[Agent][Platform][OpenAI] Add support to include usage on streams

[oesteve]

Hi !



OpenAI GPT added a functionality to receive the usage token using stream https://platform.openai.com/docs/api-reference/chat/create#chat-create-stream_options-include_usage.

The current implementation just ignore these messages as is not part of the delta content.

ai/src/platform/src/Bridge/OpenAi/Gpt/ResultConverter.php

Line 110 in 2c4d20d

continue;

I’ve been working on an implementation to parse and return the usage object through the generator, but I’m not really sure if this is the best approach. Alternatively, I could consider using an event listener or adding a usage property in the StreamResult that would be accessible after the stream has been consumed.

So far, this is how the PR looks in action:

    $options = [
        'stream' => true,
        'stream_options' => [
            'include_usage' => true,
        ],
    ];

    $stream = $agent->call($messages, $options)->getContent();

    if (!is_iterable($stream)) {
        throw new \RuntimeException('Invalid result type, expected iterable');
    }

    foreach ($stream as $chunk) {
        if (is_string($chunk)) {
            $context->setDelta($chunk);
            continue;
        }

        if ($chunk instanceof TokenUsage) {
            $context->addUsedTokens(
                $chunk->totalTokens ?: 0,
                $chunk->cachedTokens ?: 0
            );
        }
    }

I'll be so glad to know your opinion about these approaches or any other alternatives.

Thanks !