diff --git a/orga/changelog/fix-replication-sent-deletedfield-format.md b/orga/changelog/fix-replication-sent-deletedfield-format.md
new file mode 100644
index 00000000000..dc45c59e31f
--- /dev/null
+++ b/orga/changelog/fix-replication-sent-deletedfield-format.md
@@ -0,0 +1 @@
+- FIX replication `sent$` observable emitting documents in the master format (with the user-defined `deletedField`) instead of the typed `WithDeleted<RxDocType>` format (with `_deleted: boolean`), because the `deletedField` swap mutated the same row object that was later forwarded to subscribers
diff --git a/src/plugins/replication/index.ts b/src/plugins/replication/index.ts
index 714b435fa96..9ab40a5fd66 100644
--- a/src/plugins/replication/index.ts
+++ b/src/plugins/replication/index.ts
@@ -321,11 +321,22 @@ export class RxReplicationState<RxDocType, CheckpointType> {
                             if (row.assumedMasterState) {
                                 row.assumedMasterState = await pushModifier(row.assumedMasterState);
                             }
+                            /**
+                             * The deletedField swap must not mutate the original row,
+                             * because that row is later forwarded to processed.up
+                             * which feeds sent$. sent$ is typed as
+                             * Observable<WithDeleted<RxDocType>> and must always emit
+                             * documents in the WithDeleted format with `_deleted: boolean`,
+                             * never the master-format `deletedField`.
+                             */
                             if (this.deletedField !== '_deleted') {
-                                row.newDocumentState = swapDefaultDeletedTodeletedField(this.deletedField, row.newDocumentState) as any;
-                                if (row.assumedMasterState) {
-                                    row.assumedMasterState = swapDefaultDeletedTodeletedField(this.deletedField, row.assumedMasterState) as any;
-                                }
+                                return {
+                                    ...row,
+                                    newDocumentState: swapDefaultDeletedTodeletedField(this.deletedField, row.newDocumentState) as any,
+                                    assumedMasterState: row.assumedMasterState
+                                        ? swapDefaultDeletedTodeletedField(this.deletedField, row.assumedMasterState) as any
+                                        : undefined
+                                };
                             }
                             return row;
                         })
diff --git a/test/unit/replication.test.ts b/test/unit/replication.test.ts
index 978e064e9f2..20d8a3127f0 100644
--- a/test/unit/replication.test.ts
+++ b/test/unit/replication.test.ts
@@ -334,6 +334,70 @@ describe('replication.test.ts', () => {
             localCollection.database.close();
             remoteCollection.database.close();
         });
+        it('sent$ must emit documents in WithDeleted format with _deleted field when deletedField is custom', async () => {
+            const localCollection = await humansCollection.createHumanWithTimestamp(0, randomToken(10), false);
+
+            // Prepare states before starting replication to avoid storage-specific
+            // intermediate emissions for insert-then-remove in a single run.
+            await localCollection.insert(schemaObjects.humanWithTimestampData({ id: 'alive' }));
+            const removeDoc = await localCollection.insert(schemaObjects.humanWithTimestampData({ id: 'to-remove' }));
+            await removeDoc.remove();
+
+            const pushedToMaster: any[] = [];
+            const replicationState = replicateRxCollection<HumanWithTimestampDocumentType, any>({
+                collection: localCollection,
+                replicationIdentifier: REPLICATION_IDENTIFIER_TEST,
+                deletedField: 'is_deleted',
+                live: false,
+                push: {
+                    handler: (rows) => {
+                        rows.forEach(row => pushedToMaster.push(row.newDocumentState));
+                        return Promise.resolve([]);
+                    }
+                }
+            });
+            ensureReplicationHasNoErrors(replicationState);
+
+            const sentDocs: WithDeleted<HumanWithTimestampDocumentType>[] = [];
+            replicationState.sent$.subscribe(d => sentDocs.push(d));
+
+            await replicationState.awaitInitialReplication();
+
+            // The push handler must receive the master format with `is_deleted` (not `_deleted`)
+            assert.ok(pushedToMaster.length >= 2, 'push handler must receive at least both docs');
+            pushedToMaster.forEach((doc) => {
+                assert.strictEqual(typeof doc.is_deleted, 'boolean', 'push handler must see is_deleted, got ' + JSON.stringify(doc));
+                assert.strictEqual((doc as any)._deleted, undefined, 'push handler must NOT see _deleted, got ' + JSON.stringify(doc));
+            });
+
+            // sent$ is typed as Observable<WithDeleted<RxDocType>>.
+            // It must always emit documents with `_deleted: boolean`,
+            // never the master-format `is_deleted` field.
+            assert.ok(sentDocs.length >= 2, 'sent$ must emit at least both docs, got ' + sentDocs.length);
+            sentDocs.forEach((doc, idx) => {
+                assert.strictEqual(
+                    typeof doc._deleted,
+                    'boolean',
+                    'sent$ doc at index ' + idx + ' must have _deleted: boolean, got ' + JSON.stringify(doc)
+                );
+                assert.strictEqual(
+                    (doc as any).is_deleted,
+                    undefined,
+                    'sent$ doc at index ' + idx + ' must NOT have is_deleted (master format), got ' + JSON.stringify(doc)
+                );
+            });
+
+            const aliveSent = ensureNotFalsy(sentDocs.find(d => (d as any).id === 'alive'));
+            const removedSent = sentDocs.filter(d => (d as any).id === 'to-remove');
+            assert.strictEqual(aliveSent._deleted, false, 'alive doc must have _deleted=false on sent$');
+            assert.ok(removedSent.length > 0, 'removed doc must be emitted on sent$');
+            assert.ok(
+                removedSent.some(doc => doc._deleted === true),
+                'removed doc must have _deleted=true on sent$'
+            );
+
+            await localCollection.database.close();
+        });
         it('should not save pulled documents that do not match the schema', async () => {
             const amount = 5;
             const { localCollection, remoteCollection } = await getTestCollections({ local: 0, remote: amount });