Layer and width must stay explicit
Ster reads last-token hidden states from selected transformer layers and records hidden width in the artifact.
Ster by Wisent
Read, learn, measure, and steer open-weight models in Rust
Ster is a native Rust toolkit for reading last-token hidden states, learning directions from contrastive examples, evaluating them, and applying measured interventions during generation.
- Native Rust toolkit
- Reads last-token states
- CAA, PCA, logistic probes
- Width mismatch refused
A direction is only valid inside its exact boundary
Representation work breaks when model, layer, width, method, and intervention point drift apart.
Method must travel with the vector
Artifacts record trait, method, layer-indexed directions, training accuracy, and projection margin.
The wrong stream is refused
Ster refuses artifacts with the wrong product, schema, model, or vector width instead of applying them.
One path from contrastive examples to controlled generation
The workflow stays inside one native Rust binary and library crate with versioned JSON artifacts.
Read
Ster reads last-token hidden states from selected transformer layers.
Learn
Ster learns directions from contrastive examples with CAA, PCA, or logistic-probe training.
Measure
Ster evaluates artifacts with pair-ordering accuracy and projection margin, with holdout selection across method and layer.
Steer
Ster adds a measured direction in the residual stream during autoregressive generation.
Six native operations carry the workflow
One binary and one library crate share the same versioned JSON artifacts and native Candle runtime.
| Operation | Role in workflow |
|---|---|
| train | Learn directions from examples |
| optimize | Select across method and layer |
| evaluate | Score ordering and margin |
| generate | Apply steering during decoding |
| extract | Read selected hidden states |
| inspect | Read recorded fields |
The artifact contract refuses the wrong residual stream
Every steering artifact records identity and measurement fields before generation uses it.
| Artifact field | Boundary |
|---|---|
| Product identity | Wrong product refused |
| Schema identity | Wrong schema refused |
| Model revision | Wrong model refused |
| Hidden width | Wrong width refused |
| Method and trait | Kept with directions |
| Accuracy and margin | Recorded before steering |
Adoption questions answered by the contract
Does Ster route hosted models or manage fleets?
No. Ster controls local open-weight models; hosted routing, fleet placement, credentials, and release delivery belong to other products.
What checkpoints can the current runtime use?
The runtime supports local and Hugging Face Llama-family Safetensors checkpoints on CPU, with compile-time Metal and CUDA backends.
What stops a vector from the wrong model being applied?
Ster refuses artifacts with the wrong product, schema, model, or vector width instead of applying them to the wrong residual stream.
Start with the documented first steering workflow
Use Ster when you need a native Rust path from hidden states and contrastive examples to measured artifacts and controlled generation, with refusal at the artifact boundary.