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.
Template placeholders no longer pick up built-in property names
You'll notice
Useful2Signal2
Elsewhere
Template placeholders like {{constructor}} stay as text instead of expanding into junk.
What's wrong with this entry?
Anonymous. No account, no email.
What
Substituting {{name}} in a prompt or command template now requires the key to be defined directly on the supplied values. Names inherited from JavaScript's base object, such as constructor or toString, are left as literal text instead of being replaced with function source.
Evidence
Object.hasOwn(t, i) ? (t[i] ?? o) : o
Strings lifted out of the shipped bundle, so the claim above can be checked against them.