--- title: REST API seoTitle: "Langfuse AI Gateway REST API: models, Responses, Chat Completions, Messages (beta)" description: Base URLs, authentication, and endpoints of the Langfuse AI Gateway, including the models endpoints and the OpenAI Responses, OpenAI Chat Completions, and Anthropic Messages APIs. --- # REST API **Beta.** The Langfuse AI Gateway is in public beta and can still change. You can call the gateway directly over HTTP, for example from a language without an SDK or from a script. Request and response bodies are the model provider's own, so for parameters and fields, see the provider's API reference linked in the [endpoints](#routes) table. This page covers what's specific to the gateway: base URLs, authentication, and endpoints. ## Base URLs [#base-urls] | Route | Base URL | | --------- | ------------------------------------------------- | | OpenAI | `https://gateway.cloud.langfuse.com/openai/v1` | | Anthropic | `https://gateway.cloud.langfuse.com/anthropic/v1` | These are the EU URLs. For other regions, replace the host with your [gateway host](#gateway-hosts). ### Gateway hosts [#gateway-hosts] | Region | Gateway host | | ------ | ------------------------------------------ | | EU | `https://gateway.cloud.langfuse.com` | | US | `https://gateway.us.cloud.langfuse.com` | | JP | `https://gateway.jp.cloud.langfuse.com` | | HIPAA | `https://gateway.hipaa.cloud.langfuse.com` | A gateway key only works on its own region's host. On self-hosted Langfuse, use the gateway URL your deployment configured (`LANGFUSE_AI_GATEWAY_PUBLIC_URL`, see [Self-hosting the AI Gateway](/self-hosting/configuration/ai-gateway)). ## Authentication [#authentication] Every endpoint requires a [gateway API key](/docs/gateway/features/api-keys): - **OpenAI route:** `Authorization: Bearer ` - **Anthropic route:** `x-api-key: `, or a Bearer token. If you send both, they must have the same value. ## Endpoints [#routes] | Endpoint | Provider reference | | ------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------ | | `GET /openai/v1/models` | [List models](https://developers.openai.com/api/reference/resources/models/methods/list) | | `GET /anthropic/v1/models` | [List models](https://platform.claude.com/docs/en/api/models/list) | | `POST /openai/v1/responses` | [Create a response](https://developers.openai.com/api/reference/resources/responses/methods/create) | | `POST /openai/v1/responses/compact` | [Compact a response](https://developers.openai.com/api/reference/resources/responses/methods/compact) | | `POST /openai/v1/chat/completions` | [Create a chat completion](https://developers.openai.com/api/reference/resources/chat/subresources/completions/methods/create) | | `POST /anthropic/v1/messages` | [Create a message](https://platform.claude.com/docs/en/api/messages/create) | | `POST /anthropic/v1/messages/count_tokens` | [Count tokens](https://platform.claude.com/docs/en/api/messages/count_tokens) | The models endpoints return the models your key can call, with IDs in the form `:` (see [model IDs](/docs/gateway/features/models#model-ids)). The gateway doesn't translate between formats, so the OpenAI endpoints need an OpenAI provider credential and the Anthropic endpoints an Anthropic credential. Other paths return `404`, including websockets and realtime APIs. Request bodies must be uncompressed: a `Content-Encoding` other than `identity` fails with `415`. ## Streaming usage [#streaming-usage] On streamed Chat Completions requests, the gateway sets `stream_options.include_usage` so that every call gets token usage and cost. Your client receives a final chunk with an **empty `choices` array** and a `usage` object, just before `data: [DONE]`. Code that reads `chunk.choices[0]` on every chunk needs a guard. --- ## Agent Instructions This page is part of the [Langfuse](https://langfuse.com) documentation, published as plain Markdown for AI agents. Every page is available as Markdown by appending `.md` to its URL, or by sending an `Accept: text/markdown` header. This page: `https://langfuse.com/docs/gateway/features/rest-api.md`. ### Querying these docs If the answer is not on this page, query the documentation instead of guessing: - **Semantic search** across all Langfuse docs, returning an answer with the relevant pages and excerpts. Ask a specific, self-contained question: ```bash curl -sG "https://langfuse.com/api/search-docs" --data-urlencode "query=How do I trace a LangGraph agent?" ``` - **Index of every page**: , with per-section indexes [llms-docs.txt](https://langfuse.com/llms-docs.txt), [llms-integrations.txt](https://langfuse.com/llms-integrations.txt), and [llms-self-hosting.txt](https://langfuse.com/llms-self-hosting.txt). ### Before writing Langfuse code - **Install the [Langfuse Agent Skill](https://langfuse.com/docs/api-and-data-platform/features/agent-skill).** It encodes Langfuse's own best practices for instrumentation, prompt management, and evaluation, and materially improves results. - **Read [What does a good trace look like?](https://langfuse.com/docs/observability/best-practices.md)** before instrumenting an application. - **Verify endpoints, parameters, and response fields** against the [API reference](https://api.reference.langfuse.com) instead of inferring them from code examples. - **Use the [Langfuse CLI](https://langfuse.com/docs/api-and-data-platform/features/cli)** (`npx @langfuse/cli api `) to read or write traces, prompts, datasets, and scores from the terminal. 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