Merge branch 'main' into houseme/fix/scanner-root-publication-proof-final

Bind ACK expectations to validated scan candidates and confirm the actual primary-root revision and readback. Retain saved outcomes and dirty responsibility when stronger evidence is unavailable. Isolate CAS attempt confirmation and invalidate proof after scope mutations.

Revalidate observed candidate reuse before issuing a new publication proof, preserve the exact validated authoritative baseline work digest, and settle fixture commit tails before stable maintenance scans. Keep scoped ACK production disabled.

Co-Authored-By: heihutu <heihutu@gmail.com>
Co-Authored-By: zhi22915 <qiuzgang@gmail.com>

crates/scanner/src/scanner.rs

@@ -1910,10 +1910,10 @@ where
         .as_ref()
         .map(|(notification_system, grants)| (Arc::clone(notification_system), grants.clone()));
     let remote_lease_release_safe = Arc::new(AtomicBool::new(true));
-    let mut usage_persist_outcome = match publication_defer_reason {
+    let mut usage_publication_result = match publication_defer_reason {
         Some(reason) => {
             drop(receiver);
-            DataUsagePersistOutcome::Deferred(reason)
+            DataUsagePublicationResult::from(DataUsagePersistOutcome::Deferred(reason))
         }
         None => {
             // ScannerIO emits its complete or observational update only after
@@ -1928,6 +1928,11 @@ where
                 .as_ref()
                 .map(|(_, grants)| grants.iter().map(|grant| grant.lease.token).collect())
                 .unwrap_or_default();
+            let ack_expectation = scan_result
+                .as_ref()
+                .ok()
+                .filter(|result| result.has_dirty_usage_to_acknowledge())
+                .and_then(ScannerCycleResult::publication_expectation);
             let mut usage_persist_task = AbortOnDropHandle::new(tokio::spawn(async move {
                 store_data_usage_in_backend_with_outcome_for_epoch_and_baseline_and_route_probe_for_publication_epoch_and_lease_fence(
                     ctx_clone,
@@ -1940,6 +1945,7 @@ where
                         remote_lease_deadline,
                         remote_lease_fence,
                     )
+                    .with_ack_expectation(ack_expectation)
                     .with_remote_lease_tokens(remote_lease_tokens)
                     .with_lease_release_flag(remote_lease_release_safe_for_task),
                     move || {
@@ -1973,7 +1979,7 @@ where
                         error = %err,
                         "Scanner data usage persistence task failed"
                     );
-                    DataUsagePersistOutcome::Failed
+                    DataUsagePublicationResult::from(DataUsagePersistOutcome::Failed)
                 }
                 DataUsagePersistTaskResult::Cancelled => {
                     debug!(
@@ -1985,7 +1991,7 @@ where
                         state = "usage_persist_task_cancelled",
                         "Scanner data usage persistence task cancelled"
                     );
-                    DataUsagePersistOutcome::Failed
+                    DataUsagePublicationResult::from(DataUsagePersistOutcome::Failed)
                 }
                 DataUsagePersistTaskResult::TimedOut => {
                     error!(
@@ -1998,11 +2004,12 @@ where
                         state = "usage_persist_task_timed_out",
                         "Scanner data usage persistence task timed out"
                     );
-                    DataUsagePersistOutcome::Failed
+                    DataUsagePublicationResult::from(DataUsagePersistOutcome::Failed)
                 }
             }
         }
     };
+    let mut usage_persist_outcome = usage_publication_result.outcome();
     let lease_expired = remote_publication_leases
         .as_ref()
         .is_some_and(|(_, grants)| grants.iter().any(|grant| !grant.lease.is_valid()));
@@ -2202,8 +2209,9 @@ where
         };
     }
 
+    usage_publication_result.restrict_outcome(usage_persist_outcome);
     let (completion_outcome, scanner_pending_maintenance_work, remote_dirty_usage_acknowledgements) =
-        finalize_scanner_cycle_result(scan_cycle_result, usage_persist_outcome);
+        finalize_scanner_cycle_result(scan_cycle_result, usage_publication_result);
     let remote_dirty_usage_pending = if remote_dirty_usage_acknowledgements.is_empty() {
         false
     } else if let Some(notification_system) = storeapi.scanner_notification_system() {
@@ -3437,21 +3445,35 @@ fn scanner_cycle_completion_outcome(
 
 fn finalize_scanner_cycle_result(
     scan_cycle_result: crate::scanner_io::ScannerCycleResult,
-    usage_persist_outcome: DataUsagePersistOutcome,
+    publication: DataUsagePublicationResult,
 ) -> (ScannerCycleOutcome, bool, Vec<ScannerDirtyUsageAcknowledgement>) {
+    let (usage_persist_outcome, proof) = publication.into_parts();
     let completion_outcome = scanner_cycle_completion_outcome_for_result(&scan_cycle_result, usage_persist_outcome);
-    let pending_maintenance_work = scan_cycle_result.has_pending_maintenance_work();
     let durable_complete_snapshot = scan_cycle_result.status == ScannerCycleStatus::Complete
         && matches!(
             usage_persist_outcome,
             DataUsagePersistOutcome::Saved | DataUsagePersistOutcome::AlreadyDurable
-        );
+        )
+        && scan_cycle_result.publication_expectation().as_ref().is_some_and(|expected| {
+            proof
+                .as_ref()
+                .is_some_and(|proof| proof.verified_version_for(expected).is_some())
+        });
+    let pending_maintenance_work = scan_cycle_result.has_pending_maintenance_work()
+        || (scan_cycle_result.has_dirty_usage_to_acknowledge() && !durable_complete_snapshot);
     let remote_dirty_usage_acknowledgements = if durable_complete_snapshot {
-        scan_cycle_result.acknowledge_durable_usage()
+        match proof {
+            Some(proof) => scan_cycle_result.acknowledge_durable_usage(&proof),
+            None => Vec::new(),
+        }
     } else {
         Vec::new()
     };
-    (completion_outcome, pending_maintenance_work, remote_dirty_usage_acknowledgements)
+    (
+        completion_outcome,
+        pending_maintenance_work || crate::scanner_io::dirty_usage_buckets_pending(),
+        remote_dirty_usage_acknowledgements,
+    )
 }
 
 fn scanner_cycle_completion_outcome_for_result(
@@ -3551,6 +3573,7 @@ use activity::*;
 use backlog::*;
 use cycle_state::*;
 use leadership::*;
+pub(crate) use usage_store::RootPublicationProof;
 use usage_store::*;
 
 pub use activity::scanner_topology_digest;

crates/scanner/src/scanner/tests.rs

@@ -37,6 +37,7 @@ use tokio::time::{Duration, advance};
 const TEST_DEFAULT_SCANNER_CYCLE_SECS: u64 = 24 * 60 * 60;
 
 mod recovery_control;
+mod scoped_ack_publication;
 
 async fn setup_scanner_cycle_store() -> (tempfile::TempDir, Arc<ECStore>) {
     setup_scanner_cycle_store_with_usage_baseline(true).await
@@ -6184,7 +6185,7 @@ async fn coordinator_classifies_an_expired_publication_lease() {
         .await;
 
     assert_eq!(
-        outcome,
+        outcome.outcome(),
         DataUsagePersistOutcome::Deferred(ScannerCycleDeferReason::PublicationLeaseDeadlineExceeded)
     );
     assert!(store.put_counts.lock().await.is_empty(), "expired lease must prevent a PUT");
@@ -7325,7 +7326,7 @@ fn scanner_cycle_cache_floor_stays_pending_during_deferred_usage_publication() {
 
