A CLAUDE.md in a subdirectory says one thing about formatting and the one at your project root says another. What is the effect?

The principle — instruction files add up rather than override, so a contradiction stays a contradiction.

Why the key is correct — Anthropic states that all discovered files are concatenated into context rather than overriding each other, and separately that if two rules contradict each other, Claude may pick one arbitrarily. Put those together and both instructions are present, neither cancels the other, and which one is followed is not something you can predict from where the files sit.

Why the others are wrong — expecting the nested file to replace the root one imports an override model that does not operate here. Specificity-wins is the same import from a different direction, familiar from CSS and layered config, and equally absent. And nothing invalidates a contradictory pair; there is no validation step to reject them.

Remember this — audit your instruction files for disagreement periodically. A contradiction is worse than an omission, because it fails silently and inconsistently.

Sources — Anthropic's memory page.