BAR
BAR, or Branch-Adapt-Route, is Ai2’s released modular language-model family built from an Olmo 2 7B anchor and independently trained capability experts. Math, coding, tool-use, and safety experts are combined through a router into a final five-expert mixture, enabling capability updates without retraining the full model. The public checkpoints include the original anchor, intermediate two-expert combinations, and final combined model as variants. This is a concrete weight release supporting a post-training method, rather than a framework-only announcement. Expert merging and routing must be evaluated for interactions and task quality.
2026-04-20
Five experts derived from 7B backbone; total undisclosed
Modular mixture-of-experts Transformer
Apache-2.0
Specifications
- Parameters
- Five experts derived from 7B backbone; total undisclosed
- Architecture
- Modular mixture-of-experts Transformer
- License
- Apache-2.0
- Type
- text
- Modalities
- text
Benchmark Scores
Advanced Specifications
- Model Family
- BAR
- API Access
- Not Available
- Chat Interface
- Not Available
- Variants
- 7B anchor2x7B expert pairs5x7B combined
Capabilities & Limitations
- Capabilities
- reasoningcodingtool usemodular adaptation
- Known Limitations
- Research checkpointsIndividual experts and the combined model have different behavior
- Notable Use Cases
- modular post-training researchspecialist composition