 #[test]
 #[serial]
-fn finalizing_a_saved_cycle_acknowledges_its_exact_dirty_snapshot() {
+fn finalizing_a_saved_enum_without_proof_keeps_dirty_pending() {
     crate::scanner_io::clear_dirty_usage_bucket("photos");
     crate::scanner_io::record_dirty_usage_bucket("photos");
     let dirty_snapshot = crate::scanner_io::dirty_usage_buckets_for_tests();
@@ -7337,17 +7338,19 @@ fn finalizing_a_saved_cycle_acknowledges_its_exact_dirty_snapshot() {
     };
     let unsaved = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(dirty_snapshot.clone()))
         .with_remote_dirty_usage_acknowledgements(vec![remote_acknowledgement.clone()]);
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(unsaved, DataUsagePersistOutcome::NoUpdate);
+    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(unsaved, DataUsagePersistOutcome::NoUpdate.into());
     assert_eq!(outcome, ScannerCycleOutcome::Failed);
     assert!(acknowledgements.is_empty());
     assert!(crate::scanner_io::dirty_usage_buckets_pending());
 
     let saved = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(dirty_snapshot))
-        .with_remote_dirty_usage_acknowledgements(vec![remote_acknowledgement.clone()]);
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(saved, DataUsagePersistOutcome::Saved);
+        .with_remote_dirty_usage_acknowledgements(vec![remote_acknowledgement]);
+    let (outcome, pending, acknowledgements) = finalize_scanner_cycle_result(saved, DataUsagePersistOutcome::Saved.into());
     assert_eq!(outcome, ScannerCycleOutcome::Completed);
-    assert_eq!(acknowledgements, vec![remote_acknowledgement]);
-    assert!(!crate::scanner_io::dirty_usage_buckets_pending());
+    assert!(acknowledgements.is_empty());
+    assert!(pending);
+    assert!(crate::scanner_io::dirty_usage_buckets_pending());
+    crate::scanner_io::clear_dirty_usage_bucket("photos");
 }
 
 #[test]
@@ -7359,7 +7362,7 @@ fn finalizing_a_deferred_usage_save_keeps_dirty_work_pending() {
     let deferred = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(dirty_snapshot));
 
     let (outcome, _, acknowledgements) =
-        finalize_scanner_cycle_result(deferred, DataUsagePersistOutcome::Deferred(ScannerCycleDeferReason::DataMovement));
+        finalize_scanner_cycle_result(deferred, DataUsagePersistOutcome::Deferred(ScannerCycleDeferReason::DataMovement).into());
 
     assert_eq!(outcome, ScannerCycleOutcome::Deferred(ScannerCycleDeferReason::DataMovement));
     assert!(acknowledgements.is_empty());
@@ -7379,7 +7382,7 @@ fn finalizing_post_scan_observation_advances_partially_without_dirty_ack() {
     )
     .with_observational_snapshot_published(true);
 
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(observed, DataUsagePersistOutcome::Saved);
+    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(observed, DataUsagePersistOutcome::Saved.into());
 
     assert_eq!(outcome, ScannerCycleOutcome::Partial);
     assert!(acknowledgements.is_empty());
@@ -7415,17 +7418,20 @@ async fn scanner_cycle_keeps_remote_pending_acknowledgement() {
 
 #[test]
 #[serial]
-fn finalizing_an_already_durable_cycle_acknowledges_its_exact_dirty_snapshot() {
+fn finalizing_an_already_durable_enum_without_proof_keeps_dirty_pending() {
     crate::scanner_io::clear_dirty_usage_bucket("photos");
     crate::scanner_io::record_dirty_usage_bucket("photos");
     let dirty_snapshot = crate::scanner_io::dirty_usage_buckets_for_tests();
 
     let durable = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(dirty_snapshot));
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(durable, DataUsagePersistOutcome::AlreadyDurable);
+    let (outcome, pending, acknowledgements) =
+        finalize_scanner_cycle_result(durable, DataUsagePersistOutcome::AlreadyDurable.into());
 
     assert_eq!(outcome, ScannerCycleOutcome::Completed);
     assert!(acknowledgements.is_empty());
-    assert!(!crate::scanner_io::dirty_usage_buckets_pending());
+    assert!(pending);
+    assert!(crate::scanner_io::dirty_usage_buckets_pending());
+    crate::scanner_io::clear_dirty_usage_bucket("photos");
 }
 
 #[test]
@@ -7436,7 +7442,8 @@ fn finalizing_a_prior_same_cycle_snapshot_keeps_new_dirty_work_pending() {
     let dirty_snapshot = crate::scanner_io::dirty_usage_buckets_for_tests();
 
     let durable = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(dirty_snapshot));
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(durable, DataUsagePersistOutcome::PriorCycleDurable);
+    let (outcome, _, acknowledgements) =
+        finalize_scanner_cycle_result(durable, DataUsagePersistOutcome::PriorCycleDurable.into());
 
     assert_eq!(outcome, ScannerCycleOutcome::Completed);
     assert!(acknowledgements.is_empty());
@@ -7452,7 +7459,7 @@ fn finalizing_a_durable_superseded_snapshot_keeps_dirty_work_pending() {
     let dirty_snapshot = crate::scanner_io::dirty_usage_buckets_for_tests();
 
     let superseded = crate::scanner_io::ScannerCycleResult::new(ScannerCycleStatus::Superseded, Some(dirty_snapshot));
-    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(superseded, DataUsagePersistOutcome::Saved);
+    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(superseded, DataUsagePersistOutcome::Saved.into());
 
     assert_eq!(outcome, ScannerCycleOutcome::Superseded);
     assert!(acknowledgements.is_empty());
@@ -8881,7 +8888,7 @@ fn post_lease_activity_proof_rejects_a_put_tail_that_finished_before_lease_acqui
     ]);
     let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(
         result,
-        DataUsagePersistOutcome::Deferred(reason.expect("changed namespace should defer publication")),
+        DataUsagePersistOutcome::Deferred(reason.expect("changed namespace should defer publication")).into(),
     );
     assert_eq!(
         outcome,

