diff --git a/docs/plans/2026-06-16-ipsen-mes-movein-design.md b/docs/plans/2026-06-16-ipsen-mes-movein-design.md
index 7784f562..7b52b5af 100644
--- a/docs/plans/2026-06-16-ipsen-mes-movein-design.md
+++ b/docs/plans/2026-06-16-ipsen-mes-movein-design.md
@@ -74,16 +74,26 @@ receiver is ready to accept a MoveIn.
 ## 4. Components
 
 ### A. ScadaBridge source change — inbound read-only DB helper
-- New `InboundDatabaseHelper` backed by `IDatabaseGateway`, surface:
-  `T? QuerySingle<T>(string conn, string sql, object? args = null)` and
-  `IReadOnlyList<IReadOnlyDictionary<string, object?>> Query(string conn, string sql, object? args = null)`.
-  **No write methods.**
+- New `InboundDatabaseHelper` backed by `IDatabaseGateway`, surface (async — every call is
+  awaited and bound to the method deadline):
+  `Task<T?> QuerySingleAsync<T>(string conn, string sql, object? args = null)`,
+  `Task<IReadOnlyList<IReadOnlyDictionary<string, object?>>> QueryAsync(string conn, string sql, object? args = null)`,
+  and `Task<int> ExecuteAsync(string conn, string sql, object? args = null)` (writes are supported —
+  see the correction below).
 - Add `Database` property to `InboundScriptContext`; construct it in `InboundScriptExecutor`
   from a service scope (gateway is scoped). Add the helper's assembly to the script
   `ScriptOptions.WithReferences(...)` and confirm `ForbiddenApiChecker` still passes (the script
-  references only `Database.QuerySingle`, never `System.Data`).
+  references only `Database.QuerySingleAsync`, never `System.Data`).
 - Unit tests with a fake `IDatabaseGateway`.
 
+> **Correction (2026-06-25).** The shipped `InboundDatabaseHelper` is **async** —
+> `QuerySingleAsync<T>` / `QueryAsync` / `ExecuteAsync`, each `await`ed — not the synchronous
+> `QuerySingle`/`Query` sketched in the original draft above, and **writes are supported**
+> (InboundAPI-026) rather than read-only. Scripts MUST call `await Database.QuerySingleAsync<T>(...)`.
+> Three deployed methods (`IpsenMESMoveIn`, `MesMoveIn`, `MesMoveOut`) were authored from the old
+> `Database.QuerySingle` spelling and failed Roslyn compilation in production until corrected
+> (2026-06-25). The authoritative surface lives in `docs/requirements/Component-InboundAPI.md`.
+
 ### B. Rewrite inbound `/api/IpsenMESMoveIn` script (data, via management API)
 Pseudocode (always returns the 3-field shape; never throws out):
 ```csharp
@@ -96,7 +106,7 @@ try {
   var side = suf == "A" ? "Left" : suf == "B" ? "Right" : null;
   if (side == null) return new { WasSuccessful = false, ErrorText = $"Unsupported side '{suf}'", BatchID = 0 };
 
-  var code = Database.QuerySingle<string>("BTDB",
+  var code = await Database.QuerySingleAsync<string>("BTDB",
       "SELECT TOP 1 Code FROM dbo.Machine WHERE SAPID=@s", new { s = sap });
   if (string.IsNullOrEmpty(code)) return new { WasSuccessful = false, ErrorText = $"No machine for SAP {sap}", BatchID = 0 };