● An agent runtime for Effect applications

Agents,with cause.

Build autonomous TypeScript agents without leaving Effect behind. Schemas stay canonical, failures stay typed, dependencies stay visible, and every resource stays inside a Scope.

Get started →See one complete Agent

The whole runtime contract

Effect<A, E, R>

A: schema-decoded output
E: AI + tool + domain failures
R: model + handlers + services

No hidden runtime. The signature is the architecture.

01 / SCHEMA

One source of truth

Input, output, Tool, wire, and stored values begin as Effect Schemas. Provider shapes are derived.

02 / LAYER

Requirements stay visible

Models, Tool handlers, stores, clocks, sandboxes, and policies arrive through explicit Layers.

03 / SCOPE

Nothing outlives its owner

Model streams, Tool fibers, queues, clients, and attached children belong to the Run Scope.

04 / RECORD

Recovery stays honest

Replay rebuilds state, never external effects. Ambiguous outcomes stay explicit rather than guessed.

const Definition = Agent.define("triage", {
  input: Schema.Struct({ repo: Schema.String, issueNumber: Schema.Int }),
  output: Schema.Struct({
    severity: Schema.Literals(["low", "medium", "high", "critical"]),
    explanation: Schema.String,
  }),
  instructions: ({ repo, issueNumber }) => `Triage ${repo}#${issueNumber}.`,
  toolkit: TriageTools,
  policy: AgentPolicy.make({ maxTurns: 12, maxToolCalls: 20, maxDuration: "10 minutes" }),
});

const Triage = Agent.withModel(Definition, AnthropicLanguageModel.model("claude-sonnet-5"));

const result = AgentRuntime.run(Triage, { repo: "acme/api", issueNumber: 123 }).pipe(
  Effect.provide(AppLive),
  Effect.scoped,
); // Effect<AgentResult<Output>, AgentFailure | DomainFailure, Requirements>

BUILD

Define an Agent

Schema input and output, native Effect AI Tools, a bounded policy, one explicit Model binding.

Agent definitions →RUN

Run or observe

One interpreter, three views: an Effect result, a semantic Stream, or a scoped detached Run.

Run & stream →RECOVER

Survive interruption

Durable admission and crash recovery on Node/SQLite and Cloudflare, with one terminal Settlement.

Persistence & durability →PROVE

Test without a provider

Script model Turns, inject Layers, control time and IDs, and verify the semantic trace offline.

Deterministic testing →