fix(filemeta): fence unsafe heal key components

crates/filemeta/src/metacache.rs

@@ -21,6 +21,7 @@ use arc_swap::ArcSwapOption;
 use rmp::Marker;
 use serde::{Deserialize, Serialize};
 use std::cmp::Ordering;
+use std::collections::{HashMap, HashSet};
 use std::str::from_utf8;
 use std::{
     fmt::Debug,
@@ -37,8 +38,13 @@ use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 use tokio::spawn;
 use tokio::sync::Mutex;
 use tracing::{debug, warn};
+use uuid::Uuid;
 
 const SLASH_SEPARATOR: &str = "/";
+pub const MAX_META_CACHE_HEAL_CANDIDATES: usize = 1024;
+/// Keep truncation continuations bounded while still giving the scanner a
+/// safe object-level retry for versions that did not fit in the candidate set.
+pub const MAX_META_CACHE_HEAL_TRUNCATED_OBJECTS: usize = 64;
 
 #[derive(Clone, Debug, Default)]
 pub struct MetadataResolutionParams {
@@ -66,6 +72,47 @@ pub struct MetaCacheEntry {
     pub reusable: bool,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub enum MetaCacheHealCandidateKind {
+    Object,
+    DeleteMarker,
+    UnversionedObject,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct MetaCacheHealCandidate {
+    pub object: String,
+    pub version_id: Option<Uuid>,
+    pub kind: MetaCacheHealCandidateKind,
+    /// Number of raw disk entries that carried this validated version.
+    pub replica_count: usize,
+}
+
+impl MetaCacheHealCandidate {
+    pub fn validated_version(&self) -> Option<Uuid> {
+        match self.kind {
+            MetaCacheHealCandidateKind::Object | MetaCacheHealCandidateKind::DeleteMarker => self.version_id,
+            MetaCacheHealCandidateKind::UnversionedObject => None,
+        }
+    }
+
+    pub fn is_unversioned(&self) -> bool {
+        self.kind == MetaCacheHealCandidateKind::UnversionedObject
+    }
+}
+
+#[derive(Clone, Debug, Default, PartialEq, Eq)]
+pub struct MetaCacheHealDiscovery {
+    pub candidates: Vec<MetaCacheHealCandidate>,
+    pub unverified_count: usize,
+    pub truncated: bool,
+    /// Object names whose validated version set exceeded the candidate cap.
+    /// The scanner retries these names without a version and with destructive
+    /// healing disabled; this is an explicit bounded continuation, not a
+    /// version claim.
+    pub truncated_objects: Vec<String>,
+}
+
 impl MetaCacheEntry {
     pub fn marshal_msg(&self) -> Result<Vec<u8>> {
         let mut wr = Vec::new();
@@ -370,6 +417,184 @@ impl MetaCacheEntries {
         })
     }
 
