[codex] Fix MCP validation contract issues

changelog.d/unreleased/3160.fixed.md

@@ -0,0 +1,17 @@
+---
+category: fixed
+issues:
+  - 3160
+affected:
+  - src/CodeIndex/Mcp/McpServer.cs
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP project filter resolver failures now return structured invalid-argument errors (#3160)** — unresolved or inaccessible project filters now fail before tool execution with a bounded diagnostic instead of falling through to a generic sanitized tool failure.
+
+## 日本語
+
+- **MCP project filter resolver failure が structured invalid-argument error を返すようになりました (#3160)** — 解決できない、またはアクセスできない project filter は tool 実行前に bounded diagnostic 付きで失敗し、generic な sanitized tool failure に落ちないようになりました。

changelog.d/unreleased/3182.fixed.md

@@ -0,0 +1,17 @@
+---
+category: fixed
+issues:
+  - 3182
+affected:
+  - src/CodeIndex/Mcp/McpToolDefinitions.cs
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP path/list argument validation now shares CLI path-filter bounds (#3182)** — path-like arrays now use the CLI count and length limits, and `tools/list` advertises those bounds for client-side validation.
+
+## 日本語
+
+- **MCP path/list 引数検証が CLI の path-filter 上限を共有するようになりました (#3182)** — path 系配列は CLI と同じ件数・長さ上限を使い、`tools/list` でもクライアント側検証用にその上限を広告します。

changelog.d/unreleased/3184.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3184
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP `impact_analysis` now enforces the shared query length limit (#3184)** — oversized impact queries now fail with the same structured invalid-argument response used by other query tools before impact analysis runs.
+
+## 日本語
+
+- **MCP `impact_analysis` が共有 query 長上限を適用するようになりました (#3184)** — 長すぎる impact query は impact analysis 実行前に、他の query tool と同じ structured invalid-argument response で失敗します。

changelog.d/unreleased/3186.fixed.md

@@ -0,0 +1,17 @@
+---
+category: fixed
+issues:
+  - 3186
+affected:
+  - src/CodeIndex/Mcp/McpToolDefinitions.cs
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP required `path` arguments now fail before lookup when invalid (#3186)** — `outline` and `excerpt` now reject invalid indexed-file paths before database lookup, while `index` rejects non-string, overlong, or NUL-containing project paths before filesystem checks.
+
+## 日本語
+
+- **MCP の必須 `path` 引数が不正な場合 lookup 前に失敗するようになりました (#3186)** — `outline` と `excerpt` は不正な indexed-file path を database lookup 前に拒否し、`index` は non-string、長すぎる値、NUL を含む project path を filesystem check 前に拒否します。

changelog.d/unreleased/3192.fixed.md

@@ -0,0 +1,15 @@
+---
+category: fixed
+issues:
+  - 3192
+affected:
+  - tests/CodeIndex.Tests/McpToolContractTests.cs
+---
+
+## English
+
+- **MCP `search.cursor` contract is now regression-locked (#3192)** — `cursor` stays advertised, allowlisted, and string-typed across `tools/list` and server-side argument validation.
+
+## 日本語
+
+- **MCP `search.cursor` contract を regression lock しました (#3192)** — `cursor` が `tools/list` と server-side argument validation の両方で advertised / allowlisted / string-typed のまま保たれるよう確認します。

changelog.d/unreleased/3194.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3194
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP `definition` and `symbols` now reject invalid `since` values (#3194)** — invalid ISO 8601 timestamps now return the same structured invalid-argument response used by other MCP tools instead of silently dropping the freshness filter.
+
+## 日本語
+
+- **MCP `definition` / `symbols` が不正な `since` 値を拒否するようになりました (#3194)** — 不正な ISO 8601 timestamp は freshness filter を黙って無視せず、他の MCP tool と同じ structured invalid-argument response を返します。

changelog.d/unreleased/3195.fixed.md

@@ -0,0 +1,16 @@
+---
+category: fixed
+issues:
+  - 3195
+affected:
+  - src/CodeIndex/Mcp/McpToolHandlers.cs
+  - tests/CodeIndex.Tests/McpServerTests.cs
+---
+
+## English
+
+- **MCP pagination now rejects invalid lower bounds (#3195)** — non-positive `limit` values and negative `offset` values now return structured invalid-params errors instead of being silently clamped.
+
+## 日本語
+
+- **MCP pagination が不正な下限値を拒否するようになりました (#3195)** — 非正の `limit` と負の `offset` は、黙って補正されず structured invalid-params error を返すようになりました。

changelog.d/unreleased/3196.fixed.md

@@ -0,0 +1,15 @@
+---
+category: fixed
+issues:
+  - 3196
+affected:
+  - tests/CodeIndex.Tests/McpToolContractTests.cs
+---
+
+## English
+
+- **MCP `deps` argument contract is now regression-locked (#3196)** — `reverse`, `format`, and `cycles` stay advertised, allowlisted, and typed, while stale hidden arguments such as `direction` and `includeGenerated` stay absent.
+
+## 日本語
+
+- **MCP `deps` argument contract を regression lock しました (#3196)** — `reverse`、`format`、`cycles` が advertised / allowlisted / typed のまま保たれ、`direction` や `includeGenerated` のような古い hidden 引数が戻らないことを確認します。

