DeepEval

Programming, not prompting: optimize the whole pipeline.

DSPy introduced programming models for LLM pipelines — declarative modules whose prompts and weights are optimized against metrics. Its optimizer-first philosophy reshaped how production harnesses treat prompts.

Open-source LLM engineering platform: traces, evals, prompts.

Langfuse is the open-source observability layer for LLM apps — tracing, prompt management, datasets, evals and cost tracking — deployable self-hosted or as a cloud.

The TypeScript framework for production agents.

Mastra is a full TS-native agent framework — workflows, tool calling, RAG, evals and a dev playground — that has become the default choice for JavaScript teams building agent backends.