Reducers

Three reference implementations of the Vela state-transition function, kept at equal weight.

Three reducers, one protocol. Each compiles the same canonical event into the same state mutation. Conformance is the share of the public test-vector suite a reducer currently passes at protocol version v0.48.0. The Rust crate is the normative reference; the Python and TypeScript reducers track it.

Specimens Three reducers · one transition function

  1. Reference implementation

    vela-rs

    Rust

    100 % conformance 
    
              use vela::{StateEvent, Status, Reducer};

let event = StateEvent::accepted_transition()
    .frontier("alzheimers.neurovascular.bbb")
    .finding("vf_06cfcbe7c449d86a")
    .from(Status::Contested)
    .to(Status::Replicated)
    .evidence(["ev_perturb_441", "ev_cohort_118"])
    .sign(&keypair)?;

state.apply(&event)?;

    package vela

    The normative reference. Test vectors are derived from this implementation; other reducers track it.

    Source

  2. Researcher binding

    vela-py

    Python

    96 .4 % conformance 
    
              from vela import StateEvent, Status, apply

event = StateEvent.accepted_transition(
    frontier="alzheimers.neurovascular.bbb",
    finding="vf_06cfcbe7c449d86a",
    from_=Status.CONTESTED,
    to=Status.REPLICATED,
    evidence=["ev_perturb_441", "ev_cohort_118"],
).sign(keypair)

apply(state, event)

    package vela-py

    PyO3 bindings on top of vela-rs plus pure-Python ergonomics for notebooks and pipelines.

    Source

  3. Read-side reducer

    vela-ts

    TypeScript

    81 .2 % conformance 
    
              import { StateEvent, Status, verify } from "@vela/core";

const event = StateEvent.acceptedTransition({
  frontier: "alzheimers.neurovascular.bbb",
  finding: "vf_06cfcbe7c449d86a",
  from: Status.Contested,
  to: Status.Replicated,
  evidence: ["ev_perturb_441", "ev_cohort_118"],
});

verify(state, event); // read-side reducer

    package @vela/core

    Read-only verifier and event reducer for browser, edge, and Node. Suitable for atlases and viewers, not yet for canonical commit.

    Source

Install

Pick a reducer for your environment. The Rust crate is the canonical commit path: anyone applying state transitions for a frontier should run vela-rs (directly or via the Python binding). The TypeScript reducer is read-only and is suitable for atlases, viewers, and verification at the edge.

  1. vela-rs Rust

    Cargo 
    # Cargo.toml
[dependencies]
vela = "0.48.0"

# or from source
cargo add vela@0.48.0
    Source on GitHub

  2. vela-py Python

    uv / pip 
    # uv (recommended)
uv add vela

# pip
pip install vela==0.48.0
    Source on GitHub

  3. vela-ts TypeScript

    npm / pnpm / bun 
    pnpm add @vela/core@0.48.0

# or
npm install @vela/core@0.48.0
bun add @vela/core@0.48.0
    Source on GitHub

Conformance

The public test-vector suite at vela-science/vela/test-vectors is the single source of truth for what "passes" means. Each test vector pairs a canonical event with the state mutation a conforming reducer must produce. The Rust reducer passes the whole suite by construction; the Python and TypeScript reducers report their pass rate against the same vectors at every release.

Reducer Conformance Vectors Version
vela-rs Rust 100.0% 1480 / 1480 v0.48.0
vela-py Python 96.4% 1427 / 1480 v0.48.0
vela-ts TypeScript 81.2% 1202 / 1480 v0.48.0

Test-vector counts taken from the suite tagged vectors/v0.48.0. The number grows monotonically with each protocol version; reducers must pass every prior version's vectors plus the new ones.

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