fix: isolate payment amount evidence

backend/MiaoJiZhang.Api.Tests/ApiIntegrationTests.cs

@@ -3,8 +3,9 @@ using System.Net;
 using System.Net.Http.Headers;
 using System.Net.Http.Json;
 using System.Reflection;
-using System.Text.Json;
-using MiaoJiZhang.Api.Services;
+using System.Text.Json;
+using MiaoJiZhang.Api.Controllers;
+using MiaoJiZhang.Api.Services;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.AspNetCore.TestHost;
@@ -859,6 +860,29 @@ public sealed class RecognitionBatchActionParserTests
         Assert.Equal(1, action.Confidence);
     }
 }
+
+public sealed class RecognitionAmountUpdateEvidenceTests
+{
+    private static readonly IReadOnlyDictionary<string, string?> EvidenceOwners =
+        new Dictionary<string, string?>
+        {
+            ["evidence-a"] = "candidate-a",
+            ["evidence-b"] = "candidate-b"
+        };
+
+    [Fact]
+    public void AmountUpdateRequiresLinkedEvidenceAndHighConfidence()
+    {
+        Assert.False(ParseController.CanApplyAmountUpdate(
+            "candidate-a", null, 0.99, EvidenceOwners));
+        Assert.False(ParseController.CanApplyAmountUpdate(
+            "candidate-a", "evidence-a", 0.89, EvidenceOwners));
+        Assert.False(ParseController.CanApplyAmountUpdate(
+            "candidate-a", "evidence-b", 0.99, EvidenceOwners));
+        Assert.True(ParseController.CanApplyAmountUpdate(
+            "candidate-a", "evidence-a", 0.9, EvidenceOwners));
+    }
+}
 
 public sealed class BudgetRecommendationValidationTests
 {

backend/MiaoJiZhang.Api/Controllers/ParseController.cs

@@ -364,6 +364,9 @@ public class ParseController(AppDbContext db, ILlmClient llm, AgentService agent
     {
         var candidateIds = manifest.Candidates.Select(item => item.CandidateId).ToHashSet();
         var evidenceById = manifest.Evidence.ToDictionary(item => item.EvidenceId);
+        var evidenceOwners = evidenceById.ToDictionary(
+            entry => entry.Key,
+            entry => entry.Value.CandidateId);
         var selected = modelActions
             .Where(action => action.CandidateId != null && candidateIds.Contains(action.CandidateId))
             .GroupBy(action => action.CandidateId!)
@@ -401,7 +404,19 @@ public class ParseController(AppDbContext db, ILlmClient llm, AgentService agent
                 transferDirection = candidate.TransferDirection;
                 reason = "转账方向不明确，已保留本地结果";
             }
-            var amount = model?.Amount is > 0 ? model.Amount.Value : candidate.Amount;
+            var proposedAmount = model?.Amount is > 0 ? model.Amount.Value : candidate.Amount;
+            var amountChanged = proposedAmount != candidate.Amount;
+            var amountUpdateAllowed = !amountChanged ||
+                model?.Action == "update" && CanApplyAmountUpdate(
+                    candidate.CandidateId,
+                    model.EvidenceId,
+                    model.Confidence,
+                    evidenceOwners);
+            var amount = amountUpdateAllowed ? proposedAmount : candidate.Amount;
+            if (amountChanged && !amountUpdateAllowed)
+            {
+                reason = "金额修改证据不足，已保留本地金额";
+            }
             var category = FindCategory(
                 categories,
                 type == "income" || transferDirection == "in"
@@ -464,6 +479,18 @@ public class ParseController(AppDbContext db, ILlmClient llm, AgentService agent
         }
         return result.Take(20).ToList();
     }
+
+    internal static bool CanApplyAmountUpdate(
+        string candidateId,
+        string? evidenceId,
+        double confidence,
+        IReadOnlyDictionary<string, string?> evidenceOwners)
+    {
+        return confidence >= 0.9 &&
+               !string.IsNullOrWhiteSpace(evidenceId) &&
+               evidenceOwners.TryGetValue(evidenceId, out var owner) &&
+               owner == candidateId;
+    }
 
     private async Task<bool> FeatureEnabled(string key)
     {

backend/MiaoJiZhang.Api/Services/OpenAiVisionClient.cs

@@ -200,6 +200,7 @@ public partial class OpenAiVisionClient : ILlmClient
             只有截图明确显示失败、取消、待支付，或明确是同一 flowSessionId 的重复结果页时才可 drop。
             只有存在没有对应候选的 evidenceId 且截图明确显示交易成功时才可 create，并必须引用该 evidenceId。
             update/create 的 type 只能是 expense、income 或 transfer，amount 必须大于 0；transfer 必须返回 transferDirection=in|out。
+            update 修改 amount 时必须引用属于该 candidateId 的 evidenceId，且 confidence 不低于 0.9；证据不足时保持候选金额。
             截图未明确显示时间时沿用候选时间，禁止猜测时间。reason 不超过 40 个汉字。
             """;
         var messages = new List<object>();