What is SessionStart?

A session-start hook that runs a shell check when a coding-agent session begins. It checks whether the ArbiterX command is installed and reports the result.

Use it to check for ArbiterX at the start of each session and display an installation hint when it is not found.

It provides an early indication of whether ArbiterX is available in the environment. Without it, you may not know until later that the command is missing.

SessionStart — Hook by NeelPrime

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/neelprime/arbiterx/session-start

Clone the repo

git clone --depth 1 https://github.com/NeelPrime/arbiterx

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

SessionStart 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 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

{
  "SessionStart": [
    {
      "matcher": "*",
      "hooks": [
        {
          "type": "command",
          "command": "command -v arbiterx >/dev/null 2>&1 && echo 'ArbiterX engineering mode active.' || echo 'ArbiterX not installed. Run: pip install arbiterx-gate'"
        }
      ]
    }
  ]
}

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 First seen · 13 lines scan A 41ed9a34581e

Subscribe to this mod's changes

SessionStart is a hook published in the GitHub repository NeelPrime/arbiterx (2 stars, last pushed 1mo ago), licensed Apache-2.0. 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.

Code review ai ai-code-quality ai-coding-assistant ai-middleware claude-code code-quality

SessionStart

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

UserPromptSubmit

PostToolUse

PostToolUse

Stop

TaskCompleted

SessionStart