Pick Inspect AI if
eval / safety teams who will run Inspect locally at $0 (you bring model API keys) — not Promptfoo first unless they want a YAML CI red-team harness.
Read the Inspect AI pageInspect AI vs Phoenix
Our take
Pick Inspect AI if you're on a eval / safety team who will run Inspect locally at $0 (you bring model API keys) — not Promptfoo first unless they want a YAML CI red-team harness. Pick Phoenix if you're on a agent team who will self-host Phoenix for $0 (uvx arize-phoenix serve) and only open Arize AX when they want a managed cloud.
Best for
Inspect AI A research eval you can inspect at $0
Phoenix See why an agent failed and prove a fix
Free plan
Inspect AI $0 · local CLI + log viewer. You pay model inference and machines
Phoenix $0 · local / Docker / Kubernetes. You bring compute. Homepage: uvx arize-phoenix serve
Lowest paid
Inspect AI Not published by the vendor
Phoenix AX Pro $50/mo
Runs where
Inspect AI Hosted
Phoenix Hosted
Watch out
Inspect AI $0 is the toolkit, not the model bill
Phoenix ELv2, not Apache
Last checked
Inspect AI 2026-10-27 · inspect.aisi.org.uk
Phoenix 2026-10-27 · arize.com/pricing
Which one, then?
Pick Phoenix if
agent teams who will self-host Phoenix for $0 (uvx arize-phoenix serve) and only open Arize AX when they want a managed cloud.
Read the Phoenix page