diff --git a/docs/plans/2026-05-26-ibkr-flex-ingestion.md b/docs/plans/2026-05-26-ibkr-flex-ingestion.md
index 7a22578..1fa57bb 100644
--- a/docs/plans/2026-05-26-ibkr-flex-ingestion.md
+++ b/docs/plans/2026-05-26-ibkr-flex-ingestion.md
@@ -1461,8 +1461,10 @@ OpenPositions against WF-computed quantities.
 | Open Positions | symbol, position, markPrice, currency, assetCategory |
 | Securities Information | symbol, description, conid |
 
-Date range: `Last Business Day` for daily incremental. Switch to
-`Year to Date` for one-time backfills only.
+Date range: `Last 90 Days` — trailing window so a missed cron run
+doesn't lose data. SyncRecordStore makes overlapping pulls idempotent.
+Switch to `Year to Date` or `Custom Date Range` only for one-time
+historical backfills.
 
 ## Cash type mapping
 
diff --git a/docs/providers/ibkr.md b/docs/providers/ibkr.md
index a21df5b..501c641 100644
--- a/docs/providers/ibkr.md
+++ b/docs/providers/ibkr.md
@@ -39,8 +39,11 @@ a new query named `broker-sync-activity` with:
 
 **Date Format:** `yyyy-MM-dd`. **Time Format:** `HH:mm:ss` (no timezone
 suffix — ibflex 1.1 rejects timezone abbreviations in the time field).
-**Date Range:** `Last Business Day` for daily incremental. Switch to
-`Year to Date` only for one-off backfills.
+**Date Range:** `Last 90 Days` — trailing window so a missed cron run
+doesn't lose data. SyncRecordStore (keyed by `external_id`) makes
+overlapping pulls idempotent. For a one-off historical backfill, widen
+temporarily to `Year to Date` or `Custom Date Range`, run once, then
+switch back.
 
 ## Cash type mapping
 
diff --git a/docs/specs/2026-05-26-ibkr-ingest-design.md b/docs/specs/2026-05-26-ibkr-ingest-design.md
index 40bb9df..21aaf12 100644
--- a/docs/specs/2026-05-26-ibkr-ingest-design.md
+++ b/docs/specs/2026-05-26-ibkr-ingest-design.md
@@ -210,9 +210,12 @@ top.
    - Sections: `Account Information`, `Trades`, `Cash Transactions`,
      `Open Positions`, `Securities Information`
    - Date Format: `yyyy-MM-dd` · Time Format: `HH:mm:ss TimeZone`
-   - Date Range: `Last Business Day` (for daily runs; flip to
-     `Year to Date` only for the initial backfill — irrelevant while
-     account is empty)
+   - Date Range: `Last 90 Days` — trailing window so a missed cron run
+     (failed pod, outage, vacation) doesn't lose data. SyncRecordStore
+     keys on `ibkr:trade:<tradeID>` / `ibkr:cash:<transactionID>`, so
+     overlapping pulls are no-ops. `Last Business Day` was the original
+     choice but creates a "single missed run = permanent data loss"
+     failure mode — rejected in favour of dedup-backed resync window.
    - Format: XML
    - Trade fields: ensure `tradeID`, `tradeDate`, `tradeTime`, `symbol`,
      `buySell`, `quantity`, `tradePrice`, `currency`, `ibCommission`,
@@ -248,10 +251,13 @@ curl -sS -b /tmp/wf-jar -X POST "$WF_BASE_URL/api/v1/accounts" \
 
 ### Step 4 — Initial backfill (skip while account is empty)
 
-When the IBKR account first holds positions, switch the Flex query
-Date Range to `Year to Date`, run the CronJob manually once, verify WF
-totals match the broker app, then switch the Flex query back to
-`Last Business Day` for daily incremental.
+When the IBKR account first holds positions, the daily CronJob will
+backfill automatically up to the 90-day trailing window. For older
+history, temporarily switch the Flex query Date Range to
+`Year to Date` (or `Custom Date Range` with a 1-year window), run the
+CronJob manually once, verify WF totals match the broker app, then
+switch the Flex query back to `Last 90 Days` for daily incremental.
+Dedup makes the temporary widening safe — already-synced rows are no-ops.
 
 ### Step 5 — Deploy