2.4 compatibility in Nexa 3.0

This page describes the retained 2.4 language/runtime path. Sources without a version declaration use this path. Start new Open Programs with Nexa 3.0; compare contracts in the migration guide.

Rust AVM and WASM support

The Python compiler and runtime are the Nexa 2.4 reference implementation. Rust AVM expands its coverage through shared semantic fixtures and currently supports this subset.

Path	Current behavior
Rust compilation and interpretation	Declaration initialization, integer/float arithmetic, local/global variables, jumps, returns, and Agent calls
Provider boundary	Interpreter::set_agent_executor; the CLI text provider uses NEXA_API_KEY, optional NEXA_BASE_URL, and a 30-second request timeout
Tools, structured output, full Harness	Use the Python reference runtime
Unimplemented opcode or call	Explicit error

The Rust compiler rejects tool declarations with Tool … requires the Python runtime. Run programs containing tools on the Python backend.

Shared semantics

Python and Rust tests consume tests/fixtures/conformance/programs.json, covering integer precision, division, variables, and Agent calls. This complete program is part of that shared path and returns 2.5 offline.

flow main {
    result = 5 / 2;
}

Run Rust checks from the Nexa checkout:

cargo test --manifest-path avm/Cargo.toml

WASM executor

WASM uses Wasmtime 48 LTS. With the wasm feature enabled, it executes real modules with scalar parameters, retained instance state, memory limits, fuel, and epoch interruption. Without the feature, execution returns an explicit error.

cargo test --manifest-path avm/Cargo.toml --features wasm

WASI imports and reference-type parameters are not yet integrated. Configure WASM isolation and ordinary Python tool execution separately. A Python tool declaring sandbox: true still requires an actual isolation backend.

Evaluation scope

Shared fixtures check the semantics of their specified programs. Real model quality, cost, and latency require a reproducible provider, model, input, budget, and environment. Architecture evolution retains the historical design context. Performance ratios from older baselines are omitted until remeasured on the current runtime.

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Source and validation · rust