Gateway, aggregator, or direct: get the taxonomy right first.

Quick answer: two questions sort every product.

Question one: who runs the routing layer, the software that accepts your request and forwards it to a model vendor? Either nobody (you call vendors directly), you (a router deployed in your infrastructure), or a third party (a hosted endpoint). Question two: who holds the vendor accounts and pays the vendors? Either you hold a billing relationship per vendor, or the routing operator holds them and resells capacity to you as one bill. Direct integration answers nobody/you: no router, your accounts. A self-hosted gateway answers you/you: your router, your accounts, list prices. A hosted aggregator answers them/them: their router, their vendor accounts, one key and one bill for you. There is a fourth cell, a hosted router where you bring your own vendor keys, which some cloud gateways offer; it behaves like a self-hosted gateway operationally, minus the self-hosting. Every product in this market sits in one of those cells, whatever its landing page calls itself. APIsRouter, for the record, is a hosted aggregator: one OpenAI-compatible endpoint, one prepaid balance, the vendor relationships held on our side.

How each model works, mechanically.

Direct: your service imports each vendor's SDK or calls its HTTP API, authenticated with that vendor's key. Requests travel straight to the vendor. You own retries, rate-limit handling, failover, usage rollups, and one billing relationship per vendor. Nothing sits between you and the model, and nothing helps you either. Self-hosted gateway: you deploy a router, open-source projects like LiteLLM and one-api are the canonical examples, inside your own infrastructure. Your application calls the router on one OpenAI-compatible interface; the router holds your per-vendor keys and forwards each request by model id, normalizing shapes where vendors differ. You gain the unified interface, central key custody, and one place for retries and metering; you also acquire a service to operate, upgrade, and monitor, and your token prices remain each vendor's list. Hosted aggregator: your application calls a third-party endpoint with one key. The aggregator's router forwards to vendors under its own accounts and bills you per token or per image from one balance. You gain everything the self-hosted router gives, with zero operations, no per-vendor sign-ups, and often unit prices below vendor list, since aggregators can pool capacity. You accept a third party in the request path, both for availability and for data transit, which is the honest cost of the lane.

The taxonomy in one table.

Same two questions, laid out with their consequences. For the deep two-way comparison of direct versus gateway-shaped architecture, including a worked month of production traffic priced both ways, see the companion guide linked below; this table stays at the taxonomy level.

Where the marketing muddies it.

The practical defense against terminology soup is to ask the two taxonomy questions of any product you evaluate. Five minutes with the pricing page answers both: if there is a per-token price sheet, vendor accounts are theirs; if there is a deployment guide, the router is yours.

• Gateway is used for both the self-hosted routers and the hosted resellers; when a product page says gateway, check whether you bring vendor keys (router) or top up a balance (aggregator). The billing model is the tell.
• Aggregator and unified API usually mean the reseller cell, but some unified APIs are bring-your-own-key routers hosted in someone's cloud: router semantics, hosted convenience.
• Proxy usually describes a thin pass-through in front of one vendor, a special case of the router with a catalog of one.
• Router is overloaded twice: infrastructure routing (this page) and model routing, choosing which model answers a prompt. A product can do either or both; the words do not distinguish, the feature list does.
• OpenAI-compatible is orthogonal to all of it: every cell can expose the same /v1 interface, which is precisely why your application code should not care which cell serves it.

Pay-as-you-go · transparent per-model pricing

Selected models are priced below official list prices. Exact input, output, cache, and per-request prices are shown for each model.

The decision path.

One provider, provider-exclusive features, or compliance that forbids intermediaries: go direct. This is a genuine lane, not a fallback; a single-vendor product gains nothing from a router it does not need. Multiple model families, strict data-path control, and an infrastructure team that will own another service: self-hosted gateway. You get unified routing with your traffic never leaving your perimeter except to vendors, and you pay for it in operations and in list-price tokens. Multiple model families and a preference for shipping over operating: hosted aggregator. One integration, one key, one bill, models from every major family, and unit pricing that is usually the best of the three lanes. Accept the third party in the path deliberately, read the provider's data handling terms, and keep the escape hatch below. The escape hatch is the same for every lane, and it is the most important sentence on this page: code against the OpenAI-compatible surface with base URL and model id as configuration. Do that, and the three cells become deployment choices you can revisit per environment, staging on an aggregator, production direct, or the reverse, rather than architectural commitments. Teams migrate between cells in an afternoon when the interface stayed portable, and rewrite for a quarter when it did not.

Mixing lanes is normal, not indecision.

Mature stacks usually occupy two cells at once, on purpose. A common shape: the aggregator serves development, evaluation, and the long tail of models, because one key against a broad catalog is unbeatable for iteration speed, while one anchor vendor stays direct for a compliance-scoped workload or a provider-exclusive feature. Another: a self-hosted router fronts everything on-perimeter, with an aggregator configured as one of its upstreams for the families the team has no direct account with. Both shapes fall out of the same portable-interface discipline, and both keep the aggregator's strongest property in play: when a new model ships from any vendor, it appears in the catalog behind the key you already have, and trying it is a one-string change. That, more than any single month's unit price, is what the reseller cell is actually selling: option value on a fast-moving model market.

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