[iris] Add preemptible flag for `job run`

[eric-czech]

context: discord

This would make it possible to force execution on preemptible VMs rather than only supporting the heuristic @rjpower mentioned in here.

[rjpower]

@claude /fix-issue implement this one as a PR for me

[claude]

Claude finished @rjpower's task in 52s —— View job

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Research

iris job run had no user-facing flag to select preemptible workers — callers could only rely on the executor heuristic that auto-pins small CPU-only jobs to non-preemptible (job.py#L590-L597). The underlying constraint helper already exists and supports both directions (constraints.py#L301-L319); only the CLI surface was missing.

Relevant code

• cli/job.py#L582-L597 — constraint assembly + executor heuristic
• cluster/constraints.py#L301-L319 — preemptible_constraint(bool, soft=None)
• cluster/constraints.py#L832-L848 — infer_preemptible_constraint (no-ops when one is already set)

Fix — PR #5083

Added --preemptible/--no-preemptible to iris job run, threaded through run_iris_job(preemptible: bool | None). When set, appends preemptible_constraint(value) before the heuristic — infer_preemptible_constraint short-circuits on any existing preemptible constraint, so the flag wins. Refactored constraint assembly into build_job_constraints() so the new behavior is unit-testable without mocking the controller.

Testing

• ./infra/pre-commit.py --all-files --fix → OK (ruff, black, pyrefly, etc.)
• uv run --group dev python -m pytest -n1 tests/cli/ tests/cluster/test_constraints.py (iris) → 86 passed
• Four new tests in tests/cli/test_job.py:
  • --preemptible emits preemptible=true
  • --no-preemptible emits preemptible=false even on large jobs (heuristic wouldn't fire)
  • default (None) preserves the executor heuristic
  • --preemptible overrides the heuristic (no duplicate constraint)

CI Status

23 pass, 20 skip, 1 fail:

• cw-ci-test (CoreWeave integration) — failed with rigging.distributed_lock.LeaseLostError on quickstart-tests/cleaned_c4c77152. Infrastructure flake, unrelated to this patch (the matching GCP marin-itest passed; this change only adds a CLI flag + constraint wiring).

All iris/marin/zephyr unit test, lint, CodeQL, build, and smoke checks passed.

Todo

• Research + propose fix
• Write tests
• Implement --preemptible / --no-preemptible
• ./infra/pre-commit.py --all-files --fix
• uv run pytest (iris)
• Push + open PR #5083
• Verify CI (all non-CoreWeave checks green; CW flake documented)
  · branch claude/issue-4540-20260422-2145 · PR #5083