fix(codex): move common-config TOML merge off smol-toml to backend toml_edit

updateTomlCommonConfigSnippet re-serialized the whole document through
smol-toml (parse -> deepMerge -> stringify): comments dropped, keys
reordered, and empty parent table headers synthesized -- the
long-standing "config.toml keeps getting reordered" symptom (audit C5,
introduced in 083e48bf).

Replace it with a backend command backed by the same
merge_toml_table_like / remove_toml_table_like used when writing live
configs, so the form preview and the live write share one merge
semantic and user formatting survives edit-time merges. The frontend
sync helper is deleted outright to keep the pattern from coming back.

Making the form operations async exposes them to interleaving, so a
result is discarded unless it is still current when it lands:

- a per-hook sequence number (last operation wins) covers rapid
  toggle/save races where an earlier merge resolves after a later
  removal and would flip the switch back;
- a config-baseline check covers the user hand-editing the TOML while
  a merge is in flight -- the stale result must not clobber their edit.
  The checkbox state self-heals via the existing inference effect.

Regression tests pin both by resolving a suspended merge after a newer
operation / an external edit, plus backend tests locking comment and
key-order preservation, scalar override, and value-matched removal.

src-tauri/src/commands/config.rs

@@ -275,6 +275,23 @@ pub async fn get_common_config_snippet(
         .map_err(|e| e.to_string())
 }
 
+/// 对前端编辑器里的 config.toml 文本做通用配置片段的合并/剥离。
+/// 放后端是为了走 toml_edit（保注释、保键序）；前端 smol-toml 的
+/// 整文档重序列化会破坏用户手写格式。
+#[tauri::command]
+pub async fn update_toml_common_config_snippet(
+    config_toml: String,
+    snippet_toml: String,
+    enabled: bool,
+) -> Result<String, String> {
+    crate::services::provider::update_toml_common_config_snippet(
+        &config_toml,
+        &snippet_toml,
+        enabled,
+    )
+    .map_err(|e| e.to_string())
+}
+
 #[tauri::command]
 pub async fn set_common_config_snippet(
     app_type: String,

src-tauri/src/lib.rs

@@ -1215,6 +1215,7 @@ pub fn run() {
             commands::set_claude_common_config_snippet,
             commands::get_common_config_snippet,
             commands::set_common_config_snippet,
+            commands::update_toml_common_config_snippet,
             commands::extract_common_config_snippet,
             commands::read_live_provider_settings,
             commands::get_settings,

src-tauri/src/services/provider/live.rs

@@ -306,6 +306,40 @@ fn remove_toml_table_like(target: &mut dyn TableLike, source: &dyn TableLike) {
     }
 }
 
+/// 前端表单勾选/取消"使用通用配置"时，对编辑器里的 config.toml 文本做
+/// 结构化合并/剥离。必须在后端用 toml_edit 做：前端 smol-toml 只能
+/// parse → merge → 整文档重序列化，注释全丢、键序重排，还会生成多余的
+/// 空父表头（如 `[model_providers]`）。
+pub fn update_toml_common_config_snippet(
+    config_toml: &str,
+    snippet_toml: &str,
+    enabled: bool,
+) -> Result<String, AppError> {
+    let trimmed = snippet_toml.trim();
+    if trimmed.is_empty() {
+        return Ok(config_toml.to_string());
+    }
+
+    let mut target_doc = if config_toml.trim().is_empty() {
+        DocumentMut::new()
+    } else {
+        config_toml
+            .parse::<DocumentMut>()
+            .map_err(|e| AppError::Message(format!("Invalid Codex config.toml: {e}")))?
+    };
+    let source_doc = trimmed
+        .parse::<DocumentMut>()
+        .map_err(|e| AppError::Message(format!("Invalid Codex common config snippet: {e}")))?;
+
+    if enabled {
+        merge_toml_table_like(target_doc.as_table_mut(), source_doc.as_table());
+    } else {
+        remove_toml_table_like(target_doc.as_table_mut(), source_doc.as_table());
+    }
+
+    Ok(target_doc.to_string())
+}
+
 fn settings_contain_common_config(app_type: &AppType, settings: &Value, snippet: &str) -> bool {
     let trimmed = snippet.trim();
     if trimmed.is_empty() {
@@ -1678,6 +1712,71 @@ mod tests {
     use super::*;
     use serde_json::json;
 
