feat(ledger): reason codes, case-insensitive repo filter, next action on the coverage line (#2874, milestone 294)

- code_shapes.reason_code (migration 0083): an optional code from a fixed
  catalogue (scoped-css, one-off-handler, test-helper, convention-plumbing,
  pure-helper, generated, script, typed-record) beside the prose reason, so
  the ledger can be filtered/aggregated by kind of one-off; validated in
  classify_shapes and classify_shapes_by_rule; on to_dict/to_compact.
- Snippet location lookups match repo case-insensitively in both dialects
  (location_matches / location_jsonpath via like_regex flag "i") — "Scribe"
  vs "FabledScribe" vs "fabledscribe" recorded free-form hid half the canon
  from list_snippets(repo=, path=).
- coverage line names the next action: "top canon #N ×k" (biggest proposal
  queue) and "top copy <label> ×files" (widest body-identical group).

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

alembic/versions/0083_code_shape_reason_code.py

@@ -0,0 +1,26 @@
+"""Exempt/variant reason codes — a small fixed catalogue beside the prose (#2874, milestone 294)
+
+Revision ID: 0083
+Revises: 0082
+Create Date: 2026-08-21
+
+The 2026-08 audit wrote the same free-text reason thousands of times
+("scoped rule — styles one element of this view"); a judgment's WHY stays
+prose, but an optional code from a fixed catalogue makes the ledger
+filterable and aggregable ("how many pure helpers, how many test helpers").
+"""
+import sqlalchemy as sa
+from alembic import op
+
+revision = "0083"
+down_revision = "0082"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("code_shapes", sa.Column("reason_code", sa.Text(), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("code_shapes", "reason_code")

src/scribe/mcp/tools/shapes.py

@@ -36,10 +36,14 @@ async def classify_shapes(
     Args:
         project_id: The project whose ledger is being judged.
         classifications: Objects of {path, symbol, status, kind?, snippet_id?,
-            reason?}. path+symbol name the shape exactly as list_shapes shows
+            reason?, reason_code?}. path+symbol name the shape exactly as
-            it; kind ("sym"/"css") narrows when one file defines both.
+            list_shapes shows it; kind ("sym"/"css") narrows when one file
-            snippet_id is required for canonical/instance/variant; reason is
+            defines both. snippet_id is required for canonical/instance/
-            required for variant/exempt.
+            variant; reason is required for variant/exempt. reason_code is
+            an OPTIONAL index beside the prose (one of: scoped-css,
+            one-off-handler, test-helper, convention-plumbing, pure-helper,
+            generated, script, typed-record) so the ledger can be filtered
+            and aggregated by kind of one-off — the prose stays the record.
         via: Who is judging — "agent" (default), "audit" (a sweep), or
             "import" (carrying maps recorded elsewhere).
 
@@ -145,6 +149,7 @@ async def classify_shapes_by_rule(
     reason: str = "",
     via: str = "agent",
     include_judged: bool = False,
+    reason_code: str = "",
 ) -> dict:
     """The sweep form of classify_shapes: ONE judgment applied to every
     unclassified shape under a directory whose symbol matches a glob.
@@ -167,6 +172,8 @@ async def classify_shapes_by_rule(
         snippet_id: Required for instance/variant — the canon judged against.
         reason: Required for variant/exempt — the why, recorded on every row.
         via: "agent" (default) | "audit" | "import".
+        reason_code: Optional catalogue code beside the reason (see
+            classify_shapes) — a sweep is exactly where one applies.
         include_judged: By default only unjudged rows are touched —
             `unclassified` and the sync's mechanical `scoped` stamp — a
             sweep never silently overwrites a judgment. True re-judges every
@@ -184,6 +191,7 @@ async def classify_shapes_by_rule(
             uid, project_id, path=path, status=status, pattern=pattern,
             kind=kind, snippet_id=snippet_id or None, reason=reason or None,
             via=via, include_judged=include_judged,
+            reason_code=reason_code or None,
         )
     except ValueError as exc:
         return {"error": str(exc)}

src/scribe/models/code_shape.py

@@ -26,6 +26,20 @@ from scribe.models.base import TimestampMixin, iso
 SHAPE_STATUSES = ("canonical", "instance", "variant", "exempt", "scoped", "unclassified")
 SHAPE_CLASSIFIERS = ("agent", "audit", "hook", "mechanical", "import")
 
