Diff of the two buildlogs:

--
--- b1/build.log	2025-07-19 06:25:03.130673747 +0000
+++ b2/build.log	2025-07-19 07:49:07.201491095 +0000
@@ -1,6 +1,6 @@
 I: pbuilder: network access will be disabled during build
-I: Current time: Thu Aug 20 23:30:34 -12 2026
-I: pbuilder-time-stamp: 1787311834
+I: Current time: Sat Jul 19 20:25:04 +14 2025
+I: pbuilder-time-stamp: 1752906304
 I: Building the build Environment
 I: extracting base tarball [/var/cache/pbuilder/unstable-reproducible-base.tgz]
 I: copying local configuration
@@ -29,52 +29,84 @@
 dpkg-source: info: applying skip_awkward.patch
 I: Not using root during the build.
 I: Installing the build-deps
-I: user script /srv/workspace/pbuilder/1788060/tmp/hooks/D02_print_environment starting
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/D01_modify_environment starting
+debug: Running on ionos1-amd64.
+I: Changing host+domainname to test build reproducibility
+I: Adding a custom variable just for the fun of it...
+I: Changing /bin/sh to bash
+'/bin/sh' -> '/bin/bash'
+lrwxrwxrwx 1 root root 9 Jul 19 06:25 /bin/sh -> /bin/bash
+I: Setting pbuilder2's login shell to /bin/bash
+I: Setting pbuilder2's GECOS to second user,second room,second work-phone,second home-phone,second other
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/D01_modify_environment finished
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/D02_print_environment starting
 I: set
-  BUILDDIR='/build/reproducible-path'
-  BUILDUSERGECOS='first user,first room,first work-phone,first home-phone,first other'
-  BUILDUSERNAME='pbuilder1'
-  BUILD_ARCH='amd64'
-  DEBIAN_FRONTEND='noninteractive'
-  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=42 '
-  DISTRIBUTION='unstable'
-  HOME='/root'
-  HOST_ARCH='amd64'
+  BASH=/bin/sh
+  BASHOPTS=checkwinsize:cmdhist:complete_fullquote:extquote:force_fignore:globasciiranges:globskipdots:hostcomplete:interactive_comments:patsub_replacement:progcomp:promptvars:sourcepath
+  BASH_ALIASES=()
+  BASH_ARGC=()
+  BASH_ARGV=()
+  BASH_CMDS=()
+  BASH_LINENO=([0]="12" [1]="0")
+  BASH_LOADABLES_PATH=/usr/local/lib/bash:/usr/lib/bash:/opt/local/lib/bash:/usr/pkg/lib/bash:/opt/pkg/lib/bash:.
+  BASH_SOURCE=([0]="/tmp/hooks/D02_print_environment" [1]="/tmp/hooks/D02_print_environment")
+  BASH_VERSINFO=([0]="5" [1]="2" [2]="37" [3]="1" [4]="release" [5]="x86_64-pc-linux-gnu")
+  BASH_VERSION='5.2.37(1)-release'
+  BUILDDIR=/build/reproducible-path
+  BUILDUSERGECOS='second user,second room,second work-phone,second home-phone,second other'
+  BUILDUSERNAME=pbuilder2
+  BUILD_ARCH=amd64
+  DEBIAN_FRONTEND=noninteractive
+  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=40 '
+  DIRSTACK=()
+  DISTRIBUTION=unstable
+  EUID=0
+  FUNCNAME=([0]="Echo" [1]="main")
+  GROUPS=()
+  HOME=/root
+  HOSTNAME=i-capture-the-hostname
+  HOSTTYPE=x86_64
+  HOST_ARCH=amd64
   IFS=' 	
   '
-  INVOCATION_ID='881d8a5c613a400e8a5776682c94192b'
-  LANG='C'
-  LANGUAGE='en_US:en'
-  LC_ALL='C'
-  MAIL='/var/mail/root'
-  OPTIND='1'
-  PATH='/usr/sbin:/usr/bin:/sbin:/bin:/usr/games'
-  PBCURRENTCOMMANDLINEOPERATION='build'
-  PBUILDER_OPERATION='build'
-  PBUILDER_PKGDATADIR='/usr/share/pbuilder'
-  PBUILDER_PKGLIBDIR='/usr/lib/pbuilder'
-  PBUILDER_SYSCONFDIR='/etc'
-  PPID='1788060'
-  PS1='# '
-  PS2='> '
+  INVOCATION_ID=b9888dbc4dce4c7ca5c7fc3945c87516
+  LANG=C
+  LANGUAGE=et_EE:et
+  LC_ALL=C
+  MACHTYPE=x86_64-pc-linux-gnu
+  MAIL=/var/mail/root
+  OPTERR=1
+  OPTIND=1
+  OSTYPE=linux-gnu
