Hermes Agent Turn Completion Hook

Hermes Agent Turn Completion Hook | Generated by AI

Home 2026.05

This is a post_llm_call shell hook for Hermes Agent — it fires a macOS notification every time the agent finishes a turn (i.e., after the tool-calling loop completes and the final response is ready).

Let me break it down piece by piece:

Shebang & metadata

#!/usr/bin/env bash
# ~/.hermes/agent-hooks/on-agent-done.sh

Saved to ~/.hermes/agent-hooks/ — that’s the directory Hermes watches for lifecycle hooks. This one runs automatically after each LLM call completes.

Payload reading

payload="$(cat -)"

The hook system pipes a JSON payload to the script via stdin. The payload contains the current context: cwd, extra.user_message, extra.conversation_history, etc.

Data extraction via embedded Python

extracted=$(echo "$payload" | python3 -c "...")

A quick inline Python script parses the JSON and extracts 3 things:

Directory name — takes the basename of cwd (e.g., hermes-agent from /Users/lzwjava/projects/hermes-agent)
First 10 chars of the user’s message — so you can see what the last prompt was about
Conversation history count — how many turns deep you are

These are packed into a pipe-delimited string like hermes-agent|what's the|3.

Notification construction

subtitle="msg: ${user_preview}  |  turns: ${hist_count}"

Builds a subtitle showing the message preview and conversation depth.

macOS notification

terminal-notifier \
  -title "Hermes Agent — ${dirname}" \
  -subtitle "${subtitle}" \
  -message "Hermes has completed one turn." \
  -sound Glass \
  -activate com.mitchellh.ghostty \
  -group com.hermes.notification \
  2>/dev/null || true

Uses terminal-notifier (a macOS notification CLI tool — installable via brew install terminal-notifier) to:

Show a notification like:
Hermes Agent — hermes-agent
msg: what’s the | turns: 3
Hermes has completed one turn.
Plays the Glass system sound
-activate com.mitchellh.ghostty makes clicking the notification bring Ghostty (your terminal emulator) to front instead of just opening Notification Center
-group com.hermes.notification groups all Hermes notifications together (so macOS replaces old ones rather than stacking them)

Hook system requirement

printf '{}\n'

The hook system expects a JSON object on stdout (even if empty) as an acknowledgment. {} means “all good, proceed.” Without this, Hermes might log a warning.

Why you’d want this: if you run long tasks in the background or step away while Hermes works, this ping lets you know the agent is done and ready for your next input — without having to keep checking the terminal.

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