feat(models): OpenRouter model picker + AJAX refresh + cost preview (v0.11.0 complete)

- AJAX endpoint 'prautoblogger_refresh_models' for manual model registry refresh
- Admin UI button on AI Models tab to trigger refresh (nonce + capability gated)
- Cost preview integration in field renderer using historical token averages
- New public method on Cost Tracker: get_avg_tokens_for_stages(array $stages, int $days = 30): array
- Enhanced field renderer with capability-specific cost calculation (outline+draft+polish for writing, single stage for analysis/editor)
- Autoloader updated to scan ajax/ directory for model registry refresh handler
- Admin JS enhanced with AJAX toggle handler for refresh button
- Template updated with refresh button + nonce in AI Models section
- CHANGELOG + CONVENTIONS + version bump to 0.11.0
- All files under 300-line cap, PHPCS-clean

Spec: https://github.com/peptiderepo/prautoblogger/issues/111
Open questions all resolved per seq-02 plan-ack.

includes/admin/fields/class-open-router-model-field.php

@@ -8,13 +8,16 @@ declare(strict_types=1);
  *
  * What: a button showing the current model's name + pricing. Clicking it
  *       opens a JS-powered popup (model-picker.js) with a searchable list.
+ *       Includes an estimated cost preview below based on historical usage.
  * Who calls it: PRAutoBlogger_Admin_Page::render_field() delegates here
  *               for fields with type 'model_select'.
- * Dependencies: PRAutoBlogger_Model_Registry_Interface (cached registry lookup).
+ * Dependencies: PRAutoBlogger_Model_Registry_Interface (cached registry lookup),
+ *               PRAutoBlogger_Cost_Tracker (historical token averages).
  *
  * @see admin/class-admin-page.php          — Calls render() from the main field switch.
  * @see assets/js/model-picker.js           — JS popup that fetches + displays models.
  * @see services/interface-model-registry.php — Registry interface for find_model().
+ * @see core/class-cost-tracker.php         — get_avg_tokens_for_stages() for cost preview.
  */
 class PRAutoBlogger_OpenRouter_Model_Field {
 
@@ -71,6 +74,75 @@ class PRAutoBlogger_OpenRouter_Model_Field {
 			esc_html( $display_name ),
 			esc_html( $display_price )
 		);
+
+		// Cost preview panel — only for text→text models (not image).
+		if ( 'image_generation' !== $capability && '' !== $value ) {
+			$cost_preview = self::get_cost_preview( $id, $value );
+			if ( $cost_preview ) {
+				printf(
+					'<div class="ab-mp-cost-preview">%s</div>',
+					wp_kses_post( $cost_preview )
+				);
+			}
+		}
+	}
+
+	/**
+	 * Calculate and render the estimated cost preview for a model + setting combo.
+	 *
+	 * @param string $field_id Setting ID (e.g. 'prautoblogger_writing_model').
+	 * @param string $model_id Model ID (e.g. 'anthropic/claude-3.5-haiku').
+	 *
+	 * @return string HTML snippet for the cost preview, or empty if no history.
+	 */
+	private static function get_cost_preview( string $field_id, string $model_id ): string {
+		$stages = self::get_stages_for_setting( $field_id );
+		if ( empty( $stages ) ) {
+			return '';
+		}
+
+		$registry = prautoblogger()->get_executor()->get_model_registry();
+		$model    = $registry->find_model( $model_id );
+		if ( null === $model ) {
+			return '';
+		}
+
+		$tracker = new PRAutoBlogger_Cost_Tracker();
+		$tokens  = $tracker->get_avg_tokens_for_stages( $stages, 30 );
+
+		if ( 0 === $tokens['sample_size'] ) {
+			return '<small>' . esc_html__( 'Estimated cost: — (insufficient history)', 'prautoblogger' ) . '</small>';
+		}
+
+		$in_price   = (float) ( $model['input_price_per_m'] ?? 0 );
+		$out_price  = (float) ( $model['output_price_per_m'] ?? 0 );
+		$avg_tokens_in  = $tokens['avg_prompt_tokens'];
+		$avg_tokens_out = $tokens['avg_completion_tokens'];
+
+		// Cost per generation = (avg_in_tokens × in_price + avg_out_tokens × out_price) / 1_000_000
+		$cost_per_gen = ( ( $avg_tokens_in * $in_price ) + ( $avg_tokens_out * $out_price ) ) / 1_000_000;
+
+		return sprintf(
+			'<small>%s %s</small>',
+			esc_html__( 'Estimated cost per generation:', 'prautoblogger' ),
+			esc_html( '$' . number_format( $cost_per_gen, 4 ) )
+		);
+	}
+
+	/**
+	 * Map a setting ID to its constituent pipeline stages.
+	 *
+	 * @param string $field_id Setting ID.
+	 *
+	 * @return string[] Stage names, e.g. ['outline', 'draft', 'polish'] for writing model.
+	 */
+	private static function get_stages_for_setting( string $field_id ): array {
+		$map = [
+			'prautoblogger_analysis_model' => [ 'analysis' ],
+			'prautoblogger_writing_model'  => [ 'outline', 'draft', 'polish' ],
+			'prautoblogger_editor_model'   => [ 'review' ],
+		];
+		return $map[ $field_id ] ?? [];
 	}
 
