Cargo installed from (what should be) `2025-10-06` toolchain claims to be version `2025-10-04`

[justDeeevin]

I'm trying to contribute to rust-clippy and, for some reason, when including pkgs.rust-bin.nightly."2025-10-06".default in my devshell's buildinputs, cargo --version spits out 2025-10-04. Running which cargo shows that it's coming from the package rust-default-1.92.0-nightly-2025-10-06, so I'm not sure if this is a bug with cargo or the overlay or what. However, I'm not able to run clippy's tests because they require access to rustup and when I include rustup in my devshell's packages it detects that my current cargo isn't the same version as that specified in rust-toolchain.toml and tries to download the right one.

I get the same problem using fromRustupToolchainFile and when using override to manually fetch the right toolchain.

Any idea what might be going on here?