Choose a model

Picking an on-device model used to mean juggling parameter counts, quantization levels, and RAM tables. The model picker on the Community Hub now does that work for you: tell it which device you use, and it shows what actually runs well on it. This guide shows how to use the picker and explains the reasoning behind its recommendations — including why they look conservative.

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Set your device once

When you pick a model while building an Agent or a Scribe Agent, the picker asks which device you use — iPhone, iPad, or Mac. Every recommendation then tailors to it:

• Each model shows how much RAM it needs and a fits your device badge. Models that fit float to the top; ones that don’t are dimmed.
• LLMs and VLMs live in one unified list — no tab-hopping.
• Start typing to search Hugging Face directly. Results show the organization, task, license, and usage stats inline, and carry the same Runs / Needs X GB badge as the curated models.

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What the badge guarantees

The RAM number next to a model means runs well, not barely loads. A model that fits your device is guaranteed three things:

• A full 8K-token context window — enough working memory to get through a real session.
• The model runs solo — Isa never stacks multiple models in memory at once.
• Headroom for the operating system — enough margin that iOS won’t force-quit Isa mid-session.

The last one surprises people: an “8 GB” iPhone gives an app only about 4.8 GB of usable memory before iOS starts force-quitting it. The picker budgets against what’s actually available, not the number on the box.

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Why the recommendations look conservative

You might see a ~3 GB model asking for a 12 GB iPhone and think something’s off. It’s not — the context window drives the RAM number, not the weights. Here is the same model, Qwen 3.5 4B (about 3 GB on disk), under three different context guarantees: The weights stay the same size; what grows is the model’s working memory — every extra token of context needs more RAM to keep track of. The picker guarantees 8K tokens because that’s what a real session needs. Promising 2K would make the requirements look friendlier, but a longer consultation would run out of memory and crash mid-visit. That’s the philosophy behind the picker: the best model is the one that runs well on your device — fast and reliable — not the biggest one that technically loads.

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What fits which device

The picker is the source of truth — set your device and read the badges. As a rough map of where things land today: iPads and Apple Silicon Macs ship with more RAM — 16 GB and up is common — so larger variants and longer context windows fit there. The picker covers the latest iPhones, iPads, and Macs.

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If nothing fits

If your device can’t run the model you need, there are two ways out:

• Move the Primary Agent to the cloud. A cloud model doesn’t consume device RAM — you bring your own API key, and data leaves the device. See On-device vs. cloud.
• Use Isa on a Mac. Macs have the most usable memory of the supported devices — see Hardware requirements.

Agents remain on-device only, so they always need a model that fits.

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