Replay empty tool inputs as objects

includes/class-openclawp-message-adapter.php

@@ -96,12 +96,30 @@ private static function tool_call_part( array $message ) {
 			return null;
 		}
 		$id   = (string) ( $meta['tool_call_id'] ?? '' );
-		$args = is_array( $payload['parameters'] ?? null ) ? $payload['parameters'] : array();
+		$args = self::function_call_args( $payload['parameters'] ?? array() );
 
 		$call = new \WordPress\AiClient\Tools\DTO\FunctionCall( '' !== $id ? $id : null, $name, $args );
 		return new \WordPress\AiClient\Messages\DTO\MessagePart( $call );
 	}
 
+	/**
+	 * Return provider-safe function-call args for transcript replay.
+	 *
+	 * Anthropic requires `tool_use.input` to be a JSON object. PHP encodes an
+	 * empty array as `[]`, so a no-argument tool call must be carried as an
+	 * empty object when replayed through WP AI Client.
+	 *
+	 * @param mixed $parameters Stored tool parameters.
+	 * @return mixed
+	 */
+	private static function function_call_args( $parameters ) {
+		if ( array() === $parameters ) {
+			return new \stdClass();
+		}
+
+		return is_array( $parameters ) ? $parameters : array();
+	}
+
 	/**
 	 * Build a `MessagePart` wrapping the `FunctionResponse` for a stored
 	 * `tool_result` transcript message, matched to its call by `tool_call_id`.

tests/unit/MessageAdapterTest.php

@@ -69,6 +69,27 @@ public function test_to_ai_client_messages_round_trips_tool_mediation_parts(): v
 		$this->assertSame( array( 'ok' => true ), $response->getResponse() );
 	}
 
+	public function test_to_ai_client_messages_replays_empty_tool_parameters_as_object(): void {
+		self::install_ai_client_stubs();
+
+		$output = OpenclaWP_Message_Adapter::to_ai_client_messages(
+			array(
+				array(
+					'type'     => 'tool_call',
+					'payload'  => array(
+						'tool_name'  => 'client/openclawp__current-context',
+						'parameters' => array(),
+					),
+					'metadata' => array( 'tool_call_id' => 'call-empty' ),
+				),
+			)
+		);
+
+		$call = $output[0]->getParts()[0]->getContent();
+		$this->assertInstanceOf( \stdClass::class, $call->getArgs() );
+		$this->assertSame( '{}', json_encode( $call->getArgs() ) );
+	}
+
 	public function test_last_assistant_text_returns_most_recent_assistant_message(): void {
 		$messages = array(
 			array( 'role' => 'user',      'content' => 'q1' ),
@@ -200,9 +221,10 @@ public function getContent() {
 final class FunctionCall {
 	private ?string $id;
 	private string $name;
-	private array $args;
+	/** @var mixed */
+	private $args;
 
-	public function __construct( ?string $id, string $name, array $args ) {
+	public function __construct( ?string $id, string $name, $args ) {
 		$this->id   = $id;
 		$this->name = $name;
 		$this->args = $args;
@@ -216,7 +238,7 @@ public function getName(): string {
 		return $this->name;
 	}
 
-	public function getArgs(): array {
+	public function getArgs() {
 		return $this->args;
 	}
 }