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instar: Hook for Claude Code

.claude/settings.json

SessionStart is a hook for Claude Code from JKHeadley/instar. Its token cost is not measured, scanned A, original, MIT.

A startup hook configuration that runs a shell script when a session starts, resumes, or is compacted. A hook is an automatic action triggered by one of these session events.

In plain words
What is it for?
Use it to run .instar/hooks/instar/session-start.sh during startup, resume, and context compaction.
Why use it?
It ensures the same session-start script runs at each listed lifecycle point.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PROJECT_DIR} variable.

This is JKHeadley/instar's own configuration. It tells Claude Code how to work on instar itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything instar configures →

One of 14 entries in settings.json upstream. Installing this one merges just its entry into your config; the other 13 are separate, each on its own page.

not rated 84repo changed 28d ago A scan tokens not measured original MIT
View source ↗ JKHeadley/instar instar.sh
Reuse

Borrowing it

Nothing to install: this file belongs to JKHeadley/instar. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/JKHeadley/instar/main/.claude/settings.json
Clone the repo
git clone --depth 1 https://github.com/JKHeadley/instar

Made for: Claude Code.

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/jkheadley/instar/session-start/github.svg)](https://agentmods.dev/hooks/jkheadley/instar/session-start)
Your own site
<a href="https://agentmods.dev/hooks/jkheadley/instar/session-start"><img src="https://agentmods.dev/badge/hooks/jkheadley/instar/session-start/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for SessionStart

Your own site · 80×15
<a href="https://agentmods.dev/hooks/jkheadley/instar/session-start"><img src="https://agentmods.dev/badge/hooks/jkheadley/instar/session-start.svg" alt="Reviewed on agentmods" width="80" 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 28d 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.

.claude/settings.json · 34 lines

What it actually says

{
  "SessionStart": [
    {
      "matcher": "startup",
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PROJECT_DIR}/.instar/hooks/instar/session-start.sh\"",
          "timeout": 5
        }
      ]
    },
    {
      "matcher": "resume",
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PROJECT_DIR}/.instar/hooks/instar/session-start.sh\"",
          "timeout": 5
        }
      ]
    },
    {
      "matcher": "compact",
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PROJECT_DIR}/.instar/hooks/instar/session-start.sh\"",
          "timeout": 5
        }
      ]
    }
  ]
}
Same file

What else settings.json configures

This page is one entry in a file that holds 14. 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. 28d ago Changed 56458cc638a0
  2. 1mo ago First seen · 34 lines scan A ec633e3b2eb1

Subscribe to this mod's changes

SessionStart is a hook published in the GitHub repository JKHeadley/instar (84 stars, last pushed today), 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.

Autonomous AgentsClaude CodeTypeScriptagent-infrastructureagent-skillsai-agents
Related

Other hooks, from other repositories

SessionStart

Runs when a session starts, running an inline shell check. From open-covenant/covenant.

open-covenant/covenant · not measured

SessionStart

Runs when a session starts on startup, executing install_pkgs.sh. From supabase/supabase.

supabase/supabase · not measured

PostToolUse

Runs after a tool call finishes for Write and Edit tool calls, executing format_and_lint.sh. From supabase/supabase.

supabase/supabase · not measured

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