fallback-chain-js

Tiny fallback chains for JS/TS — try providers until one succeeds.

Monorepo layout:

• packages/fallback-chain-js: the tiny library
• apps/fallbacklab: Next.js demo app (Firebase + Vertex AI)

Demo: https://fallbacklab.vercel.app

Library quickstart

pnpm -C packages/fallback-chain-js build

import { fallback } from "@khalidsaidi/fallback-chain-js";

const result = await fallback([
  () => primary(),
  () => secondary()
]);

How fallback works (short)

• Candidates are lazy functions called one-by-one.
• Rejections fall through to the next candidate.
• Resolved values can be rejected via accept(...).
• AbortSignal and per-attempt timeoutMs are supported.

AI discoverability

• Root: llms.txt
• Demo API: apps/fallbacklab/public/llms.txt
• OpenAPI: apps/fallbacklab/openapi.json

Development

pnpm install
pnpm -r build
pnpm -r test

Packages

• Library docs: packages/fallback-chain-js/README.md
• Demo app docs: apps/fallbacklab/README.md