+# The reason catalogue (#2874): an OPTIONAL code beside the prose reason on
+# variant/exempt rows, so the ledger can be filtered and aggregated by kind
+# of one-off. The prose remains the record; the code is the index.
+REASON_CODES = (
+    "scoped-css",            # a scoped rule styling one element (pre-#2869 rows)
+    "one-off-handler",       # a view/component handler or loader, one per surface
+    "test-helper",           # a test module's stub, driver or fixture data
+    "convention-plumbing",   # registration, wiring, app factory — one of each
+    "pure-helper",           # a sync module-private helper with no session
+    "generated",             # generated source (theme.css, protos, bundles)
+    "script",                # a standalone dev/CI script
+    "typed-record",          # a NamedTuple / dataclass / error class — one each
+)
+
 # How the mechanical proposer (#2792) arrived at a proposal, strongest first.
 # `derive` is the odd one out: not "this is an instance of #N" but "this
 # shape repeats with NO canon — derive one first" (note 2786's derive-first
@@ -105,6 +119,7 @@ class CodeShape(Base, TimestampMixin):
         BigInteger, ForeignKey("notes.id", ondelete="SET NULL"), nullable=True
     )
     reason: Mapped[str | None] = mapped_column(Text, nullable=True)
+    reason_code: Mapped[str | None] = mapped_column(Text, nullable=True)   # REASON_CODES (#2874)
     classified_by: Mapped[str | None] = mapped_column(Text, nullable=True)
     classified_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True
@@ -158,6 +173,7 @@ class CodeShape(Base, TimestampMixin):
             "status": self.status,
             "snippet_id": self.snippet_id,
             "reason": self.reason,
+            "reason_code": self.reason_code,
             "classified_by": self.classified_by,
             "classified_at": iso(self.classified_at),
             "first_seen_commit": self.first_seen_commit,
@@ -189,6 +205,8 @@ class CodeShape(Base, TimestampMixin):
             out["snippet_id"] = self.snippet_id
         if self.classified_by:
             out["by"] = self.classified_by
+        if self.reason_code:
+            out["reason_code"] = self.reason_code
         proposal = self.proposal
         if proposal:
             out["proposal"] = proposal

src/scribe/services/coverage.py

@@ -488,6 +488,7 @@ async def compute_coverage(
         # confirm, the largest derive-first groups, and what this refresh did.
         "proposed": proposals["proposed"],
         "derive_groups": proposals["derive_groups"],
+        "top_canon": proposals.get("top_canon"),
         "proposer": proposer_stats,
         # The divergence readout (#2793): button B where button A is canon,
         # and judged shapes whose bodies moved since they were judged.
@@ -645,6 +646,14 @@ def coverage_line(coverage: dict) -> str:
             standing.append(f"{n_groups} derive group{'s' if n_groups != 1 else ''}")
         if coverage.get("divergent"):
             standing.append(f"{coverage['divergent']} DIVERGENT")
+        # The next action, on the line (#2874): the canon with the biggest
+        # queue to confirm, and the widest body-identical copy to consolidate.
+        top = coverage.get("top_canon") or {}
+        if top.get("snippet_id"):
+            standing.append(f"top canon #{top['snippet_id']} ×{top.get('count', 0)}")
+        first = (coverage.get("derive_groups") or [{}])[0]
+        if first.get("label") and first.get("files"):
+            standing.append(f"top copy {first['label']} ×{first['files']} files")
         if standing:
             line += f" ({', '.join(standing)})"
         gaps = [g["dir"] for g in coverage.get("largest_gaps") or []]

src/scribe/services/knowledge.py

@@ -16,6 +16,7 @@ endorsed, so a one-off direct share has to be searched for rather than arriving
 in your ambient lists.
 """
 import json
+import re
 import logging
 
 from sqlalchemy import and_, func, or_, select
@@ -76,6 +77,10 @@ def location_matches(data: dict | None, parts: dict[str, str]) -> bool:
         if all(
             _path_matches((loc.get(key) or "").strip(), want)
             if key == "path"
+            # Repo names are recorded free-form ("Scribe" / "FabledScribe" /
+            # "fabledscribe") — case is never the distinguishing thing (#2874).
+            else (loc.get(key) or "").strip().lower() == want.lower()
+            if key == "repo"
             else (loc.get(key) or "").strip() == want
             for key, want in parts.items()
         ):
@@ -99,6 +104,11 @@ def location_jsonpath(parts: dict[str, str]) -> str:
         if key == "path":
             prefix = json.dumps(want.rstrip("/") + "/")
             filters.append(f"(@.path == {literal} || @.path starts with {prefix})")
+        elif key == "repo":
+            # Case-insensitive, anchored, regex-escaped (#2874) — mirrors the
+            # Python dialect's .lower() compare.
+            pattern = json.dumps("^" + re.escape(want) + "$")
+            filters.append(f'(@.repo like_regex {pattern} flag "i")')
         else:
             filters.append(f"@.{key} == {literal}")
     return f"$.locations[*] ? ({' && '.join(filters)})"

