diff --git a/agent/src/Envelope.php b/agent/src/Envelope.php
index e6eb8ff..600f969 100644
--- a/agent/src/Envelope.php
+++ b/agent/src/Envelope.php
@@ -77,6 +77,13 @@ static function (EnvelopeItem $item) use ($callback) {
         );
     }
 
+    public function appendIngestPath(string $version): void
+    {
+        foreach ($this->items as $item) {
+            $item->appendIngestPath($version);
+        }
+    }
+
     public function __toString()
     {
         $data = implode(
diff --git a/agent/src/EnvelopeForwarder.php b/agent/src/EnvelopeForwarder.php
index 254225e..74ab556 100644
--- a/agent/src/EnvelopeForwarder.php
+++ b/agent/src/EnvelopeForwarder.php
@@ -83,9 +83,12 @@ public function forward(Envelope $envelope): PromiseInterface
             return resolve(null);
         }
 
+        $client = self::IDENTIFIER . '/' . self::VERSION;
+        $envelope->appendIngestPath($client);
+
         $authHeader = [
             'sentry_version=' . self::PROTOCOL_VERSION,
-            'sentry_client=' . self::IDENTIFIER . '/' . self::VERSION,
+            'sentry_client=' . $client,
             'sentry_key=' . $dsn->getPublicKey(),
         ];
 
@@ -95,7 +98,7 @@ public function forward(Envelope $envelope): PromiseInterface
         return (new Browser())->withTimeout($this->timeout)->post(
             $dsn->getEnvelopeApiEndpointUrl(),
             [
-                'User-Agent' => self::IDENTIFIER . '/' . self::VERSION,
+                'User-Agent' => $client,
                 'Content-Type' => Envelope::CONTENT_TYPE,
                 'X-Sentry-Auth' => 'Sentry ' . implode(', ', $authHeader),
             ],
diff --git a/agent/src/EnvelopeItem.php b/agent/src/EnvelopeItem.php
index c850553..46f7b5f 100644
--- a/agent/src/EnvelopeItem.php
+++ b/agent/src/EnvelopeItem.php
@@ -4,15 +4,23 @@
 
 namespace Sentry\Agent;
 
+use Sentry\Util\JSON;
+
 /**
  * @internal
  *
  * @phpstan-type EnvelopeItemHeader array{
  *     type: string,
+ *     length?: int,
  * }
  */
 class EnvelopeItem
 {
+    private const EVENT_ITEM_TYPES_WITH_INGEST_PATH = [
+        'event' => true,
+        'transaction' => true,
+    ];
+
     /**
      * @var EnvelopeItemHeader The envelope item header
      */
@@ -46,6 +54,39 @@ public function getData(): string
         return $this->data;
     }
 
+    public function appendIngestPath(string $version): void
+    {
+        if (!isset(self::EVENT_ITEM_TYPES_WITH_INGEST_PATH[$this->header['type']])) {
+            return;
+        }
+
+        $payload = json_decode($this->data, true);
+
+        if (!\is_array($payload)) {
+            return;
+        }
+
+        if (!isset($payload['ingest_path']) || !\is_array($payload['ingest_path'])) {
+            $payload['ingest_path'] = [];
+        }
+
+        $payload['ingest_path'][] = [
+            'version' => $version,
+        ];
+
+        try {
+            $data = JSON::encode($payload);
+        } catch (\Throwable $e) {
+            return;
+        }
+
+        $this->data = $data;
+
+        if (isset($this->header['length'])) {
+            $this->header['length'] = \strlen($this->data);
+        }
+    }
+
     public function __toString()
     {
         return json_encode($this->header) . "\n" . $this->data;
diff --git a/agent/tests/AgentForwardingTest.php b/agent/tests/AgentForwardingTest.php
index 4698e42..ab65298 100644
--- a/agent/tests/AgentForwardingTest.php
+++ b/agent/tests/AgentForwardingTest.php
@@ -5,6 +5,7 @@
 namespace Sentry\Agent\Tests;
 
 use PHPUnit\Framework\TestCase;
+use Sentry\Agent\EnvelopeForwarder;
 use Sentry\Event;
 use Sentry\Options;
 use Sentry\Serializer\PayloadSerializer;
@@ -32,6 +33,10 @@ public function testAgentForwardsEnvelopeToUpstream(): void
         $this->assertEquals(1, $serverOutput['request_count']);
         $this->assertStringContainsString('Hello from agent test!', $serverOutput['body']);
         $this->assertStringContainsString('"type":"event"', $serverOutput['body']);
+        $this->assertStringContainsString(
+            '"ingest_path":[{"version":"' . str_replace('/', '\/', EnvelopeForwarder::IDENTIFIER . '/' . EnvelopeForwarder::VERSION) . '"}]',
+            $serverOutput['body']
+        );
 
         // Verify the correct headers were sent
         $this->assertArrayHasKey('X-Sentry-Auth', $serverOutput['headers']);
diff --git a/agent/tests/EnvelopeTest.php b/agent/tests/EnvelopeTest.php
index 92daf53..6ad6e14 100644
--- a/agent/tests/EnvelopeTest.php
+++ b/agent/tests/EnvelopeTest.php
@@ -6,6 +6,8 @@
 
 use PHPUnit\Framework\TestCase;
 use Sentry\Agent\Envelope;
+use Sentry\Agent\EnvelopeForwarder;
+use Sentry\Agent\EnvelopeItem;
 
 class EnvelopeTest extends TestCase
 {
@@ -51,6 +53,99 @@ public function testCanParseEnvelopeWith2Items(): void
         $this->assertEquals($payload, (string) $envelope);
     }
 
