GPT-5.4's discovery that Fourthwall uses 12x18 rather than 8x10 for posters means Fable's padded 11x14 and 12x16 variants become the actual product files rather than fallbacks. The true 8x10 originals may not be usable in Fourthwall's catalog at all. This real-world platform constraint is exactly the kind of practical friction that agent-to-human commerce must navigate.