Haversack

A haversack is the bag you pack once and carry everywhere.

Every new Effect project starts by rebuilding the same things: an email service wrapped around Resend, feature flags that fail open, a Stripe client with proper tracing spans, a rate limiter on Durable Objects, CPF validation with real check digits. Haversack is that code — extracted from production apps, written as idiomatic Effect from end to end, and packed into one package so you never write it twice.

Everything is a typed Effect service. No loose async functions, no untyped errors, no global config. Each capability is a Context.Service with tagged errors, tracing spans, and a Layer you compose like any other — config in, service out, test layers included.

Import only what you use. Each module is an independent subpath export, and heavy SDKs (Stripe, Resend, posthog-js, ...) are optional peer dependencies: if you never import /stripe, you never install Stripe.

bun add @ayronforge/haversack effect

Haversack is built on Effect 4 (effect@^4.0.0).

What's inside

Schemas

Reusable Effect Schema building blocks with canonical storage values and separate presentation formatters.

import { Schema } from "effect";
import {
  CnpjFromString,
  CpfFromString,
  EmailAddressFromString,
  EndpointUrlFromString,
  formatCnpj,
  formatCpf,
  PhoneNumberFromString,
  SlugFromString,
  UuidFromString,
} from "@ayronforge/haversack/schema";

const cpf = Schema.decodeUnknownSync(CpfFromString)("529.982.247-25");
// "52998224725" — canonical digits in both decoded and encoded forms
formatCpf(cpf); // "529.982.247-25"

const cnpj = Schema.decodeUnknownSync(CnpjFromString)("11.222.333/0001-81");
// "11222333000181" — canonical digits in both decoded and encoded forms
formatCnpj(cnpj); // "11.222.333/0001-81"

const phone = Schema.decodeUnknownSync(PhoneNumberFromString({ defaultCountry: "BR" }))(
  "(11) 98765-4321",
);
// "+5511987654321" — canonical E.164

const email = Schema.decodeUnknownSync(EmailAddressFromString())("[email protected]");
// "[email protected]" — domain normalized, local part preserved by default

const host = Schema.decodeUnknownSync(EndpointUrlFromString)("https://api.example.com/");
// "https://api.example.com" — normalized, rejects query strings and fragments

const slug = Schema.decodeUnknownSync(SlugFromString)("Café com Leite!");
// "cafe-com-leite"

const uuid = Schema.decodeUnknownSync(UuidFromString)("0198A3FC-9DB1-7BD5-8A1E-2F6A1F4C9D10");
// "0198a3fc-9db1-7bd5-8a1e-2f6a1f4c9d10" — strict, canonical UUID

CepLookup.layerViaCep({ fetch }) resolves an already parsed Cep without capturing global I/O and distinguishes not-found, unavailable, and malformed responses. PhoneNumberFromString parses international or explicitly country-scoped national input through libphonenumber-js.

Email

A provider port with a Resend adapter. Send pre-rendered HTML or a react-email element, and sync contacts to segments and topics.

import { Effect, Layer, Redacted } from "effect";
import { EmailConfig, EmailLive, EmailService } from "@ayronforge/haversack/email";

const config = EmailConfig.layer({
  apiKey: Redacted.make(process.env.RESEND_API_KEY!),
  from: "Acme <[email protected]>",
});

const program = Effect.gen(function* () {
  const email = yield* EmailService;
  yield* email.send({
    to: "[email protected]",
    subject: "Welcome",
    html: "<p>Hello!</p>",
    idempotencyKey: "welcome-user-1",
  });
}).pipe(Effect.provide(EmailLive.pipe(Layer.provide(config))));

PostHog

Server-side capture and feature flags run over fetch without an SDK and work in Workers. Server delivery and evaluation are fail-open: failures log and fall back rather than break a request. The transport is Effect's FetchHttpClient.Fetch reference (defaults to globalThis.fetch); tests and hosts inject their own with Effect.provideService(FetchHttpClient.Fetch, fn).

import { Effect, Layer, Redacted } from "effect";
import { FeatureFlags, PostHogAnalytics, PostHogConfig } from "@ayronforge/haversack/posthog";

const config = PostHogConfig.layer({
  projectToken: Redacted.make(process.env.POSTHOG_TOKEN!),
});

const program = Effect.gen(function* () {
  const analytics = yield* PostHogAnalytics;
  yield* analytics.track({ event: "signup", distinctId: "user_1" });

  const flags = yield* FeatureFlags;
  return yield* flags.isEnabled(
    { key: "new-checkout", fallback: false },
    { distinctId: "user_1" },
  );
}).pipe(
  Effect.provide(PostHogAnalytics.layer.pipe(Layer.provide(config))),
  Effect.provide(FeatureFlags.layer.pipe(Layer.provide(config))),
);

React feature-flag policy lives in @ayronforge/haversack/posthog/react and composes directly with the official @posthog/react provider. useFeatureFlag subscribes through useSyncExternalStore; FeatureGate adds typed fallback and pending rendering without owning SDK initialization, capture, or identity.

