Wood stove firebox

This is at the top of the firebox in a wood stove. Can anyone help me with the correct terminology for addressing this situation? Thanks.

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The firebox is badly cracked and should not be used.

Joe nailed it…that should be all you need…imo

P.S.

A wood burning stove prevents an examination of the fireplace and flue, so we recommend a thorough examination of the fireplace and chimney by a specialist.