diff --git a/crates/huginn-mind/tests/desk_feed_fixtures.rs b/crates/huginn-mind/tests/desk_feed_fixtures.rs
index 9c6b64a..399c82b 100644
--- a/crates/huginn-mind/tests/desk_feed_fixtures.rs
+++ b/crates/huginn-mind/tests/desk_feed_fixtures.rs
@@ -11,6 +11,8 @@
 
 use std::path::PathBuf;
 
+use serde::Serialize;
+
 use cultnet_rs::{CultNetMessage, CultNetWireContract, encode_cultnet_message_to_vec, encode_frame};
 use huginn_mind::MindRefusal;
 use huginn_mind::desk_wire::{
@@ -21,6 +23,11 @@ use huginn_mind::envelope::{OperationFailure, encode_desk_failure, encode_desk_r
 use huginn_mind::eureka_pipeline::{DeskAuthority, Short, Slug};
 
 const RUNTIME: &str = "huginn-eureka";
+/// Account ids as Bifrost sends them: `UserAccount.Id` rendered lowercase D-format
+/// (`DeskEndpoints.cs` `accountId.Value.ToString("D")`; `StartupConfigurationValidator` refuses any
+/// other decider). Synthetic values.
+const READER: &str = "5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f";
+const OTHER_DECIDER: &str = "0b9d7e3a-6c21-4f58-a0d4-9e8f7a6b5c4d";
 /// A question Eureka's mind holds (asked 2026-11-11). The answers, notes and hash in `record()` are
 /// synthetic: the hash is CultLib's sample digest, not this question's.
 const FORK: &str = "eureka-substrate:question:desk-listing-authority";
@@ -32,8 +39,8 @@ fn s(text: &str) -> Short {
 fn forks(status: Option<ListStatus>, cursor: Option<u64>, limit: u8) -> DeskRequest {
     DeskRequest::Forks {
         mind: Slug("eureka".into()),
-        subject: s("7"),
-        deciders: vec![s("7"), s("12")],
+        subject: s(READER),
+        deciders: vec![s(READER), s(OTHER_DECIDER)],
         status,
         cursor: cursor.and_then(ForkCursor::new),
         limit: ForkLimit::new(limit).unwrap(),
@@ -41,7 +48,7 @@ fn forks(status: Option<ListStatus>, cursor: Option<u64>, limit: u8) -> DeskRequ
 }
 
 fn read() -> DeskRequest {
-    DeskRequest::Fork { mind: Slug("eureka".into()), subject: s("7"), deciders: vec![s("7"), s("12")], fork_id: FORK.into() }
+    DeskRequest::Fork { mind: Slug("eureka".into()), subject: s(READER), deciders: vec![s(READER), s(OTHER_DECIDER)], fork_id: FORK.into() }
 }
 
 fn list(open_count: u64, recorded_count: u64) -> DeskResponse {
@@ -93,12 +100,112 @@ fn record() -> ForkRecord {
         options_hash: "7d95fc87d532420611fe415c1def27a3447617bb68235f46e3af130aea361c48".into(),
         counted_answer_id: Some("n1".into()),
         answers: vec![
-            answer("n1", "Counted", None, "7", "The asker lists her own forks.", "2026-11-11T17:00:00Z"),
-            answer("n2", "Revision", Some("n1"), "12", "Agreed.", "2026-11-11T17:05:00Z"),
+            answer("n1", "Counted", None, READER, "The asker lists her own forks.", "2026-11-11T17:00:00Z"),
+            answer("n2", "Revision", Some("n1"), OTHER_DECIDER, "Agreed.", "2026-11-11T17:05:00Z"),
         ],
     }
 }
 
