fix(sec): tell an attribution collision apart from a changed reconstruction

snapshot_discrepancy named the accessions but not the columns, so it could not
distinguish "our numbers moved" from "the same filing is attributed twice".
The fields were already computed for validation_json and simply dropped from
the message; they are now in it.

A difference in cik ALONE is no longer reported as a reconstruction change at
all. Every fact matched, so two tracked CIKs are claiming one filing and the
fix is the universe, not the parser: it raises accession_cik_collision naming
both CIKs and sec_cik_overrides. It also never self-heals — the losing CIK
stores no row, so _ciks_with_snapshots never sees it and it is full-history
backfilled and re-reported every run until its ticker is re-pointed or retired.

Observed 2026-08-19 for EQR: after Equity Residential renamed to Vivmark
Residential (VMRK, CIK 906107), SEC's own company_tickers.json left the old
symbol on ERP Operating LP (CIK 931182), the non-traded co-registrant of their
combined 10-Qs. Both were tracked, both reconstructed the same two filings.

The reparse path now excludes cik-only differences from its rewrite set:
rewriting one would re-stamp the filing onto the co-registrant, taking it from
the issuer that actually filed it, which no parser fix asks for.

No stored value was wrong in that incident — reports/ carries the full
reproduction for this and for the companyfacts staleness behind the gate fix.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Lo99z3jWqu9X9ueBU3Z3D

app/services/sec_fundamentals_importer.py

@@ -36,7 +36,11 @@ Guardrails (design + reviews):
   excluded from actionable setups until its filing is recovered.
 - ``promote`` inserts snapshots ``ON CONFLICT (accession) DO NOTHING`` (immutable),
   reports differing existing accessions, and applies ticker updates in the same
-  transaction.
+  transaction. A difference in ``cik`` **alone** is reported separately as an
+  ``accession_cik_collision``: every fact matched, so two tracked CIKs are
+  claiming one filing and the fix is the universe, not the parser. It never
+  self-heals on its own — the losing CIK stores no row, so it is backfilled and
+  re-reported every run until its ticker is re-pointed or retired.
 - ``reparse=True`` is the one exception to immutability, and it is deliberate:
   it restages every accession with the current parser and **rewrites** the rows
   that now reconstruct differently. Immutability protects SEC's record (one row
@@ -67,7 +71,7 @@ from app.services import sec_universe
 from app.services.data_import import STATUS_PROMOTED, ValidationResult
 from app.services.sec_client import SecClient, SecError, cik10
 from app.services.sec_facts_parser import FilingMeta, SnapshotRow
-from app.services.sec_universe import ResolvedUniverse
+from app.services.sec_universe import CIK_OVERRIDES_KEY, ResolvedUniverse
 
 logger = logging.getLogger(__name__)
 
@@ -281,7 +285,18 @@ class SecFundamentalsImporter:
                 if old is not None:
                     fields = _diff_fields(row, old)
                     if fields:
-                        staged.discrepancies.append({"accession": row.accession, "fields": fields})
+                        # Carry both CIKs. promote() reads a bare ["cik"] as an
+                        # attribution collision rather than a changed
+                        # reconstruction, which holds only because _COMPARE_COLS
+                        # spans every stored fact: a fact column added to the
+                        # model but not to _SNAPSHOT_COLS would go uncompared and
+                        # let a real difference through as a collision.
+                        staged.discrepancies.append({
+                            "accession": row.accession,
+                            "fields": fields,
+                            "cik": row.cik,
+                            "stored_cik": old.cik,
+                        })
         return staged
 
     async def _stage_issuer(
@@ -555,8 +570,15 @@ class SecFundamentalsImporter:
         inserted = 0
         updated = 0
         # Only accessions whose reconstruction actually changed are rewritten;
-        # an unchanged stored row is left completely alone.
-        changed = {d["accession"] for d in staged.discrepancies} if self.reparse else set()
+        # an unchanged stored row is left completely alone. A cik-only difference
+        # is excluded on purpose: the facts are identical there, so rewriting
+        # would re-stamp the filing onto the colliding co-registrant — taking it
+        # from the issuer that actually filed it, which no parser fix asks for.
+        changed = (
+            {d["accession"] for d in staged.discrepancies if d["fields"] != ["cik"]}
+            if self.reparse
+            else set()
+        )
         for row in staged.rows:
             if row.accession in staged.existing_accessions:
                 if row.accession in changed:
@@ -641,10 +663,51 @@ class SecFundamentalsImporter:
             if gap["accession"] not in existing_gap_accessions
         ]
 
+        # Two tracked issuers claiming one filing is not a reconstruction change:
+        # every fact matched and only the CIK stamp differs, so re-parsing or
+        # reparsing fixes nothing — the universe resolution does. It is reported
+        # separately because it also does not self-heal: the loser of the
+        # collision never stores a row, so `_ciks_with_snapshots` never sees it,
+        # and it is full-history backfilled (and re-reported) on every run until
+        # a human re-points or retires the ticker. Observed 2026-08 for EQR,
+        # which SEC's own company_tickers.json maps to ERP Operating LP, the
+        # non-traded co-registrant of the issuer now trading as VMRK.
+        collisions = [d for d in staged.discrepancies if d["fields"] == ["cik"]]
+        if collisions:
+            named = ", ".join(
+                f"{d['accession']} (stored {d['stored_cik']}, parsed {d['cik']})"
+                for d in collisions[:10]
+            )
+            db.add(SystemEvent(
+                severity="warning",
+                source="sec_facts",
+                code="accession_cik_collision",
+                message=(
+                    f"{len(collisions)} filing(s) are claimed by two tracked CIKs — "
+                    "the reconstruction is identical, only the attribution differs, "
+                    "so one of the two is a co-registrant the universe should not "
+                    f"track. Re-point or retire the ticker (see {CIK_OVERRIDES_KEY}); "
+                    f"this repeats every run until then: {named}"
+                )[:4000],
+                dedup_key=f"sec_facts:accession_cik_collision:{run_id}",
+                created_at=_now(),
+            ))
+
         # Warn (in-transaction, so it commits atomically with the promotion) when
         # any existing accession reconstructed differently — kept immutable.
-        if staged.discrepancies:
-            accns = ", ".join(d["accession"] for d in staged.discrepancies[:10])
+        reconstruction_diffs = [
+            d for d in staged.discrepancies if d["fields"] != ["cik"]
+        ]
+        if reconstruction_diffs:
+            # Name the columns, not just the accession: "differs in revenue"
+            # (our numbers moved) and "differs in period_start" (the filing was
+            # re-placed in the calendar) need different responses, and the alert
+            # is where that call gets made. The fields are already computed for
+            # validation_json — they were simply dropped from the message.
+            accns = ", ".join(
+                f"{d['accession']} ({', '.join(d['fields'])})"
+                for d in reconstruction_diffs[:10]
+            )
             disposition = (
                 f"REWRITTEN by reparse run {run_id}" if self.reparse else "kept immutable"
             )
@@ -653,7 +716,7 @@ class SecFundamentalsImporter:
                 source="sec_facts",
                 code="snapshot_reparse" if self.reparse else "snapshot_discrepancy",
                 message=(
-                    f"{len(staged.discrepancies)} stored accession(s) reconstructed "
+                    f"{len(reconstruction_diffs)} stored accession(s) reconstructed "
                     f"differently; {disposition}: {accns}"
                 )[:4000],
                 dedup_key=f"sec_facts:discrepancy:{run_id}",