Static cached pages contain broken HTML

[robdekort]

Bug description

This seems to happen again: #7033. I've seen it on two projects now (both multisite). The first time I noticed it reappear was on September 16th, 2025. But of course, it could've been before that.

The nasty thing about this issue is that you don't really have a way of knowing and it looks pretty bad.

Downgraded a project to 5.20 because I noticed some lock changes in 5.21 (#10607). Perhaps those a related. Just a guess though.

How to reproduce

Wish I knew. Happy to share a repo though from the project where it happens.

Logs

No response

Environment

Environment
Laravel Version: 11.23.4
PHP Version: 8.2.23
Composer Version: 2.7.9
Environment: staging
Debug Mode: OFF
Maintenance Mode: OFF
Timezone: Europe/Amsterdam
Locale: en

Cache
Config: CACHED
Events: NOT CACHED
Routes: CACHED
Views: CACHED

Drivers
Broadcasting: log
Cache: file
Database: sqlite
Logs: stack / single
Mail: smtp
Queue: redis
Session: file

Livewire
Livewire: v3.5.6

Statamic
Addons: 7
Sites: 3 (English, Dutch, German)
Stache Watcher: Disabled (auto)
Static Caching: full
Version: 5.25.0 PRO

Statamic Addons
jonassiewertsen/statamic-livewire: 3.8.0
ryanmitchell/statamic-translation-manager: 2.0.0
stillat/relationships: 2.2.1
studio1902/statamic-peak-browser-appearance: 3.5.0
studio1902/statamic-peak-commands: 8.8.1
studio1902/statamic-peak-seo: 8.16.0
studio1902/statamic-peak-tools: 6.3.2

Installation

Starter Kit using via CLI

Additional details

No response

[robdekort]

I've checked all pages of my own site after the downgrade to 5.20 and I didn't see any broken cached pages. It doesn't prove much, but it could be a pointer.

[duncanmcclean]

I've just taken a quick look at this and I was able to reproduce the issue (I installed spatie/fork and made 10 requests to a page at once):

Essentially, it'll only happen if multiple requests are made to an uncached page at the same time. I'm guessing it's because there are multiple things trying to write to the same file at the same time.

I don't think it's related to #10607 - I was able to reproduce after rolling back that change.

[robdekort]

Nice find. And, I'm glad to learn at least some of my projects get concurrent requests 🤣.