Fix MCP cursor and guard filter bounds

changelog.d/unreleased/3073.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3073
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP search guard filters now stop at the configured limit (#3073)** - guard filter arrays now track the combined filter budget while they are read and reject the ninth filter immediately instead of materializing the remaining entries first.
+
+## 日本語
+
+- **MCP search guard filter が設定上限で即時停止するようになりました (#3073)** - guard filter 配列は読み取り中に合計filter数の予算を追跡し、残りの要素を materialize する前に9件目を即時拒否するようになりました。

changelog.d/unreleased/3112.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3112
+affected:
+  - src/CodeIndex/Mcp/McpServer.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP resources/list now rejects unsafe cursors (#3112)** - `resources/list` now validates cursor offsets against the MCP pagination cap, computes page limits with checked arithmetic, and only returns `nextCursor` values that remain within the accepted cursor range.
+
+## 日本語
+
+- **MCP resources/list が危険な cursor を拒否するようになりました (#3112)** - `resources/list` は cursor offset を MCP pagination 上限で検証し、page limit を checked 演算で計算し、受理可能な範囲内の `nextCursor` だけを返すようになりました。

changelog.d/unreleased/3193.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3193
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP search now rejects malformed cursor domains (#3193)** - search cursors now reject non-finite scores and negative chunk or offset fields before pagination continues.
+
+## 日本語
+
+- **MCP search が不正な cursor ドメインを拒否するようになりました (#3193)** - search cursor は pagination を継続する前に、非有限の score と負の chunk / offset フィールドを拒否するようになりました。

src/CodeIndex/Mcp/McpServer.cs

@@ -1881,17 +1881,31 @@ private JsonNode HandleResourcesList(JsonNode? id, JsonNode? listParams)
     {
         const int pageSize = 200;
         var offset = 0;
-        if (listParams?["cursor"] is JsonValue cursorValue
-            && cursorValue.TryGetValue<string>(out var cursor)
-            && int.TryParse(cursor, System.Globalization.NumberStyles.None, System.Globalization.CultureInfo.InvariantCulture, out var parsed)
-            && parsed > 0)
+        if (listParams?["cursor"] is JsonNode cursorNode)
         {
-            offset = parsed;
+            if (cursorNode is not JsonValue cursorValue
+                || !cursorValue.TryGetValue<string>(out var cursor)
+                || !int.TryParse(cursor, NumberStyles.None, CultureInfo.InvariantCulture, out offset)
+                || offset < 0
+                || offset > MaxMcpPaginationOffset)
+            {
+                return CreateResourcesListCursorError(id);
+            }
+        }
+
+        int listLimit;
+        try
+        {
+            listLimit = checked(offset + pageSize + 1);
+        }
+        catch (OverflowException)
+        {
+            return CreateResourcesListCursorError(id);
         }
 
         return WithDbReader(id, args: null, reader =>
         {
-            var files = reader.ListFiles(limit: offset + pageSize + 1);
+            var files = reader.ListFiles(limit: listLimit);
             var page = files.Skip(offset).Take(pageSize).ToArray();
             var resources = new JsonArray();
             foreach (var file in page)
@@ -1913,12 +1927,24 @@ private JsonNode HandleResourcesList(JsonNode? id, JsonNode? listParams)
             {
                 ["resources"] = resources,
             };
-            if (offset + pageSize < files.Count)
-                result["nextCursor"] = (offset + pageSize).ToString(System.Globalization.CultureInfo.InvariantCulture);
+            var nextOffset = offset + pageSize;
+            if (nextOffset <= MaxMcpPaginationOffset && nextOffset < files.Count)
+                result["nextCursor"] = nextOffset.ToString(CultureInfo.InvariantCulture);
             return CreateSuccessResponse(true, id, result);
         });
     }
 
