kamal setup fails on missing ed25519 gem dependency

[roscom]

rails 8.0.4
ruby 3.4.7

kamal setup yields:

/usr/lib/ruby/vendor_ruby/rubygems/specification.rb:1421:in rescue in block in activate_dependencies': Could not find 'ed25519' (~> 1.4) among 376 total gem(s) (Gem::MissingSpecError)

Relevant Gemfile.lock:

kamal (2.10.1)
activesupport (>= 7.0)
base64 (~> 0.2)
bcrypt_pbkdf (~> 1.0)
concurrent-ruby (~> 1.2)
dotenv (~> 3.1)
ed25519 (~> 1.4)
net-ssh (~> 7.3)
sshkit (>= 1.23.0, < 2.0)
thor (~> 1.3)
zeitwerk (>= 2.6.18, < 3.0)

Relevant gem env

RubyGems Environment:

• RUBYGEMS VERSION: 4.0.4
• RUBY VERSION: 3.4.7 (2025-10-08 patchlevel 58) [x86_64-linux]
• INSTALLATION DIRECTORY: /home/cb/.gem/ruby/3.4.7
• USER INSTALLATION DIRECTORY: /home/cb/.gem/ruby/3.4.0
• CREDENTIALS FILE: /home/cb/.local/share/gem/credentials
• RUBY EXECUTABLE: /home/cb/.rubies/ruby-3.4.7/bin/ruby
• GIT EXECUTABLE: /usr/bin/git
• EXECUTABLE DIRECTORY: /home/cb/.gem/ruby/3.4.7/bin
• SPEC CACHE DIRECTORY: /home/cb/.gem/specs
• SYSTEM CONFIGURATION DIRECTORY: /home/cb/.rubies/ruby-3.4.7/etc
• RUBYGEMS PLATFORMS:
  • ruby
  • x86_64-linux
• GEM PATHS:
  • /home/cb/.gem/ruby/3.4.7
  • /home/cb/.rubies/ruby-3.4.7/lib/ruby/gems/3.4.0