refactor: implement HMR-safe singleton and improve database connection recovery

- Refactor PlatformServiceFactory to use globalThis-based singleton storage
  - Store singleton in globalThis/window/self for persistence across module reloads
  - Add comprehensive debug logging for singleton lifecycle tracking
  - Implement Proxy-based lazy initialization to avoid circular dependencies
  - Add HMR support to preserve singleton across hot module replacement

- Enhance CapacitorPlatformService database connection recovery
  - Improve getOrCreateConnection() with robust error handling
  - Add recovery path for 'already exists' desync scenarios
  - Wrap retrieveConnection and db.open() calls in try-catch blocks
  - Handle cases where retrieveConnection throws instead of returning null
  - Add 50ms delay after closeConnection to allow native cleanup

- Add shared SQLite connection manager (sqlite.ts)
  - Centralize SQLiteConnection instance creation
  - Prevent connection desync issues across the application

This addresses the issue where PlatformService singleton was being
recreated on navigation, causing repeated database initialization
attempts and connection desync errors.

src/services/PlatformServiceFactory.ts

@@ -4,76 +4,181 @@ import { CapacitorPlatformService } from "./platforms/CapacitorPlatformService";
 import { ElectronPlatformService } from "./platforms/ElectronPlatformService";
 
 /**
- * Factory class for creating platform-specific service implementations.
- * Implements the Singleton pattern to ensure only one instance of PlatformService exists.
+ * HMR-safe global singleton storage for PlatformService
  *
- * The factory determines which platform implementation to use based on the VITE_PLATFORM
- * environment variable. Supported platforms are:
- * - capacitor: Mobile platform using Capacitor
- * - electron: Desktop platform using Electron with Capacitor
- * - web: Default web platform (fallback)
+ * Uses multiple fallbacks to ensure persistence across module reloads:
+ * 1. globalThis (standard, works in most environments)
+ * 2. window (browser fallback)
+ * 3. self (web worker fallback)
+ */
+declare global {
+  // eslint-disable-next-line no-var
+  var __PLATFORM_SERVICE_SINGLETON__: PlatformService | undefined;
+}
+
+/**
+ * Get the global object for singleton storage
+ * Uses multiple fallbacks to ensure compatibility
+ */
+function getGlobal(): typeof globalThis {
+  if (typeof globalThis !== "undefined") return globalThis;
+  if (typeof window !== "undefined") return window as typeof globalThis;
+  if (typeof self !== "undefined") return self as typeof globalThis;
+  // Fallback for Node.js environments
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  return {} as any;
+}
+
+/**
+ * Factory function to create platform-specific service implementation
+ *
+ * Uses console.log instead of logger to avoid circular dependency
+ * (logger imports PlatformServiceFactory)
+ */
+function create(): PlatformService {
+  const which = import.meta.env?.VITE_PLATFORM ?? "web";
+
+  // Use console.log to avoid circular dependency with logger
+  // eslint-disable-next-line no-console
+  console.log(
+    `[PlatformServiceFactory] Creating singleton instance for platform: ${which}`,
+  );
+
+  if (which === "capacitor") return new CapacitorPlatformService();
+  if (which === "electron") return new ElectronPlatformService();
+  return new WebPlatformService();
+}
+
+/**
+ * Get or create the HMR-safe singleton instance of PlatformService
+ *
+ * Uses lazy initialization to avoid circular dependency issues at module load time.
+ */
+function getPlatformSvc(): PlatformService {
+  const global = getGlobal();
+
+  // Debug: Check if singleton exists (always log in dev to diagnose)
+  const exists = global.__PLATFORM_SERVICE_SINGLETON__ !== undefined;
+  const hasKey = Object.prototype.hasOwnProperty.call(
+    global,
+    "__PLATFORM_SERVICE_SINGLETON__",
+  );
+  // eslint-disable-next-line no-console
+  console.log(
+    `[PlatformServiceFactory] Singleton check: ${exists ? "EXISTS" : "MISSING"} (global type: ${typeof global}, has key: ${hasKey})`,
+  );
+
+  if (!exists) {
+    // eslint-disable-next-line no-console
+    console.log("[PlatformServiceFactory] Creating new singleton instance");
+    global.__PLATFORM_SERVICE_SINGLETON__ = create();
+    // Verify it was stored
+    if (global.__PLATFORM_SERVICE_SINGLETON__) {
+      // eslint-disable-next-line no-console
+      console.log(
+        "[PlatformServiceFactory] Singleton created and stored successfully",
+      );
+    } else {
+      // eslint-disable-next-line no-console
+      console.error(
+        "[PlatformServiceFactory] ERROR: Singleton creation failed - storage returned undefined",
+      );
+    }
+  } else {
+    // Log singleton reuse
+    // eslint-disable-next-line no-console
+    console.log("[PlatformServiceFactory] Reusing existing singleton instance");
+  }
+
+  // Type guard: ensure singleton exists (should never be undefined at this point)
+  const singleton = global.__PLATFORM_SERVICE_SINGLETON__;
+  if (!singleton) {
+    // eslint-disable-next-line no-console
+    console.error(
+      "[PlatformServiceFactory] CRITICAL: Singleton is undefined after creation/retrieval",
+    );
+    // Fallback: create a new one
+    global.__PLATFORM_SERVICE_SINGLETON__ = create();
+    return global.__PLATFORM_SERVICE_SINGLETON__;
+  }
+
+  return singleton;
+}
+
+/**
+ * HMR-safe singleton instance of PlatformService
+ *
+ * This is the ONLY way to access PlatformService throughout the application.
+ * Do not create new instances of platform services directly.
+ *
+ * Uses lazy initialization via Proxy to avoid circular dependency issues at module load time.
  *
  * @example
  * ```typescript
- * const platformService = PlatformServiceFactory.getInstance();
- * await platformService.takePicture();
+ * import { PlatformSvc } from "./services/PlatformServiceFactory";
+ * await PlatformSvc.takePicture();
  * ```
  */
-export class PlatformServiceFactory {
-  private static instance: PlatformService | null = null;
-  private static callCount = 0; // Debug counter
-  private static creationLogged = false; // Only log creation once
+export const PlatformSvc = new Proxy({} as PlatformService, {
+  get(_target, prop) {
+    const svc = getPlatformSvc();
+    const value = (svc as unknown as Record<string, unknown>)[prop as string];
+    // Bind methods to maintain 'this' context
+    if (typeof value === "function") {
+      return value.bind(svc);
+    }
+    return value;
+  },
+});
+
+// Preserve singleton across Vite HMR
+if (import.meta?.hot) {
+  if (import.meta.env?.MODE === "development") {
+    // Defer logging until singleton is actually accessed
+    setTimeout(() => {
+      const global = getGlobal();
+      if (global.__PLATFORM_SERVICE_SINGLETON__) {
+        // Use console.log to avoid circular dependency with logger
+        // eslint-disable-next-line no-console
+        console.log("[PlatformSvc] HMR active; singleton pinned to global");
+      }
+    }, 0);
+  }
+  import.meta.hot.accept(() => {
+    // Don't recreate on HMR - keep existing instance
+    const global = getGlobal();
+    if (!global.__PLATFORM_SERVICE_SINGLETON__) {
+      // Restore singleton if it was lost during HMR
+      global.__PLATFORM_SERVICE_SINGLETON__ = getPlatformSvc();
+    }
+  });
+  import.meta.hot.dispose(() => {
+    // Don't delete - keep the global instance
+    // The singleton will persist in globalThis/window/self
+  });
+}
 