+    private static JsonObject CreateResourcesListCursorError(JsonNode? id)
+        => CreateErrorResponse(hasId: true, id: id, code: -32602,
+            message: $"resources/list cursor must be a non-negative pagination offset no greater than {MaxMcpPaginationOffset}.",
+            category: McpErrorEnvelope.CategoryInvalidArgument,
+            suggestion: "Use the `nextCursor` value returned by the previous resources/list response, or omit params.cursor to start from the first page.",
+            retrySafe: false,
+            extraData: new JsonObject
+            {
+                ["max_pagination_offset"] = MaxMcpPaginationOffset,
+            });
+
     private JsonNode HandleResourcesRead(JsonNode? id, JsonNode? readParams)
     {
         var uri = TryReadStringValue(readParams?["uri"]);

src/CodeIndex/Mcp/McpToolHandlers.cs

@@ -189,9 +189,11 @@ private static bool TryParseSearchCursor(string value, out SearchCursor cursor)
         if (firstSeparator <= 0 || firstSeparator == lastSeparator - 1)
             return false;
 
-        if (!double.TryParse(value.AsSpan(0, firstSeparator), NumberStyles.Float, CultureInfo.InvariantCulture, out var score))
+        if (!double.TryParse(value.AsSpan(0, firstSeparator), NumberStyles.Float, CultureInfo.InvariantCulture, out var score)
+            || !double.IsFinite(score))
             return false;
-        if (!long.TryParse(value.AsSpan(firstSeparator + 1, lastSeparator - firstSeparator - 1), NumberStyles.None, CultureInfo.InvariantCulture, out var chunkId))
+        if (!long.TryParse(value.AsSpan(firstSeparator + 1, lastSeparator - firstSeparator - 1), NumberStyles.None, CultureInfo.InvariantCulture, out var chunkId)
+            || chunkId < 0)
             return false;
         if (!int.TryParse(value.AsSpan(lastSeparator + 1), NumberStyles.None, CultureInfo.InvariantCulture, out var offset) || offset < 0)
             return false;
@@ -418,54 +420,47 @@ private static List<string> ReadStringList(JsonNode? args, string propertyName)
             : [];
     }
 
-    private JsonNode? TryReadStringOrStringList(JsonNode? id, JsonNode? args, string propertyName, out List<string> values)
+    private JsonNode? TryReadSearchGuardFilters(JsonNode? id, JsonNode? args, out List<SearchGuardFilter> filters)
     {
-        values = [];
-        var node = args?[propertyName];
-        if (node is null)
-            return null;
+        filters = [];
+        var collected = new List<SearchGuardFilter>();
 
-        if (node is JsonValue singleValue && singleValue.TryGetValue<string>(out var singleText))
+        JsonNode? AddFilter(string propertyName, SearchGuardRole role, SearchGuardDirection direction, string value)
         {
-            values.Add(singleText);
-            return null;
-        }
+            if (collected.Count >= DbReader.MaxSearchGuardFilters)
+                return CreateToolErrorResponse(id, $"search accepts at most {DbReader.MaxSearchGuardFilters} guard filters; got {collected.Count + 1}.");
 
-        if (node is JsonArray array)
-        {
-            foreach (var item in array)
-            {
-                if (item is not JsonValue value || !value.TryGetValue<string>(out var text))
-                    return CreateToolErrorResponse(id, $"'{propertyName}' entries must be strings.");
-                values.Add(text);
-            }
+            if (string.IsNullOrWhiteSpace(value))
+                return CreateToolErrorResponse(id, $"'{propertyName}' entries must be non-empty strings.");
+            if (value.Length > QueryLimits.MaxQueryLength)
+                return CreateToolErrorResponse(id, $"'{propertyName}' query too long (max {QueryLimits.MaxQueryLength} characters).");
+
+            collected.Add(new SearchGuardFilter(role, direction, value));
             return null;
         }
 
-        return CreateToolErrorResponse(id, $"'{propertyName}' must be a string or string array.");
-    }
-
-    private JsonNode? TryReadSearchGuardFilters(JsonNode? id, JsonNode? args, out List<SearchGuardFilter> filters)
-    {
-        filters = [];
-        var collected = new List<SearchGuardFilter>();
-
         JsonNode? AddFilters(string propertyName, SearchGuardRole role, SearchGuardDirection direction)
         {
-            if (TryReadStringOrStringList(id, args, propertyName, out var values) is JsonNode readError)
-                return readError;
+            var node = args?[propertyName];
+            if (node is null)
+                return null;
 
