OK. I was concerned about the separate discussion of "the oneworld flight on which the eligible customer is travelling departs" and "Connecting between oneworld marketed and operated flights:".

So is it a correct and complete statement to say:

You may bring a guest into the lounge (first-class, where available) if all of the following conditions are met:

1. You are travelling with oneworld (see below for various corner cases)
2. You are travelling in or connecting to/from First Class (see below for various corner cases)
3. You are travelling from the airport (i.e. origin or transit; not arriving at your final destination)
4. The guest is travelling on a oneworld-marketed and -operated flight (does not have to be the same flight as you)

I am thinking of the following corner cases:

• You have a direct flight and it is First Class domestic or First Class international <5 h -- access for you? For guest?
• You have a direct flight and it is oneworld-marketed but not oneworld-operated, or vice-versa -- access for you ("when you fly First Class or Business Class with any oneworld member airline" in general but for connections explicitly "an international flight marketed and operated by any oneworld carrier")? For guest?
• You have non-direct flights but no segment in which you travel First Class international >5 h (only First Class domestic or <5 h international) -- access for you? For guest? At which airport(s)?
• You are travelling from the airport but the guest is arriving at their final destination -- access for guest (it just says "travelling" not "departs")?

I'd say it's implicit that the two have to enter together (or at least the FC will have to go to the entrance to let the guest in), but where is it stated that the two have to leave together? I don't see this at https://www.oneworld.com/airport-lounges .