diff --git a/aw-sync/src/sync.rs b/aw-sync/src/sync.rs
index 69d811f7..aef36647 100644
--- a/aw-sync/src/sync.rs
+++ b/aw-sync/src/sync.rs
@@ -547,6 +547,69 @@ fn get_or_create_sync_bucket(
             Err(e) => return Err(format!("Failed to get bucket '{sanitized_id}': {e:?}")),
         }
     }
+
+    // Pre-#697 origin-based fallback (ActivityWatch/aw-server-rust#707):
+    // Both exact lookups missed.  A desktop that imported the peer before
+    // ActivityWatch/aw-server-rust#697 landed holds the raw hostname from that
+    // day (e.g. `…-synced-from-POCO F8 Ultra`) with `$aw.sync.origin` set to
+    // that same raw value.  After ActivityWatch/aw-android#273 migrates the
+    // phone's staging hostname to `poco_f8_ultra`, first-hand buckets carry no
+    // `$aw.sync.origin`, so both lookups above miss and the whole history gets
+    // re-imported.  Scan the destination's -synced-from- buckets for one whose
+    // base ID matches and whose `$aw.sync.origin` sanitizes to the same target.
+    if !is_push {
+        let target_base = bucket_from
+            .id
+            .split("-synced-from-")
+            .next()
+            .unwrap_or(bucket_from.id.as_str());
+        let target_sanitized = sanitize_hostname(
+            sync_origin
+                .as_deref()
+                .unwrap_or(bucket_from.hostname.as_str()),
+        );
+        let all_dest = ds_to
+            .get_buckets()
+            .map_err(|e| format!("Failed to list dest buckets for origin scan: {e:?}"))?;
+        let mut candidates: Vec<Bucket> = all_dest
+            .into_values()
+            .filter(|b| {
+                let b_base = b.id.split("-synced-from-").next().unwrap_or(&b.id);
+                if b_base != target_base {
+                    return false;
+                }
+                // $aw.sync.origin must be present and sanitize to the same value.
+                b.data
+                    .get("$aw.sync.origin")
+                    .and_then(|v| v.as_str())
+                    .map(|s| sanitize_hostname(s) == target_sanitized)
+                    .unwrap_or(false)
+            })
+            .collect();
+        match candidates.len() {
+            0 => {} // fall through to create a new bucket
+            1 => {
+                let found = candidates.remove(0);
+                info!(
+                    "   ↩  Reusing pre-#697 bucket '{}' for '{}'",
+                    found.id, bucket_from.id
+                );
+                return Ok(found);
+            }
+            n => {
+                // Two distinct pre-#697 buckets share the same sanitized origin —
+                // ambiguous.  Refuse rather than silently merging distinct histories
+                // (ActivityWatch/aw-server-rust#697 :368).
+                let ids: Vec<&str> = candidates.iter().map(|b| b.id.as_str()).collect();
+                return Err(format!(
+                    "Cannot resolve destination for '{}': {n} pre-#697 buckets share \
+                     sanitized origin '{}': {ids:?}; deduplicate manually",
+                    bucket_from.id, target_sanitized
+                ));
+            }
+        }
+    }
+
     let (final_id, final_hostname) = (sanitized_id, sanitized_hostname);
 
     let mut bucket_new = bucket_from.clone();
diff --git a/aw-sync/tests/sync.rs b/aw-sync/tests/sync.rs
index d4e02669..14b46f3d 100644
--- a/aw-sync/tests/sync.rs
+++ b/aw-sync/tests/sync.rs
@@ -261,6 +261,246 @@ mod sync_tests {
         );
     }
 
+    /// A desktop that imported the peer **before** ActivityWatch/aw-server-rust#697
+    /// landed holds `…-synced-from-POCO F8 Ultra` (raw, with `$aw.sync.origin` set
+    /// to the raw value by #697's import stamp).  After ActivityWatch/aw-android#273
+    /// migrates the phone's hostname to `poco_f8_ultra`, first-hand buckets carry no
+    /// `$aw.sync.origin`, so the two direct lookups miss.  The pre-#697 fallback scan
+    /// must find the legacy bucket and resume from it rather than creating a new one
+    /// that triggers a full re-import.
+    #[test]
+    fn test_pre697_origin_scan_resumes_legacy_bucket() {
+        let state = init_teststate();
+
+        // Post-migration phone bucket: sanitized hostname, no $aw.sync.origin.
