diff --git a/src/Symfony/Component/JsonEncoder/Encode/PhpAstBuilder.php b/src/Symfony/Component/JsonEncoder/Encode/PhpAstBuilder.php
index dc4dee96507be..443961307e1f2 100644
--- a/src/Symfony/Component/JsonEncoder/Encode/PhpAstBuilder.php
+++ b/src/Symfony/Component/JsonEncoder/Encode/PhpAstBuilder.php
@@ -196,13 +196,17 @@ private function buildClosureStatements(DataModelNodeInterface $dataModelNode, a
                 ];
             }
 
+            $escapedKey = $dataModelNode->getType()->getCollectionKeyType()->isIdentifiedBy(TypeIdentifier::INT)
+                ? new Ternary($this->builder->funcCall('is_int', [$this->builder->var('key')]), $this->builder->var('key'), $this->escapeString($this->builder->var('key')))
+                : $this->escapeString($this->builder->var('key'));
+
             return [
                 new Expression(new Yield_($this->builder->val('{'))),
                 new Expression(new Assign($this->builder->var('prefix'), $this->builder->val(''))),
                 new Foreach_($accessor, $dataModelNode->getItemNode()->getAccessor()->toPhpExpr(), [
                     'keyVar' => $this->builder->var('key'),
                     'stmts' => [
-                        new Expression(new Assign($this->builder->var('key'), $this->escapeString($this->builder->var('key')))),
+                        new Expression(new Assign($this->builder->var('key'), $escapedKey)),
                         new Expression(new Yield_(new Encapsed([
                             $this->builder->var('prefix'),
                             new EncapsedStringPart('"'),
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Decode/DecoderGeneratorTest.php b/src/Symfony/Component/JsonEncoder/Tests/Decode/DecoderGeneratorTest.php
index a298343c95fe5..20437eb492d94 100644
--- a/src/Symfony/Component/JsonEncoder/Tests/Decode/DecoderGeneratorTest.php
+++ b/src/Symfony/Component/JsonEncoder/Tests/Decode/DecoderGeneratorTest.php
@@ -95,12 +95,13 @@ public static function generatedDecoderDataProvider(): iterable
         yield ['list', Type::list()];
         yield ['object_list', Type::list(Type::object(ClassicDummy::class))];
         yield ['nullable_object_list', Type::nullable(Type::list(Type::object(ClassicDummy::class)))];
-        yield ['iterable_list', Type::iterable(key: Type::int(), asList: true)];
 
         yield ['dict', Type::dict()];
         yield ['object_dict', Type::dict(Type::object(ClassicDummy::class))];
         yield ['nullable_object_dict', Type::nullable(Type::dict(Type::object(ClassicDummy::class)))];
-        yield ['iterable_dict', Type::iterable(key: Type::string())];
+
+        yield ['iterable', Type::iterable()];
+        yield ['object_iterable', Type::iterable(Type::object(ClassicDummy::class))];
 
         yield ['object', Type::object(ClassicDummy::class)];
         yield ['nullable_object', Type::nullable(Type::object(ClassicDummy::class))];
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Encode/EncoderGeneratorTest.php b/src/Symfony/Component/JsonEncoder/Tests/Encode/EncoderGeneratorTest.php
index 75f026324bf61..1c1c6fbeaebf6 100644
--- a/src/Symfony/Component/JsonEncoder/Tests/Encode/EncoderGeneratorTest.php
+++ b/src/Symfony/Component/JsonEncoder/Tests/Encode/EncoderGeneratorTest.php
@@ -21,6 +21,7 @@
 use Symfony\Component\JsonEncoder\Mapping\PropertyMetadataLoaderInterface;
 use Symfony\Component\JsonEncoder\Tests\Fixtures\Enum\DummyBackedEnum;
 use Symfony\Component\JsonEncoder\Tests\Fixtures\Enum\DummyEnum;
+use Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy;
 use Symfony\Component\JsonEncoder\Tests\Fixtures\Model\DummyWithNameAttributes;
 use Symfony\Component\JsonEncoder\Tests\Fixtures\Model\DummyWithNormalizerAttributes;
 use Symfony\Component\JsonEncoder\Tests\Fixtures\Model\DummyWithOtherDummies;
@@ -92,12 +93,12 @@ public static function generatedEncoderDataProvider(): iterable
         yield ['object_list', Type::list(Type::object(DummyWithNameAttributes::class))];
         yield ['nullable_object_list', Type::nullable(Type::list(Type::object(DummyWithNameAttributes::class)))];
 