 /**
-   * Gets or creates the singleton instance of PlatformService.
-   * Creates the appropriate platform-specific implementation based on environment.
-   *
-   * @returns {PlatformService} The singleton instance of PlatformService
+ * Legacy factory class for backward compatibility
+ * @deprecated Use `PlatformSvc` directly instead
+ */
+export class PlatformServiceFactory {
+  /**
+   * Gets the singleton instance of PlatformService.
+   * @deprecated Use `PlatformSvc` directly instead
    */
   public static getInstance(): PlatformService {
-    PlatformServiceFactory.callCount++;
-
-    if (PlatformServiceFactory.instance) {
-      // Normal case - return existing instance silently
-      return PlatformServiceFactory.instance;
-    }
-
-    // Only log when actually creating the instance
-    const platform = process.env.VITE_PLATFORM || "web";
-
-    if (!PlatformServiceFactory.creationLogged) {
-      // Use console for critical startup message to avoid circular dependency
-      // eslint-disable-next-line no-console
-      console.log(
-        `[PlatformServiceFactory] Creating singleton instance for platform: ${platform}`,
-      );
-      PlatformServiceFactory.creationLogged = true;
-    }
-
-    switch (platform) {
-      case "capacitor":
-        PlatformServiceFactory.instance = new CapacitorPlatformService();
-        break;
-      case "electron":
-        // Use a specialized electron service that extends CapacitorPlatformService
-        PlatformServiceFactory.instance = new ElectronPlatformService();
-        break;
-      case "web":
-      default:
-        PlatformServiceFactory.instance = new WebPlatformService();
-        break;
-    }
-
-    return PlatformServiceFactory.instance;
+    return PlatformSvc;
   }
 
   /**
    * Debug method to check singleton usage stats
    */
   public static getStats(): { callCount: number; instanceExists: boolean } {
+    const global = getGlobal();
     return {
-      callCount: PlatformServiceFactory.callCount,
-      instanceExists: PlatformServiceFactory.instance !== null,
+      callCount: 0, // Deprecated - no longer tracking
+      instanceExists: global.__PLATFORM_SERVICE_SINGLETON__ !== undefined,
     };
   }
 }

src/services/platforms/CapacitorPlatformService.ts

@@ -8,11 +8,10 @@ import {
 import { Capacitor } from "@capacitor/core";
 import { Share } from "@capacitor/share";
 import {
-  SQLiteConnection,
   SQLiteDBConnection,
-  CapacitorSQLite,
   DBSQLiteValues,
 } from "@capacitor-community/sqlite";
+import { SQLITE } from "./sqlite";
 
 import { runMigrations } from "@/db-sql/migration";
 import { QueryExecResult } from "@/interfaces/database";
@@ -41,16 +40,23 @@ export class CapacitorPlatformService
   /** Current camera direction */
   private currentDirection: CameraDirection = CameraDirection.Rear;
 
-  private sqlite: SQLiteConnection;
+  // Connection parameters - must be 100% consistent across all plugin calls
+  private static readonly DB_NAME = "timesafari.sqlite";
+  private static readonly READ_ONLY = false;
+  private static readonly VERSION = 1;
+  private static readonly ENCRYPTED = false;
+  private static readonly MODE = "no-encryption";
+  private static readonly LOG_CONN =
+    import.meta.env?.VITE_LOG_DB_CONN === "true";
+
   private db: SQLiteDBConnection | null = null;
-  private dbName = "timesafari.sqlite";
   private initialized = false;
   private initializationPromise: Promise<void> | null = null;
   private operationQueue = new OperationQueue<SQLiteDBConnection>();
 
   constructor() {
     super();
-    this.sqlite = new SQLiteConnection(CapacitorSQLite);
+    // Use shared SQLITE instance - do not create new SQLiteConnection
   }
 
   // ============================================================================
@@ -71,6 +77,26 @@ export class CapacitorPlatformService
     }
   }
 
+  /**
+   * Check if database connection is open
+   */
+  private async isDbOpen(db?: SQLiteDBConnection | null): Promise<boolean> {
+    try {
+      return !!db && (await db.isDBOpen()).result === true;
+    } catch {
+      return false;
+    }
+  }
+
+  /**
+   * Connection lifecycle logging (only when VITE_LOG_DB_CONN=true)
+   */
+  private connLog(msg: string, extra?: unknown): void {
+    if (CapacitorPlatformService.LOG_CONN) {
+      logger.info(`[CPS][conn] ${msg}`, extra ?? "");
+    }
+  }
+
   /**
    * Apply SQLite PRAGMAs - single vetted sequence
    */
@@ -158,7 +184,10 @@ export class CapacitorPlatformService
         }
       }
       try {
-        await this.sqlite.closeConnection(this.dbName, false);
+        await SQLITE.closeConnection(
+          CapacitorPlatformService.DB_NAME,
+          CapacitorPlatformService.READ_ONLY,
+        );
       } catch (closeConnError) {
         logger.debug(
           "[CapacitorPlatformService] Error closing connection during cleanup:",
@@ -189,11 +218,7 @@ export class CapacitorPlatformService
 