src/scribe/services/shape_ledger.py

@@ -30,7 +30,7 @@ from typing import Iterable, NamedTuple
 from sqlalchemy import select
 
 from scribe.models import async_session
-from scribe.models.code_shape import CodeShape, CodeShapeEvent
+from scribe.models.code_shape import REASON_CODES, CodeShape, CodeShapeEvent
 from scribe.models.base import iso
 
 logger = logging.getLogger(__name__)
@@ -183,7 +183,7 @@ def _event(row: CodeShape, event: str, at: datetime, *, commit: str = "") -> Cod
 
 async def _judge(
     session, row: CodeShape, *, status: str, snippet_id: int | None,
-    by: str | None, reason: str | None, at: datetime,
+    by: str | None, reason: str | None, at: datetime, reason_code: str | None = None,
 ) -> None:
     """Apply a judgment to a row — the ONE place a status is set — and write
     its history. Clears what a judgment settles: the standing proposal, the
@@ -194,6 +194,7 @@ async def _judge(
     row.status = status
     row.snippet_id = snippet_id if status in _NEEDS_TARGET else None
     row.reason = (reason or "").strip() or None
+    row.reason_code = (reason_code or "").strip() or None
     row.classified_by = by if status != "unclassified" else None
     row.classified_at = at if status != "unclassified" else None
     row.classified_sha = row.body_sha if status != "unclassified" else ""
@@ -314,6 +315,12 @@ def validate_classifications(items: list[dict]) -> str | None:
                 f"classifications[{i}]: status {status!r} needs a reason — "
                 "the WHY is the record (note 2786)"
             )
+        code = (item.get("reason_code") or "").strip()
+        if code and code not in REASON_CODES:
+            return (
+                f"classifications[{i}]: unknown reason_code {code!r} "
+                f"(one of: {', '.join(REASON_CODES)})"
+            )
     return None
 
 
@@ -389,6 +396,7 @@ async def classify_shapes(
                     session, row, status=status,
                     snippet_id=int(item["snippet_id"]) if status in _NEEDS_TARGET else None,
                     by=via, reason=item.get("reason"), at=now,
+                    reason_code=item.get("reason_code"),
                 )
                 classified += 1
         await session.commit()
@@ -424,6 +432,7 @@ async def classify_shapes_where(
     reason: str | None = None,
     via: str = "agent",
     include_judged: bool = False,
+    reason_code: str | None = None,
 ) -> dict:
     """The sweep form of classify_shapes (#2868): one judgment applied to
     every live row under ``path`` whose symbol matches ``pattern`` (and
@@ -443,7 +452,8 @@ async def classify_shapes_where(
     if status == "canonical":
         raise ValueError("canonical is the sync's stamp on a snippet's own location — a sweep cannot set it")
     probe = {"path": path, "symbol": "*", "status": status,
-             "snippet_id": snippet_id or 0, "reason": reason or ""}
+             "snippet_id": snippet_id or 0, "reason": reason or "",
+             "reason_code": reason_code or ""}
     error = validate_classifications([probe])
     if error:
         raise ValueError(error.replace("classifications[0]", "rule"))
@@ -465,7 +475,7 @@ async def classify_shapes_where(
             await _judge(
                 session, row, status=status,
                 snippet_id=int(snippet_id) if status in _NEEDS_TARGET else None,
-                by=via, reason=reason, at=now,
+                by=via, reason=reason, at=now, reason_code=reason_code,
             )
             judged.append(f"{row.path}::{row.symbol}")
         await session.commit()
@@ -1214,6 +1224,7 @@ def proposal_summary(rows: Iterable[CodeShape], *, top: int = 8) -> dict:
     """The readout's view of the proposer's standing: how many canon
     proposals await confirmation, and the largest derive-first groups."""
     proposed = 0
+    by_canon: dict[int, int] = {}
     groups: dict[str, dict] = {}
     files: dict[str, set[str]] = {}
     for row in rows:
@@ -1221,6 +1232,7 @@ def proposal_summary(rows: Iterable[CodeShape], *, top: int = 8) -> dict:
             continue
         if row.proposed_snippet_id is not None:
             proposed += 1
+            by_canon[row.proposed_snippet_id] = by_canon.get(row.proposed_snippet_id, 0) + 1
         elif row.proposal_group:
             dup = not row.proposal_group.startswith("name:")
             g = groups.setdefault(row.proposal_group, {
@@ -1245,7 +1257,11 @@ def proposal_summary(rows: Iterable[CodeShape], *, top: int = 8) -> dict:
         groups.values(),
         key=lambda g: (g["group"].startswith("name:"), -g["files"], -g["size"], g["group"]),
     )
-    return {"proposed": proposed, "derive_groups": ranked[:top]}
+    top_canon = None
+    if by_canon:
+        sid, n = max(by_canon.items(), key=lambda kv: (kv[1], -kv[0]))
+        top_canon = {"snippet_id": sid, "count": n}
+    return {"proposed": proposed, "derive_groups": ranked[:top], "top_canon": top_canon}
 
