Fusion MoA

简体中文

One model API for coding agents, backed by your main model and independent expert models.

Fusion MoA is an open, model- and GPU-independent Mixture-of-Agents runtime. You connect the model endpoints you already use, choose an orchestration recipe, and expose one OpenAI- or Anthropic-compatible model to Claude Code, Codex, OpenCode, DeepSeek Harness, or another coding agent.

Coding agent
    │  OpenAI Chat / Responses / Anthropic Messages
    ▼
Fusion MoA  ── policy, budgets, fallback, accounting
    │
    ├── authoritative main model ──► native final stream
    └── independent read-only experts ─► private corrections only

The main model is always the only public writer. Experts receive no coding tools, their output is bounded and treated as untrusted, and the recommended expert-constrained policy requires a valid independent review before final generation. Fusion MoA does not require a particular model family, inference server, cloud, GPU, or coding-agent harness.

What works today

The current community release provides:

• one fusion/v1 YAML recipe for providers, models, pools, policies, completion rules, and serving;
• OpenAI-compatible and Anthropic-compatible upstream providers;
• OpenAI Chat Completions, OpenAI Responses, and Anthropic Messages client endpoints;
• native streaming from the authoritative final model, including incremental tool-call arguments;
• portable function/tool-call round trips and /v1/models discovery;
• direct, reasoning-reserve, critic, review-board, adaptive self-review, and mandatory expert-constrained policies;
• explicit capability checks for thinking controls, tools, and schema-constrained output;
• bounded fallback, usage aggregation, and completeness flags across all model calls;
• Python entry points for third-party provider and policy plugins;
• a version-pinned DeepSeek Harness integration.

Fusion MoA is early-stage software. Expert orchestration can cost more or perform worse than direct inference on some workloads. Keep direct as an experimental control, and validate the complete expert path on your own coding tasks before using it in production.

Quick start

Requirements: Python 3.11+ and at least one model endpoint. A local vLLM, SGLang, llama.cpp, or any service with an OpenAI-compatible Chat Completions API is enough for the first run.

1. Install

git clone https://github.com/xiaohou521/fusion-moa.git
cd fusion-moa
python3 -m venv .venv
. .venv/bin/activate
pip install .

2. Configure one main model

cp recipes/direct.yaml fusion.yaml

Edit these values in fusion.yaml:

providers:
  main_api:
    base_url: http://127.0.0.1:8000/v1

models:
  main:
    model: your-coding-model-id

Secrets are referenced by environment-variable name and never written into the recipe:

export MAIN_MODEL_API_KEY='your-upstream-key'
export FUSION_RUNTIME_API_KEY='choose-a-key-for-coding-agents'

If the local upstream does not require authentication, remove api_key_env from that provider.

3. Validate and start

fusion-runtime --config fusion.yaml --check
fusion-runtime --config fusion.yaml --host 127.0.0.1 --port 18888

Check the gateway:

curl http://127.0.0.1:18888/health

Send a native streaming request:

curl http://127.0.0.1:18888/v1/chat/completions \
  -H "Authorization: Bearer $FUSION_RUNTIME_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
    "model": "fusion-coding",
    "stream": true,
    "messages": [{"role": "user", "content": "Write a Python binary search."}]
  }'

4. Connect a coding agent

For an OpenAI-compatible client:

Base URL: http://127.0.0.1:18888/v1
API key:  value of FUSION_RUNTIME_API_KEY
Model:    fusion-coding

For Claude Code through CC Switch, create a custom Anthropic-compatible provider:

Base URL: http://127.0.0.1:18888
API key:  value of FUSION_RUNTIME_API_KEY
Model:    fusion-coding

The Anthropic client adds /v1/messages; OpenAI clients use the /v1 base URL. Keep the runtime on loopback unless you have added TLS, network access controls, and a strong API key.

