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Track OpenAI cost by customer, not by project or API key

The homepage is the product. This is the playbook: how teams try to see OpenAI cost by customer, and what actually lands on a P&L.

Teams try four things. The OpenAI user field is a label on their side, not an invoice. One OpenAI project per client (the Administrate pattern) works until you have fifty customers. SDK wrappers such as LLMeter count tokens in-process; they are not a proxy. Multi-provider Stripe tools such as PerUnit bill usage across vendors — a different job.

CostSlice is the pass-through: https://api.costslice.com/v1, x-cs-key, x-cs-tenant. Keep your OpenAI API key. The P&L is by customer.

api.costslice.com/v1

from openai import OpenAI
import os

client = OpenAI(
    base_url="https://api.costslice.com/v1",
    api_key=os.environ["OPENAI_API_KEY"],
    default_headers={
        "x-cs-key": os.environ["COSTSLICE_KEY"],
        "x-cs-tenant": tenant_id,       # opaque id, never an email
        "x-cs-feature": "support-copilot",
        "x-cs-env": "prod",
    },
)

Product story: CostSlice home. Demo: sample P&L.

Starter is free. No credit card. Operated by Operator Media Yard LLC, New Jersey. hello@costslice.com