Does a split card's color identity in Commander include both halves of the card?

In Commander, a card's color identity is determined by every mana symbol and color indicator appearing anywhere on the card, including all text boxes and mana costs. For split cards, this means both halves are examined together to form a single color identity (CR 903.4, CR 202.3).

CR 202.3 explicitly states that the color identity of a card is the combination of colors from its mana cost and any mana symbols in its rules text, and CR 712.4 clarifies that split cards have two sets of characteristics but are treated as a single card. All mana symbols on both halves contribute to the overall color identity.

This is true regardless of which half you intend to cast. If one half has a mana symbol of a color your commander doesn't share, the entire card is illegal in your deck — you can't include it just because you only plan to cast one side.

Concrete example: The split card Fire // Ice has a red mana symbol (Fire) and a blue mana symbol (Ice). Its color identity is {R}{U}. You cannot include it in a mono-red Commander deck, even if you only ever intended to cast Fire, because the blue mana symbol on Ice is part of the card's full color identity.

This applies equally to aftermath, fuse, and other split card variants — all mana symbols across every section of the card contribute to color identity under CR 202.3 and CR 903.4.