+        let src_bucket: Bucket = serde_json::from_value(serde_json::json!({
+            "id": "aw-watcher-android",
+            "type": "currentwindow",
+            "hostname": "poco_f8_ultra",
+            "client": "aw-android"
+        }))
+        .unwrap();
+        state.ds_src.create_bucket(&src_bucket).unwrap();
+
+        // Pre-#697 destination bucket: raw ID + $aw.sync.origin stamped by #697.
+        let legacy_id = "aw-watcher-android-synced-from-POCO F8 Ultra";
+        let legacy_bucket: Bucket = serde_json::from_value(serde_json::json!({
+            "id": legacy_id,
+            "type": "currentwindow",
+            "hostname": "POCO F8 Ultra",
+            "client": "aw-android",
+            "data": {"$aw.sync.origin": "POCO F8 Ultra"}
+        }))
+        .unwrap();
+        state.ds_dest.create_bucket(&legacy_bucket).unwrap();
+
+        // Seed the legacy destination bucket with one event at T0 — simulating
+        // previously-imported history.  This establishes the resume cursor.
+        let t0 = Utc::now();
+        let existing_event: Event = serde_json::from_value(serde_json::json!({
+            "timestamp": t0.to_rfc3339(),
+            "duration": 1,
+            "data": {"app": "existing"}
+        }))
+        .unwrap();
+        state
+            .ds_dest
+            .insert_events(legacy_id, &[existing_event])
+            .unwrap();
+        state.ds_dest.force_commit().unwrap();
+
+        // Two source events: one before T0 (already covered) and one after T0 (new).
+        // The sync must read the cursor from the reused bucket and import only the
+        // post-T0 event — not re-import everything from scratch.
+        let before_t0: Event = serde_json::from_value(serde_json::json!({
+            "timestamp": (t0 - Duration::hours(1)).to_rfc3339(),
+            "duration": 1,
+            "data": {"app": "old"}
+        }))
+        .unwrap();
+        let after_t0: Event = serde_json::from_value(serde_json::json!({
+            "timestamp": (t0 + Duration::hours(1)).to_rfc3339(),
+            "duration": 1,
+            "data": {"app": "new"}
+        }))
+        .unwrap();
+        state
+            .ds_src
+            .insert_events("aw-watcher-android", &[before_t0, after_t0])
+            .unwrap();
+        state.ds_src.force_commit().unwrap();
+
+        aw_sync::sync_datastores(
+            &state.ds_src,
+            &state.ds_dest,
+            false, // pull
+            None,
+            &SyncSpec::default(),
+        )
+        .unwrap();
+
+        let dest_buckets = state.ds_dest.get_buckets().unwrap();
+
+        // The legacy bucket must be reused, not replaced.
+        assert!(
+            dest_buckets.contains_key(legacy_id),
+            "legacy bucket must be preserved"
+        );
+        // No new sanitized fork must appear.
+        let forked_id = "aw-watcher-android-synced-from-poco_f8_ultra";
+        assert!(
+            !dest_buckets.contains_key(forked_id),
+            "a sanitized fork must not be created; got: {:?}",
+            dest_buckets.keys().collect::<Vec<_>>()
+        );
+        // Exactly 2 events: the pre-existing one at T0 plus the new T0+1h event.
+        // A count of 3 would mean the cursor was NOT read (full re-import from scratch).
+        let event_count = state
+            .ds_dest
+            .get_event_count(legacy_id, None, None)
+            .unwrap();
+        assert_eq!(
+            event_count, 2,
+            "legacy bucket must have exactly 2 events (existing + new); \
+             3 would mean the cursor was ignored and history was re-imported"
+        );
+    }
+
+    /// Two distinct pre-#697 buckets for the same base ID whose `$aw.sync.origin`
+    /// values sanitize to the same target must trigger an error rather than a
+    /// silent merge (ActivityWatch/aw-server-rust#697 :368).
+    #[test]
+    fn test_pre697_origin_scan_refuses_ambiguous_candidates() {
+        let state = init_teststate();
+
+        // Ambiguous source bucket: two pre-#697 destination buckets share the same
+        // sanitized origin — sync_one must skip this bucket with a warning, not abort.
+        let src_bucket: Bucket = serde_json::from_value(serde_json::json!({
+            "id": "aw-watcher-android",
+            "type": "currentwindow",
+            "hostname": "poco_f8_ultra",
+            "client": "aw-android"
+        }))
+        .unwrap();
+        state.ds_src.create_bucket(&src_bucket).unwrap();
+
+        // A second, healthy source bucket that must sync successfully even while the
+        // ambiguous bucket is being skipped — one unresolvable bucket must not abort
+        // the whole peer sync.