+// ---- PROPOSED reader views (ruling: the door withholds account ids from readers who are not
+// deciders, and returns counts). CultLib's card and desk_answer cannot carry this yet (card
+// `deciders` has minItems 1 and no count key; `answerer` is a required non-null id), so these are
+// fragments in the shape proposed to Libby (follow-up `cultlib-fork-card-reader-counts`), built from
+// mirror types that exist only here. They are not Huginn's output until that contract lands and
+// `cut-desk-feed-listing` builds it. ----
+
+/// The two card keys the proposal changes, as a fragment: a decider gets the ids, anyone else `[]`
+/// and the count. Not a card.
+#[derive(Serialize)]
+struct CardViewers {
+    deciders: Vec<String>,
+    decider_count: u64,
+}
+
+fn card_viewers(decider: bool) -> CardViewers {
+    let ids = vec![READER.to_string(), OTHER_DECIDER.to_string()];
+    CardViewers { decider_count: ids.len() as u64, deciders: if decider { ids } else { Vec::new() } }
+}
+
+/// `gamecult.desk_answer.v0` as proposed for a reader who is not a decider: `answerer` nil, key kept.
+#[derive(Serialize)]
+struct WithheldAnswer {
+    #[serde(rename = "schemaVersion")]
+    schema_version: AnswerSchema,
+    answer_id: String,
+    fork_id: String,
+    outcome: String,
+    of: Option<String>,
+    retracts: Option<String>,
+    code: Option<huginn_mind::desk_wire::ForkAnswerCode>,
+    options_hash: String,
+    choice: Option<String>,
+    note: Option<String>,
+    answered_at: String,
+    received_at: String,
+    claim_in_future: bool,
+    answerer: Option<String>,
+    authority: DeskAuthority,
+    request_id: String,
+}
+
+/// `gamecult.fork.record.v0` as proposed for a reader who is not a decider: every `answerer` nil and
+/// `answerer_count`, the number of distinct answerers, in their place.
+#[derive(Serialize)]
+struct WithheldRecord {
+    #[serde(rename = "schemaVersion")]
+    schema_version: RecordSchema,
+    fork_id: String,
+    options_hash: String,
+    counted_answer_id: Option<String>,
+    answerer_count: u64,
+    answers: Vec<WithheldAnswer>,
+}
+
+fn withheld(record: ForkRecord) -> WithheldRecord {
+    let mut answerers: Vec<&str> = record.answers.iter().map(|answer| answer.answerer.as_str()).collect();
+    answerers.sort_unstable();
+    answerers.dedup();
+    let answerer_count = answerers.len() as u64;
+    WithheldRecord {
+        schema_version: record.schema_version,
+        fork_id: record.fork_id,
+        options_hash: record.options_hash,
+        counted_answer_id: record.counted_answer_id,
+        answerer_count,
+        answers: record
+            .answers
+            .into_iter()
+            .map(|answer| WithheldAnswer {
+                schema_version: answer.schema_version,
+                answer_id: answer.answer_id,
+                fork_id: answer.fork_id,
+                outcome: answer.outcome,
+                of: answer.of,
+                retracts: answer.retracts,
+                code: answer.code,
+                options_hash: answer.options_hash,
+                choice: answer.choice,
+                note: answer.note,
+                answered_at: answer.answered_at,
+                received_at: answer.received_at,
+                claim_in_future: answer.claim_in_future,
+                answerer: None,
+                authority: answer.authority,
+                request_id: answer.request_id,
+            })
+            .collect(),
+    }
+}
+
+/// The proposed fragments by reader kind: (file stem, bytes).
+fn reader_views() -> Vec<(&'static str, Vec<u8>)> {
+    vec![
+        ("card-viewers-decider.synthetic", rmp_serde::to_vec_named(&card_viewers(true)).unwrap()),
+        ("card-viewers-non-decider.synthetic", rmp_serde::to_vec_named(&card_viewers(false)).unwrap()),
+        ("record-non-decider.proposed", rmp_serde::to_vec_named(&withheld(record())).unwrap()),
+    ]
+}
+
 /// The named MessagePack payload a CultNet operation message carries (base64 in the envelope).
 fn payload(message: &CultNetMessage) -> Vec<u8> {
     use base64::Engine;
@@ -170,6 +277,10 @@ fn fixtures() -> Vec<(String, Vec<u8>)> {
     let whole = rmp_serde::to_vec_named(&record()).unwrap();
     files.push(("record-whole.payload.msgpack".into(), whole.clone()));
     files.push(("record-whole.payload.hex".into(), hex(&whole).into_bytes()));
+    for (name, bytes) in reader_views() {
+        files.push((format!("{name}.payload.msgpack"), bytes.clone()));
+        files.push((format!("{name}.payload.hex"), hex(&bytes).into_bytes()));
+    }
     files
 }
 
