Technosignatures include (but are not limited to) evidence of electromagnetic transmissions of information, artificial heat and light, astroengineering projects (Dyson spheres and swarms, Matrioshka brains, stellar engines etc), asteroid or other space mining projects, and spacecraft.
When will technosignatures of non-human origin be detected for the first time?
By 'non-human origin,' this question refers to technosignatures that are not the result of human activity, or of the activity of any technology or 'lifeform' created by humans, including any artificial intelligence system or biological organism.
This question resolves as the date on which a competent and credible authority on astronomy and/or space exploration (such as NASA, ESA, ROSCOSMOS, CNSA, JAXA, SETI or similar) announces that, on the balance of probabilities (i.e. more than 50% likely), technosignatures of non-human origin have been discovered. This announcement qualifies for positive resolution only if it is still maintained after a year waiting period following the initial detection, unless the space agencies of the US, Russia, China and Europe all agree that the finding is genuine. Evidence of biosignatures alone will not be directly relevant to the resolution of this question.