What is tree-of-thought prompting?
Tree-of-thought treats problem solving as a search. Instead of producing one linear chain of reasoning and committing to it, the model generates several candidate "thoughts" at each step, evaluates how promising each is, and only continues down the branches worth pursuing. Weak branches are pruned; strong ones are expanded. The result is a tree, and the answer is the best leaf.
The key difference from plain chain-of-thought is the explicit evaluation and backtracking. CoT is one path; if it goes wrong early, the whole answer is wrong. ToT keeps multiple paths alive and can abandon a dead end, which is why Yao et al. 2023 showed large gains on tasks where lookahead and backtracking matter, like the Game of 24 and creative planning.
In a research setting ToT runs as an actual search algorithm (breadth-first or depth-first) with a separate evaluator model. In day-to-day prompting you usually approximate it inside a single conversation: ask for branches, ask for scores, then ask for expansion of the winner. That captures most of the benefit without orchestration code.