Will the US and Iran sign a new peace agreement by September 30, 2026?

YES if and only if by September 30, 2026 (23:59 UTC):

The US and Iran sign a final, legally binding peace treaty;

The full signed document (or its official English/Farsi text) is published on whitehouse.gov, state.gov, president.ir, or mfa.gov.ir;

The publication includes images of the signatures or an explicit statement by both governments that the document is official and in force.

Any unsigned, oral, provisional, or unpublished agreement → NO.