diff --git a/MODULE.bazel b/MODULE.bazel
index 11683d38a880..b5ef04c47d30 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -112,7 +112,7 @@ bazel_dep(name = "rules_python", version = "1.9.0")
 
 python = use_extension("@rules_python//python/extensions:python.bzl", "python")
 python.toolchain(
-    python_version = "3.11",
+    python_version = "3.12",
 )
 use_repo(python, "python_versions")
 
diff --git a/bazel/check_deps/update_roots.py b/bazel/check_deps/update_roots.py
index 0bb52a4d39eb..1ae3d661d2bd 100755
--- a/bazel/check_deps/update_roots.py
+++ b/bazel/check_deps/update_roots.py
@@ -1,4 +1,9 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# ///
+
 
 """Update the roots of the Carbon build used for dependency checking.
 
diff --git a/bazel/version/gen_tmpl.py b/bazel/version/gen_tmpl.py
index 19880353534b..a6264ced04e6 100755
--- a/bazel/version/gen_tmpl.py
+++ b/bazel/version/gen_tmpl.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 # NOTE: The `uv` shebang and inline metadata above are only used for direct
diff --git a/examples/bazel/update_module_to_nightly.py b/examples/bazel/update_module_to_nightly.py
index d637492c24de..fd0af2333b14 100755
--- a/examples/bazel/update_module_to_nightly.py
+++ b/examples/bazel/update_module_to_nightly.py
@@ -1,4 +1,9 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# ///
+
 
 """Updates example module file to use the nightly toolchain release.
 
diff --git a/github_tools/MODULE.bazel b/github_tools/MODULE.bazel
index 8ccf8ad5bb98..dd4c52a8ea1b 100644
--- a/github_tools/MODULE.bazel
+++ b/github_tools/MODULE.bazel
@@ -16,7 +16,7 @@ bazel_dep(name = "rules_python", version = "0.27.1")
 
 python = use_extension("@rules_python//python/extensions:python.bzl", "python")
 python.toolchain(
-    python_version = "3.11",
+    python_version = "3.12",
 )
 use_repo(python, "python_versions")
 
@@ -24,7 +24,7 @@ use_repo(python, "python_versions")
 pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
 pip.parse(
     hub_name = "py_deps",
-    python_version = "3.11",
+    python_version = "3.12",
     requirements_lock = "//:requirements.txt",
 )
 use_repo(pip, "py_deps")
diff --git a/github_tools/check_dependent_pr.py b/github_tools/check_dependent_pr.py
index 71ee8ecb5b74..6caab69a18c1 100755
--- a/github_tools/check_dependent_pr.py
+++ b/github_tools/check_dependent_pr.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.10"
+# requires-python = ">=3.12"
 # dependencies = [
 #   "gql==2.0.0",
 #   "requests",
diff --git a/github_tools/pr_comments.py b/github_tools/pr_comments.py
index a2785111101b..0c81150b52b0 100755
--- a/github_tools/pr_comments.py
+++ b/github_tools/pr_comments.py
@@ -1,4 +1,13 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# dependencies = [
+#   "gql==2.0.0",
+#   "requests",
+# ]
+# ///
+
 
 """Figure out comments on a GitHub PR."""
 
@@ -14,7 +23,7 @@ import hashlib
 import importlib.util
 import os
 import textwrap
-from typing import Any, Callable, Optional
+from typing import Any, Callable, Optional, override
 
 # Do some extra work to support direct runs.
 try:
@@ -178,6 +187,7 @@ class _PRComment(_Comment):
     def __lt__(self, other: "_PRComment") -> bool:
         return self.timestamp < other.timestamp
 
+    @override
     def format(self, long: bool) -> str:
         return "%s\n%s" % (self.url, super().format(long))
 
diff --git a/proposals/p000555-operator-precedence/figures.py b/proposals/p000555-operator-precedence/figures.py
index ee66b7207797..82baf6c11d5c 100755
--- a/proposals/p000555-operator-precedence/figures.py
+++ b/proposals/p000555-operator-precedence/figures.py
@@ -1,4 +1,9 @@
-#! /usr/bin/env python
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# ///
+
 
 __copyright__ = """
 Part of the Carbon Language project, under the Apache License v2.0 with LLVM
diff --git a/proposals/scripts/check_proposal_names.py b/proposals/scripts/check_proposal_names.py
index f12c0072211a..c6e28e37d7e5 100755
--- a/proposals/scripts/check_proposal_names.py
+++ b/proposals/scripts/check_proposal_names.py
@@ -1,4 +1,9 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# ///
+
 
 """Renames proposal files to match convention."""
 
diff --git a/proposals/scripts/new_proposal.py b/proposals/scripts/new_proposal.py
index 5acc9cf9a4ab..396a21b7df74 100755
--- a/proposals/scripts/new_proposal.py
+++ b/proposals/scripts/new_proposal.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 """Prepares a new proposal file and PR."""
diff --git a/pyproject.toml b/pyproject.toml
index a32c90a72d2b..8566f46abf5b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,11 +3,11 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 [project]
-requires-python = ">=3.11"
+requires-python = ">=3.12"
 
 [tool.ruff]
 line-length = 80
-target-version = "py310"
+target-version = "py312"
 
