What is UserPromptSubmit?

A Claude Code prompt hook that runs a shell script whenever a user submits a prompt, before the agent sees it.

It runs on-prompt-submit.sh for prompt-submission events, with a five-second time limit.

It lets OpenCoven Cast react at the start of each prompt without requiring a separate manual command.

UserPromptSubmit — Hook by OpenCoven

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.

agentmods

npx agentmods add hooks/opencoven/claude-code-cast/user-prompt-submit

Clone the repo

git clone --depth 1 https://github.com/OpenCoven/claude-code-cast

Or install cast, the plugin that ships this one along with the rest of its 6 hooks.

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. Scan, not verified.

Origin 59% copy Near-identical to another mod 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 3d 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.

Origin

This is a copy

59% identical to SessionStart — 8 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/cast/hooks/hooks.json · 13 lines

What it actually says

{
  "UserPromptSubmit": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "\"${CLAUDE_PLUGIN_ROOT}/scripts/on-prompt-submit.sh\"",
          "timeout": 5
        }
      ]
    }
  ]
}

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.

3d ago First seen · 13 lines scan A 86fbf025e707

Subscribe to this mod's changes

UserPromptSubmit is a hook published in the GitHub repository OpenCoven/claude-code-cast (5 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. It is 59% identical to SessionStart, differing in 8 lines, and is treated as a copy.

claude-code coding-agent integration local-first opencoven shell

SubagentStop

Runs when a subagent finishes, running observer hook claude-code subagent-stop. From superbasedapp/observer.

superbasedapp/observer · not measured