diff --git a/app/Actions/Database/StartRedis.php b/app/Actions/Database/StartRedis.php
index c5d2d66f8e..7fc89b25ce 100644
--- a/app/Actions/Database/StartRedis.php
+++ b/app/Actions/Database/StartRedis.php
@@ -4,7 +4,6 @@ namespace App\Actions\Database;
 
 use App\Exceptions\DatabaseStartException;
 use App\Helpers\SslHelper;
-use App\Models\EnvironmentVariable;
 use App\Models\SslCertificate;
 use App\Models\StandaloneRedis;
 use App\Traits\ExecutesDatabaseStartCommands;
@@ -24,7 +23,9 @@ class StartRedis
 
     private ?SslCertificate $ssl_certificate = null;
 
-    private ?string $resolvedRedisPassword = null;
+    private string $resolvedRedisPassword = '';
+
+    private bool $redisPasswordFromSecretManager = false;
 
     private ?string $resolvedRedisUsername = null;
 
@@ -245,21 +246,26 @@ class StartRedis
     private function generate_environment_variables()
     {
         $environment_variables = collect();
+        // The stored REDIS_PASSWORD value, unresolved: the v4.3.23 server password of legacy databases.
+        $this->resolvedRedisPassword = (string) $this->database->redis_password;
+        $passwordVariable = $this->database->serverPasswordEnvironmentVariable();
 
         foreach ($this->database->runtime_environment_variables as $env) {
             $usesSecretManager = $this->database->environmentVariableUsesSecretManager($env);
 
+            if ($passwordVariable?->is($env)) {
+                $rawValue = (string) $this->database->resolveSecretManagerEnvironmentVariableValue($env);
+
+                if ($rawValue !== '') {
+                    // Credentials below are placed directly in the compose file (command).
+                    $this->resolvedRedisPassword = $this->database->formatComposeFileValue($env, $rawValue);
+                    $this->redisPasswordFromSecretManager = $usesSecretManager;
+                }
+            }
+
             if ($env->is_shared) {
                 $environment_variables->push($env->key.'='.$this->database->resolveSecretManagerEnvironmentVariable($env));
 
-                if ($env->key === 'REDIS_PASSWORD') {
-                    $this->resolvedRedisPassword = $this->redisPasswordForComposeFile($env);
-
-                    if (! $usesSecretManager) {
-                        $this->database->update(['redis_password' => $this->resolvedRedisPassword]);
-                    }
-                }
-
                 if ($env->key === 'REDIS_USERNAME') {
                     $this->resolvedRedisUsername = $this->database->resolveSecretManagerEnvironmentVariableValue($env);
 
@@ -268,15 +274,11 @@ class StartRedis
                     }
                 }
             } else {
-                if ($env->key === 'REDIS_PASSWORD' && ! $usesSecretManager) {
-                    $env->update(['value' => $this->database->redis_password]);
-                } elseif ($env->key === 'REDIS_USERNAME' && ! $usesSecretManager) {
+                if ($env->key === 'REDIS_USERNAME' && ! $usesSecretManager) {
                     $env->update(['value' => $this->database->redis_username]);
                 }
 
-                if ($env->key === 'REDIS_PASSWORD') {
-                    $this->resolvedRedisPassword = $this->redisPasswordForComposeFile($env);
-                } elseif ($env->key === 'REDIS_USERNAME') {
+                if ($env->key === 'REDIS_USERNAME') {
                     $this->resolvedRedisUsername = $this->database->resolveSecretManagerEnvironmentVariableValue($env);
                 }
 
@@ -289,20 +291,9 @@ class StartRedis
         return $environment_variables->all();
     }
 
-    /**
-     * The password is placed directly in the compose command, so a remote secret value is escaped
-     * the same way as its environment entry. Other values stay unchanged.
-     */
-    private function redisPasswordForComposeFile(EnvironmentVariable $env): ?string
-    {
-        $value = $this->database->resolveSecretManagerEnvironmentVariableValue($env);
-
-        return $value === null ? null : $this->database->formatComposeFileValue($env, $value);
-    }
-
     private function buildStartCommand(): string
     {
-        $redisPassword = $this->resolvedRedisPassword ?? $this->database->redis_password;
+        $redisPassword = $this->requirePassArgument();
         $hasRedisConf = ! is_null($this->database->redis_conf) && ! empty($this->database->redis_conf);
         $redisConfPath = '/usr/local/etc/redis/redis.conf';
 