-            foreach (var value in values)
-            {
-                if (string.IsNullOrWhiteSpace(value))
-                    return CreateToolErrorResponse(id, $"'{propertyName}' entries must be non-empty strings.");
-                if (value.Length > QueryLimits.MaxQueryLength)
-                    return CreateToolErrorResponse(id, $"'{propertyName}' query too long (max {QueryLimits.MaxQueryLength} characters).");
+            if (node is JsonValue singleValue && singleValue.TryGetValue<string>(out var singleText))
+                return AddFilter(propertyName, role, direction, singleText);
 
-                collected.Add(new SearchGuardFilter(role, direction, value));
+            if (node is JsonArray array)
+            {
+                foreach (var item in array)
+                {
+                    if (item is not JsonValue value || !value.TryGetValue<string>(out var text))
+                        return CreateToolErrorResponse(id, $"'{propertyName}' entries must be strings.");
+                    if (AddFilter(propertyName, role, direction, text) is JsonNode addError)
+                        return addError;
+                }
+                return null;
             }
 
-            return null;
+            return CreateToolErrorResponse(id, $"'{propertyName}' must be a string or string array.");
         }
 
         if (AddFilters("requireBefore", SearchGuardRole.Require, SearchGuardDirection.Before) is JsonNode requireBeforeError)
@@ -478,9 +473,7 @@ private static List<string> ReadStringList(JsonNode? args, string propertyName)
             return rejectAfterError;
 
         filters = collected;
-        return filters.Count > DbReader.MaxSearchGuardFilters
-            ? CreateToolErrorResponse(id, $"search accepts at most {DbReader.MaxSearchGuardFilters} guard filters; got {filters.Count}.")
-            : null;
+        return null;
     }
 
     private static JsonObject? ValidateCommonListArguments(JsonNode? args)

tests/CodeIndex.Tests/McpServerTests.cs

@@ -297,6 +297,37 @@ public void ToolsCall_SearchReturnsStableAtAndCursorContinuesAfterAnchor_Issue14
             second["results"]!.AsArray()[0]!["path"]!.GetValue<string>());
     }
 
+    [Theory]
+    [InlineData("NaN:1:0")]
+    [InlineData("Infinity:1:0")]
+    [InlineData("1:-1:0")]
+    [InlineData("1:1:-1")]
+    public void ToolsCall_Search_InvalidCursorDomain_ReturnsInvalidCursorError_Issue3193(string cursor)
+    {
+        var request = new JsonObject
+        {
+            ["jsonrpc"] = "2.0",
+            ["id"] = 1,
+            ["method"] = "tools/call",
+            ["params"] = new JsonObject
+            {
+                ["name"] = "search",
+                ["arguments"] = new JsonObject
+                {
+                    ["query"] = "Run",
+                    ["cursor"] = cursor,
+                },
+            },
+        };
+
+        var response = _server.HandleMessage(request)!;
+
+        var result = response["result"]!;
+        Assert.True(result["isError"]!.GetValue<bool>());
+        Assert.Contains("'cursor' must be a search pagination cursor", result["content"]![0]!["text"]!.GetValue<string>());
+        Assert.Equal("invalid_argument", result["structuredContent"]!["category"]!.GetValue<string>());
+    }
+
     [Fact]
     public void ToolsCall_Callers_TruncatedResponseIncludesNextOffsetAndPages()
     {
@@ -932,6 +963,86 @@ public void ResourcesList_ReturnsIndexedFilesAsResources()
         Assert.Equal("text/x-csharp", resource["mimeType"]!.GetValue<string>());
     }
 
