SWE-Crafter: Scaling Executable Multilingual Software Engineering Data with Meta-Skill Agents

Software-engineering agents are increasingly expected to solve realistic repository-level tasks, but their training remains constrained by the limited availability of executable supervision beyond Python-centric repositories. Building such data across programming languages is difficult: repositories use different build systems, dependency managers, runtime assumptions, test interfaces, and failure modes, so separate language-specific pipelines are costly to reproduce and extend. We introduce SWE-Crafter, a unified agent-based framework for constructing executable multilingual SWE instances. SWE-Crafter keeps candidate mining, environment synthesis, fail-to-pass validation, and trajectory distillation in a shared pipeline, while language-specific construction knowledge is supplied through extensible skills induced from repository-level experience. These skills guide repository exploration and test-command synthesis while preserving repository-local evidence from documentation, manifests, CI files, and execution feedback as the final source of truth. Applying SWE-Crafter to eight programming languages yields 50,926 validated instances from 9,296 repositories and 68,851 distilled test-passing trajectories. Supervised fine-tuning on this resource produces SWE-Crafter-40B, which achieves 61.0% on SWE-bench Multilingual and 77.2% on SWE-bench Verified, showing that skill-guided construction provides scalable multilingual supervision for repository-level SWE agents.