fix: reduce excessive file writes from account state updates

- Remove unconditional requestSaveToDisk() on every API request (line 1702)
- Add snapshot deduplication to skip no-op writes
- Increase debounce from 1s to 5s for rate-limit storm resilience
- Move save trigger to after markAccountUsed() where lastUsed is persisted

Co-authored-by: Amp <amp@ampcode.com>
Amp-Thread-ID: https://ampcode.com/threads/T-019c6dae-36aa-7524-849b-d8c515ba0cd1

Author: mrm007

src/plugin.ts

@@ -1699,8 +1699,6 @@ export const createAntigravityPlugin = (providerId: string) => async (
               accountManager.markToastShown(account.index);
             }
 
-            accountManager.requestSaveToDisk();
-
             let authRecord = accountManager.toAuthDetails(account);
 
             if (accessTokenExpired(authRecord)) {
@@ -2330,7 +2328,8 @@ export const createAntigravityPlugin = (providerId: string) => async (
                   account.consecutiveFailures = 0;
                   getHealthTracker().recordSuccess(account.index);
                   accountManager.markAccountUsed(account.index);
-                  
+                  accountManager.requestSaveToDisk();
+
                   void triggerAsyncQuotaRefreshForAccount(
                     accountManager,
                     account.index,

src/plugin/accounts.test.ts

@@ -1,7 +1,7 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import { AccountManager, type ModelFamily, type HeaderStyle, parseRateLimitReason, calculateBackoffMs, type RateLimitReason, resolveQuotaGroup } from "./accounts";
-import type { AccountStorageV4 } from "./storage";
+import { saveAccounts, type AccountStorageV4 } from "./storage";
 import type { OAuthAuthDetails } from "./types";
 
 // Mock storage to prevent test data from leaking to real config files
@@ -1069,6 +1069,8 @@ describe("AccountManager", () => {
   describe("Issue #174: saveToDisk throttling", () => {
     it("requestSaveToDisk coalesces multiple calls into one write", async () => {
       vi.useFakeTimers();
+      const saveMock = vi.mocked(saveAccounts);
+      saveMock.mockClear();
 
       const stored: AccountStorageV4 = {
         version: 4,
@@ -1079,23 +1081,22 @@ describe("AccountManager", () => {
       };
 
       const manager = new AccountManager(undefined, stored);
-      const saveSpy = vi.spyOn(manager, "saveToDisk").mockResolvedValue();
 
       manager.requestSaveToDisk();
       manager.requestSaveToDisk();
       manager.requestSaveToDisk();
 
-      expect(saveSpy).not.toHaveBeenCalled();
+      expect(saveMock).not.toHaveBeenCalled();
 
-      await vi.advanceTimersByTimeAsync(1500);
+      await vi.advanceTimersByTimeAsync(5500);
 
-      expect(saveSpy).toHaveBeenCalledTimes(1);
-
-      saveSpy.mockRestore();
+      expect(saveMock).toHaveBeenCalledTimes(1);
     });
 
     it("flushSaveToDisk waits for pending save to complete", async () => {
       vi.useFakeTimers();
+      const saveMock = vi.mocked(saveAccounts);
+      saveMock.mockClear();
 
       const stored: AccountStorageV4 = {
         version: 4,
@@ -1106,22 +1107,21 @@ describe("AccountManager", () => {
       };
 
       const manager = new AccountManager(undefined, stored);
-      const saveSpy = vi.spyOn(manager, "saveToDisk").mockResolvedValue();
 
       manager.requestSaveToDisk();
 
       const flushPromise = manager.flushSaveToDisk();
 
-      await vi.advanceTimersByTimeAsync(1500);
+      await vi.advanceTimersByTimeAsync(5500);
       await flushPromise;
 