@@ -190,3 +301,74 @@ fn desk_feed_fixtures_are_what_the_encoders_write() {
         }
     }
 }
+
+/// The one grammar for `subject`, every `deciders` entry and every `answerer`: a lowercase
+/// D-format UUID (8-4-4-4-12 lowercase hex), the grammar Huginn already names for `RequestId`
+/// (`eureka-pipeline` `uuid_text`). A Matrix id, an email or a handle never fits it.
+fn account_id(text: &str) -> bool {
+    text.len() == 36
+        && text.bytes().enumerate().all(|(at, byte)| match at {
+            8 | 13 | 18 | 23 => byte == b'-',
+            _ => matches!(byte, b'0'..=b'9' | b'a'..=b'f'),
+        })
+}
+
+/// Every account id the fixtures carry is a Bifrost account id, never a Matrix id, email or
+/// handle. The door does not refuse other shapes yet (`Short`, any 200 bytes); that refusal is owed
+/// by `cut-desk-feed-listing.r6`, and this pins the grammar it must enforce.
+#[test]
+fn every_account_id_in_the_fixtures_is_a_lowercase_d_format_uuid() {
+    for request in [forks(Some(ListStatus::Open), None, 50), read()] {
+        let subject = match &request {
+            DeskRequest::Forks { subject, .. } | DeskRequest::Fork { subject, .. } | DeskRequest::Answer { subject, .. } => subject,
+        };
+        assert!(account_id(&subject.0), "subject");
+        assert!(request.deciders().iter().all(|decider| account_id(&decider.0)), "deciders");
+    }
+    assert!(record().answers.iter().all(|answer| account_id(&answer.answerer)), "answerer");
+    for shape in [
+        "@heimdall:gamecult.org",
+        "meta@gamecult.org",
+        "heimdall",
+        "7",
+        "5F0C2B1E-8A4D-4C3B-9E7F-1A2B3C4D5E6F",
+        "{5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f}",
+        "",
+        // 36 hex digits and no dash: the length alone does not make an id.
+        "5f0c2b1e08a4d04c3b09e7f01a2b3c4d5e6f",
+        // 37 characters: a valid id with one more digit.
+        "5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f0",
+        // A dash moved off its position.
+        "5f0c2b1e8-a4d-4c3b-9e7f-1a2b3c4d5e6f",
+    ] {
+        assert!(!account_id(shape), "{shape} is not an account id");
+    }
+}
+
+fn holds(bytes: &[u8], text: &str) -> bool {
+    bytes.windows(text.len()).any(|window| window == text.as_bytes())
+}
+
+/// This test pins MIRROR TYPES ONLY (`CardViewers`, `WithheldRecord`), the shapes proposed to CultLib.
+/// It does not exercise Huginn's projection, which does not withhold ids yet. The tests on real list and
+/// read responses land with `cut-desk-feed-listing` (r6).
+///
+/// A reader who is not a decider gets counts and no account id at all: neither UUID appears
+/// anywhere in its fragments' bytes. A decider gets every id. (Proposed shapes; the build cut pins
+/// the same on Huginn's real list and read responses.)
+#[test]
+fn a_non_decider_gets_counts_and_no_ids_a_decider_gets_ids() {
+    let views = reader_views();
+    let bytes = |name: &str| views.iter().find(|(stem, _)| *stem == name).unwrap().1.clone();
+    for name in ["card-viewers-non-decider.synthetic", "record-non-decider.proposed"] {
+        let view = bytes(name);
+        assert!(!holds(&view, READER) && !holds(&view, OTHER_DECIDER), "{name} carries an account id");
+    }
+    let non_decider = card_viewers(false);
+    assert_eq!((non_decider.deciders.len(), non_decider.decider_count), (0, 2));
+    assert_eq!(withheld(record()).answerer_count, 2);
+    let decider = bytes("card-viewers-decider.synthetic");
+    assert!(holds(&decider, READER) && holds(&decider, OTHER_DECIDER));
+    let whole = rmp_serde::to_vec_named(&record()).unwrap();
+    assert!(holds(&whole, READER) && holds(&whole, OTHER_DECIDER), "a decider's record keeps the answerer ids");
+}
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/README.md b/crates/huginn-mind/tests/fixtures/desk-feed/README.md
index b018191..0525883 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/README.md
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/README.md
@@ -35,7 +35,10 @@ lands (see `docs/desk-feed-door.md`).
 | `unavailable.response` | Huginn to Bifrost | `Refused` `Unavailable` (Bifrost: 503 for this Mind) |
 | `failure.response` | Huginn to Bifrost | operation failure, `payloadSchema` `gamecult.cultnet.operation_failure.v1` (Bifrost: 503) |
 | `error.response` | Huginn to Bifrost | CultNet `Error` message, no payload (Bifrost: 503) |
-| `record-whole` | fragment | `gamecult.fork.record.v0` with a counted answer and a revision, answerer ids and notes raw, as the door sends them (Bifrost masks for a reader who is not a decider) |
+| `record-whole` | fragment | `gamecult.fork.record.v0` with a counted answer and a revision, answerer ids and notes whole: what the door sends today, and a decider's view |
+| `record-non-decider.proposed` | fragment | PROPOSED non-decider record: every `answerer` nil, `answerer_count` 2. Needs CultLib change `cultlib-fork-card-reader-counts`; not Huginn output yet |
+| `card-viewers-decider.synthetic` | fragment | SYNTHETIC: only `{deciders: [two ids], decider_count: 2}`. Not a card |
+| `card-viewers-non-decider.synthetic` | fragment | SYNTHETIC: only `{deciders: [], decider_count: 2}`. Not a card |
 
