pi-meter

Know what your coding agents cost — and stay on budget.

pi-meter tracks every LLM call your AI coding agent makes, aggregates spend across sessions, days, and models, and keeps you on budget with three escalating responses: it warns as you approach a limit, auto-downshifts to a cheaper model when you go over, and can hard cut off — refusing prompts and blocking tools — when you blow a hard cap.

One core engine, four ways to run it: a CLI, an MCP server, a Claude/Cursor skill, and a pi extension.

Why

LLM coding agents burn money quietly — a long session on a frontier model can run into real dollars before you notice. pi-meter gives you:

• a portable ledger of every call (model, tokens, cost) you can grep,
• budgets with three responses — warn → downshift → cut off,
• and zero lock-in: plain JSONL + a JSON config file. No account, no daemon, no telemetry.

Features

• Spend tracking — per call, per day, per month, all-time, per model, and per session.
• Cost estimates — a built-in price table for Claude / GPT / Gemini, fully overridable; uses the harness's own reported cost when it's available.
• Soft budgets → auto-downshift — over budget, pi-meter switches the agent to a cheaper model you choose.
• Hard limits → cutoff — past a hard cap, pi-meter refuses new prompts and blocks tool calls, with a one-command override.
• Four surfaces — CLI, MCP server, Claude/Cursor skill, and pi extension, all on one core.
• Just files — the ledger is JSONL at ~/.pi-meter/usage.jsonl; config is a pi-meter.json.

Install

# CLI (global) — installs the `pimeter` command
npm install -g pi-meter

# or run without installing
npx pi-meter report

For the pi harness (installs the extension + skill):

pi install npm:pi-meter
# or from the repo:
pi install git:github.com/vaibhav-patel/pi-meter

Quick start

# record a call (the pi extension / MCP server usually does this for you)
pimeter record --model claude-opus-4-8 --input 12000 --output 3000 --label "refactor"

# where's the money going?
pimeter report

# am I within budget?
pimeter status

# set a soft budget (warn + downshift) and a hard cap (cutoff)
pimeter budget    --daily 5  --monthly 100
pimeter hardlimit --daily 10 --total 500

How it works

pi-meter has one dependency-free core behind every surface:

1. Record — each model call is priced and appended to the ledger.
2. Aggregate — spend is summed by day / month / total / model / session.
3. Enforce — spend is compared to your budget (soft) and hardLimit (hard):
   • soft budget exceeded → warn and auto-downshift to a cheaper model;
   • hard limit exceeded → cut off: refuse new prompts and block tool calls.

The ledger

One JSONL line per call at ~/.pi-meter/usage.jsonl (override with storePath):

{"ts":"2026-06-18T09:30:00Z","model":"claude-opus-4-8","provider":"anthropic","inputTokens":12000,"outputTokens":3000,"costUsd":0.225,"sessionId":"a1b2","label":"refactor"}

Greppable, portable, and yours — delete lines to forget, copy it elsewhere to analyze.

Configuration — pi-meter.json

Drop a pi-meter.json in your project root (the folder you run the agent from):

{
  "budget":    { "daily": 5, "monthly": 100, "session": 2 },   // soft  -> auto-downshift
  "hardLimit": { "monthly": 150, "total": 500 },               // hard  -> cut off
  "downshift": { "claude-opus-4-8": "claude-sonnet-4-6" },     // expensive -> cheaper
  "prices":    [ { "id": "my-model", "inputPerMTok": 1.0, "outputPerMTok": 4.0 } ],
  "storePath": "~/.pi-meter/usage.jsonl"
}

| Field | What it does | |-------|--------------| | budget | Soft limits (USD). pi-meter warns at 80%, and at 100% auto-downshifts via downshift. | | hardLimit | Hard caps (USD). Once over, the pi extension refuses prompts and blocks tools. | | downshift | Expensive-model → cheaper-model map, used when over the soft budget. | | prices | Add or override model prices (USD per 1M tokens). Wins over the built-in defaults. | | storePath | Ledger location (supports a leading ~). Defaults to ~/.pi-meter/usage.jsonl. |

Scopes for both budget and hardLimit: daily, monthly, session, and total (all-time).

CLI reference

| Command | Description | |---------|-------------| | pimeter record --model <id> --input <n> --output <n> | Record a call. Optional: --cache-read, --cache-write, --label, --session. | | pimeter report [--json] | Spend: today / month / total / by model. | | pimeter status [--session <id>] | Budget + hard-limit usage per scope (exits 1 if over). | | pimeter budget [--daily N --monthly N --session N --total N] | Show or set the soft budget. | | pimeter hardlimit [--daily N --monthly N --session N --total N] | Show or set the hard limit. | | pimeter models | List known model prices. | | pimeter mcp | Start the MCP server (stdio). |

pi extension

Once installed in pi, pi-meter runs on its own:

• Meters every turn — reads the harness's own token usage + cost and records it.
• Footer gauge — shows daily $1.20/$5.00 · monthly … live as you work.
• Auto-downshift — over the soft budget, switches to your downshift model (once per turn).
• Cutoff — over the hardLimit, refuses new prompts and blocks tool calls.
• Commands — /pimeter shows spend + budget; /pimeter override lifts a hard-limit block for the current session.

MCP server

npx pi-meter mcp starts a stdio MCP server with three tools, usable from Claude Desktop, Cursor, or any MCP client:

| Tool | Description | |------|-------------| | record_usage | Record a model call; returns its computed cost. | | get_spend | Today / month / total / by-model spend. | | check_budget | Budget status per scope, whether to downshift, and a suggested cheaper model. |

Example client config:

{ "mcpServers": { "pi-meter": { "command": "npx", "args": ["-y", "pi-meter", "mcp"] } } }

Claude / Cursor skill

The package ships a skill at skills/pimeter/SKILL.md. Drop it into your agent's skills directory (or it loads automatically when pi-meter is installed as a pi package) to teach the agent to record usage, report cost, and decide when to switch models for cost reasons.

Pricing note

The built-in price table is approximate public list pricing and will drift — verify and override anything you depend on via prices in pi-meter.json (pimeter models prints the defaults). When the harness reports its own cost (as pi does), pi-meter uses that instead of the table.

Development

npm install
npm run build      # tsc -> dist/
npm test           # node --test suite
npm run typecheck

License

MIT — see LICENSE.