+    /// C5 回归锁：前端表单的合并/剥离必须走 toml_edit 文档模型。
+    /// smol-toml 的 parse→merge→stringify 整文档重序列化会丢注释、
+    /// 按字母序重排键、并为 dotted 表生成多余的空父表头。
+    #[test]
+    fn update_toml_common_config_snippet_preserves_comments_and_key_order() {
+        // 刻意非字母序的键序 + 注释，模拟用户手写格式
+        let config = r#"# my precious comment
+model = "gpt-5.5"
+model_provider = "aprov"
+disable_response_storage = true
+
+[model_providers.aprov]
+# provider comment
+name = "A Prov"
+base_url = "https://a.example/v1"
+"#;
+        let snippet = "[tui]\nnotifications = true\n";
+
+        let merged = update_toml_common_config_snippet(config, snippet, true).unwrap();
+        assert!(merged.contains("# my precious comment"));
+        assert!(merged.contains("# provider comment"));
+        let model_pos = merged.find("model = ").unwrap();
+        let provider_pos = merged.find("model_provider = ").unwrap();
+        let disable_pos = merged.find("disable_response_storage").unwrap();
+        assert!(
+            model_pos < provider_pos && provider_pos < disable_pos,
+            "merge must not reorder user keys, got: {merged}"
+        );
+        assert!(merged.contains("[tui]"));
+        assert!(merged.contains("notifications = true"));
+        assert!(
+            !merged.contains("[model_providers]\n"),
+            "merge must not synthesize an empty parent table header, got: {merged}"
+        );
+
+        let removed = update_toml_common_config_snippet(&merged, snippet, false).unwrap();
+        assert!(!removed.contains("[tui]"), "snippet keys must be stripped");
+        assert!(removed.contains("# my precious comment"));
+        assert!(removed.contains("disable_response_storage = true"));
+    }
+
+    /// 合并时标量=片段覆盖供应商值（与 Claude 侧 deepMerge 一致）；
+    /// 剥离按值匹配：用户改过的值不删（与 strip 路径的
+    /// toml_value_is_subset 语义一致）。
+    #[test]
+    fn update_toml_common_config_snippet_scalar_override_and_value_matched_removal() {
+        let snippet = "[tui]\nnotifications = true\n";
+
+        let merged =
+            update_toml_common_config_snippet("[tui]\nnotifications = false\n", snippet, true)
+                .unwrap();
+        assert!(
+            merged.contains("notifications = true"),
+            "snippet scalar should override provider value, got: {merged}"
+        );
+
+        let removed =
+            update_toml_common_config_snippet("[tui]\nnotifications = false\n", snippet, false)
+                .unwrap();
+        assert!(
+            removed.contains("notifications = false"),
+            "user-modified value must survive removal, got: {removed}"
+        );
+    }
+
     #[test]
     fn claude_common_config_apply_and_remove_roundtrip_for_non_overlapping_fields() {
         let settings = json!({

src-tauri/src/services/provider/mod.rs

@@ -25,6 +25,7 @@ pub use live::{
     import_default_config, import_hermes_providers_from_live, import_openclaw_providers_from_live,
     import_opencode_providers_from_live, read_live_settings,
     should_import_default_config_on_startup, sync_current_to_live,
+    update_toml_common_config_snippet,
 };
 
 // Internal re-exports (pub(crate))

src/components/providers/forms/CodexCommonConfigModal.tsx

@@ -9,7 +9,7 @@ interface CodexCommonConfigModalProps {
   isOpen: boolean;
   onClose: () => void;
   value: string;
-  onSave: (value: string) => boolean;
+  onSave: (value: string) => boolean | Promise<boolean>;
   error?: string;
   onExtract?: () => void;
   isExtracting?: boolean;
@@ -58,8 +58,8 @@ export const CodexCommonConfigModal: React.FC<CodexCommonConfigModalProps> = ({
     onClose();
   };
 
