feat: add OpenRouter reasoning mode support (v0.4.9)

Enables reasoning-capable models (Grok 4.1 Fast, DeepSeek-R1, etc.)
via new admin settings: Enable Reasoning toggle and Reasoning Effort
selector. Provider auto-injects reasoning params when enabled; callers
can override per-call via options array. Response parser captures
reasoning_tokens and reasoning_content for visibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/admin/class-settings-fields-extended.php

@@ -80,6 +80,31 @@ class PRAutoBlogger_Settings_Fields_Extended {
 	 */
 	public static function get_fields(): array {
 		return [
+			// ── AI Models (extended) ────────────────────────────────────
+			[
+				'id'          => 'prautoblogger_reasoning_enabled',
+				'label'       => __( 'Enable Reasoning', 'prautoblogger' ),
+				'type'        => 'toggle',
+				'section'     => 'prautoblogger_models',
+				'default'     => '0',
+				'description' => __( 'Send reasoning instructions to models that support it (e.g. Grok, DeepSeek-R1). Reasoning tokens are billed as output tokens — expect higher costs per call. Models that don\'t support reasoning will ignore this.', 'prautoblogger' ),
+			],
+			[
+				'id'      => 'prautoblogger_reasoning_effort',
+				'label'   => __( 'Reasoning Effort', 'prautoblogger' ),
+				'type'    => 'select',
+				'section' => 'prautoblogger_models',
+				'default' => 'medium',
+				'options' => [
+					'xhigh'   => __( 'Extra High — maximum depth, highest cost', 'prautoblogger' ),
+					'high'    => __( 'High — thorough reasoning', 'prautoblogger' ),
+					'medium'  => __( 'Medium — balanced (recommended)', 'prautoblogger' ),
+					'low'     => __( 'Low — light reasoning, lower cost', 'prautoblogger' ),
+					'minimal' => __( 'Minimal — barely any reasoning', 'prautoblogger' ),
+				],
+				'description' => __( 'How much effort the model spends reasoning before answering. Higher effort = more reasoning tokens = higher cost. Only applies when reasoning is enabled above.', 'prautoblogger' ),
+			],
+
 			// ── Schedule & Budget ───────────────────────────────────────
 			[
 				'id'      => 'prautoblogger_daily_article_target',

includes/providers/class-open-router-provider.php

@@ -36,7 +36,8 @@ class PRAutoBlogger_OpenRouter_Provider implements PRAutoBlogger_LLM_Provider_In
 	 *     temperature?: float,
 	 *     max_tokens?: int,
 	 *     response_format?: array{type: string},
-	 * } $options Optional parameters.
+	 *     reasoning?: array{enabled: bool, effort?: string},
+	 * } $options Optional parameters. Pass 'reasoning' to override the global setting.
 	 *
 	 * @return array{
 	 *     content: string,
@@ -88,6 +89,16 @@ class PRAutoBlogger_OpenRouter_Provider implements PRAutoBlogger_LLM_Provider_In
 			$body['response_format'] = $options['response_format'];
 		}
 
+		// Reasoning mode: explicit caller override takes priority, then global setting.
+		if ( isset( $options['reasoning'] ) ) {
+			$body['reasoning'] = $options['reasoning'];
+		} elseif ( '1' === get_option( 'prautoblogger_reasoning_enabled', '0' ) ) {
+			$body['reasoning'] = [
+				'enabled' => true,
+				'effort'  => get_option( 'prautoblogger_reasoning_effort', 'medium' ),
+			];
+		}
+
 		$last_error = '';
 
 		$config      = new PRAutoBlogger_OpenRouter_Config();

includes/providers/class-open-router-response-parser.php

@@ -43,8 +43,10 @@ class PRAutoBlogger_OpenRouter_Response_Parser {
 	 *     model: string,
 	 *     prompt_tokens: int,
 	 *     completion_tokens: int,
+	 *     reasoning_tokens: int,
 	 *     total_tokens: int,
 	 *     finish_reason: string,
+	 *     reasoning_content: string,
 	 * }
 	 *
 	 * @throws \RuntimeException If response structure is invalid.
@@ -94,13 +96,18 @@ class PRAutoBlogger_OpenRouter_Response_Parser {
 
 		$usage = $data['usage'] ?? [];
 
+		// Reasoning content lives alongside 'content' in the message object.
+		$reasoning_content = $data['choices'][0]['message']['reasoning'] ?? '';
+
 		return [
 			'content'           => (string) $content,
 			'model'             => $data['model'] ?? $model,
 			'prompt_tokens'     => (int) ( $usage['prompt_tokens'] ?? 0 ),
 			'completion_tokens' => (int) ( $usage['completion_tokens'] ?? 0 ),
+			'reasoning_tokens'  => (int) ( $usage['reasoning_tokens'] ?? 0 ),
 			'total_tokens'      => (int) ( $usage['total_tokens'] ?? 0 ),
 			'finish_reason'     => $data['choices'][0]['finish_reason'] ?? 'unknown',
+			'reasoning_content' => (string) $reasoning_content,
 		];
 	}