+    /// Discover validated object/delete-marker versions and safe unversioned
+    /// inspection candidates in the raw entries without applying read quorum.
+    /// This is intentionally separate from [`Self::resolve`]: a sub-quorum
+    /// version is a valid heal target even though it must not participate in
+    /// normal reads or writes.
+    ///
+    /// The validated list is bounded and deduplicated by object, version id,
+    /// and metadata kind; each candidate retains the number of raw disk
+    /// entries that carried it so callers can classify sub-quorum versions.
+    /// Entries whose xl.meta cannot be decoded are counted separately for
+    /// discovery accounting; they never become versionless destructive heal
+    /// requests and do not consume the validated quota. An
+    /// [`MetaCacheHealCandidateKind::UnversionedObject`] is always consumed by
+    /// a non-destructive scanner request.
+    pub fn discover_heal_candidates(&self, bucket: &str, max_candidates: usize) -> MetaCacheHealDiscovery {
+        let limit = max_candidates.min(MAX_META_CACHE_HEAL_CANDIDATES);
+        if limit == 0 || bucket.is_empty() {
+            return MetaCacheHealDiscovery::default();
+        }
+
+        let mut discovery = MetaCacheHealDiscovery {
+            candidates: Vec::<MetaCacheHealCandidate>::with_capacity(limit.min(self.0.len())),
+            unverified_count: 0,
+            truncated: false,
+            truncated_objects: Vec::with_capacity(MAX_META_CACHE_HEAL_TRUNCATED_OBJECTS.min(limit)),
+        };
+        let mut seen: HashMap<(String, Option<Uuid>, MetaCacheHealCandidateKind), usize> =
+            HashMap::with_capacity(limit.min(self.0.len()));
+
+        for entry in self.0.iter().flatten() {
+            if !valid_heal_candidate_name(bucket, entry) {
+                continue;
+            }
+
+            let meta = match FileMeta::load(&entry.metadata) {
+                Ok(meta) => meta,
+                Err(_) => {
+                    discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                    continue;
+                }
+            };
+            let mut entry_seen = HashSet::new();
+
+            for shallow in meta.versions {
+                let version = match shallow.parse_version_meta() {
+                    Ok(version) if version.valid() => version,
+                    Ok(_) | Err(_) => {
+                        discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                        continue;
+                    }
+                };
+                if version.free_version() {
+                    continue;
+                }
+
+                let payload_header = version.header();
+                if normalize_version_id(shallow.header.version_id) != normalize_version_id(payload_header.version_id)
+                    || shallow.header.version_type != payload_header.version_type
+                {
+                    discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                    continue;
+                }
+
+                let (kind, version_id) = match version.version_type {
+                    VersionType::Object
+                        if version.object.is_some() && version.delete_marker.is_none() && version.legacy_object.is_none() =>
+                    {
+                        match version.object.as_ref().and_then(|object| object.version_id) {
+                            Some(id) if !id.is_nil() => (MetaCacheHealCandidateKind::Object, Some(id)),
+                            Some(_) | None => (MetaCacheHealCandidateKind::UnversionedObject, None),
+                        }
+                    }
+                    VersionType::Delete
+                        if version.delete_marker.is_some() && version.object.is_none() && version.legacy_object.is_none() =>
+                    {
+                        let Some(id) = version.delete_marker.as_ref().and_then(|marker| marker.version_id) else {
+                            discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                            continue;
+                        };
+                        if id.is_nil() {
+                            discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                            continue;
+                        }
+                        (MetaCacheHealCandidateKind::DeleteMarker, Some(id))
+                    }
+                    VersionType::Legacy
+                        if version.legacy_object.is_some() && version.object.is_none() && version.delete_marker.is_none() =>
+                    {
+                        let Some(legacy) = version.legacy_object.as_ref() else {
+                            continue;
+                        };
+                        if legacy.version_id.is_empty() {
+                            (MetaCacheHealCandidateKind::UnversionedObject, None)
+                        } else {
+                            let Ok(id) = Uuid::parse_str(&legacy.version_id) else {
+                                discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                                continue;
+                            };
+                            if id.is_nil() {
+                                discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                                continue;
+                            }
+                            (MetaCacheHealCandidateKind::Object, Some(id))
+                        }
+                    }
+                    _ => {
+                        discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                        continue;
+                    }
+                };
+
+                if normalize_version_id(payload_header.version_id) != version_id {
+                    discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                    continue;
+                }
+
+                // `all_parts=true` is the trust-boundary check for versioned
+                // candidates. A null/legacy object may still need the old
+                // non-destructive inspection fallback when its part arrays
+                // are parseable but incomplete; never use that fallback for
+                // a candidate carrying a real version id.
+                let file_info = match version.clone().into_fileinfo(bucket, &entry.name, true) {
+                    Ok(file_info) => file_info,
+                    Err(_) if version_id.is_none() && matches!(kind, MetaCacheHealCandidateKind::UnversionedObject) => {
+                        discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                        match version.into_fileinfo(bucket, &entry.name, false) {
+                            Ok(file_info) => file_info,
+                            Err(_) => continue,
+                        }
+                    }
+                    Err(_) => {
+                        discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                        continue;
+                    }
+                };
+                if file_info.volume != bucket || file_info.name != entry.name {
+                    discovery.unverified_count = discovery.unverified_count.saturating_add(1);
+                    continue;
+                }
+
+                let candidate = MetaCacheHealCandidate {
+                    object: entry.name.clone(),
+                    version_id,
+                    kind,
+                    replica_count: 1,
+                };
+                let key = (candidate.object.clone(), candidate.version_id, candidate.kind.clone());
+                if entry_seen.contains(&key) {
+                    continue;
+                }
+                if let Some(index) = seen.get(&key).copied() {
+                    entry_seen.insert(key);
+                    discovery.candidates[index].replica_count = discovery.candidates[index].replica_count.saturating_add(1);
+                } else if discovery.candidates.len() >= limit {
+                    // Keep the validated candidate list bounded, but retain a
+                    // bounded object-level continuation so the scanner cannot
+                    // silently lose every version of a busy object.
+                    discovery.truncated = true;
+                    if discovery.truncated_objects.len() < MAX_META_CACHE_HEAL_TRUNCATED_OBJECTS
+                        && !discovery.truncated_objects.iter().any(|object| object == &candidate.object)
+                    {
+                        discovery.truncated_objects.push(candidate.object.clone());
+                    }
+                    // The remaining versions in this raw entry cannot add a
+                    // bounded candidate; avoid parsing a very long history
+                    // after the safe continuation has been recorded.
+                    break;
+                } else {
+                    entry_seen.insert(key.clone());
+                    seen.insert(key, discovery.candidates.len());
+                    discovery.candidates.push(candidate);
+                }
+            }
+        }
+
+        discovery
+    }
+
     fn resolve_inner(&self, mut params: MetadataResolutionParams, enforce_write_quorum: bool) -> Option<MetaCacheEntry> {
         if self.0.is_empty() {
             debug!(
@@ -546,6 +771,33 @@ impl MetaCacheEntries {
     }
 }
 
+fn valid_heal_candidate_name(bucket: &str, entry: &MetaCacheEntry) -> bool {
+    if bucket.is_empty()
+        || entry.name.is_empty()
+        || entry.is_dir()
+        || entry.name.contains('\\')
+        || entry.name.chars().any(char::is_control)
+    {
+        return false;
+    }
+
+    // Validate raw key components without normalizing them. The scanner maps
+    // accepted keys to filesystem paths later, so dot components and empty
+    // internal components must be rejected before that boundary. A final
+    // empty component is retained for valid keys ending in '/'.
+    let mut components = entry.name.split('/').peekable();
+    while let Some(component) = components.next() {
+        if component == "." || component == ".." || (component.is_empty() && components.peek().is_some()) {
+            return false;
+        }
+    }
+    true
+}
+
+fn normalize_version_id(version_id: Option<Uuid>) -> Option<Uuid> {
+    version_id.filter(|id| !id.is_nil())
+}
+
 #[derive(Debug, Default)]
 pub struct MetaCacheEntriesSortedResult {
     pub entries: Option<MetaCacheEntriesSorted>,
@@ -991,7 +1243,7 @@ impl<T: Clone + Debug + Send + Sync + 'static> Cache<T> {
 mod tests {
     use super::*;
     use crate::test_data::create_real_xlmeta;
-    use crate::{FileMetaVersion, MetaDeleteMarker, TRANSITION_COMPLETE};
+    use crate::{FileMetaVersion, MetaDeleteMarker, MetaObjectV1, MetaObjectV1Erasure, MetaObjectV1Stat, TRANSITION_COMPLETE};
     use std::collections::HashMap;
     use std::io::Cursor;
     use std::sync::{
@@ -1592,6 +1844,348 @@ mod tests {
         );
     }
 
