Gpt
LLM Wire Format Benchmark: Which Format Can AI Actually Read and Write?
23 comprehension runs across 10 models (Claude Opus/Sonnet/Haiku, GPT-5.5/5.4/5.4-mini, Gemini 2.5 Flash/Pro, Gemini 3.1 Pro, Gemini 3.5 Flash). Generation eval across 11 models and 3 providers (Anthropic, OpenAI, Google). GCF wins 22, ties 1, loses 0 on comprehension. GCF achieves 5/5 valid generation on every frontier model with zero prior training. TOON fails 0/5 on generation with Opus, GPT-5.4, GPT-5.4-mini, Gemini 3.1 Pro, and Gemini 3.1 Flash Lite. JSON breaks on input at 500 symbols.