The disclosure describes techniques for joining a first part including a ceramic or a CMC and a second part including a ceramic or a CMC using brazing. A technique may include positioning a filler material in a joint region between the first and second parts and a metal or alloy on a bulk surface of the filler material. The metal or alloy may be locally heated to melt the metal or alloy, which may infiltrate the filler material. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts. Another technique may include depositing a powder that includes the filler material and the metal or alloy in the joint region. Substantially simultaneously with depositing the powder, the powder may be locally heated. A constituent of the molten metal or alloy may react with a constituent of the filler material to join the first and second parts.