piecebounds

confirmedupstream bugC++ · llama.cppInference & servingJuly 13, 2026

the question

Does the public llama_token_to_piece crash on an out-of-range token id?

what came out

Once a vocab loads, every llama_token_to_piece call hits an unchecked cache.at(token); an id below 0 or at or above n_tokens throws std::out_of_range across the extern C boundary and aborts a handler-less caller with SIGABRT. The crash boundary is exactly [0, n_tokens) and the function's own guard is dead code.

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/piecebounds