Wayline Pact
Wayline Pact (development) in the Stellaris encyclopedia: Wayline Pacts are Diplomatic Pacts signed between a Nomadic Empire and another empire. These agreements allow both Empires to benefit from the Wayline Modifiers propagated along the Wayline.
Wayline Pact in the game's words
The encyclopedia entry as the game shows it in its tooltips; underlined words open their own entry or page here.
Wayline Pacts are Diplomatic Pacts signed between a 
Nomadic Empire and another empire. These agreements allow both Empires to benefit from the 
Wayline Modifiers propagated along the Wayline.
Additionally, when signed between a Nomadic Empire and a 
Settled Empire, any Diplomatic Penalties caused by the Wayline are ignored.
Entries that mention Wayline Pact
More in Development
Source: common/game_concepts (concept_wayline_pact, also concept_wayline_pacts) and localisation/english, Stellaris Cygnus v4.5.2 (9776).