From 85bccd9a84d431824e0b038a66a580c274c5b8dd Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Mon, 22 Jun 2026 15:52:19 +0200
Subject: [PATCH 01/15] adapt to t8code v4 API

---
 examples/trixi_controller_baroclinic.c | 4 ++--
 examples/trixi_controller_t8code.c     | 4 ++--
 examples/trixi_controller_t8code.f90   | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/examples/trixi_controller_baroclinic.c b/examples/trixi_controller_baroclinic.c
index 22cdefe3..1e12fe5b 100644
--- a/examples/trixi_controller_baroclinic.c
+++ b/examples/trixi_controller_baroclinic.c
@@ -26,11 +26,11 @@ void source_terms_baroclinic(int nnodes, double * nodes, t8_forest_t forest,
     // Iterates through all local trees
     for (t8_locidx_t itree = 0, index = 0; itree < num_local_trees; ++itree) {
         // Get number of elements of this tree
-        t8_locidx_t num_elements_in_tree = t8_forest_get_tree_num_elements (forest, itree);
+        t8_locidx_t num_elements_in_tree = t8_forest_get_tree_num_leaf_elements (forest, itree);
         // Iterate through all the local elements
         for (t8_locidx_t ielement = 0; ielement < num_elements_in_tree; ++ielement) {
             // Get a pointer to the current element
-            const t8_element_t *element = t8_forest_get_element_in_tree (forest, itree, ielement);
+            const t8_element_t *element = t8_forest_get_leaf_element_in_tree (forest, itree, ielement);
             for (int k = 0; k < nnodes; ++k) {
                 for (int j = 0; j < nnodes; ++j) {
                     for (int i = 0; i < nnodes; ++i, ++index) {
diff --git a/examples/trixi_controller_t8code.c b/examples/trixi_controller_t8code.c
index cebaaf30..84d0c5d8 100644
--- a/examples/trixi_controller_t8code.c
+++ b/examples/trixi_controller_t8code.c
@@ -16,10 +16,10 @@ void t8_print_forest_information (t8_forest_t forest)
     T8_ASSERT (t8_forest_is_committed (forest));
 
     // Get the local number of elements.
-    local_num_elements = t8_forest_get_local_num_elements (forest);
+    local_num_elements = t8_forest_get_local_num_leaf_elements (forest);
 
     // Get the global number of elements.
-    global_num_elements = t8_forest_get_global_num_elements (forest);
+    global_num_elements = t8_forest_get_global_num_leaf_elements (forest);
 
     printf ("\n*** T8code ***  Local number of elements:\t%i\n", local_num_elements);
     printf ("*** T8code ***  Global number of elements:\t%li\n", global_num_elements);
diff --git a/examples/trixi_controller_t8code.f90 b/examples/trixi_controller_t8code.f90
index ed769030..54858244 100644
--- a/examples/trixi_controller_t8code.f90
+++ b/examples/trixi_controller_t8code.f90
@@ -12,7 +12,7 @@ subroutine t8_print_forest_information(forest)
     ! T8_ASSERT (t8_forest_is_committed (forest));
 
     ! Get the local number of elements.
-    local_num_elements = t8_forest_get_local_num_elements (forest)
+    local_num_elements = t8_forest_get_local_num_leaf_elements (forest)
 
     ! Get the global number of elements.
     global_num_elements = t8_forest_get_global_num_elements (forest)

From 51e4555b19fbd66b6558452b488fc618e111ac03 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 6 Aug 2026 11:52:30 +0200
Subject: [PATCH 02/15] update to Trixi.jl 0.17

---
 LibTrixi.jl/Project.toml      | 2 +-
 LibTrixi.jl/test/Project.toml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/LibTrixi.jl/Project.toml b/LibTrixi.jl/Project.toml
index af16b336..23ef6d1f 100644
--- a/LibTrixi.jl/Project.toml
+++ b/LibTrixi.jl/Project.toml
@@ -13,5 +13,5 @@ Trixi = "a7f1ee26-1774-49b1-8366-f1abc58fbfcb"
 MPI = "0.20.13"
 Pkg = "1.8"
 SciMLBase = "2.33.0, 3"
-Trixi = "0.16.10"
+Trixi = "0.17"
 julia = "1.8"
diff --git a/LibTrixi.jl/test/Project.toml b/LibTrixi.jl/test/Project.toml
index b6fae1cb..77147b9a 100644
--- a/LibTrixi.jl/test/Project.toml
+++ b/LibTrixi.jl/test/Project.toml
@@ -5,4 +5,4 @@ Trixi = "a7f1ee26-1774-49b1-8366-f1abc58fbfcb"
 
