Define type-safe RPC contracts with effect/unstable/rpc — Rpc.make payload/success/error/defect schemas, RpcSchema.Stream streaming responses, RpcGroup composition (add/merge/omit/prefix/annotate), and RpcMiddleware.Service definitions shared by client and server. Use when declaring or evolving RPC procedures, building a shared contract package, adding streaming endpoints, or defining auth/observability middleware types.

2026-06-1221

effect-rpc-client

mpsuesser/pi-effect-harness

Consume typed RPC services with Effect's RpcClient — protocol layers (HTTP, WebSocket, TCP, worker, in-memory), RpcSerialization codecs, per-call and ambient headers, streaming calls, interruption, reconnection, and RpcClientError handling. Use when calling an RpcGroup from a client, wiring a client transport + serialization stack, debugging RPC transport failures or reconnects, or testing RPC consumers with RpcTest.

2026-06-1221

effect-rpc-server

mpsuesser/pi-effect-harness

Serve RpcGroup contracts with Effect's RpcServer — handler layers (RpcGroup.toLayer/toLayerHandler), protocol layers (HTTP, WebSocket, TCP, stdio, worker), RpcSerialization, server middleware, streaming results, interruption and shutdown semantics, RpcTest. Use when implementing the server side of an Effect RPC API, mounting RPC on an HttpRouter or existing HTTP app, choosing a wire format, implementing RpcMiddleware, handling client aborts, or testing RPC handlers.

2026-06-1221

effect-http-client

mpsuesser/pi-effect-harness

Make outgoing HTTP requests with Effect's HttpClient — HttpClientRequest builders, schema-decoded HttpClientResponse bodies, the HttpClientError taxonomy, retryTransient/rate limiting/cookies/redirects, streaming uploads and downloads, and FetchHttpClient/NodeHttpClient transport layers. Use when calling external REST/JSON APIs, uploading or downloading files and streams, adding retries/auth/tracing to outbound HTTP, or mocking HTTP responses in tests.

2026-06-1221

effect-http-server

mpsuesser/pi-effect-harness

Build HTTP servers with effect/unstable/http — HttpRouter routes and middleware, HttpServerRequest schema decoding, HttpServerResponse constructors, multipart uploads, websocket upgrades, static files, NodeHttpServer/BunHttpServer layers, and in-memory web handlers. Use when serving raw HTTP routes, reading request bodies/cookies/uploads, writing server middleware, streaming responses, or testing handlers without a real port.

2026-06-1221

effect-socket

mpsuesser/pi-effect-harness

Build bidirectional socket transports with effect/unstable/socket — the Socket run/writer surface, WebSocket-backed sockets, TCP/Unix-domain clients via NodeSocket, SocketServer accept loops, channel adapters, the SocketError taxonomy, and reconnect patterns. Use when connecting to or serving raw TCP, Unix-domain, or WebSocket endpoints, framing socket bytes with Stream/Channel (NDJSON), building reconnecting socket clients, or providing socket transports to RPC/devtools layers.

2026-06-1221

name	effect-path
description	Use effect Path for platform-abstract file path operations including joining, resolving, and URL conversion.

path

Use effect Path abstraction for platform-abstract file path operations. Apply this skill when working with file paths, joining segments, resolving absolute paths, or converting between file URLs and paths. Path.layer supplies POSIX semantics from effect; Node.js and Bun platform layers provide host-specific path semantics. @effect/platform-browser does not provide a BrowserPath layer in beta.74, so browser code should provide Path.layer or a custom layer explicitly.

Import Pattern

import { Path } from 'effect';

Service Injection

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
});

Path Separator

import { Path } from 'effect';
import { Effect } from 'effect';

// Get platform-specific separator
const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const separator = path.sep; // "/" on Unix, "\" on Windows
});

Path Operations

join - Combine path segments

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const fullPath = path.join('src', 'components', 'Button.tsx');
	// "src/components/Button.tsx" on Unix
	// "src\components\Button.tsx" on Windows
});

resolve - Convert to absolute path

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const absolutePath = path.resolve('src', 'index.ts');
	// "/Users/username/project/src/index.ts" on Unix
	// "C:\Users\username\project\src\index.ts" on Windows
});

normalize - Clean up path

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const clean = path.normalize('/foo/bar//baz/asdf/quux/..');
	// "/foo/bar/baz/asdf"
});

dirname - Get directory portion

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const dir = path.dirname('/foo/bar/baz.txt');
	// "/foo/bar"
});

basename - Get file name

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const name = path.basename('/foo/bar/baz.txt');
	// "baz.txt"

	const nameWithoutExt = path.basename('/foo/bar/baz.txt', '.txt');
	// "baz"
});

extname - Get file extension

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const ext = path.extname('/foo/bar/baz.txt');
	// ".txt"
});

parse - Decompose path into components

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const parsed = path.parse('/home/user/dir/file.txt');
	// {
	//   root: "/",
	//   dir: "/home/user/dir",
	//   base: "file.txt",
	//   ext: ".txt",
	//   name: "file"
	// }
});

format - Construct path from components

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const fullPath = path.format({
		root: '/',
		dir: '/home/user/dir',
		base: 'file.txt'
	});
	// "/home/user/dir/file.txt"
});

isAbsolute - Check if path is absolute

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const isAbs = path.isAbsolute('/foo/bar');
	// true on Unix
	const isRel = path.isAbsolute('foo/bar');
	// false
});

relative - Get relative path

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const relPath = path.relative(
		'/data/orandea/test/aaa',
		'/data/orandea/impl/bbb'
	);
	// "../../impl/bbb"
});

URL Conversions (Effectful)

Both operations can fail with BadArgument error.

fromFileUrl - Convert file URL to path

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const filePath = yield* path.fromFileUrl(
		new URL('file:///home/user/file.txt')
	);
	// "/home/user/file.txt" on Unix
	// "C:\home\user\file.txt" on Windows
});

toFileUrl - Convert path to file URL

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	const fileUrl = yield* path.toFileUrl('/home/user/file.txt');
	// URL object with href "file:///home/user/file.txt"
});

Complete Example

import { Path } from 'effect';
import { Effect } from 'effect';

const buildOutputPath = Effect.gen(function* () {
	const path = yield* Path.Path;

	// Join segments
	const srcPath = path.join('src', 'index.ts');

	// Resolve to absolute
	const absoluteSrc = path.resolve(srcPath);

	// Get directory and basename
	const dir = path.dirname(absoluteSrc);
	const base = path.basename(absoluteSrc, '.ts');

	// Build output path
	const outputPath = path.join(dir, '..', 'dist', `${base}.js`);

	// Normalize
	return path.normalize(outputPath);
});

toNamespacedPath - Convert to namespaced path

import { Path } from 'effect';
import { Effect } from 'effect';

const program = Effect.gen(function* () {
	const path = yield* Path.Path;
	// On POSIX, returns the path unchanged.
	// On Windows, converts to a \\?\-prefixed namespaced path
	// that allows longer path lengths.
	const namespaced = path.toNamespacedPath('/foo/bar/baz.txt');
});

DO

Import Path from effect
Use path.sep for platform-specific separators
Use path.join() to combine path segments
Use path.resolve() to get absolute paths
Handle errors from fromFileUrl and toFileUrl with Effect error handling
Pass a URL object (not a string) to fromFileUrl

DON'T

Import node:path directly (breaks portability)
Hardcode "/" or "\" separators
Manually concatenate paths with string operations
Assume file URL format without using conversion utilities
Pass a string to fromFileUrl — it requires a URL object