+    #[test]
+    fn discover_heal_candidates_keeps_sub_quorum_versions_and_deduplicates() {
+        let now = OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp");
+        let entries = MetaCacheEntries(vec![
+            Some(metacache_entry_single_version(1, now, "one")),
+            Some(metacache_entry_single_version(2, now, "two")),
+            Some(metacache_entry_single_version(2, now, "two")),
+            Some(metacache_entry_single_version(3, now, "three")),
+        ]);
+
+        let discovery = entries.discover_heal_candidates("bucket", 16);
+        let ids: std::collections::HashSet<Uuid> = discovery
+            .candidates
+            .iter()
+            .filter_map(|candidate| candidate.version_id)
+            .collect();
+        assert_eq!(
+            ids,
+            [Uuid::from_u128(1), Uuid::from_u128(2), Uuid::from_u128(3)]
+                .into_iter()
+                .collect()
+        );
+        assert_eq!(discovery.candidates.len(), 3, "duplicate tied versions must be emitted once");
+        assert_eq!(
+            discovery
+                .candidates
+                .iter()
+                .find(|candidate| candidate.version_id == Some(Uuid::from_u128(2)))
+                .expect("duplicate version should be discovered")
+                .replica_count,
+            2
+        );
+    }
+
+    #[test]
+    fn discover_heal_candidates_does_not_count_duplicate_versions_within_one_entry() {
+        let now = OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp");
+        let mut meta = FileMeta::load(&metacache_entry_single_version(1, now, "duplicate").metadata)
+            .expect("duplicate fixture should decode");
+        meta.versions.push(meta.versions[0].clone());
+        let entry = MetaCacheEntry {
+            name: "object".to_string(),
+            metadata: meta.marshal_msg().expect("duplicate metadata should marshal"),
+            cached: Some(meta),
+            reusable: false,
+        };
+
+        let discovery = MetaCacheEntries(vec![Some(entry)]).discover_heal_candidates("bucket", 16);
+        let candidate = discovery
+            .candidates
+            .iter()
+            .find(|candidate| candidate.version_id == Some(Uuid::from_u128(1)))
+            .expect("duplicate fixture should be discovered");
+        assert_eq!(candidate.replica_count, 1);
+    }
+
+    #[test]
+    fn discover_heal_candidates_covers_divergent_quorum_boundaries_n2_n4_n6() {
+        let now = OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp");
+
+        for (disk_count, quorum) in [(2usize, 1usize), (4, 2), (6, 3)] {
+            let target_id = Uuid::from_u128(0x1000 + disk_count as u128);
+            for target_replicas in [quorum.saturating_sub(1), quorum, quorum + 1] {
+                let entries = (0..disk_count)
+                    .map(|disk| {
+                        let version_id = if disk < target_replicas {
+                            target_id
+                        } else {
+                            Uuid::from_u128(0x2000 + disk as u128)
+                        };
+                        Some(metacache_entry_single_version(version_id.as_u128(), now, "divergent"))
+                    })
+                    .collect();
+                let discovery = MetaCacheEntries(entries).discover_heal_candidates("bucket", 32);
+                let target = discovery
+                    .candidates
+                    .iter()
+                    .find(|candidate| candidate.version_id == Some(target_id));
+                assert_eq!(target.is_some(), target_replicas > 0, "N={disk_count}, replicas={target_replicas}");
+                if let Some(target) = target {
+                    assert_eq!(target.replica_count, target_replicas);
+                }
+            }
+        }
+    }
+
+    #[test]
+    fn discover_heal_candidates_separates_delete_markers_and_preserves_unversioned_objects() {
+        let mut marker_meta = FileMeta::new();
+        marker_meta
+            .add_version(FileInfo {
+                volume: "bucket".to_string(),
+                name: "object".to_string(),
+                version_id: Some(Uuid::from_u128(99)),
+                deleted: true,
+                mod_time: Some(OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp")),
+                ..Default::default()
+            })
+            .expect("delete marker should be added");
+        let marker = MetaCacheEntry {
+            name: "object".to_string(),
+            metadata: marker_meta.marshal_msg().expect("delete marker metadata should marshal"),
+            cached: Some(marker_meta),
+            reusable: false,
+        };
+
+        let unversioned_entry = metacache_entry_with_mod_time(
+            OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp"),
+            "unversioned",
+        );
+        let discovery = MetaCacheEntries(vec![Some(marker), Some(unversioned_entry)]).discover_heal_candidates("bucket", 16);
+        assert!(discovery.candidates.iter().any(|candidate| {
+            candidate.kind == MetaCacheHealCandidateKind::DeleteMarker && candidate.version_id == Some(Uuid::from_u128(99))
+        }));
+        assert!(discovery.candidates.iter().any(|candidate| {
+            candidate.kind == MetaCacheHealCandidateKind::UnversionedObject && candidate.version_id.is_none()
+        }));
+    }
+
+    #[test]
+    fn discover_heal_candidates_rejects_delete_markers_without_ids() {
+        let mut marker_meta = FileMeta::new();
+        marker_meta
+            .add_version(FileInfo {
+                volume: "bucket".to_string(),
+                name: "object".to_string(),
+                deleted: true,
+                mod_time: Some(OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp")),
+                ..Default::default()
+            })
+            .expect("nil delete marker should be added");
+        let discovery = MetaCacheEntries(vec![Some(MetaCacheEntry {
+            name: "object".to_string(),
+            metadata: marker_meta.marshal_msg().expect("nil marker metadata should marshal"),
+            cached: Some(marker_meta),
+            reusable: false,
+        })])
+        .discover_heal_candidates("bucket", 16);
+
+        assert!(
+            !discovery
+                .candidates
+                .iter()
+                .any(|candidate| candidate.kind == MetaCacheHealCandidateKind::DeleteMarker)
+        );
+        assert!(discovery.unverified_count >= 1);
+    }
+
+    #[test]
+    fn discover_heal_candidates_skips_free_versions() {
+        let object_id = Uuid::from_u128(100);
+        let free_id = Uuid::from_u128(101);
+        let mut meta = FileMeta::new();
+        meta.add_version(FileInfo {
+            volume: "bucket".to_string(),
+            name: "object".to_string(),
+            version_id: Some(object_id),
+            transition_status: TRANSITION_COMPLETE.to_string(),
+            transitioned_objname: "remote/object".to_string(),
+            transition_version_id: Some(Uuid::from_u128(102)),
+            transition_tier: "WARM".to_string(),
+            mod_time: Some(OffsetDateTime::now_utc()),
+            ..Default::default()
+        })
+        .expect("transitioned object should be added");
+        let mut delete = FileInfo {
+            volume: "bucket".to_string(),
+            name: "object".to_string(),
+            version_id: Some(object_id),
+            mod_time: Some(OffsetDateTime::now_utc()),
+            ..Default::default()
+        };
+        delete.set_tier_free_version_id(&free_id.to_string());
+        meta.delete_version(&delete).expect("free version should be persisted");
+
+        let discovery = MetaCacheEntries(vec![Some(MetaCacheEntry {
+            name: "object".to_string(),
+            metadata: meta.marshal_msg().expect("free version metadata should marshal"),
+            cached: Some(meta),
+            reusable: false,
+        })])
