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OpenAI Chat Completions (HTTP)

Fased’s Gateway can serve a small OpenAI-compatible Chat Completions endpoint. This endpoint is disabled by default. When disabled, the route is not served.
  • POST /v1/chat/completions
  • Same port as the Gateway (WS + HTTP multiplex): http://<gateway-host>:<port>/v1/chat/completions
Under the hood, requests are executed as a normal Gateway agent run (same codepath as fased agent), so routing/permissions/config match your Gateway.

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Authentication

Uses the Gateway auth configuration. Send a bearer token:
  • Authorization: Bearer <token>
Notes:
  • When gateway.auth.mode="token", use gateway.auth.token (or FASED_GATEWAY_TOKEN).
  • When gateway.auth.mode="password", use gateway.auth.password (or FASED_GATEWAY_PASSWORD).
  • If gateway.auth.rateLimit is configured and too many auth failures occur, the endpoint returns 429 with Retry-After.

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Choosing an agent

No custom headers required: encode the agent id in the OpenAI model field:
  • model: "fased:<agentId>" (example: "fased:main", "fased:beta")
  • model: "fased/<agentId>" (alias)
  • model: "agent:<agentId>" (alias)
Or target a specific Fased agent by header:
  • x-fased-agent-id: <agentId> (default: main)
  • x-fased-agent: <agentId> (alias)
Advanced:
  • x-fased-session-key: <sessionKey> to fully control session routing.

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Enabling the endpoint

Set gateway.http.endpoints.chatCompletions.enabled to true: 
{
  gateway: {
    http: {
      endpoints: {
        chatCompletions: { enabled: true },
      },
    },
  },
}

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Disabling the endpoint

Set gateway.http.endpoints.chatCompletions.enabled to false: 
{
  gateway: {
    http: {
      endpoints: {
        chatCompletions: { enabled: false },
      },
    },
  },
}

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Session behavior

By default the endpoint is stateless per request (a new session key is generated each call). If the request includes an OpenAI user string, the Gateway derives a stable session key from it, so repeated calls can share an agent session.

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Message support

  • system and developer messages become extra system instructions for the run.
  • user, assistant, tool, and function messages become conversation context.
  • Text content is supported. Non-text message parts are ignored by this compatibility endpoint.
  • Request bodies are capped at 1 MiB.
  • Usage fields are returned in the OpenAI shape, but token counts are currently 0.

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Streaming (SSE)

Set stream: true to receive Server-Sent Events (SSE):
  • Content-Type: text/event-stream
  • Each event line is data: <json>
  • Stream ends with data: [DONE]

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Examples

Non-streaming: 
curl -sS http://127.0.0.1:18789/v1/chat/completions \
  -H 'Authorization: Bearer YOUR_TOKEN' \
  -H 'Content-Type: application/json' \
  -H 'x-fased-agent-id: main' \
  -d '{
    "model": "fased",
    "messages": [{"role":"user","content":"hi"}]
  }'
Streaming: 
curl -N http://127.0.0.1:18789/v1/chat/completions \
  -H 'Authorization: Bearer YOUR_TOKEN' \
  -H 'Content-Type: application/json' \
  -H 'x-fased-agent-id: main' \
  -d '{
    "model": "fased",
    "stream": true,
    "messages": [{"role":"user","content":"hi"}]
  }'