diff --git a/packages/polyfill/src/surface/read-model.ts b/packages/polyfill/src/surface/read-model.ts
index e536a22..27d8541 100644
--- a/packages/polyfill/src/surface/read-model.ts
+++ b/packages/polyfill/src/surface/read-model.ts
@@ -170,12 +170,31 @@ async function readDoc(
  * isolation needs a repo per entity), but it is a recommendation about writing: the
  * read reports what is there.
  *
- * Never an anchorless union-scan over all graphs (which is O(wallet size) and wrong
- * on a shared / bloated wallet — the footgun this path exists to avoid). Each doc is
- * read with an anchored default-graph query, O(1) per doc, independent of wallet
- * size — a non-empty wallet no longer matters. Reads run in parallel via `Promise.all`.
+ * ── Why this enumerates, and why that is OURS and not the target's ────────
+ * Upstream DOES have a query that spans many documents: `resolve_target_for_sparql`
+ * (`engine/verifier/src/request_processor.rs`) accepts `UserSite` — or no target at
+ * all — and returns `Ok(None)`, which the verifier itself annotates "QUERYING UNION
+ * GRAPH". It is refused for updates (`InvalidTarget`) and allowed for reads. So
+ * "the target cannot read several documents at once" is FALSE, and this path must
+ * not be read as compensating for a missing upstream capability.
+ *
+ * What makes that union unusable HERE is our own emulation: one shared wallet holds
+ * EVERY virtual identity, so a scan over all graphs crosses identity boundaries that
+ * upstream does not have (there, a wallet is one person's). The cost argument —
+ * O(wallet size) — follows from the same artefact. Both reasons are `polyfill-era`.
+ *
+ * Each doc is therefore read with an anchored default-graph query, O(1) per doc,
+ * in parallel via `Promise.all`.
+ *
+ * OPEN, and deliberately not settled here: whether enumerating is what an
+ * application should be taught at all. Targeting `PrivateStore` is a first-class
+ * option upstream, and whether it reaches a document's CONTENTS — or only the store
+ * repo's own graph, documents being repos of their own — decides it. Until that is
+ * established, treat this shape as unconfirmed rather than as the aligned answer.
  */
 // @provenance readUnion kind=aligned level=2 ref=sdk/js/lib-wasm/src/lib.rs:sparql_query — one anchored query per document — upstream's own anchoring (`resolve_target_for_sparql`), composed client-side
+// @provenance readUnion.enumeration kind=invention level=none ref=none — upstream offers a union query over many documents (`UserSite`/no target → union graph); enumerating instead is OURS, forced by the shared wallet, and UNCONFIRMED as the shape to teach — see the docstring's open question
+// @provenance readUnion.swallow kind=invention level=none ref=none — a failing document is skipped and reads as empty; upstream has no batch read at all, so it has no counterpart for what a partial failure should do
 export async function readUnion(
   docsLike: NuriLike[],
   onUnreadable?: (doc: Nuri, error: unknown) => void,