-  const handleSave = () => {
-    if (onSave(draftValue)) {
+  const handleSave = async () => {
+    if (await onSave(draftValue)) {
       onClose();
     }
   };

src/components/providers/forms/CodexConfigEditor.tsx

@@ -22,11 +22,11 @@ interface CodexConfigEditorProps {
 
   useCommonConfig: boolean;
 
-  onCommonConfigToggle: (checked: boolean) => void;
+  onCommonConfigToggle: (checked: boolean) => void | Promise<void>;
 
   commonConfigSnippet: string;
 
-  onCommonConfigSnippetChange: (value: string) => boolean;
+  onCommonConfigSnippetChange: (value: string) => boolean | Promise<boolean>;
 
   onCommonConfigErrorClear: () => void;
 

src/components/providers/forms/hooks/useCodexCommonConfig.ts

@@ -1,13 +1,31 @@
 import { useState, useEffect, useCallback, useRef } from "react";
 import { useTranslation } from "react-i18next";
 import { parse as parseToml } from "smol-toml";
-import {
-  updateTomlCommonConfigSnippet,
-  hasTomlCommonConfigSnippet,
-} from "@/utils/providerConfigUtils";
+import { hasTomlCommonConfigSnippet } from "@/utils/providerConfigUtils";
 import { configApi } from "@/lib/api";
 import { normalizeTomlText } from "@/utils/textNormalization";
 
+/**
+ * 合并/剥离通用配置片段（走后端 toml_edit，保注释、保键序）。
+ * 失败时返回原文本 + error，调用方据此决定是否回退 UI 状态。
+ */
+const applyTomlSnippet = async (
+  configToml: string,
+  snippetToml: string,
+  enabled: boolean,
+): Promise<{ updatedConfig: string; error?: string }> => {
+  try {
+    const updatedConfig = await configApi.updateTomlCommonConfigSnippet(
+      configToml,
+      snippetToml,
+      enabled,
+    );
+    return { updatedConfig };
+  } catch (e) {
+    return { updatedConfig: configToml, error: String(e) };
+  }
+};
+
 const LEGACY_STORAGE_KEY = "cc-switch:codex-common-config-snippet";
 const DEFAULT_CODEX_COMMON_CONFIG_SNIPPET = `# Common Codex config
 # Add your common TOML configuration here`;
@@ -48,6 +66,26 @@ export function useCodexCommonConfig({
   const hasInitializedNewMode = useRef(false);
   // 用于跟踪编辑模式是否已初始化显式开关/预览
   const hasInitializedEditMode = useRef(false);
+  // 后端 TOML 合并是异步的：连续操作（快速点开关、连点保存）可能乱序
+  // 返回。每个写 config 的异步操作在发起时领取递增序号，结果落地前
+  // 校验自己仍是最新一次；过期结果直接丢弃，保证最后一次操作胜出。
+  const tomlOpSeqRef = useRef(0);
+  // 镜像最新的 codexConfig：用户在编辑器手动改动走父组件 onChange，
+  // 不经过本 hook（序号不变）。异步结果落地前还要校验发起时的 config
+  // 基线未被外部改写，否则会覆盖用户在请求在飞期间的手动编辑。
+  const latestCodexConfigRef = useRef(codexConfig);
+  useEffect(() => {
+    latestCodexConfigRef.current = codexConfig;
+  }, [codexConfig]);
+
+  // 结果落地前的过期判定：hook 内有更新的操作（序号变了），或发起时的
+  // config 基线已被外部改写（用户手动编辑为准）。任一成立即丢弃结果。
+  const isTomlOpStale = useCallback(
+    (seq: number, baseConfig: string) =>
+      seq !== tomlOpSeqRef.current ||
+      baseConfig !== latestCodexConfigRef.current,
+    [],
+  );
 
   // 当预设变化时，重置初始化标记，使新预设能够重新触发初始化逻辑
   useEffect(() => {
@@ -168,25 +206,34 @@ export function useCodexCommonConfig({
 
