Context: Large language model (LLM) agents are increasingly used as software and data-engineering assistants, yet evidence about locally deployable open-weight agents remains limited. Existing evaluations often emphasize textual responses, isolated code generation, or generic tool calls rather than the validity of complete engineering artifacts.Objectives: We evaluate whether local LLM agents can produce correct and reproducible data-engineering artifacts, quantify the effect of a closed-loop workspace condition, and examine trade-offs involving model scale, architecture, quantization, runtime, tool use, and failure behavior.Methods: We introduce a benchmark of fifteen tasks using mobility workflows as a domain-grounded testbed. Tasks cover data discovery, connector construction, transport-feed processing, semantic enrichment, feature engineering, validation, visualization, and reporting. Deterministic checkers assess generated scripts, tables, structured files, figures, and reports. Ten local model configurations are evaluated in one-shot and closed-loop workspace conditions, with five repetitions per model, mode, and task, yielding 1,500 scored attempts on a consumer-grade GPU.Results: Among models larger than two billion parameters, the workspace condition increases pass rates by 26.7--52.0 percentage points over one-shot generation. The strongest configuration reaches 85.3\% artifact-level success. A quantized 9-billion-parameter model reaches 69.3\% with an approximately 6.5~GB memory footprint. Gains are largest when intermediate artifacts expose errors that the agent can inspect and repair.Conclusion: Local open-weight agents can support a meaningful subset of software-intensive data-engineering work, but their reliability depends on model capability, task verifiability, and deterministic validation. The benchmark provides a reproducible method for evaluating complete agent configurations before they are adopted in engineering workflows.