GARLH4 establishes a competitive hierarchy to regulate NL synapse-type preference. Under physiological conditions (top), neuroligin 2 (NL2) acts as the dominant partner for inhibitory synapses. Because NL2 preferentially assembles with the GARLH4-containing GABA_AR complex, it effectively outcompetes other isoforms, predominating the inhibitory sites and segregating neuroligin 1 (NL1) to excitatory synapses with NMDARs and PSD-95. In the absence of NL2 (deletion or deficiency [NL2 in grey]; bottom), this competitive hierarchy is removed, enabling NL1 to assemble with GARLH4/GABA_AR complexes and redistribute toward inhibitory postsynaptic sites. This illustrates that NL localization can be a tunable outcome of stoichiometry and competition rather than a fixed address label. NMDAR, NMDA receptor; Nrxn, neurexins; PSD-95, postsynaptic density-95.