OpenMythos vs SAM 3.1

OpenMythos is a community-driven theoretical reconstruction of Claude Mythos's suspected architecture, implementing a Recurrent-Depth Transformer (RDT) — a looped transformer that recycles layers multiple times per forward pass for deeper reasoning without massive parameter growth. The project drew 10,100 GitHub stars in its first week, reflecting intense developer curiosity about what's powering Anthropic's latest generation models. The architecture has three stages: a Prelude (initial layers), a Recurrent Block (looped up to 32 times with shared weights), and a Coda (final layers). Rather than stacking hundreds of unique layers, the recurrent block runs the same weights multiple times with learned injection parameters updating hidden states between loops — enabling implicit chain-of-thought reasoning in continuous latent space without generating intermediate tokens. The project supports Grouped Query Attention (GQA) with optional Flash Attention 2, Multi-Latent Attention (MLA), and sparse MoE with routed and shared experts. Model scales range from 1B to 1T parameters. The key claim is that RDT achieves reasoning depth comparable to fixed-depth models with far more parameters, since computational complexity scales with loop iterations rather than layer count. This would explain how Claude Mythos achieves strong reasoning performance without the extreme parameter counts of brute-force scaling — though Anthropic has neither confirmed nor denied the architecture.

SAM 3.1 is Meta's latest update to the Segment Anything Model family, released March 27 2026 as a drop-in replacement for SAM 3. The core innovation is object multiplexing: where the previous model required a separate processing pass for each tracked object, SAM 3.1 processes all tracked objects together in a single shared-memory pass, eliminating redundant computation across the decoder. The result is a doubling of throughput for videos with a medium number of objects—from 16 to 32 frames per second on a single H100 GPU—without sacrificing tracking accuracy. For applications like sports analytics, surveillance, or video editing that track 5–20 objects simultaneously, this makes real-time deployment on commodity cloud hardware feasible for the first time. SAM 3.1 inherits SAM 3's open-vocabulary segmentation capability (segmenting objects described by text prompts), which achieved 75–80% of human performance on the SA-CO benchmark covering 270K unique concepts. The model checkpoint is available on Hugging Face at `facebook/sam3.1`, and the codebase supports fine-tuning via the facebookresearch/sam3 repository. Meta released SAM 3.1 under a research license with commercial use provisions similar to its predecessors.