Concepts
Core concepts
Panels, judges, synthesizers, fused models, passthrough models, sessions, and rate-limit handoff.
FusionKit's product concepts start with model fusion: a single request is routed to multiple model endpoints, each endpoint produces an independent candidate or harness trajectory, and a judge/synthesizer returns the final response. The same idea works as a raw inference endpoint and behind Codex, Claude Code, and Cursor.
Glossary
| Term | Meaning |
|---|---|
| Panel | The set of model endpoints that receive the same task. A panel can mix OpenAI, Anthropic, Gemini, OpenAI-compatible endpoints, OpenRouter models, and local MLX models. |
| Judge | The model or process that compares candidates and decides how to synthesize the final answer. |
| Synthesizer | The final-output step that writes the answer in the caller's native shape. It often uses the judge model unless configured separately. |
| Fusion / ensemble | Used interchangeably in older docs and commands; fusion is the preferred product term. |
| Fused model | A model id that runs panel fanout + judge + synthesis. In the Node gateway, the default fused id is fusion-panel. |
| Passthrough model | A direct model id for one panel member, such as gpt, sonnet, or kimi; it skips synthesis unless rate-limit handoff fires. |
fusion-panel | The gateway model id exposed to Codex, Claude Code, Cursor, and OpenAI-compatible clients through the Node gateway. |
| Internal fusion aliases | Names such as fusionkit/panel remain internal engine mode aliases and benchmark compatibility values. Public clients use fusion-panel or fusion-<name> on the Node gateway. |
| Handoff | Rate-limit failover from a failed passthrough turn to the fused panel. See Rate-limit handoff. |
Product concepts
| Concept | Meaning | Where to read more |
|---|---|---|
| Candidate | One panel member's answer or harness trajectory before synthesis. | Model fusion |
| Trajectory | A structured record of a harness attempt: messages, tool calls, observations, failures, and final answer. | Model fusion |
| Fusion gateway | The local HTTP gateway that speaks the caller's native dialect while routing fused and passthrough models. | Command reference |
| Python sidecar | The PyPI fusionkit package, provisioned through uvx, that accepts internal trajectory-fusion and native-run requests. It has no public chat or model routes. | Package map |
.fusionkit/ config | The committed per-repo source of truth for panels, judge, tool defaults, run defaults, and prompts. | Configuration |
| Durable session | Gateway state that can be resumed with --resume <id> or --continue. | Command reference |
| Rate-limit handoff | Fallback from a throttled vendor passthrough model to the fused panel. | Rate-limit handoff |
The repository also preserves older platform code under legacy/. None of it is needed to run FusionKit; Product scope explains the boundary.