 [compat]
 OrdinaryDiffEqLowStorageRK = "1.2, 2, 3"
-Trixi = "0.16.10"
+Trixi = "0.17"

From 2f0496bdf78fe5b0c5ac019944c5dbb6fe32bae5 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 6 Aug 2026 11:53:22 +0200
Subject: [PATCH 03/15] use t8code July release

---
 .github/workflows/ci.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 26fe920c..bd89d4af 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,13 +38,13 @@ jobs:
           - '1.10'
           - '1.11'
         t8code_version:
-          - '3.0.1'
+          - '4.0.0'
         include:
           - os: ubuntu-latest
             test_type: coverage
             arch: x64
             julia_version: '1.11'
-            t8code_version: '3.0.1'
+            t8code_version: '4.0.0'
     env:
       # Necessary for HDF5 to play nice with Julia
       LD_PRELOAD: /lib/x86_64-linux-gnu/libcurl.so.4
@@ -93,7 +93,7 @@ jobs:
           T8CODE_RELEASE=${{ matrix.t8code_version }}
           mkdir t8code-local
           cd t8code-local
-          wget https://github.com/DLR-AMR/t8code/releases/download/v${T8CODE_RELEASE}/T8CODE-${T8CODE_RELEASE}-Source.tar.gz
+          wget https://github.com/DLR-AMR/t8code/releases/download/v${T8CODE_RELEASE}-26.07/T8CODE-${T8CODE_RELEASE}-Source.tar.gz
           tar xf T8CODE-${T8CODE_RELEASE}-Source.tar.gz
           mkdir build
           cd build

From 0d02674e921cc3cd1b5758854027f96bc24ddb48 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 6 Aug 2026 12:20:07 +0200
Subject: [PATCH 04/15] t8code should not install gtest

---
 .github/workflows/ci.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bd89d4af..4a7b2743 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -103,6 +103,8 @@ jobs:
               -DCMAKE_BUILD_TYPE=Release \
               -DCMAKE_INSTALL_PREFIX="$PWD/../prefix" \
               -DT8CODE_BUILD_TESTS=OFF \
+              -DBUILD_GMOCK=OFF \
+              -DINSTALL_GTEST=OFF \
               -DT8CODE_BUILD_TUTORIALS=OFF \
               -DT8CODE_BUILD_EXAMPLES=OFF \
               -DT8CODE_BUILD_BENCHMARKS=OFF \

From f07c8675159be2fa6e024291370d056572129528 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 6 Aug 2026 17:35:44 +0200
Subject: [PATCH 05/15] PRIVATE_HEADER issue in July release

---
 .github/workflows/ci.yml | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4a7b2743..1caa57a0 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -114,6 +114,9 @@ jobs:
           make -j 2
           make install
 
+          # temporary workaround
+          mv ../prefix/PRIVATE_HEADER/* ../prefix/include/
+
       - name: Configure (test_type == 'regular')
         if: ${{ matrix.test_type == 'regular' }}
         run: |

From 1d4ebbceb7575e001a7e45059bc737f7d7cc0032 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Fri, 11 Sep 2026 18:22:27 +0200
Subject: [PATCH 06/15] try OpenMPI_jll v4

---
 utils/libtrixi-init-julia | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/utils/libtrixi-init-julia b/utils/libtrixi-init-julia
index a7e0be6f..c783a573 100755
--- a/utils/libtrixi-init-julia
+++ b/utils/libtrixi-init-julia
@@ -273,6 +273,17 @@ using Pkg
 Pkg.add([\"Preferences\", \"UUIDs\", \"MPIPreferences\", \"T8code\", \
          \"P4est\", \"HDF5\", \"MPI\"])"
 [ $? -eq 0 ] || die "could not install dependencies"
+
+# Workaround for CI runners using OpenMPI version 4
+# See https://github.com/trixi-framework/libtrixi/issues/237#issuecomment-2792609780
+if [ "$CI" = "true" ]; then
+  JULIA_DEPOT_PATH="$julia_depot" JULIA_PKG_PRECOMPILE_AUTO=0 \
+      $julia_exec --project=. \
+      -e "
+  using Pkg
+  Pkg.add(name=\"OpenMPI_jll\", version=\"4\")"
+  [ $? -eq 0 ] || die "could not install dependencies"
+fi
 echo
 
 # Set system MPI library

From 82232903cd427bba7b4a6516989e3304dffd41af Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Fri, 11 Sep 2026 18:23:13 +0200
Subject: [PATCH 07/15] remove n_cells_max

