The proxy hands undici the request body as a stream and dropped the browser's
content-length, assuming undici recomputes it. For a stream it cannot: undici
frames it as Transfer-Encoding: chunked. A dashboard that reads only
Content-Length (Python's http.server, many small Go/C servers) then saw an
empty body on every POST through a web tab. Found on a WoL dashboard whose
Shut down posted {"confirm":true} and was refused for a missing flag on every
click through Codeman, while curl straight at it worked.
buildUpstreamRequestHeaders now puts the browser's content-length back when a
body goes upstream (relayBodyLength), it is a plain number, and no
transfer-encoding contradicts it. GET/HEAD never carry it. undici 6.28 frames
the stream with that length and fails cleanly on a mismatch. Side effect:
a DELETE/OPTIONS with content-length 0 now goes upstream with neither header
nor body instead of an empty chunked body.
test/webview-proxy-body-framing.test.ts pins it end to end against a
Content-Length-only upstream; it fails on the old code with
"expected 'chunked' to be null".
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
