also: しゃんしゃんたいかい
noun
rigged convention; prearranged meeting
Refers to a convention or meeting where the outcome is decided in advance, often with a sense of sham proceedings. The term derives from the onomatopoeia しゃんしゃん, suggesting the clapping of hands in a perfunctory or orchestrated manner.
See also: しゃんしゃん
その株主総会はシャンシャン大会で、質問もなくすぐに終わった。
The shareholders' meeting was a rigged convention, ending quickly without any questions.
出来レース refers to a race or competition whose outcome is fixed, while シャンシャン大会 specifically describes a convention or meeting that is a mere formality.
From しゃんしゃん (onomatopoeia for clapping or a bell ringing) + 大会 (convention). The clapping sound suggests a perfunctory, orchestrated approval process.