Arcjet
Arcjet is a security SDK and platform that runs inside your code to stop bots, abuse and prompt injection and to enforce policy on AI agents' tool calls. Its new custom-trained models include Himalia 1 for prompt injection and Thebe 1 for coding agents.
About Arcjet
What Arcjet is
Arcjet is a developer-first security platform that runs inside your code. It provides SDK building blocks such as bot protection, rate limiting, a WAF and email validation, and now positions itself as an AI agent runtime security platform that observes, enforces policy on and audits agent prompts, actions and tool calls.
The launch: custom AI security models
- Himalia 1: prompt injection classifier, live for all SDK prompt-injection checks; a fine-tune of Qwen3-0.6B with a benign/injection head. Arcjet reports F1 0.964 and 0.971 on two public datasets.
- Thebe 1: trained on coding-agent data for reviewing what coding agents do (early access).
- Carme 1: for autonomous security agents (early access).
- A ShieldGemma-based content moderation model is coming soon.
For coding agents
Works with Claude Code, Codex, Copilot and Cursor through their hooks, with skills, a Claude Code/Cursor plugin, a hosted MCP server, a CLI and Rego policies over shell, web, MCP and file-write actions.
For apps
- Shield WAF, bot protection, rate limiting, signup protection, email validation
- PII detection, prompt injection, content moderation, budget control, data loss prevention
- guard() for tool calls and workflow steps; dry-run and live modes
- SDKs for JS/TS, Python and Go; many web and agent frameworks
Pricing
Individual $25/month, Startup $299/month, Enterprise custom, plus $5 per 1M web requests and $50 per 1M agent requests. 15-day free trial.
Value & Audience
Value Proposition
Security rules that live in the codebase, are versioned and tested like code, and run in-process with low latency for both web apps and AI agents, now backed by Arcjet's own small, purpose-trained security models.
Problem Solved
Web apps and AI agents face bots, abuse, prompt injection and unsafe tool calls, and traditional edge firewalls lack the application context to judge them; Arcjet makes these decisions inside the app or agent with full context.
Tech Stack
Social & Links
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Feedback & Roadmap
Arcjet FAQ
Common questions about Arcjet's features, pricing, and use cases
Is Arcjet free to use?
No. Arcjet is a paid product, starting at Individual - $25/mo + usage - 1 team member, 1 hour log retention, email support; usage $5 per 1M web requests, $50 per 1M agent requests. Plans listed: Individual - $25/mo + usage - 1 team member, 1 hour log retention, email support; usage $5 per 1M web requests, $50 per 1M agent requests; Startup - $299/mo + usage - 2 team members, 24 hour log retention, email and Slack support; Enterprise - Custom - unlimited team members, SIEM export, priority support, committed-usage discounts.
What are some alternatives to Arcjet?
Popular Security & Privacy alternatives to Arcjet include SAM - Chrome Web Store, RoomGrade and Presend.
Arcjet appears in
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