first commit

src/Agent/ThinkSuppressor.php

@@ -0,0 +1,88 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Agent;
+
+/**
+ * ThinkSuppressor
+ *
+ * Robust streaming-safe suppressor for internal <think>...</think> sections.
+ *
+ * Key properties:
+ * - Handles token fragmentation (partial tags across tokens)
+ * - Stateful per stream, stateless per request
+ * - Does not buffer full responses
+ * - Deterministic and predictable
+ */
+final class ThinkSuppressor
+{
+    /** Indicates whether the stream is currently inside a <think> block. */
+    private bool $insideThink = false;
+
+    /** Indicates whether the think section has been fully closed. */
+    private bool $thinkSectionCompleted = false;
+
+    /**
+     * Rolling buffer for detecting fragmented tags across tokens.
+     */
+    private string $rollingBuffer = '';
+
+    /**
+     * Maximum buffer length needed to safely detect tags.
+     */
+    private int $maxBufferLength = 32;
+
+    /**
+     * Filters a single token from the LLM stream.
+     *
+     * @param string $token Raw token from the LLM
+     * @return string Cleaned token safe for user output
+     */
+    public function filter(string $token): string
+    {
+        // Append to rolling buffer
+        $this->rollingBuffer .= $token;
+        if (strlen($this->rollingBuffer) > $this->maxBufferLength) {
+            $this->rollingBuffer = substr($this->rollingBuffer, -$this->maxBufferLength);
+        }
+
+        // If think section is already completed, just strip stray closing tags
+        if ($this->thinkSectionCompleted) {
+            return str_replace('</think>', '', $token);
+        }
+
+        // Detect fragmented opening <think> tag
+        if (!$this->insideThink && str_contains($this->rollingBuffer, '<think>')) {
+            $this->insideThink = true;
+            return '';
+        }
+
+        // Detect fragmented closing </think> tag
+        if ($this->insideThink && str_contains($this->rollingBuffer, '</think>')) {
+            $this->insideThink = false;
+            $this->thinkSectionCompleted = true;
+
+            // Emit a single line break after think section ends
+            return "\n";
+        }
+
+        // Suppress all content while inside <think>...</think>
+        if ($this->insideThink) {
+            return '';
+        }
+
+        return $token;
+    }
+
+    /**
+     * Resets the suppressor state.
+     * Must be called before starting a new stream.
+     */
+    public function reset(): void
+    {
+        $this->insideThink = false;
+        $this->thinkSectionCompleted = false;
+        $this->rollingBuffer = '';
+    }
+}