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SessionStart

SessionStart is a hook for Claude Code from Gfriend997/gemini-companion. Its token cost is not measured, scanned A, original, MIT.

A session-start hook that runs a Node.js script when a coding session begins.

In plain words
What is it for?
Running startup checks or displaying session-specific routing instructions.
Why use it?
It automatically applies the script's routing-policy output at the start of each session.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the gemini-companion plugin — 3 skills, 10 commands, 1 agent, 2 hooks shipped together

One of 2 entries in hooks.json — they are configured in one file and arrive together.

not rated 5repo 23d ago A scan tokens not measured original MIT

Good fit Running startup checks or displaying session-specific routing instructions.

Compare 6 hooks from other repositories ↓
View source ↗ Gfriend997/gemini-companion garywong.ai
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add Gfriend997/gemini-companion
Claude Code
/plugin install gemini-companion

Made for: Claude Code.

Or install gemini-companion, the plugin that ships this one along with the rest of its 3 skills, 10 commands, 1 agent, 2 hooks.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for SessionStart

README.md
[![agentmods](https://agentmods.dev/badge/hooks/gfriend997/gemini-companion/session-start.svg)](https://agentmods.dev/hooks/gfriend997/gemini-companion/session-start)
Your own site
<a href="https://agentmods.dev/hooks/gfriend997/gemini-companion/session-start"><img src="https://agentmods.dev/badge/hooks/gfriend997/gemini-companion/session-start.svg" alt="Measured on agentmods" height="20"></a>
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. A grade says what 26 rules found in the file — not that it is safe.
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 6d 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": [
    {
      "hooks": [
        {
          "type": "command",
          "command": "node \"${CLAUDE_PLUGIN_ROOT}/scripts/print-routing-policy.mjs\"",
          "timeout": 10
        }
      ]
    }
  ]
}
Same file

What else hooks.json configures

This page is one entry in a file that holds 2. Installing the file brings all of them; each is measured and scanned on its own page.

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. 6d ago First seen · 13 lines scan A be4274272aa8

Subscribe to this mod's changes

SessionStart is a hook published in the GitHub repository Gfriend997/gemini-companion (5 stars, last pushed 23d 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 2026-08-31.

Related

Other hooks, from other repositories

SessionStart

Runs when a session starts, executing on-start.js via node. From google-gemini/gemini-cli.

google-gemini/gemini-cli · not measured

PreToolUse

Runs before the agent uses a tool for Bash tool calls, running an inline shell check. From apache/superset.

apache/superset · not measured

PreToolUse

Runs before the agent uses a tool, executing pre-write.sh and pre-bash.sh (2 commands). From anthropics/claude-cookbooks.

anthropics/claude-cookbooks · not measured

PreCompact

Runs before the context is compacted for manual and auto tool calls, executing hook-handler.cjs via node (4 commands). From ruvnet/RuView.

ruvnet/RuView · not measured

SessionStart

Runs when a session starts on startup, clear and compact, executing run-hook.cmd. From obra/superpowers.

obra/superpowers · not measured

SessionStart

Runs when a session starts, executing hook-handler.cjs and auto-memory-hook.mjs via node (2 commands). From ruvnet/RuView.

ruvnet/RuView · not measured