fetch(new Request(url, { body })) reports requestBytes: 0

[AndresL230]

Summary

estimateRequestBytes (src/core/interceptor.ts:94-106) reads init.body only. When the caller constructs a Request object first and passes it to fetch, the body lives on the Request, not on a separate init argument — the SDK records 0 bytes. Common pattern in undici users and Next.js route handlers.

Fix

When the input is a Request, read input.body or input.headers.get("content-length") (the latter doesn't consume the stream).

Files

• src/core/interceptor.ts
• tests/interceptor.test.ts

Priority

P2 — underreports request bytes for a common modern pattern.