     // 如果应该启用通用配置但配置中还没有，则自动添加
     if (hasCommon && !inferredHasCommon && parsedSnippet.hasContent) {
-      const { updatedConfig, error } = updateTomlCommonConfigSnippet(
-        codexConfig,
-        commonConfigSnippet,
-        true,
-      );
-      if (error) {
-        setCommonConfigError(error);
-        setUseCommonConfig(false);
-        return;
-      }
+      let cancelled = false;
+      const seq = ++tomlOpSeqRef.current;
+      (async () => {
+        const { updatedConfig, error } = await applyTomlSnippet(
+          codexConfig,
+          commonConfigSnippet,
+          true,
+        );
+        if (cancelled || isTomlOpStale(seq, codexConfig)) {
+          return;
+        }
+        if (error) {
+          setCommonConfigError(error);
+          setUseCommonConfig(false);
+          return;
+        }
 
-      setCommonConfigError("");
-      setUseCommonConfig(true);
-      isUpdatingFromCommonConfig.current = true;
-      onConfigChange(updatedConfig);
-      setTimeout(() => {
-        isUpdatingFromCommonConfig.current = false;
-      }, 0);
-      return;
+        setCommonConfigError("");
+        setUseCommonConfig(true);
+        isUpdatingFromCommonConfig.current = true;
+        onConfigChange(updatedConfig);
+        setTimeout(() => {
+          isUpdatingFromCommonConfig.current = false;
+        }, 0);
+      })();
+      return () => {
+        cancelled = true;
+      };
     }
 
     setCommonConfigError("");
@@ -197,6 +244,7 @@ export function useCodexCommonConfig({
     initialData,
     initialEnabled,
     isLoading,
+    isTomlOpStale,
     onConfigChange,
     parseCommonConfigSnippet,
   ]);
@@ -221,28 +269,39 @@ export function useCodexCommonConfig({
       return;
     }
 
-    const { updatedConfig, error } = updateTomlCommonConfigSnippet(
-      codexConfig,
-      commonConfigSnippet,
-      true,
-    );
-    if (error) {
-      setCommonConfigError(error);
-      setUseCommonConfig(false);
-      return;
-    }
+    let cancelled = false;
+    const seq = ++tomlOpSeqRef.current;
+    (async () => {
+      const { updatedConfig, error } = await applyTomlSnippet(
+        codexConfig,
+        commonConfigSnippet,
+        true,
+      );
+      if (cancelled || isTomlOpStale(seq, codexConfig)) {
+        return;
+      }
+      if (error) {
+        setCommonConfigError(error);
+        setUseCommonConfig(false);
+        return;
+      }
 
-    setCommonConfigError("");
-    setUseCommonConfig(true);
-    isUpdatingFromCommonConfig.current = true;
-    onConfigChange(updatedConfig);
-    setTimeout(() => {
-      isUpdatingFromCommonConfig.current = false;
-    }, 0);
+      setCommonConfigError("");
+      setUseCommonConfig(true);
+      isUpdatingFromCommonConfig.current = true;
+      onConfigChange(updatedConfig);
+      setTimeout(() => {
+        isUpdatingFromCommonConfig.current = false;
+      }, 0);
+    })();
+    return () => {
+      cancelled = true;
+    };
   }, [
     initialData,
     commonConfigSnippet,
     isLoading,
+    isTomlOpStale,
     codexConfig,
     onConfigChange,
     parseCommonConfigSnippet,
@@ -250,7 +309,10 @@ export function useCodexCommonConfig({
 
   // 处理通用配置开关
   const handleCommonConfigToggle = useCallback(
-    (checked: boolean) => {
+    async (checked: boolean) => {
+      // 在同步校验之前领号：即使本次走同步早退分支，也要让更早发出、
+      // 仍在飞的异步结果作废，避免它晚到后把开关翻回去。
+      const seq = ++tomlOpSeqRef.current;
       const parsedSnippet = parseCommonConfigSnippet(commonConfigSnippet);
       if (parsedSnippet.error) {
         setCommonConfigError(parsedSnippet.error);
@@ -267,12 +329,14 @@ export function useCodexCommonConfig({
         return;
       }
 
