diff --git a/src/scribe/services/shape_ledger.py b/src/scribe/services/shape_ledger.py
index f0ccdcf..bbe89c7 100644
--- a/src/scribe/services/shape_ledger.py
+++ b/src/scribe/services/shape_ledger.py
@@ -710,6 +710,14 @@ _DERIVE_MIN_NAME = 3
 # Semantic checks per repo per refresh — an embedding each (local fastembed),
 # bounded so a 4,000-row ledger is worked through over refreshes, not in one.
 _SEMANTIC_CAP = 150
+# The semantic basis's own floor — stricter than the write-path arm's, because
+# a code BODY against a prose-forward snippet document scores 0.68–0.75 for
+# "both are about migrations"; first live run paired every alembic
+# upgrade()/downgrade() with an unrelated canon at exactly that band.
+_SEMANTIC_FLOOR = 0.8
+# Bump when a basis's rule changes: rows remember the (body, ruleset) they
+# were examined under, so a tightened rule re-examines everything once.
+_PROPOSER_VERSION = 2
 # Signature resemblance floor, name blanked (difflib ratio) — and a length
 # floor, because `def NAME():` resembles `def NAME(x):` at 0.95 while saying
 # nothing; a family shape has parameters to resemble.
@@ -823,13 +831,16 @@ async def canon_catalog(user_id: int) -> list[Canon]:
         symbol = (fields.get("symbol") or "").strip()
         kind = snippet_kind(symbol, fields.get("language") or "")
         code = fields.get("code") or ""
-        defs = extract_definitions(code)
-        signature = ""
-        if defs:
-            own = next(
-                (d for d in defs if _norm_symbol(d.name) == _norm_symbol(symbol)), defs[0]
-            )
-            signature = own.signature
+        # The signature basis matches against the canon's OWN definition
+        # line — never against an example in its code. A snippet whose code
+        # opens with a call-site example (confirmed()'s does) would otherwise
+        # make every `async function x(): Promise<void>` resemble it.
+        own = next(
+            (d for d in extract_definitions(code)
+             if symbol and _norm_symbol(d.name) == _norm_symbol(symbol)),
+            None,
+        )
+        signature = own.signature if own else ""
         out.append(Canon(
             int(note.id), kind, symbol,
             tuple(
@@ -867,7 +878,8 @@ async def _semantic_canon(
         return None
     query = concept_query(body) or body
     hits = await semantic_search_notes(
-        user_id, query, limit=3, threshold=WRITEPATH_DEFAULT_THRESHOLD,
+        user_id, query, limit=3,
+        threshold=max(WRITEPATH_DEFAULT_THRESHOLD, _SEMANTIC_FLOOR),
         note_type="snippet", scope="browse",
     )
     for score, note in hits:
@@ -914,7 +926,8 @@ async def propose_for_repo(
             if d is None:
                 continue
             signature, body_sha, body = d[3], d[4], d[5]
-            if row.proposed_at is not None and row.proposed_sha == body_sha:
+            examined_as = f"{body_sha}@{_PROPOSER_VERSION}"
+            if row.proposed_at is not None and row.proposed_sha == examined_as:
                 continue
             examined += 1
             group = row.proposal_group  # derive grouping is reassigned below
@@ -925,7 +938,7 @@ async def propose_for_repo(
             _clear_proposal(row)
             row.proposal_group = group
             row.proposed_at = now
-            row.proposed_sha = body_sha
+            row.proposed_sha = examined_as
             if hit:
                 row.proposed_snippet_id, row.proposal_basis, row.proposal_score = hit
                 row.proposal_group = None