schema-logic

Behavior as data. A declarative logic layer built on Effect v4 and its first-class Schema module.

schema-logic is the second floor of a larger stack:

Schema      structure as data    ← Effect Schema (given)
Logic       behavior  as data    ← this repo
Workflow    process   as data    ← later
Ontology    system    as data    ← later

Most application logic is written as opaque functions:

function approveCandidate(ctx) {
  if (ctx.role !== "reviewer") throw new Error("forbidden")
  ctx.candidate.status = "approved"
  emit("candidate.approved", { id: ctx.candidate.id })
}

An agent — or a devtool, or an auditor — can only run that. It cannot read it.

schema-logic represents the same behavior as an inspectable value:

const ApproveCandidate = Logic.Action("ApproveCandidate", ($) => $.do(
  $.require($.eq($.ref.actor.role, "reviewer"), "forbidden"),
  $.set($.ref.candidate.status, "approved"),
  $.emit("candidate.approved", { id: $.ref.candidate.id }),
))

This is a value: an AST you can execute, diff, trace, serialize, explain, or hand to an agent to reason about — not just call.

Why

The bet, shared with projects like Foldkit, Datomic, and Palantir Foundry, is that correctness and machine-legibility come from constraining the shape of programs, not from maximizing developer freedom. When every state transition flows through one inspectable form, you get the same payoff Foldkit's Model → Message → Update loop gets for UI — replay, time-travel, semantic diffs, execution traces — but for all application logic, not just rendering.

schema-logic is the "Logic as a value" layer that Datomic (facts as data) and Foundry (organizations as data) gestured at but never quite reified.

Status: v0 (Logic layer only)

v0 is intentionally narrow. It ships the Logic layer and nothing above it. Workflow and Ontology are out of scope until the Logic primitives and interpreter are solid.

What v0 includes

• AST construction via a namespaced builder API (Logic.Action, $.do, $.set, …) with proxy-based symbolic refs ($.ref.candidate.status).
• An Effect-based interpreter — Logic.evaluate(action, input) returns Effect<Result, LogicError, Store | EventSink>, so reads, writes, and events run through injectable services and inherit Effect's error channel, concurrency, and tracing.
• A single pnpm package on effect@4 (Schema is a first-class export of v4), tested with vitest.

Primitive set

Group	Primitives
Kernel	do, let, if, eq, and, or, not, literals, refs
Core mutation	require, set, get / query, create, emit
Collections	map, filter, match
Control / failure	fail, return, retry

No Level-3 domain verbs (e.g. approve, assign) in v0 — those are meant to be composed from the kernel, and proving they can be is the point of this milestone.

Foundation

• Runtime/data: effect-smol (Effect v4, currently 4.0.0-beta.74), vendored as a git submodule at .context/effect-v4 for reference. Schema is imported directly: import { Schema, Effect } from "effect".
• Package manager: pnpm
• Tests: vitest

git clone --recurse-submodules <this-repo>
# or, if already cloned:
git submodule update --init --depth 1

See PLAN.md for the build plan.