> Canonical page: https://posttrainllm.com/inspiration/halo

A note of thanks · Scale boundary

# Halo

Halo brings pre-training, SFT, preference work, and RL into one training framework that spans a GPU and clusters. For this lab it is a map of the single-Mac boundary, not a Mac runtime dependency.

01 · The idea

## What stayed with us

HF-native training and portable checkpoints, independent expert/context/tensor/data parallelism, faithful multi-turn trajectories, operation-specific model support, and explicit resume/export/serving boundaries make the single-machine-to-cluster transition inspectable.

02 · The local translation

## What we did with it

Halo informed completed Issues #159, #161 and #162: trajectory export preserves tool actions and observations with per-turn supervision; compatibility reports distinguish static predictions from matching device receipts; artifact lifecycle contracts bind identity, history, runtimes and legal next actions. The 2026-10-02 source-pinned review connects these implementations to the original contracts.

03 · The boundary

## Where the comparison stops

The documented runtime requires NVIDIA/CUDA containers, not MLX or Metal. Halo has not been run on this Mac or adopted as a dependency, and its B300 benchmarks have not been reproduced. Sampled-token RL, asynchronous weight synchronization and distributed training were not implemented locally; its license includes supplemental commercial and attribution terms.

Source trail

## Follow the work

- Original project [Halo source ↗](https://github.com/whitecircle/halo)
- Further reading [White Circle's architecture article ↗](https://whitecircle.com/research/halo)
- Our evidence · partially adopted [Halo / White Circle ↗](https://posttrainllm.com/studies/halo)
- Our context [Source review and completed local adoptions ↗](https://posttrainllm.com/docs/learn/halo/)
- Our context [Our Mac and cluster boundary map ↗](https://posttrainllm.com/docs/learn/mac-mastery-map/)

Independent appreciation. The named projects have not endorsed or affiliated with PostTrainLLM.