The determine_body_strategy function only matched two case variants of Transfer-Encoding and Content-Length headers. HTTP headers are case-insensitive per RFC 7230 §3.2, so servers sending differently cased headers (e.g. CONTENT-LENGTH) would cause incorrect body reading strategy (falling through to ReadUntilClose). Extract a header_value() helper that does case-insensitive name matching via eq_ignore_ascii_case. Add tests for mixed-case headers. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>