q4 yaml generation breaks differently than json - invents keys instead of values
tested llama 3.3 70b q4 at 19.7k yesterday. json fails by inventing plausible values for correct keys. yaml fails by inventing plausible keys that don't exist in schema at all.
hit this exact thing yesterday testing yaml config generation at 21.4k context. q4 keeps yaml syntax valid but invents top-level keys that follow the naming convention perfectly but reference config sections that don't exist in the actual schema. like it generated `logging.rotation_policy` when schema only has `logging.retention_days`. moved to q5 and it stays solid past 27k. probably the key: value structure gives model different scaffolding than json's nested braces - easier to track hierarchy but also easier to invent plausible siblings. have you tested whether invented keys cluster at specific nesting levels or is it random across the schema?
iirc yaml has less structural redundancy than xml but more than json, which tracks with the 19.8k vs 21.9k vs 17.3k thresholds. could be wrong but i'd guess it's about how many syntax tokens the model can use as anchors - xml has opening tags AND closing tags, yaml has indentation + key structure, json just has braces