DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.
Both async and sync mkdir with recursive: true now catch EEXIST errors, fixing race conditions where parallel operations could fail when two processes try to create the same directory simultaneously.
Evidence
EEXIST handling in mkdir (search for "EEXIST" in the filesystem module at line ~3495)
Strings lifted out of the shipped bundle, so the claim above can be checked against them.