Hi, I checked I have rigorously the same outputs as you. I reproduced it below for completeness (I changed a bit the type command you gave because I use zsh and type -P does not exist in zsh).
TLDR I managed to build python-jax using the /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix profile, which as you indicate means that time machine is not using the right profile, and I found that this is due to GUILE_LOAD_COMPILED_PATH environment variable. My first step was to see if the clean bash login was necessary, and it is! The outputs go like this: --8<---------------cut here---------------start------------->8--- $ /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix build python-jax guix-science/build-system/bazel.scm:104:45: In procedure bazel-vendored-inputs: erreur : nss-certs : variable non liée conseil : Auriez-vous oublié `(use-modules (gnu packages certs))' ? $ env -i $(bash -c "type -P bash") --login --noprofile --norc bash-5.2$ /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix build python-jax /gnu/store/slfhr5slgshs1c1g99rs09qggmkrmbjz-python-jax-0.4.28 --8<---------------cut here---------------end--------------->8--- I digged into it a bit more and turns out, it is due to GUILE_LOAD_COMPILED_PATH environment variable --8<---------------cut here---------------start------------->8--- $ GUILE_LOAD_COMPILED_PATH="" /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix build python-jax /gnu/store/slfhr5slgshs1c1g99rs09qggmkrmbjz-python-jax-0.4.28 $ GUILE_LOAD_COMPILED_PATH="" guix time-machine -C channels.scm -- build python-jax /gnu/store/slfhr5slgshs1c1g99rs09qggmkrmbjz-python-jax-0.4.28 --8<---------------cut here---------------end--------------->8--- I have no idea what this environment variable does, it is automatically set when I activate my profiles, but anyway it should not impact the inferior am I right? FYI, here is the content of GUILE_LOAD_COMPILED_PATH (I use several guix profiles) --8<---------------cut here---------------start------------->8--- $ echo $GUILE_LOAD_COMPILED_PATH /home/tmathieu/.guix-extra-profiles/extra_profile/extra_profile/lib/guile/3.0/site-ccache:/home/tmathieu/.guix-extra-profiles/extra_profile/extra_profile/share/guile/site/3.0:/home/tmathieu/.config/guix/current/lib/guile/3.0/site-ccache --8<---------------cut here---------------end--------------->8--- Best, Timothée The outputs from commands of previous mail: --8<---------------cut here---------------start------------->8--- $ readlink -f $(guix time-machine -C channels.scm) /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile $ find $(readlink -f $(guix time-machine -C channels.scm)/lib/guile/3.0/site-ccache/gnu) -type f | grep certs /gnu/store/g4yscymdp3k9ihlasaa6128wngs47w6q-guix-52d82e555-modules/lib/guile/3.0/site-ccache/gnu/packages/certs.go $ find $(readlink -f $(guix time-machine -C channels.scm)/lib/guile/3.0/site-ccache/guix-science) -type f | grep -E '(bazel|jupyther|python)' /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/packages/python.go /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/packages/bazel.go /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/build/bazel-build-system.go /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/build-system/bazel.go $ guix hash -f hex -H sha1 $(guix time-machine -C channels.scm)/manifest b1b4fc1f9ec79f39a133f60c8e2018e2bc003bc5 $ guix hash -f hex -H sha1 /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/manifest b1b4fc1f9ec79f39a133f60c8e2018e2bc003bc5 $ cat $(guix time-machine -C channels.scm)/manifest ;; This file was automatically generated and is for internal use only. ;; It cannot be passed to the '--manifest' option. ;; Run 'guix package --export-manifest' if you want to export a file ;; suitable for '--manifest'. (manifest (version 3) (packages (("guix-science" "1fff462" "out" "/gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science" (propagated-inputs ()) (search-paths ()) (properties (source (repository (version 0) (url "https://codeberg.org/guix-science/guix-science.git") (branch "master") (commit "1fff4622cf7b51c40c549f83496dc6d906bf874f") (name guix-science) (introduction (channel-introduction (version 0) (commit "b1fe5aaff3ab48e798a4cce02f0212bc91f423dc") (signer "CA4F 8CF4 37D7 478F DA05 5FD4 4213 7701 1A37 8446"))))))) ("guix" "52d82e5" "out" "/gnu/store/nxg5z5g7fh1c5vcrzv6d53xnaxxxnz2v-guix-52d82e555" (propagated-inputs ()) (search-paths ()) (properties (source (repository (version 0) (url "https://git.guix.gnu.org/guix.git") (branch "master") (commit "52d82e555119c013cfbf9ad7671a56dc6c1a1f16") (name guix) (introduction (channel-introduction (version 0) (commit "9edb3f66fd807b096b48283debdcddccfea34bad") (signer "BBB0 2DDF 2CEA F6A8 0D1D E643 A2A0 6DF2 A33A 54FA")))))))))) $ readlink -f /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/share/guile/site/3.0/guix-science/build-system/bazel.scm /gnu/store/4ick02v0scz4565b02fwii656x1dcd4x-guix-science-1fff462/guix-science/build-system/bazel.scm $ readlink -f /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/build-system/bazel.go /gnu/store/30j7azqpy63m251nr887g748w18cki6r-guix-science/lib/guile/3.0/site-ccache/guix-science/build-system/bazel.go $ readlink -f /gnu/store/nxg5z5g7fh1c5vcrzv6d53xnaxxxnz2v-guix-52d82e555/share/guile/site/3.0/gnu/packages/certs.scm /gnu/store/g4yscymdp3k9ihlasaa6128wngs47w6q-guix-52d82e555-modules/share/guile/site/3.0/gnu/packages/certs.scm $ readlink -f /gnu/store/nxg5z5g7fh1c5vcrzv6d53xnaxxxnz2v-guix-52d82e555/lib/guile/3.0/site-ccache/gnu/packages/certs.go /gnu/store/g4yscymdp3k9ihlasaa6128wngs47w6q-guix-52d82e555-modules/lib/guile/3.0/site-ccache/gnu/packages/certs.go $ env -i $(bash -c "type -P bash") --login --noprofile --norc bash-5.2$ type -P guix /usr/local/bin/guix bash-5.2$ PATH= bash-5.2$ type -P guix bash-5.2$ /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix describe -f channels-sans-intro (list (channel (name 'guix-science) (url "https://codeberg.org/guix-science/guix-science.git") (branch "master") (commit "1fff4622cf7b51c40c549f83496dc6d906bf874f")) (channel (name 'guix) (url "https://git.guix.gnu.org/guix.git") (branch "master") (commit "52d82e555119c013cfbf9ad7671a56dc6c1a1f16"))) bash-5.2$ /gnu/store/nw6nys0kg8118kxc9ks19n4zq2zpc0d0-profile/bin/guix build python-jax /gnu/store/slfhr5slgshs1c1g99rs09qggmkrmbjz-python-jax-0.4.28 --8<---------------cut here---------------end--------------->8---