-      expect(saveSpy).toHaveBeenCalledTimes(1);
-
-      saveSpy.mockRestore();
+      expect(saveMock).toHaveBeenCalledTimes(1);
     });
 
     it("does not save again if no new requestSaveToDisk after flush", async () => {
       vi.useFakeTimers();
+      const saveMock = vi.mocked(saveAccounts);
+      saveMock.mockClear();
 
       const stored: AccountStorageV4 = {
         version: 4,
@@ -1132,18 +1132,41 @@ describe("AccountManager", () => {
       };
 
       const manager = new AccountManager(undefined, stored);
-      const saveSpy = vi.spyOn(manager, "saveToDisk").mockResolvedValue();
 
       manager.requestSaveToDisk();
-      await vi.advanceTimersByTimeAsync(1500);
+      await vi.advanceTimersByTimeAsync(5500);
+
+      expect(saveMock).toHaveBeenCalledTimes(1);
 
-      expect(saveSpy).toHaveBeenCalledTimes(1);
+      await vi.advanceTimersByTimeAsync(6000);
+
+      expect(saveMock).toHaveBeenCalledTimes(1);
+    });
+
+    it("skips write when account state has not changed", async () => {
+      vi.useFakeTimers();
+      const saveMock = vi.mocked(saveAccounts);
+      saveMock.mockClear();
+
+      const stored: AccountStorageV4 = {
+        version: 4,
+        accounts: [
+          { refreshToken: "r1", projectId: "p1", addedAt: 1, lastUsed: 0 },
+        ],
+        activeIndex: 0,
+      };
 
-      await vi.advanceTimersByTimeAsync(3000);
+      const manager = new AccountManager(undefined, stored);
 
-      expect(saveSpy).toHaveBeenCalledTimes(1);
+      // First save — should write
+      manager.requestSaveToDisk();
+      await vi.advanceTimersByTimeAsync(5500);
+      expect(saveMock).toHaveBeenCalledTimes(1);
 
-      saveSpy.mockRestore();
+      // Second save with no state change — should skip
+      manager.requestSaveToDisk();
+      await vi.advanceTimersByTimeAsync(5500);
+      expect(saveMock).toHaveBeenCalledTimes(1);
     });
   });
 

src/plugin/accounts.ts

@@ -312,6 +312,7 @@ export class AccountManager {
   private savePending = false;
   private saveTimeout: ReturnType<typeof setTimeout> | null = null;
   private savePromiseResolvers: Array<() => void> = [];
+  private lastSavedSnapshot: string | null = null;
 
   static async loadFromDisk(authFallback?: OAuthAuthDetails): Promise<AccountManager> {
     const stored = await loadAccounts();
@@ -973,11 +974,11 @@ export class AccountManager {
     return [...this.accounts];
   }
 
-  async saveToDisk(): Promise<void> {
+  private buildStorageState(): AccountStorageV4 {
     const claudeIndex = Math.max(0, this.currentAccountIndexByFamily.claude);
     const geminiIndex = Math.max(0, this.currentAccountIndexByFamily.gemini);
-    
-    const storage: AccountStorageV4 = {
+
+    return {
       version: 4,
       accounts: this.accounts.map((a) => ({
         email: a.email,
@@ -1005,9 +1006,11 @@ export class AccountManager {
         claude: claudeIndex,
         gemini: geminiIndex,
       },
-    };
+    }
+  }
 
-    await saveAccounts(storage);
+  async saveToDisk(): Promise<void> {
+    await saveAccounts(this.buildStorageState());
   }
 
   requestSaveToDisk(): void {
@@ -1017,7 +1020,7 @@ export class AccountManager {
     this.savePending = true;
     this.saveTimeout = setTimeout(() => {
       void this.executeSave();
-    }, 1000);
+    }, 5000);
   }
 
   async flushSaveToDisk(): Promise<void> {
@@ -1032,9 +1035,14 @@ export class AccountManager {
   private async executeSave(): Promise<void> {
     this.savePending = false;
     this.saveTimeout = null;
-    
+
     try {
-      await this.saveToDisk();
+      const state = this.buildStorageState();
+      const snapshot = JSON.stringify(state);
+      if (snapshot !== this.lastSavedSnapshot) {
+        await saveAccounts(state);
+        this.lastSavedSnapshot = snapshot;
+      }
     } catch {
       // best-effort persistence; avoid unhandled rejection from timer-driven saves
     } finally {