diff --git a/fe-admin/src/components/pe/PeWorkflowPanel.tsx b/fe-admin/src/components/pe/PeWorkflowPanel.tsx
index 02e3ee9..9aa63de 100644
--- a/fe-admin/src/components/pe/PeWorkflowPanel.tsx
+++ b/fe-admin/src/components/pe/PeWorkflowPanel.tsx
@@ -45,12 +45,20 @@ export function PeWorkflowPanel({
   })
 
   const transition = useMutation({
-    mutationFn: async () =>
-      api.post(`/purchase-evaluations/${evaluation.id}/transitions`, {
+    mutationFn: async () => {
+      // Decision = Reject (2) khi:
+      //  - target = TuChoi (huỷ phiếu)
+      //  - target = DangSoanThao từ phase trung gian (= Trả lại — smart reject Mig 16
+      //    set RejectedFromPhase + clear N-stage rows + Drafter resume jump-back)
+      const isReject = target === PurchaseEvaluationPhase.TuChoi
+        || (target === PurchaseEvaluationPhase.DangSoanThao
+            && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao)
+      return api.post(`/purchase-evaluations/${evaluation.id}/transitions`, {
         targetPhase: target,
-        decision: target === PurchaseEvaluationPhase.TuChoi ? 2 : 1,
+        decision: isReject ? 2 : 1,
         comment: comment || null,
-      }),
+      })
+    },
     onSuccess: () => {
       toast.success('Đã chuyển phase.')
       qc.invalidateQueries({ queryKey: ['pe-detail', evaluation.id] })
@@ -101,22 +109,37 @@ export function PeWorkflowPanel({
 
       {next.length > 0 && !readOnly && (
         <div>
-          <Label className="text-xs">Chuyển tiếp:</Label>
+          <Label className="text-xs">Hành động:</Label>
           <div className="mt-1 flex flex-wrap gap-1.5">
-            {next.map(p => (
-              <button
-                key={p}
-                onClick={() => setTarget(p)}
-                className={cn(
-                  'rounded border px-2 py-1 text-[11px] transition',
-                  p === PurchaseEvaluationPhase.TuChoi
-                    ? 'border-red-200 text-red-700 hover:bg-red-50'
-                    : 'border-brand-300 text-brand-700 hover:bg-brand-50',
-                )}
-              >
-                → {PurchaseEvaluationPhaseLabel[p]}
-              </button>
-            ))}
+            {next.map(p => {
+              // Phân loại button theo hành động:
+              // - Trả lại = về DangSoanThao (từ phase trung gian) — red
+              // - Hủy/Từ chối = TuChoi (chỉ ở phase DangSoanThao đầu) — red
+              // - Duyệt = forward phase tiếp theo — brand
+              const isSendBack = p === PurchaseEvaluationPhase.DangSoanThao
+                && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao
+              const isCancel = p === PurchaseEvaluationPhase.TuChoi
+              const isDanger = isSendBack || isCancel
+              const label = isSendBack
+                ? '← Trả lại (về Drafter sửa)'
+                : isCancel
+                  ? '✗ Hủy / Từ chối'
+                  : `✓ Duyệt → ${PurchaseEvaluationPhaseLabel[p]}`
+              return (
+                <button
+                  key={p}
+                  onClick={() => setTarget(p)}
+                  className={cn(
+                    'rounded border px-2 py-1 text-[11px] font-medium transition',
+                    isDanger
+                      ? 'border-red-200 text-red-700 hover:bg-red-50'
+                      : 'border-brand-300 text-brand-700 hover:bg-brand-50',
+                  )}
+                >
+                  {label}
+                </button>
+              )
+            })}
           </div>
         </div>
       )}
@@ -126,20 +149,40 @@ export function PeWorkflowPanel({
         </div>
       )}
 