+        .discover_heal_candidates("bucket", 16);
+        assert!(discovery.candidates.is_empty());
+    }
+
+    #[test]
+    fn discover_heal_candidates_preserves_unversioned_legacy_object() {
+        let legacy = MetaObjectV1 {
+            version: "1.0.1".to_string(),
+            format: "xl".to_string(),
+            stat: MetaObjectV1Stat {
+                size: 1,
+                mod_time: Some(OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp")),
+                name: "object".to_string(),
+                ..Default::default()
+            },
+            erasure: MetaObjectV1Erasure {
+                data_blocks: 4,
+                parity_blocks: 2,
+                index: 1,
+                distribution: vec![1, 2, 3, 4, 5, 6],
+                ..Default::default()
+            },
+            ..Default::default()
+        };
+        let version = FileMetaVersion {
+            version_type: VersionType::Legacy,
+            legacy_object: Some(legacy),
+            ..Default::default()
+        };
+        let mut meta = FileMeta::new();
+        meta.versions
+            .push(FileMetaShallowVersion::try_from(version).expect("legacy metadata should marshal"));
+        let discovery = MetaCacheEntries(vec![Some(MetaCacheEntry {
+            name: "object".to_string(),
+            metadata: meta.marshal_msg().expect("legacy metadata should marshal"),
+            cached: Some(meta),
+            reusable: false,
+        })])
+        .discover_heal_candidates("bucket", 16);
+        assert!(discovery.candidates.iter().any(|candidate| {
+            candidate.kind == MetaCacheHealCandidateKind::UnversionedObject && candidate.version_id.is_none()
+        }));
+    }
+
+    #[test]
+    fn discover_heal_candidates_rejects_nil_and_malformed_metadata_and_is_bounded() {
+        let now = OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp");
+        let mut nil = metacache_entry_single_version(1, now, "nil");
+        let mut nil_meta = FileMeta::load(&nil.metadata).expect("nil fixture should decode");
+        let mut nil_version = nil_meta.versions[0]
+            .parse_version_meta()
+            .expect("nil fixture version should decode");
+        nil_version.object.as_mut().expect("object fixture").version_id = Some(Uuid::nil());
+        nil_meta.versions[0] = FileMetaShallowVersion::try_from(nil_version).expect("nil fixture should marshal");
+        nil.metadata = nil_meta.marshal_msg().expect("nil fixture metadata should marshal");
+
+        let mut mismatched = metacache_entry_single_version(2, now, "mismatched");
+        let mut mismatched_meta = FileMeta::load(&mismatched.metadata).expect("mismatched fixture should decode");
+        mismatched_meta.versions[0].header.version_id = Some(Uuid::from_u128(200));
+        mismatched.metadata = mismatched_meta.marshal_msg().expect("mismatched metadata should marshal");
+
+        let mut short_parts = metacache_entry_single_version(3, now, "short-parts");
+        let mut short_parts_meta = FileMeta::load(&short_parts.metadata).expect("short-parts fixture should decode");
+        let mut short_parts_version = short_parts_meta.versions[0]
+            .parse_version_meta()
+            .expect("short-parts fixture version should decode");
+        let object = short_parts_version.object.as_mut().expect("object fixture");
+        object.part_numbers = vec![1];
+        object.part_actual_sizes = vec![1];
+        object.part_sizes.clear();
+        short_parts_meta.versions[0] = FileMetaShallowVersion::try_from(short_parts_version).expect("short-parts should marshal");
+        short_parts.metadata = short_parts_meta.marshal_msg().expect("short-parts metadata should marshal");
+
+        let mut short_unversioned = metacache_entry_with_mod_time(now, "short-unversioned");
+        let mut short_unversioned_meta =
+            FileMeta::load(&short_unversioned.metadata).expect("short-unversioned fixture should decode");
+        let mut short_unversioned_version = short_unversioned_meta.versions[0]
+            .parse_version_meta()
+            .expect("short-unversioned version should decode");
+        let unversioned_object = short_unversioned_version.object.as_mut().expect("unversioned object fixture");
+        unversioned_object.part_numbers = vec![1];
+        unversioned_object.part_actual_sizes = vec![1];
+        unversioned_object.part_sizes.clear();
+        short_unversioned_meta.versions[0] =
+            FileMetaShallowVersion::try_from(short_unversioned_version).expect("short-unversioned should marshal");
+        short_unversioned.metadata = short_unversioned_meta
+            .marshal_msg()
+            .expect("short-unversioned metadata should marshal");
+
+        let mut malformed = nil.clone();
+        malformed.name = "malformed".to_string();
+        malformed.metadata = vec![1, 2, 3];
+
+        let entries = MetaCacheEntries(
+            std::iter::once(Some(nil))
+                .chain(std::iter::once(Some(mismatched)))
+                .chain(std::iter::once(Some(short_parts)))
+                .chain(std::iter::once(Some(short_unversioned)))
+                .chain(std::iter::once(Some(malformed)))
+                .chain((0..32).map(|id| Some(metacache_entry_single_version(id + 10, now, "bounded"))))
+                .collect(),
+        );
+        let discovery = entries.discover_heal_candidates("bucket", 5);
+        assert!(discovery.candidates.len() <= 5);
+        assert!(discovery.truncated, "bounded discovery must expose dropped candidates");
+        assert!(
+            discovery.truncated_objects.iter().any(|object| object == "object"),
+            "bounded discovery must expose an object-level safe continuation"
+        );
+        assert!(
+            !discovery
+                .candidates
+                .iter()
+                .any(|candidate| candidate.version_id == Some(Uuid::nil()))
+        );
+        assert!(
+            !discovery
+                .candidates
+                .iter()
+                .any(|candidate| candidate.version_id == Some(Uuid::from_u128(2)))
+        );
+        assert!(
+            !discovery
+                .candidates
+                .iter()
+                .any(|candidate| candidate.version_id == Some(Uuid::from_u128(3)))
+        );
+        assert!(discovery.candidates.iter().any(|candidate| {
+            candidate.kind == MetaCacheHealCandidateKind::UnversionedObject && candidate.version_id.is_none()
+        }));
+        assert!(
+            discovery.unverified_count >= 1,
+            "malformed and rejected metadata must remain observable during discovery"
+        );
+
+        for invalid_name in [
+            "../object",
+            "./object",
+            "object/../other",
+            "object//name",
+            "object\\name",
+            "object\u{0001}name",
+            "object\0name",
+        ] {
+            let mut entry = metacache_entry_single_version(400, now, invalid_name);
+            entry.name = invalid_name.to_string();
+            let discovery = MetaCacheEntries(vec![Some(entry)]).discover_heal_candidates("bucket", 5);
+            assert!(
+                discovery.candidates.is_empty(),
+                "invalid key should not become a heal candidate: {invalid_name:?}"
+            );
+        }
+
+        for valid_name in ["trailing/", "prefix/object"] {
+            let mut entry = metacache_entry_single_version(401, now, valid_name);
+            entry.name = valid_name.to_string();
+            let discovery = MetaCacheEntries(vec![Some(entry)]).discover_heal_candidates("bucket", 5);
+            assert_eq!(discovery.candidates.len(), 1, "raw S3 key should remain opaque: {valid_name:?}");
+        }
+    }
+
     #[test]
     fn resolve_rejects_partial_latest_and_returns_committed_previous_metadata() {
         let old_mod_time = OffsetDateTime::from_unix_timestamp(1_705_312_300).expect("valid timestamp");

