Fix object store base64 encoding to keep url-safe padding

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Fixed
+* Keep base64url padding when encoding object store names and digests, matching the reference implementation (nats.go `base64.URLEncoding`). Objects written by previous versions use unpadded meta subjects and must be re-put to be visible to the fixed client and to other NATS clients.
+
 ## [0.4.1] 2026-04-21
 
 ### Added

src/JetStream/ObjectStore/Store.php

@@ -327,8 +327,13 @@ public function seal(): void
         $this->js->updateStream($info->config->seal());
     }
 
+    /**
+     * Padding must be kept: nats.go encodes object names in meta subjects and object
+     * digests with padded url-safe base64 (base64.URLEncoding) and rejects unpadded
+     * digests on read.
+     */
     private function base64encode(string $name): string
     {
-        return rtrim(strtr(base64_encode($name), '+/', '-_'), '=');
+        return strtr(base64_encode($name), '+/', '-_');
     }
 }

tests/JetStream/ObjectStore/ObjectStoreTest.php

@@ -91,6 +91,12 @@ public function testPutObject(): void
         self::assertSame(10, $info->size);
         self::assertSame(1, $info->chunks);
 
+        // Padded url-safe base64, as written by nats.go (base64.URLEncoding).
+        self::assertSame(
+            'SHA-256=' . strtr(base64_encode(hash('sha256', $body, true)), '+/', '-_'),
+            $info->digest,
+        );
+
         $object = $store->get('xfile');
         self::assertSame($body, (string) $object);