-      {target !== null && (
-        <Dialog
-          open
-          onClose={() => setTarget(null)}
-          title={`Chuyển → ${PurchaseEvaluationPhaseLabel[target]}`}
-          footer={<>
-            <Button variant="ghost" onClick={() => setTarget(null)}>Hủy</Button>
-            <Button onClick={() => transition.mutate()} disabled={transition.isPending}>Xác nhận</Button>
-          </>}
-        >
-          <Label>Ghi chú (tùy chọn)</Label>
-          <Textarea value={comment} onChange={e => setComment(e.target.value)} rows={3} />
-        </Dialog>
-      )}
+      {target !== null && (() => {
+        const isCancel = target === PurchaseEvaluationPhase.TuChoi
+        const isSendBack = target === PurchaseEvaluationPhase.DangSoanThao
+          && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao
+        const dialogTitle = isCancel
+          ? '✗ Từ chối phiếu (khoá hoàn toàn)'
+          : isSendBack
+            ? '← Trả lại Drafter sửa'
+            : `✓ Duyệt → ${PurchaseEvaluationPhaseLabel[target]}`
+        return (
+          <Dialog
+            open
+            onClose={() => setTarget(null)}
+            title={dialogTitle}
+            footer={<>
+              <Button variant="ghost" onClick={() => setTarget(null)}>Hủy</Button>
+              <Button onClick={() => transition.mutate()} disabled={transition.isPending}>Xác nhận</Button>
+            </>}
+          >
+            {isCancel && (
+              <div className="mb-3 rounded border border-red-200 bg-red-50 px-3 py-2 text-[11px] text-red-800">
+                ⚠ Phiếu sẽ bị khoá hoàn toàn (không edit/transition được nữa). Drafter cần tạo phiếu mới nếu muốn làm lại.
+              </div>
+            )}
+            {isSendBack && (
+              <div className="mb-3 rounded border border-amber-200 bg-amber-50 px-3 py-2 text-[11px] text-amber-800">
+                Phiếu sẽ về &ldquo;Đang soạn thảo&rdquo;. Drafter có thể sửa rồi trình lại — workflow tự jump tới phase này.
+              </div>
+            )}
+            <Label>Ghi chú (tùy chọn)</Label>
+            <Textarea value={comment} onChange={e => setComment(e.target.value)} rows={3} />
+          </Dialog>
+        )
+      })()}
 
       {deptApprovals.length > 0 && (
         <div className="border-t border-slate-200 pt-4">
diff --git a/fe-user/src/components/pe/PeWorkflowPanel.tsx b/fe-user/src/components/pe/PeWorkflowPanel.tsx
index 02e3ee9..9aa63de 100644
--- a/fe-user/src/components/pe/PeWorkflowPanel.tsx
+++ b/fe-user/src/components/pe/PeWorkflowPanel.tsx
@@ -45,12 +45,20 @@ export function PeWorkflowPanel({
   })
 
   const transition = useMutation({
-    mutationFn: async () =>
-      api.post(`/purchase-evaluations/${evaluation.id}/transitions`, {
+    mutationFn: async () => {
+      // Decision = Reject (2) khi:
+      //  - target = TuChoi (huỷ phiếu)
+      //  - target = DangSoanThao từ phase trung gian (= Trả lại — smart reject Mig 16
+      //    set RejectedFromPhase + clear N-stage rows + Drafter resume jump-back)
+      const isReject = target === PurchaseEvaluationPhase.TuChoi
+        || (target === PurchaseEvaluationPhase.DangSoanThao
+            && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao)
+      return api.post(`/purchase-evaluations/${evaluation.id}/transitions`, {
         targetPhase: target,
-        decision: target === PurchaseEvaluationPhase.TuChoi ? 2 : 1,
+        decision: isReject ? 2 : 1,
         comment: comment || null,
-      }),
+      })
+    },
     onSuccess: () => {
       toast.success('Đã chuyển phase.')
       qc.invalidateQueries({ queryKey: ['pe-detail', evaluation.id] })
@@ -101,22 +109,37 @@ export function PeWorkflowPanel({
 
