Unable to upgrade the Tailscale GUI app, Error: Cask 'tailscale-app' definition is invalid

[xxyxxyxyx1]

Output of brew config

HOMEBREW_VERSION: 5.0.16-49-g0ac3954
ORIGIN: https://github.com/Homebrew/brew
HEAD: 0ac395449422b697db9936fd6793d7dd71b0adf7
Last commit: 3 hours ago
Branch: main
Core tap JSON: 05 Mar 09:11 UTC
Core cask tap JSON: 05 Mar 09:11 UTC
HOMEBREW_PREFIX: /opt/homebrew
HOMEBREW_CASK_OPTS: []
HOMEBREW_DISPLAY: /private/tmp/com.apple.launchd.7Cmt11BYF7/org.xquartz:0
HOMEBREW_DOWNLOAD_CONCURRENCY: 20
HOMEBREW_EDITOR: nvim
HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set
HOMEBREW_MAKE_JOBS: 10
HOMEBREW_NO_ENV_HINTS: set
HOMEBREW_SORBET_RUNTIME: set
Homebrew Ruby: 3.4.8 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/3.4.8/bin/ruby
CPU: deca-core 64-bit arm_firestorm_icestorm
Clang: 17.0.0 build 1700
Git: 2.53.0 => /opt/homebrew/bin/git
Curl: 8.7.1 => /usr/bin/curl
macOS: 15.7.4-arm64
CLT: 26.2.0.0.1.1764812424
Xcode: 26.3
Metal Toolchain: N/A
Rosetta 2: false

Output of brew doctor

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Description of issue

When I run brew upgrade tailscale-app, I get the following error:
Error: Cask 'tailscale-app' definition is invalid: 'conflicts_with' stanza failed with: Unknown key: :formula. Valid keys are: :cask

I do not understand this error message. I looked at tailscale-app.rb and at the output of brew info tailscale-app, and I did not find the word conflicts_with anywhere.

Relevant casks

tailscale-app

[botantony]

The cask had this stanza but it was remove half a year ago Homebrew/homebrew-cask@4e2077d

Can you try to uninstall it again with --verbose and --debug flags and send the output?

[xxyxxyxyx1]

Thank you for the suggestion.
Instead of running brew reinstall tailscale-app, I did brew uninstall tailscale-app followed by brew install tailscale-app. This time it worked. My settings were retained, I did not have to redo the tailscale setup.
I did not realize that reinstall was different from uninstall + install.