 [tool.ruff.lint]
 select = ["E", "F", "W", "I", "ANN"]
diff --git a/scripts/bazel_mod_deps.py b/scripts/bazel_mod_deps.py
index 5dec2dfcd9db..515994df249c 100755
--- a/scripts/bazel_mod_deps.py
+++ b/scripts/bazel_mod_deps.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/bench_runner.py b/scripts/bench_runner.py
index e7d3814dee73..60141e791534 100755
--- a/scripts/bench_runner.py
+++ b/scripts/bench_runner.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.10"
+# requires-python = ">=3.12"
 # dependencies = [
 #     "numpy",
 #     "rich",
@@ -73,7 +73,7 @@ from collections import defaultdict
 from dataclasses import dataclass, field
 from enum import Enum
 from pathlib import Path
-from typing import Optional
+from typing import Optional, override
 
 import numpy as np  # type: ignore
 import scipy as sp  # type: ignore
@@ -288,6 +288,7 @@ class DeltaKind(Enum):
     REGRESSION = "[slower]👎[/slower]"
     NOISE = ""
 
+    @override
     def __str__(self) -> str:
         return self.value
 
diff --git a/scripts/calculate_release_shas.py b/scripts/calculate_release_shas.py
index 171c3a377ace..a6dcfa245d88 100755
--- a/scripts/calculate_release_shas.py
+++ b/scripts/calculate_release_shas.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/check_build_graph.py b/scripts/check_build_graph.py
index 6e37bd3bf785..d5e9e30f2b47 100755
--- a/scripts/check_build_graph.py
+++ b/scripts/check_build_graph.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/check_header_guards.py b/scripts/check_header_guards.py
index 987304a7e9ff..eb036296c684 100755
--- a/scripts/check_header_guards.py
+++ b/scripts/check_header_guards.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 """Checks for missing or incorrect header guards."""
diff --git a/scripts/check_sha_filenames.py b/scripts/check_sha_filenames.py
index 8c36b6b3c7fe..73d823999b08 100755
--- a/scripts/check_sha_filenames.py
+++ b/scripts/check_sha_filenames.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/create_compdb.py b/scripts/create_compdb.py
index 6a0c3abf8351..e938db1281d5 100755
--- a/scripts/create_compdb.py
+++ b/scripts/create_compdb.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/fix_cc_deps.py b/scripts/fix_cc_deps.py
index 107756a32912..23aed858dea6 100755
--- a/scripts/fix_cc_deps.py
+++ b/scripts/fix_cc_deps.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/forbid_llvm_googletest.py b/scripts/forbid_llvm_googletest.py
index a76f4bc3d953..6dc53c3b9993 100755
--- a/scripts/forbid_llvm_googletest.py
+++ b/scripts/forbid_llvm_googletest.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/query_module_versions.py b/scripts/query_module_versions.py
index e04fdcb3db2e..e9037ec87aec 100755
--- a/scripts/query_module_versions.py
+++ b/scripts/query_module_versions.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/run_bazel.py b/scripts/run_bazel.py
index 148ffef14662..fdce58e6999a 100755
--- a/scripts/run_bazel.py
+++ b/scripts/run_bazel.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/run_bazelisk.py b/scripts/run_bazelisk.py
index cb5e78c00e3c..41d1f759ad0f 100755
--- a/scripts/run_bazelisk.py
+++ b/scripts/run_bazelisk.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/run_buildifier.py b/scripts/run_buildifier.py
index 51b068a75371..51400b2baa14 100755
--- a/scripts/run_buildifier.py
+++ b/scripts/run_buildifier.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/run_buildozer.py b/scripts/run_buildozer.py
index 8ffd678502e1..602dfe29eaa8 100755
--- a/scripts/run_buildozer.py
+++ b/scripts/run_buildozer.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/source_stats.py b/scripts/source_stats.py
index 430a70e3fac1..884306592d51 100755
--- a/scripts/source_stats.py
+++ b/scripts/source_stats.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/target_determinator.py b/scripts/target_determinator.py
index 527139b6b7ae..e9ea73b13ab7 100755
--- a/scripts/target_determinator.py
+++ b/scripts/target_determinator.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 
diff --git a/scripts/workspace_status.py b/scripts/workspace_status.py
index 20fe4609fecc..8b331976f56a 100755
--- a/scripts/workspace_status.py
+++ b/scripts/workspace_status.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 # NOTE: The `uv` shebang and inline metadata above are only used for direct
diff --git a/toolchain/autoupdate_testdata.py b/toolchain/autoupdate_testdata.py
index 0806be0ecb02..64abdc1f37b8 100755
--- a/toolchain/autoupdate_testdata.py
+++ b/toolchain/autoupdate_testdata.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 """Autoupdates testdata in toolchain."""
diff --git a/toolchain/diagnostics/check_diagnostics.py b/toolchain/diagnostics/check_diagnostics.py
index 5e0c41b709f0..c4e74db735b9 100755
--- a/toolchain/diagnostics/check_diagnostics.py
+++ b/toolchain/diagnostics/check_diagnostics.py
@@ -1,4 +1,9 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run --script
+
+# /// script
+# requires-python = ">=3.12"
+# ///
+
 
 """Checks diagnostic use.
 
@@ -19,7 +24,7 @@ import re
 import sys
 from concurrent import futures
 from pathlib import Path
-from typing import Dict, List, NamedTuple, Set
+from typing import Dict, List, NamedTuple, Set, override
 
 # Example or test diagnostics, ignored because they're expected to not pass.
 IGNORED = set(
@@ -36,6 +41,7 @@ IGNORED = set(
 class Loc(NamedTuple):
     """A location for a diagnostic."""
 
+    @override
     def __str__(self) -> str:
         return f"{str(self.path)}:{self.line}"
 
diff --git a/website/prebuild.py b/website/prebuild.py
index 5503fa695e86..3feaec98797f 100755
--- a/website/prebuild.py
+++ b/website/prebuild.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env -S uv run --script
 
 # /// script
-# requires-python = ">=3.11"
+# requires-python = ">=3.12"
 # ///
 
 """Updates files in preparation for a jekyll build.