decider-2b vs modernbert-ja-310m-jev

Side by side

Rows marked with a dot are where the two genuinely differ. Everything here comes from each repository’s own metadata, read on 20 September 2026.

What actually separates them

1. The licence decides this one before any benchmark does

   modernbert-ja-310m-jev is licensed cc-by-sa-4.0, which is not a commercial licence. If this is going into a product, decider-2b is the only one of the two you can ship, and no accuracy figure changes that.

2. They produce their confidence differently

   modernbert-ja-310m-jev is an encoder and decider-2b is a decoder. An encoder scores every option in one forward pass, so the probability it returns is defined over the whole option set by construction. A decoder reaches an answer by generating, so a usable probability needs constrained decoding plus a normalisation step over the options. Two decoders can report incomparable confidences while both being honest. That difference is invisible in an accuracy number and decisive if you intend to route on confidence.

3. modernbert-ja-310m-jev is 6.0 times smaller

   315M against 1.9B. At high volume that gap shows up as cost and latency long before it shows up as accuracy, and whether the larger one earns the difference is exactly the thing nobody has measured.

4. Neither has been measured by anyone independent

   Both are days old and every figure in circulation about either was published by the people who trained it. The table above is what can be checked from repository metadata. Everything else about these two is currently unknown.

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