Extension crash PHP (assert in Zend) during Llm::complete()

[KlimTodrik]

llm PHP extension crashes PHP (assert in Zend) during Llm::complete() — “Exceptions must implement Throwable” / follow-up LLMException at shutdown

Environment:

• Product: Manticore Buddy (Swoole runtime), plugin uses llm PHP extension
• PHP 8.4.17 (cli) (built: Feb 6 2026 01:17:54) (NTS DEBUG)
• OS/container: (test-kit)
• LLM provider/model: openai:gpt-3.5-turbo (model id string: openai:gpt-3.5-turbo)

Summary:

Calling Llm::complete() can crash the PHP process (exit code 134) with an assertion in Zend/zend_exceptions.c:
Assertion 'instanceof_function(exception_ce, zend_ce_throwable) && "Exceptions must implement Throwable"' failed.
In the real app (Swoole worker), this manifests as Fatal error: Uncaught exception LLMException in Unknown on line 0 during shutdown / request end.

Impact:

• Hard crash of PHP process / Swoole worker
• Not catchable from userland try/catch (Throwable $e)
• Leaves application in inconsistent state (task result not set, request handler returns wrong error)

Reproduction (Minimal):

Run inside a PHP environment where the llm extension is available.

<?php declare(strict_types=1);

  function padToLength(string $text, int $targetLength): string {
      $len = strlen($text);
      if ($len >= $targetLength) return $text;
      $padLen = $targetLength - $len;
      return $text . "\n\nPAD:" . str_repeat('x', max(0, $padLen - 6));
  }

  function doComplete(\Llm $llm, string $label, string $prompt, float $temperature, int $maxTokens): void {
      echo "== {$label}\n";
      echo "prompt_length=" . strlen($prompt) . "\n";
      $llm->setTemperature($temperature);
      $llm->setMaxTokens($maxTokens);
      $messages = [\Message::user($prompt)];

      echo "complete() start\n";
      try {
          $response = $llm->complete($messages);
          echo "complete() ok\n";
          echo "finish_reason=" . $response->getFinishReason() . "\n";
          $usage = $response->getUsage();
          echo "tokens_total=" . $usage->getTotalTokens() . " prompt=" . $usage->getPromptTokens() . " output=" . $usage->getOutputTokens() . "\n";
      } catch (\Throwable $e) {
          echo "complete() caught: " . $e::class . ": " . $e->getMessage() . "\n";
      }
      echo "complete() end\n";
  }

  $modelId = 'openai:gpt-3.5-turbo';
  $llm = new \Llm($modelId);

  // Prompts sized to match production logs (might matter)
  $intentPrompt = padToLength("intent prompt\n", 1736);
  $queryGenPrompt = padToLength("query generation prompt\n", 2661);
  $expansionPrompt = padToLength("expansion intent prompt\n", 1455);

  doComplete($llm, 'intent_classification', $intentPrompt, 0.1, 50);
  doComplete($llm, 'query_generation', $queryGenPrompt, 0.3, 200);

  // This call crashes PHP with Zend assertion:
  doComplete($llm, 'expansion_intent', $expansionPrompt, 0.1, 10);

  echo "done\n";

Observed result:

• First two calls: complete() ok
• Third call: PHP process aborts (exit code 134) with:

  php: .../Zend/zend_exceptions.c:857: zend_throw_exception_zstr: Assertion `instanceof_function(exception_ce, zend_ce_throwable) && "Exceptions must implement Throwable"' failed.

Notes / extra context:

• In a Swoole worker (single-process, long-lived), this causes worker crashes at request shutdown with:
  Fatal error: Uncaught exception LLMException in Unknown on line 0
• The crash happens after complete() start and before any userland catch/finally can run, suggesting the extension raises an invalid exception or corrupts exception state internally.
• Reproduces both when running only the “expansion intent” call and when doing 2 successful completes first and crashing on the 3rd.

Script output

== intent_classification
prompt_length=1736
complete() start
complete() ok
finish_reason=stop
tokens_total=227 prompt=227 output=0
complete() end
== query_generation
prompt_length=2661
complete() start
complete() ok
finish_reason=stop
tokens_total=343 prompt=343 output=0
complete() end
== expansion_intent
prompt_length=1455
complete() start
php: /home/runner/work/executor/executor/build/Zend/zend_exceptions.c:857: zend_throw_exception_zstr: Assertion `instanceof_function(exception_ce, zend_ce_throwable) && "Exceptions must implement Throwable"' failed.
Aborted

[donhardman]

Please can you try to replace the locally executor and run the test in a real case scenario to make sure it's all good?

Choose the artifact from here: https://github.com/manticoresoftware/executor/actions/runs/22478609475?pr=80

[KlimTodrik]

Yes, that works

I merged your PR and kicked off the release creation, but the job failed: https://github.com/manticoresoftware/executor/actions/runs/22588376899