crates/scanner/src/scanner/tests/scoped_ack_publication.rs

@@ -0,0 +1,490 @@
+// Copyright 2026 RustFS Team
+// Licensed under the Apache License, Version 2.0.
+
+use super::super::usage_store::DataUsagePublicationResult;
+use super::*;
+use crate::scanner_io::ScannerBucketScanScope;
+use rustfs_utils::path::path_join_buf;
+use sha2::Digest;
+use std::time::SystemTime;
+
+const PROOF_BUCKET: &str = "publication-proof-bucket";
+const PROOF_EPOCH: u64 = 7;
+const PROOF_CYCLE: u64 = 11;
+
+async fn settle_namespace_commits(store: &ECStore) {
+    tokio::time::timeout(Duration::from_secs(30), async {
+        while store.scanner_data_usage_publication_blocked().await {
+            tokio::time::sleep(Duration::from_millis(1)).await;
+        }
+    })
+    .await
+    .expect("fixture namespace commits must settle before collecting complete coverage");
+}
+
+async fn complete_candidate(store: &Arc<ECStore>, cycle: u64) -> (crate::scanner_io::ScannerCycleResult, DataUsageInfo) {
+    settle_namespace_commits(store).await;
+    let ctx = CancellationToken::new();
+    let budget = ScannerCycleBudget::new_with_progress_tracking(
+        &ctx,
+        ScannerCycleBudgetConfig {
+            max_objects: Some(8),
+            ..Default::default()
+        },
+    );
+    let (updates, mut receiver) = mpsc::channel(1);
+    let result = crate::scanner_io::nsscanner_with_storage_status_scoped(
+        store.as_ref(),
+        crate::scanner_io::ScannerCycleRequest {
+            ctx,
+            budget,
+            updates,
+            want_cycle: cycle,
+            leader_epoch: PROOF_EPOCH,
+            scan_mode: HealScanMode::Normal,
+            scan_scope: ScannerBucketScanScope::default(),
+            persisted_usage_baseline: None,
+            observed_usage_candidate: None,
+            requires_full_scan: true,
+            service_cohort: None,
+            resolved_scope_observer: None,
+        },
+    )
+    .await
+    .expect("real scanner must produce the fixture candidate");
+    assert_eq!(result.status, ScannerCycleStatus::Complete);
+    let candidate = receiver.recv().await.expect("complete scanner snapshot");
+    assert!(candidate.usage_snapshot_complete);
+    assert_eq!(candidate.usage_snapshot_converged, Some(true));
+    assert_eq!(candidate.scanner_cycle, Some(cycle));
+    assert_eq!(candidate.scanner_epoch, Some(PROOF_EPOCH));
+    (result, candidate)
+}
+
+async fn candidate_store() -> (tempfile::TempDir, Arc<ECStore>) {
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+    let (directory, store) = setup_scanner_cycle_store_with_usage_baseline(false).await;
+    store
+        .make_bucket(PROOF_BUCKET, &crate::storage_api::scan::MakeBucketOptions::default())
+        .await
+        .expect("create proof fixture bucket through the owner");
+    let mut reader = PutObjReader::from_vec(b"proof".to_vec());
+    store.pools[0].disk_set[0]
+        .put_object(PROOF_BUCKET, "initial", &mut reader, &ObjectOptions::default())
+        .await
+        .expect("persist fixture object through the owner");
+    crate::scanner_io::record_dirty_usage_bucket(PROOF_BUCKET);
+    settle_namespace_commits(&store).await;
+    (directory, store)
+}
+
+async fn read_root(store: &Arc<ECStore>) -> (Option<Vec<u8>>, DataUsageCacheRevision) {
+    read_config_with_revision(store.clone(), DATA_USAGE_OBJ_NAME_PATH.as_str())
+        .await
+        .expect("read actual v2 root bytes and revision")
+}
+
+async fn publish_candidate(
+    store: &Arc<ECStore>,
+    scan: &crate::scanner_io::ScannerCycleResult,
+    candidate: DataUsageInfo,
+    baseline: Option<DataUsagePersistBaseline>,
+) -> DataUsagePublicationResult {
+    let expectation = scan.publication_expectation();
+    assert!(expectation.is_some(), "only a real complete scan may supply the expectation");
+    let (sender, receiver) = mpsc::channel(1);
+    sender.send(candidate).await.expect("enqueue the real scan candidate");
+    drop(sender);
+    store_data_usage_in_backend_with_outcome_for_epoch_and_baseline_and_route_probe_for_publication_epoch_and_lease_fence(
+        CancellationToken::new(),
+        store.clone(),
+        receiver,
+        Some(PROOF_EPOCH),
+        baseline,
+        ScannerPublicationFence::new(scan.publication_epoch(), None, None).with_ack_expectation(expectation),
+        || async { None },
+    )
+    .await
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_companion_only_does_not_authorize_root_ack() {
+    for companion in [
+        format!("{}.bkp", DATA_USAGE_OBJ_NAME_PATH.as_str()),
+        LEGACY_DATA_USAGE_OBJ_NAME_PATH.to_string(),
+        format!("{}.bkp", LEGACY_DATA_USAGE_OBJ_NAME_PATH.as_str()),
+    ] {
+        let (_directory, store) = candidate_store().await;
+        let (scan, candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+        let bytes = serde_json::to_vec(&candidate).expect("actual candidate JSON");
+        save_config(store.clone(), &companion, bytes.clone())
+            .await
+            .expect("persist the companion on real disks");
+        let baseline = read_data_usage_persist_baseline(store.clone())
+            .await
+            .expect("companion fallback baseline");
+        assert_eq!(baseline.data.as_deref(), Some(bytes.as_slice()));
+        assert_eq!(baseline.revision, DataUsageCacheRevision::Missing);
+        assert_eq!(read_root(&store).await.0, None);
+        let dirty = crate::scanner_io::dirty_usage_buckets_for_tests();
+
+        let publication = publish_candidate(&store, &scan, candidate, Some(baseline)).await;
+        assert_eq!(publication.outcome(), DataUsagePersistOutcome::AlreadyDurable);
+        let (_, pending, acknowledgements) = finalize_scanner_cycle_result(scan, publication);
+        assert!(pending, "unacknowledged durable companion work must remain pending");
+        assert!(acknowledgements.is_empty());
+        assert_eq!(
+            crate::scanner_io::dirty_usage_buckets_for_tests(),
+            dirty,
+            "a companion is not the v2 root target"
+        );
+        assert_eq!(read_root(&store).await, (None, DataUsageCacheRevision::Missing));
+        assert_eq!(read_config(store.clone(), &companion).await.expect("companion retained"), bytes);
+    }
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_actual_root_readback_accepts_semantic_json_equivalence() {
+    let (_directory, store) = candidate_store().await;
+    let (scan, candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    let canonical = serde_json::to_vec(&candidate).expect("candidate encoding");
+    let mut value = serde_json::to_value(&candidate).expect("candidate value");
+    value
+        .as_object_mut()
+        .expect("usage object")
+        .insert("fixture_unknown_field".into(), serde_json::json!({"retained": true}));
+    let different_bytes = serde_json::to_vec_pretty(&value).expect("noncanonical primary JSON");
+    assert_ne!(different_bytes, canonical);
+    assert_eq!(
+        serde_json::from_slice::<DataUsageInfo>(&different_bytes).expect("semantic primary"),
+        candidate
+    );
+    save_config(store.clone(), DATA_USAGE_OBJ_NAME_PATH.as_str(), different_bytes.clone())
+        .await
+        .expect("persist actual primary representation");
+    let before = read_root(&store).await;
+    assert!(matches!(&before.1, DataUsageCacheRevision::Etag(etag) if !etag.is_empty()));
+    let baseline = read_data_usage_persist_baseline(store.clone())
+        .await
+        .expect("real primary revision");
+    assert!(crate::scanner_io::dirty_usage_buckets_pending());
+
+    let publication = publish_candidate(&store, &scan, candidate.clone(), Some(baseline)).await;
+    assert_eq!(publication.outcome(), DataUsagePersistOutcome::AlreadyDurable);
+    let (_, proof) = publication.into_parts();
+    let proof = proof.expect("actual primary readback must produce its own root proof");
+    let expected = scan.publication_expectation().expect("real scan expectation");
+    let (etag, raw_digest) = proof.verified_version_for(&expected).expect("proof must bind this candidate");
+    let DataUsageCacheRevision::Etag(expected_etag) = &before.1 else { panic!("actual root ETag") };
+    assert_eq!(etag, expected_etag);
+    let expected_digest: [u8; 32] = sha2::Sha256::digest(&different_bytes).into();
+    assert_eq!(
+        *raw_digest, expected_digest,
+        "proof must record actual bytes, not reserialized candidate bytes"
+    );
+    // Obtain another proof through the same real readback path rather than
+    // fabricating a publication result from the inspected proof above.
+    let publication = publish_candidate(&store, &scan, candidate, None).await;
+    let (outcome, _, acknowledgements) = finalize_scanner_cycle_result(scan, publication);
+    assert_eq!(outcome, ScannerCycleOutcome::Completed);
+    assert!(acknowledgements.is_empty(), "the single-node fixture has no remote targets");
+    assert!(
+        !crate::scanner_io::dirty_usage_buckets_pending(),
+        "actual root bytes plus a real revision authorize this scan"
+    );
+    assert_eq!(read_root(&store).await, before, "readback must not rewrite unknown fields or whitespace");
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_successful_root_cas_authorizes_its_scan() {
+    let (_directory, store) = candidate_store().await;
+    let (scan, candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    let baseline = read_data_usage_persist_baseline(store.clone())
+        .await
+        .expect("initial root revision");
+    assert_eq!(baseline.revision, DataUsageCacheRevision::Missing);
+    assert!(crate::scanner_io::dirty_usage_buckets_pending());
+    let publication = publish_candidate(&store, &scan, candidate.clone(), Some(baseline)).await;
+    assert_eq!(publication.outcome(), DataUsagePersistOutcome::Saved);
+    let (bytes, revision) = read_root(&store).await;
+    assert!(matches!(revision, DataUsageCacheRevision::Etag(etag) if !etag.is_empty()));
+    assert_eq!(
+        serde_json::from_slice::<DataUsageInfo>(&bytes.expect("actual saved root")).expect("root JSON"),
+        candidate
+    );
+    let (outcome, pending, acknowledgements) = finalize_scanner_cycle_result(scan, publication);
+    assert_eq!(outcome, ScannerCycleOutcome::Completed);
+    assert!(!pending);
+    assert!(acknowledgements.is_empty(), "the single-node fixture has no remote targets");
+    assert!(
+        !crate::scanner_io::dirty_usage_buckets_pending(),
+        "the real root CAS must authorize its matching scan"
+    );
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_observed_candidate_reuse_requires_a_new_root_proof() {
+    let (_directory, store) = candidate_store().await;
+    let bootstrap = scanner_usage_bootstrap_marker(SystemTime::now(), Some(PROOF_EPOCH));
+    save_config(
+        store.clone(),
+        DATA_USAGE_OBJ_NAME_PATH.as_str(),
+        serde_json::to_vec(&bootstrap).expect("bootstrap root encoding"),
+    )
+    .await
+    .expect("persist authoritative bootstrap root");
+    let (prior_scan, mut observed_candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    // Seed a complete but unconverged observation from real scanner coverage;
+    // the production writer attaches its authoritative baseline identity.
+    observed_candidate.usage_snapshot_converged = Some(false);
+    let observation = publish_candidate(&store, &prior_scan, observed_candidate, None).await;
+    let (outcome, proof) = observation.into_parts();
+    assert_eq!(outcome, DataUsagePersistOutcome::Saved);
+    assert!(proof.is_none(), "an observational write cannot authorize a root ACK");
+    let (root_before, revision_before) = read_root(&store).await;
