---
name: inngest-nextjs-patterns
description: Use this skill whenever scaffolding Inngest event-driven functions in a Next.js (App Router) project — creating the client, the /api/inngest route handler, typed events with Zod schemas, durable event-triggered functions, scheduled cron functions, or fan-out orchestrators. Trigger even if the user just says "add a background job", "process this async", "schedule X every hour", or "send an event when Y happens" in a Next.js codebase — these all map to Inngest patterns. Also trigger when reviewing existing Inngest code to enforce event-naming, function-id stability, and step-idempotency conventions.
---

# Inngest + Next.js Patterns

Templates and conventions for building event-driven, durable background work on Inngest from a Next.js App Router project. The skill enforces the conventions Inngest's own docs use (decentralized `eventType()` schemas, kebab-case stable function IDs, idempotent steps) so that retries, replays, and concurrency controls actually do what they advertise.

## When to Apply

Read this skill when you are:

- Setting up Inngest in a Next.js app for the first time (client + route handler + first function)
- Adding a new background job, webhook handler, or scheduled task to a Next.js app
- Defining a new domain event that other functions will trigger on
- Orchestrating multi-step work that must survive process restarts (durable workflows, sagas)
- Reviewing existing Inngest code for event naming, step idempotency, or stable function IDs
- Migrating from `setTimeout` / a queue library / a cron service to Inngest's durable execution model

## How to Use

1. **First time in this codebase?** Read [`references/conventions.md`](references/conventions.md) before writing anything. The conventions explain *why* event names take a specific shape, why function IDs must be stable, and why every `step.run` must be idempotent — once you understand the reasoning, the templates make sense.
2. **Pick a template** from the catalog below based on what you're creating.
3. **Render it** by substituting the documented parameters. Each template has a parameter table at the top of its file.
4. **Wire it up:** new functions must be added to `src/inngest/functions/index.ts` (the registry the route handler reads). The conventions doc shows the registry pattern.

## Available Templates

| Template | Output Path | Use When |
|---|---|---|
| [`client.ts.template`](assets/templates/client.ts.template) | `src/inngest/client.ts` | One-time setup: create the singleton Inngest client. Generate **once per app**. |
| [`route-handler.ts.template`](assets/templates/route-handler.ts.template) | `src/app/api/inngest/route.ts` | One-time setup: the App Router endpoint Inngest hits to invoke your functions. Generate **once per app**. |
| [`event.ts.template`](assets/templates/event.ts.template) | `src/inngest/events/{domain}.ts` | Defining a new typed event (with Zod schema) that producers send and functions consume. |
| [`function.ts.template`](assets/templates/function.ts.template) | `src/inngest/functions/{name}.ts` | Standard event-triggered durable function with steps. Parameterized retries, concurrency, throttle, debounce, cancelOn, onFailure. |
| [`function-cron.ts.template`](assets/templates/function-cron.ts.template) | `src/inngest/functions/{name}.ts` | Scheduled function — runs on a cron expression (with timezone). Optionally also accepts a manual event trigger for ad-hoc invocation. |
| [`function-fan-out.ts.template`](assets/templates/function-fan-out.ts.template) | `src/inngest/functions/{name}.ts` | Orchestrator that receives one event and fans out work — via `step.sendEvent` (fire-and-forget) or `Promise.all(step.invoke(...))` (wait for results). |

## Quick Reference

- **Event name shape:** `domain/entity.verb_past` — e.g., `app/user.created`, `shop/order.placed`, `billing/invoice.paid`. The conventions doc has the full rule.
- **Function `id`:** stable kebab-case, **never rename it** after deploy — Inngest uses it as the durable state key.
- **Step `id`:** descriptive kebab-case, also durable; changing one re-runs that step on replay.
- **Idempotency:** every `step.run` must be safely retryable. If it calls a third-party API that mutates state, pass an idempotency key.
- **Dev server:** `npx inngest-cli@latest dev`, then UI at http://localhost:8288. Set `INNGEST_DEV=1` in `.env.local` to point the SDK at it.

## Project Layout Assumption

Templates assume a `src/` directory with App Router:

```
src/
├── app/api/inngest/route.ts          # generated by route-handler template
└── inngest/
    ├── client.ts                     # generated by client template
    ├── events/                       # one file per domain (events.shop.ts, events.user.ts)
    │   └── {domain}.ts               # generated by event template
    └── functions/
        ├── index.ts                  # registry: re-exports all functions as an array
        └── {name}.ts                 # generated by function/cron/fan-out templates
```

If your project uses a different layout (no `src/`, or Pages Router), override the output paths in `config.json`. The conventions doc explains the trade-offs.

## Setup

`config.json` controls path overrides. On first use, check whether its fields are filled in — if not, ask the user before generating (project root differs from the default assumption).

## Related Skills

- `vercel:ai-sdk` — if your Inngest functions invoke LLMs, the AI SDK gives you streaming + provider abstraction; pair them with `step.run` for retry safety.
- `vercel:vercel-functions` — Inngest's `serve()` adapter for Next.js runs as a Vercel Serverless Function by default; the AI SDK skill has notes on Fluid Compute and timeout extension for long agent runs.