+  PATH=/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path
+  PBCURRENTCOMMANDLINEOPERATION=build
+  PBUILDER_OPERATION=build
+  PBUILDER_PKGDATADIR=/usr/share/pbuilder
+  PBUILDER_PKGLIBDIR=/usr/lib/pbuilder
+  PBUILDER_SYSCONFDIR=/etc
+  PIPESTATUS=([0]="0")
+  POSIXLY_CORRECT=y
+  PPID=1379010
   PS4='+ '
-  PWD='/'
-  SHELL='/bin/bash'
-  SHLVL='2'
-  SUDO_COMMAND='/usr/bin/timeout -k 18.1h 18h /usr/bin/ionice -c 3 /usr/bin/nice /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.GD9NG0MN/pbuilderrc_lndo --distribution unstable --hookdir /etc/pbuilder/first-build-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.GD9NG0MN/b1 --logfile b1/build.log python-anndata_0.12.0~rc1-1.dsc'
-  SUDO_GID='111'
-  SUDO_UID='106'
-  SUDO_USER='jenkins'
-  TERM='unknown'
-  TZ='/usr/share/zoneinfo/Etc/GMT+12'
-  USER='root'
-  _='/usr/bin/systemd-run'
-  http_proxy='http://213.165.73.152:3128'
+  PWD=/
+  SHELL=/bin/bash
+  SHELLOPTS=braceexpand:errexit:hashall:interactive-comments:posix
+  SHLVL=3
+  SUDO_COMMAND='/usr/bin/timeout -k 24.1h 24h /usr/bin/ionice -c 3 /usr/bin/nice -n 11 /usr/bin/unshare --uts -- /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.GD9NG0MN/pbuilderrc_CflV --distribution unstable --hookdir /etc/pbuilder/rebuild-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/unstable-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.GD9NG0MN/b2 --logfile b2/build.log python-anndata_0.12.0~rc1-1.dsc'
+  SUDO_GID=110
+  SUDO_UID=105
+  SUDO_USER=jenkins
+  TERM=unknown
+  TZ=/usr/share/zoneinfo/Etc/GMT-14
+  UID=0
+  USER=root
+  _='I: set'
+  http_proxy=http://46.16.76.132:3128
 I: uname -a
-  Linux ionos15-amd64 6.12.32+bpo-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.12.32-1~bpo12+1 (2025-06-21) x86_64 GNU/Linux
+  Linux i-capture-the-hostname 6.1.0-37-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.140-1 (2025-05-22) x86_64 GNU/Linux
 I: ls -l /bin
-  lrwxrwxrwx 1 root root 7 May 12  2025 /bin -> usr/bin
-I: user script /srv/workspace/pbuilder/1788060/tmp/hooks/D02_print_environment finished
+  lrwxrwxrwx 1 root root 7 May 12 19:25 /bin -> usr/bin
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/D02_print_environment finished
  -> Attempting to satisfy build-dependencies
  -> Creating pbuilder-satisfydepends-dummy package
 Package: pbuilder-satisfydepends-dummy
@@ -387,7 +419,7 @@
 Get: 217 http://deb.debian.org/debian unstable/main amd64 python3-xarray all 2025.03.1-8 [820 kB]
 Get: 218 http://deb.debian.org/debian unstable/main amd64 python3-xlrd all 2.0.1-2 [88.9 kB]
 Get: 219 http://deb.debian.org/debian unstable/main amd64 python3-zarr all 3.0.6-2 [1990 kB]
-Fetched 151 MB in 2s (99.9 MB/s)
+Fetched 151 MB in 10s (14.9 MB/s)
 Preconfiguring packages ...
 Selecting previously unselected package libexpat1:amd64.
 (Reading database ... 
(Reading database ... 5%
(Reading database ... 10%
(Reading database ... 15%
(Reading database ... 20%
(Reading database ... 25%
(Reading database ... 30%
(Reading database ... 35%
(Reading database ... 40%
(Reading database ... 45%
(Reading database ... 50%
(Reading database ... 55%
(Reading database ... 60%
(Reading database ... 65%
(Reading database ... 70%
(Reading database ... 75%
(Reading database ... 80%
(Reading database ... 85%
(Reading database ... 90%
(Reading database ... 95%
(Reading database ... 100%
(Reading database ... 19849 files and directories currently installed.)
@@ -1087,8 +1119,8 @@
 Setting up tzdata (2025b-4) ...
 
