> ## Documentation Index
> Fetch the complete documentation index at: https://tanso.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.
# Concepts
> The two-halves mental model: Monetization and Internal spend on one ledger.
Tanso is one ledger fed from two directions. A customer's usage event and a
vendor's admin API both land on the same store, so the numbers on both sides
of your AI business come from the same source instead of two spreadsheets
that never quite agree.
## Monetization — the AI you sell
A customer's usage event carries what it cost you to serve, next to what you
billed for it. Metering, entitlements, credits, subscriptions and Stripe
billing all read and write the same ledger, so margin per customer, per
feature and per model falls out of it rather than requiring a separate
report. Start at [Introduction](/introduction) and [Quickstart](/quickstart).
## Internal spend — the AI you buy
Usage and cost are pulled from the vendors' own admin APIs (Anthropic,
OpenAI, Cursor, GitHub Copilot, LiteLLM) on a schedule — no proxy in the
request path, no agent on anyone's laptop. It's reconciled against the
invoice, allocated to teams and projects, budgeted, and joined to what it
produced. Start at [Internal AI spend](/internal-spend).
## Where they meet
Feature P\&L links a project on the Internal spend side to the feature it
shipped on the Monetization side, and reports that feature's revenue and
serving cost next to what it cost to build — net margin, in one number.
Nobody else can draw that table because nobody else has both halves on one
engine.
## Either half runs on its own
Neither side depends on the other being configured. Set
`APP_MODULES_MONETIZATION_ENABLED=false` for an internal-spend-only install,
or `APP_MODULES_BUILD_ENABLED=false` to run monetization alone — the other
half's routes disappear (`404 module_disabled`) and its console section
hides. See [Self-hosting](/self-hosting) for the full flag list.