nextjs - ✅(Solved) Fix [Bug] Content-Type text/x-component does not have charset=utf-8 encoding [1 pull requests, 1 participants]

nextjs2026-03-26 11:51:27

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vercel/next.js#91942•Fetched 2026-04-08 01:35:37

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krystofmatejka

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krystofmatejka

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Root Cause

I would expect that the server actions will return a correct encoding as other text based responses. This cannot be patched in proxy because the content type header is set after the proxy.

Fix Action

Fix / Workaround

I would expect that the server actions will return a correct encoding as other text based responses. This cannot be patched in proxy because the content type header is set after the proxy.

PR fix notes

PR #91957: fix(rsc): add charset=utf-8 to text/x-component Content-Type header

Repository: vercel/next.js
Author: sleitor
State: open | merged: False
Link: https://github.com/vercel/next.js/pull/91957

Description (problem / solution / changelog)

What

RSC flight responses were missing the charset=utf-8 encoding declaration in their Content-Type header. HTML responses use text/html; charset=utf-8 and JSON responses use application/json, but RSC responses only set text/x-component — making it impossible for proxies and middleware to reliably patch the Content-Type downstream.

Why

The RSC_CONTENT_TYPE_HEADER constant is used for two different purposes:

Setting the response Content-Type header (server-side)
Detecting RSC responses via startsWith() on incoming headers (client-side)

These had conflicting requirements — the set value needs ; charset=utf-8, but the detection pattern should match the base MIME type to handle both old and new cached responses.

How

Add RSC_CONTENT_TYPE_HEADER_FULL = 'text/x-component; charset=utf-8' for use when setting response headers
Use RSC_CONTENT_TYPE_HEADER_FULL in FlightRenderResult and RenderResult.fromStatic() calls that set the Content-Type response header
Keep RSC_CONTENT_TYPE_HEADER = 'text/x-component' for client-side detection and routes manifest (infra compatibility)
Update the cached contentType comparison to startsWith() to handle both old cached values (without charset) and new ones (with charset)

Fixes #91942

Changed files

packages/next/src/build/templates/app-page.ts (modified, +4/-3)
packages/next/src/client/components/app-router-headers.ts (modified, +2/-0)
packages/next/src/server/app-render/flight-render-result.ts (modified, +3/-3)
packages/next/src/server/render-result.ts (modified, +3/-2)

Code Example

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Enterprise
  Available memory (MB): 65202
  Available CPU cores: 20
Binaries:
  Node: 24.4.0
  npm: 11.4.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.1.5 // No Next.js version data was found.
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: standalone

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Link to the code that reproduces this issue

https://codesandbox.io/p/sandbox/github/vercel/next.js/tree/canary/examples/reproduction-template

To Reproduce

start next.js server
invoke server action
inspect the response headers
content-type=text/x-component won't have charset=utf-8 encoding

Current vs. Expected behavior

I would expect that the server actions will return a correct encoding as other text based responses. This cannot be patched in proxy because the content type header is set after the proxy.

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Enterprise
  Available memory (MB): 65202
  Available CPU cores: 20
Binaries:
  Node: 24.4.0
  npm: 11.4.2
  Yarn: N/A
  pnpm: N/A
Relevant Packages:
  next: 16.1.5 // No Next.js version data was found.
  eslint-config-next: N/A
  react: 19.2.4
  react-dom: 19.2.4
  typescript: 5.9.3
Next.js Config:
  output: standalone

Which area(s) are affected? (Select all that apply)

Server Actions

Which stage(s) are affected? (Select all that apply)

Other (Deployed)

Additional context

I'm willing to send a PR if you confirm that this should be fixed.

extent analysis

Fix Plan

To fix the issue of missing charset=utf-8 encoding in the Content-Type header for server actions, you can manually set the header in your Next.js server action.

Here are the steps:

Identify the server action that is returning the text/x-component content type.
Set the Content-Type header with the charset=utf-8 parameter.

Example code:

import { NextApiRequest, NextApiResponse } from 'next';

const serverAction = async (req: NextApiRequest, res: NextApiResponse) => {
  // Your server action code here

  // Set the Content-Type header with charset=utf-8
  res.setHeader('Content-Type', 'text/x-component; charset=utf-8');

  // Return the response
  res.status(200).send('Your response data');
};

export default serverAction;

Verification

To verify that the fix worked, you can inspect the response headers of the server action using your browser's developer tools or a tool like curl. The Content-Type header should now include the charset=utf-8 parameter.

Example curl command:

curl -I https://your-domain.com/server-action

Look for the Content-Type header in the response:

Content-Type: text/x-component; charset=utf-8

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#prompt template #agent execution #callback error #memory management #API rate limit

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nextjs - ✅(Solved) Fix [Bug] Content-Type text/x-component does not have charset=utf-8 encoding [1 pull requests, 1 participants]

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Root Cause

Fix Action

Fix / Workaround

PR fix notes

PR #91957: fix(rsc): add charset=utf-8 to text/x-component Content-Type header

Description (problem / solution / changelog)

What

Why

How

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Fix Plan

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nextjs - ✅(Solved) Fix [Bug] Content-Type text/x-component does not have charset=utf-8 encoding [1 pull requests, 1 participants]

Recommended Tools

GitHub issue graph ai analysis

Root Cause

Fix Action

Fix / Workaround

PR fix notes

PR #91957: fix(rsc): add charset=utf-8 to text/x-component Content-Type header

Description (problem / solution / changelog)

What

Why

How

Changed files

Code Example

Link to the code that reproduces this issue

To Reproduce

Current vs. Expected behavior

Provide environment information

Which area(s) are affected? (Select all that apply)

Which stage(s) are affected? (Select all that apply)

Additional context

extent analysis

Fix Plan

Verification

Still need to ship something?

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