Continued pretraining destroyed a 2.6B model's native tool-call format, and its author published the numbers anyway
AspireAI community · arXiv
Saidzoda-Tajik-LFM-2.6B adapts the 2.6B-parameter hybrid LFM2.5-2.6B-Base to Tajik tool calling on modest hardware, using LoRA continued pretraining on 1,485,319 cleaned Tajik web documents for three epochs, then one epoch of supervised fine-tuning on machine-translated Tajik tool calls with English calls kept as replay. On a 174-item tool-calling test set built from BFCL v3 and machine-translated, strict full-call accuracy on Tajik rose from 20.69 to 64.14, a paired difference of +43.45 points with a 95 percent interval of +35.2 to +51.7, while English showed no detectable change at 76.55 and 77.24. The interesting part is the negative result: every continued-pretraining checkpoint scored zero, because CPT removed the native tool-call format and part of the skill itself. The author is explicit about the limits: it is not a general Tajik assistant, it almost never declines when no tool fits (6.9 percent correct against 31.0 percent for the base under a lenient parser), it is weak at multi-turn calls, and its calls should be checked before execution. Tajik knowledge accuracy rose from 28.0 to 35.0, Belebele Tajik did not change significantly, and English MMLU fell from 60.8 to 52.5.
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