diff --git a/pageserver/src/basebackup.rs b/pageserver/src/basebackup.rs
index 58b18dae7d..dca1510810 100644
--- a/pageserver/src/basebackup.rs
+++ b/pageserver/src/basebackup.rs
@@ -601,7 +601,7 @@ where
         // add zenith.signal file
         let mut zenith_signal = String::new();
         if self.prev_record_lsn == Lsn(0) {
-            if self.lsn == self.timeline.get_ancestor_lsn() {
+            if self.timeline.is_ancestor_lsn(self.lsn) {
                 write!(zenith_signal, "PREV LSN: none")
                     .map_err(|e| BasebackupError::Server(e.into()))?;
             } else {
diff --git a/pageserver/src/tenant/metadata.rs b/pageserver/src/tenant/metadata.rs
index 8ba0775120..fc71ea7642 100644
--- a/pageserver/src/tenant/metadata.rs
+++ b/pageserver/src/tenant/metadata.rs
@@ -214,12 +214,12 @@ impl TimelineMetadata {
         self.body.ancestor_timeline = Some(*timeline);
     }
 
-    pub fn detach_from_ancestor(&mut self, timeline: &TimelineId, ancestor_lsn: &Lsn) {
+    pub fn detach_from_ancestor(&mut self, branchpoint: &(TimelineId, Lsn)) {
         if let Some(ancestor) = self.body.ancestor_timeline {
-            assert_eq!(ancestor, *timeline);
+            assert_eq!(ancestor, branchpoint.0);
         }
         if self.body.ancestor_lsn != Lsn(0) {
-            assert_eq!(self.body.ancestor_lsn, *ancestor_lsn);
+            assert_eq!(self.body.ancestor_lsn, branchpoint.1);
         }
         self.body.ancestor_timeline = None;
         self.body.ancestor_lsn = Lsn(0);
diff --git a/pageserver/src/tenant/remote_timeline_client.rs b/pageserver/src/tenant/remote_timeline_client.rs
index bbe4e16378..9103760388 100644
--- a/pageserver/src/tenant/remote_timeline_client.rs
+++ b/pageserver/src/tenant/remote_timeline_client.rs
@@ -437,6 +437,19 @@ impl RemoteTimelineClient {
         }
     }
 
+    /// Returns true if this timeline was previously detached at this Lsn and the remote timeline
+    /// client is currently initialized.
+    pub(crate) fn is_previous_ancestor_lsn(&self, lsn: Lsn) -> bool {
+        // technically this is a dirty read, but given how timeline detach ancestor is implemented
+        // via tenant restart, the lineage has always been uploaded.
+        self.upload_queue
+            .lock()
+            .unwrap()
+            .initialized_mut()
+            .map(|uq| uq.latest_lineage.is_previous_ancestor_lsn(lsn))
+            .unwrap_or(false)
+    }
+
     fn update_remote_physical_size_gauge(&self, current_remote_index_part: Option<&IndexPart>) {
         let size: u64 = if let Some(current_remote_index_part) = current_remote_index_part {
             current_remote_index_part
@@ -628,7 +641,7 @@ impl RemoteTimelineClient {
         );
 
         let index_part = IndexPart::from(&*upload_queue);
-        let op = UploadOp::UploadMetadata(index_part, disk_consistent_lsn);
+        let op = UploadOp::UploadMetadata(Box::new(index_part), disk_consistent_lsn);
         self.metric_begin(&op);
         upload_queue.queued_operations.push_back(op);
         upload_queue.latest_files_changes_since_metadata_upload_scheduled = 0;
@@ -647,7 +660,14 @@ impl RemoteTimelineClient {
             let mut guard = self.upload_queue.lock().unwrap();
             let upload_queue = guard.initialized_mut()?;
 
+            let Some(prev) = upload_queue.latest_metadata.ancestor_timeline() else {
+                return Err(anyhow::anyhow!(
+                    "cannot reparent without a current ancestor"
+                ));
+            };
+
             upload_queue.latest_metadata.reparent(new_parent);
+            upload_queue.latest_lineage.record_previous_ancestor(&prev);
 
             self.schedule_index_upload(upload_queue);
 
@@ -670,9 +690,8 @@ impl RemoteTimelineClient {
             let mut guard = self.upload_queue.lock().unwrap();
             let upload_queue = guard.initialized_mut()?;
 