crates/scanner/src/scanner_folder.rs

@@ -43,7 +43,10 @@ use rustfs_common::metrics::{
     UpdateCurrentPathFn, current_path_updater, global_metrics,
 };
 use rustfs_common::trace_bus::{TraceEvent, TraceFunc, TraceKind, trace_emit, trace_subscriber_count};
-use rustfs_filemeta::{MetaCacheEntries, MetaCacheEntry, MetadataResolutionParams};
+use rustfs_filemeta::{
+    MAX_META_CACHE_HEAL_CANDIDATES, MAX_META_CACHE_HEAL_TRUNCATED_OBJECTS, MetaCacheEntries, MetaCacheEntry,
+    MetaCacheHealCandidateKind,
+};
 use rustfs_utils::path::{SLASH_SEPARATOR, path_join_buf};
 use s3s::dto::{BucketLifecycleConfiguration, ObjectLockConfiguration, VersioningConfiguration};
 use time::OffsetDateTime;
@@ -96,6 +99,11 @@ const METRIC_SCANNER_EXCESS_OBJECT_VERSION_SIZE_TOTAL: &str = "rustfs_scanner_ex
 const METRIC_SCANNER_EXCESS_FOLDERS_TOTAL: &str = "rustfs_scanner_excess_folders_total";
 const METRIC_SCANNER_PENDING_HEAL_PRUNE_TOTAL: &str = "rustfs_scanner_pending_heal_prune_total";
 const METRIC_SCANNER_PENDING_HEAL_MALFORMED_TOTAL: &str = "rustfs_scanner_pending_heal_malformed_total";
+const METRIC_SCANNER_HEAL_DISCOVERY_CANDIDATES_TOTAL: &str = "rustfs_scanner_heal_discovery_candidates_total";
+const METRIC_SCANNER_HEAL_DISCOVERY_SUB_QUORUM_TOTAL: &str = "rustfs_scanner_heal_discovery_sub_quorum_total";
+const METRIC_SCANNER_HEAL_DISCOVERY_UNVERIFIED_TOTAL: &str = "rustfs_scanner_heal_discovery_unverified_total";
+const METRIC_SCANNER_HEAL_DISCOVERY_QUEUED_TOTAL: &str = "rustfs_scanner_heal_discovery_queued_total";
+const METRIC_SCANNER_HEAL_DISCOVERY_TRUNCATED_TOTAL: &str = "rustfs_scanner_heal_discovery_truncated_total";
 const MAX_PENDING_SCANNER_HEAL_RETRIES_PER_BUCKET: usize = 128;
 
 // --- scanner excess alerts as S3 notification events (rustfs/backlog#1868) --
@@ -883,7 +891,7 @@ impl FolderScanner {
         object: Option<String>,
         version_id: Option<String>,
         request: HealChannelRequest,
-    ) -> Result<(), ScannerError> {
+    ) -> Result<HealAdmissionResult, ScannerError> {
         let candidate_type = pending_scanner_heal_candidate_type(kind);
         let priority = request.priority;
         let scan_mode = request.scan_mode.unwrap_or(self.scan_mode);
@@ -911,7 +919,7 @@ impl FolderScanner {
                     error = %err,
                     "Scanner deferred heal request after channel error"
                 );
-                return Ok(());
+                return Ok(HealAdmissionResult::Full);
             }
         };
         self.update_pending_scanner_heal_after_admission(
@@ -923,7 +931,7 @@ impl FolderScanner {
             result,
         );
         if result.is_admitted() {
-            return Ok(());
+            return Ok(result);
         }
 
         record_high_priority_heal_escalation(candidate_type, priority, result);
@@ -944,7 +952,7 @@ impl FolderScanner {
             state = "high_priority_not_admitted",
             "Scanner high-priority heal admission failed"
         );
-        Ok(())
+        Ok(result)
     }
 
     pub fn set_heal_object_select(&mut self, prob: u32) {
@@ -1736,14 +1744,7 @@ impl FolderScanner {
                 break;
             }
 
-            let mut resolver = MetadataResolutionParams {
-                dir_quorum: self.disks_quorum,
-                obj_quorum: self.disks_quorum,
-                bucket: "".to_string(),
-                strict: false,
-                ..Default::default()
-            };
-
+            let mut previous_bucket = String::new();
             for name in abandoned_children {
                 if !self.should_heal().await {
                     break;
@@ -1751,7 +1752,7 @@ impl FolderScanner {
 
                 let (bucket, prefix) = path2_bucket_object(name.as_str());
 
-                if bucket != resolver.bucket {
+                if bucket != previous_bucket {
                     self.send_required_scanner_heal_request(
                         PendingScannerHealKind::Bucket,
                         bucket.clone(),
@@ -1760,10 +1761,9 @@ impl FolderScanner {
                         build_bucket_heal_request(bucket.clone(), HealChannelPriority::High),
                     )
                     .await?;
+                    previous_bucket = bucket.clone();
                 }
 
