ci: stop testing 3.13t (#5865)

* ci: stop testing 3.13t

* forbid building with 3.13t

* newsfragment

Author: davidhewitt

.github/workflows/ci.yml

@@ -233,7 +233,6 @@ jobs:
             "3.11",
             "3.12",
             "3.13",
-            "3.13t",
             "3.14",
             "3.14t",
             "3.15-dev",

newsfragments/5865.packaging.md

@@ -0,0 +1 @@
+Drop support for Python 3.13t (3.14t and above continue to be supported in alignment with CPython declaring free-threading supported starting with Python 3.14).

noxfile.py

@@ -77,7 +77,7 @@ def _supported_interpreter_versions(
     versions = [f"{major}.{minor}" for minor in range(min_minor, max_minor + 1)]
     # Add free-threaded builds for 3.13+
     if python_impl == "cpython":
-        versions += [f"{major}.{minor}t" for minor in range(13, max_minor + 1)]
+        versions += [f"{major}.{minor}t" for minor in range(14, max_minor + 1)]
     return versions
 
 
@@ -992,6 +992,14 @@ def test_version_limits(session: nox.Session):
         config_file.set("PyPy", "3.10")
         _run_cargo(session, "check", env=env, expect_error=True)
 
+        # 3.13t is no longer supported
+        config_file.set("CPython", "3.13t")
+        _run_cargo(session, "check", env=env, expect_error=True)
+
+        # 3.14t is PyO3's minimum version of free-threaded Python
+        config_file.set("CPython", "3.14t")
+        _run_cargo(session, "check", env=env)
+
     # attempt to build with latest version and check that abi3 version
     # configured matches the feature
     max_minor_version = max(int(v.split(".")[1]) for v in ABI3_PY_VERSIONS)

pyo3-ffi/build.rs

@@ -80,6 +80,19 @@ fn ensure_python_version(interpreter_config: &InterpreterConfig) -> Result<()> {
                     return Err(error.finish().into());
                 }
             }
+
+            if interpreter_config.is_free_threaded() {
+                let min_free_threaded_version = PythonVersion {
+                    major: 3,
+                    minor: 14,
+                };
+                ensure!(
+                    interpreter_config.version >= min_free_threaded_version,
+                    "PyO3 does not support the free-threaded build of CPython versions below {}, the selected Python version is {}",
+                    min_free_threaded_version,
+                    interpreter_config.version,
+                );
+            }
         }
         PythonImplementation::PyPy => {
             let versions = SUPPORTED_VERSIONS_PYPY;