Summary

Correct, well-scoped fix — the PowerShell conversion is necessary for this workflow to run at all on the Windows strix-halo runner, and it faithfully follows the if ($LASTEXITCODE -ne 0) { throw } convention already established for self-hosted STX hardware in build_cpp.yml. The artifact-path fix is also right: I traced it through to the harness, which writes transcripts.json into tmp_path/artifacts/ on failure, so pinning --basetemp makes that path deterministic and the upload glob now actually matches. The one thing worth confirming before merge is whether the targeted runner is really labeled strix-halo — every sibling workflow uses stx/stx-test instead, and the PR description itself says the label is stx-test.

Issues Found

🟡 Runner label may not match the actual runner (test_agent_behavior_e2e.yml:21)

This PR's goal is "so the harness can finally execute," but that hinges on runs-on: [self-hosted, strix-halo] actually scheduling onto the intended box. Two signals suggest it may not:

• Every other self-hosted-STX workflow (build_cpp.yml:163, test_agent_sdk.yml:38, test_api.yml:44, …) selects the runner via the stx-test/stx labels, not strix-halo.
• The PR description states the runner sjlab-stx-halo-18 carries the label stx-test.

If the runner isn't actually tagged strix-halo, the job stays queued forever and the PowerShell fix — though correct — won't be exercised. Line 21 is outside this diff (pre-existing), so this isn't a blocker on the change itself, but since it directly determines whether the PR achieves its stated purpose, please confirm the runner's labels (or align with the stx-test/stx selector the other workflows use). No code suggestion since the right value depends on the runner's actual registration.

🟢 Mixed path separators in the upload glob (test_agent_behavior_e2e.yml:52,46)

Minor consistency nit, not a bug: --basetemp uses a backslash (${{ runner.temp }}\pytest-behavior) while the upload path uses forward slashes (${{ runner.temp }}/pytest-behavior/...). actions/upload-artifact's glob normalizes separators on Windows so this works as-is — flagging only for readability. Forward slashes are fine in both spots if you want them uniform.

Strengths

• Verified the failure path end-to-end — --basetemp → pytest tmp_path → BehaviorHarness._dump_artifacts writing transcripts.json; the new glob pytest-behavior/**/artifacts/** correctly captures it where the old /tmp/pytest-*/... glob could never match on Windows.
• Convention-faithful — the $LASTEXITCODE guard after each command mirrors build_cpp.yml exactly, preserving fail-loudly behavior that bash's && chaining gave for free.
• Tight, single-purpose diff with a clear top-of-file comment explaining why PowerShell is required — exactly the kind of WHY note that survives.

Verdict

Approve with suggestions — the change is correct and ready. Just confirm the strix-halo runner label resolves to a real runner before relying on this in CI; if it doesn't, that's a one-line follow-up, not a problem with this diff.