diff --git a/.agents/rules/pr.md b/.agents/rules/pr.md
index ae75aa34fe..bc6f87f44b 100644
--- a/.agents/rules/pr.md
+++ b/.agents/rules/pr.md
@@ -25,6 +25,8 @@ Before drafting any pull request description, strictly adhere to the rules in
   (`.github/workflows/`).
 * `tests:`: Test-only changes and test-helper fixes (never `fix:` or
   `fix(tests):`).
+* `agents:` / `agents(<scope>):`: Agent rules, skills, and prompts
+  (`.agents/`).
 
 ## PR Commit Workflow Invariant
 * Once a Pull Request is created, always make new commits or merge commits.
diff --git a/.agents/rules/python.md b/.agents/rules/python.md
index 0c4fd69da8..fd7aef7cb7 100644
--- a/.agents/rules/python.md
+++ b/.agents/rules/python.md
@@ -26,6 +26,9 @@
   link to its definition in the docstring.
 
 ## Type Checking & Annotations
+* **Version differences**: Guard version-specific arguments or APIs with runtime
+  checks (e.g. `if sys.version_info >= (3, 13):`) instead of
+  `# pyrefly: ignore[...]` comments.
 * **`importlib.metadata` `PackagePath`**: `f.locate()` is typed as `PathLike`.
   Wrap with `pathlib.Path(f.locate())` to call `.exists()`, `.is_file()`, etc.
 * **In-file disables vs target skipping**: Prefer
diff --git a/.agents/rules/testing.md b/.agents/rules/testing.md
index dceb91d24e..cd56f69105 100644
--- a/.agents/rules/testing.md
+++ b/.agents/rules/testing.md
@@ -37,3 +37,7 @@
 * **Platform Constraints**: Restrict OS-specific targets with
   `target_compatible_with` (e.g., `["@platforms//os:windows"]`) to skip on
   incompatible platforms.
+* **Multi-version `pytest_test`**: Restrict targets using `python_versions` to
+  Bzlmod with `target_compatible_with = SUPPORTS_BZLMOD`
+  (`//tests/support:support.bzl`). WORKSPACE mode resolves pip dependencies for
+  only the host Python version.
diff --git a/python/runfiles/runfiles.py b/python/runfiles/runfiles.py
index 0c56702216..9650563830 100644
--- a/python/runfiles/runfiles.py
+++ b/python/runfiles/runfiles.py
@@ -385,6 +385,7 @@ def iterdir(self) -> Generator[Self, None, None]:
         for p in resolved.iterdir():
             yield self / p.name
 
+    # Return types and keyword arguments vary across Python versions in typeshed.
     @override
     def glob(  # pyrefly: ignore[bad-override]
         self,
@@ -407,6 +408,7 @@ def glob(  # pyrefly: ignore[bad-override]
         for p in it:
             yield self / p.relative_to(resolved)
 
+    # Return types and keyword arguments vary across Python versions in typeshed.
     @override
     def rglob(  # pyrefly: ignore[bad-override]
         self,