     this.initializationPromise = (async () => {
       const conn = await this.runPhase("connect", async () =>
-        this._getOrCreateConnection(this.dbName, {
-          version: 1,
-          encrypted: false,
-          mode: "no-encryption",
-        }),
+        this.getOrCreateConnection(),
       );
 
       await this.runPhase("pragmas", async () => this.applyPragmas(conn));
@@ -213,60 +238,227 @@ export class CapacitorPlatformService
   }
 
   /**
-   * Get or create connection with desync repair (v3.5 - Minimal)
+   * Get or create connection with deterministic reuse (v3.6)
+   *
+   * Order: reuse in-memory → check manager → retrieve → create
+   * Never calls createConnection when connection already exists in native plugin
    */
-  private async _getOrCreateConnection(
-    name: string,
-    opts: {
-      version?: number;
-      encrypted?: boolean;
-      mode?: string;
-    } = {},
-  ): Promise<SQLiteDBConnection> {
-    // Check if we already have an open connection
-    if (this.db) {
-      try {
-        const isOpen = await this.db.isDBOpen();
-        if (isOpen.result) {
-          return this.db;
-        }
-      } catch {
-        // Continue to retrieve/create
-      }
+  private async getOrCreateConnection(): Promise<SQLiteDBConnection> {
+    // 1) Reuse existing open connection
+    if (await this.isDbOpen(this.db)) {
+      this.connLog("reusing existing open connection");
+      return this.db!;
     }
 
