Upgrading canisters - what happens to a spawned child canister?

@nomeata

When I build the parent canister, I only get a wasm file for the parent canister, so I can’t call install_code since there is no separate child wasm generated. (Although I do see the calls listed in the parent wasm) So I’m wondering maybe if there’s a get the updated wasm_module blob of the child canister during the upgrade process? Or a way to extract the child wasm blob out of the final wasm and upgrade manually?