Agentless is an agentless method for automatically resolving software development issues. It addresses each problem through three stages: localization, repair, and patch validation. Agentless utilizes a hierarchical process to locate failures down to specific files, related classes or functions, and fine-grained edit locations. It then samples multiple candidate patches based on these locations and selects regression tests to run, generating additional reproduction tests to replicate the original error. The results of these tests are used to re-rank all remaining patches to select a submission. Agentless is currently the top-performing open-source method on SWE-bench lite, with 82 fixes and a resolution rate of 27.3%, averaging a cost of $0.34 per problem.