Inngest v3 to v4 Migration

Use this skill when the user asks to upgrade Inngest, fix v3/v4 errors, migrate realtime, or clean up a codebase that has mixed SDK patterns.

Primary reference: https://www.inngest.com/docs/reference/typescript/v4/migrations/v3-to-v4

This skill is agent-first: detect actual usage first, make mechanical API changes in a controlled order, then typecheck and run focused tests.

When to Trigger

Use this skill for requests like:

• "Upgrade Inngest from v3 to v4"
• "Fix our Inngest v4 migration"
• "We're getting signing key required / cloud mode errors after upgrading"
• "step.invoke with a string function ID stopped working"
• "@inngest/realtime broke after installing inngest@4"
• "Move from EventSchemas to eventType"
• "Make this existing Inngest repo v4-compatible"

If the user asks for a broad codebase reliability audit first, use inngest-brownfield-audit to choose scope, then return here for the v4 changes.

Migration Scan

Start by locating all Inngest surfaces:

rg -n '"inngest"|"@inngest/realtime"|"@inngest/agent-kit"' package.json **/package.json
rg -n 'new Inngest|EventSchemas|eventType|staticSchema|createFunction\\(|serve\\(|connect\\(|step\\.invoke|referenceFunction|@inngest/realtime|realtimeMiddleware|useInngestSubscription|serveHost|rewriteGatewayEndpoint|logLevel|streaming:|signingKey|signingKeyFallback|baseUrl|INNGEST_DEV|INNGEST_SIGNING_KEY' .

Then classify the repo:

• No Inngest yet: use inngest-setup, not this migration skill.
• v3 only: migrate the SDK and all breaking changes together.
• mixed v3/v4: prioritize removing broken v3 APIs from v4 code.
• v4 mostly done: focus on missed runtime gotchas like local dev mode,

serverless maxRuntime, realtime package imports, and string step.invoke.

Before editing, record:

Inngest migration scan:
- Current package versions:
- Client files:
- Serve/connect entrypoints:
- Functions using old trigger syntax:
- EventSchemas usage:
- Realtime v3 package usage:
- step.invoke string IDs:
- Serverless runtime constraints:
- Tests/checks available:

Upgrade Order

1. Update package versions.
2. Fix client construction and local/prod mode.
3. Move serve options to the client.
4. Move triggers into createFunction options.
5. Replace EventSchemas with eventType() / staticSchema().
6. Rewrite step.invoke() string IDs.
7. Migrate realtime from @inngest/realtime to v4 native APIs.
8. Update middleware and logging.
9. Configure checkpointing/serverless runtime.
10. Typecheck, run tests, and optionally sync with the dev server.

Package and Environment

Install the latest v4 SDK:

npm install inngest@latest
# or pnpm add inngest@latest
# or yarn add inngest@latest

If the repo uses v3 realtime, remove @inngest/realtime; v4 realtime lives in the inngest package and subpaths such as inngest/realtime, inngest/react, and native step.realtime / inngest.realtime.

v4 defaults to Cloud mode. For local development, use an env var:

INNGEST_DEV=1 npm run dev

Do not hardcode isDev: true in source unless the repo's existing environment pattern clearly scopes it to local-only code. Production should use INNGEST_SIGNING_KEY.

Client and Serve Options

In v4, options such as signingKey, signingKeyFallback, and baseUrl belong on new Inngest(...), not on serve(...).

// Old v3
app.use(
  "/api/inngest",
  serve({
    client: inngest,
    functions,
    signingKey: process.env.INNGEST_SIGNING_KEY,
    baseUrl: process.env.INNGEST_BASE_URL,
  })
);

// New v4
export const inngest = new Inngest({
  id: "my-app",
  signingKey: process.env.INNGEST_SIGNING_KEY,
  baseUrl: process.env.INNGEST_BASE_URL,
});

app.use("/api/inngest", serve({ client: inngest, functions }));

If the repo already relies on supported environment variables and does not pass serve options explicitly, no code change may be required for those keys.

Other renames:

• serveHost -> serveOrigin
• streaming: "force" -> streaming: true
• streaming: "allow" -> streaming: true
• streaming: false stays false
• logLevel is removed; pass a logger such as new ConsoleLogger({ level })

createFunction Triggers

Triggers move into the first argument's options object.