       {next.length > 0 && !readOnly && (
         <div>
-          <Label className="text-xs">Chuyển tiếp:</Label>
+          <Label className="text-xs">Hành động:</Label>
           <div className="mt-1 flex flex-wrap gap-1.5">
-            {next.map(p => (
-              <button
-                key={p}
-                onClick={() => setTarget(p)}
-                className={cn(
-                  'rounded border px-2 py-1 text-[11px] transition',
-                  p === PurchaseEvaluationPhase.TuChoi
-                    ? 'border-red-200 text-red-700 hover:bg-red-50'
-                    : 'border-brand-300 text-brand-700 hover:bg-brand-50',
-                )}
-              >
-                → {PurchaseEvaluationPhaseLabel[p]}
-              </button>
-            ))}
+            {next.map(p => {
+              // Phân loại button theo hành động:
+              // - Trả lại = về DangSoanThao (từ phase trung gian) — red
+              // - Hủy/Từ chối = TuChoi (chỉ ở phase DangSoanThao đầu) — red
+              // - Duyệt = forward phase tiếp theo — brand
+              const isSendBack = p === PurchaseEvaluationPhase.DangSoanThao
+                && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao
+              const isCancel = p === PurchaseEvaluationPhase.TuChoi
+              const isDanger = isSendBack || isCancel
+              const label = isSendBack
+                ? '← Trả lại (về Drafter sửa)'
+                : isCancel
+                  ? '✗ Hủy / Từ chối'
+                  : `✓ Duyệt → ${PurchaseEvaluationPhaseLabel[p]}`
+              return (
+                <button
+                  key={p}
+                  onClick={() => setTarget(p)}
+                  className={cn(
+                    'rounded border px-2 py-1 text-[11px] font-medium transition',
+                    isDanger
+                      ? 'border-red-200 text-red-700 hover:bg-red-50'
+                      : 'border-brand-300 text-brand-700 hover:bg-brand-50',
+                  )}
+                >
+                  {label}
+                </button>
+              )
+            })}
           </div>
         </div>
       )}
@@ -126,20 +149,40 @@ export function PeWorkflowPanel({
         </div>
       )}
 
-      {target !== null && (
-        <Dialog
-          open
-          onClose={() => setTarget(null)}
-          title={`Chuyển → ${PurchaseEvaluationPhaseLabel[target]}`}
-          footer={<>
-            <Button variant="ghost" onClick={() => setTarget(null)}>Hủy</Button>
-            <Button onClick={() => transition.mutate()} disabled={transition.isPending}>Xác nhận</Button>
-          </>}
-        >
-          <Label>Ghi chú (tùy chọn)</Label>
-          <Textarea value={comment} onChange={e => setComment(e.target.value)} rows={3} />
-        </Dialog>
-      )}
+      {target !== null && (() => {
+        const isCancel = target === PurchaseEvaluationPhase.TuChoi
+        const isSendBack = target === PurchaseEvaluationPhase.DangSoanThao
+          && evaluation.phase !== PurchaseEvaluationPhase.DangSoanThao
+        const dialogTitle = isCancel
+          ? '✗ Từ chối phiếu (khoá hoàn toàn)'
+          : isSendBack
+            ? '← Trả lại Drafter sửa'
+            : `✓ Duyệt → ${PurchaseEvaluationPhaseLabel[target]}`
+        return (
+          <Dialog
+            open
+            onClose={() => setTarget(null)}
+            title={dialogTitle}
+            footer={<>
+              <Button variant="ghost" onClick={() => setTarget(null)}>Hủy</Button>
+              <Button onClick={() => transition.mutate()} disabled={transition.isPending}>Xác nhận</Button>
+            </>}
+          >
+            {isCancel && (
+              <div className="mb-3 rounded border border-red-200 bg-red-50 px-3 py-2 text-[11px] text-red-800">
+                ⚠ Phiếu sẽ bị khoá hoàn toàn (không edit/transition được nữa). Drafter cần tạo phiếu mới nếu muốn làm lại.
+              </div>
+            )}
+            {isSendBack && (
+              <div className="mb-3 rounded border border-amber-200 bg-amber-50 px-3 py-2 text-[11px] text-amber-800">
+                Phiếu sẽ về &ldquo;Đang soạn thảo&rdquo;. Drafter có thể sửa rồi trình lại — workflow tự jump tới phase này.
+              </div>
+            )}
+            <Label>Ghi chú (tùy chọn)</Label>
+            <Textarea value={comment} onChange={e => setComment(e.target.value)} rows={3} />
+          </Dialog>
+        )
+      })()}
 
