MDL-88314 core_ai: Strip think tags from AI-generated text

Author: muhammadarnaldo

public/ai/classes/aiactions/responses/response_explain_text.php

@@ -16,6 +16,8 @@
 
 namespace core_ai\aiactions\responses;
 
+use core_ai\helper;
+
 /**
  * Explain text action response class.
  *
@@ -71,7 +73,10 @@ public function __construct(
     public function set_response_data(array $response): void {
         $this->id = $response['id'] ?? null;
         $this->fingerprint = $response['fingerprint'] ?? null;
-        $this->generatedcontent = $response['generatedcontent'] ?? null;
+        $generatedcontent = $response['generatedcontent'] ?? null;
+        $this->generatedcontent = $generatedcontent !== null
+            ? helper::strip_reasoning_tags($generatedcontent)
+            : null;
         $this->finishreason = $response['finishreason'] ?? null;
         $this->prompttokens = $response['prompttokens'] ?? null;
         $this->completiontokens = $response['completiontokens'] ?? null;

public/ai/classes/aiactions/responses/response_generate_text.php

@@ -16,6 +16,8 @@
 
 namespace core_ai\aiactions\responses;
 
+use core_ai\helper;
+
 /**
  * Generate text action response class.
  *
@@ -71,7 +73,10 @@ public function __construct(
     public function set_response_data(array $response): void {
         $this->id = $response['id'] ?? null;
         $this->fingerprint = $response['fingerprint'] ?? null;
-        $this->generatedcontent = $response['generatedcontent'] ?? null;
+        $generatedcontent = $response['generatedcontent'] ?? null;
+        $this->generatedcontent = $generatedcontent !== null
+            ? helper::strip_reasoning_tags($generatedcontent)
+            : null;
         $this->finishreason = $response['finishreason'] ?? null;
         $this->prompttokens = $response['prompttokens'] ?? null;
         $this->completiontokens = $response['completiontokens'] ?? null;

public/ai/classes/aiactions/responses/response_summarise_text.php

@@ -16,6 +16,8 @@
 
 namespace core_ai\aiactions\responses;
 
+use core_ai\helper;
+
 /**
  * Summarise text action response class.
  *
@@ -71,7 +73,10 @@ public function __construct(
     public function set_response_data(array $response): void {
         $this->id = $response['id'] ?? null;
         $this->fingerprint = $response['fingerprint'] ?? null;
-        $this->generatedcontent = $response['generatedcontent'] ?? null;
+        $generatedcontent = $response['generatedcontent'] ?? null;
+        $this->generatedcontent = $generatedcontent !== null
+            ? helper::strip_reasoning_tags($generatedcontent)
+            : null;
         $this->finishreason = $response['finishreason'] ?? null;
         $this->prompttokens = $response['prompttokens'] ?? null;
         $this->completiontokens = $response['completiontokens'] ?? null;

public/ai/classes/helper.php

@@ -0,0 +1,53 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+namespace core_ai;
+
+/**
+ * AI helper class.
+ *
+ * @package    core_ai
+ * @copyright  2026 Muhammad Arnaldo <muhammad.arnaldo@moodle.com>
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+class helper {
+    /**
+     * Reasoning tag names to strip from AI-generated text.
+     *
+     * Add new tag names here when additional AI models are found to include
+     * reasoning content in their responses.
+     *
+     * @var string[]
+     */
+    public const REASONING_TAGS = [
+        'think',
+    ];
+
+    /**
+     * Strip reasoning tags from AI-generated content.
+     *
+     * Some AI models include reasoning or chain-of-thought content wrapped in
+     * XML-like tags (e.g. <think>...</think>). This method removes those tags
+     * and their content so only the final response is returned to the user.
+     *
+     * @param string $content The AI-generated content.
+     * @return string The content with reasoning tags removed.
+     */
+    public static function strip_reasoning_tags(string $content): string {
+        $pattern = implode('|', array_map('preg_quote', self::REASONING_TAGS));
+        return trim(preg_replace('/<(' . $pattern . ')>.*?<\/\1>\s*/is', '', $content) ?? $content);
+    }
+}

public/ai/placement/editor/classes/external/generate_text.php

@@ -128,7 +128,7 @@ public static function execute_returns(): external_function_parameters {
                 VALUE_REQUIRED,
             ),
             'generatedcontent' => new external_value(
-                PARAM_TEXT,
+                PARAM_RAW,
                 'The text generated by AI.',
                 VALUE_DEFAULT,
             ),

public/ai/tests/aiactions/responses/response_explain_text_test.php

@@ -75,4 +75,17 @@ public function test_set_response_data(): void {
         $this->assertEquals($body['prompttokens'], $actionresponse->get_response_data()['prompttokens']);
         $this->assertEquals($body['completiontokens'], $actionresponse->get_response_data()['completiontokens']);
     }
+
+    /**
+     * Test that reasoning tags are stripped from generated content.
+     */
+    public function test_set_response_data_strips_reasoning_tags(): void {
+        $actionresponse = new response_explain_text(success: true);
+        $actionresponse->set_response_data([
+            'generatedcontent' => '<think>Internal reasoning.</think>The actual response.',
+            'finishreason' => 'stop',
+        ]);
+
+        $this->assertEquals('The actual response.', $actionresponse->get_response_data()['generatedcontent']);
+    }
 }

public/ai/tests/aiactions/responses/response_generate_text_test.php

@@ -75,4 +75,17 @@ public function test_set_response_data(): void {
         $this->assertEquals($body['prompttokens'], $actionresponse->get_response_data()['prompttokens']);
         $this->assertEquals($body['completiontokens'], $actionresponse->get_response_data()['completiontokens']);
     }
+
+    /**
+     * Test that reasoning tags are stripped from generated content.
+     */
+    public function test_set_response_data_strips_reasoning_tags(): void {
+        $actionresponse = new response_generate_text(success: true);
+        $actionresponse->set_response_data([
+            'generatedcontent' => '<think>Internal reasoning.</think>The actual response.',
+            'finishreason' => 'stop',
+        ]);
+
+        $this->assertEquals('The actual response.', $actionresponse->get_response_data()['generatedcontent']);
+    }
 }

public/ai/tests/aiactions/responses/response_summarise_text_test.php

@@ -75,4 +75,17 @@ public function test_set_response_data(): void {
         $this->assertEquals($body['prompttokens'], $actionresponse->get_response_data()['prompttokens']);
         $this->assertEquals($body['completiontokens'], $actionresponse->get_response_data()['completiontokens']);
     }
+
+    /**
+     * Test that reasoning tags are stripped from generated content.
+     */
+    public function test_set_response_data_strips_reasoning_tags(): void {
+        $actionresponse = new response_summarise_text(success: true);
+        $actionresponse->set_response_data([
+            'generatedcontent' => '<think>Internal reasoning.</think>The actual response.',
+            'finishreason' => 'stop',
+        ]);
+
+        $this->assertEquals('The actual response.', $actionresponse->get_response_data()['generatedcontent']);
+    }
 }