+        let healthy_id = "aw-watcher-window";
+        let healthy_bucket: Bucket = serde_json::from_value(serde_json::json!({
+            "id": healthy_id,
+            "type": "currentwindow",
+            "hostname": "poco_f8_ultra",
+            "client": "aw-qt"
+        }))
+        .unwrap();
+        state.ds_src.create_bucket(&healthy_bucket).unwrap();
+
+        let ts = Utc::now();
+        let ev: Event = serde_json::from_value(serde_json::json!({
+            "timestamp": ts.to_rfc3339(),
+            "duration": 1,
+            "data": {"app": "test"}
+        }))
+        .unwrap();
+        state.ds_src.insert_events(healthy_id, &[ev]).unwrap();
+
+        // The ambiguous bucket must ALSO carry an event. Otherwise a regression that
+        // silently reused one of the two legacy candidates would copy nothing, both
+        // legacy buckets would still read 0 events, and the refusal assertions below
+        // would pass vacuously. With a real event present, only an actual skip keeps
+        // them at 0.
+        let ev_ambiguous: Event = serde_json::from_value(serde_json::json!({
+            "timestamp": ts.to_rfc3339(),
+            "duration": 1,
+            "data": {"app": "ambiguous"}
+        }))
+        .unwrap();
+        state
+            .ds_src
+            .insert_events(&src_bucket.id, &[ev_ambiguous])
+            .unwrap();
+        state.ds_src.force_commit().unwrap();
+
+        // Premise guard: the refusal assertions below are only meaningful if the
+        // ambiguous source bucket actually has something to copy.
+        assert_eq!(
+            state
+                .ds_src
+                .get_event_count(&src_bucket.id, None, None)
+                .unwrap(),
+            1,
+            "premise: the ambiguous source bucket must carry one event"
+        );
+
+        // Two legacy destination buckets whose origins both sanitize to "poco_f8_ultra".
+        for (legacy_id, raw_origin) in [
+            (
+                "aw-watcher-android-synced-from-POCO F8 Ultra",
+                "POCO F8 Ultra",
+            ),
+            (
+                "aw-watcher-android-synced-from-Poco F8 Ultra",
+                "Poco F8 Ultra",
+            ),
+        ] {
+            let b: Bucket = serde_json::from_value(serde_json::json!({
+                "id": legacy_id,
+                "type": "currentwindow",
+                "hostname": raw_origin,
+                "client": "aw-android",
+                "data": {"$aw.sync.origin": raw_origin}
+            }))
+            .unwrap();
+            state.ds_dest.create_bucket(&b).unwrap();
+        }
+
+        // The ambiguous android bucket is skipped (warn+continue); the healthy window
+        // bucket syncs normally.  sync_datastores must return Ok overall.
+        aw_sync::sync_datastores(
+            &state.ds_src,
+            &state.ds_dest,
+            false, // pull
+            None,
+            &SyncSpec::default(),
+        )
+        .unwrap();
+
+        let dest_buckets = state.ds_dest.get_buckets().unwrap();
+
+        // The healthy bucket was synced — it has a destination and received events.
+        let healthy_dest_id = "aw-watcher-window-synced-from-poco_f8_ultra";
+        assert!(
+            dest_buckets.contains_key(healthy_dest_id),
+            "healthy bucket must be synced even when another bucket is ambiguous; got: {:?}",
+            dest_buckets.keys().collect::<Vec<_>>()
+        );
+        let healthy_count = state
+            .ds_dest
+            .get_event_count(healthy_dest_id, None, None)
+            .unwrap();
+        assert!(healthy_count > 0, "healthy bucket must have events synced");
+
+        // The two ambiguous legacy buckets were not written to — the conflict was
+        // skipped, not merged.  The source bucket holds an event (premise guard
+        // above), so a silent pick-one-candidate regression would make one of these
+        // counts 1 and fail here.
+        for legacy_id in [
+            "aw-watcher-android-synced-from-POCO F8 Ultra",
+            "aw-watcher-android-synced-from-Poco F8 Ultra",
+        ] {
+            let count = state
+                .ds_dest
+                .get_event_count(legacy_id, None, None)
+                .unwrap();
+            assert_eq!(
+                count, 0,
+                "ambiguous legacy bucket '{legacy_id}' must not have received events"
+            );
+        }
+    }
+
     /// Case-only hostnames (`PIXEL8`) have no whitespace, so a whitespace-only
     /// guard would leave the destination as `…-synced-from-PIXEL8`. Android's
     /// later hostname migration produces `pixel8` and forks the history.