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/assistant-ui/tool-ui/session-startgit clone --depth 1 https://github.com/assistant-ui/tool-uiGrade 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.
What it actually says
{
"SessionStart": [
{
"hooks": [
{
"type": "command",
"command": "echo 'export NODE_ENV=development' >> $CLAUDE_ENV_FILE && echo '✓ Environment configured'"
},
{
"type": "command",
"command": "pnpm dev > /dev/null 2>&1 & echo '✓ Dev server starting on http://localhost:3000'"
}
]
}
]
}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 · 16 lines scan A d9a7750c175e
SessionStart is a hook published in the GitHub repository assistant-ui/tool-ui (773 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.
Other hooks, from other repositories
PreToolUse
Runs before the agent uses a tool for Edit, Write and Bash tool calls, executing pre-tool-use-edit-write.sh and pre-tool-use-bash.sh with --show-toplevel (2 commands). From NVIDIA/elements.
PermissionRequest
Runs when the agent asks permission for an action for Edit and Write tool calls, running an inline shell check. From NVIDIA/elements.
SessionStart
Runs when a session starts, executing welcome.sh via sh. From mahmoudilyan/marmoui.
Stop
Runs when the agent finishes a response, executing stop_gate.py via python3. From clownware/product-dev.
PostToolUse
Runs after a tool call finishes for Write and Edit tool calls, executing format_and_lint.sh. From supabase/supabase.
SessionStart
Runs when a session starts on startup, executing install_pkgs.sh. From supabase/supabase.