Pluripotential solutions versus viscosity solutions to complex Monge-Amp{\`e}re flows

We compare various notions of weak subsolutions to degenerate complex Monge-Amp{`e}re flows, showing that they all coincide. This allows us to show that the viscosity solution coincides with the envelope of pluripotential subsolutions. Dedicated to Duong Hong Phong on the occasion of his 65th birthday.