✓01
Genuinely free and open source, with a credible backer (NVIDIA / OSAIA)
SENTINEL VS PERPLEXITY
Sentinel vs
numbat.
Free, open-source local agent-activity monitor
numbat is Sentinel's closest and most credible competitor. It does most of what Sentinel v1 does — local hooks, normalized event streams, risk rules, opt-in blocking — for free, with real backing from NVIDIA and the Open Secure AI Alliance. We're not going to pretend it doesn't exist or that Sentinel is technologically ahead of it on core monitoring.
| Sentinel | numbat (Perplexity) | |
|---|---|---|
| Category | AI agent monitoring — early-access v1 prototype | Local developer-endpoint agent monitor |
| Monitoring | Desktop harnesses and browser agents: shell, files, network, browser actions | Observes Claude Code, Codex, Cursor, OpenClaw, OpenCode, and more via local hooks, OTLP/HTTP logs, and on-disk session artifacts. Normalizes everything into shell, file, network, and MCP/tool events. |
| Skill / MCP scanning | Yes — flags risky instructions before you pull a skill | Partial — it sees MCP tool calls as events, but it isn't a dedicated pre-run scanner for skills the way a SKILL.md scanner is. |
| Blocking / enforcement | Not yet — v1 is observe and alert; ask-and-approve gating is v2 | Opt-in. Monitor-only by default, with 52 built-in detection rules across 11 behavior categories (secret access, privilege escalation, data exfiltration, lateral movement) written as CEL expressions. |
| Individual tier | Planned free tier for individual developers | Free, open source, self-hosted — no paid tier needed for individuals. |
| Deployment | Early-access prototype, hosted at app.explainx.ai | Single Go binary. Backed by NVIDIA and the Open Secure AI Alliance; ~961 GitHub stars within its first ~6 weeks after launching July 29, 2026. |
| Pricing | Not yet announced | Free (Apache 2.0) |
WHAT PERPLEXITY DOES WELL
Credit where it’s due.
✓02
Broad harness coverage out of the box (Claude Code, Codex, Cursor, OpenClaw, OpenCode, Pi)
✓03
Forensic replay of past sessions, not just live streaming
✓04
Low-friction, single-binary install
WHERE SENTINEL DIFFERS
Why we’re building
this anyway.
→01
Dedicated pre-run skill and MCP scanning — checking what a skill says it will do before you pull it, not only logging what an agent did after the fact
→02
One product for both an individual developer and the IT team rolling agents out org-wide, instead of a self-hosted OSS tool you still have to operationalize
→03
A public roadmap toward ask-and-approve gating on destructive commands, not only opt-in blocking
THE HONEST VERDICT
Which one
should you use?
If you want a free, self-hosted activity monitor today and are comfortable running and maintaining it yourself, numbat is a strong choice — genuinely worth using. Sentinel is aimed at the layer above that: a product you don't have to operate yourself, with skill/MCP scanning built in and one place that works for both a solo developer and an IT team managing a fleet.
Join the Sentinel waitlist No account or payment required. See all comparisons → · Source: numbat