feat(fof-layer4): supersedes_post_id field on Post

Adds an optional supersedes_post_id pointer to Post for the
"re-issue with narrower access" path. Author publishes a new post
that references an earlier one; receivers can render "this is a
re-issued version of an earlier post" + offer to view the original.

Covered by PostId = BLAKE3(Post) — receivers can verify it wasn't
forged by anyone but the author.

#[serde(default)] for back-compat; existing posts deserialize with
None. All existing Post construction sites bulk-updated to set the
field to None.

Storage::get_post returns None for the field today; a follow-up can
add a dedicated column if/when receivers need to render the
pointer. The author-side re-issue helper that creates posts with
this field set comes in the Tauri/UI slice — the wire shape is in
place now.

148 tests pass (no regressions).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/core/src/announcement.rs

@@ -144,6 +144,7 @@ pub fn build_announcement_post(
         attachments: vec![],
         timestamp_ms,
     fof_gating: None,
+    supersedes_post_id: None,
     }
 }
 

crates/core/src/content.rs

@@ -24,6 +24,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let id1 = compute_post_id(&post);
         let id2 = compute_post_id(&post);
@@ -38,6 +39,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let post2 = Post {
             author: [1u8; 32],
@@ -45,6 +47,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         assert_ne!(compute_post_id(&post1), compute_post_id(&post2));
     }
@@ -57,6 +60,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let id = compute_post_id(&post);
         assert!(verify_post_id(&id, &post));

crates/core/src/control.rs

@@ -156,6 +156,7 @@ pub fn build_delete_control_post(
         attachments: vec![],
         timestamp_ms,
     fof_gating: None,
+    supersedes_post_id: None,
     }
 }
 
@@ -184,6 +185,7 @@ pub fn build_visibility_control_post(
         attachments: vec![],
         timestamp_ms,
     fof_gating: None,
+    supersedes_post_id: None,
     }
 }
 
@@ -215,6 +217,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let post_id = crate::content::compute_post_id(&post);
         s.store_post_with_visibility(&post_id, &post, &PostVisibility::Public).unwrap();
@@ -244,6 +247,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let post_id = crate::content::compute_post_id(&post);
         s.store_post_with_visibility(&post_id, &post, &PostVisibility::Public).unwrap();

crates/core/src/fof.rs

@@ -914,6 +914,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 3000,
             fof_gating: Some(built.gating.clone()),
+        supersedes_post_id: None,
         };
 
         // Bob's device unlocks the post via his V_me (= v_x_bob).
@@ -995,6 +996,7 @@ mod tests {
         let post = crate::types::Post {
             author: alice_id, content: "alice".into(), attachments: vec![],
             timestamp_ms: 3000, fof_gating: Some(built.gating.clone()),
+        supersedes_post_id: None,
         };
         s.store_post_with_intent(
             &post_id, &post,
@@ -1085,6 +1087,7 @@ mod tests {
         let post = crate::types::Post {
             author: alice_id, content: "alice".into(), attachments: vec![],
             timestamp_ms: 3000, fof_gating: Some(built.gating.clone()),
+        supersedes_post_id: None,
         };
         s.store_post_with_intent(
             &post_id, &post,
@@ -1186,6 +1189,7 @@ mod tests {
         let post = crate::types::Post {
             author: alice_id, content: "x".into(), attachments: vec![],
             timestamp_ms: 3000, fof_gating: Some(built.gating.clone()),
+        supersedes_post_id: None,
         };
         s.store_post_with_intent(
             &post_id, &post,
@@ -1334,6 +1338,7 @@ mod tests {
         let alice_post = crate::types::Post {
             author: alice_id, content: String::new(), attachments: vec![],
             timestamp_ms: 3000, fof_gating: Some(built.gating.clone()),
+        supersedes_post_id: None,
         };
         let bob_unlock = find_unlock_for_post(&bob_storage, &alice_post).unwrap()
             .expect("Bob can unlock");

crates/core/src/group_key_distribution.rs

@@ -62,6 +62,7 @@ pub fn build_distribution_post(
         attachments: vec![],
         timestamp_ms,
     fof_gating: None,
+    supersedes_post_id: None,
     };
     let post_id = compute_post_id(&post);
     let visibility = PostVisibility::Encrypted { recipients: wrapped_keys };
@@ -243,6 +244,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 200,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         let forged_vis = PostVisibility::Encrypted { recipients: wrapped };
 

crates/core/src/import.rs

@@ -290,6 +290,7 @@ pub async fn import_as_personas(
                     attachments: attachments.clone(),
                     timestamp_ms: ep.timestamp_ms,
                 fof_gating: None,
+                supersedes_post_id: None,
                 };
 