-    try {
-      const has = await this.sqlite.isConnection(name, false);
-      if (has.result) {
-        const conn = await this.sqlite.retrieveConnection(name, false);
-        this.db = conn;
-        const isOpen = await conn.isDBOpen();
-        if (!isOpen.result) {
-          await conn.open();
-        }
-        return conn;
-      }
-    } catch {
-      // Will attempt repair below
-    }
-
-    // Repair JS/native desync
-    try {
-      await this.sqlite.closeConnection(name, false);
-    } catch {
-      // Ignore
-    }
-
-    const conn = await this.sqlite.createConnection(
-      name,
-      false,
-      opts.mode ?? "no-encryption",
-      opts.version ?? 1,
-      opts.encrypted ?? false,
+    // 2) Check manager state FIRST (before attempting create)
+    const exists = await SQLITE.isConnection(
+      CapacitorPlatformService.DB_NAME,
+      CapacitorPlatformService.READ_ONLY,
     );
-    this.db = conn;
-    await conn.open();
-    return conn;
+    this.connLog(`isConnection? ${exists.result ? "yes" : "no"}`);
+
+    if (exists.result) {
+      // 3) Retrieve and ensure open (before assigning to this.db)
+      try {
+        const db = await SQLITE.retrieveConnection(
+          CapacitorPlatformService.DB_NAME,
+          CapacitorPlatformService.READ_ONLY,
+        );
+        if (db) {
+          try {
+            // Always open retrieved handles before assigning
+            if (!(await this.isDbOpen(db))) {
+              await db.open();
+            }
+            this.db = db;
+            this.connLog("retrieved+open");
+            return db;
+          } catch (openErr: unknown) {
+            const openMsg =
+              openErr instanceof Error ? openErr.message : String(openErr);
+            this.connLog(
+              `retrieved connection but open() failed: ${openMsg} → close stale`,
+            );
+            // Fall through to close + create
+          }
+        }
+        // Stale registry entry; clean and fall through to create
+        this.connLog("retrieve returned null → close stale");
+      } catch (retrieveErr: unknown) {
+        const retrieveMsg =
+          retrieveErr instanceof Error
+            ? retrieveErr.message
+            : String(retrieveErr);
+        // Retrieve threw error - treat as stale registry entry
+        this.connLog(
+          `retrieveConnection threw error: ${retrieveMsg} → close stale`,
+        );
+      }
+      try {
+        await SQLITE.closeConnection(
+          CapacitorPlatformService.DB_NAME,
+          CapacitorPlatformService.READ_ONLY,
+        );
+      } catch {
+        // Ignore close errors
+      }
+    }
+
+    // 4) Create NEW (only if not found in manager)
+    // Self-heal: if create throws "already exists", try retrieve instead
+    try {
+      const db = await SQLITE.createConnection(
+        CapacitorPlatformService.DB_NAME,
+        CapacitorPlatformService.ENCRYPTED,
+        CapacitorPlatformService.MODE,
+        CapacitorPlatformService.VERSION,
+        CapacitorPlatformService.READ_ONLY,
+      );
+      try {
+        await db.open();
+        this.db = db;
+        this.connLog("created+open");
+        return db;
+      } catch (openErr: unknown) {
+        const openMsg =
+          openErr instanceof Error ? openErr.message : String(openErr);
+        // If open fails on a newly created connection, treat as "already exists" case
+        if (openMsg.includes("does not exist") || openMsg.includes("already exists")) {
+          this.connLog(
+            `create succeeded but open() failed: ${openMsg} → treating as 'already exists'`,
+          );
+          // Fall through to "already exists" recovery path
+          throw new Error("already exists");
+        }
+        // Re-throw other open errors
+        throw openErr;
+      }
+    } catch (e: unknown) {
+      const errorMessage = e instanceof Error ? e.message : String(e);
+      if (errorMessage.includes("already exists")) {
+        // Self-heal: connection exists but wasn't found by isConnection
+        this.connLog("create threw 'already exists' → trying retrieve");
+        try {
+          const db = await SQLITE.retrieveConnection(
+            CapacitorPlatformService.DB_NAME,
+            CapacitorPlatformService.READ_ONLY,
+          );
+          if (db) {
+            try {
+              if (!(await this.isDbOpen(db))) {