-                resolver.bucket = bucket.clone();
-
                 let child_ctx = ctx.child_token();
 
                 let (agreed_tx, mut agreed_rx) = mpsc::channel::<String>(1);
@@ -1880,6 +1880,8 @@ impl FolderScanner {
                 let mut agreed_closed = false;
                 let mut partial_closed = false;
                 let mut finished_closed = false;
+                let mut seen_heal_candidates: HashSet<(String, Option<String>, MetaCacheHealCandidateKind)> = HashSet::new();
+                let mut seen_truncated_objects: HashSet<String> = HashSet::new();
 
                 loop {
                     if agreed_closed && partial_closed && finished_closed {
@@ -1904,65 +1906,117 @@ impl FolderScanner {
                                 break;
                             }
 
-                            let Some(entry) = resolve_object_heal_entry(&entries, resolver.clone()) else {
-                                continue;
-                            };
-
-                            (self.update_current_path)(&entry.name).await;
-
-                            if entry.is_dir() {
-                                continue;
+                            let discovery = entries.discover_heal_candidates(&bucket, MAX_META_CACHE_HEAL_CANDIDATES);
+                            counter!(METRIC_SCANNER_HEAL_DISCOVERY_CANDIDATES_TOTAL)
+                                .increment(u64::try_from(discovery.candidates.len()).unwrap_or(u64::MAX));
+                            counter!(METRIC_SCANNER_HEAL_DISCOVERY_SUB_QUORUM_TOTAL).increment(
+                                u64::try_from(
+                                    discovery
+                                        .candidates
+                                        .iter()
+                                        .filter(|candidate| candidate.replica_count < disks_quorum)
+                                        .count(),
+                                )
+                                .unwrap_or(u64::MAX),
+                            );
+                            counter!(METRIC_SCANNER_HEAL_DISCOVERY_UNVERIFIED_TOTAL).increment(
+                                u64::try_from(discovery.unverified_count).unwrap_or(u64::MAX),
+                            );
+                            if discovery.truncated {
+                                counter!(METRIC_SCANNER_HEAL_DISCOVERY_TRUNCATED_TOTAL).increment(1);
                             }
 
-                            let fivs = match entry.file_info_versions(&bucket) {
-                                Ok(fivs) => fivs,
-                                Err(e) => {
-                                    error!(
-                                        target: "rustfs::scanner::folder",
-                                        event = EVENT_SCANNER_FOLDER_STATE,
-                                        component = LOG_COMPONENT_SCANNER,
-                                        subsystem = LOG_SUBSYSTEM_FOLDER,
-                                        bucket = %bucket,
-                                        entry = %entry.name,
-                                        state = "file_info_versions_failed",
-                                        error = %e,
-                                        "Scanner list_path_raw failed to resolve file versions"
-                                    );
-                                    self.send_required_scanner_heal_request(
-                                        PendingScannerHealKind::Object,
-                                        bucket.clone(),
-                                        Some(entry.name.clone()),
-                                        None,
-                                        build_object_heal_request(
-                                            bucket.clone(),
-                                            entry.name.clone(),
-                                            None,
-                                            self.scan_mode,
-                                            HealChannelPriority::High,
-                                        ),
-                                    )
-                                    .await?;
-                                    found_objects = true;
+                            for candidate in discovery.candidates {
+                                let sub_quorum_candidate = candidate.replica_count < disks_quorum;
+                                let version_id = candidate.validated_version().map(|id| id.to_string());
+                                let identity = (candidate.object.clone(), version_id.clone(), candidate.kind.clone());
+                                if seen_heal_candidates.len() >= MAX_META_CACHE_HEAL_CANDIDATES
+                                    && !seen_heal_candidates.contains(&identity)
+                                {
                                     continue;
                                 }
-                            };
-
-                            for fiv in fivs.versions {
-                                let version_id = fiv.version_id.and_then(|v| if v.is_nil() { None } else { Some(v.to_string()) });
-                                self.send_required_scanner_heal_request(
-                                    PendingScannerHealKind::Object,
-                                    bucket.clone(),
-                                    Some(entry.name.clone()),
-                                    version_id.clone(),
-                                    build_object_heal_request(
+                                if !seen_heal_candidates.insert(identity) {
+                                    continue;
+                                }
+                                let request = if candidate.is_unversioned() {
+                                    build_non_destructive_object_heal_request(
                                         bucket.clone(),
-                                        entry.name.clone(),
-                                        version_id,
+                                        candidate.object.clone(),
                                         self.scan_mode,
                                         HealChannelPriority::High,
-                                    ),
+                                    )
+                                } else {
+                                    build_object_heal_request(
+                                        bucket.clone(),
+                                        candidate.object.clone(),
+                                        version_id.clone(),
+                                        self.scan_mode,
+                                        HealChannelPriority::High,
+                                    )
+                                };
+                                (self.update_current_path)(&candidate.object).await;
+                                let admission = self.send_required_scanner_heal_request(
+                                    PendingScannerHealKind::Object,
+                                    bucket.clone(),
+                                    Some(candidate.object.clone()),
+                                    version_id.clone(),
+                                    request,
                                 )
                                 .await?;
+                                if admission.is_admitted() {
+                                    counter!(METRIC_SCANNER_HEAL_DISCOVERY_QUEUED_TOTAL).increment(1);
+                                } else if sub_quorum_candidate {
+                                    self.mark_pending_scanner_heal_reason(
+                                        PendingScannerHealKind::Object,
+                                        &bucket,
+                                        Some(&candidate.object),
+                                        version_id.as_deref(),
+                                        "sub_quorum_metadata",
+                                    );
+                                }
+                                found_objects = true;
+                            }
+
+                            // A bounded candidate union may overflow for an
+                            // object with a very long version history. Keep
+                            // that overflow explicit and issue one safe,
+                            // versionless inspection request per object so
+                            // the dropped versions are not silently treated
+                            // as absent. This continuation is deliberately
+                            // outside the versioned candidate cap and always
+                            // disables destructive cleanup.
+                            for object in discovery.truncated_objects {
+                                if seen_truncated_objects.len() >= MAX_META_CACHE_HEAL_TRUNCATED_OBJECTS
+                                    && !seen_truncated_objects.contains(&object)
+                                {
+                                    continue;
+                                }
+                                if !seen_truncated_objects.insert(object.clone()) {
+                                    continue;
+                                }
+                                let identity = (object.clone(), None, MetaCacheHealCandidateKind::UnversionedObject);
+                                if !seen_heal_candidates.insert(identity) {
+                                    continue;
+                                }
+                                let request = build_non_destructive_object_heal_request(
+                                    bucket.clone(),
+                                    object.clone(),
+                                    self.scan_mode,
+                                    HealChannelPriority::High,
+                                );
+                                (self.update_current_path)(&object).await;
+                                let admission = self
+                                    .send_required_scanner_heal_request(
+                                        PendingScannerHealKind::Object,
+                                        bucket.clone(),
+                                        Some(object.clone()),
+                                        None,
+                                        request,
+                                    )
+                                    .await?;
+                                if admission.is_admitted() {
+                                    counter!(METRIC_SCANNER_HEAL_DISCOVERY_QUEUED_TOTAL).increment(1);
+                                }
                                 found_objects = true;
                             }
 

crates/scanner/src/scanner_folder/item_actions.rs

@@ -13,6 +13,8 @@
 // limitations under the License.
 /// Per-object scan actions: ScannerItem, the get-size failure policy, and the heal/ILM admission helpers.
 use super::*;
+#[cfg(test)]
+use rustfs_filemeta::MetadataResolutionParams;
 
