diff --git a/backend/src/routes/v1/admin.routes.ts b/backend/src/routes/v1/admin.routes.ts
index 253f112..f6427c7 100644
--- a/backend/src/routes/v1/admin.routes.ts
+++ b/backend/src/routes/v1/admin.routes.ts
@@ -222,7 +222,7 @@ router.post('/indexer/reset', async (req: Request, res: Response) => {
  * /v1/admin/indexer/replay:
  *   post:
  *     tags: [Admin]
- *     summary: Replay events from a given ledger (idempotent)
+ *     summary: Replay events from a given ledger (StreamEvent rows deduplicated; stream mutations not idempotent — see indexerService.ts JSDoc)
  *     security: [{ adminAuth: [] }]
  *     parameters:
  *       - in: query
diff --git a/backend/src/services/indexerService.ts b/backend/src/services/indexerService.ts
index 4dc6a2d..d386be4 100644
--- a/backend/src/services/indexerService.ts
+++ b/backend/src/services/indexerService.ts
@@ -38,8 +38,13 @@ export async function resetIndexer(toLedger: number): Promise<void> {
 
 /**
  * Replay events from a given ledger by resetting state and triggering a poll.
- * Deduplication in the worker (transactionHash + eventType + ledger) ensures
- * no duplicate StreamEvent rows are created.
+ * The @@unique([transactionHash, eventType]) constraint on StreamEvent
+ * guarantees no duplicate StreamEvent rows are created on replay.
+ *
+ * CAVEAT: This dedup does NOT apply to stream state mutations.
+ * Stream.withdrawnAmount (handleTokensWithdrawn, soroban-event-worker.ts:635)
+ * is incremented unconditionally on every replay, so replay is NOT fully
+ * idempotent. See issue #808 for the withdrawnAmount idempotency fix.
  */
 export async function replayFromLedger(fromLedger: number): Promise<void> {
   await resetIndexer(fromLedger);