Graph files and weights

RustNN imports .webnn text and the equivalent webnn-graph-json representation. These are project interchange formats, not serialization formats defined by W3C WebNN. The format contracts are maintained by webnn-graph:

• Graph syntax and JSON representation
• External weights and packed 4-bit storage

This guide is included in the loader's Rustdoc as well as the website. The API contracts live on load_graph_from_path and rustnn_save_webnn.

Save, load, and compile

Saving a builder writes model.webnn and model.safetensors. Keep the pair together when moving the model. Saving borrows the builder without consuming it; it can still be compiled.

rust,ignore builder.rustnn_save_webnn(&outputs, "model.webnn")?; let graph_info = rustnn::load_graph_from_path("model.webnn")?; let mut graph = context.rustnn_build_graph(graph_info)?;

The loader selects the parser from the extension: .webnn text is parsed into GraphJson, while .json is deserialized directly into that same representation. Both then use the shared external-weight resolver and RustNN graph recorder, including shape inference and validation. Loading returns a backend-independent GraphInfo; it does not compile, execute, or numerically validate a model. Compile it with MLContext::rustnn_build_graph, then use the usual tensor write, dispatch, and read calls. Model-output comparisons belong in execution tests.

Weights and compatibility

External constants are resolved relative to the graph file. The shared resolver supports SafeTensors and manifest-backed raw weights; SafeTensors takes precedence. Its canonical external-weight documentation above specifies sidecar discovery, name matching, and validation. Resolved bytes are owned by GraphInfo, so sidecars are not reread on every dispatch.

The exporter writes ordinary constants using their corresponding SafeTensors storage types. For logical Int4 and Uint4 it uses the versioned packed-U8 extension: low-nibble-first bytes in a one-dimensional U8 tensor, with the graph declaration retaining the logical dtype and shape. Native SafeTensors 4-bit types are not required. Regenerate both graph and sidecar with compatible tooling; the loader validates the shared format's metadata and packing rules.

Dynamic dimensions require dynamic-inputs; constants remain static. See the dynamic-shape workflow and Dimension.

Other exports

For text without file output, use rustnn_webnn_text_for_outputs. For backend formats, finish a GraphInfo and use ConverterRegistry. Persist both the model and any weights returned in ConvertedGraph; these backend artifacts are separate from the source .webnn/SafeTensors pair. See the conversion recipe.