These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 3.53 s (backtrack: 9/20).

[ebuild     U  ] dev-python/installer-1.1.0::gentoo [0.7.0::gentoo] USE="-test -verify-provenance%" PYTHON_TARGETS="python3_14* -pypy3_12% -python3_12 -python3_13* -python3_14t (-python3_15) (-python3_15t) (-pypy3_11%) (-python3_11%) (-python3_13t%)" 924 KiB
[ebuild  NS    ] dev-lang/rust-bin-1.99.0:1.99.0::gentoo [1.94.0:1.94.0::gentoo] USE="clippy rustfmt (-big-endian) -doc* (-prefix) -rust-analyzer -rust-src -verify-sig" CPU_FLAGS_X86="sse2" LLVM_SLOT="(23%*) (-21%*)" 205530 KiB
[ebuild  N     ] dev-python/uv-0.13.1::gentoo  USE="-debug -test" 51868 KiB
[ebuild     U  ] dev-python/gpep517-23::gentoo [19::gentoo] USE="-test" PYTHON_TARGETS="python3_14* -pypy3_12% -python3_12 -python3_13* -python3_14t (-python3_15) (-python3_15t) (-pypy3_11%) (-python3_11%) (-python3_13t%)" 31 KiB
[ebuild     U  ] dev-python/flit-core-4.1.0::gentoo [3.12.0::gentoo] USE="-test -verify-provenance%" PYTHON_TARGETS="python3_14* -pypy3_12% -python3_12 -python3_13* -python3_14t (-python3_15) (-python3_15t) (-pypy3_11%) (-python3_11%) (-python3_13t%)" 54 KiB
[ebuild     U  ] dev-python/packaging-26.3::gentoo [26.0::gentoo] USE="-test -verify-provenance" PYTHON_TARGETS="python3_14* -pypy3_12% -python3_12 -python3_13* -python3_14t (-python3_15) (-python3_15t) (-pypy3_11%) (-python3_11%) (-python3_13t%)" 307 KiB
[ebuild     U  ] dev-python/idna-3.20::gentoo [3.11::gentoo] USE="-test% -verify-provenance%" PYTHON_TARGETS="python3_14* -python3_12 -python3_13* -python3_14t (-python3_15) (-python3_15t) (-pypy3_11%) (-python3_11%) (-python3_13t%)" 212 KiB
[ebuild  N     ] dev-python/uv-build-0.13.1::gentoo  USE="-test" PYTHON_TARGETS="python3_14 -python3_12 -python3_13 (-python3_15)" 437 KiB
[ebuild  N     ] dev-python/dnspython-2.9.0::gentoo  USE="-dnssec -examples -https -quic -test -verify-provenance" PYTHON_TARGETS="python3_14 -python3_12 -python3_13 (-python3_15)" 414 KiB

Total: 9 packages (5 upgrades, 3 new, 1 in new slot), Size of downloads: 259773 KiB

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

dev-python/packaging:0

  (dev-python/packaging-26.3:0/0::gentoo, ebuild scheduled for merge) USE="-test -verify-provenance" PYTHON_TARGETS="python3_14 -pypy3_12 -python3_12 -python3_13 -python3_14t (-python3_15) (-python3_15t)" pulled in by
    >=dev-python/packaging-26.1[python_targets_pypy3_12(-)?,python_targets_python3_12(-)?,python_targets_python3_13(-)?,python_targets_python3_14t(-)?,python_targets_python3_14(-)?,python_targets_python3_15t(-)?,python_targets_python3_15(-)?] required by (dev-python/gpep517-23:0/0::gentoo, ebuild scheduled for merge) USE="-test" PYTHON_TARGETS="python3_14 -pypy3_12 -python3_12 -python3_13 -python3_14t (-python3_15) (-python3_15t)"
    ^^                     ^^^^                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

  (dev-python/packaging-26.0:0/0::gentoo, installed) USE="-test -verify-provenance" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t" pulled in by
    >=dev-python/packaging-25.0[python_targets_python3_13(-)] required by (dev-python/setuptools-81.0.0:0/0::gentoo, installed) USE="-test" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t"
                                                                                                                                                                                                                                                                                                                                                                                                                        
    >=dev-python/packaging-23.2[python_targets_python3_13(-)] required by (dev-python/scikit-build-core-0.12.2:0/0::gentoo, installed) USE="-test -verify-provenance" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_14"
                                                                                                                                                                                                                                                                                                                                                                                                     
    dev-python/packaging[python_targets_python3_13(-)] required by (dev-python/setuptools-scm-9.2.2:0/0::gentoo, installed) USE="-test -verify-provenance" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t"
                                                                                                                                                                                                                                                                                                                                                                                                                                                          
    >=dev-python/packaging-24.2[python_targets_python3_13(-)] required by (dev-python/hatchling-1.29.0:0/0::gentoo, installed) USE="-test" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t"
                                                                                                                                                                                                                                                                                                                                                                                                                       
    >=dev-python/packaging-26.0[python_targets_python3_13(-)] required by (dev-python/wheel-0.46.3:0/0::gentoo, installed) USE="-test -verify-provenance" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t"
                                                                                                                                                                                                                                                                                                                                                                                                                                                         
    >=dev-python/packaging-23.2[python_targets_python3_12(-)?,python_targets_python3_13(-)?,python_targets_python3_14t(-)?,python_targets_python3_14(-)?,python_targets_python3_15t(-)?,python_targets_python3_15(-)?] required by (dev-python/pyproject-metadata-0.11.0:0/0::gentoo, installed) USE="-test -verify-provenance" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t"
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

dev-python/idna:0

  (dev-python/idna-3.20:0/0::gentoo, ebuild scheduled for merge) USE="-test -verify-provenance" PYTHON_TARGETS="python3_14 -python3_12 -python3_13 -python3_14t (-python3_15) (-python3_15t)" pulled in by
    >=dev-python/idna-2.1[python_targets_python3_12(-)?,python_targets_python3_13(-)?,python_targets_python3_14(-)?,python_targets_python3_15(-)?] required by (dev-python/dnspython-2.9.0:0/0::gentoo, ebuild scheduled for merge) USE="-dnssec -examples -https -quic -test -verify-provenance" PYTHON_TARGETS="python3_14 -python3_12 -python3_13 (-python3_15)"
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

  (dev-python/idna-3.11:0/0::gentoo, installed) USE="" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_13t -python3_14 -python3_14t" pulled in by
    <dev-python/idna-4[python_targets_python3_13(-)] required by (dev-python/requests-2.32.5-r1:0/0::gentoo, installed) USE="(test-rust) -socks5 -test" PYTHON_TARGETS="python3_13 -pypy3_11 -python3_11 -python3_12 -python3_14"
                                                                                                                                                                                                                                                                                                                                                                                                          


It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously.  If such a conflict exists in
the dependencies of two different packages, then those packages can
not be installed simultaneously. You may want to try a larger value of
the --backtrack option, such as --backtrack=30, in order to see if
that will solve this conflict automatically.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.