diff --git a/src/Backend/SolutionErp.Infrastructure/Services/ContractWorkflowService.cs b/src/Backend/SolutionErp.Infrastructure/Services/ContractWorkflowService.cs
index a4cce4f..1da58ad 100644
--- a/src/Backend/SolutionErp.Infrastructure/Services/ContractWorkflowService.cs
+++ b/src/Backend/SolutionErp.Infrastructure/Services/ContractWorkflowService.cs
@@ -279,18 +279,46 @@ public class ContractWorkflowService(
             ApprovedAt = dateTime.UtcNow,
         });
 
-        // TODO Plan B Chunk C: UPSERT ContractLevelOpinion vào row Level chính
-        // chủ (mirror PE Mig 26 / line 512-546). Bảng + entity chưa có (Chunk C
-        // Implementer sẽ scaffold Mig 33). Block UPSERT add ở đây sau Chunk C
-        // done. Hiện tại Section 5 FE sẽ KHÔNG hiển thị opinion comment per
-        // Level — sẽ wire khi Chunk E (FE Section 5 LevelOpinionsV2).
+        // [Plan B Chunk B2 S29 2026-05-22] UPSERT ContractLevelOpinion vào row
+        // Level chính chủ (mirror PE Mig 26 line 512-546). Section 5 FE render
+        // dynamic theo flow.steps[].levels[]. Comment khi duyệt auto sync sang
+        // Section 5 (read-only summary). Empty comment → "(duyệt — không ý kiến)"
+        // placeholder. Multi-NV cùng Cấp (OR-of-N): match level theo
+        // ApproverUserId. Admin override → fallback first level group; FE detect
+        // SignedByUserId !== Level.ApproverUserId → banner "Admin duyệt thay".
+        var matchingLevel = pendingLevelGroup.FirstOrDefault(l => actorUserId.HasValue && l.ApproverUserId == actorUserId.Value)
+                            ?? pendingLevelGroup.First();
+        var actorFullName = await ResolveActorFullNameAsync(actorUserId, isSystem, ct);
+        var existingOpinion = await db.ContractLevelOpinions
+            .FirstOrDefaultAsync(o => o.ContractId == contract.Id
+                && o.ApprovalWorkflowLevelId == matchingLevel.Id, ct);
+        var normalizedComment = string.IsNullOrWhiteSpace(comment)
+            ? "(duyệt — không ý kiến)"
+            : comment.Trim();
+        if (existingOpinion is null)
+        {
+            db.ContractLevelOpinions.Add(new ContractLevelOpinion
+            {
+                ContractId = contract.Id,
+                ApprovalWorkflowLevelId = matchingLevel.Id,
+                Comment = normalizedComment,
+                SignedAt = dateTime.UtcNow,
+                SignedByUserId = actorUserId ?? Guid.Empty,
+                SignedByFullName = actorFullName,
+            });
+        }
+        else
+        {
+            existingOpinion.Comment = normalizedComment;
+            existingOpinion.SignedAt = dateTime.UtcNow;
+            existingOpinion.SignedByUserId = actorUserId ?? Guid.Empty;
+            existingOpinion.SignedByFullName = actorFullName;
+        }
 
         // skipToFinal F2 (Mig 31 Plan K S23) — Approver scope ChoDuyet skip
         // thẳng Cấp cuối. Admin opt-in per slot tại AllowApproverSkipToFinal.
         if (skipToFinal)
         {
-            var matchingLevel = pendingLevelGroup.FirstOrDefault(l => actorUserId.HasValue && l.ApproverUserId == actorUserId.Value)
-                                ?? pendingLevelGroup.First();
             if (!isAdmin && !isSystem && !matchingLevel.AllowApproverSkipToFinal)
             {
                 throw new ConflictException(
@@ -398,4 +426,18 @@ public class ContractWorkflowService(
                 ct: ct);
         }
     }
+
+    // [Plan B Chunk B2 S29 2026-05-22] Resolve actor full name for
+    // ContractLevelOpinion.SignedByFullName denormalized field (Section 5 FE
+    // display). Mirror PE PurchaseEvaluationWorkflowService.cs:774-783.
+    private async Task<string> ResolveActorFullNameAsync(Guid? actorUserId, bool isSystem, CancellationToken ct)
+    {
+        if (isSystem || actorUserId is null) return "(System)";
+        var user = await db.Users.AsNoTracking()
+            .Where(u => u.Id == actorUserId.Value)
+            .Select(u => new { u.FullName, u.UserName })
+            .FirstOrDefaultAsync(ct);
+        if (user is null) return "(unknown)";
+        return !string.IsNullOrWhiteSpace(user.FullName) ? user.FullName : (user.UserName ?? "(unknown)");
+    }
 }