 Current default time zone: 'Etc/UTC'
-Local time is now:      Fri Aug 21 11:31:24 UTC 2026.
-Universal Time is now:  Fri Aug 21 11:31:24 UTC 2026.
+Local time is now:      Sat Jul 19 06:26:49 UTC 2025.
+Universal Time is now:  Sat Jul 19 06:26:49 UTC 2025.
 Run 'dpkg-reconfigure tzdata' if you wish to change it.
 
 Setting up autotools-dev (20240727.1) ...
@@ -1303,7 +1335,11 @@
 Building tag database...
  -> Finished parsing the build-deps
 I: Building the package
-I: Running cd /build/reproducible-path/python-anndata-0.12.0~rc1/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-genchanges -S  > ../python-anndata_0.12.0~rc1-1_source.changes
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/A99_set_merged_usr starting
+Not re-configuring usrmerge for unstable
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/A99_set_merged_usr finished
+hostname: Name or service not known
+I: Running cd /build/reproducible-path/python-anndata-0.12.0~rc1/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-genchanges -S  > ../python-anndata_0.12.0~rc1-1_source.changes
 dpkg-buildpackage: info: source package python-anndata
 dpkg-buildpackage: info: source version 0.12.0~rc1-1
 dpkg-buildpackage: info: source distribution unstable
@@ -1333,7 +1369,7 @@
 cachedir: .pytest_cache
 rootdir: /build/reproducible-path/python-anndata-0.12.0~rc1/.pybuild/cpython3_3.13_anndata/build
 configfile: pyproject.toml
-plugins: cov-5.0.0, anyio-4.8.0, typeguard-4.4.2, xdist-3.6.1, mock-3.14.0
+plugins: mock-3.14.0, xdist-3.6.1, typeguard-4.4.2, cov-5.0.0, anyio-4.8.0
 collecting ... collected 6026 items / 3 skipped
 
 tests/lazy/test_concat.py::test_concat_access_count[full-vars_different-obs-cat-outer] PASSED [  0%]
@@ -4240,8 +4276,8 @@
 tests/test_inplace_subset.py::test_inplace_subset_no_X[spmatrix_bool_subset-var] PASSED [ 48%]
 tests/test_inplace_subset.py::test_inplace_subset_no_X[sparray_bool_subset-obs] PASSED [ 48%]
 tests/test_inplace_subset.py::test_inplace_subset_no_X[sparray_bool_subset-var] PASSED [ 48%]
-tests/test_io_backwards_compat.py::test_backwards_compat_files[v0.7.8] PASSED [ 48%]
 tests/test_io_backwards_compat.py::test_backwards_compat_files[v0.7.0] PASSED [ 48%]
+tests/test_io_backwards_compat.py::test_backwards_compat_files[v0.7.8] PASSED [ 48%]
 tests/test_io_backwards_compat.py::test_clean_uns_backwards_compat[h5ad] PASSED [ 48%]
 tests/test_io_backwards_compat.py::test_clean_uns_backwards_compat[zarr2] PASSED [ 48%]
 tests/test_io_backwards_compat.py::test_clean_uns_backwards_compat[zarr3] PASSED [ 48%]
@@ -7368,7 +7404,7 @@
   /usr/lib/python3/dist-packages/setuptools_scm/_get_version_impl.py:173: DeprecationWarning: empty regex for tag regex is invalid, using default
     warnings.warn(EMPTY_TAG_REGEX_DEPRECATION)
 
