diff --git a/.github/workflows/nix-action-8.18.yml b/.github/workflows/nix-action-8.18.yml
index 7857c76..1a7beee 100644
--- a/.github/workflows/nix-action-8.18.yml
+++ b/.github/workflows/nix-action-8.18.yml
@@ -8,7 +8,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -22,16 +22,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -55,7 +55,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -69,16 +69,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -134,7 +134,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -148,16 +148,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -202,7 +202,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -216,16 +216,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -277,5 +277,4 @@ name: Nix CI for bundle 8.18
     - reopened
   push:
     branches:
-    - main
-  workflow_dispatch:
+    - master
diff --git a/.github/workflows/nix-action-8.19.yml b/.github/workflows/nix-action-8.19.yml
index 36cebd7..6949247 100644
--- a/.github/workflows/nix-action-8.19.yml
+++ b/.github/workflows/nix-action-8.19.yml
@@ -8,7 +8,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -22,16 +22,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -55,7 +55,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -69,16 +69,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -134,7 +134,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -148,16 +148,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -202,7 +202,7 @@ jobs:
         \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
         \ }}\" >> $GITHUB_ENV\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.target_commit }}
@@ -216,16 +216,16 @@ jobs:
         \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
         \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
     - name: Git checkout
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
       with:
         fetch-depth: 0
         ref: ${{ env.tested_commit }}
     - name: Cachix install
-      uses: cachix/install-nix-action@v20
+      uses: cachix/install-nix-action@v27
       with:
         nix_path: nixpkgs=channel:nixpkgs-unstable
     - name: Cachix setup coq
-      uses: cachix/cachix-action@v12
+      uses: cachix/cachix-action@v15
       with:
         extraPullNames: coq-community, math-comp
         name: coq
@@ -277,5 +277,4 @@ name: Nix CI for bundle 8.19
     - reopened
   push:
     branches:
-    - main
-  workflow_dispatch:
+    - master
diff --git a/.github/workflows/nix-action-8.20.yml b/.github/workflows/nix-action-8.20.yml
new file mode 100644
index 0000000..9f3eacb
--- /dev/null
+++ b/.github/workflows/nix-action-8.20.yml
@@ -0,0 +1,280 @@
+jobs:
+  coq:
+    needs: []
+    runs-on: ubuntu-latest
+    steps:
+    - name: Determine which commit to initially checkout
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"target_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
+        \ }}\" >> $GITHUB_ENV\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.target_commit }}
+    - name: Determine which commit to test
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"tested_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  merge_commit=$(git ls-remote ${{\
+        \ github.event.repository.html_url }} refs/pull/${{ github.event.number }}/merge\
+        \ | cut -f1)\n  mergeable=$(git merge --no-commit --no-ff ${{ github.event.pull_request.base.sha\
+        \ }} > /dev/null 2>&1; echo $?; git merge --abort > /dev/null 2>&1 || true)\n\
+        \  if [ -z \"$merge_commit\" -o \"x$mergeable\" != \"x0\" ]; then\n    echo\
+        \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
+        \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.tested_commit }}
+    - name: Cachix install
+      uses: cachix/install-nix-action@v27
+      with:
+        nix_path: nixpkgs=channel:nixpkgs-unstable
+    - name: Cachix setup coq
+      uses: cachix/cachix-action@v15
+      with:
+        extraPullNames: coq-community, math-comp
+        name: coq
+    - id: stepCheck
+      name: Checking presence of CI target coq
+      run: "nb_dry_run=$(NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link \\\n   --argstr\
+        \ bundle \"8.20\" --argstr job \"coq\" \\\n   --dry-run 2>&1 > /dev/null)\n\
+        echo $nb_dry_run\necho status=$(echo $nb_dry_run | grep \"built:\" | sed \"\
+        s/.*/built/\") >> $GITHUB_OUTPUT\n"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: Building/fetching current CI target
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "coq"
+  mathcomp:
+    needs:
+    - coq
+    runs-on: ubuntu-latest
+    steps:
+    - name: Determine which commit to initially checkout
