Building a full agentic harness around a 4B model is hard

Show HN: Building a full agentic harness around a 4B model is hard

Based, Building a full agentic harness around a 4B model is hard works in show hn launch.

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Around 3 months ago, we were thinking why none of the iPhone apps running an LLM are built as a full harness (as in inference + agentic loop + context management + tools + MCP servers and etc.). It became more interesting when we noticed even the new Siri is not fully on device (and not available in EU for that matter).Having built a few agentic products around a custom harness in the past, we thought this shouldn't be that hard. well, we underestimated how "dumb" a 4B model can be, especially when it comes to tool calling. :DWe tried 8 different models and we settled on Qwen 3.5 4B and we used every trick we knew to make this model behave. well, it works!It's not gonna win in any intelligen

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