It can apply a predefined policy to each submitted request before the agent processes it, so the policy does not need to be added manually every time.

UserPromptSubmit — Hook for Claude Code by onehorizonai

UserPromptSubmit

UserPromptSubmit is a hook for Claude Code from onehorizonai/skills. Its token cost is not measured, scanned A, original, MIT.

A prompt-submission hook is an automated command that runs after you send a request but before the coding agent reads it. This one runs a Node.js script from the One Horizon skills package.

In plain words

What is it for?: It is for automatically checking or modifying submitted prompts according to the One Horizon policy script.
Why use it?: It can apply a predefined policy to each submitted request before the agent processes it, so the policy does not need to be added manually every time.

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the one-horizon plugin — 21 skills, 1 hook, 1 MCP server shipped together

Good fit It is for automatically checking or modifying submitted prompts according to the One Horizon policy script.

Compare 6 hooks from other repositories ↓

Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code

/plugin marketplace add onehorizonai/skills

Claude Code

/plugin install one-horizon

Made for: Claude Code.

Or install one-horizon, the plugin that ships this one along with the rest of its 21 skills, 1 hook, 1 MCP server.

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/hooks/onehorizonai/skills/user-prompt-submit.svg)](https://agentmods.dev/hooks/onehorizonai/skills/user-prompt-submit)

Your own site

<a href="https://agentmods.dev/hooks/onehorizonai/skills/user-prompt-submit"><img src="https://agentmods.dev/badge/hooks/onehorizonai/skills/user-prompt-submit.svg" alt="Measured on agentmods" height="20"></a>

Per session not measured What this adds to a session before it is invoked.

When invoked not measured Not applicable: nothing here is loaded into a session.

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

Origin original No closer match found in the catalogue.

Security

Grade A, and why

UserPromptSubmit 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 7d ago.

A static scan of the commands this hook runs, not an audit. A hook is shell that executes on your machine at the event it names, which is why every command in it is printed with what was found.

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.

hooks/hooks.json · 13 lines

What it actually says

{
  "UserPromptSubmit": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "node ${CLAUDE_PLUGIN_ROOT}/hooks/scripts/inject_one_horizon_policy.mjs",
          "timeout": 15
        }
      ]
    }
  ]
}

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.

7d ago First seen · 13 lines scan A c3ca0c8aeb59

Subscribe to this mod's changes

UserPromptSubmit is a hook published in the GitHub repository onehorizonai/skills (2 stars, last pushed 1mo ago), licensed MIT. Its token cost is not measured: a hook is shell that never enters the context. 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 2026-08-31.

UserPromptSubmit

Getting it into your agent

Wrote this? Show the measurements

Grade A, and why

Nothing flagged

What it actually says

What this file has done since we first saw it

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