+    let observed = read_config(store.clone(), DATA_USAGE_OBSERVED_OBJ_NAME_PATH.as_str())
+        .await
+        .expect("read real persisted observation");
+    let ctx = CancellationToken::new();
+    let budget = ScannerCycleBudget::new(&ctx, ScannerCycleBudgetConfig::default());
+    let (updates, mut receiver) = mpsc::channel(1);
+    let (observer, selected) = tokio::sync::oneshot::channel();
+    let scan = crate::scanner_io::nsscanner_with_storage_status_scoped(
+        store.as_ref(),
+        crate::scanner_io::ScannerCycleRequest {
+            ctx,
+            budget,
+            updates,
+            want_cycle: PROOF_CYCLE + 1,
+            leader_epoch: PROOF_EPOCH,
+            scan_mode: HealScanMode::Normal,
+            scan_scope: ScannerBucketScanScope::default(),
+            persisted_usage_baseline: root_before.clone().map(Bytes::from),
+            observed_usage_candidate: Some(Bytes::from(observed)),
+            requires_full_scan: false,
+            service_cohort: None,
+            resolved_scope_observer: Some(observer),
+        },
+    )
+    .await
+    .expect("observation-backed scope must run through the real scanner");
+    let scope = selected.await.expect("production resolver decision");
+    assert_eq!(scope.selected_buckets_for_tests(), Some(&HashSet::from([PROOF_BUCKET.to_string()])));
+    assert_eq!(scan.status, ScannerCycleStatus::Complete);
+    let expectation = scan.publication_expectation().expect("reused coverage must be revalidated");
+    assert!(
+        !expectation.same_candidate(&prior_scan.publication_expectation().expect("prior real candidate")),
+        "the observation cannot transfer the previous scan's expectation"
+    );
+    assert_eq!(read_root(&store).await, (root_before, revision_before));
+    assert!(crate::scanner_io::dirty_usage_buckets_pending());
+    let candidate = receiver.recv().await.expect("new validated root candidate");
+    assert_eq!(candidate.scanner_cycle, Some(PROOF_CYCLE + 1));
+    assert_eq!(candidate.usage_snapshot_converged, Some(true));
+    let publication = publish_candidate(&store, &scan, candidate, None).await;
+    assert_eq!(publication.outcome(), DataUsagePersistOutcome::Saved);
+    let (outcome, pending, acknowledgements) = finalize_scanner_cycle_result(scan, publication);
+    assert_eq!(outcome, ScannerCycleOutcome::Completed);
+    assert!(!pending);
+    assert!(acknowledgements.is_empty());
+    assert!(!crate::scanner_io::dirty_usage_buckets_pending());
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_stale_root_cas_keeps_dirty_after_bucket_save() {
+    let (_directory, store) = candidate_store().await;
+    let (scan, candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    let mut bucket_cache = DataUsageCache::default();
+    bucket_cache
+        .load(store.pools[0].disk_set[0].clone(), &path_join_buf(&[PROOF_BUCKET, DATA_USAGE_CACHE_NAME]))
+        .await
+        .expect("real bucket checkpoint must be persisted before root publication");
+    assert!(bucket_cache.info.snapshot_complete);
+    assert_eq!(
+        bucket_cache
+            .checked_flatten(PROOF_BUCKET)
+            .expect("persisted bucket root")
+            .objects,
+        1
+    );
+    let stale_baseline = read_data_usage_persist_baseline(store.clone())
+        .await
+        .expect("missing root revision");
+    assert_eq!(stale_baseline.revision, DataUsageCacheRevision::Missing);
+    let mut competing = candidate.clone();
+    competing.scanner_epoch = Some(PROOF_EPOCH + 1);
+    competing.scanner_cycle = Some(PROOF_CYCLE + 1);
+    for state in &mut competing.usage_snapshot_set_states {
+        state.scanner_epoch = Some(PROOF_EPOCH + 1);
+        state.scanner_cycle = Some(PROOF_CYCLE + 1);
+    }
+    let competing_bytes = serde_json::to_vec(&competing).expect("competing root");
+    save_config(store.clone(), DATA_USAGE_OBJ_NAME_PATH.as_str(), competing_bytes.clone())
+        .await
+        .expect("another publisher wins the actual root slot");
+    let before = read_root(&store).await;
+    let dirty = crate::scanner_io::dirty_usage_buckets_for_tests();
+
+    let publication = publish_candidate(&store, &scan, candidate, Some(stale_baseline)).await;
+    assert_eq!(
+        publication.outcome(),
+        DataUsagePersistOutcome::Current,
+        "the old missing revision loses CAS and reconciles the newer root"
+    );
+    let (_, _, acknowledgements) = finalize_scanner_cycle_result(scan, publication);
+    assert!(acknowledgements.is_empty());
+    assert_eq!(crate::scanner_io::dirty_usage_buckets_for_tests(), dirty);
+    assert_eq!(
+        read_root(&store).await,
+        before,
+        "bucket durability must not authorize replacing the winning root"
+    );
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_cannot_transfer_proof_between_real_scan_results() {
+    let (_directory, store) = candidate_store().await;
+    let (first_scan, first_candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    let (second_scan, second_candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    assert_eq!(first_candidate.scanner_epoch, second_candidate.scanner_epoch);
+    assert_eq!(first_candidate.scanner_cycle, second_candidate.scanner_cycle);
+    assert_eq!(first_candidate.objects_total_count, second_candidate.objects_total_count);
+    let baseline = read_data_usage_persist_baseline(store.clone())
+        .await
+        .expect("initial root revision");
+    let dirty = crate::scanner_io::dirty_usage_buckets_for_tests();
+    let publication = publish_candidate(&store, &first_scan, first_candidate, Some(baseline)).await;
+    assert_eq!(publication.outcome(), DataUsagePersistOutcome::Saved);
+    assert!(read_root(&store).await.0.is_some(), "the first scan really published its root");
+
+    let (_, pending, acknowledgements) = finalize_scanner_cycle_result(second_scan, publication);
+    assert!(pending, "another scan's publication must not finish this scan's dirty maintenance work");
+    assert!(acknowledgements.is_empty());
+    assert_eq!(
+        crate::scanner_io::dirty_usage_buckets_for_tests(),
+        dirty,
+        "same counters and cycle cannot transfer another scan's proof"
+    );
+
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_stale_baseline_cannot_prove_a_replaced_root() {
+    let (_directory, store) = candidate_store().await;
+    let (first_scan, first_candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+    save_config(
+        store.clone(),
+        DATA_USAGE_OBJ_NAME_PATH.as_str(),
+        serde_json::to_vec(&first_candidate).expect("first candidate"),
+    )
+    .await
+    .expect("persist the first candidate on real disks");
+    let stale_baseline = read_data_usage_persist_baseline(store.clone())
+        .await
+        .expect("capture the genuine first root revision");
+    let dirty = crate::scanner_io::dirty_usage_buckets_for_tests();
+    let mut reader = PutObjReader::from_vec(b"second".to_vec());
+    store.pools[0].disk_set[0]
+        .put_object(PROOF_BUCKET, "second", &mut reader, &ObjectOptions::default())
+        .await
+        .expect("commit a real namespace change");
+    assert_eq!(
+        crate::scanner_io::dirty_usage_buckets_for_tests(),
+        dirty,
+        "direct storage writes leave this fixture's scanner hint generation unchanged"
+    );
+    let (_, replacement) = complete_candidate(&store, PROOF_CYCLE).await;
+    assert_eq!(first_candidate.scanner_epoch, replacement.scanner_epoch);
+    assert_eq!(first_candidate.scanner_cycle, replacement.scanner_cycle);
+    assert_eq!((first_candidate.objects_total_count, replacement.objects_total_count), (1, 2));
+    save_config(
+        store.clone(),
+        DATA_USAGE_OBJ_NAME_PATH.as_str(),
+        serde_json::to_vec(&replacement).expect("replacement candidate"),
+    )
+    .await
+    .expect("publish the replacement root");
+    let current = read_root(&store).await;
+    assert_ne!(current.1, stale_baseline.revision);
+
+    // The supplied baseline still equals candidate A, but the actual target
+    // now contains B. Compatibility's AlreadyDurable outcome is not proof.
+    let publication = publish_candidate(&store, &first_scan, first_candidate, Some(stale_baseline)).await;
+    assert_eq!(publication.outcome(), DataUsagePersistOutcome::AlreadyDurable);
+    let (_, pending, acknowledgements) = finalize_scanner_cycle_result(first_scan, publication);
+    assert!(pending);
+    assert!(acknowledgements.is_empty());
+    assert_eq!(crate::scanner_io::dirty_usage_buckets_for_tests(), dirty);
+    assert_eq!(read_root(&store).await, current);
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+}
+
+#[tokio::test]
+#[serial]
+async fn scoped_ack_publication_rejects_builder_mutation_after_real_root_publish() {
+    for mutation in ["remote_ack_target", "publication_epoch", "remote_lease_targets"] {
+        let (_directory, store) = candidate_store().await;
+        let (scan, candidate) = complete_candidate(&store, PROOF_CYCLE).await;
+        let baseline = read_data_usage_persist_baseline(store.clone())
+            .await
+            .expect("initial root revision");
+        let dirty = crate::scanner_io::dirty_usage_buckets_for_tests();
+        let changed_generation = dirty
+            .get(PROOF_BUCKET)
+            .expect("the real scan has dirty work")
+            .checked_add(1)
+            .expect("bounded fixture generation");
+        let changed_epoch = scan
+            .publication_epoch()
+            .expect("real scan publication epoch")
+            .checked_add(1)
+            .expect("bounded fixture epoch");
+        let publication = publish_candidate(&store, &scan, candidate.clone(), Some(baseline)).await;
+        assert_eq!(publication.outcome(), DataUsagePersistOutcome::Saved, "{mutation}");
+        let root_before = read_root(&store).await;
+        assert_eq!(
+            serde_json::from_slice::<DataUsageInfo>(root_before.0.as_deref().expect("actual saved root"))
+                .expect("persisted root JSON"),
+            candidate,
+            "{mutation}: the original candidate really reached root storage"
+        );
+
+        let changed = match mutation {
+            "remote_ack_target" => scan.with_remote_dirty_usage_acknowledgements(vec![ScannerDirtyUsageAcknowledgement {
+                host: "proof-peer:9000".to_string(),
+                instance_id: crate::scanner_activity_epoch().to_string(),
+                generation: changed_generation,
+            }]),
+            "publication_epoch" => scan.with_publication_epoch(Some(changed_epoch)),
+            "remote_lease_targets" => scan.with_remote_publication_lease_targets(vec![(
+                "proof-peer:9000".to_string(),
+                crate::scanner_activity_epoch().to_string(),
+                changed_generation,
+            )]),
+            _ => unreachable!("fixed mutation cases"),
+        };
+        let (_, pending, acknowledgements) = finalize_scanner_cycle_result(changed, publication);
+        assert!(
+            acknowledgements.is_empty(),
+            "{mutation}: the old root proof must not authorize changed ACK work"
+        );
+        assert!(pending, "{mutation}: changed maintenance work must remain pending");
+        assert_eq!(
+            crate::scanner_io::dirty_usage_buckets_for_tests(),
+            dirty,
+            "{mutation}: the changed scan must not clear local dirty work"
+        );
+        assert_eq!(read_root(&store).await, root_before, "{mutation}: the durable original root is retained");
+    }
+    crate::scanner_io::clear_dirty_usage_buckets_for_tests();
+}

