Fix MCP compact search metadata (#4402) (#4482)

Author: Widthdom

changelog.d/unreleased/4402.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 4402
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.QueryTools.cs
+  - src/CodeIndex/Mcp/McpToolHandlers.Instructions.cs
+---
+
+## English
+
+- **MCP compact search now reports actual match lines and only emits a cursor when more results exist (#4402)** — compact locations now agree with full search results, and terminal pages no longer expose a misleading `next_cursor` when `truncated` and `more_available` are false.
+
+## 日本語
+
+- **MCP compact search が実際の一致行を返し、続きがある場合だけ cursor を出力するようになりました (#4402)** — compact の位置情報が full search の結果と一致し、`truncated` と `more_available` が false の終端ページでは誤解を招く `next_cursor` を返さなくなりました。

src/CodeIndex/Mcp/McpToolHandlers.Instructions.cs

@@ -142,7 +142,12 @@ private static void AddFreshnessHint(JsonObject payload, DbReader reader)
             payload["freshness_degraded_reason"] = freshness.FreshnessDegradedReason;
     }
 
-    private static void AddSearchStabilityMetadata(JsonObject payload, DbReader reader, SearchCursor? cursor, IReadOnlyList<SearchResult> results)
+    private static void AddSearchStabilityMetadata(
+        JsonObject payload,
+        DbReader reader,
+        SearchCursor? cursor,
+        IReadOnlyList<SearchResult> results,
+        bool moreAvailable = false)
     {
         var freshness = reader.GetFreshnessHint();
         payload["result_stable_at"] = freshness.IndexedAt.HasValue
@@ -152,7 +157,7 @@ private static void AddSearchStabilityMetadata(JsonObject payload, DbReader read
         if (!freshness.FreshnessAvailable && freshness.FreshnessDegradedReason != null)
             payload["freshness_degraded_reason"] = freshness.FreshnessDegradedReason;
 
-        if (results.Count > 0)
+        if (moreAvailable && results.Count > 0)
             payload["next_cursor"] = FormatSearchCursor(results[^1]);
     }
 

src/CodeIndex/Mcp/McpToolHandlers.QueryTools.cs

@@ -188,10 +188,14 @@ private JsonNode ExecuteSearch(JsonNode? id, JsonNode? args)
                 ["excludeTests"] = excludeTests,
                 ["results"] = ToJsonArray(compactResults)
             };
-            AddSearchStabilityMetadata(structured, reader, cursor, results);
+            AddSearchStabilityMetadata(structured, reader, cursor, results, truncated);
             AddResultEnvelope(structured, results.Count, truncated ? null : results.Count, truncated);
             if (format == "compact")
-                ApplyCompactResults(structured, results, result => result.Path, result => result.StartLine);
+                ApplyCompactResults(
+                    structured,
+                    compactResults,
+                    result => result.Path,
+                    result => result.MatchLines.Count > 0 ? result.MatchLines[0] : result.ChunkStartLine);
             var topResult = results[0];
             AddNextStepSuggestion(
                 structured,

tests/CodeIndex.Tests/McpServerToolsCallTests.cs

@@ -22,19 +22,28 @@ namespace CodeIndex.Tests;
 public partial class McpServerTests
 {
     [Fact]
-    public void ToolsCall_SearchFormatCompactEmitsFileLineOnly_Issue1642()
+    public void ToolsCall_SearchFormatCompactEmitsMatchLineAndNoTerminalCursor_Issues1642And4402()
     {
+        InsertIndexedFile(
+            "src/compact-line.cs",
+            "csharp",
+            "class CompactLine\n{\n    void Needle4402() { }\n}\n");
         var request = JsonNode.Parse(
-            """{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"search","arguments":{"query":"Run","format":"compact"}}}""")!;
+            """{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"search","arguments":{"query":"Needle4402","format":"compact","limit":1}}}""")!;
 
         var response = _server.HandleMessage(request)!;
         var structured = response["result"]!["structuredContent"]!;
         var row = Assert.Single(structured["results"]!.AsArray());
 
         Assert.Equal("compact", structured["format"]!.GetValue<string>());
-        Assert.Equal("src/app.cs", row!["file"]!.GetValue<string>());
-        Assert.Equal(1, row["line"]!.GetValue<int>());
+        Assert.Equal("src/compact-line.cs", row!["file"]!.GetValue<string>());
+        Assert.Equal(3, row["line"]!.GetValue<int>());
         Assert.Null(row["snippet"]);
+        Assert.Equal(1, structured["count"]!.GetValue<int>());
+        Assert.Equal(1, structured["total"]!.GetValue<int>());
+        Assert.False(structured["truncated"]!.GetValue<bool>());
+        Assert.False(structured["more_available"]!.GetValue<bool>());
+        Assert.Null(structured["next_cursor"]);
     }
 
     [Fact]