A Java oracle builds vanilla's real Brigadier command tree with the loaded registries and data-pack tags, exports the tree, and parses a corpus of command strings. The corpus is generated by walking that tree with valid and invalid samples for every argument type plus hand-written edge cases. A Rust example parses the same corpus with Horizon's dispatcher and the Python driver compares success, exact error text and cursor, and end-of-input completion suggestions, with tree-diff and mismatch summary helpers. Currently 79 percent of 39685 inputs match at permission level 4. Entity selector errors now rewind to the start of the input like vanilla.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Ludovic Marie