crates/scanner/src/scanner/usage_store.rs

@@ -34,6 +34,139 @@ pub(super) enum DataUsagePersistOutcome {
     Failed,
 }
 
+#[derive(Debug)]
+pub(crate) struct RootPublicationProof {
+    candidate: crate::scanner_io::ScannerPublicationExpectation,
+    root_version: (String, [u8; 32]),
+}
+
+impl RootPublicationProof {
+    pub(crate) fn verified_version_for(
+        &self,
+        expected: &crate::scanner_io::ScannerPublicationExpectation,
+    ) -> Option<&(String, [u8; 32])> {
+        self.candidate.same_candidate(expected).then_some(&self.root_version)
+    }
+}
+
+#[derive(Debug)]
+pub(super) struct DataUsagePublicationResult {
+    outcome: DataUsagePersistOutcome,
+    proof: Option<RootPublicationProof>,
+}
+
+impl From<DataUsagePersistOutcome> for DataUsagePublicationResult {
+    fn from(outcome: DataUsagePersistOutcome) -> Self {
+        Self { outcome, proof: None }
+    }
+}
+
+impl DataUsagePublicationResult {
+    pub(super) fn outcome(&self) -> DataUsagePersistOutcome {
+        self.outcome
+    }
+    pub(super) fn restrict_outcome(&mut self, outcome: DataUsagePersistOutcome) {
+        if outcome != self.outcome {
+            self.proof = None;
+        }
+        self.outcome = outcome;
+    }
+    pub(super) fn into_parts(self) -> (DataUsagePersistOutcome, Option<RootPublicationProof>) {
+        (self.outcome, self.proof)
+    }
+}
+
+fn root_ack_write_is_confirmed<T, E>(
+    result: &std::result::Result<T, E>,
+    state: Option<ScannerPublicationCommitState>,
+    written_etag: Option<&str>,
+) -> bool {
+    result.is_ok() && state == Some(ScannerPublicationCommitState::Committed) && written_etag.is_some_and(|etag| !etag.is_empty())
+}
+
+#[cfg(test)]
+mod root_publication_confirmation_tests {
+    use super::*;
+
+    #[test]
+    fn root_publication_confirmation_requires_committed_state_and_write_revision() {
+        let saved = Ok::<(), ()>(());
+        for state in [
+            None,
+            Some(ScannerPublicationCommitState::Admitted),
+            Some(ScannerPublicationCommitState::InFlight),
+            Some(ScannerPublicationCommitState::AbortedBeforeCommit),
+            Some(ScannerPublicationCommitState::Indeterminate),
+        ] {
+            assert!(!root_ack_write_is_confirmed(&saved, state, Some("revision")));
+        }
+        for etag in [None, Some("")] {
+            assert!(!root_ack_write_is_confirmed(&saved, Some(ScannerPublicationCommitState::Committed), etag));
+        }
+        assert!(root_ack_write_is_confirmed(
+            &saved,
+            Some(ScannerPublicationCommitState::Committed),
+            Some("revision")
+        ));
+    }
+
+    #[test]
+    fn root_publication_confirmation_does_not_carry_state_across_cas_attempts() {
+        let attempts = [
+            (Err(()), Some(ScannerPublicationCommitState::Committed), Some("first")),
+            (Ok(()), Some(ScannerPublicationCommitState::AbortedBeforeCommit), Some("second")),
+            (Ok(()), None, Some("legacy")),
+            (Ok(()), Some(ScannerPublicationCommitState::Committed), Some("confirmed")),
+        ];
+        let confirmations = attempts
+            .iter()
+            .map(|(result, state, etag)| root_ack_write_is_confirmed(result, *state, *etag))
+            .collect::<Vec<_>>();
+        assert_eq!(confirmations, [false, false, false, true]);
+    }
+}
+
+async fn read_root_publication_proof<S: ScannerObjectIO + ScannerConfigObjectDelete>(
+    store: Arc<S>,
+    ctx: &CancellationToken,
+    deadline: tokio::time::Instant,
+    epoch: u64,
+    expected: &crate::scanner_io::ScannerPublicationExpectation,
+    candidate: &DataUsageInfo,
+    written_etag: Option<&str>,
+) -> Option<RootPublicationProof> {
+    let read = async {
+        let _admission = scanner_publication_admission_for_epoch(store.clone(), epoch).await?;
+        let (bytes, revision) = read_config_with_revision(store, DATA_USAGE_OBJ_NAME_PATH.as_str())
+            .await
+            .ok()?;
+        let bytes = bytes?;
+        let DataUsageCacheRevision::Etag(etag) = revision else {
+            return None;
+        };
+        if etag.is_empty() || written_etag.is_some_and(|written| written != etag) {
+            return None;
+        }
+        let persisted: DataUsageInfo = serde_json::from_slice(&bytes).ok()?;
+        if &persisted != candidate {
+            return None;
+        }
+        let root_digest = Sha256::digest(&bytes).into();
+        if ctx.is_cancelled() || tokio::time::Instant::now() >= deadline {
+            return None;
+        }
+        Some(RootPublicationProof {
+            candidate: expected.clone(),
+            root_version: (etag, root_digest),
+        })
+    };
+    tokio::select! {
+        biased;
+        _ = ctx.cancelled() => None,
+        result = tokio::time::timeout_at(deadline, read) => result.ok().flatten(),
+    }
+}
+
 fn remote_lease_expired(deadline: Option<std::time::Instant>) -> bool {
     deadline.is_some_and(|deadline| std::time::Instant::now() >= deadline)
 }
@@ -166,6 +299,7 @@ pub(super) struct ScannerPublicationFence {
     pub(super) scanner_publication_lease_fence: Option<String>,
     pub(super) remote_lease_tokens: Vec<Uuid>,
     pub(super) lease_release_safe: Arc<AtomicBool>,
+    pub(super) ack_expectation: Option<crate::scanner_io::ScannerPublicationExpectation>,
 }
 
