diff --git a/.coveragerc b/.coveragerc
new file mode 100644
index 0000000..e8cb87d
--- /dev/null
+++ b/.coveragerc
@@ -0,0 +1,29 @@
+# Coverage configuration.
+#
+# This lives in a dedicated .coveragerc (INI) rather than pyproject.toml so
+# that it can be read by any coverage install. The OpenAstronomy tox workflow
+# runs `coverage combine`/`coverage xml` in the repo root via `uvx coverage`,
+# which installs a bare `coverage` without the `[toml]` extra. On Python < 3.11
+# (no stdlib tomllib) that build cannot parse a pyproject.toml config and fails
+# with "Can't read 'pyproject.toml' without TOML support".
+[run]
+omit = tests/*
+
+[report]
+exclude_lines =
+    # Have to re-enable the standard pragma
+    # and branches that don't pertain to this version of Python
+    pragma: no cover
+    pragma: py{ignore_python_version}
+    # Don't complain if tests don't hit defensive assertion code:
+    raise AssertionError
+    raise NotImplementedError
+    # Don't complain if non-runnable code isn't run
+    if __name__ == .__main__.:
+    # Don't complain about abstract methods, they aren't run:
+    @(abc\.)?abstractmethod
+    # Exclude type check blocks and Protocol contents, they aren't run:
+    if TYPE_CHECKING:
+    \.\.\.
+    # Don't complain about IPython completion helper
+    def _ipython_key_completions_
diff --git a/.github/workflows/ci_tests.yml b/.github/workflows/ci_tests.yml
index df89031..86ed41c 100644
--- a/.github/workflows/ci_tests.yml
+++ b/.github/workflows/ci_tests.yml
@@ -52,12 +52,12 @@ jobs:
         - linux: py310-test-cov
         - linux: py312-test-cov
         # All deps tests
-        - linux: py311-test-alldeps
+        - linux: py311-test-alldeps-cov
           toxargs: '-v --develop'
         - linux: py39-test-oldestdeps-alldeps-cov-clocale
         # Platform test
-        - windows: py311-test-alldeps
-        # - macos: py311-test-alldeps  # TODO: https://github.com/OpenAstronomy/github-actions-workflows/issues/197
+        - windows: py311-test-alldeps-cov
+        # - macos: py311-test-alldeps-cov  # TODO: https://github.com/OpenAstronomy/github-actions-workflows/issues/197
 
       conda: false
       coverage: codecov
diff --git a/pyproject.toml b/pyproject.toml
index 6b23074..7b36b5b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -57,28 +57,8 @@
   documentation = "https://cosmology.readthedocs.org/projects/api"
 
 
-[tool.coverage.run]
-  omit = ["tests/*"]
-
-[tool.coverage.report]
-  exclude_lines = [
-    # Have to re-enable the standard pragma
-    # and branches that don't pertain to this version of Python
-    "pragma: no cover",
-    "pragma: py{ignore_python_version}",
-    # Don't complain if tests don't hit defensive assertion code:
-    "raise AssertionError",
-    "raise NotImplementedError",
-    # Don't complain if non-runnable code isn't run
-    "if __name__ == .__main__.:",
-    # Don't complain about abstract methods, they aren't run:
-    '@(abc\.)?abstractmethod',
-    # Exclude type check blocks and Protocol contents, they aren't run:
-    "if TYPE_CHECKING:",
-    '\.\.\.',
-    # Don't complain about IPython completion helper
-    "def _ipython_key_completions_",
-  ]
+# NOTE: coverage configuration lives in .coveragerc (not here) so that the
+# bare `coverage` used by the CI workflow can read it without TOML support.
 
 [tool.hatch]
 build.targets.sdist.exclude = [
diff --git a/tox.ini b/tox.ini
index 1a6a7b0..7f015fb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -73,7 +73,7 @@ extras =
 commands =
     pip freeze
     !cov-!double: pytest --pyargs {toxinidir}/tests {toxinidir}/docs {posargs}
-    cov-!double: pytest --pyargs {toxinidir}/tests {toxinidir}/docs --cov cosmology --cov-config={toxinidir}/pyproject.toml {posargs}
+    cov-!double: pytest --pyargs {toxinidir}/tests {toxinidir}/docs --cov cosmology --cov-config={toxinidir}/.coveragerc {posargs}
     cov: coverage xml -o {toxinidir}/coverage.xml