Fastify v5 support

[zapotinschii]

Do you plan to update this package for fastify v5?

'
npm error code ERESOLVE
npm error ERESOLVE could not resolve
npm error
npm error While resolving: fastify-zod@1.4.0
npm error Found: fastify@5.0.0
npm error node_modules/fastify
npm error fastify@"^5.0.0" from the root project
npm error
npm error Could not resolve dependency:
npm error peer fastify@"^4.15.0" from fastify-zod@1.4.0
npm error node_modules/fastify-zod
npm error fastify-zod@"^1.4.0" from the root project
npm error
npm error Conflicting peer dependency: fastify@4.28.1
npm error node_modules/fastify
npm error peer fastify@"^4.15.0" from fastify-zod@1.4.0
npm error node_modules/fastify-zod
npm error fastify-zod@"^1.4.0" from the root project
npm error
npm error Fix the upstream dependency conflict, or retry
npm error this command with --force or --legacy-peer-deps
npm error to accept an incorrect (and potentially broken) dependency resolution.
'

[stefano-8wave]

I'm having the same problem.

[VMBindraban]

I am running this fine with V5. I am using yarn though.

[stefano-8wave]

there is a need to update the package.json (peerDependencies) with latest version of fastify.

[MkLHX]

@elierotenberg ping

[frdwhite24]

i am also just running into this when upgrading from fastify v4 to v5, would be great to address it, thanks! for those that are struggling, you can use npm install --legacy-peer-deps to get past it. I figure this is relatively ok to do given it's been reported above it's working fine with v5, I'll report back here if I face any issues with doing this in the coming months.

[Ali-Aref]

any updates ?

[zapotinschii]

I suggest looking into alternatives, such as zod-build-json-schemas or fastify-type-provider-zod

[frdwhite24]

I'll report back here if I face any issues with doing this in the coming months.

I ended up migrating my entire API to fastify-type-provider-zod and it's working great.

[Ali-Aref]

I ended up using zod to json schema package which has over 7M npm weekly downloads 🥶.

import { z } from "zod";
import { zodToJsonSchema } from "zod-to-json-schema";

const mySchema = z
  .object({
    myString: z.string().min(5),
    myUnion: z.union([z.number(), z.boolean()]),
  })
  .describe("My neat object schema");

and inside the fastify route files or any other places you can

server.get("/", {
  schema: {
    response: {
      200: zodToJsonSchema(mySchema),  // <- just like this
    }
  }
}, myAwsomeController)

[EDM115]

Zod v4 now allows to create JSON schemas without any 3rd-party library.
see https://zod.dev/json-schema

edit : here's how I did it : https://edm115.dev/blog/2025/05/30/how-i-migrated-to-zod-4