                 // Preserve the original visibility intent from the export.
@@ -464,6 +465,7 @@ pub async fn import_public_posts(
                     attachments: attachments.clone(),
                     timestamp_ms: ep.timestamp_ms,
                 fof_gating: None,
+                supersedes_post_id: None,
                 };
 
                 // Read blob data from archive
@@ -701,6 +703,7 @@ pub async fn merge_with_key(
                     attachments: attachments.clone(),
                     timestamp_ms: ep.timestamp_ms,
                 fof_gating: None,
+                supersedes_post_id: None,
                 };
 
                 // Read blob data from archive (may need decryption for encrypted posts)

crates/core/src/network.rs

@@ -2259,6 +2259,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms: 1000,
         fof_gating: None,
+        supersedes_post_id: None,
         }
     }
 

crates/core/src/node.rs

@@ -828,6 +828,7 @@ impl Node {
                 attachments: vec![],
                 timestamp_ms: pi.created_at,
             fof_gating: None,
+            supersedes_post_id: None,
             };
             let post_id = crate::content::compute_post_id(&post);
             {
@@ -1168,6 +1169,7 @@ impl Node {
             attachments: vec![],
             timestamp_ms: now,
             fof_gating: Some(built.gating),
+        supersedes_post_id: None,
         };
         let post_id = crate::content::compute_post_id(&post);
 
@@ -1321,6 +1323,7 @@ impl Node {
             attachments,
             timestamp_ms: now,
             fof_gating,
+            supersedes_post_id: None,
         };
 
         let post_id = compute_post_id(&post);
@@ -3345,6 +3348,7 @@ impl Node {
                     attachments: post.attachments.clone(),
                     timestamp_ms: post.timestamp_ms,
                 fof_gating: None,
+                supersedes_post_id: None,
                 };
                 let new_post_id = compute_post_id(&new_post);
 

crates/core/src/profile.rs

@@ -196,6 +196,7 @@ pub fn build_profile_post(
         attachments: vec![],
         timestamp_ms,
     fof_gating: None,
+    supersedes_post_id: None,
     }
 }
 
@@ -465,6 +466,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms,
         fof_gating: None,
+        supersedes_post_id: None,
         };
 
         // Apply. Auto-scan should fire and store the unwrapped V_me.
@@ -534,6 +536,7 @@ mod tests {
             attachments: vec![],
             timestamp_ms,
         fof_gating: None,
+        supersedes_post_id: None,
         };
         apply_profile_post_if_applicable(&s, &post, Some(&VisibilityIntent::Profile)).unwrap();
 

crates/core/src/storage.rs

@@ -966,6 +966,15 @@ impl Storage {
                 attachments,
                 timestamp_ms: row.get::<_, i64>(3)? as u64,
                 fof_gating,
+                // FoF Layer 4: supersedes_post_id is not persisted as a
+                // dedicated column today; it would arrive in the JSON
+                // form via fof_gating_json on re-issued posts. For now,
+                // get_post returns None and re-issue UX surfaces it
+                // when present in the in-memory Post (Layer 4 re-issue
+                // helper sets it inline). A follow-up can add a
+                // dedicated column if/when receivers need to render the
+                // supersedes pointer in feeds.
+                supersedes_post_id: None,
             }))
         } else {
             Ok(None)
@@ -993,6 +1002,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: row.get::<_, i64>(3)? as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             )))
@@ -1087,6 +1097,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: timestamp_ms as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             ));
@@ -1126,6 +1137,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: timestamp_ms as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             ));
@@ -1289,6 +1301,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: timestamp_ms as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             ));
@@ -1325,6 +1338,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: timestamp_ms as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             ));
@@ -3012,6 +3026,7 @@ impl Storage {
                     attachments,
                     timestamp_ms: row.get::<_, i64>(4)? as u64,
                 fof_gating: None,
+                supersedes_post_id: None,
                 },
                 visibility,
             ));
@@ -6414,6 +6429,7 @@ mod tests {
                 attachments: vec![],
                 timestamp_ms: ts,
             fof_gating: None,
+            supersedes_post_id: None,
             };
             let id = blake3::hash(&serde_json::to_vec(&post).unwrap());
             s.store_post(id.as_bytes(), &post).unwrap();

crates/core/src/types.rs

@@ -48,6 +48,13 @@ pub struct Post {
     /// t=0, not the live mutable state.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub fof_gating: Option<FoFCommentGating>,
+    /// FoF Layer 4: optional pointer to a post this one supersedes.
+    /// Used by the "re-issue with narrower access" path (advanced
+    /// rotation). Readers may display "this is a re-issued version
+    /// of an earlier post" + offer to view the original if still
+    /// cached. Covered by PostId since it's part of the signed Post.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub supersedes_post_id: Option<PostId>,
 }
 
 /// A reference to a media blob attached to a post