witness-pi

Persistent agent Analytics. Cost & usage tracking for your pi agent. Including models, provider, tokens, cost, skills, tools.

witness-pi is an extension that records the tokens and dollars spent in every pi session and keeps a running total for each repository. You can check your spend at any time, see which models, tools and skills use the most, and find the sessions that cost the most.

Why use it

• Cost overview. The running cost for the repo is always visible in pi's status bar.
• Totals per project. Spend is added up per repository, across every session and restart, so you can see what a project has cost so far.
• See where tokens go. Find the models, tools and skills that use the most tokens and cost the most.
• Nothing to set up. Install it once and keep working. The extension records usage on its own.

Features

Live cost in the status bar

💰 Witnessed: $1.23 · 45.6K TOK

Shows the total dollars and tokens for the current repository across all sessions. It updates after every agent turn.

Usage dashboard

Run this inside pi:

/witness-pi:show

This opens a local dashboard at http://localhost:4444. On macOS it opens in your browser automatically; on other systems pi shows the link. The dashboard shows:

• Totals: cost, tokens, and the number of distinct tools and skills used in this repo
• Model costs: dollars spent per model per day
• Tokens used: tokens per model per day
• Top models, tools and skills: how often each one was used
• Sessions table: every session with its time, model, turns, tools, skills, tokens and cost. You can sort by any column.

Detailed tracking

For every agent turn, witness-pi records:

• input, output, cache-read, cache-write and reasoning tokens
• cost in dollars
• each tool call, whether it failed, and the tokens and cost of the tool itself
• the model used (provider/model)
• skills used, whether run with /skill:<name> or loaded by the agent reading a SKILL.md

Install

pi install npm:witness-pi

To try it for one session without installing:

pi -e npm:witness-pi

Or install the same extension from source:

pi install git:github.com/HeapSoftGmbH/witness

[!IMPORTANT] Pi extensions run with your full user permissions. Review the source before installing anything from a third party.

Usage

1. Work in pi as usual. Usage is recorded automatically.
2. Check the status bar for the running total.
3. Run /witness-pi:show to open the dashboard.
4. Add /.witness to your .gitignore, unless you want to commit the usage log so your team can share it.