- I put a debugger call in the test that was failing.
- Running the install command at that debug prompt and lo,
  the typing bug was staring me in the face:

```
Error: An exception occurred within a child process:
  TypeError: Parameter 'ref_type': Expected type T.nilable(String), got type Symbol with value :branch
Caller: /opt/homebrew/Library/Homebrew/vendor/bundle/ruby/3.3.0/gems/sorbet-runtime-0.5.11471/lib/types/private/methods/call_validation.rb:215
Definition: /opt/homebrew/Library/Homebrew/unpack_strategy.rb:102 (UnpackStrategy.detect)
```