@@ -336,6 +327,21 @@ class StartRedis
         return $command;
     }
 
+    /**
+     * The password argument of the start command. Docker Compose splits the command like a shell, so the
+     * password is quoted. Databases created before this release keep their unquoted v4.3.23 argument when
+     * quoting would change it (quotes, backslashes, whitespace, ; & | < >): Compose splits or cuts the old
+     * command there, so quoting now would change the password or options and can lose data.
+     */
+    private function requirePassArgument(): string
+    {
+        $keepsUnquotedPassword = $this->database->legacy_password_quoting
+            && ! $this->redisPasswordFromSecretManager
+            && strpbrk($this->resolvedRedisPassword, "\\'\";&|<> \t\r\n") !== false;
+
+        return $keepsUnquotedPassword ? $this->resolvedRedisPassword : escapeshellarg($this->resolvedRedisPassword);
+    }
+
     private function add_custom_redis()
     {
         if (is_null($this->database->redis_conf) || empty($this->database->redis_conf)) {
diff --git a/app/Models/StandaloneRedis.php b/app/Models/StandaloneRedis.php
index 3bfcc5434e..2e6f158cf1 100644
--- a/app/Models/StandaloneRedis.php
+++ b/app/Models/StandaloneRedis.php
@@ -66,6 +66,8 @@ class StandaloneRedis extends BaseModel
         'redis_password',
         'internal_db_url',
         'external_db_url',
+        // Internal start-command state, not part of the API.
+        'legacy_password_quoting',
     ];
 
     protected $casts = [
@@ -74,6 +76,7 @@ class StandaloneRedis extends BaseModel
         'health_check_timeout' => 'integer',
         'health_check_retries' => 'integer',
         'health_check_start_period' => 'integer',
+        'legacy_password_quoting' => 'boolean',
         'public_port_timeout' => 'integer',
         'restart_count' => 'integer',
         'last_restart_at' => 'datetime',
@@ -313,7 +316,7 @@ class StandaloneRedis extends BaseModel
             get: function () {
                 $redis_version = $this->getRedisVersion();
                 $username_part = version_compare($redis_version, '6.0', '>=') ? rawurlencode($this->redis_username).':' : '';
-                $encodedPass = rawurlencode($this->redis_password);
+                $encodedPass = rawurlencode($this->connectionPassword());
                 $scheme = $this->enable_ssl ? 'rediss' : 'redis';
                 $port = $this->enable_ssl ? 6380 : 6379;
                 $url = "{$scheme}://{$username_part}{$encodedPass}@{$this->uuid}:{$port}/0";
@@ -338,7 +341,7 @@ class StandaloneRedis extends BaseModel
                     }
                     $redis_version = $this->getRedisVersion();
                     $username_part = version_compare($redis_version, '6.0', '>=') ? rawurlencode($this->redis_username).':' : '';
-                    $encodedPass = rawurlencode($this->redis_password);
+                    $encodedPass = rawurlencode($this->connectionPassword());
                     $scheme = $this->enable_ssl ? 'rediss' : 'redis';
                     $url = "{$scheme}://{$username_part}{$encodedPass}@{$serverIp}:{$this->public_port}/0";
 
@@ -381,6 +384,47 @@ class StandaloneRedis extends BaseModel
         return $this->morphMany(EnvironmentVariable::class, 'resourceable');
     }
 