       {deptApprovals.length > 0 && (
         <div className="border-t border-slate-200 pt-4">
diff --git a/src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationPolicy.cs b/src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationPolicy.cs
index b6faed8..67a8d2b 100644
--- a/src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationPolicy.cs
+++ b/src/Backend/SolutionErp.Domain/PurchaseEvaluations/PurchaseEvaluationPolicy.cs
@@ -56,14 +56,20 @@ public static class PurchaseEvaluationPolicies
             [(PurchaseEvaluationPhase.DangSoanThao, PurchaseEvaluationPhase.ChoPurchasing)] = [AppRoles.Drafter, AppRoles.DeptManager],
             [(PurchaseEvaluationPhase.DangSoanThao, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Drafter, AppRoles.DeptManager],
 
+            // Phase trung gian: 3 hành động — Duyệt forward / Trả lại Drafter (DangSoanThao) / Từ chối hoàn toàn (TuChoi).
+            // Trả lại = smart reject pattern Mig 16 (set RejectedFromPhase + về DangSoanThao + Drafter sửa).
+            // Từ chối = phiếu khoá hoàn toàn (Phase=TuChoi → 17 handler Mig 16 lock edit).
             [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.ChoCCM)] = [AppRoles.Procurement],
             [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.Procurement],
+            [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Procurement],
 
             [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.ChoCEODuyetNCC)] = [AppRoles.CostControl],
             [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.CostControl],
+            [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.CostControl],
 
             [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.DaDuyet)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
             [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
+            [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
         },
         PhaseSla: DefaultSla,
         ActivePhases:
@@ -85,20 +91,26 @@ public static class PurchaseEvaluationPolicies
             [(PurchaseEvaluationPhase.DangSoanThao, PurchaseEvaluationPhase.ChoPurchasing)] = [AppRoles.Drafter, AppRoles.DeptManager],
             [(PurchaseEvaluationPhase.DangSoanThao, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Drafter, AppRoles.DeptManager],
 
+            // Phase trung gian: 3 hành động — Duyệt forward / Trả lại / Từ chối (xem comment NccOnly).
             [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.ChoDuAn)] = [AppRoles.Procurement],
             [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.Procurement],
+            [(PurchaseEvaluationPhase.ChoPurchasing, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Procurement],
 
             [(PurchaseEvaluationPhase.ChoDuAn, PurchaseEvaluationPhase.ChoCCM)] = [AppRoles.ProjectManager],
             [(PurchaseEvaluationPhase.ChoDuAn, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.ProjectManager],
+            [(PurchaseEvaluationPhase.ChoDuAn, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.ProjectManager],
 
             [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.ChoCEODuyetPA)] = [AppRoles.CostControl],
             [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.CostControl],
+            [(PurchaseEvaluationPhase.ChoCCM, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.CostControl],
 
             [(PurchaseEvaluationPhase.ChoCEODuyetPA, PurchaseEvaluationPhase.ChoCEODuyetNCC)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
             [(PurchaseEvaluationPhase.ChoCEODuyetPA, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
+            [(PurchaseEvaluationPhase.ChoCEODuyetPA, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
 
             [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.DaDuyet)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
             [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.DangSoanThao)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
+            [(PurchaseEvaluationPhase.ChoCEODuyetNCC, PurchaseEvaluationPhase.TuChoi)] = [AppRoles.Director, AppRoles.AuthorizedSigner],
         },
         PhaseSla: DefaultSla,
         ActivePhases:
@@ -171,17 +183,21 @@ public static class PurchaseEvaluationPolicyRegistry
                 transitions[(prev.Value, s.Phase)] = roles;
                 if (userIds.Length > 0) userTransitions[(prev.Value, s.Phase)] = userIds;
 
