Inference endpoint

Run FusionKit as an OpenAI-compatible HTTP endpoint without launching a coding harness.

You can run FusionKit as a plain HTTP endpoint. This mode is useful when you want model fusion from curl, the OpenAI SDK, a custom application, or a benchmark harness without launching Codex, Claude Code, or Cursor.

fusionkit serve starts the same underlying stack as the harness launchers: RouteKit routing, the Python synthesis sidecar, and the Fusion gateway.

Prepare the engine

Install the CLI and pre-provision the Python engine so the first request does not pay the uvx cold start.

npm install -g @fusionkit/cli
fusionkit setup
fusionkit init
fusionkit doctor

Edit .routekit/router.yaml and export the provider variables named by its registry-defined credentials. FusionKit reads only namespaced RouteKit model IDs.

Start the endpoint

Run from inside the git repository you want the panel to see.

cd your-git-repo
fusionkit serve --port 8787
export FUSION_URL=http://127.0.0.1:8787

Omit --port for an ephemeral port. Configure members and judge with fusionkit ensemble; configure models and credentials in RouteKit.

The fused model id is fusion-panel. Each panel member id is also exposed for direct passthrough calls when you want to compare the ensemble against one member.

HTTP surface

The gateway exposes familiar routes under /v1.

Route	Purpose
`/v1/chat/completions`	OpenAI-compatible chat completions.
`/v1/responses`	OpenAI Responses dialect used by Codex-style clients.
`/v1/messages`	Anthropic Messages dialect used by Claude Code-style clients.
`/v1/messages/count_tokens`	Anthropic token-count helper.
`/v1/models`	Model listing in OpenAI or Anthropic shape.
`/v1/cursor/chat/completions`	Cursor BYOK hybrid: accepts Cursor's Responses-shaped body on a Chat Completions path when Cursor's base URL override points at `.../v1/cursor`. Accepts `routekit/<served-id>` and discovered `routekit/<served-id>:<effort>` model names.
`/v1/cursor/models`	Mirror of `/v1/models` for Cursor probing relative to its BYOK base URL. Advertises every id as `routekit/<served-id>` and reasoning-capable models as one `:<effort>` variant per discovered effort.
`/v1/embeddings`	Embeddings route when the configured backend supports it.
`/health`	Unauthenticated health check.

Streaming example

curl -N "$FUSION_URL/v1/chat/completions" \
  -H 'content-type: application/json' \
  -d '{
    "model": "fusion-panel",
    "stream": true,
    "messages": [
      { "role": "user", "content": "Explain a B-tree in two sentences." }
    ]
  }'

The -N flag disables curl buffering so you can see Server-Sent Events as they arrive. Remove "stream": true for a single JSON response.

Tool-calling example

Tools are passed through the panel and judge. When the ensemble decides to call a tool, the response contains a tool_calls array in the OpenAI Chat shape.

curl "$FUSION_URL/v1/chat/completions" \
  -H 'content-type: application/json' \
  -d '{
    "model": "fusion-panel",
    "messages": [
      { "role": "user", "content": "What is the weather in Paris?" }
    ],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_weather",
        "description": "Get the current weather for a city",
        "parameters": {
          "type": "object",
          "properties": {
            "city": { "type": "string" }
          },
          "required": ["city"]
        }
      }
    }]
  }'

Execute the tool in your application and continue the conversation with a tool message, the same way you would with the OpenAI API.

Auth and binding

Loopback usage can run without auth. If you bind the gateway beyond loopback, require a token.

fusionkit serve --port 8787 --auth-token "$FUSIONKIT_GATEWAY_TOKEN"

Then send either Authorization: Bearer <token> or x-api-key: <token>.

When to use this instead of a harness launcher

Use fusionkit serve when your application already owns the conversation loop, when you want to benchmark the endpoint directly, or when you want a familiar OpenAI-compatible URL. Use fusionkit codex, fusionkit claude, or fusionkit cursor when you want an existing coding agent to be wired automatically with its native protocol and tool loop.