[Next.js] "effects_UNSTABLE" => Warning: did not match. Server, Client

Description

Contributor guide

Tech stack

javascripttypescriptreactnextjsnodejs

Domain

frontend

Issue type

bug

DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.

3

Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.

1-2 days

Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.

stale

ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.

needs investigation

Prerequisites

ReactNext.jsRecoilServer side rendering

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

25

Research direction

Investigate the Recoil effects UNSTABLE API and its interaction with Next.js server side rendering hydration warnings. Look at the Recoil source code, particularly the effects implementation in the core module (e.g., packages/recoil/core/effects.js). Check if there are any known issues or documentation about effects and hydration. The bug report lacks a minimal reproduction, so a good first step would be to create a simple Next.js app using effects UNSTABLE to reproduce the warning and then identify the root cause.