-            upload_queue
-                .latest_metadata
-                .detach_from_ancestor(&adopted.0, &adopted.1);
+            upload_queue.latest_metadata.detach_from_ancestor(&adopted);
+            upload_queue.latest_lineage.record_detaching(&adopted);
 
             for layer in layers {
                 upload_queue
@@ -1811,6 +1830,7 @@ impl RemoteTimelineClient {
                         latest_files: initialized.latest_files.clone(),
                         latest_files_changes_since_metadata_upload_scheduled: 0,
                         latest_metadata: initialized.latest_metadata.clone(),
+                        latest_lineage: initialized.latest_lineage.clone(),
                         projected_remote_consistent_lsn: None,
                         visible_remote_consistent_lsn: initialized
                             .visible_remote_consistent_lsn
diff --git a/pageserver/src/tenant/remote_timeline_client/index.rs b/pageserver/src/tenant/remote_timeline_client/index.rs
index 3e05905afa..b114d6aa10 100644
--- a/pageserver/src/tenant/remote_timeline_client/index.rs
+++ b/pageserver/src/tenant/remote_timeline_client/index.rs
@@ -6,6 +6,7 @@ use std::collections::HashMap;
 
 use chrono::NaiveDateTime;
 use serde::{Deserialize, Serialize};
+use utils::id::TimelineId;
 
 use crate::tenant::metadata::TimelineMetadata;
 use crate::tenant::storage_layer::LayerName;
@@ -84,6 +85,9 @@ pub struct IndexPart {
 
     #[serde(rename = "metadata_bytes")]
     pub metadata: TimelineMetadata,
+
+    #[serde(default)]
+    pub(crate) lineage: Lineage,
 }
 
 impl IndexPart {
@@ -96,10 +100,11 @@ impl IndexPart {
     /// - 3: no longer deserialize `timeline_layers` (serialized format is the same, but timeline_layers
     ///      is always generated from the keys of `layer_metadata`)
     /// - 4: timeline_layers is fully removed.
-    const LATEST_VERSION: usize = 4;
+    /// - 5: lineage was added
+    const LATEST_VERSION: usize = 5;
 
     // Versions we may see when reading from a bucket.
-    pub const KNOWN_VERSIONS: &'static [usize] = &[1, 2, 3, 4];
+    pub const KNOWN_VERSIONS: &'static [usize] = &[1, 2, 3, 4, 5];
 
     pub const FILE_NAME: &'static str = "index_part.json";
 
@@ -107,6 +112,7 @@ impl IndexPart {
         layers_and_metadata: &HashMap<LayerName, LayerFileMetadata>,
         disk_consistent_lsn: Lsn,
         metadata: TimelineMetadata,
+        lineage: Lineage,
     ) -> Self {
         let layer_metadata = layers_and_metadata
             .iter()
@@ -119,6 +125,7 @@ impl IndexPart {
             disk_consistent_lsn,
             metadata,
             deleted_at: None,
+            lineage,
         }
     }
 
@@ -147,6 +154,7 @@ impl IndexPart {
             &HashMap::new(),
             example_metadata.disk_consistent_lsn(),
             example_metadata,
+            Default::default(),
         )
     }
 }
@@ -155,8 +163,9 @@ impl From<&UploadQueueInitialized> for IndexPart {
     fn from(uq: &UploadQueueInitialized) -> Self {
         let disk_consistent_lsn = uq.latest_metadata.disk_consistent_lsn();
         let metadata = uq.latest_metadata.clone();
+        let lineage = uq.latest_lineage.clone();
 
-        Self::new(&uq.latest_files, disk_consistent_lsn, metadata)
+        Self::new(&uq.latest_files, disk_consistent_lsn, metadata, lineage)
     }
 }
 
@@ -184,8 +193,76 @@ impl From<&LayerFileMetadata> for IndexLayerMetadata {
     }
 }
 
