diff --git a/CI/requirements_ci.in b/CI/requirements_ci.in
index 989877a..f1cb9e4 100644
--- a/CI/requirements_ci.in
+++ b/CI/requirements_ci.in
@@ -1,7 +1,7 @@
 bump-my-version==1.4.1
 exceptiongroup==1.3.1
 deptry==0.25.1
-flit==3.12.0
+flit==4.1.0
 pip==26.2
 pydantic==2.13.5
 pygments==2.20.0
diff --git a/CI/requirements_ci.txt b/CI/requirements_ci.txt
index 6d5bb23..0a213c3 100644
--- a/CI/requirements_ci.txt
+++ b/CI/requirements_ci.txt
@@ -178,13 +178,13 @@ filelock==3.25.2 \
     #   python-discovery
     #   tox
     #   virtualenv
-flit==3.12.0 \
-    --hash=sha256:1c80f34dd96992e7758b40423d2809f48f640ca285d0b7821825e50745ec3740 \
-    --hash=sha256:2b4e7171dc22881fa6adc2dbf083e5ecc72520be3cd7587d2a803da94d6ef431
+flit==4.1.0 \
+    --hash=sha256:18b463c435db03b8cbecf139b6b0bb285b2dfd8a7e623558136abd66f4a04af4 \
+    --hash=sha256:4feee56693b32d1ad2b04e727372b6bf3f3f62d1feda78ab5a7b97091c3f0158
     # via -r requirements_ci.in
-flit-core==3.12.0 \
-    --hash=sha256:18f63100d6f94385c6ed57a72073443e1a71a4acb4339491615d0f16d6ff01b2 \
-    --hash=sha256:e7a0304069ea895172e3c7bb703292e992c5d1555dd1233ab7b5621b5b69e62c
+flit-core==4.1.0 \
+    --hash=sha256:17398cdd2c38b24047a5a9c93089ec5c0bf12ec3d1469bbf69c27ed7965299db \
+    --hash=sha256:62e12b63ead8335b37f59fabb977c7167fe476dafb5e41785dfa8c9aff843bc6
     # via flit
 h11==0.16.0 \
     --hash=sha256:4e35b956cf45792e4caa5885e69fba00bdbc6ffafbfa020300e549b208ee5ff1 \
diff --git a/environment-dev.yml b/environment-dev.yml
index 2968fe6..30ffe92 100644
--- a/environment-dev.yml
+++ b/environment-dev.yml
@@ -17,7 +17,7 @@ dependencies:
   - coverage >=7.5.0
   - flake8 >=7.1.1
   - flake8-rst-docstrings >=0.3.0
-  - flit >=3.10.1,<4.0
+  - flit >=4.0,<5.0
   - numpydoc >=1.8.0
   - pip >=25.0
   - pre-commit >=3.5.0
diff --git a/pyproject.toml b/pyproject.toml
index f3c8165..1faf0a7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["flit_core >=3.12.0,<4"]
+requires = ["flit_core >=4.0,<5.0"]
 build-backend = "flit_core.buildapi"
 
 [dependency-groups]
@@ -40,6 +40,7 @@ tox = [
 dev = [
   # Development and testing tools
   "bump-my-version >=1.3.0",
+  "flit >=4.0,<5.0",
   "pip >=26.0.1",
   "prek >=0.3.0",
   "watchdog >=6.0.0",