Preserve common config during proxy takeover

Update takeover backup generation to rebuild effective provider settings with common config applied before saving restore snapshots.

Keep Codex mcp_servers entries when hot-switching providers under takeover so restore does not drop live-only MCP config.

Migrate legacy providers with inferred common-config usage to explicit commonConfigEnabled=true markers during startup and default imports, and cover the new behavior with proxy and provider regression tests.

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

@@ -461,19 +461,18 @@ fn apply_common_config_to_settings(
     }
 }
 
-pub(crate) fn write_live_with_common_config(
+pub(crate) fn build_effective_settings_with_common_config(
     db: &Database,
     app_type: &AppType,
     provider: &Provider,
-) -> Result<(), AppError> {
+) -> Result<Value, AppError> {
     let snippet = db.get_config_snippet(app_type.as_str())?;
-    let mut effective_provider = provider.clone();
+    let mut effective_settings = provider.settings_config.clone();
 
     if provider_uses_common_config(app_type, provider, snippet.as_deref()) {
         if let Some(snippet_text) = snippet.as_deref() {
-            match apply_common_config_to_settings(app_type, &provider.settings_config, snippet_text)
-            {
-                Ok(settings) => effective_provider.settings_config = settings,
+            match apply_common_config_to_settings(app_type, &effective_settings, snippet_text) {
+                Ok(settings) => effective_settings = settings,
                 Err(err) => {
                     log::warn!(
                         "Failed to apply common config for {} provider '{}': {err}",
@@ -485,6 +484,18 @@ pub(crate) fn write_live_with_common_config(
         }
     }
 
+    Ok(effective_settings)
+}
+
+pub(crate) fn write_live_with_common_config(
+    db: &Database,
+    app_type: &AppType,
+    provider: &Provider,
+) -> Result<(), AppError> {
+    let mut effective_provider = provider.clone();
+    effective_provider.settings_config =
+        build_effective_settings_with_common_config(db, app_type, provider)?;
+
     write_live_snapshot(app_type, &effective_provider)
 }
 

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

@@ -28,8 +28,9 @@ pub use live::{
 // Internal re-exports (pub(crate))
 pub(crate) use live::sanitize_claude_settings_for_live;
 pub(crate) use live::{
-    normalize_provider_common_config_for_storage, strip_common_config_from_live_settings,
-    sync_current_provider_for_app_to_live, write_live_with_common_config,
+    build_effective_settings_with_common_config, normalize_provider_common_config_for_storage,
+    strip_common_config_from_live_settings, sync_current_provider_for_app_to_live,
+    write_live_with_common_config,
 };
 
 // Internal re-exports
@@ -670,6 +671,25 @@ impl ProviderService {
         Ok(())
     }
 
+    pub fn migrate_legacy_common_config_usage_if_needed(
+        state: &AppState,
+        app_type: AppType,
+    ) -> Result<(), AppError> {
+        if app_type.is_additive_mode() {
+            return Ok(());
+        }
+
+        let Some(snippet) = state.db.get_config_snippet(app_type.as_str())? else {
+            return Ok(());
+        };
+
+        if snippet.trim().is_empty() {
+            return Ok(());
+        }
+
+        Self::migrate_legacy_common_config_usage(state, app_type, &snippet)
+    }
+
     /// Extract common config snippet from current provider
     ///
     /// Extracts the current provider's configuration and removes provider-specific fields