diff --git a/.cirrus.star b/.cirrus.star
index d2d6ceca207..2f03002833a 100644
--- a/.cirrus.star
+++ b/.cirrus.star
@@ -7,7 +7,7 @@ https://github.com/bazelbuild/starlark/blob/master/spec.md
 See also .cirrus.yml and src/tools/ci/README
 """
 
-load("cirrus", "env", "fs")
+load("cirrus", "env", "fs", "yaml")
 
 
 def main():
@@ -18,19 +18,36 @@ def main():
 
     1) the contents of .cirrus.yml
 
-    2) if defined, the contents of the file referenced by the, repository
+    2) computed environment variables
+
+    3) if defined, the contents of the file referenced by the, repository
        level, REPO_CI_CONFIG_GIT_URL variable (see
        https://cirrus-ci.org/guide/programming-tasks/#fs for the accepted
        format)
 
-    3) .cirrus.tasks.yml
+    4) .cirrus.tasks.yml
     """
 
     output = ""
 
     # 1) is evaluated implicitly
 
+
     # Add 2)
+    additional_env = compute_environment_vars()
+    env_fmt = """
+###
+# Computed environment variables start here
+###
+{0}
+###
+# Computed environment variables end here
+###
+"""
+    output += env_fmt.format(yaml.dumps({'env': additional_env}))
+
+
+    # Add 3)
     repo_config_url = env.get("REPO_CI_CONFIG_GIT_URL")
     if repo_config_url != None:
         print("loading additional configuration from \"{}\"".format(repo_config_url))
@@ -38,12 +55,37 @@ def main():
     else:
         output += "\n# REPO_CI_CONFIG_URL was not set\n"
 
-    # Add 3)
+
+    # Add 4)
     output += config_from(".cirrus.tasks.yml")
 
+
     return output
 
 
+def compute_environment_vars():
+    cenv = {}
+
+    # Some tasks are manually triggered by default because they might use too
+    # many resources for users of free Cirrus credits, but they can be
+    # triggered automatically by naming them in an environment variable e.g.
+    # REPO_CI_AUTOMATIC_TRIGGER_TASKS="task_name other_task" under "Repository
+    # Settings" on Cirrus CI's website.
+
+    default_manual_trigger_tasks = ['mingw']
+
+    repo_ci_automatic_trigger_tasks = env.get('REPO_CI_AUTOMATIC_TRIGGER_TASKS', '')
+    for task in default_manual_trigger_tasks:
+        name = 'CI_TRIGGER_TYPE_' + task.upper()
+        if repo_ci_automatic_trigger_tasks.find(task) != -1:
+            value = 'automatic'
+        else:
+            value = 'manual'
+        cenv[name] = value
+
+    return cenv
+
+
 def config_from(config_src):
     """return contents of config file `config_src`, surrounded by markers
     indicating start / end of the the included file
diff --git a/.cirrus.tasks.yml b/.cirrus.tasks.yml
index 45e9e35428e..3f098810452 100644
--- a/.cirrus.tasks.yml
+++ b/.cirrus.tasks.yml
@@ -590,13 +590,11 @@ task:
   << : *WINDOWS_ENVIRONMENT_BASE
   name: Windows - Server 2019, MinGW64 - Meson
 
-  # due to resource constraints we don't run this task by default for now
-  trigger_type: manual
-  # worth using only_if despite being manual, otherwise this task will show up
-  # when e.g. ci-os-only: linux is used.
-  only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*mingw.*'
-  # otherwise it'll be sorted before other tasks
+  # See REPO_CI_AUTOMATIC_TRIGGER_TASKS in .cirrus.star.
+  trigger_type: $CI_TRIGGER_TYPE_MINGW
+
   depends_on: SanityCheck
+  only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*mingw.*'
 
   env:
     TEST_JOBS: 4 # higher concurrency causes occasional failures
diff --git a/.cirrus.yml b/.cirrus.yml
index a83129ae46d..f270f61241f 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -10,12 +10,20 @@
 #
 # 1) the contents of this file
 #
-# 2) if defined, the contents of the file referenced by the, repository
+# 2) computed environment variables
+#
+#    Used to enable/disable tasks based on the execution environment. See
+#    .cirrus.star: compute_environment_vars()
+#
+# 3) if defined, the contents of the file referenced by the, repository
 #    level, REPO_CI_CONFIG_GIT_URL variable (see
 #    https://cirrus-ci.org/guide/programming-tasks/#fs for the accepted
 #    format)
 #
-# 3) .cirrus.tasks.yml
+#    This allows running tasks in a different execution environment than the
+#    default, e.g. to have sufficient resources for cfbot.
+#
+# 4) .cirrus.tasks.yml
 #
 # This composition is done by .cirrus.star
 
diff --git a/src/tools/ci/README b/src/tools/ci/README
index 30ddd200c96..771243c4da0 100644
--- a/src/tools/ci/README
+++ b/src/tools/ci/README
@@ -82,3 +82,14 @@ defined in .cirrus.yml, by redefining the relevant yaml anchors.
 Custom compute resources can be provided using
 - https://cirrus-ci.org/guide/supported-computing-services/
 - https://cirrus-ci.org/guide/persistent-workers/
+
+
+Enabling manual tasks by default
+================================
+
+Some tasks are not triggered automatically by default, to avoid using up CI
+credits too quickly. This can be changed on the repository level, e.g. when
+custom compute resources are configured.
+
+The following repository level environment variables are recognized:
+- REPO_CI_AUTOMATIC_TRIGGER_TASKS="mingw"