feat(mapgen-studio): saved-config precedence — drift detection + orange Modified affordance with click-to-resync

apps/mapgen-studio/src/app/StudioShell.tsx

@@ -44,6 +44,7 @@ import {
   normalizeStudioSetupConfig,
   optionRowsFromParameter,
   studioSetupConfigFromLiveSnapshot,
+  studioSetupDriftsFromSavedConfig,
   updateStudioSetupSavedConfig,
   type Civ7SetupSnapshotLike,
   type Civ7StudioSetupConfig,
@@ -1398,6 +1399,19 @@ export function StudioShell(props: StudioShellProps) {
     };
   }, [liveSetup.setup, savedSetupConfigs.configurations, savedSetupConfigs.status, setupCatalog.catalog, setupConfig]);
 
+  // Config precedence (Y2): the saved-config selector must SHOW when the
+  // game-setup dropdowns (or a live sync) have superseded values the selected
+  // saved config governs — drift is "re-applying the file would change the
+  // state". The header renders the orange Modified affordance off this flag;
+  // clicking it re-applies the saved config (sync back).
+  const savedSetupConfigModified = useMemo(() => {
+    const selectedId = setupConfig.savedConfig?.id;
+    if (!selectedId) return false;
+    const savedConfig = savedSetupConfigs.configurations.find((config) => config.id === selectedId);
+    if (!savedConfig) return false;
+    return studioSetupDriftsFromSavedConfig(setupConfig, savedConfig);
+  }, [savedSetupConfigs.configurations, setupConfig]);
+
   const handleSavedSetupConfigChange = useCallback((configId: string) => {
     const savedConfig = savedSetupConfigs.configurations.find((config) => config.id === configId);
     if (!savedConfig) {
@@ -2240,6 +2254,7 @@ export function StudioShell(props: StudioShellProps) {
       onShowGridChange={setShowGrid}
       setupConfig={setupConfig}
       setupOptions={setupControlOptions}
+      savedConfigModified={savedSetupConfigModified}
       onSetupConfigChange={setSetupConfig}
       onSavedConfigChange={handleSavedSetupConfigChange}
       onHeaderHeightChange={handleHeaderHeightChange}

apps/mapgen-studio/src/features/civ7Setup/setupConfig.ts

@@ -308,6 +308,24 @@ export function updateStudioSetupSavedConfig(
   });
 }
 
+/**
+ * Drift detection for the saved-config selector (config-precedence rule): a
+ * saved config GOVERNS the setup options it specifies plus the player
+ * options it carries; the game-setup dropdowns must never silently supersede
+ * it. The studio has drifted from the selected saved config exactly when
+ * RE-APPLYING the file would change the current state — i.e. a later
+ * dropdown change (or live sync) overwrote a governed value. Keys the file
+ * does not specify are deliberately ungoverned (apply is a merge that keeps
+ * them), so editing them never counts as drift, and re-apply ("sync back")
+ * is a no-op precisely when the selector is clean.
+ */
+export function studioSetupDriftsFromSavedConfig(
+  config: Civ7StudioSetupConfig,
+  savedConfig: Civ7SavedSetupConfigFile,
+): boolean {
+  return !studioSetupConfigsEqual(config, updateStudioSetupSavedConfig(config, savedConfig));
+}
+
 export function labelForCiv7SetupValue(value: unknown): string {
   if (typeof value !== "string") return String(value ?? "");
   const stripped = value

apps/mapgen-studio/src/ui/components/AppHeader.tsx

@@ -25,6 +25,12 @@ export interface AppHeaderProps {
   };
   onSetupConfigChange: (config: Civ7StudioSetupConfig) => void;
   onSavedConfigChange: (configId: string) => void;
+  /**
+   * Config precedence: true when the game-setup dropdowns (or a live sync)
+   * superseded values the selected saved config governs. Renders the orange
+   * Modified affordance on the selector; clicking it re-applies the file.
+   */
+  savedConfigModified?: boolean;
   onHeaderHeightChange?: (height: number) => void;
   /**
    * The live-game command cluster (Pass-5 zoning v2: top = Game, bottom =
@@ -40,6 +46,7 @@ export const AppHeader: React.FC<AppHeaderProps> = ({
   onShowGridChange,
   setupConfig,
   setupOptions,
+  savedConfigModified = false,
   onSetupConfigChange,
   onSavedConfigChange,
   onHeaderHeightChange,
@@ -120,7 +127,17 @@ export const AppHeader: React.FC<AppHeaderProps> = ({
               onValueChange={(value) => onSavedConfigChange(value)}
               options={setupOptions.savedConfigOptions}
               ariaLabel="Saved config"
-              className="w-44 max-w-[34vw]" />
+              className={`w-44 max-w-[34vw] ${savedConfigModified ? 'border-warning text-warning ring-1 ring-warning/40' : ''}`} />
+            {savedConfigModified && setupConfig.savedConfig ? (
+              <button
+                type="button"
+                onClick={() => onSavedConfigChange(setupConfig.savedConfig!.id)}
+                aria-label={`Game setup modified from ${setupConfig.savedConfig.displayName} — click to re-apply the saved config`}
+                title={`Game setup modified from ${setupConfig.savedConfig.displayName} — click to re-apply the saved config`}
+                className="shrink-0 rounded border border-warning/40 px-1.5 py-0.5 text-label text-warning cursor-pointer transition-colors hover:bg-warning/10">
+                Modified
+              </button>
+            ) : null}
           </div>
 
