"We Never Fight": When Silence Isn't Harmony, It's a Deal

You tell people you never fight. You say it like proof. But one of you stopped bringing things up, and the other one was relieved, and now you live in a house where nothing is wrong and nothing is real. The quiet one learned that silence keeps the peace. The comfortable one learned that peace means no one is complaining. Both of you built a relationship around what you avoid.
There is a version of you that wants to say "this bothers me." There is a version of them that could hear it. But those two people never meet, because the cost of conflict got set too high, too early, by one of you, and the other agreed to the terms without reading them. You don't fight. You also don't talk, not about the things that would actually change something. The silence is not harmony. It's a deal you made without words.
The trait is conflict avoidance, on both sides
A conflict-free relationship usually runs on two low-Assertiveness people, or one who withdraws paired with one who prefers not to be challenged. Low Assertiveness makes raising a problem feel more dangerous than living with it, so grievances get filed away instead of aired, and the relationship optimizes for the absence of friction rather than the presence of honesty. It feels calm. It is actually the sound of two people slowly editing themselves down to the parts that don't cause trouble.
The fix is to lower the cost of conflict on purpose: treat a raised concern as maintenance rather than an attack, and make it safe to say "this bothers me" without it becoming a crisis. Real harmony includes disagreement handled well. What you have is peace by omission, and peace by omission means neither of you is fully in the room.
Where each of you sits on the Assertiveness facet that decides whether things get raised or buried is measured by the 30-facet OCEAN personality test in about 15 minutes, with domain results free, and a compatibility report shows whether your quiet is harmony or a deal made without words.