LangSmith vs ProofHound

LangSmith is a commercial agent-engineering platform for building, evaluating, deploying, monitoring, and improving AI agents. It supports offline evaluations on curated datasets and real-time scoring of production interactions. Evaluation methods include human review, heuristic checks, LLM-as-judge evaluators, pairwise comparisons, and custom Python or TypeScript evaluators. Annotation queues route runs to subject-matter experts for feedback that can calibrate evaluations, improve prompts, or augment datasets. The Playground compares prompt versions or model providers, and LangSmith chat can auto-improve prompts. Observability includes agent and retrieval tracing, token and general cost tracking, trajectory monitoring, online evaluations, and webhook or PagerDuty alerts. Traces can arrive through SDKs or an API from LangGraph, custom Python, or other stacks; SDKs are listed for Python, TypeScript, Go, and Java. Hosting ranges from cloud to hybrid and self-hosted Enterprise options. The Developer plan costs nothing, Plus costs $39 a month, and Enterprise pricing is custom.

ProofHound is a prompt-optimization platform for LLM classification work, available through an API, self-hosted deployment, or the web. It examines error cases, iterates prompts, validates outputs, and provides controlled deployment and rollback. Dataset uploads accept CSV, TSV, JSONL, JSON arrays, and ZIP files, with field mapping in the interface. Optimization can target overall accuracy or category measures such as recall for high-risk categories and precision for error-prone classes. Immutable prompt versions retain variable configurations, output rules, and differences between revisions. Experiment records include datasets, model configurations, sample judgments, and overall and category metrics. Release controls include gray traffic, A/B testing, full rollout, and one-click rollback. Connections include the web UI, webhooks, API tokens, and MCP. Customers supply their own model provider, and ProofHound says model calls are not charged. A free plan is listed at free, while self-hosted open source is also free.