Fix broken CI -- update python command for Linux Helix work items

[danmoseley]

Note

This PR description was AI/Copilot-generated.

Fix python: not found on Linux Helix work items

The updated Ubuntu 22.04 Helix image (Helix-Ubuntu-2204-2026-03-23) no longer provides a python command — only python3 is available. This broke all Linux Helix work items in public CI with exit code 127.

Main branch has been red since March 26 (build 1354108 onward; last green was 1353009 on March 25).

Changes

• get_work_item_command(): Change the non-Windows command from python to python3 (line 598). The Windows path (python, line 593) is correct as-is.
• PerfSendToHelixArgs: Use the existing agent_python variable (python3 on Linux, py -3 on Windows) for the $(Python) env var passed to .proj files, instead of unconditionally using "python".

Internal builds were unaffected because they create a Python venv first, which provides a python symlink.

Why this is safe

$(Python) is consumed by all the scenario .proj files (pre.py, test.py, post.py, etc.). The new values (python3 on Linux, py -3 on Windows) are the same values already used by the agent itself — see line 1157 (os.environ["Python"] = agent_python) and run-performance-job-script-step.yml line 6. Python venvs create both python and python3 symlinks, so internal builds (which use a venv) are also unaffected. The hardcoded "python" was the oddball; this change makes the Helix work item value consistent with the rest of the infrastructure.

[danmoseley]

@caaavik-msft as an aside, how about enabling copilot review on new PR's (repo settings). either on first push only, or all. but I think first push only is a definite good thing.

[Copilot]

Pull request overview

Updates the Helix work item Python invocation to match modern Linux images where python is no longer available, restoring Linux Helix CI reliability.

Changes:

• Switch non-Windows Helix work item command execution from python to python3.
• Pass the platform-correct agent_python value into PerfSendToHelixArgs.python so .proj scenario work items use the correct Python launcher via $(Python).

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[danmoseley]

Note

This comment was AI/Copilot-generated.

Why is Windows OK with just python?
Windows Helix images install Python via the windows-python-3 artifact, which puts python.exe on PATH. On Windows, python has always meant Python 3 (there's no Python 2 legacy issue). Ubuntu dropped the unversioned python symlink years ago — it only ships python3.

What is agent_python?
Defined at lines 1015-1018 of run_performance_job.py:

if args.os_group == "windows":
    agent_python = "py -3"
else:
    agent_python = "python3"

py -3 is the Windows Python Launcher — it finds the installed Python 3 automatically. It was originally meant for commands running on the AzDO agent machine (e.g., line 1157: os.environ["Python"] = agent_python), but the same values are correct for Helix machines too, since both Windows Helix images and AzDO agents have the Python launcher installed.

[danmoseley]

CI passed!

[DrewScoggins]

Going to do a quick test to make sure that all of our internal machines have the python3 alias. Once that looks good we can get this merged.

[LoopedBard3]

Looks good to me once we have a regular test run .👍