 No case carries a card (`gamecult.fork.card.v0`). The card's bytes wait on CultLib's re-pinned card
 vectors for `raised_at`, so no entry-bearing list page or read is pinned yet.
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.hex
new file mode 100644
index 0000000..1624ae5
--- /dev/null
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.hex
@@ -0,0 +1 @@
+82a8646563696465727392d92435663063326231652d386134642d346333622d396537662d316132623363346435653666d92430623964376533612d366332312d346635382d613064342d396538663761366235633464ad646563696465725f636f756e7402
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.msgpack
new file mode 100644
index 0000000..71b15b3
--- /dev/null
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-decider.synthetic.payload.msgpack
@@ -0,0 +1 @@
+‚¨deciders’Ù$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6fÙ$0b9d7e3a-6c21-4f58-a0d4-9e8f7a6b5c4d­decider_count
\ No newline at end of file
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.hex
new file mode 100644
index 0000000..29a1257
--- /dev/null
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.hex
@@ -0,0 +1 @@
+82a8646563696465727390ad646563696465725f636f756e7402
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.msgpack
new file mode 100644
index 0000000..252f158
--- /dev/null
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/card-viewers-non-decider.synthetic.payload.msgpack
@@ -0,0 +1 @@
+‚¨deciders�­decider_count
\ No newline at end of file
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.bin b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.bin
index b5c855d..87fae5a 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.bin and b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.bin differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.hex
index d0554ad..f11745c 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.frame.hex
@@ -1 +1 @@
-0000011287a96d6573736167654964a36d2d33a96f7065726174696f6ea5666f726b73a77061796c6f6164d9606761564762334a726334616b62576c755a4b5a6c64584a6c6132476e63335669616d566a644b45337147526c59326c6b5a584a7a6b7145336f6a4579706e4e30595852316336527663475675706d4e31636e4e766373436c62476c7461585141af7061796c6f6164456e636f64696e67b26d6573736167657061636b2d626173653634ad7061796c6f6164536368656d61b6687567696e6e2e6465736b5f726571756573742e7631ad736368656d6156657273696f6ebc63756c746e65742e6f7065726174696f6e5f726571756573742e7630a9736572766963654964ab687567696e6e2e6465736b
+000001a287a96d6573736167654964a36d2d33a96f7065726174696f6ea5666f726b73a77061796c6f6164d9f06761564762334a726334616b62576c755a4b5a6c64584a6c6132476e63335669616d566a644e6b6b4e575977597a4a694d5755744f4745305a433030597a4e694c546c6c4e3259744d574579596a4e6a4e4751315a545a6d7147526c59326c6b5a584a7a6b746b6b4e575977597a4a694d5755744f4745305a433030597a4e694c546c6c4e3259744d574579596a4e6a4e4751315a545a6d32535177596a6c6b4e32557a59533032597a49784c54526d4e5467745954426b4e4330355a54686d4e324532596a566a4e47536d633352686448567a704739775a57366d5933567963323979774b5673615731706441413daf7061796c6f6164456e636f64696e67b26d6573736167657061636b2d626173653634ad7061796c6f6164536368656d61b6687567696e6e2e6465736b5f726571756573742e7631ad736368656d6156657273696f6ebc63756c746e65742e6f7065726174696f6e5f726571756573742e7630a9736572766963654964ab687567696e6e2e6465736b
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.hex
index 60cb15a..804b47e 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.hex
@@ -1 +1 @@
-81a5466f726b7386a46d696e64a6657572656b61a77375626a656374a137a8646563696465727392a137a23132a6737461747573a46f70656ea6637572736f72c0a56c696d697400
+81a5466f726b7386a46d696e64a6657572656b61a77375626a656374d92435663063326231652d386134642d346333622d396537662d316132623363346435653666a8646563696465727392d92435663063326231652d386134642d346333622d396537662d316132623363346435653666d92430623964376533612d366332312d346635382d613064342d396538663761366235633464a6737461747573a46f70656ea6637572736f72c0a56c696d697400
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.msgpack
index 931ad8d..d79df5f 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.msgpack and b/crates/huginn-mind/tests/fixtures/desk-feed/list-counts.request.payload.msgpack differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.bin b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.bin
index 55963c3..f2479d5 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.bin and b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.bin differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.hex
index 74bfc3c..466d859 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.frame.hex
@@ -1 +1 @@
-0000011687a96d6573736167654964a36d2d32a96f7065726174696f6ea5666f726b73a77061796c6f6164d9646761564762334a726334616b62576c755a4b5a6c64584a6c6132476e63335669616d566a644b45337147526c59326c6b5a584a7a6b7145336f6a4579706e4e30595852316336527663475675706d4e31636e4e7663714e6a4e444b6c62476c7461585179af7061796c6f6164456e636f64696e67b26d6573736167657061636b2d626173653634ad7061796c6f6164536368656d61b6687567696e6e2e6465736b5f726571756573742e7631ad736368656d6156657273696f6ebc63756c746e65742e6f7065726174696f6e5f726571756573742e7630a9736572766963654964ab687567696e6e2e6465736b