Stripe

An SDK wrapper where every call is named: the operation becomes the tracing span (stripe.checkout.sessions.create) and error metadata.

import { Effect, Layer, Redacted } from "effect";
import { StripeClient, StripeConfig } from "@ayronforge/haversack/stripe";

const config = StripeConfig.layer({
  secretKey: Redacted.make(process.env.STRIPE_SECRET_KEY!),
  webhookSecret: Redacted.make(process.env.STRIPE_WEBHOOK_SECRET!),
});

const program = Effect.gen(function* () {
  const stripe = yield* StripeClient;
  const session = yield* stripe.use("checkout.sessions.create", (sdk) =>
    sdk.checkout.sessions.create({ mode: "subscription", line_items: [/* ... */] }),
  );
  return session.url;
}).pipe(Effect.provide(StripeClient.layer.pipe(Layer.provide(config))));

verifyWebhook(payload, signature) validates webhook signatures with tagged errors. makeStripeClientFromSdk is the seam for injecting a fake SDK in tests.

Auth

Thin client layers for WorkOS (/auth/workos) and Clerk (/auth/clerk), following the same provider pattern: config with redacted keys, use with spans, tagged errors. Clerk additionally exposes useWebhook for verified webhook events.

Cloudflare

Workers primitives, all binding-oriented — you pass bindings explicitly, the library never reads a global env.

• RequestRateLimiter — fixed-window and token-bucket over effect/persistence, with layerMemory for tests and layerDurableObject(namespace) for cross-isolate limits. The namespace points to a caller-owned Durable Object implementing RateLimiterRpc; the application owns persistence, migrations and cleanup. Fail-open on store failures.
• DistributedLock / withLock(key, effect) — acquireUseRelease lifecycle over a caller-owned Durable Object implementing the typed lease RPC contract.
• makeQueueClientService(queue) — queue producer publishing in Cloudflare's 100-message batches.
• AnalyticsEngine — the strict Analytics Engine SQL API with Schema-decoded rows. Non-successful responses remain typed query errors; the library does not infer undocumented Cloudflare error semantics from response text. Requests go through the FetchHttpClient.Fetch reference, so no global fetch is captured.
• makeR2BlobStorageLayer(bucket) / R2BlobPresignerLive — the blob storage contract over R2 (see Contracts below).
• @ayronforge/haversack/cf/workflow — makeCloudflareWorkflowEngineLayer({ workflow, step }) adapts effect/workflow to Cloudflare Workflows: activities map to step.do with retries, durable deferreds to sendEvent/waitForEvent, durable clocks to step.sleep.

Contracts and AWS

@ayronforge/haversack/contracts defines vendor-neutral ports — currently BlobStorage (put/get/delete/exists/list) and BlobPresigner. Code against the port; pick the implementation per runtime:

import { Effect } from "effect";
import { BlobStorage } from "@ayronforge/haversack/contracts";
import { makeR2BlobStorageLayer } from "@ayronforge/haversack/cf";
import { S3BlobStorageLive, S3Config } from "@ayronforge/haversack/aws";

const program = Effect.gen(function* () {
  const storage = yield* BlobStorage;
  yield* storage.put("reports/q3.pdf", bytes, { contentType: "application/pdf" });
  const report = yield* storage.get("reports/q3.pdf", { maxBytes: 10_000_000 });
});

// In a Worker:  Effect.provide(program, makeR2BlobStorageLayer(env.BUCKET))
// Elsewhere:    Effect.provide(program, S3BlobStorageLive) + S3Config.layer({ ... })

BlobPresigner.presignPut signs the Content-Type and, when you pass contentLength, the exact body size too. Browsers send Content-Length automatically, so an upload whose body is any other size is rejected by the storage before it is written:

const url = yield* presigner.presignPut({
  key: "uploads/avatar.png",
  contentType: "image/png",
  contentLength: file.size,
  expiresInSeconds: 600,
});

Testing

• runWithService(tag, layer) — a Promise-based runner for exercising one service in tests without repeating provide/run boilerplate.
• testExecutionContext() — a fake Cloudflare ExecutionContext whose drainWaitUntil() awaits fire-and-forget work.
• testStub<T>(partial) — the sanctioned escape hatch for faking SDK clients in tests. Never use it in production code.
• applyTestEnvDefaults(record) — fills missing process.env keys.

Environment configuration

Haversack deliberately contains no env-var handling. Use @ayronforge/envil for type-safe environment validation and feed the decoded values into the config layers.

Contributing

bun install
bun run typecheck
bun test
bun run build   # bundles with tsdown and smoke-tests every entrypoint

Issues and pull requests are welcome. If you're adding a new integration, follow the house style: every capability is a Context.Service with a config layer, tagged errors, and tracing spans — and multi-vendor capabilities get a port in /contracts with one implementation per vendor.

License

MIT