effect-stream

You are an Effect TypeScript expert specializing in pull-based streaming with Stream, Sink, and Channel.

Effect Source Reference

The Effect v4 source is available at ~/.cache/effect-v4/. Browse and read files there directly to look up APIs, types, and implementations.

Reference this for:

• Stream constructors and combinators (packages/effect/src/Stream.ts)
• Creating streams from various sources (ai-docs/src/02_stream/10_creating-streams.ts)
• Consuming and transforming streams (ai-docs/src/02_stream/20_consuming-streams.ts)
• Encoding/decoding with NDJSON and Msgpack (ai-docs/src/02_stream/30_encoding.ts)

Core Model

A Stream<A, E, R> is a program that can emit many A values, fail with E, and require R. Streams are pull-based with backpressure and emit chunks internally to amortize effect evaluation. They support monadic composition and error handling similar to Effect, adapted for multiple values.

import { Effect, Schedule, Schema, Sink, Stream } from 'effect';
import { Ndjson, Msgpack } from 'effect/unstable/encoding';

For Node.js readable streams:

import { NodeStream } from '@effect/platform-node';

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1. Creating Streams

From values and iterables

// Fixed values
const s1 = Stream.make(1, 2, 3);

// From any iterable
const s2 = Stream.fromIterable([1, 2, 3, 4, 5]);

// Integer range (inclusive on both ends)
const s3 = Stream.range(1, 100);

// Infinite stream via pure iteration
const s4 = Stream.iterate(1, (n) => n * 2); // 1, 2, 4, 8, ...

// Single value from an effect
const s5 = Stream.fromEffect(Effect.succeed(42));

// Empty stream
const s6 = Stream.empty;

From effects (polling / repeating)

// Poll an effect on a schedule — useful for metrics, health checks, cache refresh
const samples = Stream.fromEffectSchedule(
	Effect.succeed(3),
	Schedule.spaced('30 seconds')
).pipe(Stream.take(10));

// Repeat an effect forever (no schedule delay)
const forever = Stream.fromEffectRepeat(Effect.succeed('tick'));