llm-meter 0.3.3

Accurate LLM usage & cost tracking for Python backends (FastAPI-native)

llm-meter 📊

Accurate LLM usage & cost tracking for Python backends.

llm-meter solves the "black box" of LLM costs by providing framework-native (FastAPI) instrumentation that attributes every token, cent, and millisecond to your business-level concepts (User ID, Feature, Endpoint).

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⚡ 15-Minute Setup

# Using uv (recommended)
uv add llm-meter

# or pip
pip install llm-meter

1. Initialize & Instrument

from fastapi import FastAPI
from llm_meter import LLMMeter, FastAPIMiddleware
from openai import OpenAI

# 1. Initialize SDK
meter = LLMMeter(
    storage_url="sqlite+aiosqlite:///llm_usage.db",
    providers={"openai": {"api_key": "YOUR_KEY"}}
)

app = FastAPI()

# 2. Add Middleton for automatic attribution
app.add_middleware(FastAPIMiddleware, meter=meter)

# 3. Wrap your client
client = meter.wrap_client(OpenAI())

@app.post("/generate")
async def generate(prompt: str):
    # This call is automatically tracked and attributed to "/generate"
    response = client.chat.completions.create(
        model="gpt-4",
        messages=[{"role": "user", "content": prompt}]
    )
    return {"text": response.choices[0].message.content}

2. Inspect via CLI

# Get a high-level summary
llm-meter usage summary

# See which endpoint costs the most
llm-meter usage by-endpoint

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🎯 Key Features

• Accounting, not Observability: Focuses on cost attribution and usage tracking, not heavy traces or prompt logging.
• FastAPI Native: Middleware handles request_id and context propagation automatically.
• Async-Safe: Powered by contextvars to ensure usage is correctly attributed even in complex async workflows.
• Proxy-Free: Works via SDK-level instrumentation (no network interception or latency overhead).
• Self-Hosted: You own your data. Supports SQLite (default) and PostgreSQL.

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⚠️ v1 Limitations

• Supports OpenAI and Azure OpenAI.
• Batch token tracking (Streaming support coming in v1.1).
• No web UI (everything is available via CLI or SQL).

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🧪 Testing, Linting & Type Checks

To run all tests and check coverage:

uv run pytest --cov=llm_meter --cov-report=term-missing

To run linting and formatting checks with Ruff:

uv run ruff check . --fix
uv run ruff format .

To run type checking with Pyright:

uv run pyright

To run all pre-commit hooks manually:

uv run pre-commit run --all-files

These commands help ensure code quality, style, and type safety before committing changes.

🛠 Contributing

We love contributions! Please see CONTRIBUTING.md for details on how to get started.

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📄 License

This project is licensed under the MIT License - see the LICENSE file for details.