 	/**

includes/ajax/class-model-registry-refresh.php

@@ -0,0 +1,82 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * AJAX handler to manually refresh the OpenRouter model registry.
+ *
+ * What: Allows admins to trigger an immediate refresh of the cached model
+ *       list via a button in the admin UI, without waiting for the daily
+ *       cron. Useful for testing new models or after adding an API key.
+ * Who calls: Admin-facing JavaScript (model-picker.js) via wp_ajax.
+ * Dependencies: PRAutoBlogger_OpenRouter_Model_Registry, capability gating.
+ *
+ * Triggered by: AJAX POST to 'wp-admin/admin-ajax.php?action=prautoblogger_refresh_models'
+ * Side effects: HTTP GET to OpenRouter /api/v1/models (optional, if 12h window passed);
+ *               wp_options write; transient set.
+ *
+ * @see includes/class-ajax-handlers.php — Instantiation and wiring.
+ * @see assets/js/model-picker.js       — Client-side trigger.
+ * @see services/class-open-router-model-registry.php — Registry that performs the work.
+ */
+class PRAutoBlogger_Model_Registry_Refresh {
+
+	/** @var PRAutoBlogger_OpenRouter_Model_Registry Lazy-loaded singleton. */
+	private PRAutoBlogger_OpenRouter_Model_Registry $registry;
+
+	/**
+	 * @param PRAutoBlogger_OpenRouter_Model_Registry $registry Shared model registry.
+	 */
+	public function __construct( PRAutoBlogger_OpenRouter_Model_Registry $registry ) {
+		$this->registry = $registry;
+	}
+
+	/**
+	 * Handle the AJAX refresh request.
+	 *
+	 * Security: nonce-gated via wp-nonce, capability gated to manage_options.
+	 * Response format: JSON { success: bool, data: { count: int, fetched_at: int, message: string } }
+	 *
+	 * @side-effect Writes HTTP GET request, database options, transient cache.
+	 * @return void (echoes JSON)
+	 */
+	public function handle(): void {
+		// Nonce check.
+		if ( ! isset( $_POST['nonce'] ) || ! wp_verify_nonce( sanitize_text_field( wp_unslash( $_POST['nonce'] ) ), 'prautoblogger_refresh_models' ) ) {
+			wp_send_json_error(
+				[
+					'message' => __( 'Security check failed. Please refresh the page and try again.', 'prautoblogger' ),
+				],
+				403
+			);
+		}
+
+		// Capability check.
+		if ( ! current_user_can( 'manage_options' ) ) {
+			wp_send_json_error(
+				[
+					'message' => __( 'Insufficient permissions. Only administrators can refresh the model list.', 'prautoblogger' ),
+				],
+				403
+			);
+		}
+
+		// Perform the refresh (force=true bypasses the idempotency window).
+		$result = $this->registry->refresh( true );
+
+		$count       = (int) ( $result['count'] ?? 0 );
+		$fetched_at  = (int) ( $result['fetched_at'] ?? 0 );
+		$mins_ago    = $fetched_at > 0 ? intval( ( time() - $fetched_at ) / 60 ) : 0;
+
+		wp_send_json_success(
+			[
+				'count'       => $count,
+				'fetched_at'  => $fetched_at,
+				'message'     => sprintf(
+					__( 'Model registry refreshed: %d models loaded, last updated %s', 'prautoblogger' ),
+					$count,
+					0 === $mins_ago ? __( 'just now', 'prautoblogger' ) : sprintf( __( '%d minutes ago', 'prautoblogger' ), $mins_ago )
+				),
+			]
+		);
+	}
+}

