Hooks

Where it lives

• hooks/session-start.shRunsGitHub ↗
  Read the script

  #!/usr/bin/env bash
  # Portions of this file are adapted from the n8n-io/skills plugin
  # (https://github.com/n8n-io/skills), licensed under Apache License 2.0.
  # Adapted for the community n8n-mcp MCP server. See /NOTICES.
  #
  # SessionStart hook for n8n-mcp-skills.
  # Loads the meta-skill (using-n8n-mcp-skills) into every session via additionalContext.
  # Re-fires on resume/clear/compact so the protocol survives compaction.
  #
  # On `clear` and `compact`, also wipes the PreToolUse hook markers for this
  # session so the per-node-type warnings can fire again. The agent's memory
  # of those warnings is gone after a clear/compact, so the markers shouldn't
  # keep them silent.
  #
  # Fails silently and never blocks session startup.
  
  set -uo pipefail
  
  PLUGIN_ROOT="${CLAUDE_PLUGIN_ROOT:-$(cd "$(dirname "$0")/.." && pwd)}"
  META_SKILL="${PLUGIN_ROOT}/skills/using-n8n-mcp-skills/SKILL.md"
  CACHE_DIR="${HOME}/.cache/n8n-mcp-skills"
  mkdir -p "${CACHE_DIR}" 2>/dev/null || true
  
  INPUT="$(cat)"
  
  # --- Reset PreToolUse markers on clear/compact -------------------------------
  #
  # After /clear or /compact, the agent has lost the additionalContext that the
  # PreToolUse hooks injected earlier in the session. Without wiping markers,
  # the per-node warnings stay silent for the rest of the session even though
  # the agent no longer remembers them.
  
  if command -v jq >/dev/null 2>&1; then
    SOURCE="$(echo "${INPUT}" | jq -r '.source // empty' 2>/dev/null)"
    SESSION_ID="$(echo "${INPUT}" | jq -r '.session_id // empty' 2>/dev/null)"
  
    if [[ "${SOURCE}" == "clear" || "${SOURCE}" == "compact" ]] && [[ -n "${SESSION_ID}" ]]; then
      STATE_DIR="${TMPDIR:-/tmp}/n8n-mcp-skills-state"
      rm -f "${STATE_DIR}/${SESSION_ID}-"*.loaded 2>/dev/null || true
    fi
  fi
  
  # --- Build additionalContext --------------------------------------------------
  
  if [[ ! -r "${META_SKILL}" ]]; then
    # Skill missing or unreadable. Fail open with no context, don't break session.
    exit 0
  fi
  
  SKILL_BODY="$(cat "${META_SKILL}")"
  
  ADDITIONAL_CONTEXT="${SKILL_BODY}"
  
  # --- Emit hook output ---------------------------------------------------------
  
  # jq is the safe way to escape arbitrary text into JSON. Fall back to python3
  # if jq isn't installed (rare on macOS, possible on minimal Linux).
  if command -v jq >/dev/null 2>&1; then
    jq -n --arg ctx "${ADDITIONAL_CONTEXT}" '{
      hookSpecificOutput: {
        hookEventName: "SessionStart",
        additionalContext: $ctx
      }
    }'
  elif command -v python3 >/dev/null 2>&1; then
    python3 -c '
  import json, sys
  ctx = sys.stdin.read()
  print(json.dumps({
    "hookSpecificOutput": {
      "hookEventName": "SessionStart",
      "additionalContext": ctx
    }
  }))
  ' <<< "${ADDITIONAL_CONTEXT}"
  else
    # No JSON encoder available, skip injection rather than emit malformed JSON.
    exit 0
  fi
  

Read the script before you install anything that runs on your machine. This is the one part of a plugin that acts without being asked.