Conversations across models

llmshim does not store conversations. A conversation continues because the caller sends the previous messages again.

Start with a history:

[
  { "role": "user", "content": "What is a Rust closure?" },
  { "role": "assistant", "content": "A closure is..." },
  { "role": "user", "content": "Explain that another way." }
]

Send it to another provider by keeping messages and changing the address:

- "model": "anthropic/claude-opus-4-8"
+ "model": "openai/gpt-5.6-sol"

There is no session handoff between Anthropic and OpenAI. The new provider sees the history because it is present in the new request.

Who owns history?

• Rust applications keep and resend their own messages array.
• HTTP callers and language clients do the same. The proxy is stateless and does not assign conversation IDs.
• llmshim chat keeps history in memory for the interactive process. The /model command changes the model for the next request without clearing that history; /clear removes it.

Provider adapters translate recognized cross-provider artifacts before sending the history upstream. This includes common message roles and supported tool call/result shapes. They also remove provider-only response metadata that should not be sent to another API.

That translation makes a shared history usable across providers, but it does not make every provider-specific detail portable. A turn that depends on a native extension, unsupported content block, or provider-only behavior can still lose that behavior after a switch.

What model switching does not do

Changing the model does not:

• summarize or truncate history;
• run more than one model;
• choose a model automatically;
• persist messages after the caller or CLI process discards them.

Multi-model conversation is therefore a small operation: preserve the history, choose a new model address, and send the next request.