Hacking open-source model behavior with sglang's scoring endpoint, no fine-tuning needed

BLUECOW009 · x · 2026-09-19

Developer skeptrune shows a surprisingly simple inference-engineering trick to make any open-source model behave in a targeted way — demoed with a joke endpoint named deepseek-v4.1-flash-jev.

The core idea: sglang exposes a scoring endpoint (/v1/score) alongside normal generation. In scoring mode, given an input and candidate answers, the model is forced to output a probability distribution over the options instead of streamed text (e.g., "most common letter in abcccde" → (c, 0.9)). Swapping /gen for /v1/score is all it takes.

By engineering over these score distributions, you can cheaply replicate a specific model's behavior style without any fine-tuning. Commenters quip that future models might just ship with a built-in "jev option."

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