 impl ScannerPublicationFence {
@@ -180,6 +314,7 @@ impl ScannerPublicationFence {
             scanner_publication_lease_fence,
             remote_lease_tokens: Vec::new(),
             lease_release_safe: Arc::new(AtomicBool::new(true)),
+            ack_expectation: None,
         }
     }
 
@@ -192,21 +327,26 @@ impl ScannerPublicationFence {
         self.lease_release_safe = lease_release_safe;
         self
     }
+
+    pub(super) fn with_ack_expectation(mut self, expected: Option<crate::scanner_io::ScannerPublicationExpectation>) -> Self {
+        self.ack_expectation = expected;
+        self
+    }
 }
 
 #[derive(Debug)]
-pub(super) enum DataUsagePersistTaskResult {
-    Completed(DataUsagePersistOutcome),
+pub(super) enum DataUsagePersistTaskResult<T = DataUsagePersistOutcome> {
+    Completed(T),
     Cancelled,
     TimedOut,
     JoinFailed(tokio::task::JoinError),
 }
 
-pub(super) async fn wait_for_data_usage_persist_task(
+pub(super) async fn wait_for_data_usage_persist_task<T>(
     ctx: &CancellationToken,
-    task: &mut AbortOnDropHandle<DataUsagePersistOutcome>,
+    task: &mut AbortOnDropHandle<T>,
     timeout: Duration,
-) -> DataUsagePersistTaskResult {
+) -> DataUsagePersistTaskResult<T> {
     tokio::select! {
         biased;
         result = &mut *task => match result {
@@ -320,6 +460,7 @@ where
         route_probe,
     )
     .await
+    .outcome()
 }
 
 pub(super) async fn store_data_usage_in_backend_with_outcome_for_epoch_and_baseline_and_route_probe_for_publication_epoch_and_lease_fence<
@@ -333,7 +474,7 @@ pub(super) async fn store_data_usage_in_backend_with_outcome_for_epoch_and_basel
     initial_baseline: Option<DataUsagePersistBaseline>,
     publication_fence: ScannerPublicationFence,
     route_probe: F,
-) -> DataUsagePersistOutcome
+) -> DataUsagePublicationResult
 where
     F: Fn() -> Fut + Send + Sync,
     Fut: Future<Output = Option<ScannerCycleDeferReason>> + Send,
@@ -344,11 +485,15 @@ where
         scanner_publication_lease_fence,
         remote_lease_tokens,
         lease_release_safe,
+        ack_expectation,
     } = publication_fence;
+    let ack_deadline = scanner_publication_scope_deadline(data_usage_persist_timeout(), remote_lease_deadline);
     let mut outcome = DataUsagePersistOutcome::NoUpdate;
+    let mut proof = None;
     let mut next_baseline = initial_baseline;
 
     'updates: while let Some(mut data_usage_info) = receiver.recv().await {
+        proof = None;
         let _activity_guard = ScannerActivityGuard::new();
         if ctx.is_cancelled() {
             break;
@@ -523,10 +668,14 @@ where
                 continue;
             }
         };
-        let sha256hex = (!data.is_empty()).then(|| hex_simd::encode_to_string(Sha256::digest(&data), hex_simd::AsciiCase::Lower));
+        let data_digest: [u8; 32] = Sha256::digest(&data).into();
+        let sha256hex = (!data.is_empty()).then(|| hex_simd::encode_to_string(data_digest, hex_simd::AsciiCase::Lower));
         let data = Bytes::from(data);
         let backup_due = !observational && data_usage_backup_due(&data_usage_info);
         let mut cas_retry = 0usize;
+        let mut ack_epoch = None;
+        let mut write_confirmed = false;
+        let mut written_etag = None;
         let save_outcome = loop {
             if ctx.is_cancelled() {
                 break 'updates;
@@ -557,6 +706,7 @@ where
             } else {
                 None
             };
+            ack_epoch = Some(publication_epoch_for_save);
             let (existing_data, revision) = match baseline {
                 Some(baseline) => (baseline.data, baseline.revision),
                 None => match read_config_with_revision(storeapi.clone(), target_path).await {
@@ -645,7 +795,7 @@ where
             }
 
             let done_save = Metrics::time(Metric::SaveUsage);
-            let save_result = {
+            let (save_result, commit_state) = {
                 let publication_scope = storeapi
                     .scanner_data_usage_publication_commit_scope_with_release_flag(
                         publication_epoch_for_save,
@@ -681,24 +831,33 @@ where
                 .await;
                 drop(legacy_publication_admission);
                 if let Some(scope) = publication_scope {
-                    match scope.wait_for_completion().await {
-                        ScannerPublicationCommitState::Committed | ScannerPublicationCommitState::AbortedBeforeCommit => {
-                            save_result
-                        }
+                    let state = scope.wait_for_completion().await;
+                    let result = match state {
+                        ScannerPublicationCommitState::Committed => save_result,
+                        ScannerPublicationCommitState::AbortedBeforeCommit => save_result,
                         ScannerPublicationCommitState::Indeterminate
                         | ScannerPublicationCommitState::Admitted
                         | ScannerPublicationCommitState::InFlight => Err(EcstoreError::other(
                             "scanner publication commit scope did not reach a safe terminal state",
                         )),
-                    }
+                    };
+                    (result, Some(state))
                 } else {
-                    save_result
+                    (save_result, None)
                 }
             };
             done_save();
 
+            let attempt_confirmed = root_ack_write_is_confirmed(
+                &save_result,
+                commit_state,
+                save_result.as_ref().ok().and_then(|info| info.etag.as_deref()),
+            );
+
             match save_result {
                 Ok(object_info) => {
+                    write_confirmed = attempt_confirmed;
+                    written_etag = object_info.etag.as_ref().filter(|etag| !etag.is_empty()).cloned();
                     if !observational {
                         next_baseline = object_info
                             .etag
@@ -909,9 +1068,27 @@ where
                 break 'updates;
             }
         }
+        if !observational
+            && data_usage_info.usage_snapshot_converged == Some(true)
+            && matches!(outcome, DataUsagePersistOutcome::Saved | DataUsagePersistOutcome::AlreadyDurable)
+            && (outcome == DataUsagePersistOutcome::AlreadyDurable || write_confirmed)
+            && let (Some(expected), Some(epoch)) = (ack_expectation.as_ref(), ack_epoch)
+            && expected.matches_encoded_candidate(&data_digest)
+        {
+            proof = read_root_publication_proof(
+                storeapi.clone(),
+                &ctx,
+                ack_deadline,
+                epoch,
+                expected,
+                &data_usage_info,
+                written_etag.as_deref(),
+            )
+            .await;
+        }
     }
 