-      const { updatedConfig, error: snippetError } =
-        updateTomlCommonConfigSnippet(
-          codexConfig,
-          commonConfigSnippet,
-          checked,
-        );
+      const { updatedConfig, error: snippetError } = await applyTomlSnippet(
+        codexConfig,
+        commonConfigSnippet,
+        checked,
+      );
+      if (isTomlOpStale(seq, codexConfig)) {
+        return;
+      }
 
       if (snippetError) {
         setCommonConfigError(snippetError);
@@ -293,6 +357,7 @@ export function useCodexCommonConfig({
     [
       codexConfig,
       commonConfigSnippet,
+      isTomlOpStale,
       onConfigChange,
       parseCommonConfigSnippet,
       t,
@@ -301,7 +366,10 @@ export function useCodexCommonConfig({
 
   // 处理通用配置片段变化
   const handleCommonConfigSnippetChange = useCallback(
-    (value: string): boolean => {
+    async (value: string): Promise<boolean> => {
+      // 与 handleCommonConfigToggle 同一套序号：连续保存或保存与开关
+      // 交错时，只允许最后一次操作的结果落地。
+      const seq = ++tomlOpSeqRef.current;
       const previousSnippet = commonConfigSnippet;
 
       if (!value.trim()) {
@@ -312,11 +380,14 @@ export function useCodexCommonConfig({
           let updatedConfig = codexConfig;
 
           if (!previousParsed.error && previousParsed.hasContent) {
-            const removeResult = updateTomlCommonConfigSnippet(
+            const removeResult = await applyTomlSnippet(
               codexConfig,
               previousSnippet,
               false,
             );
+            if (isTomlOpStale(seq, codexConfig)) {
+              return false;
+            }
             if (removeResult.error) {
               setCommonConfigError(removeResult.error);
               return false;
@@ -352,11 +423,14 @@ export function useCodexCommonConfig({
         const previousParsed = parseCommonConfigSnippet(previousSnippet);
 
         if (!previousParsed.error && previousParsed.hasContent) {
-          const removeResult = updateTomlCommonConfigSnippet(
+          const removeResult = await applyTomlSnippet(
             codexConfig,
             previousSnippet,
             false,
           );
+          if (isTomlOpStale(seq, codexConfig)) {
+            return false;
+          }
           if (removeResult.error) {
             setCommonConfigError(removeResult.error);
             return false;
@@ -364,11 +438,11 @@ export function useCodexCommonConfig({
           nextConfig = removeResult.updatedConfig;
         }
 
-        const addResult = updateTomlCommonConfigSnippet(
-          nextConfig,
-          value,
-          true,
-        );
+        const addResult = await applyTomlSnippet(nextConfig, value, true);
+        // nextConfig 派生自发起时的 codexConfig，基线校验仍对 codexConfig 做
+        if (isTomlOpStale(seq, codexConfig)) {
+          return false;
+        }
 
         if (addResult.error) {
           setCommonConfigError(addResult.error);
@@ -400,6 +474,7 @@ export function useCodexCommonConfig({
     [
       commonConfigSnippet,
       codexConfig,
+      isTomlOpStale,
       onConfigChange,
       parseCommonConfigSnippet,
       t,

src/lib/api/config.ts

@@ -48,6 +48,29 @@ export async function setCommonConfigSnippet(
   return invoke("set_common_config_snippet", { appType, snippet });
 }
 
+/**
+ * 对编辑器里的 config.toml 文本做通用配置片段的合并/剥离
+ *
+ * 合并/剥离在后端用 toml_edit 完成（保注释、保键序）；前端 smol-toml
+ * 的整文档重序列化会破坏用户手写格式，禁止在前端做这类结构化改写。
+ *
+ * @param configToml - 编辑器当前的 config.toml 文本
+ * @param snippetToml - 通用配置片段（TOML 字符串）
+ * @param enabled - true 合并片段，false 按值匹配剥离片段
+ * @returns 更新后的 config.toml 文本
+ */
+export async function updateTomlCommonConfigSnippet(
+  configToml: string,
+  snippetToml: string,
+  enabled: boolean,
+): Promise<string> {
+  return invoke<string>("update_toml_common_config_snippet", {
+    configToml,
+    snippetToml,
+    enabled,
+  });
+}
+
 /**
  * 提取通用配置片段
  *

