feat(coverage): the line names standing work with 0 unclassified + derive_new, copies that joined a family since the previous refresh (#2899, milestone 299 step 1)

Since the scoped bucket (#2869) the ledger reads 100% accounted while 439
derive rows stand; the standing block was gated on unclassified > 0 and so
went silent. Build it whatever the todo count ("; standing: ..."), and add
derive_new — derive-grouped rows first seen after the previous refresh
stamp — so entering a project names the drift ("+2 new copies since last
refresh: .error-msg in InceptionCard.vue") instead of waiting for an audit.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_integration_shape_classify.py

@@ -597,6 +597,39 @@ async def test_derive_groups_land_on_rows_and_in_the_summary(seeded):
     assert {r.symbol for r in rows} == {"slug"}                   # 2 files < the name floor
 
 
+@pytest.mark.integration
+async def test_derive_new_names_the_copy_that_joined_a_family_since_the_stamp(seeded):
+    """#2899: the first sync seeds one `slug`; a later sync adds an identical
+    copy. Against the stamp between them, derive_new counts ONLY the
+    newcomer — the drift since the last refresh, not the whole family."""
+    from datetime import datetime, timezone
+
+    from scribe.services.shape_ledger import (
+        apply_derive_groups, derive_new_summary, live_rows,
+    )
+
+    owner, pid = seeded["owner"], seeded["pid"]
+    first = _defs(
+        ("a/one.py", "sym", "slug", "def slug(t):", "def slug(t):\n    return t.lower()"),
+    )
+    await sync_repo_shapes(pid, REPO, first, seen_marker="m1")
+    stamp = datetime.now(timezone.utc)
+    second = _defs(
+        ("a/one.py", "sym", "slug", "def slug(t):", "def slug(t):\n    return t.lower()"),
+        ("a/two.py", "sym", "slug", "def slug(t):", "def slug(t):\n    return t.lower()"),
+    )
+    await sync_repo_shapes(pid, REPO, second, seen_marker="m2")
+    assert await apply_derive_groups(pid) == 2
+
+    rows = await live_rows(pid)
+    out = derive_new_summary(rows, since=stamp)
+    assert out["count"] == 1
+    assert out["examples"][0]["path"] == "a/two.py"
+    assert out["examples"][0]["label"] == "slug"
+    assert out["examples"][0]["group"].startswith("dup:")
+    assert derive_new_summary(rows, since=None)["count"] == 0
+
+
 # --- #2793: the divergence readout against real rows -------------------------
 
 

tests/test_pattern_coverage.py

@@ -276,6 +276,8 @@ async def test_coverage_measures_the_tree_exactly_and_caches(seeded):
     assert coverage["largest_gaps"] == [
         {"dir": "src", "unclassified": 2, "total": 3}
     ]
+    # #2899: a first computation has no previous stamp — nothing is "new".
+    assert coverage["derive_new"] == {"count": 0, "examples": []}
 
     # The walk fed the LEDGER (#2788): every extracted shape has a row, the
     # snippet reference locations are mechanically stamped canonical WITH
@@ -512,6 +514,41 @@ def test_coverage_line_names_the_proposers_standing():
     assert "top canon #2844 ×78" in line and "top copy closed-msg (identical body) ×3 files" in line
 