 /// Cached folder information for scanning
 #[derive(Clone, Debug)]
@@ -88,6 +90,22 @@ pub(super) fn build_object_heal_request(
     }
 }
 
+/// Build the versionless inspection request used when discovery cannot prove
+/// a destructive version identity (for example an unversioned object or a
+/// bounded candidate overflow). The explicit flag is the fail-closed safety
+/// boundary; callers must not reconstruct it with the destructive default.
+pub(super) fn build_non_destructive_object_heal_request(
+    bucket: String,
+    object: String,
+    scan_mode: HealScanMode,
+    priority: HealChannelPriority,
+) -> HealChannelRequest {
+    let mut request = build_object_heal_request(bucket, object, None, scan_mode, priority);
+    request.remove_corrupted = Some(false);
+    request
+}
+
+#[cfg(test)]
 pub(super) fn resolve_object_heal_entry(
     entries: &MetaCacheEntries,
     resolver: MetadataResolutionParams,

crates/scanner/src/scanner_folder/ledger.rs

@@ -105,6 +105,29 @@ impl FolderScanner {
         }
     }
 
+    /// Preserve the discovery reason when a candidate could not be admitted
+    /// immediately. The existing string field is intentionally reused so the
+    /// scanner's map-encoded cache schema stays backward compatible.
+    pub(super) fn mark_pending_scanner_heal_reason(
+        &mut self,
+        kind: PendingScannerHealKind,
+        bucket: &str,
+        object: Option<&str>,
+        version_id: Option<&str>,
+        reason: &str,
+    ) {
+        if let Some(entry) = self
+            .new_cache
+            .info
+            .pending_heals
+            .iter_mut()
+            .find(|entry| pending_scanner_heal_matches(entry, kind, bucket, object, version_id))
+        {
+            entry.last_admission_reason = reason.to_string();
+            self.sync_pending_heals();
+        }
+    }
+
     pub(super) fn prune_pending_scanner_heals(&mut self) {
         let now = Self::now_secs();
         let before_expiry = self.new_cache.info.pending_heals.len();
@@ -305,13 +328,22 @@ pub(super) fn build_pending_scanner_heal_request(entry: &PendingScannerHeal) ->
     match entry.kind {
         PendingScannerHealKind::Bucket => Some(build_bucket_heal_request(entry.bucket.clone(), HealChannelPriority::High)),
         PendingScannerHealKind::Object => entry.object.as_ref().map(|object| {
-            build_object_heal_request(
-                entry.bucket.clone(),
-                object.clone(),
-                entry.version_id.clone(),
-                entry.scan_mode,
-                HealChannelPriority::High,
-            )
+            if entry.version_id.is_none() {
+                build_non_destructive_object_heal_request(
+                    entry.bucket.clone(),
+                    object.clone(),
+                    entry.scan_mode,
+                    HealChannelPriority::High,
+                )
+            } else {
+                build_object_heal_request(
+                    entry.bucket.clone(),
+                    object.clone(),
+                    entry.version_id.clone(),
+                    entry.scan_mode,
+                    HealChannelPriority::High,
+                )
+            }
         }),
     }
 }

crates/scanner/src/scanner_folder/tests.rs

@@ -17,7 +17,7 @@ use crate::SCANNER_SLEEPER;
 use super::*;
 use crate::storage_api::VersionPurgeStatusType;
 use crate::{DiskOption, Endpoint, STORAGE_FORMAT_FILE, TierStats, new_disk, storageclass};
-use rustfs_filemeta::{FileInfo, FileMeta};
+use rustfs_filemeta::{FileInfo, FileMeta, MetadataResolutionParams};
 use std::io::Write;
 #[cfg(unix)]
 use std::os::unix::fs::{PermissionsExt, symlink};
@@ -982,6 +982,21 @@ fn test_build_object_heal_request_omits_nil_version_id() {
     assert_eq!(request.recreate_missing, Some(false));
 }
 
+#[test]
+fn test_build_non_destructive_object_heal_request_disables_removal() {
+    let request = build_non_destructive_object_heal_request(
+        "bucket".to_string(),
+        "path/to/object".to_string(),
+        HealScanMode::Deep,
+        HealChannelPriority::High,
+    );
+
+    assert_eq!(request.object_version_id, None);
+    assert_eq!(request.remove_corrupted, Some(false));
+    assert_eq!(request.recreate_missing, Some(false));
+    assert_eq!(request.source, HealRequestSource::Scanner);
+}
+
 #[test]
 fn test_build_bucket_heal_request_disables_recreate_for_scanner() {
     let request = build_bucket_heal_request("bucket".to_string(), HealChannelPriority::Low);
@@ -1121,6 +1136,42 @@ fn test_pending_heal_reconstructs_object_request_with_version() {
     assert_eq!(request.source, HealRequestSource::Scanner);
 }
 
