy-body-size: 0, meaning it enforces no limit at all, so the gateway is the only place a cap exists. Embedding and rerank callers can send large batches legitimately, which is why the cap is per route rather than one number for the whole surface.

Verify

go test ./internal/proxy/... -run TestBodySizeCap -v
# expected: passes — a body one byte over the route cap returns 413 and the stub
# upstream records zero requests; a body exactly at the cap returns the stub's 200