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logprobcost

mixedPython · llama.cppInference & servingJuly 6, 2026

the question

What does requesting token logprobs cost per token, and does asking for more cost more?

what came out

A fixed per-token overhead -- +6% (1.5B), +10% (0.5B) -- that does NOT grow with k (that prediction was falsified): once you pay for any logprobs, asking for more is nearly free. Exact server timing.

method & receipts

  • Result: mixed
  • Pre-registered the prediction was written down and committed before the run.
  • Reproducible one script re-runs the whole thing from scratch.
  • Independently reviewed an adversarial review pass, kept in the repo.
  • Machine-readable claims every reported number, in a checkable file.
  • Tested — a correctness/benchmark suite ships alongside the code.

→ read the code and re-run it

github.com/v-code01/logprobcost