 
+def test_coverage_line_shows_standing_work_even_with_nothing_unclassified():
+    """#2899: since the scoped bucket a ledger can be fully accounted and
+    still carry derive groups / proposals / divergence — the line names
+    them as `standing:` instead of hiding them behind the todo count, and
+    names the drift since the previous refresh first-copy-first."""
+    from scribe.services.coverage import coverage_line
+
+    base = {
+        "total": 4693, "accounted": 4693, "unclassified": 0,
+        "counts": {"canonical": 37, "instance": 977, "variant": 73, "exempt": 1797, "scoped": 1809},
+        "computed_at": "2026-08-22T00:00:00+00:00", "largest_gaps": [],
+    }
+    quiet = coverage_line(base)
+    assert "unclassified" not in quiet and "standing" not in quiet
+    line = coverage_line({
+        **base,
+        "derive_groups": [{"group": "dup:abc", "label": "log-empty (identical body)", "files": 4}],
+        "derive_new": {"count": 2, "examples": [
+            {"label": ".error-msg", "path": "frontend/src/components/InceptionCard.vue", "group": "dup:9f0"},
+            {"label": ".error-msg", "path": "frontend/src/components/Other.vue", "group": "dup:9f0"},
+        ]},
+        "divergent": 1,
+    })
+    assert "; standing: 1 derive group, +2 new copies since last refresh: .error-msg in " \
+           "frontend/src/components/InceptionCard.vue, 1 DIVERGENT, top copy log-empty (identical body) ×4 files" in line
+    assert "unclassified" not in line
+    # One copy reads singular; with a todo the block keeps its old place.
+    one = coverage_line({**base, "derive_new": {"count": 1, "examples": []}})
+    assert one.endswith("; standing: +1 new copy since last refresh")
+    todo = coverage_line({**base, "unclassified": 3, "accounted": 4690, "proposed": 2,
+                          "derive_new": {"count": 1, "examples": [{"label": "x", "path": "a.py"}]},
+                          "largest_gaps": [{"dir": "src", "unclassified": 3, "total": 9}]})
+    assert "; 3 unclassified (2 proposed, +1 new copy since last refresh: x in a.py), largest: src" in todo
+
+
 def test_coverage_line_names_divergence_and_recheck():
     from scribe.services.coverage import coverage_line
 

tests/test_shape_ledger.py

@@ -317,6 +317,38 @@ def test_derive_groups_copy_before_name_with_floors():
     assert ("i.py", "sym", "one") not in g
 
 
+def test_derive_new_summary_counts_copies_first_seen_since_the_previous_refresh():
+    """#2899: the arrival-moment drift signal — derive-grouped rows created
+    after the previous refresh's stamp, newest first, judged rows and a
+    first seed (since=None) never count."""
+    from datetime import datetime, timedelta, timezone
+
+    from scribe.models.code_shape import CodeShape
+    from scribe.services.shape_ledger import derive_new_summary
+
+    t0 = datetime(2026, 8, 22, 12, 0, tzinfo=timezone.utc)
+
+    def row(path, symbol, at, kind="css", status="scoped", group="dup:abc", basis="derive"):
+        r = CodeShape(project_id=2, repo_key="r", path=path, symbol=symbol, kind=kind,
+                      status=status, proposal_basis=basis, proposal_group=group)
+        r.created_at = at
+        return r
+    rows = [
+        row("v/Old.vue", "error-msg", t0 - timedelta(days=3)),              # before the stamp
+        row("v/InceptionCard.vue", "error-msg", t0 + timedelta(hours=1)),   # new copy
+        row("v/Other.vue", "error-msg", t0 + timedelta(hours=2)),           # newer copy
+        row("v/J.vue", "error-msg", t0 + timedelta(hours=3), status="exempt"),   # judged: never
+        row("s/a.py", "load", t0 + timedelta(hours=1), kind="sym", group=None, basis=None),  # no family
+    ]
+    out = derive_new_summary(rows, since=t0)
+    assert out["count"] == 2
+    assert [e["path"] for e in out["examples"]] == ["v/Other.vue", "v/InceptionCard.vue"]
+    assert out["examples"][0] == {"label": ".error-msg", "path": "v/Other.vue", "group": "dup:abc"}
+    assert derive_new_summary(rows, since=None) == {"count": 0, "examples": []}
+    assert derive_new_summary(rows, since=t0, top=1)["examples"] == [
+        {"label": ".error-msg", "path": "v/Other.vue", "group": "dup:abc"}]
+
+
 def test_proposal_summary_ranks_body_identical_groups_first_and_sees_scoped_rows():
     """#2872: dup groups (the real copies) outrank name groups (usually
     convention), wider spread first; #2869: scoped rows are in the readout."""