Relations are sets — chars returns the distinct character set, so count (chars s) is the distinct-char count, not the string length. That broke nearly every text helper under the current Knot toolchain: - isValidExactHex 64 could never pass (16 distinct hex chars max), so every PubkeyHex/SignatureHex refinement rejected -> all requests 400 - hasPrefix "Bearer " compared take 5 against a 7-char prefix -> all authenticated routes 401 - the 192.168./169.254. SSRF prefixes and all suffix checks never matched - the multi-colon IPv6 check could never see more than one ':' - isValidServerName's length cap was a distinct-char cap Use length for character counts, keep chars only for membership checks, and add countChar for the colon count. Verified with a compiled test covering prefix/suffix/hex/colon/trailing-dot cases.