Native Protocol Base URLs Reward Careful Setup

Native protocol names change more than the endpoint

Anyone who has pointed an agentic coding client at a relay knows the address is the least interesting part of the change. The protocol traveling over that address decides which fields a client may send, which response shapes it can parse, and how much of its own behavior survives the detour. Gemini CLI speaks a native Gemini protocol, so a native-protocol base URL lets the tool keep its request vocabulary intact. The model name stays in the payload where the provider expects it, streaming arrives in frames the client already understands, and tool calls round trip without an adapter inventing new fields on the way out.

A base URL that speaks only a foreign protocol forces an adapter to do the inventing, and every invented field is a place where behavior can quietly drift. The consequence shows up in long sessions rather than in the first request. Retries, cached context, partial responses, and cancellation all behave differently when the wire format was translated and then translated back. Authentication and error envelopes tend to change too, which makes a session that fails look like a session that timed out. Treating the base URL as a protocol commitment first and an address second keeps the rest of the comparison honest, because it separates transport questions from service questions.

Four criteria make a base URL comparable

Four criteria make a base URL comparable, and none of them needs a benchmark suite. Protocol fidelity asks whether the request leaving the client matches the request the upstream provider expects, field for field, including streaming frames and tool-call envelopes. Naming fidelity asks whether the model identifier carried in the payload is the model that actually answers. Accounting fidelity asks whether billed numbers come from the provider's own count of input, output, and cache tokens instead of a local estimate. Behavioral fidelity asks whether retries, partial responses, and error codes keep their original meaning after the hop.

Presenting two setups side by side works when both are described in these terms rather than in adjectives like fast or cheap. A relay that converts protocols can still be an excellent service, yet conversion is precisely where each criterion can drift, and drift compounds over a long agent session. A native-protocol base URL removes the conversion entirely, so the comparison shifts to service quality rather than to translation quality. BestRelay, a quality-first API relay, leans on that distinction. Every request is forwarded to the official model named in it, with no substitution, so the identifier in your payload is the identifier the provider serves, and the wire format it arrives in is the one the provider parses natively.

Model naming fidelity keeps routing honest

Model naming fidelity keeps routing honest, and the difference becomes visible the moment an identifier is ambiguous. Agentic clients pass model strings through unchanged, so the real question is whether the receiving side treats that string as a request or as a suggestion. A relay committed to no substitution treats it as a request. If the payload names Gemini 3.8 Flash, the request goes to Gemini 3.8 Flash. Nothing is silently moved to a cheaper tier to save cost, and nothing is upgraded to disguise a failure.

The native-protocol base URL supports that discipline because the model name arrives in a field the provider already parses. With a foreign protocol in the middle, the identifier often has to be rewritten to fit a different vocabulary, and rewriting is exactly where substitution becomes tempting, since an unmapped name has to go somewhere. The same rule holds across the catalog a relay carries, including Claude, GPT, Gemini, DeepSeek, Kimi, GLM, Qwen, Grok and more, and it matters most for coding clients that show the model name to the user and log it with each step. A logged name that disagrees with the served model makes every trace untrustworthy, including the ones you need after an incident.

Token accounting reveals whether the wire stayed clean

Billing follows the same logic as routing. When a request is translated, token counts can be estimated locally, extrapolated from characters, or rounded to hide the gap between two vocabularies. BestRelay bills pay-as-you-go from the token counts the provider itself reports, which means the numbers in your usage history are the numbers the upstream provider produced for that request. Cache reads and cache writes are priced separately, so a long agent session with a stable system prompt is billed on its real cache economics rather than on a blended average that hides them.

This distinction rewards a clean wire. A native-protocol base URL preserves the cache-control markers and the prompt structure that let a provider identify reusable context, so cache hits show up in the reported counts instead of evaporating during translation. It also keeps tool-call boundaries intact, since fragmented tool arguments inflate output tokens and confuse downstream accounting. The same provider-reported discipline applies whether the client is Claude Code, Codex, Gemini CLI, or any OpenAI SDK, and the relay's API base hostname is api.bestapirelay.com for all of them. Members also earn a referral commission when the people they invite top up, which is a separate matter from accuracy but sits on the same pay-as-you-go ledger.

Side-by-side checks catch divergence before release

Run the comparison as a checklist rather than as an argument. Point the same client at two base URLs and send an identical prompt that exercises streaming, a tool call, a long cached preamble, and a deliberate failure. Compare the payloads as the provider receives them, the model identifier actually served, the reported input and output counts, the cache read and write counts, and the shape of the error when the request fails. Any difference in those five observations is a concrete finding you can act on, and any agreement is evidence that the setup is safe to keep.

The judgement that follows from this reading is narrow and useful. Choose the base URL that speaks your client's native protocol first, then judge the relay behind it on naming fidelity and reported accounting. Gemini CLI rewards that order more than most tools, because its request vocabulary is specific and its sessions are long enough for small translation errors to become expensive. A relay that forwards each request to the official model named in it, with no substitution and with cache reads and writes priced separately, gives you a clean baseline for the test, so the only variable left is your own configuration. Create a BestRelay account and run the checklist against your own prompts.