+/// Limited history of earlier ancestors.
+///
+/// A timeline can have more than 1 earlier ancestor, in the rare case that it was repeatedly
+/// reparented by having an later timeline be detached from it's ancestor.
+#[derive(Debug, PartialEq, Eq, Clone, Serialize, Deserialize, Default)]
+pub(crate) struct Lineage {
+    /// Has the `reparenting_history` been truncated to [`Lineage::REMEMBER_AT_MOST`].
+    #[serde(skip_serializing_if = "is_false", default)]
+    reparenting_history_truncated: bool,
+
+    /// Earlier ancestors, truncated when [`Self::reparenting_history_truncated`]
+    ///
+    /// These are stored in case we want to support WAL based DR on the timeline. There can be many
+    /// of these and at most one [`Self::original_ancestor`]. There cannot be more reparentings
+    /// after [`Self::original_ancestor`] has been set.
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
+    reparenting_history: Vec<TimelineId>,
+
+    /// The ancestor from which this timeline has been detached from and when.
+    ///
+    /// If you are adding support for detaching from a hierarchy, consider changing the ancestry
+    /// into a `Vec<(TimelineId, Lsn)>` to be a path instead.
+    #[serde(skip_serializing_if = "Option::is_none", default)]
+    original_ancestor: Option<(TimelineId, Lsn, NaiveDateTime)>,
+}
+
+fn is_false(b: &bool) -> bool {
+    !b
+}
+
+impl Lineage {
+    const REMEMBER_AT_MOST: usize = 100;
+
+    pub(crate) fn record_previous_ancestor(&mut self, old_ancestor: &TimelineId) {
+        if self.reparenting_history.last() == Some(old_ancestor) {
+            // do not re-record it
+            return;
+        }
+
+        let drop_oldest = self.reparenting_history.len() + 1 >= Self::REMEMBER_AT_MOST;
+
+        self.reparenting_history_truncated |= drop_oldest;
+        if drop_oldest {
+            self.reparenting_history.remove(0);
+        }
+        self.reparenting_history.push(*old_ancestor);
+    }
+
+    pub(crate) fn record_detaching(&mut self, branchpoint: &(TimelineId, Lsn)) {
+        assert!(self.original_ancestor.is_none());
+
+        self.original_ancestor =
+            Some((branchpoint.0, branchpoint.1, chrono::Utc::now().naive_utc()));
+    }
+
+    /// The queried lsn is most likely the basebackup lsn, and this answers question "is it allowed
+    /// to start a read/write primary at this lsn".
+    ///
+    /// Returns true if the Lsn was previously a branch point.
+    pub(crate) fn is_previous_ancestor_lsn(&self, lsn: Lsn) -> bool {
+        self.original_ancestor
+            .as_ref()
+            .is_some_and(|(_, ancestor_lsn, _)| lsn == *ancestor_lsn)
+    }
+}
+
 #[cfg(test)]
 mod tests {
+    use std::str::FromStr;
+
     use super::*;
 
     #[test]
@@ -221,6 +298,7 @@ mod tests {
             disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
             metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
             deleted_at: None,
+            lineage: Lineage::default(),
         };
 
         let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -261,6 +339,7 @@ mod tests {
             disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
             metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
             deleted_at: None,
+            lineage: Lineage::default(),
         };
 
         let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -302,7 +381,8 @@ mod tests {
             disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
             metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
             deleted_at: Some(chrono::NaiveDateTime::parse_from_str(
-                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap())
+                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap()),
+            lineage: Lineage::default(),
         };
 
         let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
@@ -347,6 +427,7 @@ mod tests {
             ])
             .unwrap(),
             deleted_at: None,
+            lineage: Lineage::default(),
         };
 
         let empty_layers_parsed = IndexPart::from_s3_bytes(empty_layers_json.as_bytes()).unwrap();
@@ -385,11 +466,58 @@ mod tests {
             ]),
             disk_consistent_lsn: "0/16960E8".parse::<Lsn>().unwrap(),
             metadata: TimelineMetadata::from_bytes(&[113,11,159,210,0,54,0,4,0,0,0,0,1,105,96,232,1,0,0,0,0,1,105,96,112,0,0,0,0,0,0,0,0,0,0,0,0,0,1,105,96,112,0,0,0,0,1,105,96,112,0,0,0,14,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
-            deleted_at: Some(chrono::NaiveDateTime::parse_from_str(
-                "2023-07-31T09:00:00.123000000", "%Y-%m-%dT%H:%M:%S.%f").unwrap()),
+            deleted_at: Some(parse_naive_datetime("2023-07-31T09:00:00.123000000")),
+            lineage: Lineage::default(),
         };
 
