Add setModel() convenience method to Session

src/Contracts/CopilotSession.php

@@ -6,6 +6,7 @@
 
 use Closure;
 use Revolution\Copilot\Enums\SessionEventType;
+use Revolution\Copilot\Exceptions\JsonRpcException;
 use Revolution\Copilot\Rpc\SessionRpc;
 use Revolution\Copilot\Types\SessionEvent;
 
@@ -24,6 +25,13 @@ public function id(): string;
      */
     public function rpc(): SessionRpc;
 
+    /**
+     * Switch the model for this session.
+     *
+     * @throws JsonRpcException
+     */
+    public function setModel(string $modelId): void;
+
     /**
      * Send a message to this session.
      */

src/Session.php

@@ -20,6 +20,7 @@
 use Revolution\Copilot\JsonRpc\JsonRpcClient;
 use Revolution\Copilot\Rpc\SessionRpc;
 use Revolution\Copilot\Support\PermissionRequestKind;
+use Revolution\Copilot\Types\Rpc\SessionModelSwitchToParams;
 use Revolution\Copilot\Types\SessionEvent;
 use Revolution\Copilot\Types\SessionHooks;
 use Revolution\Copilot\Types\UserInputRequest;
@@ -662,6 +663,16 @@ public function destroy(): void
         $this->hooks = null;
     }
 
+    /**
+     * Switch the model for this session.
+     *
+     * @throws JsonRpcException
+     */
+    public function setModel(string $modelId): void
+    {
+        $this->rpc()->model()->switchTo(new SessionModelSwitchToParams(modelId: $modelId));
+    }
+
     /**
      * Abort the currently processing message.
      *

src/Testing/FakeSession.php

@@ -47,6 +47,11 @@ public function rpc(): SessionRpc
         );
     }
 
+    public function setModel(string $modelId): void
+    {
+        // No-op in fake
+    }
+
     public function send(string $prompt, ?array $attachments = null, ?string $mode = null): string
     {
         $this->recorded[] = [

tests/Feature/SessionTest.php

@@ -299,6 +299,20 @@
         $session->abort();
     });
 
+    it('setModel calls session.model.switchTo via rpc', function () {
+        $mockClient = Mockery::mock(JsonRpcClient::class);
+        $mockClient->shouldReceive('request')
+            ->with('session.model.switchTo', [
+                'modelId' => 'claude-sonnet-4',
+                'sessionId' => 'test-session',
+            ])
+            ->once()
+            ->andReturn(['modelId' => 'claude-sonnet-4']);
+
+        $session = new Session('test-session', $mockClient);
+        $session->setModel('claude-sonnet-4');
+    });
+
     it('handlePermissionRequest uses registered handler', function () {
         $mockClient = Mockery::mock(JsonRpcClient::class);
         $session = new Session('test-session', $mockClient);