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"target_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
+        \ }}\" >> $GITHUB_ENV\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.target_commit }}
+    - name: Determine which commit to test
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"tested_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  merge_commit=$(git ls-remote ${{\
+        \ github.event.repository.html_url }} refs/pull/${{ github.event.number }}/merge\
+        \ | cut -f1)\n  mergeable=$(git merge --no-commit --no-ff ${{ github.event.pull_request.base.sha\
+        \ }} > /dev/null 2>&1; echo $?; git merge --abort > /dev/null 2>&1 || true)\n\
+        \  if [ -z \"$merge_commit\" -o \"x$mergeable\" != \"x0\" ]; then\n    echo\
+        \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
+        \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.tested_commit }}
+    - name: Cachix install
+      uses: cachix/install-nix-action@v27
+      with:
+        nix_path: nixpkgs=channel:nixpkgs-unstable
+    - name: Cachix setup coq
+      uses: cachix/cachix-action@v15
+      with:
+        extraPullNames: coq-community, math-comp
+        name: coq
+    - id: stepCheck
+      name: Checking presence of CI target mathcomp
+      run: "nb_dry_run=$(NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link \\\n   --argstr\
+        \ bundle \"8.20\" --argstr job \"mathcomp\" \\\n   --dry-run 2>&1 > /dev/null)\n\
+        echo $nb_dry_run\necho status=$(echo $nb_dry_run | grep \"built:\" | sed \"\
+        s/.*/built/\") >> $GITHUB_OUTPUT\n"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: coq'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "coq"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-ssreflect'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-ssreflect"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-fingroup'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-fingroup"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-algebra'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-algebra"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-solvable'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-solvable"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-field'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-field"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-character'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-character"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: hierarchy-builder'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "hierarchy-builder"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: Building/fetching current CI target
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp"
+  mathcomp-analysis:
+    needs:
+    - coq
+    runs-on: ubuntu-latest
+    steps:
+    - name: Determine which commit to initially checkout
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"target_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
+        \ }}\" >> $GITHUB_ENV\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.target_commit }}
+    - name: Determine which commit to test
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"tested_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  merge_commit=$(git ls-remote ${{\
+        \ github.event.repository.html_url }} refs/pull/${{ github.event.number }}/merge\
+        \ | cut -f1)\n  mergeable=$(git merge --no-commit --no-ff ${{ github.event.pull_request.base.sha\
+        \ }} > /dev/null 2>&1; echo $?; git merge --abort > /dev/null 2>&1 || true)\n\
+        \  if [ -z \"$merge_commit\" -o \"x$mergeable\" != \"x0\" ]; then\n    echo\
+        \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
+        \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.tested_commit }}
+    - name: Cachix install
+      uses: cachix/install-nix-action@v27
+      with:
+        nix_path: nixpkgs=channel:nixpkgs-unstable
+    - name: Cachix setup coq
+      uses: cachix/cachix-action@v15
+      with:
+        extraPullNames: coq-community, math-comp
+        name: coq
+    - id: stepCheck
+      name: Checking presence of CI target mathcomp-analysis
+      run: "nb_dry_run=$(NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link \\\n   --argstr\
+        \ bundle \"8.20\" --argstr job \"mathcomp-analysis\" \\\n   --dry-run 2>&1\
+        \ > /dev/null)\necho $nb_dry_run\necho status=$(echo $nb_dry_run | grep \"\
