diff --git a/contracts/cultnet/interop/write-receipt-vectors.json b/contracts/cultnet/interop/write-receipt-vectors.json
index f575398d..c0313569 100644
--- a/contracts/cultnet/interop/write-receipt-vectors.json
+++ b/contracts/cultnet/interop/write-receipt-vectors.json
@@ -75,6 +75,23 @@
         "messageId": null
       }
     },
+    {
+      "name": "error_v1_empty_schema_id_is_unreadable_and_names_the_write",
+      "messagePackHex": "86AD736368656D6156657273696F6EB063756C746E65742E6572726F722E7631A56572726F72D9216D6573736167655F696E76616C69643A20756E7265616461626C65206672616D65AB726F7574696E6748696E74C0A4636F6465AF6D6573736167655F696E76616C6964A764657461696C7384A56669656C64A76D657373616765A576616C7565C0A461734F66C0A763757272656E74C0A96D6573736167654964A57075742D31",
+      "message": {
+        "schemaVersion": "cultnet.error.v1",
+        "error": "message_invalid: unreadable frame",
+        "routingHint": null,
+        "code": "message_invalid",
+        "details": {
+          "field": "message",
+          "value": null,
+          "asOf": null,
+          "current": null
+        },
+        "messageId": "put-1"
+      }
+    },
     {
       "name": "error_v1_limit_reached",
       "messagePackHex": "86AD736368656D6156657273696F6EB063756C746E65742E6572726F722E7631A56572726F72D93B6C696D69745F726561636865643A207468652073657373696F6E27732072656D656D62657265642D7772697465206C696D69742069732066756C6CAB726F7574696E6748696E74C0A4636F6465AD6C696D69745F72656163686564A764657461696C7384A56669656C64C0A576616C7565C0A461734F66C0A763757272656E74C0A96D6573736167654964A87075742D31303235",
diff --git a/contracts/cultnet/interop/write-receipt.md b/contracts/cultnet/interop/write-receipt.md
index ce708ca6..75da775f 100644
--- a/contracts/cultnet/interop/write-receipt.md
+++ b/contracts/cultnet/interop/write-receipt.md
@@ -36,7 +36,7 @@ A connection is receipt-capable when its `cultnet.hello.v0` (sent before its fir
    - **What is remembered.** Per entry a server keeps only fixed-size digests (SHA-256) of the `messageId` and of the content hash, plus the answer (`admitted`, or the refusal's code and details). Memory per entry is bounded independent of id length and payload size. Lookup compares digests.
    - **Remembered-write limits.** The per-session table holds at most 1024 entries. A server MAY also enforce a server-wide memory budget across all sessions (reference: 32 MiB of remembered entries). A NEW write (a key not already in the table) that would exceed either bound is refused `limit_reached` for that write alone, `messageId` the write's id, `details` all null; the write is not applied and the session continues. A resend of a remembered key is still answered from the table.
    - **Limit refusals are remembered.** A `limit_reached` refusal is remembered like any other: a resend of the same id and content hash replays `limit_reached`. No slot is freed mid-session, so an id refused at a bound never becomes admitted later in that session (a server at the cap keeps the refused digest pair in a bounded refusal set of at most 1024 per session, outside the entry budget; past it, a further new write is refused `limit_reached` without being remembered, and the session refuses every id it has not seen for the rest of its life, even if a server-wide budget has since freed, so a refusal that was not remembered is never followed by an admission of the same id). The client mints a new id on a new session.
-   - **Required fields.** A put or delete whose document or `schemaId` is null or missing is refused `message_invalid` with `details.field` `"document"` or `"schemaId"` (the first missing in that order) and fixed text; the write is not applied.
+   - **Required fields.** A put or delete whose document or `schemaId` is null or missing is refused `message_invalid` with `details.field` `"document"` or `"schemaId"` (the first missing in that order) and fixed text; the write is not applied. A `schemaId` or `recordKey` that is empty or only whitespace (present but names nothing) is not "missing": the write is refused `message_invalid` exactly as a frame that does not read, with `details.field` `"message"` and the write's id (vector `error_v1_empty_schema_id_is_unreadable_and_names_the_write`), and is never applied; a server must not hand it to its store.
    - **Fixed texts.** The `error` string of these refusals is fixed, so vectors can compare it: `message_invalid: messageId exceeds 256 bytes`, `message_invalid: document is required`, `message_invalid: schemaId is required`, `message_invalid: receipt sessions require the reliable channel`, `limit_reached: the session's remembered-write limit is full`.
    - **Reliable channel only.** A write is accepted on a receipt session only on a channel that is reliable and not sequenced (reliable ordered and reliable unordered both qualify; a sequenced channel drops superseded packets, so a write on it can vanish without trace). A write arriving on any other channel is refused `message_invalid` with `details.field: "channel"` (the transport profile's word for it) and fixed text. Receipts and refusals travel the reliable channel; a write that could be lost without trace cannot be answered once.
    - Past the session (or a server's longer retention, if it keeps one) a resend is a new write.