---
license: mit
base_model: microsoft/FastContext-1.0-4B-SFT
pipeline_tag: text-generation
tags:
- core-ai
- coreml
- on-device
- ios
- iphone
- qwen3
language:
- en
---

# FastContext-1.0-4B-SFT — Core AI (on-device, iPhone)

[microsoft/FastContext-1.0-4B-SFT](https://huggingface.co/microsoft/FastContext-1.0-4B-SFT)
converted to Apple **Core AI** for on-device inference, served by the **CoreAIChat** app.

FastContext is a long-context **repository-exploration agent** (Qwen3-4B-Instruct
backbone, supervised-fine-tuned on exploration traces: broad first-turn search,
multi-turn evidence gathering, and precise file:line citation generation).

## Contents
- `gpu/` — AOT-compiled **GPU (MPSGraph)** bundle, 4-bit linear-INT4, **h18p**
  (iPhone 17 / iPhone 18 class). ~2.1 GB. Drop-in for CoreAIChat's
  `Documents/models/fastcontext_4b_gpu`.

> **Device class:** this is an **AOT h18p** bundle (iPhone 17 / 18 class). On-device
> specialization of a 4B graph is not viable, so the bundle is precompiled for the
> h18p GPU — the same approach Core AI uses for the Gemma-4B bundle.

## Verified on iPhone 17 Pro (iOS 27)
- **Parity** vs HF fp16 (teacher-forced): **23/24 argmax**, perplexity 1.41 — the
  single flip is a near-tie quant-noise position.
- **On-device GPU:** ~**334 tok/s** prefill, ~**16.5 tok/s** decode (512-prompt /
  1024-gen), load ~8 s cold, ~0.3 GB resident (weights memory-mapped).

## Use
Install **CoreAIChat**, open the model picker, and select **FastContext 4B**.

## License
MIT, inherited from the base model
[microsoft/FastContext-1.0-4B-SFT](https://huggingface.co/microsoft/FastContext-1.0-4B-SFT).
See `LICENSE`.