+        built:\" | sed \"s/.*/built/\") >> $GITHUB_OUTPUT\n"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: coq'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "coq"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-classical'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-classical"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-field'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-field"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-bigenough'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-bigenough"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: hierarchy-builder'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "hierarchy-builder"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: Building/fetching current CI target
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-analysis"
+  ssprove:
+    needs:
+    - coq
+    - mathcomp-analysis
+    runs-on: ubuntu-latest
+    steps:
+    - name: Determine which commit to initially checkout
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"target_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  echo \"target_commit=${{ github.event.pull_request.head.sha\
+        \ }}\" >> $GITHUB_ENV\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.target_commit }}
+    - name: Determine which commit to test
+      run: "if [ ${{ github.event_name }} = \"push\" ]; then\n  echo \"tested_commit=${{\
+        \ github.sha }}\" >> $GITHUB_ENV\nelse\n  merge_commit=$(git ls-remote ${{\
+        \ github.event.repository.html_url }} refs/pull/${{ github.event.number }}/merge\
+        \ | cut -f1)\n  mergeable=$(git merge --no-commit --no-ff ${{ github.event.pull_request.base.sha\
+        \ }} > /dev/null 2>&1; echo $?; git merge --abort > /dev/null 2>&1 || true)\n\
+        \  if [ -z \"$merge_commit\" -o \"x$mergeable\" != \"x0\" ]; then\n    echo\
+        \ \"tested_commit=${{ github.event.pull_request.head.sha }}\" >> $GITHUB_ENV\n\
+        \  else\n    echo \"tested_commit=$merge_commit\" >> $GITHUB_ENV\n  fi\nfi\n"
+    - name: Git checkout
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+        ref: ${{ env.tested_commit }}
+    - name: Cachix install
+      uses: cachix/install-nix-action@v27
+      with:
+        nix_path: nixpkgs=channel:nixpkgs-unstable
+    - name: Cachix setup coq
+      uses: cachix/cachix-action@v15
+      with:
+        extraPullNames: coq-community, math-comp
+        name: coq
+    - id: stepCheck
+      name: Checking presence of CI target ssprove
+      run: "nb_dry_run=$(NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link \\\n   --argstr\
+        \ bundle \"8.20\" --argstr job \"ssprove\" \\\n   --dry-run 2>&1 > /dev/null)\n\
+        echo $nb_dry_run\necho status=$(echo $nb_dry_run | grep \"built:\" | sed \"\
+        s/.*/built/\") >> $GITHUB_OUTPUT\n"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: coq'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "coq"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: equations'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "equations"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-ssreflect'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-ssreflect"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: mathcomp-analysis'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "mathcomp-analysis"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: extructures'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "extructures"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: deriving'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "deriving"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: Building/fetching current CI target
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.20" --argstr
+        job "ssprove"
+name: Nix CI for bundle 8.20
+'on':
+  pull_request:
+    paths:
+    - .github/workflows/nix-action-8.20.yml
+  pull_request_target:
+    paths-ignore:
+    - .github/workflows/nix-action-8.20.yml
+    types:
+    - opened
+    - synchronize
+    - reopened
+  push:
+    branches:
+    - master
diff --git a/.nix/config.nix b/.nix/config.nix
index 195296d..0c77843 100644
--- a/.nix/config.nix
+++ b/.nix/config.nix
@@ -58,6 +58,11 @@
     mathcomp.override.version = "2.2.0";
     mathcomp-analysis.override.version = "1.0.0";
   };
+  bundles."8.20".coqPackages = {
+    coq.override.version = "8.19";
+    mathcomp.override.version = "2.2.0";
+    mathcomp-analysis.override.version = "1.2.0";
+  };
 
   ## Cachix caches to use in CI
   ## Below we list some standard ones
diff --git a/.nix/coq-nix-toolbox.nix b/.nix/coq-nix-toolbox.nix
index c339840..879ef3f 100644
--- a/.nix/coq-nix-toolbox.nix
+++ b/.nix/coq-nix-toolbox.nix
@@ -1 +1 @@
-"544d3d77a4a0f4fef30ad7825d2a8d2255abb0e3"
+"ebb1f62a5884802e598c662b22c978688a0e1a4a"