---
 LibTrixi.jl/examples/libelixir_tree1d_advection_basic.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/LibTrixi.jl/examples/libelixir_tree1d_advection_basic.jl b/LibTrixi.jl/examples/libelixir_tree1d_advection_basic.jl
index d34bc223..17b020f3 100644
--- a/LibTrixi.jl/examples/libelixir_tree1d_advection_basic.jl
+++ b/LibTrixi.jl/examples/libelixir_tree1d_advection_basic.jl
@@ -20,7 +20,7 @@ function init_simstate()
     # Create a uniformly refined mesh with periodic boundaries
     mesh = TreeMesh(coordinates_min, coordinates_max,
                     initial_refinement_level = 4,
-                    n_cells_max = 30_000, periodicity = true)
+                    periodicity = true)
 
     # A semidiscretization collects data structures and functions for the spatial discretization
     semi = SemidiscretizationHyperbolic(mesh, equations,

From 8f9158cf0acec7b0bd3287c0921e3e92b04cf136 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Wed, 16 Sep 2026 10:10:11 +0200
Subject: [PATCH 08/15] try with T8code not loading t8code_jll

---
 utils/libtrixi-init-julia | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/utils/libtrixi-init-julia b/utils/libtrixi-init-julia
index c783a573..fdca7383 100755
--- a/utils/libtrixi-init-julia
+++ b/utils/libtrixi-init-julia
@@ -281,7 +281,7 @@ if [ "$CI" = "true" ]; then
       $julia_exec --project=. \
       -e "
   using Pkg
-  Pkg.add(name=\"OpenMPI_jll\", version=\"4\")"
+  Pkg.add(name=\"T8code\", rev=\"bg/avoid-loading-t8code_jll\")"
   [ $? -eq 0 ] || die "could not install dependencies"
 fi
 echo

From fcd9b42053bcf687e6fc9ad144c1d69ee9d31bc9 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Wed, 23 Sep 2026 11:01:40 +0200
Subject: [PATCH 09/15] now in T8code main

---
 utils/libtrixi-init-julia | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/utils/libtrixi-init-julia b/utils/libtrixi-init-julia
index fdca7383..9c4c4ce2 100755
--- a/utils/libtrixi-init-julia
+++ b/utils/libtrixi-init-julia
@@ -274,18 +274,6 @@ Pkg.add([\"Preferences\", \"UUIDs\", \"MPIPreferences\", \"T8code\", \
          \"P4est\", \"HDF5\", \"MPI\"])"
 [ $? -eq 0 ] || die "could not install dependencies"
 
-# Workaround for CI runners using OpenMPI version 4
-# See https://github.com/trixi-framework/libtrixi/issues/237#issuecomment-2792609780
-if [ "$CI" = "true" ]; then
-  JULIA_DEPOT_PATH="$julia_depot" JULIA_PKG_PRECOMPILE_AUTO=0 \
-      $julia_exec --project=. \
-      -e "
-  using Pkg
-  Pkg.add(name=\"T8code\", rev=\"bg/avoid-loading-t8code_jll\")"
-  [ $? -eq 0 ] || die "could not install dependencies"
-fi
-echo
-
 # Set system MPI library
 echo "Use system MPI for Julia... "
 JULIA_DEPOT_PATH="$julia_depot" $julia_exec --project=. \

From 409579248280020f1d7f4bdceb7e0183fe13a305 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 14:58:22 +0200
Subject: [PATCH 10/15] use full version string

---
 .github/workflows/ci.yml | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1caa57a0..bc0844d1 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,13 +38,13 @@ jobs:
           - '1.10'
           - '1.11'
         t8code_version:
-          - '4.0.0'
+          - '4.0.0-26-07'
         include:
           - os: ubuntu-latest
             test_type: coverage
             arch: x64
             julia_version: '1.11'
-            t8code_version: '4.0.0'
+            t8code_version: '4.0.0-26.07'
     env:
       # Necessary for HDF5 to play nice with Julia
       LD_PRELOAD: /lib/x86_64-linux-gnu/libcurl.so.4
@@ -90,11 +90,12 @@ jobs:
       - name: Install t8code
         if: steps.cache-t8code.outputs.cache-hit != 'true'
         run: |
-          T8CODE_RELEASE=${{ matrix.t8code_version }}
+          T8CODE_FULL_VERSION=${{ matrix.t8code_version }}
+          T8CODE_VERSION=${T8CODE_FULL_VERSION%%-*}
           mkdir t8code-local
           cd t8code-local
-          wget https://github.com/DLR-AMR/t8code/releases/download/v${T8CODE_RELEASE}-26.07/T8CODE-${T8CODE_RELEASE}-Source.tar.gz
-          tar xf T8CODE-${T8CODE_RELEASE}-Source.tar.gz
+          wget https://github.com/DLR-AMR/t8code/releases/download/v${T8CODE_FULL_VERSION}/T8CODE-${T8CODE_VERSION}-Source.tar.gz
+          tar xf T8CODE-${T8CODE_VERSION}-Source.tar.gz
           mkdir build
           cd build
           cmake \
@@ -110,7 +111,7 @@ jobs:
               -DT8CODE_BUILD_BENCHMARKS=OFF \
               -DT8CODE_ENABLE_MPI=ON \
               -DT8CODE_BUILD_FORTRAN_INTERFACE=ON \
-              ../T8CODE-${T8CODE_RELEASE}-Source
+              ../T8CODE-${T8CODE_VERSION}-Source
           make -j 2
           make install
 

