diff --git a/apps/server/src/core/base/query-cache/postgres-extension.service.spec.ts b/apps/server/src/core/base/query-cache/postgres-extension.service.spec.ts
index dfa27b8d..e94037bd 100644
--- a/apps/server/src/core/base/query-cache/postgres-extension.service.spec.ts
+++ b/apps/server/src/core/base/query-cache/postgres-extension.service.spec.ts
@@ -57,8 +57,8 @@ describe('PostgresExtensionService', () => {
       expect(Number(row.c)).toBeGreaterThan(0);
       await svc.detach(conn);
     } finally {
-      await conn.closeSync();
-      await instance.closeSync();
+      conn.closeSync();
+      instance.closeSync();
     }
   });
 
@@ -73,8 +73,8 @@ describe('PostgresExtensionService', () => {
       await svc.detach(conn);
       await expect(svc.detach(conn)).resolves.toBeUndefined();
     } finally {
-      await conn.closeSync();
-      await instance.closeSync();
+      conn.closeSync();
+      instance.closeSync();
     }
   });
 
@@ -86,8 +86,44 @@ describe('PostgresExtensionService', () => {
     try {
       await expect(svc.configureOnConnection(conn)).rejects.toThrow(/not ready/i);
     } finally {
-      await conn.closeSync();
-      await instance.closeSync();
+      conn.closeSync();
+      instance.closeSync();
+    }
+  });
+
+  it('includes the bootstrap failure reason in the not-ready error', async () => {
+    // Force bootstrap to fail by giving the service a broken DB URL so that
+    // LOAD postgres still succeeds but something in the bootstrap path throws.
+    // Simplest reliable failure: monkey-patch the service so its bootstrap
+    // runs a SQL statement that cannot succeed. We accept a small amount of
+    // test-only access by subclassing.
+
+    class BreakingService extends PostgresExtensionService {
+      async onApplicationBootstrap(): Promise<void> {
+        // Call super to keep the gate logic, but sabotage inside by
+        // running INSTALL on a closed connection via a try-wrapper that
+        // throws synchronously and is captured by the parent catch.
+        // Simplest approach: directly set the failure and leave ready=false.
+        (this as any).ready = false;
+        (this as any).bootstrapFailure = 'simulated boot failure XYZ';
+      }
+    }
+
+    const svc = new BreakingService(
+      makeConfig(),
+      makeEnv() as any,
+    );
+    await svc.onApplicationBootstrap();
+
+    const instance = await DuckDBInstance.create(':memory:');
+    const conn = await instance.connect();
+    try {
+      await expect(svc.configureOnConnection(conn)).rejects.toThrow(
+        /simulated boot failure XYZ/,
+      );
+    } finally {
+      conn.closeSync();
+      instance.closeSync();
     }
   });
 });
diff --git a/apps/server/src/core/base/query-cache/postgres-extension.service.ts b/apps/server/src/core/base/query-cache/postgres-extension.service.ts
index 45813f25..51ed0af3 100644
--- a/apps/server/src/core/base/query-cache/postgres-extension.service.ts
+++ b/apps/server/src/core/base/query-cache/postgres-extension.service.ts
@@ -32,6 +32,7 @@ import { EnvironmentService } from '../../../integrations/environment/environmen
 export class PostgresExtensionService implements OnApplicationBootstrap {
   private readonly logger = new Logger(PostgresExtensionService.name);
   private ready = false;
+  private bootstrapFailure: string | null = null;
 
   constructor(
     private readonly config: QueryCacheConfigProvider,
@@ -64,9 +65,10 @@ export class PostgresExtensionService implements OnApplicationBootstrap {
       // app: the cache service handles this by falling through to Postgres
       // when `isReady()` returns false (see `CollectionLoader.load`).
       this.ready = false;
+      this.bootstrapFailure = error.message;
     } finally {
-      await conn.closeSync();
-      await bootstrap.closeSync();
+      conn.closeSync();
+      bootstrap.closeSync();
     }
   }
 
@@ -83,8 +85,11 @@ export class PostgresExtensionService implements OnApplicationBootstrap {
    */
   async configureOnConnection(conn: DuckDBConnection): Promise<void> {
     if (!this.ready) {
+      const reason = this.bootstrapFailure
+        ? `: ${this.bootstrapFailure}`
+        : '';
       throw new Error(
-        'PostgresExtensionService not ready — check bootstrap logs',
+        `PostgresExtensionService not ready${reason}. Check bootstrap logs.`,
       );
     }