+    /**
+     * The REDIS_PASSWORD variable whose resolved value sets the server password. Databases created
+     * before this release (legacy_password_quoting) keep their v4.3.23 server password, the stored
+     * value as it is, unless the variable reads a remote secret.
+     */
+    public function serverPasswordEnvironmentVariable(): ?EnvironmentVariable
+    {
+        $environmentVariable = $this->runtime_environment_variables()->where('key', 'REDIS_PASSWORD')->first();
+
+        if (! $environmentVariable) {
+            return null;
+        }
+
+        if ($this->legacy_password_quoting && ! $this->environmentVariableUsesSecretManager($environmentVariable)) {
+            return null;
+        }
+
+        return $environmentVariable;
+    }
+
+    /**
+     * The server password for connection URLs. A remote secret is not fetched here, so the URL
+     * shows its reference instead of a stale or wrong password.
+     */
+    public function connectionPassword(): string
+    {
+        $environmentVariable = $this->serverPasswordEnvironmentVariable();
+
+        if ($environmentVariable) {
+            $password = $this->environmentVariableUsesSecretManager($environmentVariable)
+                ? (string) $environmentVariable->value
+                : (string) $this->resolveSecretManagerEnvironmentVariableValue($environmentVariable);
+
+            if ($password !== '') {
+                return $password;
+            }
+        }
+
+        return (string) $this->redis_password;
+    }
+
     public function persistentStorages()
     {
         return $this->morphMany(LocalPersistentVolume::class, 'resource');
diff --git a/database/migrations/2026_10_05_204113_add_legacy_password_quoting_to_standalone_redis.php b/database/migrations/2026_10_05_204113_add_legacy_password_quoting_to_standalone_redis.php
new file mode 100644
index 0000000000..7ecb900946
--- /dev/null
+++ b/database/migrations/2026_10_05_204113_add_legacy_password_quoting_to_standalone_redis.php
@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Until v4.3.23, the Redis start command and connection URLs used the stored REDIS_PASSWORD value
+     * as it is (a shared variable reference stayed text) and the command did not quote it. Existing
+     * databases keep that server password; databases created later resolve and quote it.
+     */
+    public function up(): void
+    {
+        Schema::table('standalone_redis', function (Blueprint $table) {
+            $table->boolean('legacy_password_quoting')->default(false);
+        });
+
+        DB::table('standalone_redis')->update(['legacy_password_quoting' => true]);
+    }
+
+    public function down(): void
+    {
+        Schema::table('standalone_redis', function (Blueprint $table) {
+            $table->dropColumn('legacy_password_quoting');
+        });
+    }
+};
diff --git a/tests/Feature/Api/LegacyPasswordQuotingApiTest.php b/tests/Feature/Api/LegacyPasswordQuotingApiTest.php
index 549f955497..78d3dd548b 100644
--- a/tests/Feature/Api/LegacyPasswordQuotingApiTest.php
+++ b/tests/Feature/Api/LegacyPasswordQuotingApiTest.php
@@ -38,4 +38,4 @@ it('does not return the internal legacy password quoting flag in the database AP
 