         let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
         assert_eq!(part, expected);
     }
+
+    #[test]
+    fn v5_indexpart_is_parsed() {
+        let example = r#"{
+            "version":5,
+            "layer_metadata":{
+                "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF420-00000000014EF499":{"file_size":23289856,"generation":1},
+                "000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF499-00000000015A7619":{"file_size":1015808,"generation":1}},
+                "disk_consistent_lsn":"0/15A7618",
+                "metadata_bytes":[226,88,25,241,0,46,0,4,0,0,0,0,1,90,118,24,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,78,244,32,0,0,0,0,1,78,244,32,0,0,0,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0],
+                "lineage":{
+                    "original_ancestor":["e2bfd8c633d713d279e6fcd2bcc15b6d","0/15A7618","2024-05-07T18:52:36.322426563"],
+                    "reparenting_history":["e1bfd8c633d713d279e6fcd2bcc15b6d"]
+                }
+        }"#;
+
+        let expected = IndexPart {
+            version: 5,
+            layer_metadata: HashMap::from([
+                ("000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF420-00000000014EF499".parse().unwrap(), IndexLayerMetadata {
+                    file_size: 23289856,
+                    generation: Generation::new(1),
+                    shard: ShardIndex::unsharded(),
+                }),
+                ("000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000014EF499-00000000015A7619".parse().unwrap(), IndexLayerMetadata {
+                    file_size: 1015808,
+                    generation: Generation::new(1),
+                    shard: ShardIndex::unsharded(),
+                })
+            ]),
+            disk_consistent_lsn: Lsn::from_str("0/15A7618").unwrap(),
+            metadata: TimelineMetadata::from_bytes(&[226,88,25,241,0,46,0,4,0,0,0,0,1,90,118,24,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,78,244,32,0,0,0,0,1,78,244,32,0,0,0,16,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]).unwrap(),
+            deleted_at: None,
+            lineage: Lineage {
+                reparenting_history_truncated: false,
+                reparenting_history: vec![TimelineId::from_str("e1bfd8c633d713d279e6fcd2bcc15b6d").unwrap()],
+                original_ancestor: Some((TimelineId::from_str("e2bfd8c633d713d279e6fcd2bcc15b6d").unwrap(), Lsn::from_str("0/15A7618").unwrap(), parse_naive_datetime("2024-05-07T18:52:36.322426563"))),
+            },
+        };
+
+        let part = IndexPart::from_s3_bytes(example.as_bytes()).unwrap();
+        assert_eq!(part, expected);
+    }
+
+    fn parse_naive_datetime(s: &str) -> NaiveDateTime {
+        chrono::NaiveDateTime::parse_from_str(s, "%Y-%m-%dT%H:%M:%S.%f").unwrap()
+    }
 }
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 60b3873b71..505dc8c30d 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -3037,6 +3037,18 @@ impl Timeline {
 
         Some(HeatMapTimeline::new(self.timeline_id, layers))
     }
+
+    /// Returns true if the given lsn is or was an ancestor branchpoint.
+    pub(crate) fn is_ancestor_lsn(&self, lsn: Lsn) -> bool {
+        // upon timeline detach, we set the ancestor_lsn to Lsn::INVALID and the store the original
+        // branchpoint in the value in IndexPart::lineage
+        self.ancestor_lsn == lsn
+            || (self.ancestor_lsn == Lsn::INVALID
+                && self
+                    .remote_client
+                    .as_ref()
+                    .is_some_and(|rtc| rtc.is_previous_ancestor_lsn(lsn)))
+    }
 }
 
 type TraversalId = Arc<str>;
@@ -4354,7 +4366,6 @@ impl Timeline {
     /// - has an ancestor to detach from
     /// - the ancestor does not have an ancestor -- follows from the original RFC limitations, not
     /// a technical requirement
-    /// - has prev_lsn in remote storage (temporary restriction)
     ///
     /// After the operation has been started, it cannot be canceled. Upon restart it needs to be
     /// polled again until completion.
diff --git a/pageserver/src/tenant/timeline/detach_ancestor.rs b/pageserver/src/tenant/timeline/detach_ancestor.rs
index 2641bf3d13..69b82344a6 100644
--- a/pageserver/src/tenant/timeline/detach_ancestor.rs
+++ b/pageserver/src/tenant/timeline/detach_ancestor.rs
@@ -22,8 +22,6 @@ pub(crate) enum Error {
     TooManyAncestors,
     #[error("shutting down, please retry later")]
     ShuttingDown,
-    #[error("detached timeline must receive writes before the operation")]
-    DetachedTimelineNeedsWrites,
     #[error("flushing failed")]
     FlushAncestor(#[source] anyhow::Error),
     #[error("layer download failed")]
@@ -94,14 +92,6 @@ pub(super) async fn prepare(
         return Err(TooManyAncestors);
     }
 
