HumanLoop
Prompt engineering and eval platform, sunset after Anthropic acqui-hire.
About
HumanLoop was an LLM development platform for managing prompts, datasets, evaluations, and production observability. AI product teams at companies like Duolingo and Gusto used it to version prompts, run evaluations against datasets, capture production logs, and systematically improve LLM features. It was widely regarded as the leading dedicated prompt-engineering workbench of the 2023-2025 era.
This is a historical entry. In August 2025 Anthropic acqui-hired the three co-founders and roughly a dozen engineers; billing stopped July 30, 2025, and the platform, API, and UI went permanently offline on September 8, 2025, with all user data deleted. Anthropic did not acquire the assets or IP. The team's DNA lives on as the Workbench and Evaluations tabs inside the Anthropic Console.
It is included because HumanLoop defined the prompt-ops category that LangSmith, Braintrust, PromptLayer, and others now serve. There is no recovery path for old accounts; teams needing this workflow should evaluate the Anthropic Console, LangSmith, Braintrust, or open-source Promptfoo.
What it can do
- Versioned prompt management with collaboration (retired)
- Dataset-based evaluations and evaluators (retired)
- Production log capture and observability (retired)
- Prompt endpoints callable from production (retired)
- Migration: .prompt files importable into newer workbenches
Setup
Sunset: platform offline since September 2025. Evaluate Anthropic Console, LangSmith, Braintrust, or Promptfoo instead.
Prerequisites
None; the service no longer exists.
Use cases
Works with
Trust score — 6/10
Scored 6/10 (metrics tier, metrics-v1). Evidence: Verified via vendor site/docs/GitHub and reputable coverage, wave 74; Trending score 58/100 from researcher assessment.
Sources
Every fact above was checked against these sources. Where a claim comes from the provider and couldn't be independently verified, the text says so.