+    public function testAppendIngestPathToEventItem(): void
+    {
+        $envelope = new Envelope(
+            ['dsn' => 'http://public@example.com/1'],
+            [new EnvelopeItem(['type' => 'event'], '{"message":"test"}')]
+        );
+
+        $envelope->appendIngestPath($this->getIngestPathVersion());
+
+        $payload = json_decode($envelope->getItems()[0]->getData(), true);
+
+        $this->assertSame([['version' => $this->getIngestPathVersion()]], $payload['ingest_path']);
+    }
+
+    public function testAppendIngestPathPreservesExistingEntries(): void
+    {
+        $envelope = new Envelope(
+            ['dsn' => 'http://public@example.com/1'],
+            [
+                new EnvelopeItem(
+                    ['type' => 'transaction'],
+                    '{"transaction":"/test","ingest_path":[{"version":"relay/1.0.0","public_key":"abc"}]}'
+                ),
+            ]
+        );
+
+        $envelope->appendIngestPath($this->getIngestPathVersion());
+
+        $payload = json_decode($envelope->getItems()[0]->getData(), true);
+
+        $this->assertSame(
+            [
+                ['version' => 'relay/1.0.0', 'public_key' => 'abc'],
+                ['version' => $this->getIngestPathVersion()],
+            ],
+            $payload['ingest_path']
+        );
+    }
+
+    public function testAppendIngestPathUpdatesLengthHeader(): void
+    {
+        $envelope = new Envelope(
+            ['dsn' => 'http://public@example.com/1'],
+            [new EnvelopeItem(['type' => 'event', 'length' => 18], '{"message":"test"}')]
+        );
+
+        $envelope->appendIngestPath($this->getIngestPathVersion());
+
+        $item = $envelope->getItems()[0];
+
+        $this->assertSame(\strlen($item->getData()), $item->getHeader()['length']);
+    }
+
+    public function testAppendIngestPathReplacesInvalidExistingIngestPath(): void
+    {
+        $envelope = new Envelope(
+            ['dsn' => 'http://public@example.com/1'],
+            [new EnvelopeItem(['type' => 'event'], '{"message":"test","ingest_path":"invalid"}')]
+        );
+
+        $envelope->appendIngestPath($this->getIngestPathVersion());
+
+        $payload = json_decode($envelope->getItems()[0]->getData(), true);
+
+        $this->assertSame([['version' => $this->getIngestPathVersion()]], $payload['ingest_path']);
+    }
+
+    public function testAppendIngestPathDoesNotMutateUnsupportedItems(): void
+    {
+        foreach (['log', 'check_in', 'profile', 'attachment'] as $type) {
+            $envelope = new Envelope(
+                ['dsn' => 'http://public@example.com/1'],
+                [new EnvelopeItem(['type' => $type], '{"message":"test"}')]
+            );
+
+            $envelope->appendIngestPath($this->getIngestPathVersion());
+
+            $this->assertSame('{"message":"test"}', $envelope->getItems()[0]->getData());
+        }
+    }
+
+    public function testAppendIngestPathDoesNotMutateMalformedJson(): void
+    {
+        $envelope = new Envelope(
+            ['dsn' => 'http://public@example.com/1'],
+            [new EnvelopeItem(['type' => 'event'], '{"message":')]
+        );
+
+        $envelope->appendIngestPath($this->getIngestPathVersion());
+
+        $this->assertSame('{"message":', $envelope->getItems()[0]->getData());
+    }
+
     private function getFixture(string $name): string
     {
         $fixture = file_get_contents(__DIR__ . "/fixtures/envelopes/{$name}.dat");
@@ -62,4 +157,9 @@ private function getFixture(string $name): string
         // To make it easier to edit the fixtures, we remove the trailing new line
         return rtrim($fixture, "\n");
     }
+
+    private function getIngestPathVersion(): string
+    {
+        return EnvelopeForwarder::IDENTIFIER . '/' . EnvelopeForwarder::VERSION;
+    }
 }
diff --git a/bin/sentry-agent b/bin/sentry-agent
index 07aea35..2018297 100755
Binary files a/bin/sentry-agent and b/bin/sentry-agent differ
diff --git a/bin/sentry-agent.sig b/bin/sentry-agent.sig
index 3f96e06..cee0682 100644
--- a/bin/sentry-agent.sig
+++ b/bin/sentry-agent.sig
@@ -1 +1 @@
-C5A1B020D608BDEF9E7D690A7DA18DF1BE0F3FF534304B3CED4734096A415F63B448F8156224E80F530CF203582C124CE04F4BABF968F5A905DA83199B5F6EF9
+D8B94BAD7E5B61D6310089C043AA6B9A3BEFD4FB4B41752004863AB4B822A2A43B49CC2587FB83446D8AA5AC8FE6A5AA6095D8DC932DE00334D1359F70C1D9A8