VECTRA: Verified Episodic Control for Repository-Level Code Translation

Repository-level code translation is a long-horizon engineering process that requires establishing a coherent target architecture and cross-file interfaces, reconstructing build configurations, and preserving program behavior. Modern coding agents can perform much of this work, but effective execution also requires deciding which intermediate repository states to retain, which failures to address next under a limited budget, and what knowledge to carry across sessions. We present VECTRA, a control framework that advances repository translation through a sequence of verifier-admitted states. Four coordinated mechanisms form its execution loop: a holistic bootstrap establishes the overall target structure; a frontier scheduler turns current build and test evidence into bounded translation missions; a verification gate accepts candidate changes or rolls them back; and a persistent translation ledger carries verified facts and cross-language decisions across fresh coding-agent episodes. The underlying coding agent remains unmodified and can use its usual tools and subagents. Across 13 translation directions in RepoTransBench, VECTRA achieves an average success rate of 67.9%, outperforming the evaluated agent-based baselines. Ablation results show that removing any of the four mechanisms reduces the success rate. These results suggest that explicit control over intermediate repository states and translation progress can complement advances in code generation.