-                // Reject path back to Drafter (common pattern)
+                // 3 hành động phase trung gian — Duyệt forward + Trả lại Drafter + Từ chối hoàn toàn
                 if (prev.Value != PurchaseEvaluationPhase.DangSoanThao && s.Phase != PurchaseEvaluationPhase.DangSoanThao)
                 {
                     transitions.TryAdd((s.Phase, PurchaseEvaluationPhase.DangSoanThao), roles);
+                    transitions.TryAdd((s.Phase, PurchaseEvaluationPhase.TuChoi), roles);
                     if (userIds.Length > 0)
+                    {
                         userTransitions.TryAdd((s.Phase, PurchaseEvaluationPhase.DangSoanThao), userIds);
+                        userTransitions.TryAdd((s.Phase, PurchaseEvaluationPhase.TuChoi), userIds);
+                    }
                 }
             }
             prev = s.Phase;
         }
-        // First step có thể reject to TuChoi
+        // First step (DangSoanThao) — Drafter có thể TuChoi (huỷ phiếu)
         if (steps.Count > 0)
             transitions.TryAdd((steps[0].Phase, PurchaseEvaluationPhase.TuChoi),
                 [AppRoles.Drafter, AppRoles.DeptManager]);
diff --git a/src/Backend/SolutionErp.Infrastructure/Services/PurchaseEvaluationWorkflowService.cs b/src/Backend/SolutionErp.Infrastructure/Services/PurchaseEvaluationWorkflowService.cs
index b0508e3..05267ca 100644
--- a/src/Backend/SolutionErp.Infrastructure/Services/PurchaseEvaluationWorkflowService.cs
+++ b/src/Backend/SolutionErp.Infrastructure/Services/PurchaseEvaluationWorkflowService.cs
@@ -43,17 +43,25 @@ public class PurchaseEvaluationWorkflowService(
 
         if (decision == ApprovalDecision.Reject)
         {
-            evaluation.RejectedFromPhase = fromPhase;
-            targetPhase = PurchaseEvaluationPhase.DangSoanThao;
+            // 2 loại Reject (Session 14):
+            //  - target=TuChoi: "Từ chối hoàn toàn" — phiếu khoá vĩnh viễn (Phase=TuChoi
+            //    → 17 handler Mig 16 lock edit). Drafter phải tạo phiếu mới. KHÔNG set
+            //    RejectedFromPhase + KHÔNG clear N-stage (không resume).
+            //  - target khác (thường = DangSoanThao): "Trả lại" — smart reject pattern
+            //    Mig 16. Set RejectedFromPhase + force DangSoanThao + clear N-stage rows
+            //    tại fromPhase → Drafter sửa rồi trình lại jump-back tới phase đã reject.
+            if (targetPhase != PurchaseEvaluationPhase.TuChoi)
+            {
+                evaluation.RejectedFromPhase = fromPhase;
+                targetPhase = PurchaseEvaluationPhase.DangSoanThao;
 
-            // N-stage state reset (Mig 18): clear inner step approval rows tại
-            // fromPhase. User resume sẽ approve lại từ inner step đầu.
-            var staleNStageRows = await db.PurchaseEvaluationDepartmentApprovals
-                .Where(a => a.PurchaseEvaluationId == evaluation.Id
-                         && a.PhaseAtApproval == (int)fromPhase
-                         && a.InnerStepId != null)
-                .ToListAsync(ct);
-            foreach (var r in staleNStageRows) db.PurchaseEvaluationDepartmentApprovals.Remove(r);
+                var staleNStageRows = await db.PurchaseEvaluationDepartmentApprovals
+                    .Where(a => a.PurchaseEvaluationId == evaluation.Id
+                             && a.PhaseAtApproval == (int)fromPhase
+                             && a.InnerStepId != null)
+                    .ToListAsync(ct);
+                foreach (var r in staleNStageRows) db.PurchaseEvaluationDepartmentApprovals.Remove(r);
+            }
         }
         else if (isResumingAfterReject)
         {
diff --git a/tests/SolutionErp.Infrastructure.Tests/Services/PeNStageApprovalTests.cs b/tests/SolutionErp.Infrastructure.Tests/Services/PeNStageApprovalTests.cs
index e946b2e..aafec55 100644
--- a/tests/SolutionErp.Infrastructure.Tests/Services/PeNStageApprovalTests.cs
+++ b/tests/SolutionErp.Infrastructure.Tests/Services/PeNStageApprovalTests.cs
@@ -278,11 +278,11 @@ public class PeNStageApprovalTests : IClassFixture<IdentityFixture>
 
         pe = await _db.PurchaseEvaluations.FirstAsync(x => x.Id == pe.Id);
 
