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Inconsistent hydration: some tags in the head are duplicated, eg. application/ld+json #6569
Description
Which project does this relate to?
Start
Describe the bug
Some tags appear to be duplicated during hydration, even though the server has sent them correctly if we look at them with view-source:[url]
Your Example Website or App
https://stackblitz.com/edit/github-zpekad3w?file=src%2Froutes%2F__root.tsx
Steps to Reproduce the Bug or Issue
- run
npm run build - start production server
npm run start - open production URL
- check
elementstab on browser dev tools, the seeapplication/ld+jsonscript
It looks like there are 2 even though I only inserted 1. The duplicate tag appears without content.
Expected behavior
Hydration should produce matching elements according to the head content sent by the server.
Screenshots or Videos
No response
Platform
- Router / Start Version: 1.157.18
- OS: Linux
- Browser: Chrome
- Browser Version: 144.0.7559.110
- Bundler: vite
- Bundler Version: 7.3.1
Additional context
No response
Activity
Ammar123890 commentedon Feb 8, 2026
I'm seeing this exact same behavior in React Router v7, and looking at the source here in TanStack Router, it seems to share the same root cause.
In
packages/router/src/HeadContent.tsx(specifically around theScriptorMetacomponent rendering logic), the framework uses the stringified content or a simple index as the Reactkeyduring iteration.When using a CDN like Cloudflare (Auto-Minify) or when dealing with special character encoding (e.g., Arabic/Unicode), the server-rendered string often differs slightly from the client-hydrated string:
Server:
<script>...{"foo":"bar"}...</script>(Minified/Encoded)Client:
<script>...{ "foo": "bar" }...</script>(Standard formatting)React sees
Key(Server) !== Key(Client), assumes the server node is foreign, leaves it in the DOM (the duplicate), and appends a new one.We bypassed the framework's head management entirely for JSON-LD and moved the
<script>tag directly into the Component BodyThis forces React to manage the script lifecycle natively as part of the component tree, completely avoiding the hydration mismatch in the
<head>.AlexandreSi commentedon Feb 9, 2026
Hi,
I have a similar issue: I have the empty script tag and nothing inside, but the correct ld+json tag is nowhere to be found.
Ammar123890 commentedon Feb 10, 2026
@AlexandreSi
Can you share some snapshots of your code?
AlexandreSi commentedon Feb 10, 2026
Hi @Ammar123890,
Thank you for your response.
I created a new issue with all the details here: #6627