+                await db.open();
+              }
+              this.db = db;
+              this.connLog("retrieved+open (after create-throw)");
+              return db;
+            } catch (openErr: unknown) {
+              const openMsg =
+                openErr instanceof Error ? openErr.message : String(openErr);
+              this.connLog(
+                `retrieved connection but open() failed: ${openMsg} → closing stale + recreate`,
+              );
+              // Fall through to close + recreate
+            }
+          }
+        } catch (retrieveErr: unknown) {
+          const retrieveMsg =
+            retrieveErr instanceof Error
+              ? retrieveErr.message
+              : String(retrieveErr);
+          this.connLog(
+            `retrieveConnection threw error: ${retrieveMsg} → closing stale + recreate`,
+          );
+        }
+        // Retrieve failed after "already exists" - close stale and recreate
+        this.connLog(
+          "retrieve after create-throw failed → closing stale + recreate",
+        );
+        try {
+          await SQLITE.closeConnection(
+            CapacitorPlatformService.DB_NAME,
+            CapacitorPlatformService.READ_ONLY,
+          );
+          // Small delay to allow native cleanup
+          await new Promise((resolve) => setTimeout(resolve, 50));
+        } catch (closeErr) {
+          // Log but continue - connection might already be closed
+          this.connLog("closeConnection error (may be expected)", closeErr);
+        }
+        try {
+          const fresh = await SQLITE.createConnection(
+            CapacitorPlatformService.DB_NAME,
+            CapacitorPlatformService.ENCRYPTED,
+            CapacitorPlatformService.MODE,
+            CapacitorPlatformService.VERSION,
+            CapacitorPlatformService.READ_ONLY,
+          );
+          try {
+            await fresh.open();
+            this.db = fresh;
+            this.connLog("created+open (after stale close)");
+            return fresh;
+          } catch (freshOpenErr: unknown) {
+            const freshOpenMsg =
+              freshOpenErr instanceof Error
+                ? freshOpenErr.message
+                : String(freshOpenErr);
+            this.connLog(
+              `recreate succeeded but open() failed: ${freshOpenMsg} → final retrieve attempt`,
+            );
+            // Fall through to final retrieve attempt
+            throw freshOpenErr;
+          }
+        } catch (recreateErr: unknown) {
+          const recreateMsg =
+            recreateErr instanceof Error
+              ? recreateErr.message
+              : String(recreateErr);
+          // If recreate fails, try one more retrieve attempt
+          this.connLog(
+            `recreate failed: ${recreateMsg} → final retrieve attempt`,
+          );
+          try {
+            const finalDb = await SQLITE.retrieveConnection(
+              CapacitorPlatformService.DB_NAME,
+              CapacitorPlatformService.READ_ONLY,
+            );
+            if (finalDb) {
+              try {
+                if (!(await this.isDbOpen(finalDb))) {
+                  await finalDb.open();
+                }
+                this.db = finalDb;
+                this.connLog("retrieved+open (final attempt)");
+                return finalDb;
+              } catch (finalOpenErr: unknown) {
+                const finalOpenMsg =
+                  finalOpenErr instanceof Error
+                    ? finalOpenErr.message
+                    : String(finalOpenErr);
+                this.connLog(
+                  `final retrieve succeeded but open() failed: ${finalOpenMsg}`,
+                );
+                // Fall through to throw error
+              }
+            }
+          } catch (finalRetrieveErr: unknown) {
+            const finalRetrieveMsg =
+              finalRetrieveErr instanceof Error
+                ? finalRetrieveErr.message
+                : String(finalRetrieveErr);
+            this.connLog(
+              `final retrieve attempt also failed: ${finalRetrieveMsg}`,
+            );
+          }
+          // All recovery attempts failed
+          throw new Error(
+            `Failed to establish database connection after recovery attempts: ${recreateMsg}`,
+          );
+        }
+      }
+      // Re-throw if it's not an "already exists" error
+      throw e;
+    }
   }
 
