Eval Frameworks

Evaluation frameworks provide standardized tooling for defining test cases, running them against agent systems, and comparing results across different configurations of prompts, models, and tools. Key frameworks include Promptfoo (open-source CLI tool for comparing prompt variations), Braintrust (end-to-end eval platform with trace analysis), and LangSmith (eval and observability integrated into the LangChain ecosystem). These frameworks handle the plumbing that makes eval-driven development practical — test case management, parallel execution, statistical comparison, regression detection, and human-in-the-loop review for ambiguous outputs. The choice of eval framework shapes your entire quality improvement loop because it determines how easily you can iterate on prompts and measure the impact of changes. This concept connects to eval-driven development for the practice these tools enable, quality metrics for defining what frameworks should measure, agent benchmarks for standardized evaluation suites, and trace analysis for the debugging data that eval frameworks capture.