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.hex
index cd0c5b0..4004719 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.hex
@@ -1 +1 @@
-81a5466f726b7386a46d696e64a6657572656b61a77375626a656374a137a8646563696465727392a137a23132a6737461747573a46f70656ea6637572736f72a3633432a56c696d697432
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.msgpack
index d9b0991..c0349ca 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.msgpack
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open-cursor.request.payload.msgpack
@@ -1 +1 @@
-�¥Forks†¤mind¦eureka§subject¡7¨deciders’¡7¢12¦status¤open¦cursor£c42¥limit2
\ No newline at end of file
+�¥Forks†¤mind¦eureka§subjectÙ$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f¨deciders’Ù$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6fÙ$0b9d7e3a-6c21-4f58-a0d4-9e8f7a6b5c4d¦status¤open¦cursor£c42¥limit2
\ No newline at end of file
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.bin b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.bin
index 0da51f3..8ea0611 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.bin and b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.bin differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.hex
index 304b63b..c351ca8 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.frame.hex
@@ -1 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.hex
index e8564d6..2006332 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.hex
@@ -1 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.msgpack
index 90f32b7..0b18a68 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.msgpack
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/list-open.request.payload.msgpack
@@ -1 +1 @@
-�¥Forks†¤mind¦eureka§subject¡7¨deciders’¡7¢12¦status¤open¦cursorÀ¥limit2
\ No newline at end of file
+�¥Forks†¤mind¦eureka§subjectÙ$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f¨deciders’Ù$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6fÙ$0b9d7e3a-6c21-4f58-a0d4-9e8f7a6b5c4d¦status¤open¦cursorÀ¥limit2
\ No newline at end of file
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.bin b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.bin
index 9b114db..181317a 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.bin and b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.bin differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.hex b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.hex
index 64c88a6..f581179 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.frame.hex
@@ -1 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.hex
index 68e7538..efe17b0 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.hex
@@ -1 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.msgpack
index bda8f77..27941b5 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.msgpack
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/read.request.payload.msgpack
@@ -1 +1 @@
-�¤Fork„¤mind¦eureka§subject¡7¨deciders’¡7¢12§fork_idÙ0eureka-substrate:question:desk-listing-authority
\ No newline at end of file
+�¤Fork„¤mind¦eureka§subjectÙ$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6f¨deciders’Ù$5f0c2b1e-8a4d-4c3b-9e7f-1a2b3c4d5e6fÙ$0b9d7e3a-6c21-4f58-a0d4-9e8f7a6b5c4d§fork_idÙ0eureka-substrate:question:desk-listing-authority
\ No newline at end of file
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.hex
new file mode 100644
index 0000000..4053399
--- /dev/null
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.hex
@@ -0,0 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.msgpack
new file mode 100644
index 0000000..d184479
Binary files /dev/null and b/crates/huginn-mind/tests/fixtures/desk-feed/record-non-decider.proposed.payload.msgpack differ
diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.hex b/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.hex
index ecf6f3f..aa5f793 100644
--- a/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.hex
+++ b/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.hex
@@ -1 +1 @@
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diff --git a/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.msgpack b/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.msgpack
index 2405433..1c8b4ed 100644
Binary files a/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.msgpack and b/crates/huginn-mind/tests/fixtures/desk-feed/record-whole.payload.msgpack differ
diff --git a/docs/desk-feed-door.md b/docs/desk-feed-door.md
index 8f233ec..e440feb 100644
--- a/docs/desk-feed-door.md
+++ b/docs/desk-feed-door.md
@@ -94,6 +94,45 @@ Request (`huginn.desk_request.v1`):
 Huginn keeps no copy. `subject` is the verified Bifrost account id of the reader. The reads carry
 no `authority`, and a payload that names it is refused whole.
 
