What is SubagentStop?

A cleanup hook that runs a PowerShell command when a subagent finishes. It stops listening processes using ports 8200 through 8299.

Cleaning up local development servers after subagents finish. It is intended for Windows environments with PowerShell.

It removes development servers left running after an agent task, which can occupy ports and interfere with later work.

SubagentStop — Hook by Caldis

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/caldis/react-zmage/subagent-stop

Clone the repo

git clone --depth 1 https://github.com/Caldis/react-zmage

Made for: Claude Code.

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 original No closer match found in the catalogue.

Security

Grade A, and why

SubagentStop 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 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.

.claude/settings.json · 15 lines

What it actually says

{
  "SubagentStop": [
    {
      "hooks": [
        {
          "type": "command",
          "shell": "powershell",
          "command": "Get-NetTCPConnection -LocalPort (8200..8299) -State Listen -ErrorAction SilentlyContinue | Select-Object -ExpandProperty OwningProcess -Unique | ForEach-Object { Stop-Process -Id $_ -Force -ErrorAction SilentlyContinue }",
          "timeout": 10,
          "statusMessage": "Cleaning up agent dev servers (8200-8299)"
        }
      ]
    }
  ]
}

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 First seen · 15 lines scan A cd74ec800847

Subscribe to this mod's changes

SubagentStop is a hook published in the GitHub repository Caldis/react-zmage (942 stars, last pushed 3mo 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 2026-08-30.

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SubagentStop

Getting it into your agent

Grade A, and why

Nothing flagged

What it actually says

What this file has done since we first saw it

Other hooks, from other repositories

SubagentStart

SubagentStop

SubagentStop

SubagentStop

Stop

SubagentStop