-    outcome
+    DataUsagePublicationResult { outcome, proof }
 }
 
 async fn cleanup_observed_data_usage_snapshot_for_epoch_and_lease(

crates/scanner/src/scanner_io.rs

@@ -114,6 +114,11 @@ pub(crate) struct ScannerBucketScanScope {
 }
 
 impl ScannerBucketScanScope {
+    #[cfg(test)]
+    pub(crate) fn selected_buckets_for_tests(&self) -> Option<&HashSet<String>> {
+        self.selected_buckets.as_deref()
+    }
+
     fn is_default(&self) -> bool {
         self.selected_buckets.is_none() && self.baseline_scan_plan_digest.is_none()
     }
@@ -218,8 +223,8 @@ fn complete_scanner_cache_snapshot_plan_digest(
 
 fn complete_scanner_cache_baseline_plan_digest(proof: ScannerCacheBaselineProof<'_>) -> Option<DataUsageScanPlanDigest> {
     let authoritative = serde_json::from_slice::<DataUsageInfo>(proof.authoritative_data?).ok()?;
-    if complete_scanner_cache_snapshot_plan_digest(&authoritative, proof, true).is_some() {
-        return Some(proof.scan_plan_digest);
+    if let Some(validated_digest) = complete_scanner_cache_snapshot_plan_digest(&authoritative, proof, true) {
+        return Some(validated_digest);
     }
 
     // A complete but superseded observation may reuse its per-set cache only
@@ -896,6 +901,7 @@ pub(crate) struct ScannerCycleResult {
     failed_dirty_usage: bool,
     pending_maintenance_work: bool,
     required_cycle_floor: Option<u64>,
+    publication_expectation: Option<ScannerPublicationExpectation>,
 }
 
 impl ScannerCycleResult {
@@ -911,10 +917,12 @@ impl ScannerCycleResult {
             failed_dirty_usage: false,
             pending_maintenance_work: false,
             required_cycle_floor: None,
+            publication_expectation: None,
         }
     }
 
     pub(crate) fn with_publication_epoch(mut self, publication_epoch: Option<u64>) -> Self {
+        self.publication_expectation = None;
         self.publication_epoch = publication_epoch;
         self
     }
@@ -924,6 +932,7 @@ impl ScannerCycleResult {
     }
 
     fn with_activity_digest(mut self, activity_digest: [u8; 32]) -> Self {
+        self.publication_expectation = None;
         self.activity_digest = Some(activity_digest);
         self
     }
@@ -933,6 +942,7 @@ impl ScannerCycleResult {
     }
 
     pub(crate) fn with_observational_snapshot_published(mut self, published: bool) -> Self {
+        self.publication_expectation = None;
         self.observational_snapshot_published = published;
         self
     }
@@ -942,16 +952,19 @@ impl ScannerCycleResult {
     }
 
     fn with_failed_dirty_usage(mut self, failed_dirty_usage: bool) -> Self {
+        self.publication_expectation = None;
         self.failed_dirty_usage = failed_dirty_usage;
         self
     }
 
     fn with_pending_maintenance_work(mut self, pending_maintenance_work: bool) -> Self {
+        self.publication_expectation = None;
         self.pending_maintenance_work = pending_maintenance_work;
         self
     }
 
     fn with_required_cycle_floor(mut self, required_cycle_floor: Option<u64>) -> Self {
+        self.publication_expectation = None;
         self.required_cycle_floor = required_cycle_floor;
         self
     }
@@ -960,11 +973,13 @@ impl ScannerCycleResult {
         mut self,
         acknowledgements: Vec<crate::scanner::ScannerDirtyUsageAcknowledgement>,
     ) -> Self {
+        self.publication_expectation = None;
         self.remote_dirty_usage_acknowledgements = acknowledgements;
         self
     }
 
     pub(crate) fn with_remote_publication_lease_targets(mut self, targets: Vec<(String, String, u64)>) -> Self {
+        self.publication_expectation = None;
         self.remote_publication_lease_targets = targets;
         self
     }
@@ -973,7 +988,32 @@ impl ScannerCycleResult {
         &self.remote_publication_lease_targets
     }
 
-    pub(crate) fn acknowledge_durable_usage(self) -> Vec<crate::scanner::ScannerDirtyUsageAcknowledgement> {
+    pub(crate) fn publication_expectation(&self) -> Option<ScannerPublicationExpectation> {
+        self.publication_expectation.clone()
+    }
+
+    fn with_publication_expectation(mut self, expectation: Option<ScannerPublicationExpectation>) -> Self {
+        // Seal only after all coverage and acknowledgement inputs are final.
+        self.publication_expectation = expectation;
+        self
+    }
+
+    pub(crate) fn acknowledge_durable_usage(
+        self,
+        proof: &crate::scanner::RootPublicationProof,
+    ) -> Vec<crate::scanner::ScannerDirtyUsageAcknowledgement> {
+        if self.status != ScannerCycleStatus::Complete
+            || self
+                .publication_expectation
+                .as_ref()
+                .is_none_or(|expected| proof.verified_version_for(expected).is_none())
+        {
+            return Vec::new();
+        }
+        self.clear_verified_usage()
+    }
+
+    fn clear_verified_usage(self) -> Vec<crate::scanner::ScannerDirtyUsageAcknowledgement> {
         if let Some(snapshot) = self.dirty_usage_clear {
             clear_dirty_usage_buckets(&snapshot);
         }
@@ -1013,6 +1053,7 @@ mod publish_gate_tests;
 #[cfg(test)]
 mod tests;
 
+pub(crate) use cache::ScannerPublicationExpectation;
 use cache::*;
 use dirty_usage::*;
 use guards::*;

