Why not using a proxy in claudecode to forward all the claude-* model to anthropic as a standard proxy forwarder and route other models to other providers (openrouter, vllm, ..)? This way Claude's model can get all the context from other models as all in the same harness. To use other models than claude-* you can use agents files.
Ps: as you won't use your proxy to distill or alter claudecode requests to anthropic you should be compliant with anthropic rules.
Probably depends if you're trying to treat it as "subagent(s)" or as two different models working on the same stream of thought/context.
Both are, I think, valid options. Depends on the workflow you're looking for.