What constructive discharge means, and the two things you must prove
A resignation normally ends the wage claim: you chose to leave, so the employer does not owe you the paycheck you walked away from. Constructive discharge is the exception. The Supreme Court stated the standard in Pennsylvania State Police v. Suders (2004): working conditions so intolerable that a reasonable person in the employee’s position would have felt compelled to resign. The test is objective. It asks what a reasonable person would have endured, not how badly you felt, and it sits above the ordinary hostile-environment threshold, an aggravated case in which resignation was a fitting response. Green v. Brennan (2016) restated the claim as two elements: the intolerable conditions, and the fact that you actually resigned because of them.
The second thing to prove is why the conditions existed. Constructive discharge is not a freestanding claim. It supplies the adverse-action element inside a claim that already has an unlawful motive at its center: discrimination because of a protected characteristic, retaliation for complaining about discrimination or requesting an accommodation, or interference with protected leave under the FMLA. A miserable job with no illegal motive behind it is a reason to quit, not a lawsuit. Once the illegal motive is proven, quitting no longer forfeits the remedies a firing would have carried.
Some courts add a third question: whether the employer intended to force you out, or could reasonably foresee that its conduct would. Green left that open and the circuits are split, so assume you will have to show the employer knew the conditions were intolerable and let them stand. A written complaint does that, and it answers the argument, which courts often accept, that a reasonable person would have tried to fix the problem before quitting.