My current character is going to side with the Brotherhood of Steel for endgame, but I am planning on doing as many Railroad quests as I can before I betray them, as well as getting Deacon's affinity to max (so in a way I am acting as an infiltrator). So far I have done Tradecraft, Boston After Dark, PAM's first DIA cache, the Augusta Safehouse quests (Butcher's Bill 1 and 2), Mercer Safehouse, and just last night completed Memory Interrupted. I have Tinker Tom's Weathervane quests to start, and have a quest called Concierge in my log. After completing Memory Interrupted, I returned to the RR HQ to hear Des talk about how the BoS are officially their enemy, but they will delay making an attack on the Prydwen until later.

So, now this makes me wonder: How far should I go with the RR quests before I can safely walk away without causing issues with either of the factions?

I'm pretty sure that you won't attack the BOS until after "Battle of Bunker Hill"

There is a quest Precipice of War with the Railroad that I believe will make the Brotherhood hostile without warning. However, getting to this point is a little tricky because in order to progress with the Railroad you also have to progress a questline with a certain other faction that will make the Brotherhood hostile towards you much earlier on. The last quest you'll be able to do with the Railroad is Underground Undercover, but only half of it, as you will not be able to complete it without progressing with that other certain faction that make the Brotherhood hostile. Besides, you wouldn't want to complete Underground Undercover anyway as it's completion leads directly to Precipice of War, which means hostile Brotherhood.


It's rather difficult doing both Railroad and Brotherhood quests because of how tied in the Railroad questline is with the certain other factions questline who make the BoS hostile earlier than the Railroad does.

I think you need to stop at Operation Ticonderoga, because it automatically activates Precipice of War. Or if you finish the objectives in Op. T, don't talk to Desdemona to turn in it. As Legion64 mentioned, you can start Underground Undercover, but won't be able to complete it if you want a BoS ending. It will stay open in your Pip-Boy, and then automatically fail later on.

For the BoS, the "point of no return" quest is Tactical Thinking. Once you start that, the RR will turn hostile.

Yeah, I did get to Tactical Thinking on my higher-level character but never proceeded with it because I planned on siding with the MM for that playthrough. The RR is more uncharted territory for me right now, and even if this info is in the Fallout wiki, I think it's useful to get the opinions of individuals.

Yeah, you should stop at Operation Ticonderoga, the quest itself can't be completed without Spoils of War/Mass Fusion, RR quest can't be completed without siding with the Institute. You can basically do all the RR quests before Spoils of War/Mass Fusion without worry about anything. You will never be asked to choose with the RR because you need to side with either the BoS or the Institute beforehand. Go nuts with the RR, but remember to get Ballistic Weave first before doing Blind Betrayal since PAM will be locked down by the BoS after that quest is completed.