What is integrate-arcjet-guard-claude-managed-agents?

A security integration for Claude Managed Agents, Anthropic’s hosted service for running agents through a web API. It checks incoming user messages and custom tool calls with Arcjet before they are handled.

Use it when adding Arcjet checks to Claude Managed Agents, rate-limiting custom tools, or returning an error when a tool call is denied.

It prevents denied messages from starting sessions and denied custom tools from running. It also clarifies which hosted actions cannot be checked by this integration.

integrate-arcjet-guard-claude-managed-agents

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add arcjet/arcjet-js --skill integrate-arcjet-guard-claude-managed-agents

Clone the repo

git clone --depth 1 https://github.com/arcjet/arcjet-js

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents/github.svg)](https://agentmods.dev/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents)

Your own site

<a href="https://agentmods.dev/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents"><img src="https://agentmods.dev/badge/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents"><img src="https://agentmods.dev/badge/skills/arcjet/arcjet-js/integrate-arcjet-guard-claude-managed-agents.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 102 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,240 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

NVIDIA SkillSpector pass 7 Sept 2026

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00102	$0.02240
Opus 5	$0.00051	$0.01120
Sonnet 5	$0.00020	$0.00448
Haiku 4.5	$0.00010	$0.00224

Measured yesterday against content hash b62dfc106909, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

integrate-arcjet-guard-claude-managed-agents scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

arcjet-guard/skills/integrate-arcjet-guard-claude-managed-agents/SKILL.md · 223 lines

How it starts

The opening of the file, as written. The whole thing — 223 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Integrate Arcjet Guard into Claude Managed Agents

@arcjet/guard's Claude Managed Agents v0 namespace wraps the agent's existing Arcjet client. It never talks to the Arcjet API itself. Anthropic runs the hosted tool loop. There is no PreToolUse.

This is not @arcjet/guard/claude-agent-sdk/v0. Do not reuse that adapter, its hooks, or guardTool.

Inbound text (user.message / initial_events) → guardEvents() before sessions.events.send. DENY does not send. There is no guardInbound.
A custom tool you execute (agent.custom_tool_use) → guardCustomTool(). DENY does not run the tool; send user.custom_tool_result with is_error: true and error text (that field exists on the real events API). Self-hosted EnvironmentWorker / betaTool({ run }) uses the same gate. The CLI worker cannot register custom tools.
Correlation → claudeManagedAgentsContext() is caller-owned only. It never mints. It never treats Anthropic session/event ids as if we created them. Never traceId.

What cannot be gated

Default permission_policy: always_allow cannot be gated. Anthropic executes bash/read/write in the cloud sandbox before your process sees an event. web_search / web_fetch always run on Anthropic. MCP: Anthropic is the client; customer-side Guard is on custom tools and MCP servers you host. user.tool_confirmation is HITL (always_ask), not a policy gate — do not add a confirmation helper as the happy path.

protect() stays fail-open. These helpers are fail-closed.

Docs: https://docs.arcjet.com/guards/claude-managed-agents/ (shared JS+Python page). Do not edit /guards/claude-agent-sdk/ or /guards/claude-agent-sdk-py/.

Questions to ask the human first

Ask only what you cannot infer from the code; suggest defaults.

Which custom tools does the app execute on agent.custom_tool_use? Those get guardCustomTool. Built-ins under always_allow cannot.
What limits? (e.g. "10 lookups/min per order" → tokenBucket.)
Who is the user for metadata — an opaque user/tenant ID (never PII)? Default: none. Session/event ids from Anthropic are not the correlation id.
Is an Arcjet outage unacceptable? Every helper defaults to onGuardError: "deny". Ask explicitly about inbound guardEvents: failing closed there means the turn is not sent.

Read the full file on GitHub · 223 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

yesterday Changed · +6 lines b62dfc106909
6d ago First seen · 217 lines · 102 tokens per session scan A c7301c097f38

Subscribe to this mod's changes

integrate-arcjet-guard-claude-managed-agents is a skill published in the GitHub repository arcjet/arcjet-js (682 stars, last pushed yesterday), licensed Apache-2.0. It adds 102 tokens to every session and 2,240 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.

Security agent-security ai-agents ai-security application-security bot-detection llm-security

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