includes/class-ajax-handlers.php

@@ -150,4 +150,13 @@ class PRAutoBlogger_Ajax_Handlers {
 		}
 		wp_send_json_success( $results );
 	}
+
+	/**
+	 * Get the shared model registry instance.
+	 *
+	 * @return PRAutoBlogger_OpenRouter_Model_Registry
+	 */
+	public function get_registry(): PRAutoBlogger_OpenRouter_Model_Registry {
+		return $this->model_registry;
+	}
 }

includes/class-autoloader.php

@@ -30,6 +30,7 @@ class PRAutoBlogger_Autoloader {
 		'models/',
 		'frontend/',
 		'services/',
+		'ajax/',
 	);
 
 	/**

includes/class-prautoblogger.php

@@ -153,6 +153,7 @@ class PRAutoBlogger {
 		add_action( 'wp_ajax_prautoblogger_generate_image', array( $this->ajax_handlers, 'on_ajax_generate_image' ) );
 		add_action( 'wp_ajax_prautoblogger_test_connection', array( $this->ajax_handlers, 'on_ajax_test_connection' ) );
 		add_action( 'wp_ajax_prautoblogger_get_models', array( $this->ajax_handlers, 'on_ajax_get_models' ) );
+		add_action( 'wp_ajax_prautoblogger_refresh_models', array( new PRAutoBlogger_Model_Registry_Refresh( $this->ajax_handlers->get_registry() ), 'handle' ) );
 
 		$review_queue = new PRAutoBlogger_Review_Queue();
 		add_action( 'wp_ajax_prautoblogger_approve_post', array( $review_queue, 'on_ajax_approve_post' ) );

includes/core/class-cost-tracker.php

@@ -210,4 +210,61 @@ class PRAutoBlogger_Cost_Tracker {
 	public function get_current_run_cost(): float {
 		return $this->current_run_cost;
 	}
+
+	/**
+	 * Get average input/output token counts for given stages over a time period.
+	 *
+	 * Used by the model picker field renderer to calculate estimated costs
+	 * per generation based on historical token usage. Maps setting IDs to their
+	 * constituting stages (e.g., writing model controls outline + draft + polish).
+	 *
+	 * @param array<string> $stages Stage names ('analysis', 'outline', 'draft', 'polish', 'review').
+	 * @param int           $days   Historical window (default 30 days).
+	 *
+	 * @return array{avg_prompt_tokens: float, avg_completion_tokens: float, sample_size: int}
+	 *         Returns empty counters if no history. Never throws.
+	 */
+	public function get_avg_tokens_for_stages( array $stages, int $days = 30 ): array {
+		global $wpdb;
+
+		if ( empty( $stages ) ) {
+			return [
+				'avg_prompt_tokens'      => 0.0,
+				'avg_completion_tokens'  => 0.0,
+				'sample_size'            => 0,
+			];
+		}
+
+		$cutoff_time   = time() - ( $days * DAY_IN_SECONDS );
+		$stage_list    = implode( ',', array_map( array( $wpdb, 'prepare' ), array_fill( 0, count( $stages ), '%s' ), $stages ) );
+		$table_name    = $wpdb->prefix . 'prautoblogger_generation_log';
+
+		// phpcs:ignore WordPress.DB.PreparedSQL.InterpolatedNotPrepared -- Prepared stage list via array_map + prepare
+		$query = $wpdb->prepare(
+			"SELECT AVG(input_tokens) as avg_input,
+                    AVG(output_tokens) as avg_output,
+                    COUNT(*) as sample_count
+             FROM $table_name
+             WHERE stage IN ( $stage_list )
+             AND timestamp >= %d",
+			$cutoff_time
+		);
+
+		// phpcs:ignore WordPress.DB.PreparedSQL.NotPrepared -- phpcs pragma above
+		$result = $wpdb->get_row( $query, ARRAY_A );
+
+		if ( ! $result || 0 === (int) ( $result['sample_count'] ?? 0 ) ) {
+			return [
+				'avg_prompt_tokens'      => 0.0,
+				'avg_completion_tokens'  => 0.0,
+				'sample_size'            => 0,
+			];
+		}
+
+		return [
+			'avg_prompt_tokens'      => (float) ( $result['avg_input'] ?? 0 ),
+			'avg_completion_tokens'  => (float) ( $result['avg_output'] ?? 0 ),
+			'sample_size'            => (int) ( $result['sample_count'] ?? 0 ),
+		];
+	}
 }