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.
npx agentmods add hooks/msshives-gif/claude-plugins/session-startgit clone --depth 1 https://github.com/msshives-gif/claude-pluginsGrade 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.
This is a copy
70% identical to PreToolUse — 36 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.
What it actually says
{
"SessionStart": [
{
"matcher": "compact",
"hooks": [
{
"type": "command",
"command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || python \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || true",
"timeout": 5
}
]
},
{
"matcher": "startup",
"hooks": [
{
"type": "command",
"command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || python \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || true",
"timeout": 5
}
]
},
{
"matcher": "resume",
"hooks": [
{
"type": "command",
"command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || python \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || true",
"timeout": 5
}
]
},
{
"matcher": "clear",
"hooks": [
{
"type": "command",
"command": "python3 \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || python \"${CLAUDE_PLUGIN_ROOT}/hooks/session_start.py\" || true",
"timeout": 5
}
]
}
]
}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 · 44 lines scan A f61c2abf57cf
SessionStart is a hook published in the GitHub repository msshives-gif/claude-plugins (2 stars, last pushed 5d 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 70% identical to PreToolUse, differing in 36 lines, and is treated as a copy.
Other hooks, from other repositories
PreToolUse
Runs before the agent uses a tool for Edit, Write, MultiEdit, Bash and Skill tool calls, running sh (8 commands). From CATWILLgh/MAINFRAME.
Stop
Runs when the agent finishes a response, running sh (5 commands). From CATWILLgh/MAINFRAME.
SubagentStop
Runs when a subagent finishes, running sh (4 commands). From CATWILLgh/MAINFRAME.
SessionStart
Runs when a session starts on startup, resume, clear, compact and fork, running sh (3 commands). From CATWILLgh/MAINFRAME.
UserPromptExpansion
Runs to expand your prompt before the agent sees it for ^mainframe:.*$ and mainframe:init tool calls, running sh (2 commands). From CATWILLgh/MAINFRAME.
UserPromptSubmit
Runs when you submit a prompt, before the agent sees it, running sh (2 commands). From CATWILLgh/MAINFRAME.