+**Account ids.** `subject`, every `deciders` entry and every stored `answerer` are Bifrost account ids:
+`UserAccount.Id` in lowercase D-format, 8-4-4-4-12 lowercase hex (Bifrost renders it in
+`DeskEndpoints.cs` with `accountId.Value.ToString("D")`, and `StartupConfigurationValidator.cs`
+refuses any decider not in that form). That is the same grammar Huginn names for `RequestId`
+(`uuid_text`). These ids are opaque random UUIDs. A Matrix id, an email, a display name or any other
+handle is never one of them. Bifrost enforces the grammar; Huginn's door does not yet: it reads these
+fields as `Short` (any text up to 200 bytes) and would accept `@x:server` or an email. A subject
+is stored as `answerer` on an answer, so a wrong value would enter the mind. Refusing every other
+shape at decode is owed by `cut-desk-feed-listing.r6`. The test
+`every_account_id_in_the_fixtures_is_a_lowercase_d_format_uuid` pins the grammar. The fixtures use
+synthetic UUIDs.
+
+## Account ids by reader (planned; needs a CultLib change)
+
+A reader is a **decider** when the call's `subject` is in the call's `deciders`, compared byte for
+byte; both values are in the account-id format above. Any other reader is a non-decider.
+
+- **On `main` today**, every reader gets the ids. `card.deciders` carries the call's decider list on
+  every card, and every answer carries its `answerer` id. This is not live yet: no receiver is
+  deployed.
+- **Ruled (Persona, 2026-11-11; follow-up `chat-mind-20261111T150417226Z-t167`):** the door, not
+  Bifrost, withholds account ids from a non-decider and returns a count instead. Bifrost cannot do
+  it, because the card is opaque to it. A decider sees the ids. The superseding ruling is drafted
+  as `desk-read-visibility-withheld-ids`.
+- **CultLib cannot carry this yet.** The card has 16 required keys in closed map-mode (17 once `raised_at` lands), and
+  `deciders` must hold at least one item. `answerer` is a required, non-null id. The proposal to
+  Libby (follow-up `cultlib-fork-card-reader-counts`):
+  - the card gains a required `decider_count` (an integer). A non-decider gets `deciders: []`; a
+    decider gets the ids. The count is the same for both.
+  - `answerer` becomes nullable: nil for a non-decider, with the key kept, as `note` is stripped.
+  - the record gains a required `answerer_count`, the number of distinct answerers.
+- **Proposed fixtures**, built from mirror types that exist only in the test:
+  - `card-viewers-decider.synthetic` and `card-viewers-non-decider.synthetic` hold only the two card
+    keys the proposal changes. They are not cards.
+  - `record-non-decider.proposed` is a whole record as the proposal shapes it.
+
+  The test `a_non_decider_gets_counts_and_no_ids_a_decider_gets_ids` checks that neither account id
+  appears anywhere in a non-decider's bytes. `record-whole` is the decider's view.
+
 Response (`huginn.desk_response.v1`):
 