-        yield ['iterable_list', Type::iterable(key: Type::int(), asList: true)];
-
         yield ['dict', Type::dict()];
         yield ['object_dict', Type::dict(Type::object(DummyWithNameAttributes::class))];
         yield ['nullable_object_dict', Type::nullable(Type::dict(Type::object(DummyWithNameAttributes::class)))];
-        yield ['iterable_dict', Type::iterable(key: Type::string())];
+
+        yield ['iterable', Type::iterable()];
+        yield ['object_iterable', Type::iterable(Type::object(ClassicDummy::class))];
 
         yield ['object', Type::object(DummyWithNameAttributes::class)];
         yield ['nullable_object', Type::nullable(Type::object(DummyWithNameAttributes::class))];
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_dict.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable.php
similarity index 100%
rename from src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_dict.php
rename to src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable.php
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_dict.stream.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable.stream.php
similarity index 74%
rename from src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_dict.stream.php
rename to src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable.stream.php
index 67543a3171a1e..cbd2e10b0e1e7 100644
--- a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_dict.stream.php
+++ b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable.stream.php
@@ -1,7 +1,7 @@
 <?php
 
 return static function (mixed $stream, \Psr\Container\ContainerInterface $denormalizers, \Symfony\Component\JsonEncoder\Decode\LazyInstantiator $instantiator, array $options): mixed {
-    $providers['iterable<string,mixed>'] = static function ($stream, $offset, $length) use ($options, $denormalizers, $instantiator, &$providers) {
+    $providers['iterable'] = static function ($stream, $offset, $length) use ($options, $denormalizers, $instantiator, &$providers) {
         $data = \Symfony\Component\JsonEncoder\Decode\Splitter::splitDict($stream, $offset, $length);
         $iterable = static function ($stream, $data) use ($options, $denormalizers, $instantiator, &$providers) {
             foreach ($data as $k => $v) {
@@ -10,5 +10,5 @@
         };
         return $iterable($stream, $data);
     };
-    return $providers['iterable<string,mixed>']($stream, 0, null);
+    return $providers['iterable']($stream, 0, null);
 };
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.php
deleted file mode 100644
index f0645e3f291d1..0000000000000
--- a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.php
+++ /dev/null
@@ -1,5 +0,0 @@
-<?php
-
-return static function (string|\Stringable $string, \Psr\Container\ContainerInterface $denormalizers, \Symfony\Component\JsonEncoder\Decode\Instantiator $instantiator, array $options): mixed {
-    return \Symfony\Component\JsonEncoder\Decode\NativeDecoder::decodeString((string) $string);
-};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.stream.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.stream.php
deleted file mode 100644
index 1ae72ccd7391e..0000000000000
--- a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/iterable_list.stream.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-
-return static function (mixed $stream, \Psr\Container\ContainerInterface $denormalizers, \Symfony\Component\JsonEncoder\Decode\LazyInstantiator $instantiator, array $options): mixed {
-    $providers['iterable<int,mixed>'] = static function ($stream, $offset, $length) use ($options, $denormalizers, $instantiator, &$providers) {
-        $data = \Symfony\Component\JsonEncoder\Decode\Splitter::splitList($stream, $offset, $length);
-        $iterable = static function ($stream, $data) use ($options, $denormalizers, $instantiator, &$providers) {
-            foreach ($data as $k => $v) {
-                yield $k => \Symfony\Component\JsonEncoder\Decode\NativeDecoder::decodeStream($stream, $v[0], $v[1]);
-            }
-        };
-        return $iterable($stream, $data);
-    };
-    return $providers['iterable<int,mixed>']($stream, 0, null);
-};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.php
new file mode 100644
index 0000000000000..0dfbb689419cb
--- /dev/null
+++ b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.php
@@ -0,0 +1,18 @@
+<?php
+
+return static function (string|\Stringable $string, \Psr\Container\ContainerInterface $denormalizers, \Symfony\Component\JsonEncoder\Decode\Instantiator $instantiator, array $options): mixed {
+    $providers['iterable<int|string,Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy>'] = static function ($data) use ($options, $denormalizers, $instantiator, &$providers) {
+        $iterable = static function ($data) use ($options, $denormalizers, $instantiator, &$providers) {
+            foreach ($data as $k => $v) {
+                yield $k => $providers['Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy']($v);
+            }
+        };
