diff --git a/YKanBan.Tests/Storage/AppData/AppConfigStoreTests.cs b/YKanBan.Tests/Storage/AppData/AppConfigStoreTests.cs
index c04a37f..a22b0fc 100644
--- a/YKanBan.Tests/Storage/AppData/AppConfigStoreTests.cs
+++ b/YKanBan.Tests/Storage/AppData/AppConfigStoreTests.cs
@@ -222,6 +222,13 @@ public class AppConfigStoreTests
     [DataRow("\"column-width\": { \"custom-pixels\": \"wide\" }")]
     [DataRow("\"confirmations\": { \"delete-card\": \"nope\" }")]
     [DataRow("\"version\": \"one\"")]
+    [DataRow("\"version\": \"1\"")]
+    [DataRow("\"language\": [\"zh-Hans\"]")]
+    [DataRow("\"confirmations\": { \"delete-card\": 0 }")]
+    [DataRow("\"confirmations\": { \"delete-card\": \"false\" }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": \"500\" }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": 500.0 }")]
+    [DataRow("\"column-width\": { \"custom-pixels\": 99999999999 }")]
     public void InvalidFieldFallsBackAloneWithoutBackup(string invalidMember)
     {
         using var directory = new TempDirectory();
diff --git a/YKanBan/Storage/AppData/AppConfigStore.cs b/YKanBan/Storage/AppData/AppConfigStore.cs
index 5cf8446..29edb52 100644
--- a/YKanBan/Storage/AppData/AppConfigStore.cs
+++ b/YKanBan/Storage/AppData/AppConfigStore.cs
@@ -1,3 +1,4 @@
+using System.Globalization;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Converters;
 using Newtonsoft.Json.Linq;
@@ -8,7 +9,7 @@ namespace YKanBan.Storage.AppData;
 /// Loads and saves app.json with graceful degradation: a missing file yields
 /// defaults; a file that is not a JSON object is backed up to app.json.bak and
 /// then defaults are used; an individual invalid field (unknown enum value or
-/// language, out-of-range width, wrong type) falls back to its own default while
+/// language, out-of-range width, wrong JSON type — no implicit conversion) falls back to its own default while
 /// the other fields are kept; a file that exists but cannot be read (I/O or
 /// permission error) also yields defaults. Saving happens only when this session
 /// changed a setting (<see cref="ConfigSection.IsDirty"/>), and writes the file directly (no atomic replace) —
@@ -29,7 +30,7 @@ public sealed class AppConfigStore
     private static readonly JsonSerializer FieldTolerantSerializer = JsonSerializer.Create(new JsonSerializerSettings
     {
         NullValueHandling = NullValueHandling.Ignore,
-        Converters = { new StringEnumConverter { AllowIntegerValues = false } },
+        Converters = { new StringEnumConverter { AllowIntegerValues = false }, new StrictPrimitiveConverter() },
 
         // The JSON text is already known to be well formed here, so every error is a
         // single member that fails to convert: skip it and keep that member's default.
@@ -211,6 +212,41 @@ public sealed class AppConfigStore
         File.WriteAllText(FilePath, json);
     }
 
+    /// <summary>
+    /// Reads booleans, integers and strings only from JSON tokens of exactly that
+    /// type, so a wrong type is an invalid field (falling back to its default)
+    /// instead of being converted: <c>0</c> or <c>"false"</c> is not a boolean,
+    /// <c>"500"</c> or <c>500.0</c> is not an integer, <c>5</c> is not a string.
+    /// </summary>
+    private sealed class StrictPrimitiveConverter : JsonConverter
+    {
+        /// <inheritdoc/>
+        public override bool CanWrite => false;
+
+        /// <inheritdoc/>
+        public override bool CanConvert(Type objectType) =>
+            objectType == typeof(bool) || objectType == typeof(int) || objectType == typeof(string);
+
+        /// <inheritdoc/>
+        public override object? ReadJson(JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer)
+        {
+            JsonToken expected = objectType == typeof(bool) ? JsonToken.Boolean
+                : objectType == typeof(int) ? JsonToken.Integer
+                : JsonToken.String;
+            if (reader.TokenType != expected)
+            {
+                throw new JsonSerializationException($"Expected a {expected} token for {objectType.Name}, got {reader.TokenType}.");
+            }
+
+            // Integer tokens are read as Int64 (or BigInteger); a value outside the Int32 range is invalid too.
+            return objectType == typeof(int) ? checked((int)Convert.ToInt64(reader.Value, CultureInfo.InvariantCulture)) : reader.Value;
+        }
+
+        /// <inheritdoc/>
+        public override void WriteJson(JsonWriter writer, object? value, JsonSerializer serializer) =>
+            throw new NotSupportedException();
+    }
+
     /// <summary>
     /// Serializes a configuration in the on-disk format.
     /// </summary>
diff --git a/docs/ACCEPTANCE.md b/docs/ACCEPTANCE.md
index e9868ed..7bb0fba 100644
--- a/docs/ACCEPTANCE.md
+++ b/docs/ACCEPTANCE.md
@@ -44,7 +44,7 @@
 - [ ] 删除 `app.json`，打开设置、不改任何项直接确认后退出 → `app.json` 不被创建；改一项再改回原值后退出 → `app.json` 被写出（脏标记按"改动过"判定）
 - [ ] 处于错误页（例如参数错误页）的实例退出时不写 `app.json`（可先删除 `app.json`，退出后确认文件未被创建）
 - [ ] `app.json` 写成非法 JSON → 启动正常、使用默认值，生成 `app.json.bak`；改一次设置退出后 `app.json` 恢复为合法内容
-- [ ] `app.json` 中单个字段非法（如 `"theme": "pink"`、列宽 `"custom-pixels": 9999`）→ 仅该字段回退默认，其余设置保留，不生成 `.bak`
+- [ ] `app.json` 中单个字段非法（如 `"theme": "pink"`、列宽 `"custom-pixels": 9999`、类型不符如 `"delete-card": 0`、`"custom-pixels": "500"`）→ 仅该字段回退默认，其余设置保留，不生成 `.bak`
 
