www/docs/server/adapters/fastify.md (2)

120-126: Reword to explicitly reference routerOptions and Fastify version

Tiny clarity tweak so the prose aligns with the snippet and deprecation context.

Apply:

- tRPC includes an adapter for [Fastify](https://www.fastify.io/) out of the box. This adapter lets you convert your tRPC router into a [Fastify plugin](https://www.fastify.io/docs/latest/Reference/Plugins/). In order to prevent errors during large batch requests, make sure to set the `maxParamLength` Fastify option to a suitable value, as shown.
+ tRPC includes an adapter for [Fastify](https://www.fastify.io/) out of the box. This adapter lets you convert your tRPC router into a [Fastify plugin](https://www.fastify.io/docs/latest/Reference/Plugins/). To prevent errors during large batch requests, set `routerOptions.maxParamLength` (Fastify ≥5.5) to a suitable value, as shown below.

---

163-165: Add a short compatibility note for Fastify <5.5

Given the ongoing transition and the PR description, consider a small “Compatibility” block with the legacy snippet to help users on older Fastify versions. Keeps the main path modern while reducing friction.

Append right after the code block:

+:::note Compatibility (Fastify <5.5)
+If you're on an older Fastify version (<5.5), configure `maxParamLength` at the top level:
+
+```ts title='server.ts (Fastify <5.5)'
+const server = fastify({
+  maxParamLength: 5000,
+});
+```
+Router options moved under `routerOptions` in Fastify 5.5 and will be removed from the top level in Fastify 6.
+:::

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

Learnt from: CR
PR: trpc/trpc#0
File: .cursor/rules/react-query-tests.mdc:0-0
Timestamp: 2025-09-05T15:16:01.751Z
Learning: Applies to packages/react-query/**/*.test.tsx : Create the tRPC React client with createTRPCReact<typeof appRouter>()