+#[test]
+fn test_pending_heal_reconstructs_unversioned_request_without_removal() {
+    let pending = pending_heal(PendingScannerHealKind::Object, "bucket", Some("object"), None, 1, 1);
+
+    let request = build_pending_scanner_heal_request(&pending).expect("unversioned object request should rebuild");
+
+    assert!(request.object_version_id.is_none());
+    assert_eq!(request.remove_corrupted, Some(false));
+    assert_eq!(request.recreate_missing, Some(false));
+}
+
+#[tokio::test]
+async fn test_pending_heal_reason_preserves_sub_quorum_discovery() {
+    let (mut scanner, temp_dir) = build_test_scanner().await;
+    let _guard = TestGuard::new(u64::MAX, usize::MAX, &mut scanner, temp_dir);
+
+    scanner.update_pending_scanner_heal_after_admission(
+        PendingScannerHealKind::Object,
+        "bucket",
+        Some("object"),
+        Some("version-a"),
+        HealScanMode::Deep,
+        HealAdmissionResult::Full,
+    );
+    scanner.mark_pending_scanner_heal_reason(
+        PendingScannerHealKind::Object,
+        "bucket",
+        Some("object"),
+        Some("version-a"),
+        "sub_quorum_metadata",
+    );
+
+    assert_eq!(scanner.new_cache.info.pending_heals.len(), 1);
+    assert_eq!(scanner.new_cache.info.pending_heals[0].last_admission_reason, "sub_quorum_metadata");
+}
+
 #[test]
 fn test_pending_heal_retry_candidates_respect_cap_and_order() {
     let pending: Vec<PendingScannerHeal> = (0..(MAX_PENDING_SCANNER_HEAL_RETRIES_PER_BUCKET + 2))
@@ -1323,6 +1374,20 @@ fn metadata_for_object(bucket: &str, object: &str) -> Vec<u8> {
     meta.marshal_msg().expect("test metadata should marshal")
 }
 
+fn metadata_for_object_version(bucket: &str, object: &str, version_id: Option<Uuid>) -> Vec<u8> {
+    let mut file_info = FileInfo::new(object, 4, 2);
+    file_info.volume = bucket.to_string();
+    file_info.name = object.to_string();
+    file_info.version_id = version_id;
+    file_info.versioned = version_id.is_some();
+    file_info.mod_time = Some(OffsetDateTime::now_utc());
+    file_info.size = 1;
+
+    let mut meta = FileMeta::new();
+    meta.add_version(file_info).expect("test metadata version should be accepted");
+    meta.marshal_msg().expect("test metadata should marshal")
+}
+
 async fn write_test_object_metadata(root: &std::path::Path, bucket: &str, object: &str) {
     write_test_object_metadata_bytes(root, bucket, object, &metadata_for_object(bucket, object)).await;
 }
@@ -1726,12 +1791,21 @@ async fn test_scan_folder_exits_when_abandoned_child_listing_finishes() {
     let _guard = TestGuard::new(60, 100, &mut scanner, temp_dir.clone());
     let heal_starts = Arc::new(AtomicUsize::new(0));
     let heal_starts_clone = heal_starts.clone();
+    let healed_versions = Arc::new(Mutex::new(Vec::<Option<String>>::new()));
+    let healed_versions_clone = healed_versions.clone();
     let mut heal_rx =
         rustfs_common::heal_channel::init_heal_channel().expect("heal channel should initialize once for scanner tests");
     let _heal_responder = tokio::spawn(async move {
         while let Some(command) = heal_rx.recv().await {
-            if let rustfs_common::heal_channel::HealChannelCommand::Start { response_tx, .. } = command {
+            if let rustfs_common::heal_channel::HealChannelCommand::Start {
+                request, response_tx, ..
+            } = command
+            {
                 heal_starts_clone.fetch_add(1, Ordering::Relaxed);
+                healed_versions_clone
+                    .lock()
+                    .expect("heal version capture lock should not be poisoned")
+                    .push(request.object_version_id);
                 let _ = response_tx.send(Ok(HealAdmissionResult::Accepted));
             }
         }
@@ -1739,13 +1813,18 @@ async fn test_scan_folder_exits_when_abandoned_child_listing_finishes() {
 
     let bucket = "src-archive";
     let object = "snapshots/37b3f20d941e2f5e6d99114d9bb2f3e67a8a2e5c9c4c5a1b0d6e7f8091a2b3c4";
-    let metadata = metadata_for_object(bucket, object);
-    write_test_object_metadata_bytes(&temp_dir, bucket, object, &metadata).await;
+    let orphan_version = Uuid::from_u128(0x1934);
+    let shared_version = Uuid::from_u128(0x1935);
+    let orphan_metadata = metadata_for_object_version(bucket, object, Some(orphan_version));
+    let shared_metadata = metadata_for_object_version(bucket, object, Some(shared_version));
+    write_test_object_metadata_bytes(&temp_dir, bucket, object, &orphan_metadata).await;
+    let mut expected_metadata = vec![(temp_dir.join(bucket).join(object).join("xl.meta"), orphan_metadata.clone())];
 
     let mut disks = vec![scanner.local_disk.clone()];
     for disk_name in ["disk2", "disk3", "disk4"] {
         let disk_root = temp_dir.join(disk_name);
-        write_test_object_metadata_bytes(&disk_root, bucket, object, &metadata).await;
+        write_test_object_metadata_bytes(&disk_root, bucket, object, &shared_metadata).await;
+        expected_metadata.push((disk_root.join(bucket).join(object).join("xl.meta"), shared_metadata.clone()));
         let endpoint = Endpoint::try_from(disk_root.to_string_lossy().as_ref()).expect("failed to create extra disk endpoint");
         let disk = new_disk(
             &endpoint,
@@ -1794,8 +1873,29 @@ async fn test_scan_folder_exits_when_abandoned_child_listing_finishes() {
         .new_cache
         .checked_flatten(bucket)
         .expect("healed cache must contain canonical child links");
-    assert_eq!(root.objects, 1);
+    // The fixture intentionally exposes two divergent version histories, so
+    // the scanner keeps both logical versions visible while discovering heals.
+    assert_eq!(root.objects, 2);
     assert!(heal_starts.load(Ordering::Relaxed) > 0, "test must execute the heal child-link path");
+    let orphan_version_text = orphan_version.to_string();
+    assert!(
+        healed_versions
+            .lock()
+            .expect("heal version capture lock should not be poisoned")
+            .iter()
+            .any(|version| version.as_deref() == Some(orphan_version_text.as_str())),
+        "sub-quorum orphan version must be submitted as an exact heal candidate"
+    );
+    for (path, expected) in expected_metadata {
+        assert_eq!(
+            tokio::fs::read(&path)
+                .await
+                .expect("scanner discovery must not delete metadata"),
+            expected,
+            "scanner discovery must not modify candidate metadata: {}",
+            path.display()
+        );
+    }
 }
 
 #[tokio::test]