From e08e17a8d108d9d769cb3a7241fb190e658851a7 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 15:00:27 +0200
Subject: [PATCH 11/15] lnk gh issue for workaround

---
 .github/workflows/ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bc0844d1..6875692f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -115,7 +115,8 @@ jobs:
           make -j 2
           make install
 
-          # temporary workaround
+          # temporary workaround, remove with next release
+          # https://github.com/DLR-AMR/t8code/pull/2355
           mv ../prefix/PRIVATE_HEADER/* ../prefix/include/
 
       - name: Configure (test_type == 'regular')

From 1b0e5ea10912c12b3d5880a055c4c47ce6cdb135 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 15:02:39 +0200
Subject: [PATCH 12/15] PackageCompiler hotfix

current version errors
---
 LibTrixi.jl/lib/Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/LibTrixi.jl/lib/Project.toml b/LibTrixi.jl/lib/Project.toml
index 60481033..73c2958d 100644
--- a/LibTrixi.jl/lib/Project.toml
+++ b/LibTrixi.jl/lib/Project.toml
@@ -3,5 +3,5 @@ PackageCompiler = "9b87118b-4619-50d2-8e1e-99f35a4d4d9d"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 
 [compat]
-PackageCompiler = "2.1.9"
+PackageCompiler = "2.1.9, < 2.4.2"
 TOML = "1"

From d4056f4bd25d070bb2d165369c1b2067b864518b Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 15:05:06 +0200
Subject: [PATCH 13/15] re-add line

---
 utils/libtrixi-init-julia | 1 +
 1 file changed, 1 insertion(+)

diff --git a/utils/libtrixi-init-julia b/utils/libtrixi-init-julia
index 9c4c4ce2..a7e0be6f 100755
--- a/utils/libtrixi-init-julia
+++ b/utils/libtrixi-init-julia
@@ -273,6 +273,7 @@ using Pkg
 Pkg.add([\"Preferences\", \"UUIDs\", \"MPIPreferences\", \"T8code\", \
          \"P4est\", \"HDF5\", \"MPI\"])"
 [ $? -eq 0 ] || die "could not install dependencies"
+echo
 
 # Set system MPI library
 echo "Use system MPI for Julia... "

From 7305e716d839ac3785d02e4f4e3102331b6a3529 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 15:24:41 +0200
Subject: [PATCH 14/15] duh

---
 .github/workflows/ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6875692f..df6d3876 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,7 +38,7 @@ jobs:
           - '1.10'
           - '1.11'
         t8code_version:
-          - '4.0.0-26-07'
+          - '4.0.0-26.07'
         include:
           - os: ubuntu-latest
             test_type: coverage

From 416470dd25e921009c3d102042ebf8d4308b25d7 Mon Sep 17 00:00:00 2001
From: Benedict Geihe <bgeihe@uni-koeln.de>
Date: Thu, 24 Sep 2026 16:06:20 +0200
Subject: [PATCH 15/15] compat bound syntax

---
 LibTrixi.jl/lib/Project.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/LibTrixi.jl/lib/Project.toml b/LibTrixi.jl/lib/Project.toml
index 73c2958d..2019109f 100644
--- a/LibTrixi.jl/lib/Project.toml
+++ b/LibTrixi.jl/lib/Project.toml
@@ -3,5 +3,5 @@ PackageCompiler = "9b87118b-4619-50d2-8e1e-99f35a4d4d9d"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 
 [compat]
-PackageCompiler = "2.1.9, < 2.4.2"
+PackageCompiler = "2.1.9 - 2.4.1"
 TOML = "1"