From Archon Arcana - The KeyForge Wiki
The cards in each player’s discard pile are open information, and may be referenced at any time.
The order of cards in a player’s discard pile is maintained during play, unless a card ability causes this order to change.
When a player runs out of cards in their deck and is required to draw, that player shuffles their discard pile to create a new deck.
—KeyForge Master Rulebook v17 April 2023