[SDK Sentinel] Fix cancellation-reason test time-skipping race

[sdk-sentinel-bot]

Caution

This PR contains untrusted AI-generated code. Do not approve or run CI until a maintainer has reviewed the diff. SDK Sentinel verified that GitHub Actions remained approval-gated with zero executable jobs when this PR was opened.

Summary

• CI evidence: failed CI job · workflow run · last known pass · first known failure

A macOS ARM Python 3.14 time-skipping V2 job failed while querying the cancellation-reason workflow. The [preceding main run](https://github.com/temporalio/sdk-python/actions/runs/38939898149) passed the equivalent job, while the [first observed failure](https://github.com/temporalio/sdk-python/actions/runs/38940312509/job/117105967325) timed out after the workflow reached its intentional unreachable failure.

Root cause

The workflow waited on a finite 1,000-second timer while expecting an external cancellation. Time-skipping V2 could advance that timer before the client sent cancellation, making the workflow fail repeatedly and preventing its query from completing.

Fix

Wait on a condition that cannot become true instead. It remains interruptible by workflow cancellation but gives time-skipping no timer to advance.

Validation

Both parameter cases passed five consecutive focused time-skipping V2 runs. The fixed repository validator passed. The unchanged test did not reproduce locally, so the macOS ARM Python 3.14 job remains required.

Validation status: validated-without-reproduction

• Flake confidence: high
• Fix confidence: high
• Value: medium
• Patch scope: standard — 1 changed file; 633 B
• Local reproduction: not-reproduced — The unchanged focused test passed once on Linux under time-skipping V2; the captured macOS ARM failure was not reproduced locally.
• Regression coverage: pass-after-only — The existing two-case cancellation-reason test passed five consecutive time-skipping V2 runs after the change.
• Unchanged baseline (Poe lint, bridge lint, and editable build) — passed
• Independent candidate (Poe lint, bridge lint, and editable build) — passed

Investigator-run checks

• poe test -s --workflow-environment time-skipping-v2 -k test_workflow_cancellation_reason — passed; 1 attempt(s). The unchanged checkout passed both parameter cases once on Linux, so the CI flake was not naturally reproduced.
• poe test -s --workflow-environment time-skipping-v2 -k test_workflow_cancellation_reason — passed; 5 attempt(s). Both parameter cases passed in five consecutive post-change runs.
• .ci-flake-runtime/input/validate.sh — passed; 1 attempt(s). Import sorting, formatting, pyright, mypy, basedpyright, docstyle, Rust clippy, and editable bridge build all passed.

Required target CI

• build-lint-test (3.14, macos-arm), including time-skipping-v2

Residual risks

• The failure was observed on macOS ARM and did not reproduce on the Linux investigator.
• The bounded snapshot has no same-SHA rerun proving fail-then-pass behavior.

Automation provenance

• Investigator workflow
• Base SHA: da794611dbfc746ca27c65385d00d9089de5c57b

If this finding should not be fixed, apply the sdk-sentinel:false-positive label and close the PR. Sentinel will suppress the finding until its affected source changes.

SDK Sentinel recurrence history

• Unique failed CI run attempts: 1
• First occurrence: 2026-10-16 17:50 UTC
• Latest occurrence: 2026-10-16 17:50 UTC
• Recent occurrences:
  • 2026-10-16 17:50 UTC — failed CI job