   private async processQueue(): Promise<void> {
@@ -443,6 +635,40 @@ export class CapacitorPlatformService
     await this.initializeDatabase();
   }
 
+  /**
+   * Explicit teardown for database connection (v3.6)
+   *
+   * Use this ONLY on explicit teardown scenarios:
+   * - Sign-out
+   * - App shutdown
+   * - Corruption recovery
+   *
+   * DO NOT call on route changes or component unmounts.
+   *
+   * @public
+   */
+  public async teardown(): Promise<void> {
+    if (await this.isDbOpen(this.db)) {
+      try {
+        await this.db?.close();
+      } catch {
+        // Ignore close errors
+      }
+    }
+    try {
+      await SQLITE.closeConnection(
+        CapacitorPlatformService.DB_NAME,
+        CapacitorPlatformService.READ_ONLY,
+      );
+    } catch {
+      // Ignore close errors
+    }
+    this.db = null;
+    this.initialized = false;
+    this.initializationPromise = null;
+    this.connLog("teardown complete");
+  }
+
   private async waitForInitialization(): Promise<void> {
     // If we have an initialization promise, wait for it
     if (this.initializationPromise) {

src/services/platforms/sqlite.ts

@@ -0,0 +1,20 @@
+/**
+ * Shared SQLite connection manager for Capacitor platform
+ *
+ * Ensures only one SQLiteConnection instance exists across the application,
+ * preventing connection desync issues and unnecessary connection recreation.
+ */
+
+import { CapacitorSQLite, SQLiteConnection } from "@capacitor-community/sqlite";
+
+/**
+ * Native Capacitor SQLite plugin instance
+ * This is the bridge to the native SQLite implementation
+ */
+export const CAP_SQLITE = CapacitorSQLite;
+
+/**
+ * Shared SQLite connection manager
+ * Use this instance throughout the application - do not create new SQLiteConnection instances
+ */
+export const SQLITE = new SQLiteConnection(CAP_SQLITE);