     expect($single->json())->not->toHaveKey('legacy_password_quoting')
         ->and(collect($list->json())->firstWhere('uuid', $database->uuid))->not->toHaveKey('legacy_password_quoting');
-})->with(['keydb' => 'create_standalone_keydb', 'dragonfly' => 'create_standalone_dragonfly']);
+})->with(['keydb' => 'create_standalone_keydb', 'dragonfly' => 'create_standalone_dragonfly', 'redis' => 'create_standalone_redis']);
diff --git a/tests/Feature/RedisLegacyPasswordQuotingTest.php b/tests/Feature/RedisLegacyPasswordQuotingTest.php
new file mode 100644
index 0000000000..dec7077109
--- /dev/null
+++ b/tests/Feature/RedisLegacyPasswordQuotingTest.php
@@ -0,0 +1,187 @@
+<?php
+
+use App\Actions\Database\StartRedis;
+use App\Models\Environment;
+use App\Models\InstanceSettings;
+use App\Models\IntegrationToken;
+use App\Models\PrivateKey;
+use App\Models\Project;
+use App\Models\Server;
+use App\Models\SharedEnvironmentVariable;
+use App\Models\StandaloneDocker;
+use App\Models\StandaloneRedis;
+use App\Models\Team;
+use App\Services\DatabaseStartCommandExecutor;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Http;
+use Illuminate\Support\Facades\Process;
+use Illuminate\Support\Facades\Queue;
+use Illuminate\Support\Facades\Schema;
+use Spatie\Activitylog\Models\Activity;
+use Symfony\Component\Yaml\Yaml;
+
+uses(RefreshDatabase::class);
+
+beforeEach(function () {
+    InstanceSettings::forceCreate(['id' => 0]);
+    config(['app.maintenance.store' => 'array', 'cache.default' => 'array']);
+    Process::fake();
+    Queue::fake();
+    Server::flushIdentityMap();
+
+    $team = Team::factory()->create();
+    $privateKey = PrivateKey::factory()->create(['team_id' => $team->id]);
+    $server = Server::factory()->create(['team_id' => $team->id, 'private_key_id' => $privateKey->id]);
+    $this->destination = StandaloneDocker::query()->where('server_id', $server->id)->firstOrFail();
+    $project = Project::factory()->create(['team_id' => $team->id]);
+    $this->environment = Environment::factory()->create(['project_id' => $project->id]);
+
+    SharedEnvironmentVariable::query()->create([
+        'key' => 'RPW',
+        'value' => 's3cret',
+        'type' => 'environment',
+        'environment_id' => $this->environment->id,
+        'project_id' => $project->id,
+        'team_id' => $team->id,
+    ]);
+
+    $this->executor = new class
+    {
+        public array $commands = [];
+
+        public function execute(array $commands, $database, Activity $activity): Activity
+        {
+            $this->commands = $commands;
+
+            return $activity;
+        }
+    };
+    app()->instance(DatabaseStartCommandExecutor::class, $this->executor);
+});
+
+function redisLegacyQuotingDatabase(object $test, string $password, bool $legacy, array $otherData = []): StandaloneRedis
+{
+    $database = create_standalone_redis($test->environment->id, $test->destination, ['redis_password' => $password, 'image' => 'redis:7.2', ...$otherData]);
+    if ($legacy) {
+        DB::table($database->getTable())->where('id', $database->id)->update(['legacy_password_quoting' => true]);
+    }
+
+    return $database->fresh();
+}
+
+function redisLegacyQuotingStartCommand(object $executor, string $uuid): string
+{
+    foreach ($executor->commands as $command) {
+        if (preg_match("#^echo '([^']+)' \| base64 -d \| tee \S+/docker-compose\.yml#", $command, $matches)) {
+            return Yaml::parse(base64_decode($matches[1]))['services'][$uuid]['command'];
+        }
+    }
+
+    throw new RuntimeException('No docker-compose.yml was written.');
+}
+
+it('keeps the v4.3.23 server password and URL of a legacy database with a shared REDIS_PASSWORD reference', function () {
+    $database = redisLegacyQuotingDatabase($this, '{{environment.RPW}}', legacy: true, otherData: ['is_public' => true, 'public_port' => 16379]);
+
+    StartRedis::run($database, new Activity);
+
+    $database = $database->fresh();
+    $encodedReference = rawurlencode('{{environment.RPW}}');
+    expect(redisLegacyQuotingStartCommand($this->executor, $database->uuid))
+        ->toBe("redis-server --requirepass '{{environment.RPW}}' --appendonly yes")
+        ->and($database->internal_db_url)->toContain(":{$encodedReference}@")
+        ->and($database->external_db_url)->toContain(":{$encodedReference}@")
+        ->and($database->runtime_environment_variables()->where('key', 'REDIS_PASSWORD')->first()->value)->toBe('{{environment.RPW}}')
+        ->and($database->legacy_password_quoting)->toBeTrue();
+});
+
+it('keeps the unquoted v4.3.23 argument of a legacy password that quoting would change', function (string $password) {
+    $database = redisLegacyQuotingDatabase($this, $password, legacy: true);
+
+    StartRedis::run($database, new Activity);
+
+    expect(redisLegacyQuotingStartCommand($this->executor, $database->uuid))
+        ->toBe("redis-server --requirepass {$password} --appendonly yes");
+})->with([
+    'backslash' => 'ab\c',
+    'quote' => "a'b",
+    'space' => 'a b',
+    'semicolon' => 'ab;cd',
+]);
+
+it('starts a new database with the resolved shared REDIS_PASSWORD and shows it in the URLs', function () {
+    $database = redisLegacyQuotingDatabase($this, '{{environment.RPW}}', legacy: false, otherData: ['is_public' => true, 'public_port' => 16379]);
+
+    StartRedis::run($database, new Activity);
+
+    $database = $database->fresh();
+    expect(redisLegacyQuotingStartCommand($this->executor, $database->uuid))
+        ->toBe("redis-server --requirepass 's3cret' --appendonly yes")
+        ->and($database->internal_db_url)->toContain(':s3cret@')
+        ->and($database->external_db_url)->toContain(':s3cret@')
+        ->and($database->legacy_password_quoting)->toBeFalse();
+});
+
+it('quotes special characters of the password of a new database', function (string $password) {
+    SharedEnvironmentVariable::query()->where('key', 'RPW')->firstOrFail()->update(['value' => $password]);
+    $local = redisLegacyQuotingDatabase($this, $password, legacy: false);
+    $shared = redisLegacyQuotingDatabase($this, '{{environment.RPW}}', legacy: false);
+
+    StartRedis::run($local, new Activity);
+    $localCommand = redisLegacyQuotingStartCommand($this->executor, $local->uuid);
+    StartRedis::run($shared, new Activity);
+    $sharedCommand = redisLegacyQuotingStartCommand($this->executor, $shared->uuid);
+
+    $expected = 'redis-server --requirepass '.escapeshellarg($password).' --appendonly yes';
+    expect($localCommand)->toBe($expected)
+        ->and($sharedCommand)->toBe($expected)
+        ->and($shared->fresh()->internal_db_url)->toContain(':'.rawurlencode($password).'@');
+})->with([
+    'quote and space' => "pa ss'w",
+    'backslash' => 'ab\c',
+    'double quote' => 'a"b',
+]);
+
+it('quotes the password next to a custom redis.conf without requirepass', function () {
+    $database = redisLegacyQuotingDatabase($this, 'a b', legacy: false, otherData: ['redis_conf' => 'maxmemory 100mb']);
+
+    StartRedis::run($database, new Activity);
+
+    expect(redisLegacyQuotingStartCommand($this->executor, $database->uuid))
+        ->toBe("redis-server /usr/local/etc/redis/redis.conf --requirepass 'a b'");
+});
+
+it('quotes a remote secret password of a legacy database exactly and shows the reference in the URL', function () {
+    Http::fake(['https://api.doppler.com/*' => Http::response(['REDIS_PASSWORD' => 'ab\\c'])]);
+    $token = IntegrationToken::query()->create([
+        'team_id' => $this->environment->project->team_id,
+        'provider' => 'doppler',
+        'name' => 'Doppler',
+        'token' => 'the-secret-token',
+        'capabilities' => ['secrets'],
+    ]);
+    $database = redisLegacyQuotingDatabase($this, '{{vault.REDIS_PASSWORD}}', legacy: true);
+    $database->secretManagerLink()->create(['integration_token_id' => $token->id]);
+
+    expect($database->fresh()->internal_db_url)->toContain(':'.rawurlencode('{{vault.REDIS_PASSWORD}}').'@');
+
+    StartRedis::run($database->fresh(), new Activity);
+
+    expect(redisLegacyQuotingStartCommand($this->executor, $database->uuid))
+        ->toBe("redis-server --requirepass 'ab\\c' --appendonly yes");
+});
+
+it('marks only Redis databases that exist before the migration as legacy', function () {
+    $existing = create_standalone_redis($this->environment->id, $this->destination);
+
+    $migration = require database_path('migrations/2026_10_05_204113_add_legacy_password_quoting_to_standalone_redis.php');
+    $migration->down();
+    expect(Schema::hasColumn('standalone_redis', 'legacy_password_quoting'))->toBeFalse();
+    $migration->up();
+
+    $new = create_standalone_redis($this->environment->id, $this->destination);
+
+    expect($existing->fresh()->legacy_password_quoting)->toBeTrue()
+        ->and($new->fresh()->legacy_password_quoting)->toBeFalse();
+});
diff --git a/tests/Feature/SecretManagers/RemoteSecretResourceLifecycleTest.php b/tests/Feature/SecretManagers/RemoteSecretResourceLifecycleTest.php
index 1a8d128001..d3846d9ae3 100644
--- a/tests/Feature/SecretManagers/RemoteSecretResourceLifecycleTest.php
+++ b/tests/Feature/SecretManagers/RemoteSecretResourceLifecycleTest.php
@@ -199,7 +199,7 @@ test('redis remote passwords are escaped the same way in the environment and the
     $startCommand = (new ReflectionMethod($action, 'buildStartCommand'))->invoke($action);
 
