HEAD TO HEAD
Onyx Security matched with Prompt Security (SentinelOne): agentic endpoint security compared
SHORT ANSWER
On our published weights Onyx Security scores higher overall, 6.85 to 5.45 out of 10. Onyx scores higher on stop before it runs, verdict range, capability rules, actor trail and cloud and workspace reach; Prompt Security scores higher on named agent coverage and public proof; they tie on rollout path. Which fits depends on which of those criteria matters most to you.
By The Agent Desk · Agentic Endpoint Compare · Published 2026-10-11
Desk research from public vendor pages, press releases and standards pages read on 27 September and 11 October 2026. Editorial assessment; we did not run the products.
How do they compare at a glance?
Onyx Security
Inline control with the widest set of verdicts
Rank 2 of 8 among broader AI security platforms
Prompt Security (SentinelOne)
SentinelOne (deal announced 5 August 2025; completion reported in September 2025)
SentinelOne Singularity estates
Rank 8 of 8 among broader AI security platforms
Which scores higher on each criterion?
| Criterion | Weight | Onyx Security | Prompt Security (SentinelOne) | Higher |
|---|---|---|---|---|
| Stop before it runs | 25% | 8 / 10 Inspects every prompt, tool call and model response inline before acting on it. Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 6 / 10 Governs what agents and MCP servers can do; per-tool-call enforcement is not detailed. Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 | Onyx |
| Verdict range | 15% | 7 / 10 Documents 4 of six verdict types: Block or deny, Ask a person, Alert or warn and Mask or modify. "Five actions: alert, block, mask, steer, or ask." Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 3 / 10 Documents 2 of six verdict types: Block or deny and Mask or modify. "Prevents prompt injection and data leakage; its browser extension inspects and redacts prompts." Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 Source: Prompt Security blog: browser and endpoint sensors (updated 16 August 2026) · Read 11 Oct 2026 | Onyx |
| Capability rules | 15% | 6 / 10 Agent posture covers misconfigurations, excessive permissions and credential handling; rules by capability type (shell, packages, cloud CLIs) are not itemized. Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 5 / 10 Maps agents and MCP servers and finds shadow MCP servers; capability rules are not itemized. Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 | Onyx |
| Actor trail | 10% | 7 / 10 Agent identity and access governance is a named solution; per-action attribution detail is lighter than the leader. Source: Onyx Security homepage · Read 27 Sep 2026 | 5 / 10 Agent versus person attribution is not described on the pages we read. Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 | Onyx |
| Rollout path | 10% | 6 / 10 Endpoint agents, browser extensions, APIs and gateways; the device component is resident software. Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 6 / 10 Two resident sensors, a browser extension and a dedicated AI endpoint agent, inside the SentinelOne Singularity Platform. Source: Prompt Security blog: browser and endpoint sensors (updated 16 August 2026) · Read 11 Oct 2026 | Tie |
| Cloud and workspace reach | 10% | 9 / 10 Covers cloud workloads alongside browser AI, coding assistants, desktop agents and MCP servers, across SaaS, cloud, endpoint and code. Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 6 / 10 Covers homegrown AI apps from testing to runtime as well as employee and developer AI use. Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 | Onyx |
| Named agent coverage | 5% | 0 / 10 Names 0 of the six agents we track: none. Source: Onyx Security: AI security platform · Read 27 Sep 2026 | 5 / 10 Names 3 of the six agents we track: Claude Code, Cursor and GitHub Copilot. Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026 | Prompt Security |
| Public proof | 10% | 7 / 10 Series B of $113M announced 29 July 2026; SOC 2 Type II and ISO 27001 listed; pricing not published. Source: Onyx Security blog: $113M Series B (29 July 2026) · Read 27 Sep 2026 | 8 / 10 Backed by SentinelOne, which announced the acquisition on 5 August 2025; pricing not published. Source: SentinelOne press release: agreement to acquire Prompt Security (5 August 2025) · Read 27 Sep 2026 | Prompt Security |
Which verdicts does each document?
| Verdict type | Onyx Security | Prompt Security (SentinelOne) |
|---|---|---|
| Block or deny | Documented | Documented |
| Ask a person | Documented | Not described |
| Alert or warn | Documented | Not described |
| Mask or modify | Documented | Documented |
| Simulate first | Not described | Not described |
| Remove or scale back | Not described | Not described |
- Onyx Security: "Five actions: alert, block, mask, steer, or ask."
Source: Onyx Security: AI security platform · Read 27 Sep 2026
- Prompt Security (SentinelOne): "Prevents prompt injection and data leakage; its browser extension inspects and redacts prompts."
Source: SentinelOne: Prompt Security, securing AI · Read 27 Sep 2026
Source: Prompt Security blog: browser and endpoint sensors (updated 16 August 2026) · Read 11 Oct 2026
How does each reach devices?
Onyx Security
Endpoint agents, browser extensions, APIs and gateways; Onyx says no SDK changes are needed.
Source: Onyx Security: AI security platform · Read 27 Sep 2026
Prompt Security (SentinelOne)
Two local sensors, a browser extension and a dedicated AI endpoint agent, built into the SentinelOne Singularity Platform.
Source: Prompt Security blog: browser and endpoint sensors (updated 16 August 2026) · Read 11 Oct 2026
Which agents does each name?
| Agent | Onyx Security | Prompt Security (SentinelOne) |
|---|---|---|
| Claude Code | Not named | Named |
| Cursor | Not named | Named |
| GitHub Copilot | Not named | Named |
| OpenAI Codex | Not named | Not named |
| Windsurf | Not named | Not named |
| Claude Desktop | Not named | Not named |
| Named | 0 of 6 | 3 of 6 |
Which should you choose?
Choose Onyx Security if you need cloud and workspace reach and stop before it runs. Onyx Security is best for: Inline control with the widest set of verdicts.
Choose Prompt Security (SentinelOne) if you need public proof and stop before it runs. Prompt Security (SentinelOne) is best for: SentinelOne Singularity estates.
Frequently asked questions
Which is better for agentic endpoint security, Onyx Security or Prompt Security (SentinelOne)?
On our published weights Onyx Security scores higher overall, 6.85 to 5.45 out of 10. See the criterion table above for where each scores higher.
Which stops an agent action before it runs more fully, Onyx Security or Prompt Security (SentinelOne)?
Onyx Security scores higher on stopping an action before it runs (8 to 6). Onyx Security: Inspects every prompt, tool call and model response inline before acting on it. Prompt Security (SentinelOne): Governs what agents and MCP servers can do; per-tool-call enforcement is not detailed.
Do Onyx Security and Prompt Security (SentinelOne) publish prices?
Onyx Security: not published. Onyx Security publishes no pricing. Prompt Security (SentinelOne): not published. SentinelOne publishes no pricing for Prompt Security.