+        return $iterable($data);
+    };
+    $providers['Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy'] = static function ($data) use ($options, $denormalizers, $instantiator, &$providers) {
+        return $instantiator->instantiate(\Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy::class, \array_filter(['id' => $data['id'] ?? '_symfony_missing_value', 'name' => $data['name'] ?? '_symfony_missing_value'], static function ($v) {
+            return '_symfony_missing_value' !== $v;
+        }));
+    };
+    return $providers['iterable<int|string,Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy>'](\Symfony\Component\JsonEncoder\Decode\NativeDecoder::decodeString((string) $string));
+};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.stream.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.stream.php
new file mode 100644
index 0000000000000..cfdf671d8a9bc
--- /dev/null
+++ b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/decoder/object_iterable.stream.php
@@ -0,0 +1,26 @@
+<?php
+
+return static function (mixed $stream, \Psr\Container\ContainerInterface $denormalizers, \Symfony\Component\JsonEncoder\Decode\LazyInstantiator $instantiator, array $options): mixed {
+    $providers['iterable<int|string,Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy>'] = static function ($stream, $offset, $length) use ($options, $denormalizers, $instantiator, &$providers) {
+        $data = \Symfony\Component\JsonEncoder\Decode\Splitter::splitDict($stream, $offset, $length);
+        $iterable = static function ($stream, $data) use ($options, $denormalizers, $instantiator, &$providers) {
+            foreach ($data as $k => $v) {
+                yield $k => $providers['Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy']($stream, $v[0], $v[1]);
+            }
+        };
+        return $iterable($stream, $data);
+    };
+    $providers['Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy'] = static function ($stream, $offset, $length) use ($options, $denormalizers, $instantiator, &$providers) {
+        $data = \Symfony\Component\JsonEncoder\Decode\Splitter::splitDict($stream, $offset, $length);
+        return $instantiator->instantiate(\Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy::class, static function ($object) use ($stream, $data, $options, $denormalizers, $instantiator, &$providers) {
+            foreach ($data as $k => $v) {
+                match ($k) {
+                    'id' => $object->id = \Symfony\Component\JsonEncoder\Decode\NativeDecoder::decodeStream($stream, $v[0], $v[1]),
+                    'name' => $object->name = \Symfony\Component\JsonEncoder\Decode\NativeDecoder::decodeStream($stream, $v[0], $v[1]),
+                    default => null,
+                };
+            }
+        });
+    };
+    return $providers['iterable<int|string,Symfony\Component\JsonEncoder\Tests\Fixtures\Model\ClassicDummy>']($stream, 0, null);
+};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable_dict.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable.php
similarity index 100%
rename from src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable_dict.php
rename to src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable.php
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable_list.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable_list.php
deleted file mode 100644
index 6eec711284d61..0000000000000
--- a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/iterable_list.php
+++ /dev/null
@@ -1,5 +0,0 @@
-<?php
-
-return static function (mixed $data, \Psr\Container\ContainerInterface $normalizers, array $options): \Traversable {
-    yield \json_encode($data);
-};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/object_iterable.php b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/object_iterable.php
new file mode 100644
index 0000000000000..e1780548e7a35
--- /dev/null
+++ b/src/Symfony/Component/JsonEncoder/Tests/Fixtures/encoder/object_iterable.php
@@ -0,0 +1,17 @@
+<?php
+
+return static function (mixed $data, \Psr\Container\ContainerInterface $normalizers, array $options): \Traversable {
+    yield '{';
+    $prefix = '';
+    foreach ($data as $key => $value) {
+        $key = is_int($key) ? $key : \substr(\json_encode($key), 1, -1);
+        yield "{$prefix}\"{$key}\":";
+        yield '{"id":';
+        yield \json_encode($value->id);
+        yield ',"name":';
+        yield \json_encode($value->name);
+        yield '}';
+        $prefix = ',';
+    }
+    yield '}';
+};
diff --git a/src/Symfony/Component/JsonEncoder/Tests/JsonDecoderTest.php b/src/Symfony/Component/JsonEncoder/Tests/JsonDecoderTest.php
index b0a1b3d12ed1e..1e3d72a8b1e36 100644
--- a/src/Symfony/Component/JsonEncoder/Tests/JsonDecoderTest.php
+++ b/src/Symfony/Component/JsonEncoder/Tests/JsonDecoderTest.php
@@ -64,16 +64,29 @@ public function testDecodeCollection()
     {
         $decoder = JsonDecoder::create(decodersDir: $this->decodersDir, lazyGhostsDir: $this->lazyGhostsDir);
 