+    [Theory]
+    [InlineData("-1")]
+    [InlineData("not-a-cursor")]
+    public void ResourcesList_InvalidCursor_ReturnsInvalidParams_Issue3112(string cursor)
+    {
+        var request = new JsonObject
+        {
+            ["jsonrpc"] = "2.0",
+            ["id"] = 1,
+            ["method"] = "resources/list",
+            ["params"] = new JsonObject
+            {
+                ["cursor"] = cursor,
+            },
+        };
+
+        var response = _server.HandleMessage(request)!;
+
+        Assert.Equal(-32602, response["error"]!["code"]!.GetValue<int>());
+        var data = response["error"]!["data"]!;
+        Assert.Equal("invalid_argument", data["category"]!.GetValue<string>());
+        Assert.Equal(McpServer.MaxMcpPaginationOffset, data["max_pagination_offset"]!.GetValue<int>());
+    }
+
+    [Fact]
+    public void ResourcesList_CursorBeyondPaginationCap_ReturnsInvalidParams_Issue3112()
+    {
+        var request = new JsonObject
+        {
+            ["jsonrpc"] = "2.0",
+            ["id"] = 1,
+            ["method"] = "resources/list",
+            ["params"] = new JsonObject
+            {
+                ["cursor"] = (McpServer.MaxMcpPaginationOffset + 1).ToString(System.Globalization.CultureInfo.InvariantCulture),
+            },
+        };
+
+        var response = _server.HandleMessage(request)!;
+
+        Assert.Equal(-32602, response["error"]!["code"]!.GetValue<int>());
+        var data = response["error"]!["data"]!;
+        Assert.Equal("invalid_argument", data["category"]!.GetValue<string>());
+        Assert.Equal(McpServer.MaxMcpPaginationOffset, data["max_pagination_offset"]!.GetValue<int>());
+    }
+
+    [Fact]
+    public void ResourcesList_AtPaginationCap_DoesNotEmitSelfInvalidNextCursor_Issue3112()
+    {
+        var writer = new DbWriter(_db.Connection);
+        using var transaction = writer.BeginTransaction();
+        for (var i = 0; i < McpServer.MaxMcpPaginationOffset + 200; i++)
+        {
+            writer.UpsertFile(new FileRecord
+            {
+                Path = $"zz/paged-{i:D5}.cs",
+                Lang = "csharp",
+                Size = 1,
+                Lines = 1,
+                Modified = ManualTimeProvider.FixtureUtcNow.UtcDateTime,
+                Checksum = $"bulk-{i}",
+            });
+        }
+        transaction.Commit();
+        var request = new JsonObject
+        {
+            ["jsonrpc"] = "2.0",
+            ["id"] = 1,
+            ["method"] = "resources/list",
+            ["params"] = new JsonObject
+            {
+                ["cursor"] = McpServer.MaxMcpPaginationOffset.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            },
+        };
+
+        var response = _server.HandleMessage(request)!;
+
+        Assert.Null(response["result"]!["nextCursor"]);
+    }
+
     [Fact]
     public void ResourcesList_DoesNotAdvertiseUrisTooLongToRead_Issue3122()
     {
@@ -4033,6 +4144,42 @@ public void NonAtomic(string path)
         Assert.Equal("File.Move", evidence["query"]!.GetValue<string>());
     }
 
+    [Fact]
+    public void ToolsCall_Search_GuardFiltersFailFastWhenCombinedArraysExceedLimit_Issue3073()
+    {
+        var requireBefore = new JsonArray();
+        for (var i = 0; i < DbReader.MaxSearchGuardFilters; i++)
+            requireBefore.Add($"Guard{i}");
+        var requireAfter = new JsonArray();
+        requireAfter.Add("Overflow");
+        requireAfter.Add(42);
+        var request = new JsonObject
+        {
+            ["jsonrpc"] = "2.0",
+            ["id"] = 1,
+            ["method"] = "tools/call",
+            ["params"] = new JsonObject
+            {
+                ["name"] = "search",
+                ["arguments"] = new JsonObject
+                {
+                    ["query"] = "Run",
+                    ["requireBefore"] = requireBefore,
+                    ["requireAfter"] = requireAfter,
+                },
+            },
+        };
+
+        var response = _server.HandleMessage(request)!;
+
+        var result = response["result"]!;
+        Assert.True(result["isError"]!.GetValue<bool>());
+        var text = result["content"]![0]!["text"]!.GetValue<string>();
+        Assert.Contains($"search accepts at most {DbReader.MaxSearchGuardFilters} guard filters; got {DbReader.MaxSearchGuardFilters + 1}.", text);
+        Assert.DoesNotContain("entries must be strings", text);
+        Assert.Equal("invalid_argument", result["structuredContent"]!["category"]!.GetValue<string>());
+    }
+
     [Fact]
     public void ToolsCall_Search_GuardPaginationResumesWithinSplitChunk_Issue2852()
     {