What is SessionStart?

A startup hook that runs shell commands when an agent session starts, resumes, or is compacted. It installs project tools, builds the project, and runs a session handoff script.

It helps prepare a project environment and restore session context during agent sessions.

It repeats setup and handoff tasks automatically instead of relying on someone to remember them.

SessionStart — Hook by zernie

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/zernie/vigiles/session-start

Clone the repo

git clone --depth 1 https://github.com/zernie/vigiles

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

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 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 · 22 lines

What it actually says

{
  "SessionStart": [
    {
      "matcher": "startup|compact",
      "hooks": [
        {
          "type": "command",
          "command": "npm install && npm run build && pip install ruff pylint && gem install rubocop 2>/dev/null; true"
        }
      ]
    },
    {
      "matcher": "startup|resume|compact",
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PROJECT_DIR:-.}/.claude/hooks/session-handoff.sh\""
        }
      ]
    }
  ]
}

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 · 22 lines scan A 58e82e5f4d5c

Subscribe to this mod's changes

SessionStart is a hook published in the GitHub repository zernie/vigiles (15 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. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

agentic-coding ai-agents anthropic claude claude-code cli

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

Setup

PreToolUse

PreToolUse

SessionStart

Stop

PostToolUse