-    if detached.get_prev_record_lsn() == Lsn::INVALID
-        || detached.disk_consistent_lsn.load() == ancestor_lsn
-    {
-        // this is to avoid a problem that after detaching we would be unable to start up the
-        // compute because of "PREV_LSN: invalid".
-        return Err(DetachedTimelineNeedsWrites);
-    }
-
     // before we acquire the gate, we must mark the ancestor as having a detach operation
     // ongoing which will block other concurrent detach operations so we don't get to ackward
     // situations where there would be two branches trying to reparent earlier branches.
diff --git a/pageserver/src/tenant/upload_queue.rs b/pageserver/src/tenant/upload_queue.rs
index 7797117e0f..a2f761fa94 100644
--- a/pageserver/src/tenant/upload_queue.rs
+++ b/pageserver/src/tenant/upload_queue.rs
@@ -3,6 +3,7 @@ use super::storage_layer::ResidentLayer;
 use crate::tenant::metadata::TimelineMetadata;
 use crate::tenant::remote_timeline_client::index::IndexPart;
 use crate::tenant::remote_timeline_client::index::LayerFileMetadata;
+use crate::tenant::remote_timeline_client::index::Lineage;
 use std::collections::{HashMap, VecDeque};
 use std::fmt::Debug;
 
@@ -56,6 +57,9 @@ pub(crate) struct UploadQueueInitialized {
     /// DANGER: do not return to outside world, e.g., safekeepers.
     pub(crate) latest_metadata: TimelineMetadata,
 
+    /// Part of the flattened "next" `index_part.json`.
+    pub(crate) latest_lineage: Lineage,
+
     /// `disk_consistent_lsn` from the last metadata file that was successfully
     /// uploaded. `Lsn(0)` if nothing was uploaded yet.
     /// Unlike `latest_files` or `latest_metadata`, this value is never ahead.
@@ -171,6 +175,7 @@ impl UploadQueue {
             latest_files: HashMap::new(),
             latest_files_changes_since_metadata_upload_scheduled: 0,
             latest_metadata: metadata.clone(),
+            latest_lineage: Lineage::default(),
             projected_remote_consistent_lsn: None,
             visible_remote_consistent_lsn: Arc::new(AtomicLsn::new(0)),
             // what follows are boring default initializations
@@ -218,6 +223,7 @@ impl UploadQueue {
             latest_files: files,
             latest_files_changes_since_metadata_upload_scheduled: 0,
             latest_metadata: index_part.metadata.clone(),
+            latest_lineage: index_part.lineage.clone(),
             projected_remote_consistent_lsn: Some(index_part.metadata.disk_consistent_lsn()),
             visible_remote_consistent_lsn: Arc::new(
                 index_part.metadata.disk_consistent_lsn().into(),
@@ -290,7 +296,7 @@ pub(crate) enum UploadOp {
     UploadLayer(ResidentLayer, LayerFileMetadata),
 
     /// Upload the metadata file
-    UploadMetadata(IndexPart, Lsn),
+    UploadMetadata(Box<IndexPart>, Lsn),
 
