fix(learning-harness): a baseline over a named slice measures that slice

`--slice vfc` selected the vfc rows and `run_baseline` filtered them all out
again against its own default of the two web slices, so the memory-safety
baseline Req 8.4 asks for produced an empty report and said nothing about it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG

src/openultrasast/cli.py

@@ -1257,7 +1257,7 @@ def _learning_run(args: argparse.Namespace, cases: Sequence[PairCase], taxonomy:
     from .learning.detectors import load_family_configs, write_default_configs
     from .learning.endpoint import resolve_chat_endpoint, resolve_models
     from .learning.journal import Archive, LearningJournal
-    from .learning.rounds import MIN_K_RUNS, load_noise_floors, run_baseline, run_learning_round
+    from .learning.rounds import DEFAULT_SLICES, MIN_K_RUNS, load_noise_floors, run_baseline, run_learning_round
     from .learning.scoring import aggregate
     from .tool_hunter import _SYSTEM_PROMPT
 
@@ -1320,6 +1320,9 @@ def _learning_run(args: argparse.Namespace, cases: Sequence[PairCase], taxonomy:
             out_dir=out,
             k_runs=k_runs,
             cutoff=config.learning.cutoff_date or "",
+            # `--slice` already chose the rows; without this the baseline's own default filters them out again and
+            # a run over the memory-safety slice reports nothing at all (Req 8.4).
+            slices=(args.slice,) if args.slice != "all" else DEFAULT_SLICES,
         )
         print(f"learning baseline {model}: {len(report.floors)} families, k={report.k_runs} -> {out / 'baseline'}")
         return 0

tests/test_learning_cutoff.py

@@ -171,3 +171,43 @@ def test_the_command_line_reports_the_slice_the_cutoff_and_the_undated_count(tmp
     )
     line = next(item for item in captured if item.startswith("learning score injection"))
     assert "post-cutoff(2025-07-01)=2" in line and "undated=0" in line
+
+
+def test_a_baseline_over_a_named_slice_measures_that_slice(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    """`--slice vfc` selected the vfc rows and then `run_baseline` filtered them all out again.
+
+    Its `slices` default is the two web slices, so a baseline over the memory-safety slice — the run Req 8.4 asks
+    for as a measured, non-gating number — produced an empty report and said nothing about it."""
+    import sys
+
+    sys.path.insert(0, str(Path(__file__).parent))
+    from test_learning_cli import CATALOG, FIXED, VULN, _detector  # noqa: PLC0415
+
+    from openultrasast.cli import main
+
+    (tmp_path / "a-v.py").write_text(VULN)
+    (tmp_path / "a-f.py").write_text(FIXED)
+    (tmp_path / "pairs.toml").write_text(CATALOG.format(name="a", split="train").replace('slice = "vibe-py"', 'slice = "vfc"'))
+    _detector(monkeypatch)
+    assert (
+        main(
+            [
+                "learning",
+                "baseline",
+                "--catalog",
+                str(tmp_path / "pairs.toml"),
+                "--slice",
+                "vfc",
+                "--out",
+                str(tmp_path / "l"),
+                "--k-runs",
+                "3",
+                "--model",
+                "m",
+            ]
+        )
+        == 0
+    )
+    report = json.loads((tmp_path / "l" / "baseline" / "m" / "report.json").read_text())
+    assert report["slices"] == ["vfc"]
+    assert report["metrics"]["injection"]["scorable"] == 1