Sample

Navigate Unicode surrogate asymmetry, UTF-8 BOM rejection, Unicode whitespace rejections, and IEEE 754 negative zero float preservation in the Ruby json gem

sha256:f35dff85940e709eea7e0676276ab4be475c03c3c093131ba97aba4a80221c71

Case

Goal

Navigate Unicode surrogate asymmetry, UTF-8 BOM rejection, Unicode whitespace rejections, and IEEE 754 negative zero float preservation in the Ruby json gem HOW

Packages

json 2.9.1

Environment

ruby

Created

2026-08-17T02:44:01Z

Commonly assumed

JSON.parse validates all escaped Unicode surrogate sequences identically by rejecting any unpaired surrogate with a ParserError.

The sample's author recorded this as what a developer or model would expect here. The contract below is what actually ran.

Contract

• assert JSON.parse accepts lone low surrogates like \uDC00 without raising ParserError, returning an invalid UTF-8 string that fails when passed to JSON.generate, while lone high surrogates like \uD800 raise ParserError immediately
• assert JSON.parse rejects a UTF-8 Byte Order Mark at document start with JSON::ParserError because RFC 8259 forbids BOM signatures in JSON text
• assert JSON.parse strictly rejects Unicode whitespace characters like non-breaking space U+00A0 and zero-width space U+200B outside string tokens
• assert JSON.parse rejects unescaped raw ASCII control characters U+0000 to U+001F in string literals while correctly decoding escaped \u0000 into binary NUL without string truncation
• assert JSON.parse preserves IEEE 754 negative zero float sign from "-0.0" producing -0.0 whose reciprocal evaluates to -Infinity

Files

• Gemfile
• Gemfile.lock
• NOTES.md
• csx.json
• src/unicode_boundary.rb
• test/contract.rb

Download the verified artifact (tar.gz) — the exact bytes the contract ran against

Origin Seeder

csx-seed

Verification receipts

• ruby 3 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · rubygems@1 · 2026-08-17 · ed25519:d91480838ac982c9