Verifier‑guided self‑repair conditions a model on feedback from a failed attempt before it retries, without updating weights.\ \ Prior work reported two seemingly contradictory findings: verifier feedback can improve repair of failures, yet self‑repair offers little to no advantage over independent resampling.\ \ To reconcile this, we conducted controlled one‑step experiments in the Lean theorem‑proving environment. We fixed the preceding failure and varied three factors: whether the failed proof is shown to the model, whether the compiler error corresponds to that failure, and whether a retry instruction is provided.\ \ We evaluated a frozen Qwen3.6‑27B (a general‑purpose model) and DeepSeek‑Prover‑V2‑7B (a specialized prover) on challenging MiniF2F problems.\ \ Two opposing effects emerged. Showing the model its failed predecessor reduced success rates sharply and caused heavy copying of the predecessor, while for Qwen adding the attempt’s compiler error recovered the loss to the level of using the diagnostic alone. Replacing the predecessor with a failed proof from another theorem largely removed the degradation for both models; for Qwen, substituting the diagnostic with an error from a different problem substantially reduced recovery. Without the failed proof, correct diagnostics showed no advantage over wrong‑diagnostic controls on either model. The failed‑proof penalty persisted with and without the retry instruction, whereas Qwen’s diagnostic recovery was weaker without it.\ \ In sequential experiments covering 11 problems and 64 attempts, Qwen retained a correct‑diagnostic benefit within failed‑proof histories, while DeepSeek‑Prover showed no discernible recovery. No tested one‑step feedback condition outperformed instruction‑only resampling, and a 64‑attempt sequential repair with failed proofs and correct diagnostics did not yield an advantage under equal token budgets.\ \ Thus, verifier feedback can improve repair, but it does not overcome the performance loss incurred by conditioning on a failed attempt.\ \ Review