Leaving a job without burning it down

Whatever the contract says, plus a written handover that outlives you: runbooks, access list, the three things that break at 3am. Extending the notice period rarely helps; writing things down always does.

Offer a substitute rather than a refusal: a take-home you have already done, a walkthrough of public work, or pair debugging on their codebase. Companies that decline all three have told you something useful about how they work.