diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index 8b0759f7a6..a9154651cf 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -24,7 +24,7 @@ jobs:
   tests-linux:
     name: Tests (Linux, PHP ${{ matrix.php-versions }})
     runs-on: ubuntu-latest
-    continue-on-error: false
+    continue-on-error: ${{ matrix.experimental || false }}
     strategy:
       fail-fast: false
       matrix:
@@ -33,6 +33,8 @@ jobs:
           - php-versions: "8.3"
           - php-versions: "8.4"
           - php-versions: "8.5"
+          - php-versions: "8.6"
+            experimental: true
     env:
       GOMAXPROCS: 10
       LIBRARY_PATH: ${{ github.workspace }}/watcher/target/lib
diff --git a/testdata/session-handler.php b/testdata/session-handler.php
index ba518c13d2..1671bf2a72 100644
--- a/testdata/session-handler.php
+++ b/testdata/session-handler.php
@@ -3,7 +3,7 @@
 require_once __DIR__.'/_executor.php';
 
 // Custom session handler class
-class TestSessionHandler implements SessionHandlerInterface
+class TestSessionHandler implements SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface
 {
     private static array $data = [];
 
@@ -38,6 +38,23 @@ public function gc(int $max_lifetime): int|false
     {
         return 0;
     }
+
+    public function create_sid(): string
+    {
+        return bin2hex(random_bytes(16));
+    }
+
+    public function validateId(string $id): bool
+    {
+        // session.use_strict_mode is off in these tests: accept any id, as
+        // PHP did before 8.6 deprecated handlers without this method
+        return true;
+    }
+
+    public function updateTimestamp(string $id, string $data): bool
+    {
+        return true;
+    }
 }
 
 return function () {
diff --git a/testdata/session_deadlock.php b/testdata/session_deadlock.php
index 4407e79345..393999795b 100644
--- a/testdata/session_deadlock.php
+++ b/testdata/session_deadlock.php
@@ -4,7 +4,7 @@
 
 // Self-contained repro of https://github.com/php/frankenphp/issues/2368
 if (!class_exists('StrictSessionHandler', false)) {
-    abstract class AbstractSessionHandler implements SessionHandlerInterface, SessionUpdateTimestampHandlerInterface
+    abstract class AbstractSessionHandler implements SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface
     {
         private string $sessionName;
         private string $prefetchId;
@@ -21,6 +21,11 @@ abstract protected function doRead(string $sessionId): string;
         abstract protected function doWrite(string $sessionId, string $data): bool;
         abstract protected function doDestroy(string $sessionId): bool;
 
+        public function create_sid(): string
+        {
+            return bin2hex(random_bytes(16));
+        }
+
         public function validateId(string $sessionId): bool
         {
             $this->prefetchData = $this->read($sessionId);
diff --git a/testdata/worker-with-session-handler.php b/testdata/worker-with-session-handler.php
index 218c54769e..ad7d66a238 100644
--- a/testdata/worker-with-session-handler.php
+++ b/testdata/worker-with-session-handler.php
@@ -1,7 +1,7 @@
 <?php
 
 // Custom session handler defined BEFORE the worker loop
-class PreLoopSessionHandler implements SessionHandlerInterface
+class PreLoopSessionHandler implements SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface
 {
     private static array $data = [];
 
@@ -36,6 +36,23 @@ public function gc(int $max_lifetime): int|false
     {
         return 0;
     }
+
+    public function create_sid(): string
+    {
+        return bin2hex(random_bytes(16));
+    }
+
+    public function validateId(string $id): bool
+    {
+        // session.use_strict_mode is off in these tests: accept any id, as
+        // PHP did before 8.6 deprecated handlers without this method
+        return true;
+    }
+
+    public function updateTimestamp(string $id, string $data): bool
+    {
+        return true;
+    }
 }
 
 // Set the session handler BEFORE the worker loop