 
 async def confirm_proposals(

tests/test_pattern_coverage.py

@@ -497,6 +497,12 @@ def test_coverage_line_names_the_proposers_standing():
     assert "; 90 unclassified (40 proposed, 2 derive groups), largest: src" in line
     line = coverage_line({**base, "proposed": 0, "derive_groups": [{"group": "a"}]})
     assert "(1 derive group)" in line
+    # #2874: the next action on the line — biggest canon queue, widest copy.
+    line = coverage_line({
+        **base, "proposed": 40, "top_canon": {"snippet_id": 2844, "count": 78},
+        "derive_groups": [{"group": "dup:abc", "label": "closed-msg (identical body)", "files": 3}],
+    })
+    assert "top canon #2844 ×78" in line and "top copy closed-msg (identical body) ×3 files" in line
 
 
 def test_coverage_line_names_divergence_and_recheck():

tests/test_shape_ledger.py

@@ -391,6 +391,22 @@ def test_compact_row_carries_identity_standing_and_the_proposers_word_only():
         assert noisy not in compact
 
 
+def test_reason_codes_are_a_fixed_catalogue_and_validated():
+    """#2874: an optional index beside the prose reason; unknown codes are a
+    structural error (the batch applies nothing)."""
+    from scribe.models.code_shape import REASON_CODES
+    from scribe.services.shape_ledger import validate_classifications
+    assert set(REASON_CODES) == {
+        "scoped-css", "one-off-handler", "test-helper", "convention-plumbing",
+        "pure-helper", "generated", "script", "typed-record",
+    }
+    assert "reason_code" in CodeShape.__table__.c
+    ok = [{"path": "a.py", "symbol": "f", "status": "exempt", "reason": "x", "reason_code": "pure-helper"}]
+    assert validate_classifications(ok) is None
+    bad = [{"path": "a.py", "symbol": "f", "status": "exempt", "reason": "x", "reason_code": "nope"}]
+    assert "unknown reason_code" in validate_classifications(bad)
+
+
 def test_rule_matches_is_directory_glob_and_kind_aware():
     from scribe.models.code_shape import CodeShape
     from scribe.services.shape_ledger import rule_matches

tests/test_snippet_location_filter.py

@@ -56,6 +56,7 @@ def test_no_parts_matches_everything():
 def test_matches_exact_repo_path_and_symbol():
     data = _data({"repo": "Scribe", "path": "src/scribe/x.py", "symbol": "helper"})
     assert location_matches(data, {"repo": "Scribe"})
+    assert location_matches(data, {"repo": "scribe"})   # repo names: case never distinguishes (#2874)
     assert location_matches(data, {"path": "src/scribe/x.py"})
     assert location_matches(data, {"symbol": "helper"})
     assert location_matches(data, {"repo": "Scribe", "symbol": "helper"})
@@ -101,7 +102,8 @@ def test_blank_recorded_part_does_not_match_a_requested_one():
 def test_jsonpath_filters_within_one_locations_entry():
     expr = location_jsonpath({"repo": "Scribe", "symbol": "helper"})
     assert expr.startswith("$.locations[*] ? (")
-    assert '@.repo == "Scribe"' in expr
+    # repo: anchored, case-insensitive (#2874) — mirrors location_matches.
+    assert '@.repo like_regex "^Scribe$" flag "i"' in expr
     assert '@.symbol == "helper"' in expr
     assert " && " in expr
 
@@ -121,8 +123,9 @@ def test_jsonpath_quotes_values_as_json_literals():
     """A quote in a repo name must stay inside the literal, not end it."""
     nasty = 'we"ird'
     expr = location_jsonpath({"repo": nasty})
-    assert json.dumps(nasty) in expr
+    assert json.dumps("^" + nasty + "$") in expr      # the regex is a JSON literal too
     assert '\\"' in expr
+    assert json.dumps(nasty) in location_jsonpath({"symbol": nasty})
 
 
 def test_jsonpath_emits_parts_in_a_fixed_key_order():