     /// Delete layer files
     Delete(Delete),
diff --git a/s3_scrubber/src/checks.rs b/s3_scrubber/src/checks.rs
index 68133fc0a9..dd64a0a98f 100644
--- a/s3_scrubber/src/checks.rs
+++ b/s3_scrubber/src/checks.rs
@@ -246,7 +246,7 @@ pub(crate) struct S3TimelineBlobData {
 #[derive(Debug)]
 pub(crate) enum BlobDataParseResult {
     Parsed {
-        index_part: IndexPart,
+        index_part: Box<IndexPart>,
         index_part_generation: Generation,
         s3_layers: HashSet<(LayerName, Generation)>,
     },
@@ -368,7 +368,7 @@ pub(crate) async fn list_timeline_blobs(
             Ok(index_part) => {
                 return Ok(S3TimelineBlobData {
                     blob_data: BlobDataParseResult::Parsed {
-                        index_part,
+                        index_part: Box::new(index_part),
                         index_part_generation,
                         s3_layers,
                     },
diff --git a/s3_scrubber/src/tenant_snapshot.rs b/s3_scrubber/src/tenant_snapshot.rs
index 2c93a8490a..a24a1e92ae 100644
--- a/s3_scrubber/src/tenant_snapshot.rs
+++ b/s3_scrubber/src/tenant_snapshot.rs
@@ -159,7 +159,7 @@ impl SnapshotDownloader {
     async fn download_timeline(
         &self,
         ttid: TenantShardTimelineId,
-        index_part: IndexPart,
+        index_part: Box<IndexPart>,
         index_part_generation: Generation,
         ancestor_layers: &mut HashMap<
             TenantShardTimelineId,
diff --git a/test_runner/regress/test_timeline_detach_ancestor.py b/test_runner/regress/test_timeline_detach_ancestor.py
index b8a88ca6df..075f0a6bbc 100644
--- a/test_runner/regress/test_timeline_detach_ancestor.py
+++ b/test_runner/regress/test_timeline_detach_ancestor.py
@@ -1,3 +1,4 @@
+import datetime
 import enum
 from concurrent.futures import ThreadPoolExecutor
 from queue import Empty, Queue
@@ -12,6 +13,7 @@ from fixtures.neon_fixtures import (
 )
 from fixtures.pageserver.http import HistoricLayerInfo
 from fixtures.pageserver.utils import wait_timeline_detail_404
+from fixtures.remote_storage import LocalFsStorage
 from fixtures.types import Lsn, TimelineId
 
 
@@ -56,15 +58,16 @@ SHUTDOWN_ALLOWED_ERRORS = [
 
 @pytest.mark.parametrize("branchpoint", Branchpoint.all())
 @pytest.mark.parametrize("restart_after", [True, False])
+@pytest.mark.parametrize("write_to_branch_first", [True, False])
 def test_ancestor_detach_branched_from(
-    neon_env_builder: NeonEnvBuilder, branchpoint: Branchpoint, restart_after: bool
+    neon_env_builder: NeonEnvBuilder,
+    branchpoint: Branchpoint,
+    restart_after: bool,
+    write_to_branch_first: bool,
 ):
     """
     Creates a branch relative to L0 lsn boundary according to Branchpoint. Later the timeline is detached.
     """
-    # TODO: parametrize; currently unimplemented over at pageserver
-    write_to_branch_first = True
-
     env = neon_env_builder.init_start()
 
     env.pageserver.allowed_errors.extend(SHUTDOWN_ALLOWED_ERRORS)
@@ -174,8 +177,7 @@ def test_ancestor_detach_branched_from(
     wait_timeline_detail_404(client, env.initial_tenant, env.initial_timeline, 10, 1.0)
 
 
-@pytest.mark.parametrize("restart_after", [True, False])
-def test_ancestor_detach_reparents_earlier(neon_env_builder: NeonEnvBuilder, restart_after: bool):
+def test_ancestor_detach_reparents_earlier(neon_env_builder: NeonEnvBuilder):
     """
     The case from RFC:
 
@@ -204,9 +206,6 @@ def test_ancestor_detach_reparents_earlier(neon_env_builder: NeonEnvBuilder, res
     We confirm the end result by being able to delete "old main" after deleting "after".
     """
 
-    # TODO: support not yet implemented for these
-    write_to_branch_first = True
-
     env = neon_env_builder.init_start()
 
     env.pageserver.allowed_errors.extend(SHUTDOWN_ALLOWED_ERRORS)
@@ -244,42 +243,57 @@ def test_ancestor_detach_reparents_earlier(neon_env_builder: NeonEnvBuilder, res
 
     after = env.neon_cli.create_branch("after", "main", env.initial_tenant, ancestor_start_lsn=None)
 
-    if write_to_branch_first:
-        with env.endpoints.create_start("new main", tenant_id=env.initial_tenant) as ep:
-            assert ep.safe_psql("SELECT count(*) FROM foo;")[0][0] == 8192
-            with ep.cursor() as cur:
-                cur.execute("UPDATE audit SET starts = starts + 1")
-                assert cur.rowcount == 1
-            wait_for_last_flush_lsn(env, ep, env.initial_tenant, timeline_id)
-
-        client.timeline_checkpoint(env.initial_tenant, timeline_id)
-
     all_reparented = client.detach_ancestor(env.initial_tenant, timeline_id)
     assert all_reparented == {reparented, same_branchpoint}
 
-    if restart_after:
-        env.pageserver.stop()
-        env.pageserver.start()
-
     env.pageserver.quiesce_tenants()
 
