Apple's free on-device fm paired with decision model Jev beats big-model routing in tests
jasonkneen · x · 2026-09-28
Developer Jason Kneen open-sourced fm-with-jev, a combo splitting cheap decisions from small models:
- fm: Apple's on-device Foundation Model in macOS 27 (/usr/bin/fm) — free, offline, no API key; handles short-text generation like session naming.
- Jev: TypeSafe's decision model on OpenRouter; picks from lists and returns confidence, can't write text.
Test results (Apple Silicon, 2026-09-27):
- Tier routing (haiku/sonnet/opus): fm 9/10, Jev 10/10
- Pick from 20 models: fm only 5/14 with one hang, Jev 14/14
- Tool choice from 40: both 15/15
- Avg decision speed: fm 0.45s vs Jev 0.31s with 0-1 confidence
Takeaway: use fm for titles, Jev for anything involving list selection, fm as offline fallback. A useful pattern for cutting agent costs by keeping big models out of small decisions.
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