Run with required expert review

Start from the expert-constrained recipe:

cp recipes/expert-constrained.yaml fusion.yaml
export MAIN_MODEL_KEY='your-main-model-key'
export PRIMARY_EXPERT_KEY='your-primary-expert-key'
export BACKUP_EXPERT_KEY='your-backup-expert-key'
export FUSION_RUNTIME_API_KEY='choose-a-key-for-coding-agents'

Edit the three endpoint URLs and model IDs, then validate and start as above. The request path is:

main model selects a private plan and final-answer budget
        ▼
primary independent expert returns a compact structured correction
        │ retry the same tier on a retryable transport error
        └ use the independent backup if the primary still fails
        ▼
authoritative main model applies only the correction delta and streams natively

Each reviewer endpoint must support provider-enforced JSON Schema. A valid review is either abstain or a bounded advise object containing only a risk class, up to three must-fix items, one counterexample, and a solution delta. The main model selects its final-answer budget before seeing the review, so expert text cannot expand compute. The default expert tiers are 512 → 1024 → 2048; a higher tier is used only for an explicitly truncated JSON response at its current ceiling.

Expert review is mandatory for this policy. A retryable primary transport failure is retried once at the same tier, then the backup is tried. If no configured independent expert produces a valid review, the request fails with required_expert_failed; it never silently becomes direct inference. Only the final main-model call retains the coding agent's tools, and only that call is streamed to the client.

Inspect response headers while testing:

• x-fusion-route shows the expert attempt, selected tier, review action, and final budget;
• x-fusion-fallback reports bounded recovery information when present;
• x-fusion-streaming-mode: native-final confirms final-model streaming.

Choose a recipe

Every recipe has six sections:

1. providers: endpoint transports and environment-variable credential references;
2. models: upstream model IDs, limits, tools, and declared generation capabilities;
3. pools: one authoritative main model and role-named experts;
4. policy: orchestration and hard expert budgets;
5. completion: public-output requirements and optional bounded recovery;
6. serve: the public model name and enabled client protocols.

Capabilities are declarations, not guesses based on model names. Only declare disabled or bounded thinking when the provider plugin really maps that control. Only declare json-schema when the upstream endpoint enforces it. Unsupported combinations fail visibly before inference.

Plugins and integrations

Third-party Python packages can register providers under fusion_runtime.providers and policies under fusion_runtime.policies. Provider plugins own upstream protocol translation; policy plugins own bounded orchestration; the gateway owns client-protocol translation and the final stream.

The repository also contains a community-maintained DeepSeek Harness profile bundle. It uses the Harness's generic OpenAI-compatible model seam and does not imply upstream endorsement.

In development

The active roadmap focuses on:

• checkpointed, model-independent evaluation and public Evidence Cards;
• direct and matched-compute controls that separate expert value from extra inference cost;
• expert-role routing that always selects at least one independent expert while optimizing which expert should review each task;
• privacy-safe outcome storage, failure clustering, and reusable failure taxonomies;
• offline, evaluation-gated recipe evolution with lineage, rejection, promotion, and rollback;
• more provider, coding-agent, and community expert-pool plugins;
• optional training/model-adapter plugins that remain outside the core runtime.

This roadmap does not mean a production model can currently rewrite runtime code, modify its own weights, or promote itself online. Fusion MoA uses “RSI” to mean a controlled offline loop: observe failures → propose a bounded recipe candidate → run frozen evaluation → explicitly accept or reject it.

Evidence, security, and contributing

Fusion is not automatically better than direct inference. Published aggregate experiments live in benchmarks/cards; they document both accepted and rejected hypotheses and do not contain private endpoints, credentials, raw prompts, or model responses.

• Keep credentials in environment variables, never YAML or Git.
• Treat recipes and installed plugins as trusted deployment code.
• Treat user input, model output, and expert advice as untrusted data.
• Read SECURITY.md before exposing the gateway outside localhost.
• See CONTRIBUTING.md for provider, policy, recipe, and evaluation contributions.

License

Apache-2.0.