-        $this->assertDecoded($decoder, [['foo' => 1, 'bar' => 2], ['foo' => 3]], '[{"foo": 1, "bar": 2}, {"foo": 3}]', Type::list(Type::dict(Type::int())));
+        $this->assertDecoded(
+            $decoder,
+            [true, false],
+            '{"0": true, "1": false}',
+            Type::array(Type::bool()),
+        );
+
+        $this->assertDecoded(
+            $decoder,
+            [true, false],
+            '[true, false]',
+            Type::list(Type::bool()),
+        );
+
         $this->assertDecoded($decoder, function (mixed $decoded) {
             $this->assertIsIterable($decoded);
-            $array = [];
-            foreach ($decoded as $item) {
-                $array[] = iterator_to_array($item);
-            }
+            $this->assertSame([true, false], iterator_to_array($decoded));
+        }, '{"0": true, "1": false}', Type::iterable(Type::bool()));
 
-            $this->assertSame([['foo' => 1, 'bar' => 2], ['foo' => 3]], $array);
-        }, '[{"foo": 1, "bar": 2}, {"foo": 3}]', Type::iterable(Type::iterable(Type::int()), Type::int(), asList: true));
+        $this->assertDecoded($decoder, function (mixed $decoded) {
+            $this->assertIsIterable($decoded);
+            $this->assertSame([true, false], iterator_to_array($decoded));
+        }, '{"0": true, "1": false}', Type::iterable(Type::bool(), Type::int()));
     }
 
     public function testDecodeObject()
diff --git a/src/Symfony/Component/JsonEncoder/Tests/JsonEncoderTest.php b/src/Symfony/Component/JsonEncoder/Tests/JsonEncoderTest.php
index de584c64f29e0..8cab0f3474c7b 100644
--- a/src/Symfony/Component/JsonEncoder/Tests/JsonEncoderTest.php
+++ b/src/Symfony/Component/JsonEncoder/Tests/JsonEncoderTest.php
@@ -81,6 +81,33 @@ public function testEncodeUnion()
         $this->assertEncoded('{"value":null}', $dummy, Type::object(DummyWithUnionProperties::class));
     }
 
+    public function testEncodeCollection()
+    {
+        $this->assertEncoded(
+            '{"0":{"id":1,"name":"dummy"},"1":{"id":1,"name":"dummy"}}',
+            [new ClassicDummy(), new ClassicDummy()],
+            Type::array(Type::object(ClassicDummy::class)),
+        );
+
+        $this->assertEncoded(
+            '[{"id":1,"name":"dummy"},{"id":1,"name":"dummy"}]',
+            [new ClassicDummy(), new ClassicDummy()],
+            Type::list(Type::object(ClassicDummy::class)),
+        );
+
+        $this->assertEncoded(
+            '{"0":{"id":1,"name":"dummy"},"1":{"id":1,"name":"dummy"}}',
+            new \ArrayObject([new ClassicDummy(), new ClassicDummy()]),
+            Type::iterable(Type::object(ClassicDummy::class)),
+        );
+
+        $this->assertEncoded(
+            '{"0":{"id":1,"name":"dummy"},"1":{"id":1,"name":"dummy"}}',
+            new \ArrayObject([new ClassicDummy(), new ClassicDummy()]),
+            Type::iterable(Type::object(ClassicDummy::class), Type::int()),
+        );
+    }
+
     public function testEncodeObject()
     {
         $dummy = new ClassicDummy();