Cross-Dialect Egress

The gateway’s /router surface lets you keep writing requests in one provider’s dialect while the gateway egresses to a different provider. You send an Anthropic Messages-shaped request to /router/anthropic, select OpenAI as the egress target, and the gateway translates the request into OpenAI’s format on the way out and translates the response back into Anthropic’s format on the way in. Your code speaks Anthropic conventions end to end; the served model is OpenAI’s. This is useful when your application is already built against the Anthropic Messages API — SDKs, prompt templates, response parsing — and you want to serve an OpenAI model without rewriting the integration to OpenAI’s request/response shape.

Today the only covered cross-dialect pair is Anthropic → OpenAI: an Anthropic-shaped request routed to OpenAI. Other combinations are not substituted — the router fails closed rather than guessing at a translation it does not support.

How it differs from the provider doors

The provider doors (/anthropic, /openai, /gemini) are passthrough: you speak each provider’s native dialect at its own path, and the gateway forwards to that same provider. The /router surface adds dialect translation — you speak Anthropic, the gateway speaks OpenAI upstream — and it carries its own egress-key contract: you supply the OpenAI key for the upstream leg on the request.

Endpoint

POST https://gateway.mnemom.ai/router/anthropic/v1/messages

Headers

Header	Required	Value
`x-api-key`	Yes	Your existing Mnemom gateway credential — the same one you use for the `/anthropic` door. It authenticates you at the gateway and is stripped before egress; it is never sent to OpenAI.
`Content-Type`	Yes	`application/json`
`x-mnemom-provider`	Yes	Routing directive selecting the egress provider. To egress to OpenAI: `{"only":["openai"]}`.
`x-mnemom-egress-key`	Yes	Your OpenAI API key, used only for the upstream leg. The gateway injects it as `Authorization: Bearer <key>` to OpenAI. It is never logged.

x-api-key and x-mnemom-egress-key are two different credentials with two different jobs. x-api-key is your Mnemom gateway credential and authenticates the call to Mnemom — it never leaves the gateway. x-mnemom-egress-key is your OpenAI key and is used only to call OpenAI upstream. Do not swap them.

Request body

Send a standard Anthropic Messages body. Use Anthropic conventions throughout — model, max_tokens, messages, system, and so on. The gateway maps them to OpenAI’s equivalents automatically (for example, max_tokens becomes OpenAI’s max_completion_tokens). The model field must name a supported OpenAI model (see Supported models):

{
  "model": "gpt-5.6-sol",
  "max_tokens": 256,
  "messages": [
    { "role": "user", "content": "Explain retrieval-augmented generation in two sentences." }
  ]
}

Supported models

The model in a cross-dialect request must be one of the supported OpenAI model IDs:

gpt-5
gpt-5-codex
o3
o3-mini
gpt-5.6-sol
gpt-5.6-terra
gpt-5.6-luna

Example

curl https://gateway.mnemom.ai/router/anthropic/v1/messages \
  -H "x-api-key: $MNEMOM_API_KEY" \
  -H "Content-Type: application/json" \
  -H 'x-mnemom-provider: {"only":["openai"]}' \
  -H "x-mnemom-egress-key: $OPENAI_API_KEY" \
  -d '{
    "model": "gpt-5.6-sol",
    "max_tokens": 256,
    "messages": [
      {"role": "user", "content": "Explain retrieval-augmented generation in two sentences."}
    ]
  }'

curl -N https://gateway.mnemom.ai/router/anthropic/v1/messages \
  -H "x-api-key: $MNEMOM_API_KEY" \
  -H "Content-Type: application/json" \
  -H 'x-mnemom-provider: {"only":["openai"]}' \
  -H "x-mnemom-egress-key: $OPENAI_API_KEY" \
  -d '{
    "model": "gpt-5.6-sol",
    "max_tokens": 256,
    "stream": true,
    "messages": [
      {"role": "user", "content": "Explain retrieval-augmented generation in two sentences."}
    ]
  }'

Response

The gateway returns a standard Anthropic Messages response, regardless of the fact that an OpenAI model served it. You parse the same content blocks, stop_reason, and usage fields you already parse for the /anthropic door. The model field echoes the OpenAI model that served the request.

{
  "id": "msg_...",
  "type": "message",
  "role": "assistant",
  "model": "gpt-5.6-sol",
  "content": [
    { "type": "text", "text": "Retrieval-augmented generation ..." }
  ],
  "stop_reason": "end_turn",
  "usage": { "input_tokens": 18, "output_tokens": 42 }
}

Streaming

Add "stream": true to the body and the gateway streams the response back as Anthropic Server-Sent Events — not raw OpenAI chunks. You receive the same event sequence the /anthropic door emits:

message_start
content_block_start
content_block_delta
content_block_stop
message_delta
message_stop

Client code written to consume Anthropic streaming events works unchanged. The gateway translates OpenAI’s streaming chunks into this Anthropic event shape for you.

Errors

Errors surface in the Anthropic error envelope — the same shape the /anthropic door returns — so your existing error handling applies:

{
  "type": "error",
  "error": {
    "type": "...",
    "message": "..."
  }
}

Condition	Status	Detail
Missing `x-api-key`	`401`	The gateway credential is required to authenticate the request.
Routing directive set but `x-mnemom-egress-key` missing	`400`	Error code `cross-dialect-egress-credential-required`. A cross-dialect egress needs your OpenAI key on the request.
Upstream provider error	Upstream status preserved	The gateway wraps the upstream error in the Anthropic error envelope above and preserves the upstream HTTP status.

Gateway Quickstart — the passthrough provider doors (/anthropic, /openai, /gemini)
Provider Support — per-provider feature coverage across Anthropic, OpenAI, and Gemini
Headers reference — the full set of gateway response headers

Overview

Identity & Cards

Posture & Policy

Detection & Safe House

AEGIS

Reputation & Risk

Lifecycle

Gateway

Pricing

Migrations

Policy

Specifications

Changelog

How it differs from the provider doors

Endpoint

Headers

Request body

Supported models

Example

Response

Streaming

Errors

​How it differs from the provider doors

​Endpoint

​Headers

​Request body

​Supported models

​Example

​Response

​Streaming

​Errors

​Related

How it differs from the provider doors

Endpoint

Headers

Request body

Supported models

Example

Response

Streaming

Errors

Related