           {gameConsole ? (

apps/mapgen-studio/test/civ7Setup/setupConfig.test.ts

@@ -3,6 +3,8 @@ import { describe, expect, it } from "vitest";
 import {
   studioSetupConfigFromSavedConfigFile,
   studioSetupConfigFromLiveSnapshot,
+  studioSetupDriftsFromSavedConfig,
+  updateStudioSetupGameOption,
   updateStudioSetupSavedConfig,
   updateStudioSetupPlayerOption,
 } from "../../src/features/civ7Setup/setupConfig";
@@ -162,4 +164,61 @@ describe("Civ7 Studio setup config", () => {
     });
     expect(updated.playerOptions[0]?.options.PlayerLeader).toBe("LEADER_ALEXANDER");
   });
+
+  // Config-precedence pins (Y2): the saved-config selector shows Modified
+  // exactly when a governed value drifted; re-apply (sync back) clears it.
+  describe("saved-config drift detection", () => {
+    const savedConfig = {
+      id: "tot-config",
+      displayName: "ToT Config",
+      fileName: "ToT Config.Civ7Cfg",
+      path: "/tmp/ToT Config.Civ7Cfg",
+      sizeBytes: 128,
+      modifiedAt: "2026-06-01T00:00:00.000Z",
+      source: "local-disk" as const,
+      summary: {},
+      setupOptions: {
+        Difficulty: "DIFFICULTY_CUSTOM",
+        GameSpeeds: "GAMESPEED_STANDARD",
+      },
+      playerOptions: [
+        {
+          playerId: 0,
+          options: {
+            PlayerLeader: "LEADER_ALEXANDER",
+            PlayerCivilization: "CIVILIZATION_GREECE",
+          },
+        },
+      ],
+    };
+    const applied = updateStudioSetupSavedConfig(
+      { gameOptions: { AgeLength: "AGE_LENGTH_STANDARD" }, playerOptions: [{ playerId: 0, options: {} }] },
+      savedConfig,
+    );
+
+    it("is clean immediately after applying the saved config", () => {
+      expect(studioSetupDriftsFromSavedConfig(applied, savedConfig)).toBe(false);
+    });
+
+    it("drifts when a game-setup dropdown supersedes a governed option", () => {
+      const drifted = updateStudioSetupGameOption(applied, "GameSpeeds", "GAMESPEED_QUICK");
+      expect(studioSetupDriftsFromSavedConfig(drifted, savedConfig)).toBe(true);
+    });
+
+    it("drifts when a player option supersedes the saved leader", () => {
+      const drifted = updateStudioSetupPlayerOption(applied, "PlayerLeader", "LEADER_ASHOKA");
+      expect(studioSetupDriftsFromSavedConfig(drifted, savedConfig)).toBe(true);
+    });
+
+    it("does NOT drift when an ungoverned option changes (the apply merge keeps it)", () => {
+      const edited = updateStudioSetupGameOption(applied, "AgeLength", "AGE_LENGTH_LONG");
+      expect(studioSetupDriftsFromSavedConfig(edited, savedConfig)).toBe(false);
+    });
+
+    it("re-applying the saved config clears the drift (sync back)", () => {
+      const drifted = updateStudioSetupGameOption(applied, "GameSpeeds", "GAMESPEED_QUICK");
+      const resynced = updateStudioSetupSavedConfig(drifted, savedConfig);
+      expect(studioSetupDriftsFromSavedConfig(resynced, savedConfig)).toBe(false);
+    });
+  });
 });