-tests/lazy/test_concat.py: 1116 warnings
+tests/lazy/test_concat.py: 1150 warnings
 tests/test_concatenate.py: 442 warnings
 tests/test_concatenate_disk.py: 104 warnings
 tests/test_utils.py: 1 warning
@@ -7381,14 +7417,14 @@
   /build/reproducible-path/python-anndata-0.12.0~rc1/.pybuild/cpython3_3.13_anndata/build/tests/test_backed_dense.py:84: ImplicitModificationWarning: Modifying `X` on a view results in data being overridden
     view.X = np.zeros((4, 2))
 
-tests/test_backed_sparse.py: 1413 warnings
-tests/test_dask.py: 111 warnings
-tests/test_io_backwards_compat.py: 9 warnings
-tests/test_io_elementwise.py: 232 warnings
-tests/test_io_partial.py: 8 warnings
+tests/test_backed_sparse.py: 1415 warnings
+tests/test_dask.py: 110 warnings
+tests/test_io_backwards_compat.py: 8 warnings
+tests/test_io_elementwise.py: 227 warnings
+tests/test_io_partial.py: 7 warnings
 tests/test_io_utils.py: 1 warning
-tests/test_readwrite.py: 417 warnings
-tests/test_x.py: 37 warnings
+tests/test_readwrite.py: 409 warnings
+tests/test_x.py: 36 warnings
   /usr/lib/python3/dist-packages/zarr/codecs/vlen_utf8.py:44: UserWarning: The codec `vlen-utf8` is currently not part in the Zarr format 3 specification. It may not be supported by other zarr implementations and may change in the future.
     return cls(**configuration_parsed)
 
@@ -7446,7 +7482,6 @@
     self._set_arrayXarray(i, j, x)
 
 tests/test_concatenate.py: 8 warnings
-tests/test_helpers.py: 1 warning
 tests/test_views.py: 6 warnings
   /usr/lib/python3/dist-packages/scipy/sparse/_index.py:168: SparseEfficiencyWarning: Changing the sparsity structure of a csr_matrix is expensive. lil and dok are more efficient.
     self._set_intXint(row, col, x.flat[0])
@@ -7534,7 +7569,7 @@
     self._set_arrayXarray_sparse(i, j, x)
 
 -- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
-== 5252 passed, 634 skipped, 143 xfailed, 5488 warnings in 4473.48s (1:14:33) ==
+== 5252 passed, 634 skipped, 143 xfailed, 5506 warnings in 4800.66s (1:20:00) ==
    debian/rules execute_after_dh_auto_test
 make[1]: Entering directory '/build/reproducible-path/python-anndata-0.12.0~rc1'
 rm -fv  /build/reproducible-path/python-anndata-0.12.0~rc1/.pybuild/cpython3_*_anndata/build/test.h5ad
@@ -7568,12 +7603,14 @@
 dpkg-buildpackage: info: binary-only upload (no source included)
 dpkg-genchanges: info: including full source code in upload
 I: copying local configuration
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/B01_cleanup starting
+I: user script /srv/workspace/pbuilder/1379010/tmp/hooks/B01_cleanup finished
 I: unmounting dev/ptmx filesystem
 I: unmounting dev/pts filesystem
 I: unmounting dev/shm filesystem
 I: unmounting proc filesystem
 I: unmounting sys filesystem
 I: cleaning the build env 
-I: removing directory /srv/workspace/pbuilder/1788060 and its subdirectories
-I: Current time: Fri Aug 21 00:48:02 -12 2026
-I: pbuilder-time-stamp: 1787316482
+I: removing directory /srv/workspace/pbuilder/1379010 and its subdirectories
+I: Current time: Sat Jul 19 21:49:06 +14 2025
+I: pbuilder-time-stamp: 1752911346