     # checking the ancestor after is much faster than waiting for the endpoint not start
     expected_result = [
         ("main", env.initial_timeline, None, 16384, 1),
         ("after", after, env.initial_timeline, 16384, 1),
-        ("new main", timeline_id, None, 8192, 2),
+        ("new main", timeline_id, None, 8192, 1),
         ("same_branchpoint", same_branchpoint, timeline_id, 8192, 1),
         ("reparented", reparented, timeline_id, 0, 1),
     ]
 
-    for _, timeline_id, expected_ancestor, _, _ in expected_result:
-        details = client.timeline_detail(env.initial_tenant, timeline_id)
+    assert isinstance(env.pageserver_remote_storage, LocalFsStorage)
+
+    for _, queried_timeline, expected_ancestor, _, _ in expected_result:
+        details = client.timeline_detail(env.initial_tenant, queried_timeline)
         ancestor_timeline_id = details["ancestor_timeline_id"]
         if expected_ancestor is None:
             assert ancestor_timeline_id is None
         else:
             assert TimelineId(ancestor_timeline_id) == expected_ancestor
 
+        index_part = env.pageserver_remote_storage.index_content(
+            env.initial_tenant, queried_timeline
+        )
+        lineage = index_part["lineage"]
+        assert lineage is not None
+
+        assert lineage.get("reparenting_history_overflown", "false") == "false"
+
+        if queried_timeline == timeline_id:
+            original_ancestor = lineage["original_ancestor"]
+            assert original_ancestor is not None
+            assert original_ancestor[0] == str(env.initial_timeline)
+            assert original_ancestor[1] == str(branchpoint_x)
+
+            # this does not contain Z in the end, so fromisoformat accepts it
+            # it is to be in line with the deletion timestamp.. well, almost.
+            when = original_ancestor[2][:26]
+            when_ts = datetime.datetime.fromisoformat(when)
+            assert when_ts < datetime.datetime.now()
+            assert len(lineage.get("reparenting_history", [])) == 0
+        elif expected_ancestor == timeline_id:
+            assert len(lineage.get("original_ancestor", [])) == 0
+            assert lineage["reparenting_history"] == [str(env.initial_timeline)]
+        else:
+            assert len(lineage.get("original_ancestor", [])) == 0
+            assert len(lineage.get("reparenting_history", [])) == 0
+
     for name, _, _, rows, starts in expected_result:
         with env.endpoints.create_start(name, tenant_id=env.initial_tenant) as ep:
             assert ep.safe_psql("SELECT count(*) FROM foo;")[0][0] == rows
@@ -293,14 +307,10 @@ def test_ancestor_detach_reparents_earlier(neon_env_builder: NeonEnvBuilder, res
     wait_timeline_detail_404(client, env.initial_tenant, env.initial_timeline, 10, 1.0)
 
 
-@pytest.mark.parametrize("restart_after", [True, False])
-def test_detached_receives_flushes_while_being_detached(
-    neon_env_builder: NeonEnvBuilder, restart_after: bool
-):
+def test_detached_receives_flushes_while_being_detached(neon_env_builder: NeonEnvBuilder):
     """
     Makes sure that the timeline is able to receive writes through-out the detach process.
     """
-    write_to_branch_first = True
 
     env = neon_env_builder.init_start()
 
@@ -330,12 +340,6 @@ def test_detached_receives_flushes_while_being_detached(
     ep = env.endpoints.create_start("new main", tenant_id=env.initial_tenant)
     assert ep.safe_psql("SELECT count(*) FROM foo;")[0][0] == rows
 
-    if write_to_branch_first:
-        rows += insert_rows(256, ep)
-        wait_for_last_flush_lsn(env, ep, env.initial_tenant, timeline_id)
-        client.timeline_checkpoint(env.initial_tenant, timeline_id)
-        log.info("completed {write_to_branch_first=}")
-
     def small_txs(ep, queue: Queue[str], barrier):
         extra_rows = 0
 
@@ -368,11 +372,6 @@ def test_detached_receives_flushes_while_being_detached(
         reparented = client.detach_ancestor(env.initial_tenant, timeline_id)
         assert len(reparented) == 0
 
-        if restart_after:
-            # ep and row production is kept alive on purpose
-            env.pageserver.stop()
-            env.pageserver.start()
-
         env.pageserver.quiesce_tenants()
 
         queue.put("done")