src/utils/providerConfigUtils.ts

@@ -3,7 +3,7 @@
 import type { TemplateValueConfig } from "../config/claudeProviderPresets";
 import { deepClone } from "@/utils/deepClone";
 import { normalizeTomlText } from "@/utils/textNormalization";
-import { parse as parseToml, stringify as stringifyToml } from "smol-toml";
+import { parse as parseToml } from "smol-toml";
 
 const isPlainObject = (value: unknown): value is Record<string, any> => {
   return Object.prototype.toString.call(value) === "[object Object]";
@@ -343,40 +343,9 @@ export const setApiKeyInConfig = (
 
 // ========== TOML Config Utilities ==========
 
-export interface UpdateTomlCommonConfigResult {
-  updatedConfig: string;
-  error?: string;
-}
-
-// Write/remove common config snippet to/from TOML config (structural merge)
-export const updateTomlCommonConfigSnippet = (
-  tomlString: string,
-  snippetString: string,
-  enabled: boolean,
-): UpdateTomlCommonConfigResult => {
-  if (!snippetString.trim()) {
-    return { updatedConfig: tomlString };
-  }
-
-  try {
-    const config = parseToml(normalizeTomlText(tomlString || ""));
-    const snippet = parseToml(normalizeTomlText(snippetString));
-
-    if (enabled) {
-      const merged = deepMerge(
-        deepClone(config) as Record<string, any>,
-        deepClone(snippet) as Record<string, any>,
-      );
-      return { updatedConfig: stringifyToml(merged) };
-    } else {
-      const result = deepClone(config) as Record<string, any>;
-      deepRemove(result, snippet as Record<string, any>);
-      return { updatedConfig: stringifyToml(result) };
-    }
-  } catch (e) {
-    return { updatedConfig: tomlString, error: String(e) };
-  }
-};
+// TOML 片段的合并/剥离必须走后端命令（configApi.updateTomlCommonConfigSnippet，
+// toml_edit 保注释保键序）。禁止在前端用 smol-toml parse→merge→stringify
+// 整文档重序列化：注释全丢、键序重排、还会生成多余的空父表头。
 
 // Check if TOML config already contains the common config snippet (structural subset check)
 export const hasTomlCommonConfigSnippet = (

tests/hooks/useCommonConfigSave.test.tsx

@@ -6,6 +6,7 @@ import { useGeminiCommonConfig } from "@/components/providers/forms/hooks/useGem
 const getCommonConfigSnippetMock = vi.fn();
 const setCommonConfigSnippetMock = vi.fn();
 const extractCommonConfigSnippetMock = vi.fn();
+const updateTomlCommonConfigSnippetMock = vi.fn();
 
 vi.mock("@/lib/api", () => ({
   configApi: {
@@ -15,6 +16,8 @@ vi.mock("@/lib/api", () => ({
       setCommonConfigSnippetMock(...args),
     extractCommonConfigSnippet: (...args: unknown[]) =>
       extractCommonConfigSnippetMock(...args),
+    updateTomlCommonConfigSnippet: (...args: unknown[]) =>
+      updateTomlCommonConfigSnippetMock(...args),
   },
 }));
 
@@ -23,6 +26,9 @@ describe("common config snippet saving", () => {
     getCommonConfigSnippetMock.mockResolvedValue("");
     setCommonConfigSnippetMock.mockResolvedValue(undefined);
     extractCommonConfigSnippetMock.mockResolvedValue("");
+    updateTomlCommonConfigSnippetMock.mockImplementation(
+      async (configToml: string) => configToml,
+    );
   });
 
   it("does not persist an invalid Codex common config snippet", async () => {
@@ -36,9 +42,9 @@ describe("common config snippet saving", () => {
 
     await waitFor(() => expect(result.current.isLoading).toBe(false));
 