     expect($environmentVariables)->toContain('REDIS_PASSWORD=p4$$word')
-        ->and($startCommand)->toContain('--requirepass p4$$word');
+        ->and($startCommand)->toContain("--requirepass 'p4\$\$word'");
 });
 
 test('a service restart keeps the service running when remote secrets cannot be fetched', function () {
diff --git a/tests/Feature/SecretManagers/SecretManagerLinkTest.php b/tests/Feature/SecretManagers/SecretManagerLinkTest.php
index 3cad814ea6..acaa33f7a7 100644
--- a/tests/Feature/SecretManagers/SecretManagerLinkTest.php
+++ b/tests/Feature/SecretManagers/SecretManagerLinkTest.php
@@ -264,7 +264,7 @@ test('redis remote credentials stay deployment-local and use raw values in the s
         ->and($username->fresh()->value)->toBe('{{vault.REDIS_USERNAME}}')
         ->and($environmentVariables)->toContain('REDIS_PASSWORD=p4$$$$word')
         ->and($environmentVariables)->toContain('REDIS_USERNAME=remote-user')
-        ->and($startCommand)->toContain('--requirepass p4$$$$word');
+        ->and($startCommand)->toContain("--requirepass 'p4\$\$\$\$word'");
 });
 
 test('all deployable environment-variable resources support secret managers', function (string $resourceClass) {