$ rustup update nightly
$ cd .rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin
$ ./cargo-fmt --version
rustfmt 1.8.0-stable (4d91de4e48 2025-02-17)
$ ./rustfmt --version
rustfmt 1.8.0-nightly (85abb27636 2025-02-25)

The version has a different date than rustfmt, which I would perhaps understand, but it's a bit weird that it says -stable even though it's in the nightly toolchain.

It's possible that #137541 might fix this, we'll see after the next nightly is released.