Python: [Bug]: native Windows --files paths skip changed-package tasks #9742

Observed Behavior

At main 1168c001dd228d6c7a623fd14f53e1f05b7b4540, python/scripts/run_tasks_in_changed_packages.py recognizes a repository-relative path with / but not the native Windows spelling with \. The complete get_changed_packages() function returns an empty set for python\packages\core\agent_framework\_types.py, while the same forward-slash path selects core. A native path to the redis package is also omitted.

The function strips only the text prefix python/, then joins the remaining path to workspace_root, which already ends in python. The native spelling therefore points under python/python. The calling script returns without running tasks when the set is empty. The package-routing result was reproduced directly; the task runner itself was not executed.

Expected Behavior

Repository-relative paths in the platform's native spelling should select the same package as equivalent forward-slash paths. Workspace-relative and absolute paths should keep their current behavior.

Steps to Reproduce

1. Check out the above main commit on Windows.
2. Run the standard-library-only probe below from the repository root.
3. Observe that only the forward-slash path selects core; the native repo-relative path returns an empty set.

Minimal Reproduction

import ast
from pathlib import Path

source = Path("python/scripts/run_tasks_in_changed_packages.py")
tree = ast.parse(source.read_text(encoding="utf-8"))
function = next(n for n in tree.body if isinstance(n, ast.FunctionDef)
                and n.name == "get_changed_packages")
namespace = {"Path": Path}
exec(compile(ast.Module(body=[function], type_ignores=[]), str(source), "exec"), namespace)
workspace = Path("python").resolve()
projects = [Path("packages/core")]
for spelling in ["python/packages/core/agent_framework/_types.py",
                 str(Path("python/packages/core/agent_framework/_types.py"))]:
    print(repr(spelling), namespace["get_changed_packages"](projects, [spelling], workspace))

This executes the exact complete routing function with native pathlib and real path values. It avoids importing the task runner and does not stub Path or execute package commands.

Error Messages and Stack Traces

No exception: the native repo-relative case returns (set(), False).

Package Versions

Repository script at main 1168c00; no installed agent-framework package used.

Python Version

CPython 3.12.14 AMD64

Operating System

Windows

Regression

Unknown

Additional Context

Six native routing cases were observed: repository-relative forward/native, workspace-relative forward/native, absolute core, and native repo-relative redis. Four passed; the latter native repo-relative core/redis cases did not. An isolated diagnostic variant using native Path components recognized all six. This is not a full CLI, SDK, build, type-checking or CI result. No repository branch, source change or PR has been submitted for this observation; maintainer direction is requested before proceeding with a production change.

AI Assistance

Codex assisted the report analysis and diagnostic code. The submitter is responsible for verifying this report.

Acknowledgements

• I searched existing issues and did not find a duplicate.
• I personally verified this behavior and the reproduction details are authentic.
• I will wait for explicit maintainer agreement before starting implementation of a non-trivial change.