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Goal. Your harness runs one model, and a single model can be confidently wrong. This recipe cross-checks your host model’s answer against two or three independent models with Fusion, right inside the same Claude Code or Codex session, so a contested or incorrect claim shows up instead of hiding behind one model’s confidence. When to reach for it. A design call, a security claim, a tricky algorithm, a “which library” decision, anything where being wrong is expensive. For an ordinary question you already trust, you do not need it.

How It Works

A single model has blind spots, and it states a wrong answer with the same fluency as a right one. You cannot tell which from the answer alone. Fusion asks several models the same question at once and synthesizes their answers. The result has two parts: each model’s own take, and a synthesis combining them, which flags material disagreements it cannot resolve. Reading the participants next to each other is what tells you whether the question is settled or contested, so you can compare that against what your harness’s own model told you. Because it runs through the plugin, all of this happens inside your existing session. You do not copy the question into another tool or lose your context; you get an independent panel in the same place you are already working.

Prerequisites

Step 1: Get your host model’s answer

Ask your harness as you normally would, for example:
Should this service use optimistic or pessimistic locking for its inventory counter?
Your host model answers. Keep that answer in mind for the comparison.

Step 2: Cross-check with a panel

Send the same question to two or three independent models with Fusion. Name models from different families so the panel is genuinely independent, not three variations of one lineage:

Step 3: Read the synthesis against your host model

Fusion returns each model’s answer plus a synthesis. Abridged and representative:
Now compare against your host model:
  • The panel agrees with your host model: you have independent corroboration. Move on.
  • The panel splits: the question is genuinely contested. Read the participants to see on what, so you can decide deliberately instead of trusting one voice.
  • The panel disagrees with your host model: the strongest signal. Read why, and re-examine the host’s answer before you act on it.

Verify a Specific Claim

To check one concrete statement rather than re-ask the whole question, paste the claim and ask a single independent model whether it holds. This works on Free:

Automate It From the Terminal

To cross-check answers outside a chat, or in a loop over several claims, run the same check from the shell. This script takes a claim and reports a panel verdict:

Variations

Fact-check with sources. For a claim about the current state of the world, let the check use web search so it returns citations:
Keep the check private. If the claim involves proprietary details, verify it with private so your harness never sends it upstream.

Troubleshooting

Where to Go Next

Fusion command

Full syntax, how to pick participants, and how privacy levels mix.

Private Code Review Pipeline

Multi-model review of your changes on Private-tier models.

Choosing a Model

How to pick strong, complementary models for a panel.

Web Search

How the web-search modes behave when you fact-check.