-    let saved = false;
-    act(() => {
-      saved = result.current.handleCommonConfigSnippetChange(
+    let saved = true;
+    await act(async () => {
+      saved = await result.current.handleCommonConfigSnippetChange(
         "base_url = https://bad.example/v1",
       );
     });
@@ -49,6 +55,99 @@ describe("common config snippet saving", () => {
     expect(result.current.commonConfigError).toContain("invalid value");
   });
 
+  it("discards stale toggle results when a newer toggle finishes first", async () => {
+    getCommonConfigSnippetMock.mockResolvedValue(
+      "[tui]\nnotifications = true\n",
+    );
+
+    const onConfigChange = vi.fn();
+    const { result } = renderHook(() =>
+      useCodexCommonConfig({
+        codexConfig: 'model = "gpt-5"',
+        onConfigChange,
+        initialData: { settingsConfig: { config: 'model = "gpt-5"' } },
+        initialEnabled: false,
+      }),
+    );
+
+    await waitFor(() => expect(result.current.isLoading).toBe(false));
+    await waitFor(() => expect(result.current.useCommonConfig).toBe(false));
+
+    // 第一次调用（勾选 on 的 merge）挂起，第二次（取消勾选的剥离）立即返回：
+    // 模拟后端乱序完成
+    let resolveMerge: ((value: string) => void) | undefined;
+    updateTomlCommonConfigSnippetMock
+      .mockImplementationOnce(
+        () =>
+          new Promise<string>((resolve) => {
+            resolveMerge = resolve;
+          }),
+      )
+      .mockImplementationOnce(async (configToml: string) => configToml);
+
+    await act(async () => {
+      const mergePending = result.current.handleCommonConfigToggle(true);
+      const removeDone = result.current.handleCommonConfigToggle(false);
+      await removeDone;
+      // on 的合并结果此时才姗姗来迟——必须被序号守卫丢弃
+      resolveMerge?.('model = "gpt-5"\n\n[tui]\nnotifications = true\n');
+      await mergePending;
+    });
+
+    // 用户最后一次操作是 off：过期的 on 结果不得翻转开关或改写配置
+    expect(result.current.useCommonConfig).toBe(false);
+    const lastConfig = onConfigChange.mock.calls.at(-1)?.[0] as string;
+    expect(lastConfig).not.toContain("[tui]");
+  });
+
+  it("discards async merge results when the user edited the config while in flight", async () => {
+    getCommonConfigSnippetMock.mockResolvedValue(
+      "[tui]\nnotifications = true\n",
+    );
+
+    const initialData = { settingsConfig: { config: 'model = "gpt-5"' } };
+    const onConfigChange = vi.fn();
+    const { result, rerender } = renderHook(
+      ({ config }: { config: string }) =>
+        useCodexCommonConfig({
+          codexConfig: config,
+          onConfigChange,
+          initialData,
+          initialEnabled: false,
+        }),
+      { initialProps: { config: 'model = "gpt-5"' } },
+    );
+
+    await waitFor(() => expect(result.current.isLoading).toBe(false));
+    await waitFor(() => expect(result.current.useCommonConfig).toBe(false));
+
+    let resolveMerge: ((value: string) => void) | undefined;
+    updateTomlCommonConfigSnippetMock.mockImplementationOnce(
+      () =>
+        new Promise<string>((resolve) => {
+          resolveMerge = resolve;
+        }),
+    );
+
+    let togglePending: Promise<void> = Promise.resolve();
+    act(() => {
+      togglePending = result.current.handleCommonConfigToggle(true);
+    });
+
+    // merge 在飞期间，用户在编辑器里手动改了 config（不经过 hook，
+    // 序号不变，只有 codexConfig prop 变化）
+    rerender({ config: 'model = "gpt-6-user-edit"' });
+
+    await act(async () => {
+      resolveMerge?.('model = "gpt-5"\n\n[tui]\nnotifications = true\n');
+      await togglePending;
+    });
+
+    // 基于陈旧基线的合并结果必须被丢弃，不得覆盖用户的手动编辑
+    expect(onConfigChange).not.toHaveBeenCalled();
+    expect(result.current.useCommonConfig).toBe(false);
+  });
+
   it("does not persist an invalid Gemini common config snippet", async () => {
     const onEnvChange = vi.fn();
     const { result } = renderHook(() =>