diff --git a/.gitea/workflows/acceptance.yml b/.gitea/workflows/acceptance.yml
index 8efd9761..c0e2a3e9 100644
--- a/.gitea/workflows/acceptance.yml
+++ b/.gitea/workflows/acceptance.yml
@@ -18,7 +18,8 @@ on:
   workflow_dispatch:
 
 concurrency:
-  group: qemu                     # one QEMU at a time on the runner: shared with nightly.yml and release.yml
+  group: qemu                     # every workflow shares this one group: one run at a time,
+                                  # a runner-image rebuild included (Captain Bob, 2026-11-07)
   cancel-in-progress: false
 
 jobs:
diff --git a/.gitea/workflows/build.yml b/.gitea/workflows/build.yml
index eee41929..07711d7f 100644
--- a/.gitea/workflows/build.yml
+++ b/.gitea/workflows/build.yml
@@ -13,6 +13,10 @@ on:
                                      # the server the wikis share (Captain Bob, 2026-11-07)
   workflow_dispatch:
 
+concurrency:
+  group: qemu                     # every workflow shares this one group (Captain Bob, 2026-11-07: a
+  cancel-in-progress: false       # runner-image rebuild blocks other jobs, always): one run at a time
+
 jobs:
   image:
     name: Image ${{ matrix.board }}
diff --git a/.gitea/workflows/nightly-docs.yml b/.gitea/workflows/nightly-docs.yml
index ef75f63f..d2410264 100644
--- a/.gitea/workflows/nightly-docs.yml
+++ b/.gitea/workflows/nightly-docs.yml
@@ -14,6 +14,10 @@ on:
     - cron: '0 4 * * *'        # 04:00 UTC, after the images (nightly.yml, 03:00)
   workflow_dispatch:
 
+concurrency:
+  group: qemu                     # every workflow shares this one group (Captain Bob, 2026-11-07: a
+  cancel-in-progress: false       # runner-image rebuild blocks other jobs, always): one run at a time
+
 jobs:
   docs:
     name: Book, volumes, API reference
diff --git a/.gitea/workflows/nightly.yml b/.gitea/workflows/nightly.yml
index 7f04f6f7..1588ff39 100644
--- a/.gitea/workflows/nightly.yml
+++ b/.gitea/workflows/nightly.yml
@@ -20,7 +20,8 @@ on:
   workflow_dispatch:
 
 concurrency:
-  group: qemu                     # one QEMU at a time on the runner: shared with acceptance.yml
+  group: qemu                     # every workflow shares this one group: one run at a time,
+                                  # a runner-image rebuild included (Captain Bob, 2026-11-07)
   cancel-in-progress: false
 
 jobs:
diff --git a/.gitea/workflows/release.yml b/.gitea/workflows/release.yml
index e248f06b..404bebd6 100644
--- a/.gitea/workflows/release.yml
+++ b/.gitea/workflows/release.yml
@@ -14,7 +14,8 @@ on:
     tags: ['v*']
 
 concurrency:
-  group: qemu                     # one QEMU at a time on the runner: shared with acceptance.yml
+  group: qemu                     # every workflow shares this one group: one run at a time,
+                                  # a runner-image rebuild included (Captain Bob, 2026-11-07)
   cancel-in-progress: false
 
 jobs:
diff --git a/.gitea/workflows/runner-image.yml b/.gitea/workflows/runner-image.yml
index 433997dd..485eaee2 100644
--- a/.gitea/workflows/runner-image.yml
+++ b/.gitea/workflows/runner-image.yml
@@ -17,6 +17,10 @@ on:
     paths: ['ci/runner-image/**', 'Makefile']
   workflow_dispatch:
 
+concurrency:
+  group: qemu                     # every workflow shares this one group (Captain Bob, 2026-11-07: a
+  cancel-in-progress: false       # runner-image rebuild blocks other jobs, always): one run at a time
+
 jobs:
   image:
     name: Build and publish the runner image