diff --git a/crates/vectord/src/playbook_memory.rs b/crates/vectord/src/playbook_memory.rs
index 7ad6f7b..3fd22d4 100644
--- a/crates/vectord/src/playbook_memory.rs
+++ b/crates/vectord/src/playbook_memory.rs
@@ -252,11 +252,21 @@ pub struct BoostEntry {
 /// Phase 26 — what happened during an upsert. The seed endpoint
 /// returns this shape so the caller sees whether its write was a new
 /// entry, a merge, or a dedup'd no-op.
+///
+/// SHAPE NOTE: `#[serde(tag = "mode")]` requires struct-like variants —
+/// bare `Added(String)` and `Noop(String)` newtype variants would
+/// panic serialization at runtime. That bug silently 500-ed every
+/// /seed call from Phase 26 (commit 640db8c) until 2026-04-22 when the
+/// auditor's hybrid fixture surfaced it. All three variants are now
+/// struct-like, producing uniform JSON:
+///   {"mode":"added","playbook_id":"pb-..."}
+///   {"mode":"updated","playbook_id":"pb-...","merged_names":[...]}
+///   {"mode":"noop","playbook_id":"pb-..."}
 #[derive(Debug, Clone, Serialize)]
 #[serde(tag = "mode", rename_all = "lowercase")]
 pub enum UpsertOutcome {
     /// New playbook appended. Carries the new playbook_id.
-    Added(String),
+    Added { playbook_id: String },
     /// Existing same-day entry updated. Playbook_id unchanged; names
     /// merged (union, original order preserved, new names appended).
     Updated {
@@ -265,7 +275,7 @@ pub enum UpsertOutcome {
     },
     /// Identical same-day entry already exists; nothing changed.
     /// Returns the stable playbook_id so caller still has a reference.
-    Noop(String),
+    Noop { playbook_id: String },
 }
 
 /// Phase 27 — shape returned from `revise_entry`. Reports both ends of
@@ -597,7 +607,7 @@ impl PlaybookMemory {
                 drop(state);
                 self.persist().await?;
                 self.rebuild_geo_index().await;
-                Ok(UpsertOutcome::Added(pid))
+                Ok(UpsertOutcome::Added { playbook_id: pid })
             }
             Some(i) => {
                 let mut existing_names_sorted = state.entries[i].endorsed_names.clone();
@@ -605,7 +615,7 @@ impl PlaybookMemory {
                 if existing_names_sorted == new_names_sorted {
                     // NOOP — identical data, just report the existing id
                     let pid = state.entries[i].playbook_id.clone();
-                    Ok(UpsertOutcome::Noop(pid))
+                    Ok(UpsertOutcome::Noop { playbook_id: pid })
                 } else {
                     // UPDATE — merge names (union, stable order).
                     let existing = state.entries.get_mut(i).ok_or("index invalidated")?;
@@ -1600,7 +1610,7 @@ mod upsert_tests {
         let pm = PlaybookMemory::new(Arc::new(InMemory::new()));
         let e = mk("fill: Welder x2 in Nashville, TN", "2026-04-21", &["Alice Smith"]);
         match pm.upsert_entry(e).await.unwrap() {
-            UpsertOutcome::Added(_) => {}
+            UpsertOutcome::Added { .. } => {}
             other => panic!("expected Added, got {:?}", other),
         }
         assert_eq!(pm.entry_count().await, 1);
@@ -1613,7 +1623,7 @@ mod upsert_tests {
         let e2 = mk("fill: Welder x2 in Nashville, TN", "2026-04-21", &["Alice Smith", "Bob Jones"]);
         pm.upsert_entry(e1).await.unwrap();
         let outcome = pm.upsert_entry(e2).await.unwrap();
-        assert!(matches!(outcome, UpsertOutcome::Noop(_)));
+        assert!(matches!(outcome, UpsertOutcome::Noop { .. }));
         // Still exactly one entry, no duplicate from the re-seed.
         assert_eq!(pm.entry_count().await, 1);
     }
@@ -1625,7 +1635,7 @@ mod upsert_tests {
         let e2 = mk("fill: Welder x2 in Nashville, TN", "2026-04-21", &["Alice Smith", "Bob Jones"]);
         let o1 = pm.upsert_entry(e1).await.unwrap();
         let pid = match o1 {
-            UpsertOutcome::Added(p) => p,
+            UpsertOutcome::Added { playbook_id: p } => p,
             other => panic!("expected Added, got {:?}", other),
         };
         let o2 = pm.upsert_entry(e2).await.unwrap();
@@ -1646,7 +1656,7 @@ mod upsert_tests {
         let e2 = mk("fill: Welder x2 in Nashville, TN", "2026-04-22", &["Alice Smith"]);
         pm.upsert_entry(e1).await.unwrap();
         let o2 = pm.upsert_entry(e2).await.unwrap();
-        assert!(matches!(o2, UpsertOutcome::Added(_)), "different day → fresh ADD");
+        assert!(matches!(o2, UpsertOutcome::Added { .. }), "different day → fresh ADD");
         assert_eq!(pm.entry_count().await, 2);
     }
 
@@ -1659,7 +1669,7 @@ mod upsert_tests {
         // A new seed on same day should ADD, not merge into the retired one.
         let e2 = mk("fill: Welder x2 in Nashville, TN", "2026-04-21", &["Carol Davis"]);
         let o = pm.upsert_entry(e2).await.unwrap();
-        assert!(matches!(o, UpsertOutcome::Added(_)));
+        assert!(matches!(o, UpsertOutcome::Added { .. }));
         assert_eq!(pm.entry_count().await, 2);
     }
 }