prefixkey

confirmedupstream bugC++Inference & servingJuly 13, 2026

the question

Does the additionalProperties key grammar reject valid keys that are proper prefixes of a defined property name?

what came out

_not_strings emits the stop-here epsilon only at the trie root, so an interior node that is a proper prefix of a defined property name has no accepting derivation. With schema property "ab" and additionalProperties true, the valid key "a" is rejected. Over 889 exhaustive cases: 10 under-generation mismatches, 0 over-generation, all prefixes.

method & receipts

Result: confirmed
Pre-registered — the prediction was written down and committed before the run.
Reproducible — one script re-runs the whole thing from scratch.
Tested — a correctness/benchmark suite ships alongside the code.

→ read the code and re-run it

github.com/v-code01/prefixkey