 | variant | meaning | Bifrost answers |
@@ -158,16 +197,16 @@ every pinned response carries no entry. The entry-bearing fixtures (an open list
 with `raised_at` as a string and as nil) are added by `cut-desk-feed-raised-at` against that
 CultLib commit.
 
-## Trust boundary: what Huginn sends raw, what Bifrost does
+## Trust boundary: what Huginn sends, what Bifrost does
 
-- Huginn sends every record whole over the peer-checked socket: every answer's `answerer` id and
-  every note, unmasked (fixture `record-whole`). The peer-uid check means only Bifrost's uid reads
-  them. A second reader of the socket would leak answerer ids and notes, so the socket must belong
-  to Bifrost's uid alone.
+- The peer-uid check is the whole authentication, so the socket must belong to Bifrost's uid alone.
+- Today Huginn sends every record whole: every `answerer` id, every note and the card's
+  `deciders` (fixture `record-whole`).
+- Once `cut-desk-feed-listing` and the CultLib change land, Huginn withholds the account ids from a
+  non-decider (above). Notes stay whole on the wire.
 - Bifrost owns three things: the per-request membership check, the `desk.read` token, and
-  masking on what the door returns. It masks answerer ids for a reader who is not a decider (X3,
-  Heimdall 2026-11-11) and strips notes (ruling `desk-read-visibility-listed`, `DeskNotes`).
-  Huginn masks nothing.
+  stripping notes for a reader who is not a decider (`DeskNotes`). It no longer masks answerer
+  ids.
 
 ## Listing: which forks a reader sees (Huginn's; NOT live, see the status above)