The best code-embedding retriever returns a functionally broken near-clone at rank 1 in two thirds of queries.

ExecRetrieval builds a search pool containing the counterfactuals: 939 Python tasks, each with one execution-verified canonical implementation and up to four execution-verified buggy variants from a single targeted mutation. Across 23 dense embedding configurations plus BM25, the top hosted system reaches exec@10 = 1.00 but exec@1 = 0.331, and rank-1 misses are paired buggy variants 91.5-99.4% of the time on the four leading systems. The canonical scores below at least one paired distractor in 67-78% of queries. Any coding agent trusting a single top-1 embedding hit is being handed subtly wrong code most of the time.