What is integrate-arcjet-guard-langchain?

A security integration for LangChain's JavaScript createAgent function. LangChain is a framework for building applications that use language models and tools; the integration checks authored and runtime-discovered tools with Arcjet.

Use it to guard LangChain tools, MCP tools, and other tools discovered while an agent runs, while preserving tool-call responses and correlation.

It helps prevent unapproved tools from running, including tools supplied through MCP, a standard way to connect applications to external tools and data. It also links decisions to the caller's thread or session.

integrate-arcjet-guard-langchain — Skill for Claude Code and Codex by

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-langchain

Clone the repo

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

Made for: Claude Code, Codex.

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-langchain/github.svg)](https://agentmods.dev/skills/arcjet/arcjet-js/integrate-arcjet-guard-langchain)

Your own site

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

Per session 101 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 3,516 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	$0.00101	$0.03516
Opus 5	$0.00051	$0.01758
Sonnet 5	$0.00020	$0.00703
Haiku 4.5	$0.00010	$0.00352

Measured 2d ago against content hash 4fa381500218, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

integrate-arcjet-guard-langchain 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 2d ago.

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-langchain/SKILL.md · 319 lines

How it starts

The opening of the file, as written. The whole thing — 319 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Integrate Arcjet Guard into a LangChain JS createAgent

@arcjet/guard's LangChain v1 namespace wraps the agent's existing Arcjet client. It never talks to the Arcjet API itself. Three surfaces, one decision rule:

An authored tool (tool() / StructuredTool) → guardTool(). DENY returns a plain ArcjetDenialResult. Do not throw. Do not fabricate a ToolMessage. createAgent's baseHandler wraps a non-ToolMessage in a success ToolMessage.
MCP / unwrapped / runtime-discovered tools → guardMiddleware(). A createAgent({ middleware }) middleware whose wrapToolCall is the invoke()-wide gate. It denies by returning a real ToolMessage (content = JSON of the payload, tool_call_id = request.toolCall.id, name = request.toolCall.name) without calling handler. Already-branded tools are skipped when request.tool can be looked up. Do not set status: "error". Do not throw (throws bubble and drop arcjetDenied).
Correlation → langchainContext() reads configurable.thread_id (what wrapToolCall sees on runtime.configurable as of langchain 1.2.34), then caller-owned sessionId / conversationId. It never mints a new id. It never reads traceId. A run that pauses on interrupt() resumes through the same config, so it keeps its thread_id and its later decisions stay on the Sequence that started it — the interrupt and its resume value are simply not correlation sources of their own.

This namespace is LangChain JS createAgent + wrapToolCall. Not LangGraph Graph API (StateGraph + ToolNode) — that is @arcjet/guard/langgraph/v1. Not vercel-ai/v7. Server-side provider tools and headless .implement() tools are out of scope. Do not also wrap the same tool with @arcjet/guard/langgraph/v1 or @arcjet/guard/vercel-ai/v7.

Docs live at docs.arcjet.com/guards/langchain-js/. Do not use /guards/langchain/ — that is the live Python page.

Read the full file on GitHub · 319 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.

2d ago Changed · +5 lines 4fa381500218
7d ago Changed · +7 lines 34caeb1a9640
12d ago First seen · 307 lines · 101 tokens per session scan A ac817744169c

Subscribe to this mod's changes

integrate-arcjet-guard-langchain is a skill published in the GitHub repository arcjet/arcjet-js (682 stars, last pushed yesterday), licensed Apache-2.0. It adds 101 tokens to every session and 3,516 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 2026-08-30.

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

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