Junie Can Now Run Entirely on Your Mac – No Credits, No Cloud

Summary

JetBrains has introduced Junie Local, a feature that runs the Junie coding agent entirely on local hardware without cloud dependencies, subscriptions, or credit meters. Users execute a single command inside Junie to download a 4-bit quantized Qwen3.6-27B model, requiring an Apple M5 Mac with 64 GB of RAM. The team prioritized prefill throughput over pure generation speed by utilizing 8-bit arithmetic instructions on the M5 Neural Accelerator, which increased prefill throughput by approximately 40%. Performance optimizations also include KV-cache reuse, speculative decoding to double generation speed, and disabling reasoning to preserve performance. In JetBrains' evaluations, the local configuration performed comparably to cloud-based Sonnet 4.5 on everyday tasks while ensuring source code, diffs, and prompts never leave the local environment.

Takeaways

1. 1

   Junie Local runs a 4-bit Qwen3.6-27B model locally on an Apple M5 Mac with 64 GB of RAM via a single /local command.

2. 2

   Optimizing prefill throughput using the Apple M5 Neural Accelerator's 8-bit arithmetic instructions yielded a 40% performance gain.

3. 3

   JetBrains selected Qwen3.6 over Qwen3.8 because 3.8 required reasoning to operate reliably, which made tasks run roughly four times slower.