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-# .drvPath inconsistencies / Why .drvPath differs between Nix and Tvix
-
-Nix and Tvix currently use a different approach when it comes to tracking input
-references, in order to build the right dependencies in advance.
-Nix is using string contexts, whereas Tvix is doing reference scanning [^inbox-drvpath].
-
-There are some real-life cases, for example during nixpkgs bootstrapping, where
-multiple different fixed-output derivations are written to produce the same
-hash.
-
-For example, bootstrap sources that are downloaded early are fetched using
-a special "builder hack", in which the `builder` field of the derivation is
-populated with the magic string `builtin:fetchurl` and the builder itself will
-perform a fetch, with everything looking like a normal derivation to the user.
-
-These bootstrap sources are later on defined *again*, once `curl`is available,
-to be downloaded using the standard pkgs.fetchtarball mechanism, but yielding
-the *same* outputs (as the same files are being fetched).
-
-In our reference scanning implementation, this output scanning of FOD will
-cause the path of the *first* derivation producing the given fixed output to be
-stored in the `inputDrvs` field of the derivation, while Nix will point to the
-derivation that was actually used.
-
-This doesn't cause any differences in the calculated *output paths*, as paths to
-fixed-output derivations are replaced with a special
-`fixed:out:${algo}:${digest}:${fodPath}` string that doesn't contain the "path
-to the wrong derivation" anymore.
-
-As we haven't fully determined if our reference scanning approach is gonna work,
-and comparing output paths is sufficient to determine equality of the build
-instructions, this is left as a future work item.
-
-
-[^inbox-drvpath]: https://inbox.tvl.su/depot/20230316120039.j4fkp3puzrtbjcpi@tp/T/#t