-        // Act: admin reject (skip 2-stage gate).
+        // Act: admin "Trả lại" (target=DangSoanThao + decision=Reject Session 14).
         var admin = await _fx.CreateUserAsync($"adm-rej-{Guid.NewGuid():N}@test", "Admin", null, ["Admin"]);
         await _service.TransitionAsync(
-            pe, PurchaseEvaluationPhase.TuChoi, admin.Id, ["Admin"],
-            ApprovalDecision.Reject, "reject test");
+            pe, PurchaseEvaluationPhase.DangSoanThao, admin.Id, ["Admin"],
+            ApprovalDecision.Reject, "trả lại test");
 
         // Assert: phase = DangSoanThao, RejectedFromPhase = ChoPurchasing,
         // N-stage rows tại ChoPurchasing đã clear.
diff --git a/tests/SolutionErp.Infrastructure.Tests/Services/PeTwoStageApprovalTests.cs b/tests/SolutionErp.Infrastructure.Tests/Services/PeTwoStageApprovalTests.cs
index 2cff73c..2fa8ebc 100644
--- a/tests/SolutionErp.Infrastructure.Tests/Services/PeTwoStageApprovalTests.cs
+++ b/tests/SolutionErp.Infrastructure.Tests/Services/PeTwoStageApprovalTests.cs
@@ -197,24 +197,41 @@ public class PeTwoStageApprovalTests : IClassFixture<IdentityFixture>
     }
 
     [Fact]
-    public async Task Reject_Sets_RejectedFromPhase_And_Forces_DangSoanThao()
+    public async Task Reject_To_DangSoanThao_Sets_RejectedFromPhase_TraLai()
     {
-        // Arrange: PE phase=ChoCCM. Drafter reject.
+        // Session 14: "Trả lại" semantic — target=DangSoanThao + decision=Reject.
+        // Service set RejectedFromPhase + force về DangSoanThao + Drafter resume jump-back.
         var actor = await _fx.CreateUserAsync(
             $"ccm-{Guid.NewGuid():N}@test", "CCM TPB", _deptCcm, ["DeptManager", "CostControl"]);
         var pe = await SeedPeAsync(PurchaseEvaluationPhase.ChoCCM);
 
-        // Act: reject (target irrelevant — service forces về DangSoanThao).
         await _service.TransitionAsync(
-            pe, PurchaseEvaluationPhase.TuChoi, actor.Id, ["DeptManager", "CostControl"],
-            ApprovalDecision.Reject, "không phù hợp");
+            pe, PurchaseEvaluationPhase.DangSoanThao, actor.Id, ["DeptManager", "CostControl"],
+            ApprovalDecision.Reject, "trả lại Drafter sửa");
 
-        // Assert.
         var fresh = await _db.PurchaseEvaluations.AsNoTracking().FirstAsync(x => x.Id == pe.Id);
         fresh.Phase.Should().Be(PurchaseEvaluationPhase.DangSoanThao);
         fresh.RejectedFromPhase.Should().Be(PurchaseEvaluationPhase.ChoCCM);
     }
 
+    [Fact]
+    public async Task Reject_To_TuChoi_Locks_Permanently_No_RejectedFromPhase()
+    {
+        // Session 14: "Từ chối" semantic — target=TuChoi + decision=Reject.
+        // Service KHÔNG override target + KHÔNG set RejectedFromPhase (phiếu khoá vĩnh viễn).
+        var actor = await _fx.CreateUserAsync(
+            $"ccm-{Guid.NewGuid():N}@test", "CCM TPB cancel", _deptCcm, ["DeptManager", "CostControl"]);
+        var pe = await SeedPeAsync(PurchaseEvaluationPhase.ChoCCM);
+
+        await _service.TransitionAsync(
+            pe, PurchaseEvaluationPhase.TuChoi, actor.Id, ["DeptManager", "CostControl"],
+            ApprovalDecision.Reject, "từ chối hoàn toàn");
+
+        var fresh = await _db.PurchaseEvaluations.AsNoTracking().FirstAsync(x => x.Id == pe.Id);
+        fresh.Phase.Should().Be(PurchaseEvaluationPhase.TuChoi);
+        fresh.RejectedFromPhase.Should().BeNull();
+    }
+
     [Fact]
     public async Task Resume_After_Reject_Jumps_Back_To_RejectedPhase()
     {