// Old v3
inngest.createFunction(
  { id: "send-welcome" },
  { event: "user/created" },
  async ({ event, step }) => {}
);

// New v4
inngest.createFunction(
  { id: "send-welcome", triggers: [{ event: "user/created" }] },
  async ({ event, step }) => {}
);

Cron triggers move the same way:

inngest.createFunction(
  { id: "nightly-sync", triggers: [{ cron: "0 2 * * *" }] },
  async ({ step }) => {}
);

If a function is invoked only via step.invoke, it may be triggerless.

EventSchemas to eventType/staticSchema

Replace centralized EventSchemas with event-specific definitions.

import { Inngest, eventType, staticSchema } from "inngest";
import { z } from "zod";

export const userCreated = eventType("user/created", {
  schema: z.object({
    userId: z.string(),
    email: z.string().email(),
  }),
});

type InvoicePaid = {
  invoiceId: string;
  customerId: string;
};

export const invoicePaid = eventType("billing/invoice.paid", {
  schema: staticSchema<InvoicePaid>(),
});

Use event types consistently:

await inngest.send(userCreated.create({ userId, email }));

inngest.createFunction(
  { id: "on-user-created", triggers: [userCreated] },
  async ({ event }) => {}
);

await step.waitForEvent("wait-for-invoice", {
  event: invoicePaid,
  timeout: "7d",
});

Important: staticSchema expects a type, not an interface. Convert interfaces to type aliases when needed.

step.invoke

v4 no longer accepts raw string function IDs. Use an imported function reference or referenceFunction().

import { referenceFunction } from "inngest";

await step.invoke("run-report", {
  function: referenceFunction({
    appId: "analytics-app",
    functionId: "generate-report",
  }),
  data: { reportId },
});

If the target function is in the same codebase, prefer passing the imported function itself:

await step.invoke("run-report", {
  function: generateReport,
  data: { reportId },
});

Realtime Migration

v3 realtime used @inngest/realtime and middleware-injected publish. v4 realtime is native.

Replace:

• @inngest/realtime package
• realtimeMiddleware()
• handler args such as { publish }
• v3 React hooks such as useInngestSubscription()

With:

• channel definitions from inngest/realtime
• step.realtime.publish between steps
• inngest.realtime.publish inside an existing step.run
• subscription helpers/hooks from current v4 APIs

Use inngest-realtime for detailed patterns. Do not call step.realtime.publish from inside step.run; use inngest.realtime.publish there to avoid step-in-step behavior.

Parallelism and Checkpointing

v4 enables optimized parallelism and checkpointing by default.

Watch for Promise.race over steps. With optimized parallelism, Promise.race waits for all step promises to settle. If the repo relies on first-winner behavior, use group.parallel().

For serverless platforms, configure checkpointing maxRuntime slightly below the platform limit:

export const inngest = new Inngest({
  id: "my-app",
  checkpointing: {
    maxRuntime: "50s",
  },
});

On Vercel or similar frameworks, also set the route handler's max duration where the platform supports it.

Connect Changes

If the repo uses Connect:

• rewriteGatewayEndpoint is replaced by gatewayUrl.
• Connect may use worker-thread isolation. If integration issues appear, check

isolateExecution: false or INNGEST_CONNECT_ISOLATE_EXECUTION=false.

• Keep target URLs and signing/event keys in env vars.

Verification

Run checks in increasing confidence:

1. Package manager install/update.
2. Typecheck.
3. Unit/integration tests around migrated functions.
4. Start the app with INNGEST_DEV=1.
5. Run npx inngest-cli@latest dev and confirm function discovery.
6. Send one representative event and inspect the run.

If local dev-server verification is not possible, state exactly which static checks passed and what runtime verification remains.

Common Failure Messages

• "A signing key is required to run in Cloud mode": set INNGEST_DEV=1 for

local development or configure INNGEST_SIGNING_KEY for production.

• `Cls is not a constructor` on `/api/inngest`: likely v3

@inngest/realtime middleware in a v4 app. Remove the package and migrate to native realtime.

• `step.invoke` fails with string function ID: replace strings with

imported function references or referenceFunction().

• Type errors around schemas: replace EventSchemas with eventType() and

staticSchema().

• Unexpected `Promise.race` behavior: use group.parallel() for first-winner

step races or disable optimized parallelism only when necessary.

Anti-Patterns

• Mixing v3 realtime middleware with inngest@4.
• Passing signingKey, baseUrl, or signingKeyFallback to serve().
• Moving event trigger syntax but forgetting cron/invoke-triggered functions.
• Replacing EventSchemas with untyped string events everywhere.
• Hardcoding isDev: true in production-bound source.
• Leaving string IDs in step.invoke.
• Skipping typecheck after mechanical migration.