Supported APIs

Overview

The LLM Gateway exposes one gateway URL, https://llm-gateway.aptible.com, and speaks several API dialects from it. Pick whichever matches how you’re already integrating:

OpenAI-compatible — Chat Completions, Responses, and Embeddings, in both a strict /openai namespace and as un-namespaced defaults
Anthropic-compatible — Messages, in a strict /anthropic namespace
Agent harnesses — a dedicated, never-changing base URL per supported coding assistant or agent harness, under /harness/<name>

Every request authenticates with an LLM Key and selects a model by name in the request body — see Supported Models for the current model catalog.

Authentication

Send your LLM Key as a bearer token:

Authorization: Bearer <YOUR_LLM_KEY>

Anthropic’s SDKs (and Claude Code) instead send an x-api-key header — the gateway accepts either:

x-api-key: <YOUR_LLM_KEY>

OpenAI-compatible API

Use the /openai namespace for strict OpenAI compatibility:

Endpoint	Path
Chat Completions	`POST /openai/v1/chat/completions`
Responses	`POST /openai/v1/responses`
Embeddings	`POST /openai/v1/embeddings`

The same three endpoints are also available un-namespaced (/v1/chat/completions, /v1/responses, /v1/embeddings) as the gateway’s default dialect — use whichever your SDK or tooling expects. For full request and response documentation, see OpenAI’s API reference.

Anthropic-compatible API

Use the /anthropic namespace for Anthropic Messages:

Endpoint	Path
Messages	`POST /anthropic/v1/messages`
Count Tokens	`POST /anthropic/v1/messages/count_tokens`

For full request and response documentation, see Anthropic’s API reference.

Agent harness support

Some coding assistants and agent harnesses need a single base URL they can be pointed at once and never have to edit again — even as the underlying API dialect they speak evolves. The LLM Gateway provides one under /harness/<name>, which resolves internally to the right compatibility endpoint:

Harness	Base URL
Claude Code	`https://llm-gateway.aptible.com/harness/claude-code`
Claude Desktop	`https://llm-gateway.aptible.com/harness/claude-desktop`
Grok Build	`https://llm-gateway.aptible.com/harness/grok-build`
Pi	`https://llm-gateway.aptible.com/harness/pi`

See the Claude Code guide for a full walkthrough of harness setup.

Don’t see your harness or coding assistant listed? Any tool that speaks OpenAI- or Anthropic-compatible APIs already works against the /openai or /anthropic endpoints above — a dedicated /harness route just saves you from ever having to change the base URL again. Contact us if you’d like a harness added.

Example requests

Every example below uses the model field to select a model — see Supported Models for valid IDs.

curl https://llm-gateway.aptible.com/openai/v1/chat/completions \
  -H "Authorization: Bearer $LLM_GATEWAY_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5",
    "messages": [
      {"role": "user", "content": "Tell me a joke about cloud security"}
    ]
  }'

curl https://llm-gateway.aptible.com/openai/v1/responses \
  -H "Authorization: Bearer $LLM_GATEWAY_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5",
    "input": "Tell me a joke about cloud security"
  }'

curl https://llm-gateway.aptible.com/anthropic/v1/messages \
  -H "x-api-key: $LLM_GATEWAY_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-5",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Tell me a joke about cloud security"}
    ]
  }'

Automatic provider failover and client-side fallbacks

If a model is available from more than one provider, the gateway automatically fails over to another available provider during an outage — no client changes required. You can also specify your own fallback models in a request; see Supported Models for details on both.

Getting Started

Platform

Managed AI

Reference

Overview

Authentication

OpenAI-compatible API

Anthropic-compatible API

Agent harness support

Example requests

Automatic provider failover and client-side fallbacks

​Overview

​Authentication

​OpenAI-compatible API

​Anthropic-compatible API

​Agent harness support

​Example requests

​Automatic provider failover and client-side fallbacks

Overview

Authentication

OpenAI-compatible API

Anthropic-compatible API

Agent harness support

Example requests

Automatic provider failover and client-side fallbacks