What are reasoning models?
Also: Thinking models, chain of thought
Reasoning models spend extra computation working through a problem in steps before answering. In assistants they often plan searches and weigh sources, which can change which brands appear compared with a quick-reply model. Answer behaviour therefore depends on the selected model and mode, not only the assistant.
Consequences for tracking
Test with a fixed engine and setting, and note when a provider changes defaults. A change in the default model can alter your visibility overnight, as described under model drift.
Example: a reasoning model breaks a software question into four searches and compares sources before naming two tools.