Ex post opportunism threatens agreements after relation-specific investments are sunk.

Evidence

My concern here is less with the terms of the original bargain than with the possibility of ex post opportunism: either reneging on the agreement or using the occasion of unanticipated contingencies to try to shift the distribution of joint profits in one’s favour. — Diego Gambetta, Trust - Making and Breaking Cooperative…, 2540

Categorization

• DEFINE: Precise definition of ex post opportunism — reneging or exploiting unforeseen contingencies to shift profit distribution.
• XREF: Directly names the opportunistic-behavior constraint Hardin argues trust institutions must observe; the doctor’s wife in Saramago enforces exactly this against the blind.