The platform behind 100+ Fortune 500 LLM apps

Vellum is the LLM development platform built for teams shipping production AI features. It bundles prompt engineering (a Notion-like editor for prompts), evaluation (run 1,000 test cases side by side, score with LLMs), deployment (one-click to API), and observability (log every request, debug regressions). Used by Ramp, Webflow, and Samsara.

Who it's for: AI engineering teams at companies shipping 5+ LLM features to production. Less suited for solo developers or weekend hackers — the value is in the team workflows.

Key features

Prompts Collaborative prompt editor

Notion-style prompt editor with versioning, branching, comments, and review workflows. Track every change. Roll back when an A/B test fails.

Evals LLM-as-judge evaluation

Run 1,000+ test cases across Claude, GPT, Gemini, Llama in parallel. Use GPT-4o or Claude to score outputs. Catch regressions before production.

Deploy One-click API + SDKs

Turn your prompt + workflow into a versioned API endpoint. SDKs for Python, TypeScript, Go. Latency, cost, and error rate tracked per version.

Observe Production observability

Log every production request with inputs, outputs, latency, cost, and feedback. Filter to debug user-reported bugs. Sample for fine-tuning datasets.

The honest take

✓ What works

End-to-end platform — prompt → eval → deploy → observe in one tool
LLM-as-judge evals save weeks of manual scoring
Versioning and rollback is genuinely production-grade
SOC 2 Type II, HIPAA-eligible — passes enterprise procurement
Real customers shipping real revenue (Ramp, Webflow)

✗ What doesn't

Expensive — $300/mo minimum for production deployments
Overkill for solo builders or weekend projects
UI can feel slow on very large prompt workspaces (1,000+ prompts)
Vendor lock-in — your prompts live in Vellum's format
Free tier is read-only — no production deploys without paid plan

Verdict

Vellum is the closest thing to "Vercel for LLM apps" in 2026. If your team is past the prototype stage and shipping multiple LLM features to production, the time saved on prompt versioning, evals, and observability is worth the $300/mo easily. If you're still prototyping solo, stick with LangSmith, Helicone, or just your terminal — Vellum's value is in the team workflows.

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