 ## B. 启动与错误页（M4 / M4R）
 
diff --git a/docs/PLAN.md b/docs/PLAN.md
index 49fb768..f37f441 100644
--- a/docs/PLAN.md
+++ b/docs/PLAN.md
@@ -16,7 +16,7 @@
 - 网络共享明确不支持；命令行参数边界；macOS 无参启动行为写入文档（§2.3、§4.1、附录）
 - 补充：导出转义规则、卡片列表虚拟化、模态窗口 FlowDirection、`Resources` 类名使用规则、CI osx-x64 运行器（§5、§7、§8）
 - 依赖：Avalonia 11.3.6 → 11.3.22，Semi.Avalonia 11.2.1.10 → 11.3.22（§7）
-- 实现回补：搜索括号嵌套上限 64 层、单个表达式至多 256 个原子，空短语、短语紧贴文本、`key:` 后空白均为非法（§6.1、§6.2）；导出表格单元格转义 `\`、默认文件名剔除非法字符（§5.8）；初始化中途锁冲突进锁冲突页、数据库文件缺失不静默新建（§4.4）；app.json 读不出 / 备份写不出 / 退出写盘失败均不阻断启动与退出（§4.3）；主题下拉选中即预览、取消恢复（§5.6）；空白新卡片确认不创建（§5.4）；app.json 脏标记按"改动过"判定（改回原值仍写盘）（§4.3）
+- 实现回补：搜索括号嵌套上限 64 层、单个表达式至多 256 个原子，空短语、短语紧贴文本、`key:` 后空白均为非法（§6.1、§6.2）；导出表格单元格转义 `\`、默认文件名剔除非法字符（§5.8）；初始化中途锁冲突进锁冲突页、数据库文件缺失不静默新建（§4.4）；app.json 读不出 / 备份写不出 / 退出写盘失败均不阻断启动与退出（§4.3）；主题下拉选中即预览、取消恢复（§5.6）；空白新卡片确认不创建（§5.4）；app.json 脏标记按"改动过"判定（改回原值仍写盘），字段类型不符不做隐式转换（§4.3）
 - 里程碑：标注 M0–M4 已完成，新增 **M4R（v1.9 回补）**（§9）
 
 ## 1. 项目概述
@@ -141,7 +141,7 @@ card_tags: (card_id, tag_id) 复合主键，双向 ON DELETE CASCADE
 - 读取：
   - 文件缺失 → 默认值启动照常运行（下次脏退出时自然创建）
   - JSON 本身无法解析 → 备份为 `app.json.bak`（覆盖旧备份）→ 以默认值启动
-  - JSON 完好但个别字段非法（未知枚举值、未知语言、列宽越界 160–720、类型不符等）→ **仅该字段回退默认值**，其余字段保留，不生成备份
+  - JSON 完好但个别字段非法（未知枚举值、未知语言、列宽越界 160–720、类型不符等；类型须严格匹配，不做隐式转换——如布尔字段写 `0` / `"false"`、整数字段写 `"500"` / `500.0` 均视为非法）→ **仅该字段回退默认值**，其余字段保留，不生成备份
   - 文件存在但无法读取（IO / 权限错误）→ 以默认值启动；`.bak` 备份写不出时跳过备份，照常以默认值启动
 - 退出写盘失败（IO / 权限错误）→ 忽略，等同丢失当次会话的设置变更；无论写盘成败都释放工作区锁与连接