[dan-petty]

The stage row and the alternatives row of the Service planned every selected item first and wrote the results after. A stop of the Service, or a kill of the worker, lost every finished plan of the round, and a stage plan can use up to 1.5 million input tokens. Now each row writes the result of an item when the item is done, with StageWriter and AlternativesWriter, as RefineWriter does for the refine row (#3631). A stop of the Service ends a stage round after it records the failures of the finished items. A rate limit on a write ends an alternatives round at once. The plan-only command writes nothing.

Closes #4034

Change: openspec/changes/archive/2026-11-07-4034-write-each-stage-alternatives-item/

[dan-petty]

Test record for this pull request (before the final rebase, then re-run).

fail-to-pass (devops ci fail-to-pass --base origin/main), run on the base tree:

• failed on base, pass now (6): stage killed_between_items, stage service_stopping, stage phase order (removals before the first plan call), stage phase order (moved paths per item), alternatives killed_between_items, alternatives rate_limit.
• guards that pass on base and now (3): both plan-only tests and the rejection order of a selected item.

Full devops ci on the tree before the archive commit: exit 0, 25 rows pass. The test row took 21 min 5 s, over the 5 min budget, because of the slow replays in tests/roadmap/stage/test_roadmap_stage_eval_*.py. This change does not touch them (known class #3593).

After the rebase onto origin/main (two merged changes, one conflict in openspec/specs/roadmap-stage/spec.md, kept both sides): test_roadmap_stage_item_writes.py 6 passed, test_roadmap_alternatives_item_writes.py 3 passed, test_roadmap_stage_apply.py 34 passed, test_roadmap_stage_plan.py 163 passed. devops docs generate --check, devops openspec check and mypy on the three changed source files pass.

[dan-petty]

Update: the Fail-to-Pass check failed on the first push. The pytest plugin tests/support/roadmap_stage.py imported StageWriter at module level, so the replay on the base tree could not load it. The two test helpers now import StageWriter and AlternativesWriter inside the function (c31a450). Local devops ci fail-to-pass --base origin/main now reports 125 tests failed on base and pass on this branch. All 25 checks pass.