crates/scanner/src/scanner_io/cache.rs

@@ -308,6 +308,86 @@ impl<'a> ValidatedScannerSnapshot<'a> {
     }
 }
 
+#[derive(Clone, Debug)]
+pub(crate) struct ScannerPublicationExpectation {
+    candidate: Arc<([u8; 32], DataUsageScanPlanDigest)>,
+}
+
+impl ScannerPublicationExpectation {
+    pub(crate) fn matches_encoded_candidate(&self, digest: &[u8; 32]) -> bool {
+        &self.candidate.0 == digest
+    }
+
+    pub(crate) fn same_candidate(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.candidate, &other.candidate) && self.candidate.1 == other.candidate.1
+    }
+}
+
+pub(super) struct ValidatedUsageCandidate {
+    data: DataUsageInfo,
+    #[cfg(test)]
+    last_update: SystemTime,
+    coverage_digest: DataUsageScanPlanDigest,
+}
+
+pub(super) fn empty_namespace_usage_candidate(
+    all_buckets: &[BucketInfo],
+    sources: &HashSet<DataUsageCacheSource>,
+    buckets_by_source: &HashMap<DataUsageCacheSource, Vec<BucketInfo>>,
+    identity: ScannerSnapshotIdentity,
+) -> Option<ValidatedUsageCandidate> {
+    if !all_buckets.is_empty()
+        || sources.is_empty()
+        || sources.len() != buckets_by_source.len()
+        || sources
+            .iter()
+            .any(|source| buckets_by_source.get(source).is_none_or(|buckets| !buckets.is_empty()))
+    {
+        return None;
+    }
+    let last_update = SystemTime::now();
+    Some(ValidatedUsageCandidate {
+        data: DataUsageInfo {
+            last_update: Some(last_update),
+            scanner_cycle: Some(identity.cycle),
+            scanner_epoch: Some(identity.leader_epoch),
+            usage_snapshot_complete: true,
+            ..Default::default()
+        },
+        #[cfg(test)]
+        last_update,
+        coverage_digest: identity.coverage_digest,
+    })
+}
+
+impl ValidatedUsageCandidate {
+    pub(super) fn prepare(mut self, status: ScannerCycleStatus) -> (DataUsageInfo, Option<ScannerPublicationExpectation>) {
+        self.data.usage_snapshot_converged = Some(status == ScannerCycleStatus::Complete);
+        let expectation = if status == ScannerCycleStatus::Complete {
+            struct DigestWriter(Sha256);
+            impl std::io::Write for DigestWriter {
+                fn write(&mut self, bytes: &[u8]) -> std::io::Result<usize> {
+                    self.0.update(bytes);
+                    Ok(bytes.len())
+                }
+                fn flush(&mut self) -> std::io::Result<()> {
+                    Ok(())
+                }
+            }
+            let mut writer = DigestWriter(Sha256::new());
+            serde_json::to_writer(&mut writer, &self.data)
+                .ok()
+                .map(|()| ScannerPublicationExpectation {
+                    candidate: Arc::new((writer.0.finalize().into(), self.coverage_digest)),
+                })
+        } else {
+            None
+        };
+        (self.data, expectation)
+    }
+}
+
+#[cfg(test)]
 pub(super) fn completed_data_usage_info(
     results: &[DataUsageCache],
     scope: &ScannerSnapshotScope<'_>,
@@ -316,6 +396,18 @@ pub(super) fn completed_data_usage_info(
     budget_elapsed: bool,
     cancelled: bool,
 ) -> Option<(DataUsageInfo, SystemTime)> {
+    completed_usage_candidate(results, scope, tier_registry_names, bucket_plan_complete, budget_elapsed, cancelled)
+        .map(|candidate| (candidate.data, candidate.last_update))
+}
+
+pub(super) fn completed_usage_candidate(
+    results: &[DataUsageCache],
+    scope: &ScannerSnapshotScope<'_>,
+    tier_registry_names: &[String],
+    bucket_plan_complete: bool,
+    budget_elapsed: bool,
+    cancelled: bool,
+) -> Option<ValidatedUsageCandidate> {
     if !bucket_plan_complete {
         return None;
     }
@@ -393,7 +485,12 @@ pub(super) fn completed_data_usage_info(
         usage_snapshot_set_states,
         ..Default::default()
     };
-    Some((data_usage_info, merged_last_update))
+    Some(ValidatedUsageCandidate {
+        data: data_usage_info,
+        #[cfg(test)]
+        last_update: merged_last_update,
+        coverage_digest: scope.identity.coverage_digest,
+    })
 }
 
 fn tier_accounting_proof_is_publishable(

crates/scanner/src/scanner_io/io_cycle.rs

@@ -338,12 +338,21 @@ where
             dirty_usage_status,
             activity_status,
         );
-        let empty_usage = DataUsageInfo {
-            last_update: Some(SystemTime::now()),
-            scanner_cycle: Some(want_cycle),
-            usage_snapshot_complete: true,
-            ..Default::default()
+        let Some(candidate) = empty_namespace_usage_candidate(
+            &all_buckets,
+            &expected_sources,
+            &buckets_by_source,
+            ScannerSnapshotIdentity {
+                cycle: want_cycle,
+                leader_epoch,
+                plan_digest: scan_plan_digest,
+                coverage_digest: bucket_coverage_digest,
+                tier_registry_generation: Some(tier_registry_generation),
+            },
+        ) else {
+            return Ok(ScannerCycleResult::new(ScannerCycleStatus::Incomplete, None).with_publication_epoch(publication_epoch));
         };
+        let (empty_usage, publication_expectation) = candidate.prepare(status);
         let observational_snapshot_published = if should_publish_observational_snapshot(status) {
             publish_observational_snapshot(&updates, empty_usage).await?
         } else {
@@ -366,7 +375,8 @@ where
             .with_activity_digest(activity_digest)
             .with_observational_snapshot_published(observational_snapshot_published)
             .with_remote_publication_lease_targets(remote_publication_lease_targets)
-            .with_remote_dirty_usage_acknowledgements(remote_dirty_usage_acknowledgements));
+            .with_remote_dirty_usage_acknowledgements(remote_dirty_usage_acknowledgements)
+            .with_publication_expectation(publication_expectation));
     }
 
     let total_results = expected_sources.len();
@@ -595,7 +605,7 @@ where
     let (activity_status, remote_publication_lease_targets) =
         scanner_cycle_activity_status(store, distributed, &activity_before).await;
     let all_bucket_names = all_buckets.iter().map(|bucket| bucket.name.clone()).collect::<Vec<_>>();
-    let completed_usage = completed_data_usage_info(
+    let completed_usage = completed_usage_candidate(
         &results,
         &ScannerSnapshotScope {
             sources: &expected_sources,
@@ -636,7 +646,10 @@ where
         dirty_usage_status,
         activity_status,
     );
-    let observational_snapshot_published = if let Some((data_usage_info, _)) = completed_usage {
+    let mut publication_expectation = None;
+    let observational_snapshot_published = if let Some(candidate) = completed_usage {
+        let (data_usage_info, expectation) = candidate.prepare(cycle_status);
+        publication_expectation = expectation;
         if should_publish_observational_snapshot(cycle_status) {
             publish_observational_snapshot(&updates, data_usage_info).await?
         } else {
@@ -674,5 +687,6 @@ where
         .with_remote_dirty_usage_acknowledgements(remote_dirty_usage_acknowledgements)
         .with_failed_dirty_usage(!failed_buckets.is_empty())
         .with_pending_maintenance_work(pending_maintenance_work)
-        .with_required_cycle_floor(required_cycle_floor))
+        .with_required_cycle_floor(required_cycle_floor)
+        .with_publication_expectation(publication_expectation))
 }

crates/scanner/src/scanner_io/tests.rs

@@ -454,6 +454,7 @@ async fn scoped_scan_same_cycle_maintenance_rewalks_after_root_delivery_failure(
                 .await
                 .expect("initial object should persist");
         }
+        wait_for_namespace_commit_tails(&store).await;
         let ctx = CancellationToken::new();
         let budget = ScannerCycleBudget::new(&ctx, ScannerCycleBudgetConfig::default());
         let (updates, receiver) = mpsc::channel(1);
@@ -503,6 +504,7 @@ async fn scoped_scan_same_cycle_maintenance_rewalks_after_root_delivery_failure(
             .put_object("cold-bucket", "new", &mut reader, &ScannerObjectOptions::default())
             .await
             .expect("new cold object should persist");
+        wait_for_namespace_commit_tails(&store).await;
         record_dirty_usage_bucket("hot-bucket");
         if scan_mode == HealScanMode::Normal && !requires_full_scan {
             record_dirty_usage_bucket("cold-bucket");
@@ -994,8 +996,8 @@ fn dirty_usage_snapshot_clears_a_stably_absent_bucket_after_durable_save() {
     assert!(dirty_usage_buckets().contains_key("temporarily-omitted"));
     assert_eq!(dirty_usage_snapshot_status(&snapshot), DirtyUsageSnapshotStatus::Current);
 
-    let acknowledgements = ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(snapshot.buckets.as_ref().clone()))
-        .acknowledge_durable_usage();
+    let acknowledgements =
+        ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(snapshot.buckets.as_ref().clone())).clear_verified_usage();
     assert!(acknowledgements.is_empty());
     assert!(!dirty_usage_buckets().contains_key("temporarily-omitted"));
     clear_dirty_usage_buckets_for_tests();
@@ -1101,7 +1103,7 @@ fn dirty_usage_is_acknowledged_only_after_durable_usage_confirmation() {
     assert!(dirty_usage_buckets().contains_key("photos"));
 
     let confirmed = ScannerCycleResult::new(ScannerCycleStatus::Complete, Some(snapshot.buckets.as_ref().clone()));
-    let acknowledgements = confirmed.acknowledge_durable_usage();
+    let acknowledgements = confirmed.clear_verified_usage();
     assert!(acknowledgements.is_empty());
     assert!(!dirty_usage_buckets().contains_key("photos"));
     clear_dirty_usage_buckets_for_tests();