DNS override fails in iOS 27 due to Connectivity Assist

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Active
Tech stack
ios

Research direction

No source files, tests, or entry points are named. Start by reproducing the DNS override failure on iOS 27.0.0 with Tailscale 1.102.4 and review the attached bug report; done means the override remains in use after extended normal use.

Written by the indexing model from the issue text.

Description

bug dns OS-ios
What is the issue?

I have an override DNS server set for my tailnet. New on my iPhone updated to iOS 27, it starts off using the override DNS server, but after an hour of normal use, the override server stops working.

Steps to reproduce
  1. Set an override DNS server on your tailnet.
  2. Reboot your phone. Watch your server be used for an hour or so.
  3. Eventually discover that your override DNS server is no longer used.
Are there any recent changes that introduced the issue?

iOS 27 is a notable recent change, though perhaps maybe a Tailscale update broke it.

OS

iOS

OS version

iOS 27.0.0

Tailscale version

1.102.4

Other software

No response

Bug report

BUG-dcc84a5e6f313a3c018dd5ea26dad506e6ac15f0d342305384a5a57ce171e1a1-20260917032959Z-a009ecfe6dadae27

Dominant language
Go
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Avg merge
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Merged PRs (30d)
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