changelog.d/unreleased/3197.fixed.md

@@ -0,0 +1,15 @@
+---
+category: fixed
+issues:
+  - 3197
+affected:
+  - tests/CodeIndex.Tests/McpToolContractTests.cs
+---
+
+## English
+
+- **MCP `map` argument contract is now regression-locked (#3197)** — `sections` and `depth` stay advertised, allowlisted, and validated with their documented JSON shapes.
+
+## 日本語
+
+- **MCP `map` argument contract を regression lock しました (#3197)** — `sections` と `depth` が advertised / allowlisted され、documented JSON shape のまま検証されることを確認します。

changelog.d/unreleased/3198.fixed.md

@@ -0,0 +1,15 @@
+---
+category: fixed
+issues:
+  - 3198
+affected:
+  - tests/CodeIndex.Tests/McpToolContractTests.cs
+---
+
+## English
+
+- **MCP `outline` and `validate` no-op argument contracts are now regression-locked (#3198)** — hidden no-op arguments stay absent and advertised arguments stay aligned with server-side allowlists.
+
+## 日本語
+
+- **MCP `outline` / `validate` の no-op 引数 contract を regression lock しました (#3198)** — hidden no-op 引数が戻らず、advertised 引数と server-side allowlist が一致し続けることを確認します。

src/CodeIndex/Mcp/McpServer.cs

@@ -2479,6 +2479,15 @@ JsonObject CreateUnknownToolResponseForMetrics()
                     DeferFrameLog(BuildRateLimitedLog(toolName, _caller, decision.RetryAfterMs));
                     response = CreateRateLimitedErrorResponse(id, toolName, _caller, decision.RetryAfterMs);
                 }
+                else if (ValidateProjectFilterArguments(args) is JsonObject projectFilterError)
+                {
+                    metricsError = "invalid_project_filter";
+                    response = CreateToolErrorResponse(id, projectFilterError["message"]!.GetValue<string>(),
+                        category: McpErrorEnvelope.CategoryInvalidArgument,
+                        suggestion: "Use a project name or project path from the current workspace, or correct the solution filter.",
+                        retrySafe: false,
+                        extraData: projectFilterError);
+                }
                 else
                 {
                     response = toolName switch

src/CodeIndex/Mcp/McpToolDefinitions.cs

@@ -643,13 +643,48 @@ private static void ApplyCommonSchemaConstraint(string toolName, string name, Js
             case "path":
             case "project":
             case "solution":
-                obj.TryAdd("minLength", 1);
-                obj.TryAdd("maxLength", 4096);
-                obj.TryAdd("pattern", @"^(?!/)(?![A-Za-z]:)(?!.*(^|/)\.\.(/|$))(?!.*\u0000).*$");
-                AppendConstraintDescription(obj, "Must be workspace-relative, non-empty, and must not contain NUL bytes or `..` path traversal segments.");
+                if (obj["type"]?.GetValue<string>() == "array")
+                {
+                    obj.TryAdd("maxItems", MaxMcpArrayFilterCount);
+                }
+                else if (name == "path" && toolName == "index")
+                {
+                    obj.TryAdd("minLength", 1);
+                    obj.TryAdd("maxLength", MaxMcpArrayFilterStringLength);
+                    obj.TryAdd("pattern", @"^(?!.*\u0000).+$");
+                    AppendConstraintDescription(obj, "May be absolute or relative, but must be non-empty and must not contain NUL bytes.");
+                }
+                else
+                {
+                    obj.TryAdd("minLength", 1);
+                    obj.TryAdd("maxLength", MaxMcpArrayFilterStringLength);
+                    obj.TryAdd("pattern", @"^(?!/)(?![A-Za-z]:)(?!.*(^|/)\.\.(/|$))(?!.*\u0000).*$");
+                    AppendConstraintDescription(obj, "Must be workspace-relative, non-empty, and must not contain NUL bytes or `..` path traversal segments.");
+                }
                 break;
             case "excludePaths":
-                obj.TryAdd("maxItems", 100);
+                if (obj["type"]?.GetValue<string>() == "array")
+                {
+                    obj.TryAdd("maxItems", MaxMcpArrayFilterCount);
+                }
+                else
+                {
+                    obj.TryAdd("minLength", 1);
+                    obj.TryAdd("maxLength", MaxMcpArrayFilterStringLength);
+                    obj.TryAdd("pattern", @"^(?!/)(?![A-Za-z]:)(?!.*(^|/)\.\.(/|$))(?!.*\u0000).*$");
+                    AppendConstraintDescription(obj, "Must be workspace-relative, non-empty, and must not contain NUL bytes or `..` path traversal segments.");
+                }
+                break;
+            case "sections":
+                if (obj["type"]?.GetValue<string>() == "array")
+                {
+                    obj.TryAdd("maxItems", MaxMcpArrayFilterCount);
+                }
+                else
+                {
+                    obj.TryAdd("minLength", 1);
+                    obj.TryAdd("maxLength", MaxMcpArrayFilterStringLength);
+                }
                 break;
             case "limit":
                 obj.TryAdd("minimum", 1);