SessionStart

A session-start hook that runs a Python guard script when a new session begins. A hook is an automatic action attached to a particular event.

In plain words
What is it for?
Use it to trigger guard.py at session startup when the script exists in the project or one of its parent directories.
Why use it?
It lets the configured guard check the environment or apply its startup behavior without someone running it manually.

Hook for Claude Code

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/shafthq/shaft_engine/session-start
Clone the repo
git clone --depth 1 https://github.com/ShaftHQ/SHAFT_ENGINE

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 95% copy Near-identical to another mod 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.

Origin

This is a copy

95% identical to PreCompact — 2 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.

.claude/settings.json · 14 lines

What it actually says

{
  "SessionStart": [
    {
      "hooks": [
        {
          "command": "python3 -c \"import os,pathlib,runpy;os.environ['CHAOS_ENGINE_HOST']='claude';cands=('.chaos-engine/hooks/guard.py','plugins/chaos-engine/hooks/guard.py','chaos-engine/hooks/guard.py');p=next((root/rel for root in (pathlib.Path.cwd(),*pathlib.Path.cwd().parents) for rel in cands if (root/rel).is_file()),None);runpy.run_path(str(p),run_name='__main__') if p else print('{}')\"",
          "commandWindows": "py -3 -c \"import os,pathlib,runpy;os.environ['CHAOS_ENGINE_HOST']='claude';cands=('.chaos-engine/hooks/guard.py','plugins/chaos-engine/hooks/guard.py','chaos-engine/hooks/guard.py');p=next((root/rel for root in (pathlib.Path.cwd(),*pathlib.Path.cwd().parents) for rel in cands if (root/rel).is_file()),None);runpy.run_path(str(p),run_name='__main__') if p else print('{}')\"",
          "timeout": 30,
          "type": "command"
        }
      ]
    }
  ]
}
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.

  1. 2d ago First seen · 14 lines scan A be3c14e6a3fe

Subscribe to this mod's changes

SessionStart is a hook published in the GitHub repository ShaftHQ/SHAFT_ENGINE (407 stars, last pushed yesterday), 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 95% identical to PreCompact, differing in 2 lines, and is treated as a copy.